Biomimetic polymeric superhydrophobic surfaces and nanostructures: from fabrication to applications.

PubMed

Wen, Gang; Guo, ZhiGuang; Liu, Weimin

2017-03-09

Numerous research studies have contributed to the development of mature superhydrophobic systems. The fabrication and applications of polymeric superhydrophobic surfaces have been discussed and these have attracted tremendous attention over the past few years due to their excellent properties. In general, roughness and chemical composition, the two most crucial factors with respect to surface wetting, provide the basic criteria for yielding polymeric superhydrophobic materials. Furthermore, with their unique properties and flexible configurations, polymers have been one of the most efficient materials for fabricating superhydrophobic materials. This review aims to summarize the most recent progress in polymeric superhydrophobic surfaces. Significantly, the fundamental theories for designing these materials will be presented, and the original methods will be introduced, followed by a summary of multifunctional superhydrophobic polymers and their applications. The principles of these methods can be divided into two categories: the first involves adding nanoparticles to a low surface energy polymer, and the other involves combining a low surface energy material with a textured surface, followed by chemical modification. Notably, surface-initiated radical polymerization is a versatile method for a variety of vinyl monomers, resulting in controlled molecular weights and low polydispersities. The surfaces produced by these methods not only possess superhydrophobicity but also have many applications, such as self-cleaning, self-healing, anti-icing, anti-bioadhesion, oil-water separation, and even superamphiphobic surfaces. Interestingly, the combination of responsive materials and roughness enhances the responsiveness, which allows the achievement of intelligent transformation between superhydrophobicity and superhydrophilicity. Nevertheless, surfaces with poor physical and chemical properties are generally unable to withstand the severe conditions of the outside world; thus, it is necessary to optimize the performances of such materials to yield durable superhydrophobic surfaces. To sum up, some challenges and perspectives regarding the future research and development of polymeric superhydrophobic surfaces are presented.

Engineering tunable bio-inspired polymeric coatings for amphiphobic fibrous materials

NASA Astrophysics Data System (ADS)

Oyola-Reynoso, Stephanie

Chemical grafting has been widely used to modify the surface properties of materials, especially surface energy for controlled wetting, because of the resilience of such coatings/modifications. Reagents with multiple reactive sites have been used with the expectation that a monolayer will form. The step-growth polymerization mechanism, however, suggests the possibility of gel formation for hydrolysable moieties in the presence of physisorbed water. In the following chapters, we demonstrate that using alkyltrichlorosilanes (trivalent [3 reactive sites]) in the surface modification of a cellulosic material (paper) does not yield a monolayer but rather gives surface-bound polymeric particles. We infer that the presence of physisorbed (surface-bound) water allows for polymerization (or oligomerization) of the silane, prior to its attachment on the surface. Surface energy mismatch between the hydrophobic tails of the growing polymer and any unreacted bound water leads to the assembly of the polymerizing material into spherical particles to minimize surface tension. By varying paper grammage (16.2-201.4 g/m2), we varied the accessible surface area and thus the amount of surface-adsorbed water, allowing us to control the ratio of the silane to the bound water. Using this approach, polymeric particles were formed on the surface of cellulose fibers ranging from 70 nm to a film. The hydrophobicity of the surface, as determined by water contact angles, correlates with particle sizes (p < 0.001, Student t-test), and, hence, the hydrophobicity can be tuned (contact angle between 94° and 149°). Using a model structure of a house, we demonstrated that as a result of this modification, cardboard houses can be rendered self-cleaning or tolerant to surface running water. Each of the chapters below supports the mechanism via a series of applications, material characterization, and/or, smart engineering.

Covalently bonded networks through surface-confined polymerization

NASA Astrophysics Data System (ADS)

El Garah, Mohamed; MacLeod, Jennifer M.; Rosei, Federico

2013-07-01

The prospect of synthesizing ordered, covalently bonded structures directly on a surface has recently attracted considerable attention due to its fundamental interest and for potential applications in electronics and photonics. This prospective article focuses on efforts to synthesize and characterize epitaxial one- and two-dimensional (1D and 2D, respectively) polymeric networks on single crystal surfaces. Recent studies, mostly performed using scanning tunneling microscopy (STM), demonstrate the ability to induce polymerization based on Ullmann coupling, thermal dehalogenation and dehydration reactions. The 2D polymer networks synthesized to date have exhibited structural limitations and have been shown to form only small domains on the surface. We discuss different approaches to control 1D and 2D polymerization, with particular emphasis on the surface phenomena that are critical to the formation of larger ordered domains.

Evaluation of mechanism of cold atmospheric pressure plasma assisted polymerization of acrylic acid on low density polyethylene (LDPE) film surfaces: Influence of various gaseous plasma pretreatment

NASA Astrophysics Data System (ADS)

Ramkumar, M. C.; Pandiyaraj, K. Navaneetha; Arun Kumar, A.; Padmanabhan, P. V. A.; Uday Kumar, S.; Gopinath, P.; Bendavid, A.; Cools, P.; De Geyter, N.; Morent, R.; Deshmukh, R. R.

2018-05-01

Owing to its exceptional physiochemical properties, low density poly ethylene (LDPE) has wide range of tissue engineering applications. Conversely, its inadequate surface properties make LDPE an ineffectual candidate for cell compatible applications. Consequently, plasma-assisted polymerization with a selected precursor is a good choice for enhancing its biocompatibility. The present investigation studies the efficiency of plasma polymerization of acrylic acid (AAC) on various gaseous plasma pretreated LDPE films by cold atmospheric pressure plasma, to enhance its cytocompatibility. The change in chemical composition and surface topography of various gaseous plasma pretreated and acrylic deposited LDPE films has been assessed by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The changes in hydrophilic nature of surface modified LDPE films were studied by contact angle (CA) analysis. Cytocompatibility of the AAC/LDPE films was also studied in vitro, using RIN-5F cells. The results acquired by the XPS and AFM analysis clearly proved that cold atmospheric pressure (CAP) plasma assisted polymerization of AAC enhances various surface properties including carboxylic acid functional group density and increased surface roughness on various gaseous plasma treated AAC/LDPE film surfaces. Moreover, contact angle analysis clearly showed that the plasma polymerized samples were hydrophilic in nature. In vitro cytocompatibility analysis undoubtedly validates that the AAC polymerized various plasma pretreated LDPE films surfaces stimulate cell distribution and proliferation compared to pristine LDPE films. Similarly, cytotoxicity analysis indicates that the AAC deposited various gaseous plasma pretreated LDPE film can be considered as non-toxic as well as stimulating cell viability significantly. The cytocompatible properties of AAC polymerized Ar + O2 plasma pretreated LDPE films were found to be more pronounced compared to the other plasma pretreated AAC/LDPE films.

Polythiophene thin films by surface-initiated polymerization: Mechanistic and structural studies

DOE PAGES

Youm, Sang Gil; Hwang, Euiyong; Chavez, Carlos A.; ...

2016-06-15

The ability to control nanoscale morphology and molecular organization in organic semiconducting polymer thin films is an important prerequisite for enhancing the efficiency of organic thin-film devices including organic light-emitting and photovoltaic devices. The current “top-down” paradigm for making such devices is based on utilizing solution-based processing (e.g., spin-casting) of soluble semiconducting polymers. This approach typically provides only modest control over nanoscale molecular organization and polymer chain alignment. A promising alternative to using solutions of presynthesized semiconducting polymers pursues instead a “bottom-up” approach to prepare surface-grafted semiconducting polymer thin films by surface-initiated polymerization of small-molecule monomers. Herein, we describe themore » development of an efficient method to prepare polythiophene thin films utilizing surface-initiated Kumada catalyst transfer polymerization. In this study, we provided evidence that the surface-initiated polymerization occurs by the highly robust controlled (quasi-“living”) chain-growth mechanism. Further optimization of this method enabled reliable preparation of polythiophene thin films with thickness up to 100 nm. Extensive structural studies of the resulting thin films using X-ray and neutron scattering methods as well as ultraviolet photoemission spectroscopy revealed detailed information on molecular organization and the bulk morphology of the films, and enabled further optimization of the polymerization protocol. One of the remarkable findings was that surface-initiated polymerization delivers polymer thin films showing complex molecular organization, where polythiophene chains assemble into lateral crystalline domains of about 3.2 nm size, with individual polymer chains folded to form in-plane aligned and densely packed oligomeric segments (7-8 thiophene units per each segment) within each domain. Achieving such a complex mesoscale organization is virtually impossible with traditional methods relying on solution processing of presynthesized polymers. Another significant advantage of surface-confined polymer thin films is their remarkable stability toward organic solvents and other processing conditions. In addition to controlled bulk morphology, uniform molecular organization, and stability, a unique feature of the surface-initiated polymerization is that it can be used for the preparation of large-area uniformly nanopatterned polymer thin films. Lastly, this was demonstrated using a combination of particle lithography and surface-initiated polymerization. In general, surface-initiated polymerization is not limited to polythiophene but can be also expanded toward other classes of semiconducting polymers and copolymers.« less

Highly reflective polymeric substrates functionalized utilizing atomic layer deposition

NASA Astrophysics Data System (ADS)

Zuzuarregui, Ana; Coto, Borja; Rodríguez, Jorge; Gregorczyk, Keith E.; Ruiz de Gopegui, Unai; Barriga, Javier; Knez, Mato

2015-08-01

Reflective surfaces are one of the key elements of solar plants to concentrate energy in the receivers of solar thermal electricity plants. Polymeric substrates are being considered as an alternative to the widely used glass mirrors due to their intrinsic and processing advantages, but optimizing both the reflectance and the physical stability of polymeric mirrors still poses technological difficulties. In this work, polymeric surfaces have been functionalized with ceramic thin-films by atomic layer deposition. The characterization and optimization of the parameters involved in the process resulted in surfaces with a reflection index of 97%, turning polymers into a real alternative to glass substrates. The solution we present here can be easily applied in further technological areas where seemingly incompatible combinations of polymeric substrates and ceramic coatings occur.

Preparation of polymeric Janus particles by directional UV-induced reactions.

PubMed

Liu, Lianying; Ren, Mingwei; Yang, Wantai

2009-09-15

Polymeric Janus particles are obtained by UV-induced selective surface grafting polymerizations and coupling reactions, in virtue of the light-absorption of photoreactive materials such as the immobilized photoinitiator and spread photoinitiator solution on the surfaces exposed to UV light and the sheltering of densely arrayed immovable particles from light. Varying the monomers or macromolecules applied in photografting polymerization or coupling reaction, and choosing diverse polymeric particles of various size, bicolor and amphiphilic Janus particles could be successfully achieved. Observations by fluorescence microscope, scanning electron microscope ,and transmission electron microscope confirmed the asymmetrical morphology of the resultant Janus particles.

Evaluation of microhardness, surface roughness, and wear behavior of different types of resin composites polymerized with two different light sources.

PubMed

Topcu, Fulya Toksoy; Erdemir, Ugur; Sahinkesen, Gunes; Yildiz, Esra; Uslan, Ibrahim; Acikel, Cengizhan

2010-02-01

The microhardness, surface roughness and wear resistance of different types of resin composites, polymerized by a Quartz Tungsten Halogen (QTH) or Light Emitting Diode (LED) light curing units (LCU) were evaluated in this in vitro study. Cylindrical blocks were prepared from composites (8 mm in diameter, and 2 mm in thickness) and polymerized by a LED or a QTH LCU. Vickers hardness was measured on the top and bottom surfaces of the specimens. Surface roughness was measured with a surface profilometer on the top of the specimens. For the wear test, specimens were tested in a conventional pin-on-disc tribology machine under 15 N loads. The statistical analyses were performed by one-way analysis of variance (ANOVA) and t-tests, including the Bonferroni correction. Nanocomposite material Clearfil Majesty Posterior showed the highest hardness values in all polymerization types at the top and bottom surfaces (p < 0.05). Microhybrid Clearfil APX and hybrid Quixfil composites demonstrated the greatest surface roughness. Wear resistance of Clearfil Majesty Posterior was found to be the highest among the other tested resin composites. The results indicated that Clearfil Majesty Posterior demonstrated higher microhardness, less surface roughness, and higher wear resistance when compared with the other tested materials for both polymerization types.

On-Surface Domino Reactions: Glaser Coupling and Dehydrogenative Coupling of a Biscarboxylic Acid To Form Polymeric Bisacylperoxides.

PubMed

Held, Philipp Alexander; Gao, Hong-Ying; Liu, Lacheng; Mück-Lichtenfeld, Christian; Timmer, Alexander; Mönig, Harry; Barton, Dennis; Neugebauer, Johannes; Fuchs, Harald; Studer, Armido

2016-08-08

Herein we report the on-surface oxidative homocoupling of 6,6'-(1,4-buta-1,3-diynyl)bis(2-naphthoic acid) (BDNA) via bisacylperoxide formation on different Au substrates. By using this unprecedented dehydrogenative polymerization of a biscarboxylic acid, linear poly-BDNA with a chain length of over 100 nm was prepared. It is shown that the monomer BDNA can be prepared in situ at the surface via on-surface Glaser coupling of 6-ethynyl-2-naphthoic acid (ENA). Under the Glaser coupling conditions, BDNA directly undergoes polymerization to give the polymeric peroxide (poly-BDNA) representing a first example of an on-surface domino reaction. It is shown that the reaction outcome varies as a function of surface topography (Au(111) or Au(100)) and also of the surface coverage, to give branched polymers, linear polymers, or 2D metal-organic networks. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Self-assembly of block copolymers on topographically patterned polymeric substrates

DOEpatents

Russell, Thomas P.; Park, Soojin; Lee, Dong Hyun; Xu, Ting

2016-05-10

Highly-ordered block copolymer films are prepared by a method that includes forming a polymeric replica of a topographically patterned crystalline surface, forming a block copolymer film on the topographically patterned surface of the polymeric replica, and annealing the block copolymer film. The resulting structures can be used in a variety of different applications, including the fabrication of high density data storage media. The ability to use flexible polymers to form the polymeric replica facilitates industrial-scale processes utilizing the highly-ordered block copolymer films.

Amine Enrichment of Thin-Film Composite Membranes via Low Pressure Plasma Polymerization for Antimicrobial Adhesion.

PubMed

Reis, Rackel; Dumée, Ludovic F; He, Li; She, Fenghua; Orbell, John D; Winther-Jensen, Bjorn; Duke, Mikel C

2015-07-15

Thin-film composite membranes, primarily based on poly(amide) (PA) semipermeable materials, are nowadays the dominant technology used in pressure driven water desalination systems. Despite offering superior water permeation and salt selectivity, their surface properties, such as their charge and roughness, cannot be extensively tuned due to the intrinsic fabrication process of the membranes by interfacial polymerization. The alteration of these properties would lead to a better control of the materials surface zeta potential, which is critical to finely tune selectivity and enhance the membrane materials stability when exposed to complex industrial waste streams. Low pressure plasma was employed to introduce amine functionalities onto the PA surface of commercially available thin-film composite (TFC) membranes. Morphological changes after plasma polymerization were analyzed by SEM and AFM, and average surface roughness decreased by 29%. Amine enrichment provided isoelectric point changes from pH 3.7 to 5.2 for 5 to 15 min of plasma polymerization time. Synchrotron FTIR mappings of the amine-modified surface indicated the addition of a discrete 60 nm film to the PA layer. Furthermore, metal affinity was confirmed by the enhanced binding of silver to the modified surface, supported by an increased antimicrobial functionality with demonstrable elimination of E. coli growth. Essential salt rejection was shown minimally compromised for faster polymerization processes. Plasma polymerization is therefore a viable route to producing functional amine enriched thin-film composite PA membrane surfaces.

Olefin metathesis for effective polymer healing via dynamic exchange of strong carbon-carbon bonds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guan, Zhibin; Lu, Yixuan

A method of preparing a malleable and/or self-healing polymeric or composite material is provided. The method includes providing a polymeric or composite material comprising at least one alkene-containing polymer, combining the polymer with at least one homogeneous or heterogeneous transition metal olefin metathesis catalyst to form a polymeric or composite material, and performing an olefin metathesis reaction on the polymer so as to form reversible carbon-carbon double bonds in the polymer. Also provided is a method of healing a fractured surface of a polymeric material. The method includes bringing a fractured surface of a first polymeric material into contact withmore » a second polymeric material, and performing an olefin metathesis reaction in the presence of a transition metal olefin metathesis catalyst such that the first polymeric material forms reversible carbon-carbon double bonds with the second polymeric material. Compositions comprising malleable and/or self-healing polymeric or composite material are also provided.« less

Polymeric hydrogels for novel contact lens-based ophthalmic drug delivery systems: a review.

PubMed

Xinming, Li; Yingde, Cui; Lloyd, Andrew W; Mikhalovsky, Sergey V; Sandeman, Susan R; Howel, Carol A; Liewen, Liao

2008-04-01

Only about 5% of drugs administrated by eye drops are bioavailable, and currently eye drops account for more than 90% of all ophthalmic formulations. The bioavailability of ophthalmic drugs can be improved by a soft contact lens-based ophthalmic drug delivery system. Several polymeric hydrogels have been investigated for soft contact lens-based ophthalmic drug delivery systems: (i) polymeric hydrogels for conventional contact lens to absorb and release ophthalmic drugs; (ii) polymeric hydrogels for piggyback contact lens combining with a drug plate or drug solution; (iii) surface-modified polymeric hydrogels to immobilize drugs on the surface of contact lenses; (iv) polymeric hydrogels for inclusion of drugs in a colloidal structure dispersed in the lens; (v) ion ligand-containing polymeric hydrogels; (vi) molecularly imprinted polymeric hydrogels which provide the contact lens with a high affinity and selectivity for a given drug. Polymeric hydrogels for these contact lens-based ophthalmic drug delivery systems, their advantages and drawbacks are critically analyzed in this review.

PECVD de composes de silicium sur polymeres: Etude de la premiere phase du depot

NASA Astrophysics Data System (ADS)

Dennler, Gilles

Since their first introduction in the early 90's, transparent barriers against oxygen and/or water vapor permeation through polymers, such as SiO 2, are the object of increasing interest in the food and pharmaceutical packaging industries, and more recently for the encapsulation of organic-based displays. It is now well known that these thin layers possess barrier properties only if they are thicker than a certain critical thickness, dc. For example, dc is around 12 nm in the case of SiO2 on KaptonRTM PI; below this value, the measured "Oxygen Transmission Rate" (OTR, in standard cm3/m2/day/bar) is roughly the same as that of the uncoated polymer. Until now, no detailed research has been carried out to explain this observation, but a hypothesis was proposed in the literature, based on island-like growth structure of the coating for d ≤ dc. According to this hypothesis, the surface energy of the polymeric substrates is so low that the Volmer-Weber (island-coalescence) growth mode occurs. We have aimed to verify this explanation, that is, to study the initial phase of silicon-compound (SiO2 and SiN) growth on four different polymeric substrates, namely polyimide (KaptonRTM PI), polycarbonate (LexanRTM PC), polypropylene (PP), and polyethyleneterephthalate (MylarRTM PET). Three different deposition methods were used, namely reactive evaporation of SiO, radio-frequency (RF) Plasma Enhanced Chemical Vapor Deposition (RF PECVD), and Distributed Electron Cyclotron Resonance (DECR) PECVD. In this latter case, the substrates were placed in three different positions: (i) in the active glow zone, (ii) downstream, and (iii) downstream, but shielded from photon emission (e.g. VUV) from the plasma. Angle-Resolved X-Ray Photoelectron Spectroscopy (ARXPS), Rutherford Backscattering Spectroscopy (RBS), and Scanning Electron Microscopy (SEM), the latter performed after Reactive Ion Etching (RIE) by oxygen plasma, revealed that growth indeed occurs in a Volmer-Weber mode in the case of evaporated films. The island coalescence was observed to occur at d = 1.2 nm, at which point the sticking coefficient of precursor species changes drastically. Finally, we have investigated the presence of an "interphase" between deposited coatings and the polymeric substrate. (Abstract shortened by UMI.)

Formation of Polymer Particles by Direct Polymerization on the Surface of a Supramolecular Template.

PubMed

Schmuck, Carsten; Li, Mao; Zellermann, Elio

2018-04-06

Formation of polymeric materials on the surface of supramolecular assemblies is rather challenging due to the often weak non-covalent interactions between the self-assembled template and the monomers before polymerization. We herein describe that the introduction of a supramolecular anion recognition motif, the guanidiniocarbonyl pyrrole cation (GCP), into a short Fmoc-dipeptide 1 leads to self-assembled spherical nanoparticles in aqueous solution. Onto the surface of these nanoparticles negatively charged diacetylene monomers can be attached which after UV polymerization lead to the formation of a polymer shell around the self-assembled template. The hybrid supramolecular and polymeric nanoparticles demonstrated intriguing thermal hysteresis phenomenon. The template nanoparticle could be disassembled through the treatment with organic base which cleaved the Fmoc moiety on 1. This strategy thus showed that a supramolecular anion recognition motif allows the post-assembly formation of polymeric nanomaterials from anionic monomers around a cationic self-assembled template. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Use of the Ex Vivo Chandler Loop Apparatus to Assess the Biocompatibility of Modified Polymeric Blood Conduits

PubMed Central

Slee, Joshua B.; Alferiev, Ivan S.; Levy, Robert J.; Stachelek, Stanley J.

2014-01-01

The foreign body reaction occurs when a synthetic surface is introduced to the body. It is characterized by adsorption of blood proteins and the subsequent attachment and activation of platelets, monocyte/macrophage adhesion, and inflammatory cell signaling events, leading to post-procedural complications. The Chandler Loop Apparatus is an experimental system that allows researchers to study the molecular and cellular interactions that occur when large volumes of blood are perfused over polymeric conduits. To that end, this apparatus has been used as an ex vivo model allowing the assessment of the anti-inflammatory properties of various polymer surface modifications. Our laboratory has shown that blood conduits, covalently modified via photoactivation chemistry with recombinant CD47, can confer biocompatibility to polymeric surfaces. Appending CD47 to polymeric surfaces could be an effective means to promote the efficacy of polymeric blood conduits. Herein is the methodology detailing the photoactivation chemistry used to append recombinant CD47 to clinically relevant polymeric blood conduits and the use of the Chandler Loop as an ex vivo experimental model to examine blood interactions with the CD47 modified and control conduits. PMID:25178087

Engineering live cell surfaces with functional polymers via cytocompatible controlled radical polymerization

NASA Astrophysics Data System (ADS)

Niu, Jia; Lunn, David J.; Pusuluri, Anusha; Yoo, Justin I.; O'Malley, Michelle A.; Mitragotri, Samir; Soh, H. Tom; Hawker, Craig J.

2017-06-01

The capability to graft synthetic polymers onto the surfaces of live cells offers the potential to manipulate and control their phenotype and underlying cellular processes. Conventional grafting-to strategies for conjugating preformed polymers to cell surfaces are limited by low polymer grafting efficiency. Here we report an alternative grafting-from strategy for directly engineering the surfaces of live yeast and mammalian cells through cell surface-initiated controlled radical polymerization. By developing cytocompatible PET-RAFT (photoinduced electron transfer-reversible addition-fragmentation chain-transfer polymerization), synthetic polymers with narrow polydispersity (Mw/Mn < 1.3) could be obtained at room temperature in 5 minutes. This polymerization strategy enables chain growth to be initiated directly from chain-transfer agents anchored on the surface of live cells using either covalent attachment or non-covalent insertion, while maintaining high cell viability. Compared with conventional grafting-to approaches, these methods significantly improve the efficiency of grafting polymer chains and enable the active manipulation of cellular phenotypes.

Improved polymeric surface for adhesion through electron stimulated chemical modification of polymeric surface

DOEpatents

Kelber, J.A.

1987-04-08

Treating polymer surfaces, e.g., Teflon, particularly very thin surfaces, e.g., 50-10,000 A, with low energy electron radiation, e.g., 100-1000 eV, in a high vacuum environment, e.g., less than 10 /sup /minus/6/ Torr, to enhance the ability of the surface to be adhered to a variety of substrates.

Exact solutions to model surface and volume charge distributions

NASA Astrophysics Data System (ADS)

Mukhopadhyay, S.; Majumdar, N.; Bhattacharya, P.; Jash, A.; Bhattacharya, D. S.

2016-10-01

Many important problems in several branches of science and technology deal with charges distributed along a line, over a surface and within a volume. Recently, we have made use of new exact analytic solutions of surface charge distributions to develop the nearly exact Boundary Element Method (neBEM) toolkit. This 3D solver has been successful in removing some of the major drawbacks of the otherwise elegant Green's function approach and has been found to be very accurate throughout the computational domain, including near- and far-field regions. Use of truly distributed singularities (in contrast to nodally concentrated ones) on rectangular and right-triangular elements used for discretizing any three-dimensional geometry has essentially removed many of the numerical and physical singularities associated with the conventional BEM. In this work, we will present this toolkit and the development of several numerical models of space charge based on exact closed-form expressions. In one of the models, Particles on Surface (ParSur), the space charge inside a small elemental volume of any arbitrary shape is represented as being smeared on several surfaces representing the volume. From the studies, it can be concluded that the ParSur model is successful in getting the estimates close to those obtained using the first-principles, especially close to and within the cell. In the paper, we will show initial applications of ParSur and other models in problems related to high energy physics.

Effect of repair resin type and surface treatment on the repair strength of heat-polymerized denture base resin.

PubMed

Alkurt, Murat; Yeşil Duymuş, Zeynep; Gundogdu, Mustafa

2014-01-01

Acrylic resin denture fracture is common in prosthodontic practice. When fractured denture bases are repaired, recurrent fractures frequently occur at the repair surface interface or adjacent areas. The purpose of this study was to evaluate the effect of different surface treatments on the flexural strength of the acrylic resin denture base repaired with heat-polymerized acrylic resin, autopolymerizing resin, and light-polymerized acrylic resin. Ninety-six specimens of heat-polymerized acrylic resin were prepared according to the American Dental Association Specification No. 12 (65.0 × 10.0 × 2.5 mm) and sectioned into halves to create a repair gap (3.0 × 10 × 2.5 mm). The sectioned specimens were divided into 3 groups according to their repair materials. The specimens from each group were divided into 4 subgroups according to their surface treatments: a control group without any surface treatment; an experimental group treated with methyl methacrylate monomer (MMA group); an experimental group treated with airborne-particle abrasion with aluminum oxide particles of 250-μm particle size (abrasion group); and an experimental group treated with erbium:yttrium-aluminum-garnet laser (laser group). After the surface treatments, the 3 materials were placed into the repair gaps and then polymerized. After all of the specimens had been ground and polished, they were stored in distilled water at 37°C for 1 week and subjected to a 3-point bend test. Data were analyzed with a 2-way analysis of variance, and the Tukey honestly significant difference test was performed to identify significant differences (α=.05). The effects of the surface treatments and repair resins on the surface of the denture base resin were examined with scanning electron microscopy. Significant differences were found among the groups in terms of repair resin type (P<.001). All surface-treated specimens had higher flexural strength than controls, except the surface treated with the methyl methacrylate in the heat-polymerized group. A significant difference between the control and abrasion groups (P=.013) was found. The scanning electron microscopy observations showed that the application of surface treatments modified the surface of the denture base resin. The repair procedure with heat-polymerized resin exhibited significantly higher flexural strength than that of the autopolymerized and light-polymerized resins. In addition, the airborne-particle abrasion with aluminum oxide particles of 250-μm particle size improved the flexural strength of the specimens tested. Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Porous polymer networks and ion-exchange media and metal-polymer composites made therefrom

DOEpatents

Kanatzidis, Mercouri G; Katsoulidis, Alexandros

2015-03-10

Porous polymeric networks and composite materials comprising metal nanoparticles distributed in the polymeric networks are provided. Also provided are methods for using the polymeric networks and the composite materials in liquid- and vapor-phase waste remediation applications. The porous polymeric networks, are highly porous, three-dimensional structures characterized by high surface areas. The polymeric networks comprise polymers polymerized from aldehydes and phenolic molecules.

Porous polymer networks and ion-exchange media and metal-polymer composites made therefrom

DOEpatents

Kanatzidis, Mercouri G.; Katsoulidis, Alexandros

2016-10-18

Porous polymeric networks and composite materials comprising metal nanoparticles distributed in the polymeric networks are provided. Also provided are methods for using the polymeric networks and the composite materials in liquid- and vapor-phase waste remediation applications. The porous polymeric networks, are highly porous, three-dimensional structures characterized by high surface areas. The polymeric networks comprise polymers polymerized from aldehydes and phenolic molecules.

Collapse of surface nanobubbles.

PubMed

Chan, Chon U; Chen, Longquan; Arora, Manish; Ohl, Claus-Dieter

2015-03-20

Surface attached nanobubbles populate surfaces submerged in water. These nanobubbles have a much larger contact angle and longer lifetime than predicted by classical theory. Moreover, it is difficult to distinguish them from hydrophobic droplets, e.g., polymeric contamination, using standard atomic force microscopy. Here, we report fast dynamics of a three phase contact line moving over surface nanobubbles, polymeric droplets, and hydrophobic particles. The dynamics is distinct: across polymeric droplets the contact line quickly jumps and hydrophobic particles pin the contact line, while surface nanobubbles rapidly shrink once merging with the contact line, suggesting a method to differentiate nanoscopic gaseous, liquid, and solid structures. Although the collapse process of surface nanobubbles occurs within a few milliseconds, we show that it is dominated by microscopic dynamics rather than bulk hydrodynamics.

Graft Polymerization of Acrylic Acid on a Polytetrafluoroethylene Panel by an Inductively Coupled Plasma

NASA Astrophysics Data System (ADS)

Lan, Yan; You, Qingliang; Cheng, Cheng; Zhang, Suzhen; Ni, Guohua; Nagatsu, M.; Meng, Yuedong

2011-02-01

Surface modification on a polytetrafluoroethylene (PTFE) panel was performed with sequential nitrogen plasma treatments and surface-initiated polymerization. By introducing COO- groups to the surface of the PTFE panel through grafting polymerization of acrylic acid (AA), a transparent poly (acrylic acid) (PAA) membrane was achieved from acrylic acid solution. Grafting polymerization initiating from the active groups was achieved on the PTFE panel surface after the nitrogen plasma treatment. Utilizing the acrylic acid as monomers, with COO- groups as cross link sites to form reticulation structure, a transparent poly (acrylic acid) membrane with arborescent macromolecular structure was formed on the PTFE panel surface. Analysis methods, such as fourier transform infrared spectroscopy (FTIR), microscopy and X-ray photoelectron spectroscopy (XPS), were utilized to characterize the structures of the macromolecule membrane on the PTFE panel surface. A contact angle measurement was performed to characterize the modified PTFE panels. The surface hydrophilicities of modified PTFE panels were significantly enhanced after the plasma treatment. It was shown that the grafting rate is related to the treating time and the power of plasma.

A Review on Surface Stress-Based Miniaturized Piezoresistive SU-8 Polymeric Cantilever Sensors

NASA Astrophysics Data System (ADS)

Mathew, Ribu; Ravi Sankar, A.

2018-06-01

In the last decade, microelectromechanical systems (MEMS) SU-8 polymeric cantilevers with piezoresistive readout combined with the advances in molecular recognition techniques have found versatile applications, especially in the field of chemical and biological sensing. Compared to conventional solid-state semiconductor-based piezoresistive cantilever sensors, SU-8 polymeric cantilevers have advantages in terms of better sensitivity along with reduced material and fabrication cost. In recent times, numerous researchers have investigated their potential as a sensing platform due to high performance-to-cost ratio of SU-8 polymer-based cantilever sensors. In this article, we critically review the design, fabrication, and performance aspects of surface stress-based piezoresistive SU-8 polymeric cantilever sensors. The evolution of surface stress-based piezoresistive cantilever sensors from solid-state semiconductor materials to polymers, especially SU-8 polymer, is discussed in detail. Theoretical principles of surface stress generation and their application in cantilever sensing technology are also devised. Variants of SU-8 polymeric cantilevers with different composition of materials in cantilever stacks are explained. Furthermore, the interdependence of the material selection, geometrical design parameters, and fabrication process of piezoresistive SU-8 polymeric cantilever sensors and their cumulative impact on the sensor response are also explained in detail. In addition to the design-, fabrication-, and performance-related factors, this article also describes various challenges in engineering SU-8 polymeric cantilevers as a universal sensing platform such as temperature and moisture vulnerability. This review article would serve as a guideline for researchers to understand specifics and functionality of surface stress-based piezoresistive SU-8 cantilever sensors.[Figure not available: see fulltext.

Evaluation of Vickers hardness and depth of cure of six composite resins photo-activated with different polymerization modes.

PubMed

Poggio, C; Lombardini, M; Gaviati, S; Chiesa, M

2012-07-01

The current in vitro study evaluated Vickers hardness (VK) and depth of cure (hardness ratio) of six resin composites, polymerized with a light-emitting diode (LED) curing unit by different polymerization modes: Standard 20 s, Standard 40 s, Soft-start 40 s. SIX RESIN COMPOSITES WERE SELECTED FOR THE PRESENT STUDY: three microhybrid (Esthet.X HD, Amaris, Filtek Silorane), two nanohybrid (Grandio, Ceram.X mono) and one nanofilled (Filtek Supreme XT). The VK of the surface was determined with a microhardness tester using a Vickers diamond indenter and a 200 g load applied for 15 seconds. The mean VK and hardness ratio of the specimens were calculated using the formula: hardness ratio = VK of bottom surface / VK of top surface. For all the materials tested and with all the polymerization modes, hardness ratio was higher than the minimum value indicated in literature in order to consider the bottom surface as adequately cured (0.80). Curing time did not affect hardness ratio values for Filtek Silorane, Grandio and Filtek Supreme XT. The effectiveness of cure at the top and bottom surface was not affected by Soft-start polymerization mode.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Youm, Sang Gil; Hwang, Euiyong; Chavez, Carlos A.

The ability to control nanoscale morphology and molecular organization in organic semiconducting polymer thin films is an important prerequisite for enhancing the efficiency of organic thin-film devices including organic light-emitting and photovoltaic devices. The current “top-down” paradigm for making such devices is based on utilizing solution-based processing (e.g., spin-casting) of soluble semiconducting polymers. This approach typically provides only modest control over nanoscale molecular organization and polymer chain alignment. A promising alternative to using solutions of presynthesized semiconducting polymers pursues instead a “bottom-up” approach to prepare surface-grafted semiconducting polymer thin films by surface-initiated polymerization of small-molecule monomers. Herein, we describe themore » development of an efficient method to prepare polythiophene thin films utilizing surface-initiated Kumada catalyst transfer polymerization. In this study, we provided evidence that the surface-initiated polymerization occurs by the highly robust controlled (quasi-“living”) chain-growth mechanism. Further optimization of this method enabled reliable preparation of polythiophene thin films with thickness up to 100 nm. Extensive structural studies of the resulting thin films using X-ray and neutron scattering methods as well as ultraviolet photoemission spectroscopy revealed detailed information on molecular organization and the bulk morphology of the films, and enabled further optimization of the polymerization protocol. One of the remarkable findings was that surface-initiated polymerization delivers polymer thin films showing complex molecular organization, where polythiophene chains assemble into lateral crystalline domains of about 3.2 nm size, with individual polymer chains folded to form in-plane aligned and densely packed oligomeric segments (7-8 thiophene units per each segment) within each domain. Achieving such a complex mesoscale organization is virtually impossible with traditional methods relying on solution processing of presynthesized polymers. Another significant advantage of surface-confined polymer thin films is their remarkable stability toward organic solvents and other processing conditions. In addition to controlled bulk morphology, uniform molecular organization, and stability, a unique feature of the surface-initiated polymerization is that it can be used for the preparation of large-area uniformly nanopatterned polymer thin films. Lastly, this was demonstrated using a combination of particle lithography and surface-initiated polymerization. In general, surface-initiated polymerization is not limited to polythiophene but can be also expanded toward other classes of semiconducting polymers and copolymers.« less

Anchoring submersible ultrasonic receivers in river channels with stable substrate

USGS Publications Warehouse

Bettoli, Phillip William; Scholten, G.D.; Hubbs, D.

2010-01-01

We developed an anchoring system for submersible ultrasonic receivers (SURs) that we placed on the bottom of the riverine reaches of three main-stem reservoirs in the upper Tennessee River. Each anchor consisted of a steel tube (8.9 x 35.6 cm) welded vertically to a round plate of steel (5.1 x 40.6 cm). All seven SURs and their 57-kg anchors were successfully deployed and retrieved three times over 547 d by a dive team employing surface air-breathing equipment and a davit-equipped boat. All of the anchors and their SURs remained stationary over two consecutive winters on the hard-bottom, thalweg sites where they were deployed. The SUR and its anchor at the most downriver site experienced flows that exceeded 2,100 m(3)/s and mean water column velocities of about 0.9 m/s.

Conjugation of diisocyanate side chains to dimethacrylate reduces polymerization shrinkage and increases the hardness of composite resins.

PubMed

Jan, Yih-Dean; Lee, Bor-Shiunn; Lin, Chun-Pin; Tseng, Wan-Yu

2014-04-01

Polymerization shrinkage is one of the main causes of dental restoration failure. This study tried to conjugate two diisocyanate side chains to dimethacrylate resins in order to reduce polymerization shrinkage and increase the hardness of composite resins. Diisocyanate, 2-hydroxyethyl methacrylate, and bisphenol A dimethacrylate were reacted in different ratios to form urethane-modified new resin matrices, and then mixed with 50 wt.% silica fillers. The viscosities of matrices, polymerization shrinkage, surface hardness, and degrees of conversion of experimental composite resins were then evaluated and compared with a non-modified control group. The viscosities of resin matrices increased with increasing diisocyanate side chain density. Polymerization shrinkage and degree of conversion, however, decreased with increasing diisocyanate side chain density. The surface hardness of all diisocyanate-modified groups was equal to or significantly higher than that of the control group. Conjugation of diisocyanate side chains to dimethacrylate represents an effective means of reducing polymerization shrinkage and increasing the surface hardness of dental composite resins. Copyright © 2012. Published by Elsevier B.V.

Facile preparation of fluorescent layered double hydroxide polymeric composites through the photo-induced surface-initiated controlled living polymerization

NASA Astrophysics Data System (ADS)

Chen, Junyu; Liu, Meiying; Huang, Qiang; Jiang, Ruming; Huang, Hongye; Deng, Fengjie; Wen, Yuanqing; Tian, Jianwen; Zhang, Xiaoyong; Wei, Yen

2018-05-01

(Zn/Al) layered double hydroxide (LDH) based fluorescence probes have been facilely fabricated via photo-induced surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization, which demonstrated green fluorescence, good biocompatibility and excellent dispersion performance in aqueous solution. The as prepared (Zn/Al)LDH polymeric composites were modified with 2-methacryloyloxyethyl phosphorylcholine (MPC), acrylic acid (AA) and diacroloyl-fluorescein (Ac-Fl). Among them, the comonomers MPC and AA were used to endow their water dispersibility, biocompatibility and potential drug carriers, while the Ac-Fl was served both as the fluorescence signal and photocatalyst for RAFT polymerization. A series of characterization methods, including 1H nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, transmission electronic microscopy, thermogravimetric analyses, X-ray photoelectron spectroscopy were employed to conform the successful of surface modification of LDH through photo-induced surface-initiated RAFT polymerization. Besides, UV-vis absorption spectra and fluorescence spectra were adopted to evaluate the optical characteristics of as prepared (Zn/Al)LDH-co-Poly(MPC-AA-Fl) composites, which exhibited high intense green fluorescence. Furthermore, the endocytosis behavior indicates that (Zn/Al)LDH-co-Poly(MPC-AA-Fl) composites could be potentially used in cell imaging and even drug delivery application for their excellent biocompatibility and all advantages described above.

Surface functionalization of polyamide fiber via dopamine polymerization

NASA Astrophysics Data System (ADS)

Kuang, Xiao-Hui; Guan, Jin-Ping; Tang, Ren-Cheng; Chen, Guo-Qiang

2017-09-01

The oxidative polymerization of dopamine for the functional surface modification of textile fibers has drawn great attention. In this work, the functionalization of polyamide fiber via dopamine polymerization was studied with the aim of the fabrication of hydrophilic and antistatic surface. The conditions of dopamine application were first discussed in the absence of specific oxidants in terms of the apparent color depth of polyamide fiber. Dopamine concentration, pH and time were found to exert great impact on color depth. The highest color depth was achieved at pH 8.5. In the process of modification, polydopamine was deposited onto the surface of polyamide fiber. The modified polyamide fiber displayed a yellowish brown color with excellent wash and light color fastness, and exhibited good hydrophilic, UV protection and antistatic effects. A disadvantage of the present approach was the slow rate of dopamine polymerization and functionalization.

Synthesis of long Prebiotic Oligomers on Mineral Surfaces

NASA Technical Reports Server (NTRS)

Ferris, James P.; Hill, Aubrey R., Jr.; Liu, Rihe; Orgel, Leslie E.

1996-01-01

Most theories of the origin of biological organization assume that polymers with lengths in the range of 30-60 monomers are needed to make a genetic system viable. But it has not proved possible to synthesize plausibly prebiotic polymers this long by condensation in aqueous solution, because hydrolysis competes with polymerization. The potential of mineral surfaces to facilitate prebiotic polymerization was pointed out long ago. Here we describe a system that models prebiotic polymerization by the oligomerization of activated monomers -both nucleotides and amino acids. We find that whereas the reactions in solution produce only short oligomers (the longest typically being a 10-mer), the presence of mineral surfaces (montmorillonite for nucleotides, illite and hydroxylapatite for amino adds) induces the formation of oligomers up to 55 monomers long. These are formed by successive "feedings" with the monomers; polymerization takes place on the mineral surfaces in a manner akin to solid-phase synthesis of biopolymers.

Tensile bond strength between auto-polymerized acrylic resin and acrylic denture teeth treated with MF-MA solution.

PubMed

Thongrakard, Ticha; Wiwatwarrapan, Chairat

2016-08-01

This study evaluated the effect of chemical surface treatment using methyl formate-methyl acetate (MF-MA) solution on the tensile bond strength between acrylic denture teeth and auto-polymerized acrylic resin. Seventy maxillary central incisor acrylic denture teeth for each of three different brands (Yamahachi New Ace; Major Dent; Cosmo HXL) were embedded with incisal edge downwards in auto-polymerized resin in polyethylene pipes and ground with silicone carbide paper on their ridge lap surfaces. The teeth of each brand were divided into seven groups (n=10): no surface treatment (control group), MF-MA solution at a ratio of 25:75 (v/v) for 15 seconds, 30 seconds, 60 seconds, 120 seconds, 180 seconds, and MMA for 180 seconds. Auto-polymerized acrylic resin (Unifast Trad) was applied to the ground surface and polymerized in a pressure cooker. A tensile strength test was performed with a universal testing machine. Statistical analysis of the results was performed using two-way analysis of variance (ANOVA) and post-hoc Dunnett T3 test (α=.05). The surface treatment groups had significantly higher mean tensile bond strengths compared with the control group (P<.05) when compared within the same brand. Among the surface treatment groups of each brand, there were no significantly different tensile bond strengths between the MF-MA groups and the MMA 180 second group (P>.05), except for the Yamahachi New Ace MF-MA 180-second group (P<.05). 15-second MF-MA solution can be an alternative chemical surface treatment for repairing a denture base and rebonding acrylic denture teeth with auto-polymerized acrylic resin, for both conventional and cross-linked teeth.

The formation of the smallest fullerene-like carbon cages on metal surfaces

NASA Astrophysics Data System (ADS)

Ben Romdhane, F.; Rodríguez-Manzo, J. A.; Andrieux-Ledier, A.; Fossard, F.; Hallal, A.; Magaud, L.; Coraux, J.; Loiseau, A.; Banhart, F.

2016-01-01

The nucleation and growth of carbon on catalytically active metal surfaces is one of the most important techniques to produce nanomaterials such as graphene or nanotubes. Here it is shown by in situ electron microscopy that fullerene-like spherical clusters with diameters down to 0.4 nm and thus much smaller than C60 grow in a polymerized state on Co, Fe, or Ru surfaces. The cages appear on the surface of metallic islands in contact with graphene under heating to at least 650 °C and successively cooling to less than 500 °C. The formation of the small cages is explained by the segregation of carbon on a supersaturated metal, driven by kinetics. First principles energy calculations show that the clusters polymerize and can be attached to defects in graphene. Under compression, the polymerized cages appear in a crystalline structure.The nucleation and growth of carbon on catalytically active metal surfaces is one of the most important techniques to produce nanomaterials such as graphene or nanotubes. Here it is shown by in situ electron microscopy that fullerene-like spherical clusters with diameters down to 0.4 nm and thus much smaller than C60 grow in a polymerized state on Co, Fe, or Ru surfaces. The cages appear on the surface of metallic islands in contact with graphene under heating to at least 650 °C and successively cooling to less than 500 °C. The formation of the small cages is explained by the segregation of carbon on a supersaturated metal, driven by kinetics. First principles energy calculations show that the clusters polymerize and can be attached to defects in graphene. Under compression, the polymerized cages appear in a crystalline structure. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08212a

Fundamental Degradation Mechanisms of Multi-Functional Nanoengineered Surfaces

DTIC Science & Technology

2018-04-08

surface tension fluids with widely used lubricants for designing LIS. We considered a wide range of low surface tension fluids (12 to 48 mN/m) and...selection in designing stable LIS for the low surface tension fluids. Lastly, using steady state condensation experiments, we show that polymeric...polymeric coating to the high surface energy substrate and mechanical delamination of the coating. This finding will be key to future design

Synthesis of selenium nano-composite (t-Se@PS) by surface initiated atom transfer radical polymerization.

PubMed

Wang, Michael C P; Gates, Byron D

2012-09-04

Selenium nanostructures, which are otherwise susceptible to oxidative damage, were encapsulated with a thin layer of polystyrene. The thin layer of polystyrene was grafted onto the surfaces of selenium by a surface initiated atom transfer radical polymerization reaction. These encapsulated nanostructures demonstrate an enhanced resistance towards corrosion.

Polymerization Behavior and Polymer Properties of Eosin-Mediated Surface Modification Reactions.

PubMed

Avens, Heather J; Randle, Thomas James; Bowman, Christopher N

2008-10-17

Surface modification by surface-mediated polymerization necessitates control of the grafted polymer film thicknesses to achieve the desired property changes. Here, a microarray format is used to assess a range of reaction conditions and formulations rapidly in regards to the film thicknesses achieved and the polymerization behavior. Monomer formulations initiated by eosin conjugates with varying concentrations of poly(ethylene glycol) diacrylate (PEGDA), N-methyldiethanolamine (MDEA), and 1-vinyl-2-pyrrolidone (VP) were evaluated. Acrylamide with MDEA or ascorbic acid as a coinitiator was also investigated. The best formulation was found to be 40 wt% acrylamide with MDEA which yielded four to eight fold thicker films (maximum polymer thickness increased from 180 nm to 1420 nm) and generated visible films from 5-fold lower eosin surface densities (2.8 vs. 14 eosins/µm(2)) compared to a corresponding PEGDA formulation. Using a microarray format to assess multiple initiator surface densities enabled facile identification of a monomer formulation that yields the desired polymer properties and polymerization behavior across the requisite range of initiator surface densities.

Polymerization Behavior and Polymer Properties of Eosin-Mediated Surface Modification Reactions

PubMed Central

Avens, Heather J.; Randle, Thomas James; Bowman, Christopher N.

2008-01-01

Surface modification by surface-mediated polymerization necessitates control of the grafted polymer film thicknesses to achieve the desired property changes. Here, a microarray format is used to assess a range of reaction conditions and formulations rapidly in regards to the film thicknesses achieved and the polymerization behavior. Monomer formulations initiated by eosin conjugates with varying concentrations of poly(ethylene glycol) diacrylate (PEGDA), N-methyldiethanolamine (MDEA), and 1-vinyl-2-pyrrolidone (VP) were evaluated. Acrylamide with MDEA or ascorbic acid as a coinitiator was also investigated. The best formulation was found to be 40 wt% acrylamide with MDEA which yielded four to eight fold thicker films (maximum polymer thickness increased from 180 nm to 1420 nm) and generated visible films from 5-fold lower eosin surface densities (2.8 vs. 14 eosins/µm2) compared to a corresponding PEGDA formulation. Using a microarray format to assess multiple initiator surface densities enabled facile identification of a monomer formulation that yields the desired polymer properties and polymerization behavior across the requisite range of initiator surface densities. PMID:19838291

Influence of semisynthetic modification of the scaffold of a contact domain of HbS on polymerization: role of flexible surface topology in polymerization inhibition.

PubMed

Sonati, Srinivasulu; Bhutoria, Savita; Prabhakaran, Muthuchidambaran; Acharya, Seetharama A

2018-02-01

A new variant of HbS, HbS-Einstein with a deletion of segment α 23-26 in the B-helix, has been assembled by semisynthetic approach. B-helix of the α chain of cis αβ-dimer of HbS plays dominant role in the quinary interactions of deoxy HbS dimer. This B-helix is the primary scaffold that provides the orientation for the side chains of contact residues of this intermolecular contact domain. The design of HbS-Einstein has been undertaken to map the influence of perturbation of molecular surface topology and the flexibility of surface residues in the polymerization. The internal deletion exerts a strong inhibitory influence on Val-6 (β)-dependent polymerization, comparable to single contact site mutations and not for complete neutralization of Val-6(β)-dependent polymerization. The scaffold modification in cis-dimer is inhibitory, and is without any effect when present on the trans dimer. The flexibility changes in the surface topology in the region of scaffold modification apparently counteracts the intrinsic polymerization potential of the molecule. The inhibition is close to that of Le Lamentin mutation [His-20 (α) → Gln] wherein a mutation engineered without much change in flexibility of the contact domain. Interestingly, the chimeric HbS with swine-human chimeric α chain with multiple non-conservative mutations completely inhibits the Val-6(β)-dependent polymerization. The deformabilities of surface topology of chimeric HbS are comparable to HbS in spite of the multiple contact site mutations in the α-chain. We conclude that the design of antisickling Hbs for gene therapy of sickle cell disease should involve multiple mutations of intermolecular contact sites.

Accelerated cell-sheet recovery from a surface successively grafted with polyacrylamide and poly(N-isopropylacrylamide).

PubMed

Akiyama, Yoshikatsu; Kikuchi, Akihiko; Yamato, Masayuki; Okano, Teruo

2014-08-01

A double polymeric nanolayer consisting of poly(N-isopropylacrylamide) (PIPAAm) and hydrophilic polyacrylamide (PAAm) was deposited on tissue culture polystyrene (TCPS) surfaces using electron beam irradiation to form a new temperature-responsive cell culture surface in which the basal hydrophilic PAAm component in the double polymeric layer promotes the hydration of the upper PIPAAm layer and induces rapid cell detachment compared to a conventional temperature-responsive cell culture surface, PIPAAm-grafted TCPS (PIPAAm-TCPS). Take-off angle-dependent X-ray photoelectron spectroscopy spectral analysis demonstrated that the grafted PIPAAm and PAAm components were located in the upper and basal regions of the double polymeric layer, respectively, suggesting that the double polymeric layer forms an inter-penetrating-network-like structure with PAAm at the basal portion of the PIPAAm grafted chains. The wettability of the temperature-responsive cell culture surfaces with the double polymeric layer tended to be more hydrophilic, with an increase in the basal PAAm graft density at a constant PIPAAm graft density. However, when the graft densities of the upper PIPAAm and basal PAAm were optimized, the resulting temperature-responsive cell culture surface with the double polymeric layer exhibited rapid cell detachment while maintaining cell adhesive character comparable to that of PIPAAm-TCPS. The cell adhesive character was altered from cell-adhesive to cell-repellent with increasing PAAm or PIPAAm graft density. The cell adhesive character of the temperature-responsive cell culture surfaces was relatively consistent with their contact angles. These results strongly suggest that the basal PAAm surface properties affect the degree of hydration and dehydration of the subsequently grafted PIPAAm. In addition, the roles of the hydrophilic component in accelerating cell detachment are further discussed in terms of the mobility of the grafted PIPAAm chains. Applications of this insight might be useful for designing temperature-responsive cell culture surfaces for achieving efficient cell culture and quick target cell detachment. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Preparation of Transparent Bulk TiO2/PMMA Hybrids with Improved Refractive Indices via an in Situ Polymerization Process Using TiO2 Nanoparticles Bearing PMMA Chains Grown by Surface-Initiated Atom Transfer Radical Polymerization.

PubMed

Maeda, Satoshi; Fujita, Masato; Idota, Naokazu; Matsukawa, Kimihiro; Sugahara, Yoshiyuki

2016-12-21

Transparent TiO 2 /PMMA hybrids with a thickness of 5 mm and improved refractive indices were prepared by in situ polymerization of methyl methacrylate (MMA) in the presence of TiO 2 nanoparticles bearing poly(methyl methacrylate) (PMMA) chains grown using surface-initiated atom transfer radical polymerization (SI-ATRP), and the effect of the chain length of modified PMMA on the dispersibility of modified TiO 2 nanoparticles in the bulk hybrids was investigated. The surfaces of TiO 2 nanoparticles were modified with both m-(chloromethyl)phenylmethanoyloxymethylphosphonic acid bearing a terminal ATRP initiator and isodecyl phosphate with a high affinity for common organic solvents, leading to sufficient dispersibility of the surface-modified particles in toluene. Subsequently, SI-ATRP of MMA was achieved from the modified surfaces of the TiO 2 nanoparticles without aggregation of the nanoparticles in toluene. The molecular weights of the PMMA chains cleaved from the modified TiO 2 nanoparticles increased with increases in the prolonging of the polymerization period, and these exhibited a narrow distribution, indicating chain growth controlled by SI-ATRP. The nanoparticles bearing PMMA chains were well-dispersed in MMA regardless of the polymerization period. Bulk PMMA hybrids containing modified TiO 2 nanoparticles with a thickness of 5 mm were prepared by in situ polymerization of the MMA dispersion. The transparency of the hybrids depended significantly on the chain length of the modified PMMA on the nanoparticles, because the modified PMMA of low molecular weight induced aggregation of the TiO 2 nanoparticles during the in situ polymerization process. The refractive indices of the bulk hybrids could be controlled by adjusting the TiO 2 content and could be increased up to 1.566 for 6.3 vol % TiO 2 content (1.492 for pristine PMMA).

Hydrophilic crosslinked-polymeric surface capable of effective suppression of protein adsorption

NASA Astrophysics Data System (ADS)

Kamon, Yuri; Inoue, Naoko; Mihara, Erika; Kitayama, Yukiya; Ooya, Tooru; Takeuchi, Toshifumi

2016-08-01

We investigated the nonspecific adsorption of proteins towards three hydrophilic crosslinked-polymeric thin layers prepared by surface-initiated atom transfer radical polymerization using N,N‧-methylenebisacrylamide, 2-(methacryloyloxy)ethyl-[N-(2-methacryloyloxy)ethyl]phosphorylcholine (MMPC), or 6,6‧-diacryloyl-trehalose crosslinkers. Protein binding experiments were performed by surface plasmon resonance with six proteins of different pI values including α-lactalbumin, bovine serum albumin (BSA), myoglobin, ribonuclease A, cytochrome C, and lysozyme in buffer solution at pH 7.4. All of the obtained crosslinked-polymeric thin layers showed low nonspecific adsorption of negatively charged proteins at pH 7.4 such as α-lactalbumin, BSA, and myoglobin. Nonspecific adsorption of positively charged proteins including ribonuclease A, cytochrome C, and lysozyme was the lowest for poly(MMPC). These results suggest poly(MMPC) can effectively reduce nonspecific adsorption of a wide range of proteins that are negatively or positively charged at pH 7.4. MMPC is a promising crosslinker for a wide range of polymeric materials requiring low nonspecific protein binding.

Control of in vivo disposition and immunogenicity of polymeric micelles by adjusting poly(sarcosine) chain lengths on surface

NASA Astrophysics Data System (ADS)

Kurihara, Kensuke; Ueda, Motoki; Hara, Isao; Ozeki, Eiichi; Togashi, Kaori; Kimura, Shunsaku

2017-07-01

Four kinds of A3B-type amphiphilic polydepsipeptides, (poly(sarcosine))3- b-poly( l-lactic acid) (the degree of polymerization of poly(sarcosine) are 10, 33, 55, and 85; S10 3 , S33 3 , S55 3 , and S85 3 ) were synthesized to prepare core-shell type polymeric micelles. Their in vivo dispositions and stimulations to trigger immune system to produce IgM upon multiple administrations to mice were examined. With increasing poly(sarcosine) chain lengths, the hydrophilic shell became thicker and the surface density at the most outer surface decreased on the basis of dynamic and static light scattering measurements. These two physical elements of polymeric micelles elicited opposite effects on the immune response in light of the chain length therefore to show an optimized poly(sarcosine) chain length existing between 33mer and 55mer to suppress the accelerated blood clearance phenomenon associated with polymeric micelles.

Superwettability-Induced Confined Reaction toward High-Performance Flexible Electrodes.

PubMed

Xiong, Weiwei; Liu, Hongliang; Zhou, Yahong; Ding, Yi; Zhang, Xiqi; Jiang, Lei

2016-05-18

To find a general strategy to realize confinement of the conductive layer for high-performance flexible electrodes, with improved interfacial adhesion and high conductivity, is of important scientific significance. In this work, superwettability-induced confined reaction is used to fabricate high-performance flexible Ag/polymer electrodes, showing significantly improved silver conversion efficiency and interfacial adhesion. The as-prepared flexible electrodes by superhydrophilic polymeric surface under oil are highly conductive with an order of magnitude higher than the Ag/polymer electrodes obtained from original polymeric surface. The high conductivity achieved via superhydrophilic confinement is ascribed to the fact that the superhydrophilic polymeric surface can enhance the reaction rate of silver deposition and reduce the size of silver nanoparticles to achieve the densest packing. This new approach will provide a simple method to fabricate flexible and highly conductive Ag/polymer electrodes with excellent adhesion between the conductive layer and the substrate, and can be extended to other metal/polymeric electrodes or alloy/polymeric electrodes.

Fractal atomic surfaces of self-similar quasiperiodic tilings of the plane

NASA Astrophysics Data System (ADS)

Godrèche, C.; Luck, J. M.; Janner, A.; Janssen, T.

1993-09-01

We consider in parallel three self-similar quasiperiodic tilings of the plane with eight-fold symmetry, made of two prototiles, the square and the 45-degree rhomb. They possess the same inflation rules up to a reordering of the tiles. We study the consequences of this reordering on the nature of the atomic surfaces, or acceptance domains, and on the Fourier spectra of the tilings. For two of the tilings the atomic surface has a fractal boundary. For one of them it is not a connected set. We argue that the situation described in this paper is generic. Nous considérons en parallèle trois pavages quasipériodiques auto-similaires du plan, de symétrie de rotation d'ordre huit, et constitués des deux mêmes tuiles : le carré et le losange à 45 degrés. Les trois pavages sont décrits par les mêmes règles d'inflation, à une permutation des tuiles près. Nous étudions l'influence de cette permutation sur les surfaces atomiques, ou domaines d'acceptance, et sur les spectres de Fourier des pavages. Le bord de la surface atomique de deux des pavages est fractal ; pour l'un d'entre eux ce bord n'est pas connexe. Les propriétés décrites sur cette famille d'exemples sont vraisemblablement génériques.

Synthesis of Biocompatible Surfaces by Different Techniques

DTIC Science & Technology

2002-04-01

production . In the other hand, polymers are widely used in bone/cartilage implants, both, as polymeric materials themselves and as a polymeric surface on a...focus on the production of HA scaffolds by a sol-gel method using different drying processes, and on the study of the plasma polymerization technique to...precursor at 3. SA-stoichiometric amount (to maintain Ca/P= 1,67) of the calcium precursor solution (3 M solution in anhidrous etanol ) was added dropwise

Polymer-modified opal nanopores.

PubMed

Schepelina, Olga; Zharov, Ilya

2006-12-05

The surface of nanopores in opal films, assembled from 205 nm silica spheres, was modified with poly(acrylamide) brushes using surface-initiated atom transfer radical polymerization. The colloidal crystal lattice remained unperturbed by the polymerization. The polymer brush thickness was controlled by polymerization time and was monitored by measuring the flux of redox species across the opal film using cyclic voltammetry. The nanopore size and polymer brush thickness were calculated on the basis of the limiting current change. Polymer brush thickness increased over the course of 26 h of polymerization in a logarithmic manner from 1.3 to 8.5 nm, leading to nanopores as small as 7.5 nm.

Self-folding polymeric containers for encapsulation and delivery of drugs

PubMed Central

Fernandes, Rohan; Gracias, David H.

2012-01-01

Self-folding broadly refers to self-assembly processes wherein thin films or interconnected planar templates curve, roll-up or fold into three dimensional (3D) structures such as cylindrical tubes, spirals, corrugated sheets or polyhedra. The process has been demonstrated with metallic, semiconducting and polymeric films and has been used to curve tubes with diameters as small as 2 nm and fold polyhedra as small as 100 nm, with a surface patterning resolution of 15 nm. Self-folding methods are important for drug delivery applications since they provide a means to realize 3D, biocompatible, all-polymeric containers with well-tailored composition, size, shape, wall thickness, porosity, surface patterns and chemistry. Self-folding is also a highly parallel process, and it is possible to encapsulate or self-load therapeutic cargo during assembly. A variety of therapeutic cargos such as small molecules, peptides, proteins, bacteria, fungi and mammalian cells have been encapsulated in self-folded polymeric containers. In this review, we focus on self-folding of all-polymeric containers. We discuss the mechanistic aspects of self-folding of polymeric containers driven by differential stresses or surface tension forces, the applications of self-folding polymers in drug delivery and we outline future challenges. PMID:22425612

Recruiting physisorbed water in surface polymerization for bio-inspired materials of tunable hydrophobicity

DOE PAGES

Oyola-Reynoso, S.; Tevis, I. D.; Chen, J.; ...

2016-08-18

Here, chemical grafting has been widely used to modify the surface properties of materials, especially surface energy for controlled wetting, because of the resilience of such coatings/modifications. Reagents with multiple reactive sites have been used with the expectation that a monolayer will form. The step-growth polymerization mechanism, however, suggests the possibility of gel formation for hydrolyzable moieties in the presence of physisorbed water. In this report, we demonstrated that using alkyltrichlorosilanes (trivalent [i.e., 3 reactive sites]) in the surface modification of a cellulosic material (paper) does not yield a monolayer but rather gives surface-bound particles. We infer that the presencemore » of physisorbed (surface-bound) water allows for polymerization (or oligomerization) of the silane prior to its attachment on the surface. Surface energy mismatch between the hydrophobic tails of the growing polymer and any unreacted bound water leads to the assembly of the polymerizing material into spherical particles to minimize surface tension. By varying paper grammage (16.2–201.4 g m –2), we varied the accessible surface area and thus the amount of surface-adsorbed water, allowing us to control the ratio of the silane to the bound water. Using this approach, polymeric particles were formed on the surface of cellulose fibers ranging from ~70 nm to a film. The hydrophobicity of the surface, as determined by water contact angles, correlates with particle sizes (p < 0.001, Student's t-test), and, hence, the hydrophobicity can be tuned (contact angle between 94° and 149°). Using a model structure of a house, we demonstrated that as a result of this modification, paper-based houses can be rendered self-cleaning or tolerant to surface running water. In another application, we demonstrated that the felicitous choice of architectural design allows for the hydrophobic paper to be used for water harvesting.« less

1995 Annual Report and Five Year (1995-1999) Strategic Investment Plan

DTIC Science & Technology

1996-08-01

fouling release hull coatings exploiting the low surface energy of surface oriented perfluorinated alkyl compounds . This project is a continuation...would not be able to adhere to it. The lowest surface free energies can be created by adsorbed monolayers of closely packed perfluorinated compounds ...embedding such molecules into the surface of polymeric matrices, and by binding the perfluorinated compounds into a polymeric backbone to create comb type

Synthesis and Free Radical Polymerization of Fluorinated Polyhedral Oligomeric Silsesquioxane (F-POSS) Macromers: Precursors for Low Surface Energy Materials and Devices

DTIC Science & Technology

2012-04-01

Methanol Octane Methylene Iodide Water Superhydrophobic /oleophilic dip-coated fabric Tuteja et al, Science, 2007, 318, 1618 Superamphiphobic...building block material for low surface energy materials • Applications – Mechanical robust superhydrophobic /oleophobic/omniphobic surfaces • Via...non-wetting polymeric surfaces 5 mm Methanol Octane Methylene Iodide Water Superhydrophobic /oleophilic dip-coated fabric Tuteja et al, Science, 2007

Preparation of end-grafted polymer brushes by nitroxide-mediated free radical polymerization of vaporized vinyl monomers.

PubMed

Li, Jun; Chen, Xiaoru; Chang, Ying-Chih

2005-10-11

In this work, we report a gas-phase polymerization approach to create end-grafted vinyl based polymer films on silicon oxide based substrates. The "surface-initiated vapor deposition polymerization" (SI-VDP) of vaporized vinyl monomers, via the nitroxide-mediated free radical polymerization mechanism, was developed to fabricate various homo- and block copolymer brushes from surface-bound initiators, 1-(4'-oxa-2'-phenyl-12'-trimethoxysilyldodecyloxy)-2,2,6,6-tetra-methylpiperidine ("TEMPO"). The resulting polymer thin films were characterized by the Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ellipsometry, and contact angle goniometry, respectively, to identify the surface composition, film thickness, surface coverage, and water contact angles. Through the SI-VDP, end-grafted polymer films of polystyrene (PSt), poly(acrylic acid) (PAAc), poly(N-(2-hydroxypropyl) methacrylamide) (PHPMA), and poly(N-isopropylacrylamide) (PNIPAAm) with 10-200 nm thicknesses were fabricated. Furthermore, the block copolymer films of PAAc (1st block)-b-PSt (2nd block), PSt (1st block)-b-PAAc (2nd block), and a triblock copolymer film of PAAc (1st)-b-PSt (2nd)-b-PHPMA (3rd), were also fabricated, suggesting the "renewability" of the TEMPO-initiated polymerization in the SI-VDP scheme. It is also noticed that the SI-VDP is more efficient than the conventional solution phase polymerization in producing functional polymer brushes such as PNIPAAm, PAAc, or PAAc-b-PSt end-grafted films. In summary, our studies have shown clear advantages of the SI-VDP setup for the nitroxide-mediated polymerization scheme in controlling synthesis of end-grafted homo- and copolymer thin films.

Littoral Infrared Ship Self Defence Technology Studies (Autodefense cotiere infrarouge des navires etudes technologiques)

DTIC Science & Technology

2014-05-01

de simulation du Simulateur de Contre- mesures de la Menace Navale afin de pouvoir inclure des leurres et des autodirecteurs de missiles ; 4) Une...sur le littoral ; 2) La détection des petites cibles de surface sur le littoral ; 3) L’amélioration et la validation de la modélisation et du code...amélioration et une validation supplémentaire de la modélisation et du

Modeling phosphorus losses from soils amended with cattle manures and chemical fertilizers.

PubMed

Wang, Zhaozhi; Zhang, T Q; Tan, C S; Vadas, P; Qi, Z M; Wellen, C

2018-05-22

While applied manure/fertilizer is an important source of P loss in surface runoff, few models simulate the direct transfer of phosphorus (P) from soil-surface-applied manure/fertilizer to surface runoff. The SurPhos model was tested with 2008-2010 growing season daily surface runoff data from clay loam experimental plots subject to different manure/fertilizer applications. Model performance was evaluated on the basis of the coefficient of determination (R 2 ), Nash-Sutcliffe efficiency (NSE), percent bias (PBIAS), and the ratio of the root mean square error to the standard deviation of observed values (RSR). The model offered an acceptable performance in simulating soil labile P dynamics (R 2  = 0.75, NSE = 0.55, PBIAS = 10.43%, and RSR = 0.67) and dissolved reactive P (DRP) loss in surface runoff (R 2  ≥ 0.74 and NSE ≥ 0.69) for both solid and liquid cattle manure, as well as inorganic fertilizer. Simulated direct P loss in surface runoff from solid and liquid cattle manure accounted for 39% and 40% of total growing season DRP losses in surface runoff. To compensate for the unavailability of daily surface runoff observations under snow melt condition, the whole four years' (2008-2011) daily surface runoff predicted by EPIC (Environmental Policy Integrated Climate) was used as SurPhos input. The accuracy of simulated DRP loss in surface runoff under the different manure/fertilizer treatments was acceptable (R 2  ≥ 0.55 and NSE ≥ 0.50). For the solid cattle manure treatment, of all annual DRP losses, 19% were derived directly from the manure. Beyond offering a reliable prediction of manure/fertilizer P loss in surface runoff, SurPhos quantified different sources of DRP loss and dynamic labile P in soil, allowing a better critical assessment of different P management measures' effectiveness in mitigating DRP losses. Copyright © 2018 Elsevier B.V. All rights reserved.

Synthesis of surface-anchored DNA-polymer bioconjugates using reversible addition-fragmentation chain transfer polymerization.

PubMed

He, Peng; He, Lin

2009-07-13

We report here an approach to grafting DNA-polymer bioconjugates on a planar solid support using reversible addition-fragmentation chain transfer (RAFT) polymerization. In particular, a trithiocarbonate compound as the RAFT chain transfer agent (CTA) is attached to the distal point of a surface-immobilized oligonucleotide. Initiation of RAFT polymerization leads to controlled growth of polymers atop DNA molecules on the surface. Growth kinetics of poly(monomethoxy-capped oligo(ethylene glycol) methacrylate) atop DNA molecules is investigated by monitoring the change of polymer film thickness as a function of reaction time. The reaction conditions, including the polymerization temperature, the initiator concentration, the CTA surface density, and the selection of monomers, are varied to examine their impacts on the grafting efficiency of DNA-polymer conjugates. Comparing to polymer growth atop small molecules, the experimental results suggest that DNA molecules significantly accelerate polymer growth, which is speculated as a result of the presence of highly charged DNA backbones and purine/pyrimidine moieties surrounding the reaction sites.

Amelioration de l'adhesion de revetements organiques deposes par plasma froid sur polymeres pour applications biomedicales

NASA Astrophysics Data System (ADS)

Sbai, Marouan

Plasma surface modification is commonly used in biomedical field, for example to enhance cell adhesion and growth surrounding the stent covers without affecting its bulk properties. Plasma polymer (PP) deposition used to create thin films rich in functional groups, e.g. primary amines, known to enhance the cellular response and allow grafting of biomolecules especially on stent grafts. Thin film adhesion to stent polymeric cover should be considered especially as they will evolve in a biological environment. The aim of this project is to evaluate the adhesion of PP on polytetrafluoroethylene (PTFE) and polyethyleneterephthalate (PET). Thereafter, an ammonia plasma treatment on PTFE is performed prior to deposition of PP to optimize the PP/PTFE adhesion. PP studied here (referred to as "LP") is prepared from a mixture of ethylene (C2H4) and ammonia (NH3). It is deposited on two supports, PET and PTFE. The interfacial adhesion between the LP coating and the substrate was evaluated by "Peel-test 180 °" according to ASTM F1842. Staining of the surface after peel test followed by an image analysis was performed to determine the percentage of removed coating. Adhesion optimization is done by varying operating plasma parameters such as power, pressure and pretreatment time. Chemical analyses and wettability of LP and pretreated surfaces in dry and wet conditions are characterized by XPS and contact angle measurements, respectively. The adhesion of LP/PET was excellent in a dry environment (<1%), but lower under wet conditions (4+/-6% and 44+/-7% as minimum and maximum values at 5min and 60min of immersion in deionized water, respectively). However, 56% to 75% of the LP is removed from virgin PTFE in a dry and wet environment, respectively; percentages can be substantially reduced by plasma pretreatment (0% and 8+/-3% in air and 30min in deionized water). Almost no delamination was observed with NH3 plasma pretreatment at 15s, 100 mTorr and 50W. N2 plasma pretreatment, for comparison, proves much less effective. The LP/PTFE adhesion is considerably improved by plasma pretreatment compared to untreated samples. The chemical LP composition and the cell growth on LP/pretreated PTFE are not significantly affected by this pretreatment. Further investigations are required to explain the LP/PET low adhesion in wet conditions.

Morphology of poly-p-xylylene crystallized during polymerization.

NASA Technical Reports Server (NTRS)

Kubo, S.; Wunderlich, B.

1971-01-01

The morphology of as-polymerized poly-p-xylylene grown between -17 and 30 C is found to consist of lame llar alpha crystals oriented with the (010) plane parallel to the support surface. The crystallinity decreases with decreasing polymerization temperature. Spherulitic and nonspherulitic portions of the polymer film consist of folded chain lamellas with the chain axis parallel to the support surface. The results were obtained by small- and wide-angle X-ray measurements, electron and optical microscopy, and differential thermal analysis.

The Effect of Surface Pressure on the Langmuir-Blodgett Polymerization of 2-Pentadecyl Aniline

DTIC Science & Technology

1992-05-19

the mean molecular area was decreasing during the polymerization of 2-pentadecyl aniline . Also no polymer was found when the reaction was run at low...and polymer, we suppose, is the cause of Mma decrease during the polymerization of 2-pentadecyl aniline . Compared with the area of a long alkyl ...is put into changing its conformation at the surface. In the case of 2-pentadecyl aniline , the work done upon compressing the monolayer, we suppose, is

In situ AFM investigation of electrochemically induced surface-initiated atom-transfer radical polymerization.

PubMed

Li, Bin; Yu, Bo; Zhou, Feng

2013-02-12

Electrochemically induced surface-initiated atom-transfer radical polymerization is traced by in situ AFM technology for the first time, which allows visualization of the polymer growth process. It affords a fundamental insight into the surface morphology and growth mechanism simultaneously. Using this technique, the polymerization kinetics of two model monomers were studied, namely the anionic 3-sulfopropyl methacrylate potassium salt (SPMA) and the cationic 2-(metharyloyloxy)ethyltrimethylammonium chloride (METAC). The growth of METAC is significantly improved by screening the ammonium cations by the addition of ionic liquid electrolyte in aqueous solution. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymer-phyllosilicate nanocomposites and their preparation

DOEpatents

Chaiko, David J.

2007-01-09

Polymer-phyllosilicate nanocomposites that exhibit superior properties compared to the polymer alone, and methods-for producing these polymer-phyllosilicate nanocomposites, are provided. Polymeric surfactant compatabilizers are adsorbed onto the surface of hydrophilic or natural phyllosilicates to facilitate the dispersal and exfoliation of the phyllosilicate in a polymer matrix. Utilizing polymeric glycol based surfactants, polymeric dicarboxylic acids, polymeric diammonium surfactants, and polymeric diamine surfactants as compatabilizers facilitates natural phyllosilicate and hydrophilic organoclay dispersal in a polymer matrix to produce nanocomposites.

Durable superhydrophobic and superamphiphobic polymeric surfaces and their applications: A review.

PubMed

Ellinas, Kosmas; Tserepi, Angeliki; Gogolides, Evangelos

2017-12-01

Wetting control is essential for many applications, such as self-cleaning, anti-icing, anti-fogging, antibacterial action as well as anti-reflection and friction control. While significant effort has been devoted to fabricate superhydrophobic/superamphiphobic surfaces (repellent to water and other low surface tension liquids), very few polymeric superhydrophobic/superamphiphobic surfaces can be considered as durable against various externally imposed stresses (e.g. application of heating, pressure, mechanical forces, chemical, etc.). Therefore, durability tests are extremely important for applications especially when such surfaces are made of "soft" materials. Here, we review the most recent and promising efforts reported towards the realization of durable, superhydrophobic/superamphiphobic, polymeric surfaces emphasizing the durability tests performed, and some important applications. We compare and put in context the scattered durability tests reported in the literature, and present conclusions, perspectives and challenges in the field. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of Functional Groups on Biodegradation and Pre-osteoblastic Cell Response on the Plasma-Polymerized Magnesium Surface

NASA Astrophysics Data System (ADS)

Ko, Yeong-Mu; Lee, Kang; Kim, Byung-Hoon

2013-01-01

Magnesium (Mg) is light, has biocompatibility, and has mechanical properties close to those of natural bone. However, pure Mg severely corrodes in a physiological environment, which may result in fracture prior to substantial tissue healing. In this study, the Mg surface was modified by depositing a thin polymeric film containing COOH, NH2, and OH groups through plasma polymerization of acrylic acid, allyl amine, and allyl alcohol in order to improve its anticorrosion and bioactive properties. The -COOH group had a significant effect on bonelike apatite formation compared with -NH2 and -OH. It was also concluded that a bonelike-apatite formed COOH/Mg surface was more effective for reducing biodegradation rate than the other surfaces. The results of in vitro cell test revealed significantly enhanced cell proliferation and differentiation on the COOH/Mg and NH2/Mg surfaces compared with other surfaces.

Relationship between Leakage Current and Pollution Deposits on the Surface of Polymeric Insulator

NASA Astrophysics Data System (ADS)

Miyake, Takuma; Seo, Yuya; Sakoda, Tatsuya; Otsubo, Masahisa

Application of polymeric materials used for housing insulators is considered. However, because polymeric insulator is organic matter, the aged deterioration is anxious. The lifetime of polymeric insulator is influenced by environmental conditions such as ultraviolet, acid rain, and polluted deposits. A change of the surface condition of polymeric material causes the dry band arc discharge and the discharge may lower the insulation strength. To investigate the relationship between insoluble pollution and occurrence of dry band arc discharge, we performed a salt-fog test with ethylene vinyl acetate (EVA) samples. The results showed that the heavy erosion caused by frequent dry band arc discharges occurred even in the case of a light polluted condition. Additionally, a very characteristic increase tendency in leakage current with a period of about 5 h was observed during the mist period.

Elaboration of nano-structured grafted polymeric surface.

PubMed

Vrlinic, Tjasa; Debarnot, Dominique; Mozetic, Miran; Vesel, Alenka; Kovac, Janez; Coudreuse, Arnaud; Legeay, Gilbert; Poncin-Epaillard, Fabienne

2011-10-15

The surface grafting of multi-polymeric materials can be achieved by grafting as components such as polymers poly(N-isopropylacrylamide) and/or surfactant molecules (hexatrimethylammonium bromide, polyoxyethylene sorbitan monolaurate). The chosen grafting techniques, i.e. plasma activation followed by coating, allow a large spectrum of functional groups that can be inserted on the surface controlling the surface properties like adhesion, wettability and biocompatibility. The grafted polypropylene surfaces were characterized by contact angle analyses, XPS and AFM analyses. The influence of He plasma activation, of the coating parameters such as concentrations of the various reactive agents are discussed in terms of hydrophilic character, chemical composition and morphologic surface heterogeneity. The plasma pre-activation was shown inevitable for a permanent polymeric grafting. PNIPAM was grafted alone or with a mixture of the surfactant molecules. Depending on the individual proportion of each component, the grafted surfaces are shown homogeneous or composed of small domains of one component leading to a nano-structuration of the grafted surface. Copyright © 2011 Elsevier Inc. All rights reserved.

Chain polymerization of diacetylene compound multilayer films on the topmost surface initiated by a scanning tunneling microscope tip.

PubMed

Takajo, Daisuke; Okawa, Yuji; Hasegawa, Tsuyoshi; Aono, Masakazu

2007-05-08

Chain polymerizations of diacetylene compound multilayer films on graphite substrates were examined with a scanning tunneling microscope (STM) at the liquid/solid interface of the phenyloctane solution. The first layer grew very quickly into many small domains. This was followed by the slow formation of the piled up layers into much larger domains. Chain polymerization on the topmost surface layer could be initiated by applying a pulsed voltage between the STM tip and the substrate, usually producing a long polymer of submicrometer length. In contrast, polymerizations on the underlying layer were never observed. This can be explained by a conformation model in which the polymer backbone is lifted up.

Fast Disinfecting Antimicrobial Surfaces

PubMed Central

Madkour, Ahmad E.; Dabkowski, Jeffery M.; Nüsslein, Klaus; Tew, Gregory N.

2013-01-01

Silicon wafers and glass surfaces were functionalized with facially amphiphilic antimicrobial copolymers using the “grafting from” technique. Surface initiated atom transfer radical polymerization (ATRP) was used to grow poly(butylmethacrylate)-co-poly(Boc-aminoethyl methacrylate) from the surfaces. Upon Boc-deprotection, these surfaces became highly antimicrobial and killed S. aureus and E. coli 100% in less than 5 min. The molecular weight and grafting density of the polymer were controlled by varying the polymerization time and initiator surface density. Antimicrobial studies showed that the killing efficiency of these surfaces was independent of polymer layer thickness or grafting density within the range of surfaces studied. PMID:19177651

Mass and Charge Transport in Electronically Conductive Polymers

DTIC Science & Technology

1990-08-02

This method is based on coating an electrode surface with an insulating nitrile butadiene rubber ( NBR ). The electrolyte for polymerization (LiCIO4...in acetonitrile) etches channels through the NBR ; pyrrole is then polymerized in these channels. After polymerization the NBR is extracted away with

Modeling phosphorus losses from soils amended with cattle manure and chemical fertilizers

USDA-ARS?s Scientific Manuscript database

While applied manure/fertilizer is an important source of P loss in surface runoff, few models simulate the direct transfer of phosphorus (P) from soil-surface-applied manure/fertilizer to runoff. The SurPhos model was tested with 2008-2010 growing season, daily surface runoff data from clay loam ex...

FIRE_AX_SOF_SUR_MET

Atmospheric Science Data Center

2015-11-25

... Buoy Instrument:  Barometer Sonic Anemometer Thermistor Spatial Coverage:  (34.60, ... Earthdata Search Parameters:  Dry Bulb Temperature Pressure Sea Surface Temperature Wet Bulb Temperature ...

Self-folding polymeric containers for encapsulation and delivery of drugs.

PubMed

Fernandes, Rohan; Gracias, David H

2012-11-01

Self-folding broadly refers to self-assembly processes wherein thin films or interconnected planar templates curve, roll-up or fold into three dimensional (3D) structures such as cylindrical tubes, spirals, corrugated sheets or polyhedra. The process has been demonstrated with metallic, semiconducting and polymeric films and has been used to curve tubes with diameters as small as 2nm and fold polyhedra as small as 100nm, with a surface patterning resolution of 15nm. Self-folding methods are important for drug delivery applications since they provide a means to realize 3D, biocompatible, all-polymeric containers with well-tailored composition, size, shape, wall thickness, porosity, surface patterns and chemistry. Self-folding is also a highly parallel process, and it is possible to encapsulate or self-load therapeutic cargo during assembly. A variety of therapeutic cargos such as small molecules, peptides, proteins, bacteria, fungi and mammalian cells have been encapsulated in self-folded polymeric containers. In this review, we focus on self-folding of all-polymeric containers. We discuss the mechanistic aspects of self-folding of polymeric containers driven by differential stresses or surface tension forces, the applications of self-folding polymers in drug delivery and we outline future challenges. Copyright © 2012 Elsevier B.V. All rights reserved.

A multifunctional polymeric nanofilm with robust chemical performances for special wettability.

PubMed

Wang, Yabin; Lin, Feng; Dong, Yaping; Liu, Zhong; Li, Wu; Huang, Yudong

2016-03-07

A multifunctional polymeric nanofilm of a triazinedithiolsilane compound, which can protect metallic substrates and activate the corresponding surface simultaneously, is introduced onto a copper mesh surface via facile solution-immersion approaches. The resultant interface exhibits hydrophilic features due to the existence of silanol groups (SiOH) outward and has the potential to act as a superhydrophilic and underwater superoleophobic material. As the polymeric nanofilm atop the copper mesh is modified with long-chain octadecyltrichlorosilane (OTS), the functionalized surface becomes superhydrophobic and superoleophilic. The OTS-modified polymeric nanofilm shows outstanding chemical durability and stability that are seldom concurrently satisfied for a material with special wettability, owing to its inherent architecture. These textures generate high separation efficiency, durable separation capability and excellent thermal stability. The protective ability, originating from the textures of the underlying cross-linked disulfide units (-SS-) and siloxane networks (SiOSi) on the top of the nanofilm, prolongs the chemical durability. The activating capability stemming from the residual SiOH groups improves the chemical stability as a result of the chemical bonds developed by these sites. The significant point of this investigation lies in enlightening us on the fabrication of multifunctional polymeric nanofilms on different metal surfaces using various triazinedithiolsilane compounds, and on the construction of interfaces with controllable wettable performances in demanding research or industrial applications.

Fabrication of the superhydrophobic surface on aluminum alloy by anodizing and polymeric coating

NASA Astrophysics Data System (ADS)

Liu, Wenyong; Luo, Yuting; Sun, Linyu; Wu, Ruomei; Jiang, Haiyun; Liu, Yuejun

2013-01-01

We reported the preparation of the superhydrophobic surface on aluminum alloy via anodizing and polymeric coating. Both the different anodizing processes and different polymeric coatings of aluminum alloy were investigated. The effects of different anodizing conditions, such as electrolyte concentration, anodization time and current on the superhydrophobic surface were discussed. The results showed that a good superhydrophobic surface was facilely fabricated by polypropylene (PP) coating after anodizing. The optimum conditions for anodizing were determined by orthogonal experiments. When the concentration of oxalic acid was 10 g/L, the concentration of NaCl was 1.25 g/L, anodization time was 40 min, and anodization current was 0.4 A, the best superhydrophobic surface on aluminum alloy with the contact angle (CA) of 162° and the sliding angle of 2° was obtained. On the other hand, the different polymeric coatings, such as polystyrene (PS), polypropylene (PP) and polypropylene grafting maleic anhydride (PP-g-MAH) were used to coat the aluminum alloy surface after anodizing. The results showed that the superhydrophobicity was most excellent by coating PP, while the duration of the hydrophobic surface was poor. By modifying the surface with the silane coupling agent before PP coating, the duration of the superhydrophobic surface was improved. The morphologies of the superhydrophobic surface were further confirmed by optical microscope (OM) and scanning electron microscope (SEM). Combined with the material of PP with the low surface free energy, the micro/nano-structures of the surface resulted in the superhydrophobicity of the aluminum alloy surface.

High-efficiency preparation of poly(2-methacryloyloxyethyl phosphorylcholine) grafting layer on poly(ether ether ketone) by photoinduced and self-initiated graft polymerization in an aqueous solution in the presence of inorganic salt additives.

PubMed

Shiojima, Taro; Inoue, Yuuki; Kyomoto, Masayuki; Ishihara, Kazuhiko

2016-08-01

A highly efficient methodology for preparing a poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) layer on the surface of poly(ether ether ketone) (PEEK) was examined by photoinduced and self-initiated graft polymerization. To enhance the polymerization rate, we demonstrated the effects of inorganic salt additives in the feed monomer solution on thickness of grafted PMPC layer. Photoinduced polymerization occurred and the PMPC graft layer was successfully formed on the PEEK surface, regardless of inorganic salt additives. Moreover, it was clearly observed that the addition of inorganic salt enhanced the grafting thickness of PMPC layer on the surface even when the photoirradiation time was shortened. The addition of inorganic salt additives in the feed monomer solution enhanced the polymerization rate of MPC and resulted in thicker PMPC layers. In particular, we evaluated the effect of NaCl concentration and how this affected the polymerization rate and layer thickness. We considered that this phenomenon was due to the hydration of ions in the feed monomer solution and subsequent apparent increase in the MPC concentration. A PMPC layer with over 100-nm-thick, which was prepared by 5-min photoirradiation in 2.5mol/L inorganic salt aqueous solution, showed good wettability and protein adsorption resistance compared to that of untreated PEEK. Hence, we concluded that the addition of NaCl into the MPC feed solution would be a convenient and efficient method for preparing a graft layer on PEEK. Photoinduced and self-initiated graft polymerization on the PEEK surface is one of the several methodologies available for functionalization. However, in comparison with free-radical polymerization, the efficiency of polymerization at the solid-liquid interface is limited. Enhancement of the polymerization rate for grafting could solve the problem. In this study, we observed the acceleration of the polymerization rate of MPC in an aqueous solution by the addition of inorganic salt. The salt itself did not show any adverse effects on the radical polymerization; however, the apparent concentration of the monomer in feed may be increased due to the hydration of ions attributed to salt additives. We could obtain PMPC-grafted PEEK with sufficient PMPC thickness to obtain good functionality with only 5-min photoirradiation by using 2.5mol/L NaCl in the feed solution. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Imaging nanowire plasmon modes with two-photon polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gruber, Christian; Trügler, Andreas; Hohenester, Ulrich

2015-02-23

Metal nanowires sustain propagating surface plasmons that are strongly confined to the wire surface. Plasmon reflection at the wire end faces and interference lead to standing plasmon modes. We demonstrate that these modes can be imaged via two-photon (plasmon) polymerization of a thin film resist covering the wires and subsequent electron microscopy. Thereby, the plasmon wavelength and the phase shift of the nanowire mode picked up upon reflection can be directly retrieved. In general terms, polymerization imaging is a promising tool for the imaging of propagating plasmon modes from the nano- to micro-scale.

Real-time monitoring of surface-initiated atom transfer radical polymerization using silicon photonic microring resonators: implications for combinatorial screening of polymer brush growth conditions.

PubMed

Limpoco, F Ted; Bailey, Ryan C

2011-09-28

We directly monitor in parallel and in real time the temporal profiles of polymer brushes simultaneously grown via multiple ATRP reaction conditions on a single substrate using arrays of silicon photonic microring resonators. In addition to probing relative polymerization rates, we show the ability to evaluate the dynamic properties of the in situ grown polymers. This presents a powerful new platform for studying modified interfaces that may allow for the combinatorial optimization of surface-initiated polymerization conditions.

Nanophosphor composite scintillators comprising a polymer matrix

DOEpatents

Muenchausen, Ross Edward; Mckigney, Edward Allen; Gilbertson, Robert David

2010-11-16

An improved nanophosphor composite comprises surface modified nanophosphor particles in a solid matrix. The nanophosphor particle surface is modified with an organic ligand, or by covalently bonding a polymeric or polymeric precursor material. The surface modified nanophosphor particle is essentially charge neutral, thereby preventing agglomeration of the nanophosphor particles during formation of the composite material. The improved nanophosphor composite may be used in any conventional scintillator application, including in a radiation detector.

Surface Functionalization Methods to Enhance Bioconjugation in Metal-Labeled Polystyrene Particles

PubMed Central

Abdelrahman, Ahmed I.; Thickett, Stuart C.; Liang, Yi; Ornatsky, Olga; Baranov, Vladimir; Winnik, Mitchell A.

2011-01-01

Lanthanide-encoded polystyrene particles synthesized by dispersion polymerization are excellent candidates for mass cytometry based immunoassays, however they have previously lacked the ability to conjugate biomolecules to the particle surface. We present here three approaches to post-functionalize these particles, enabling the covalent attachment of proteins. Our first approach used partially hydrolyzed poly(N-vinylpyrrolidone) as a dispersion polymerization stabilizer to synthesize particles with high concentration of -COOH groups on the particle surface. In an alternative strategy to provide -COOH functionality to the lanthanide-encoded particles, we employed seeded emulsion polymerization to graft poly(methacrylic acid) (PMAA) chains onto the surface of these particles. However, these two approaches gave little to no improvement in the extent of bioconjugation. In our third approach, seeded emulsion polymerization was subsequently used as a method to grow a functional polymer shell (in this case, poly(glycidyl methacrylate) (PGMA)) onto the surface of these particles, which proved highly successful. The epoxide-rich PGMA shell permitted extensive surface bioconjugation of NeutrAvidin, as probed by an Lu-labeled biotin reporter (ca. 7 × 105 binding events per particle with a very low amount of non-specific binding) and analyzed by mass cytometry. It was shown that coupling agents such as EDC were not needed, such was the reactivity of the particle surface. These particles were stable and the addition of a polymeric shell was shown did not affect the narrow lanthanide ion distribution within the particle interior as analyzed by mass cytometry. These particles represent the most promising candidates for the development of a highly multiplexed bioassay based on lanthanide-labeled particles to date. PMID:21799543

Coating and dispersion of ceramic nanoparticles by UV-ozone etching assisted surface-initiated living radical polymerization.

PubMed

Arita, Toshihiko

2010-10-01

Commercially available unmodified ceramic nanoparticles (NPs) in dry powder state were surface-modified and dispersed in almost single-crystal size. The surface-initiated living radical polymerization after just UV-ozone soft etching enables one to graft polymers onto the surface of ceramic NPs and disperse them in solvents. Furthermore, a number of NPs were dispersed with single-crystal sizes. The technique developed here could be applied to almost all ceramic NPs including metal nitrides.

Argon Ion Laser Polymerized Acrylic Resin: A Comparative Analysis of Mechanical Properties of Laser Cured, Light Cured and Heat Cured Denture Base Resins

PubMed Central

Murthy, S Srinivasa; Murthy, Gargi S

2015-01-01

Background: Dentistry in general and prosthodontics in particular is evolving at greater pace, but the denture base resins poly methyl methacrylate. There has been vast development in modifying chemically and the polymerization techniques for better manipulation and enhancement of mechanical properties. One such invention was introduction of visible light cure (VLC) denture base resin. Argon ion lasers have been used extensively in dentistry, studies has shown that it can polymerize restorative composite resins. Since composite resin and VLC resin share the same photo initiator, Argon laser is tested as activator for polymerizing VLC resin. In the Phase 1 study, the VLC resin was evaluated for exposure time for optimum polymerization using argon ion laser and in Phase 2; flexural strength, impact strength, surface hardness and surface characteristics of laser cured resin was compared with light cure and conventional heat cure resin. Materials and Methods: Phase 1; In compliance with American Dental Association (ADA) specification no. 12, 80 samples were prepared with 10 each for different curing time using argon laser and evaluated for flexural strength on three point bend test. Results were compared to established performance requirement specified. Phase 2, 10 specimen for each of the mechanical properties (30 specimen) were polymerized using laser, visible light and heat and compared. Surface and fractured surface of laser, light and heat cured resins were examined under scanning electron microscope (SEM). Results: In Phase 1, the specimen cured for 7, 8, 9 and 10 min fulfilled ADA requirement. 8 min was taken as suitable curing time for laser curing. Phase 2 the values of mechanical properties were computed and subjected to statistical analysis using one-way ANOVA and Tukey post-hoc test. The means of three independent groups showed significant differences between any two groups (P < 0.001). Conclusion: Triad VLC resin can be polymerized by argon ion laser with 1 W/mm2 power and exposure time of 8 min to satisfy ADA specification. Impact strength, surface hardness of laser cure was better than light cure and heat cure resin. Flexural strength of light cure was better than laser cure and heat cure resin. The SEM study showed similar density on surface, the fractured surface of heat cure resin was dense and compact. PMID:26124596

Pesticide mitigation strategies for surface water quality

USDA-ARS?s Scientific Manuscript database

Pesticide residues are being increasingly detected in surface water in agricultural and urban areas. In some cases water bodies are being listed under the Clean Water Act 303(d) as impaired and Total Maximum Daily Loads are required to address the impairments in agricultural areas. Pesticides in sur...

Glycine Polymerization on Oxide Minerals.

PubMed

Kitadai, Norio; Oonishi, Hiroyuki; Umemoto, Koichiro; Usui, Tomohiro; Fukushi, Keisuke; Nakashima, Satoru

2017-06-01

It has long been suggested that mineral surfaces played an important role in peptide bond formation on the primitive Earth. However, it remains unclear which mineral species was key to the prebiotic processes. This is because great discrepancies exist among the reported catalytic efficiencies of minerals for amino acid polymerizations, owing to mutually different experimental conditions. This study examined polymerization of glycine (Gly) on nine oxide minerals (amorphous silica, quartz, α-alumina and γ-alumina, anatase, rutile, hematite, magnetite, and forsterite) using identical preparation, heating, and analytical procedures. Results showed that a rutile surface is the most effective site for Gly polymerization in terms of both amounts and lengths of Gly polymers synthesized. The catalytic efficiency decreased as rutile > anatase > γ-alumina > forsterite > α- alumina > magnetite > hematite > quartz > amorphous silica. Based on reported molecular-level information for adsorption of Gly on these minerals, polymerization activation was inferred to have arisen from deprotonation of the NH 3 + group of adsorbed Gly to the nucleophilic NH 2 group, and from withdrawal of electron density from the carboxyl carbon to the surface metal ions. The orientation of adsorbed Gly on minerals is also a factor influencing the Gly reactivity. The examination of Gly-mineral interactions under identical experimental conditions has enabled the direct comparison of various minerals' catalytic efficiencies and has made discussion of polymerization mechanisms and their relative influences possible Further systematic investigations using the approach reported herein (which are expected to be fruitful) combined with future microscopic surface analyses will elucidate the role of minerals in the process of abiotic peptide bond formation.

Indirect latex glove contamination and its inhibitory effect on vinyl polysiloxane polymerization.

PubMed

Kimoto, Katsuhiko; Tanaka, Kinya; Toyoda, Minoru; Ochiai, Kent T

2005-05-01

The inhibitory effect of indirect latex contamination on the polymerization of vinyl polysiloxane (VPS) impression material has been previously reported. However, the transfer of specific elements that cause inhibition has not been confirmed, nor has the removal of such contaminants been reported. This study examined the surfaces of materials commonly used in restorative procedures that were contaminated by indirect latex glove contact and then evaluated for inhibition of polymerization of VPS. The effect of selected cleansing procedures was then studied. Four experimental groups (n = 8) were prepared: (1) clean vinyl gloves (control), (2) clean gingival retraction cords (control), (3) contaminated vinyl gloves, and (4) contaminated gingival retraction cord. Microscopic evaluation of the appearance and the characterization of surface particulate contamination were performed for each. Three cleansing protocols were then evaluated for efficacy in cleaning vinyl glove surfaces contaminated by latex contact (n = 10): (1) brushing with water, (2) brushing with soap/rinsing with water, (3) cleansing with rubbing alcohol. The subsequent degree of VPS polymerization inhibition was evaluated subjectively. A chi-square test was used for data analysis (alpha=.05). Particulate sulfur elements and sulfur-chloride compounds were present on the contaminated substrates. None of the 3 cleansing procedures eliminated polymerization inhibition (P =.33). Residual elemental sulfur remained on all tested surfaces. Particulate sulfur and sulfur-chloride compounds were identified as the particulate contamination that resulted in polymerization inhibition of the tested VPS dental impression material. Removal of these contaminants from the tested vinyl gloves and gingival retraction cord was not possible with the 3 cleansing protocols tested in this study.

Preparation of polymeric diacetylene thin films for nonlinear optical applications

NASA Technical Reports Server (NTRS)

Frazier, Donald O. (Inventor); Mcmanus, Samuel P. (Inventor); Paley, Mark S. (Inventor); Donovan, David N. (Inventor)

1995-01-01

A method for producing polymeric diacetylene thin films having desirable nonlinear optical characteristics has been achieved by producing amorphous diacetylene polymeric films by simultaneous polymerization of diacetylene monomers in solution and deposition of polymerized diacetylenes on to the surface of a transparent substrate through which ultraviolet light has been transmitted. These amorphous polydiacetylene films produced by photo-deposition from solution possess very high optical quality and exhibit large third order nonlinear optical susceptibilities, such properties being suitable for nonlinear optical devices such as waveguides and integrated optics.

Pore Structure and Fluoride Ion Adsorption Characteristics of Zr (IV) Surface-Immobilized Resin Prepared Using Polystyrene as a Porogen

NASA Astrophysics Data System (ADS)

Mizuki, Hidenobu; Ito, Yudai; Harada, Hisashi; Uezu, Kazuya

Zr(IV) surface-immobilized resins for removal of fluoride ion were prepared by surface template polymerization using polystyrene as a porogen. At polymerization, polystyrene was added in order to increase mesopores (2-50 nm) and macropore (>50 nm) with large macropores (around 300 nm) formed with internal aqueous phase of W⁄O emulsion. The pore structure of Zr(IV) surface-immobilized resins was evaluated by measuring specific surface area, pore volume, and pore size distribution with volumetric adsorption measurement instrument and mercury porosimeter. The adsorption isotherms were well fitted by Langmuir equation. The removal of fluoride was also carried out with column method. Zr(IV) surface-immobilized resins, using 10 g⁄L polystyrene in toluene at polymerization, possessed higher volume of not only mesopores and macropores but also large macropores. Furethermore, by adding the polystyrene with smaller molecular size, the pore volume of mesopores, macropores and large macropores was significantly increased, and the fluoride ion adsorption capacity and the column utilization also increased.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oyola-Reynoso, S.; Tevis, I. D.; Chen, J.

Here, chemical grafting has been widely used to modify the surface properties of materials, especially surface energy for controlled wetting, because of the resilience of such coatings/modifications. Reagents with multiple reactive sites have been used with the expectation that a monolayer will form. The step-growth polymerization mechanism, however, suggests the possibility of gel formation for hydrolyzable moieties in the presence of physisorbed water. In this report, we demonstrated that using alkyltrichlorosilanes (trivalent [i.e., 3 reactive sites]) in the surface modification of a cellulosic material (paper) does not yield a monolayer but rather gives surface-bound particles. We infer that the presencemore » of physisorbed (surface-bound) water allows for polymerization (or oligomerization) of the silane prior to its attachment on the surface. Surface energy mismatch between the hydrophobic tails of the growing polymer and any unreacted bound water leads to the assembly of the polymerizing material into spherical particles to minimize surface tension. By varying paper grammage (16.2–201.4 g m –2), we varied the accessible surface area and thus the amount of surface-adsorbed water, allowing us to control the ratio of the silane to the bound water. Using this approach, polymeric particles were formed on the surface of cellulose fibers ranging from ~70 nm to a film. The hydrophobicity of the surface, as determined by water contact angles, correlates with particle sizes (p < 0.001, Student's t-test), and, hence, the hydrophobicity can be tuned (contact angle between 94° and 149°). Using a model structure of a house, we demonstrated that as a result of this modification, paper-based houses can be rendered self-cleaning or tolerant to surface running water. In another application, we demonstrated that the felicitous choice of architectural design allows for the hydrophobic paper to be used for water harvesting.« less

Controlled grafting of comb copolymer brushes on poly(tetrafluoroethylene) films by surface-initiated living radical polymerizations.

PubMed

Yu, W H; Kang, E T; Neoh, K G

2005-01-04

Surface modification of poly(tetrafluoroethylene) (PTFE) films by well-defined comb copolymer brushes was carried out. Peroxide initiators were generated directly on the PTFE film surface via radio frequency Ar plasma pretreatment, followed by air exposure. Poly(glycidyl methacrylate) (PGMA) brushes were first prepared by surface-initiated reversible addition-fragmentation chain transfer polymerization from the peroxide initiators on the PTFE surface in the presence of a chain transfer agent. Kinetics study revealed a linear increase in the graft concentration of PGMA with the reaction time, indicating that the chain growth from the surface was consistent with a "controlled" or "living" process. alpha-Bromoester moieties were attached to the grafted PGMA by reaction of the epoxide groups with 2-bromo-2-methylpropionic acid. The comb copolymer brushes were subsequently prepared via surface-initiated atom transfer radical polymerization of two hydrophilic vinyl monomers, including poly(ethylene glycol) methyl ether methacrylate and sodium salt of 4-styrenesulfonic acid. The chemical composition of the modified PTFE surfaces was characterized by X-ray photoelectron spectroscopy.

Polymerization method for formation of thermally exfoliated graphite oxide containing polymer

NASA Technical Reports Server (NTRS)

Prud'Homme, Robert K. (Inventor); Aksay, Ilhan A. (Inventor); Adamson, Douglas (Inventor)

2010-01-01

A process for polymerization of at least one monomer including polymerizing the at least one monomer in the presence of a modified graphite oxide material, which is a thermally exfoliated graphite oxide with a surface area of from about 300 m(esp 2)/g to 2600 m(esp 2/g.

Surface engineering: molecularly imprinted affinity membranes by photograft polymerization

NASA Astrophysics Data System (ADS)

Matuschewski, Heike; Sergeyeva, Tatiana A.; Bendig, Juergen; Piletsky, Sergey A.; Ulbricht, Matthies; Schedler, Uwe

2001-02-01

Commercial polymer microfiltration membranes were surface-modified with a graft copolymer of a functional monomer and a crosslinker in the presence of a template (triazine-herbicide). As result, membranes covered with a thin layer of imprinted polymer (MIP) selective to the template were obtained. The influence of the polymerization conditions on membrane recognition properties was studied by membranes

Hepatitis B surface antigen and polymerized albumin binding activity in sheep serum.

PubMed Central

Franklin, S G; Millman, I; Blumberg, B S

1984-01-01

Sera from sheep and other domestic animals contain a substance that gives a strongly positive test for antibody to hepatitis B virus surface antigen by the accepted radioimmunoassay procedure. We have purified this substance from sheep serum to near homogeneity by ion-exchange, affinity, and molecular exclusion chromatography and have identified it to be an IgM. We present evidence that this sheep IgM is an antibody to polymerized sheep albumin. This antibody may arise due to infection by hepatitis B virus, hepatitis B virus-like viruses, or other pathological agents and may react with hepatitis B virus surface antigen by combining with polymerized albumin bound to the hepatitis B virus receptor for this polymer. Images PMID:6582511

Tailoring the surface properties of polypropylene films through cold atmospheric pressure plasma (CAPP) assisted polymerization and immobilization of biomolecules for enhancement of anti-coagulation activity

NASA Astrophysics Data System (ADS)

Navaneetha Pandiyaraj, K.; Ram Kumar, M. C.; Arun Kumar, A.; Padmanabhan, P. V. A.; Deshmukh, R. R.; Bah, M.; Ismat Shah, S.; Su, Pi-Guey; Halleluyah, M.; Halim, A. S.

2016-05-01

Enhancement of anti-thrombogenic properties of polypropylene (PP) to avert the adsorption of plasma proteins (fibrinogen and albumin), adhesion and activation of the platelets are very important for vast biomedical applications. The cold atmospheric pressure plasma (CAPP) assisted polymerization has potential to create the specific functional groups such as Osbnd Cdbnd O, Cdbnd O, Csbnd N and Ssbnd S. on the surface of polymeric films using selective precursor in vapour phase to enhance anti-thrombogenic properties. Such functionalized polymeric surfaces would be suitable for various biomedical applications especially to improve the blood compatibility. The eventual aspiration of the present investigation is to develop the biofunctional coating onto the surface of PP films using acrylic acid (AAc) and polyethylene glycol (PEG) as a precursor in a vapour phase by incorporating specific functional groups for immobilization of biomolecules such as heparin (HEP), chitosan (CHI) and insulin (INS) on the surface of plasma modified PP films. The surface properties such as hydrophilicity, chemical composition, surface topography of the surface modified PP films were analyzed by contact angle (CA), Fourier transform infrared spectroscopy (FTIR), X-ray photo electron spectroscopy (XPS) and atomic force microscopy (AFM). Furthermore the anti-thrombogenic properties of the surface modified PP films were studied by in vitro tests which include platelet adhesion and protein adsorption analysis. It was found that the anti-thrombogenic properties of the PP films are effectively controlled by the CAPP grafting of AAc and PEG followed by immobilization of biomolecules of heparin, chitosan and insulin. The grafting and immobilization was confirmed by FTIR and XPS through the recognition of specific functional groups such as COOH, Csbnd O, Ssbnd S and Csbnd N. on the surface of PP film. Furthermore, the surface morphology and hydrophilic nature of the PP films also tailored significantly by the successful grafting and immobilization which is confirmed by AFM and CA analysis. Owing to the physico-chemical changes on the surface of PP films induced by CAPP assisted polymerization, the anti-thrombogenic properties of PP films were enhanced as confirmed by in vitro analysis.

Surface patterning of polymeric separation membranes and its influence on the filtration performance

NASA Astrophysics Data System (ADS)

Maruf, Sajjad

Polymeric membrane based separation technologies are crucial for addressing the global issues such as water purification. However, continuous operations of these processes are often hindered by fouling which increases mass transport resistance of the membrane to permeation and thus the energy cost, and eventually replacement of the membrane in the system. In comparison to other anti-fouling strategies, the use of controlled surface topography to mitigate fouling has not been realized mainly due to the lack of methods to create targeted topography on the porous membrane surface. This thesis aims to develop a new methodology to create surface-patterned polymeric separation membrane to improve their anti-fouling characteristics during filtration. First, successful fabrication of sub-micron surface patterns directly on a commercial ultrafiltration (UF) membrane surface using nanoimprint lithographic (NIL) technique was demonstrated. Comprehensive filtration studies revealed that the presence of these sub-micron surface patterns mitigates not only the onset of colloidal particle deposition, but also lowers the rate of growth of cake layer after initial deposition, in comparison with un-patterned membranes. The anti-fouling effects were also observed for model protein solutions. Staged filtration experiments, with backwash cleaning, revealed that the permeate flux of the patterned membrane after protein fouling was considerably higher than that of the pristine or un-patterned membrane. In addition to the surface-patterning of UF membranes, successful fabrication of a surface-patterned thin film composite (TFC) membrane was shown for the first time. A two-step fabrication process was carried out by (1) nanoimprinting a polyethersulfone (PES) support using NIL, and (2) forming a thin dense film atop the PES support via interfacial polymerization (IP). Fouling experiments suggest that the surface patterns alter the hydrodynamics at the membrane-feed interface, which is effective in decreasing fouling in dead end filtration system. In summary, this thesis represents the first ever fabrication of functional patterned polymeric separation membrane and systematic investigation of the influence of submicron surface patterns on pressure-driven liquid membrane separations. The results presented here will enable an effective non-chemical surface modification anti-fouling strategy, which can be directly added onto current commercial separation membrane manufacturing route.

Polymeric Coatings for Combating Biocorrosion

NASA Astrophysics Data System (ADS)

Guo, Jing; Yuan, Shaojun; Jiang, Wei; Lv, Li; Liang, Bin; Pehkonen, Simo O.

2018-03-01

Biocorrosion has been considered as big trouble in many industries and marine environments due to causing great economic loss. The main disadvantages of present approaches to prevent corrosion include being limited by environmental factors, being expensive, inapplicable to field, and sometimes inefficient. Studies show that polymer coatings with anti-corrosion and anti-microbial properties have been widely accepted as a novel and effective approach to preventbiocorrosion. The main purpose of this review is to summarize up the progressive status of polymer coatings used for combating microbially-induced corrosion. Polymers used to synthesize protective coatings are generally divided into three categories: i) traditional polymers incorporated with biocides, ii) antibacterial polymers containing quaternary ammonium compounds, and iii) conductive polymers. The strategies to synthesize polymer coatings resort mainly to grafting anti-bacterial polymers from the metal substrate surface using novel surface-functionalization approaches, such as free radical polymerization, chemically oxidative polymerization and surface-initiated atom transfer radical polymerization, as opposed to the traditional approaches of dip coating or spin coating.

Preparation and Structural Studies on Hybrid Core-Shell Nanoparticles Consisting of Silica Core and Conjugated Block Copolymer Shell Prepared by Surface-Initiated Polymerization

NASA Astrophysics Data System (ADS)

Chatterjee, Sourav; Karam, Tony; Rosu, Cornelia; Li, Xin; Do, Changwoo; Youm, Sang Gil; Haber, Louis; Russo, Paul; Nesterov, Evgueni

Controlled Kumada catalyst-transfer polymerization occurring by chain-growth mechanism was developed for the synthesis of conjugated polymers and block copolymers from the surface of inorganic substrates such as silica nanoparticles. Although synthesis of conjugated polymers via Kumada polymerization became an established method for solution polymerization, carrying out the same reaction in heterogeneous conditions to form monodisperse polymer chains still remains a challenge. We developed and described a simple and efficient approach to the preparation of surface-immobilized layer of catalytic Ni(II) initiator, and demonstrated using it to prepare polymers and block copolymers on silica nanoparticle. The structure of the resulting hybrid nanostructures was thoroughly studied using small-angle neutron and X-ray scattering, thermal analysis, and optical spectroscopy. The photoexcitation energy transfer processes in the conjugated polymer shell were studied via steady-state and time resolved transient absorption spectroscopy. This study uncovered important details of the energy transfer, which will be discussed in this presentation.

Molecular Imprinting of Silica Nanoparticle Surfaces via Reversible Addition-Fragmentation Polymerization for Optical Biosensing Applications

NASA Astrophysics Data System (ADS)

Oluz, Zehra; Nayab, Sana; Kursun, Talya Tugana; Caykara, Tuncer; Yameen, Basit; Duran, Hatice

Azo initiator modified surface of silica nanoparticles were coated via reversible addition-fragmentation polymerization (RAFT) of methacrylic acid and ethylene glycol dimethacrylate using 2-phenylprop 2-yl dithobenzoate as chain transfer agent. Using L-phenylalanine anilide as template during polymerization led molecularly imprinted nanoparticles. RAFT polymerization offers an efficient control of grafting process, while molecularly imprinted polymers shows enhanced capacity as sensor. L-phenylalanine anilide imprinted silica particles were characterized by X-Ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM). Performances of the particles were followed by surface plasmon resonance spectroscopy (SPR) after coating the final product on gold deposited glass substrate against four different analogous of analyte molecules: D-henylalanine anilide, L-tyrosine, L-tryptophan and L-phenylalanine. Characterizations indicated that silica particles coated with polymer layer do contain binding sites for L-phenylalanine anilide, and are highly selective for the molecule of interest. This project was supported by TUBITAK (Project No:112M804).

Topical Ophthalmic Formulation of Trichostatin A and SurR9-C84A for Quick Recovery Post-alkali Burn of Corneal Haze

PubMed Central

Roy, Kislay; Cheung, Chun Hei Antonio; Kanwar, Rupinder K.; Sandhir, Rajat; Kanwar, Jagat R.

2017-01-01

Alkali burn injury is a true ocular emergency of the conjunctiva and cornea that requires immediate precision. Lack of an immediate therapy can lead to a substantial damage in the ocular surface and anterior segment further causing visual impairment and disfigurement. We explored the regenerative capability of dominant negative survivin protein (SurR9-C84A) and histone deacetylase inhibitor trichostatin-A (TSA) in vivo, in a rat alkali burn model. A topical insult in rat eyes with NaOH led to degradation of the conjunctival and corneal epithelium. The integrity of the conjunctival and corneal tissue was increased by TSA and SurR9-C84A by improving the clathrin and claudin expressions. Wound healing was initiated by an increase in TGF-beta-1 and, increased endogenous survivin which inhibited apoptosis post-TSA and SurR9-C84A treatments. Protein expressions of fibronectin and alpha-integrin 5 were found to increase promoting corneal integrity. The cytokine analysis confirmed increased expressions of IL-1beta, IL-6, IL-12, IL-13, IFN-gamma, TNF-alpha, GMCSF, Rantes, and MMP-2 in injured cornea, which were found to be significantly downregulated by the combined treatment of SurR9-C84A and TSA. The ocular and systemic pharmacokinetic (PK) parameters were measured post-topical ocular administration of TSA and SurR9-C84A. The SurR9-C84A and TSA sustained relatively longer in the cornea, conjunctiva, and aqueous humor than in the tear fluid and plasma. Our results confirmed that a combination of TSA with SurR9-C8A worked in synergy and showed a promising healing and anti-inflammatory effect in a very short time against alkali burn. Therefore, a combination of TSA and SurR9-C84A can fulfill the need for an immediate response to wound healing in alkali burnt cornea. We also synthesized ultra-small chitosan nanoparticles (USC-NPs) targeted with alpha-SMA antibodies that can be used for delivery of TSA and SurR9-C84A specifically to the ocular burn site. PMID:28529481

A Survey of Serious Aircraft Accidents Involving Fatigue Fracture. Volume 2. Rotary-Wing Aircraft (Etude sur des Accidents Importants d’Avions du aux Effets des Fractures de Fatigue. Volume 2. Effets sur des Helicopteres).

DTIC Science & Technology

1983-04-01

Convention on International Civil Aviation, Second Edition , March 1966. 5. WORLD AIRLINE ACCIDENT SUMMARY. Civil Aviation Authority, (Great Britain...people who either provided information, or who suggested other sources of information for the current edition of this survey. E.M.R. Alexander Civil...Waverley, New Zealand. F-28C Tail rotor drive shaft. Fatigue strength reduc- ed by softened condition & surface decarbur- isation. AISA 4130 steel. Ref: NZ

Evaluation of the validated soil moisture product from the SMAP radiometer

USDA-ARS?s Scientific Manuscript database

In this study, we used a multilinear regression approach to retrieve surface soil moisture from NASA’s Soil Moisture Active Passive (SMAP) satellite data to create a global dataset of surface soil moisture which is consistent with ESA’s Soil Moisture and Ocean Salinity (SMOS) satellite retrieved sur...

Effect of two types of latex gloves and surfactants on polymerization inhibition of three polyvinylsiloxane impression materials.

PubMed

Peregrina, Alejandro; Land, Martin F; Feil, Phillip; Price, Connie

2003-09-01

Polymerization inhibition of polyvinylsiloxane impression materials has been reported when in sustained contact with some types of latex gloves. This study examined the polymerization inhibition of 3 polyvinylsiloxane impression materials placed in contact with surfaces subjected to prior contact with gloves or commonly used surfactants. A 2 x 3 x 4 x 2 design was used (n = 20), with 2 types of gloves (powdered and unpowdered), 3 types of polyvinylsiloxane impression materials (Aquasil, Extrude, and Affinis), 4 surfactant conditions (water, soap/water-rinse, alcohol, and unexposed), and 2 ambient temperatures of 22 degrees C and 36 degrees C. After glove exposure to surfactants, a glass surface was subjected to rubbing contact with the treated glove for a standardized time. After drying, automixed polyvinylsiloxane impression materials were dispensed onto the treated surface. Specimens were removed and evaluated for polymerization inhibition at the manufacturer's recommended polymerization time (36 degrees C), or after 15 minutes at 22 degrees C. Specimens were rated as polymerized, or as inhibited if any polyvinylsiloxane residue remained on the slab. A chi-square analysis was used to evaluate the results (alpha=.05). Setting inhibition was found only with one of the polyvinylsiloxane materials when alcohol was used as a surfactant. At 22 degrees C, the inhibition rate ranged from 95% to 100% for both glove types; at 36 degrees C inhibition ranged from 40% (unpowdered gloves) to 75% (powdered gloves), respectively. Under these in vitro conditions, glove exposure to alcohol resulted in polymerization inhibition of 1 of 3 tested polyvinylsiloxane impression materials (Extrude).

Positron Annihilation Spectroscopy as a Novel Interfacial Probe for Thin Polymeric Films and Nano-Composites

NASA Astrophysics Data System (ADS)

Awad, Somia; Chen, Hongmin; Maina, Grace; Lee, L. James; Gu, Xiaohong; Jean, Y. C.

2010-03-01

Positron annihilation spectroscopy (PAS) has been developed as a novel probe to characterize the sub-nanometer defect, free volume, profile from the surface, interfaces, and to the bulk in polymeric materials when a variable mono-energy slow positron beam is used. Free-volume hole sizes, fractions, and distributions are measurable as a function of depth at the high precision. PAS has been successfully used to study the interfacial properties of polymeric nanocomposites at different chemical bonding. In nano-scale thin polymeric films, such as in PS/SiO2, and PU/ZnO, significant variations of Tg as a function of depth and of wt% oxide are observed. Variations of Tg are dependent on strong or weak interactions between polymers and nano-scale oxides surfaces.

Glucose Oxidase-Mediated Polymerization as a Platform for Dual-Mode Signal Amplification and Biodetection

PubMed Central

Berron, Brad J; Johnson, Leah M; Ba, Xiao; McCall, Joshua D; Alvey, Nicholas J; Anseth, Kristi S; Bowman, Christopher N

2011-01-01

We report the first use of a polymerization-based ELISA substrate solution employing enzymatically mediated radical polymerization as a dual-mode amplification strategy. Enzymes are selectively coupled to surfaces to generate radicals that subsequently lead to polymerization-based amplification (PBA) and biodetection. Sensitivity and amplification of the polymerization-based detection system were optimized in a microwell strip format using a biotinylated microwell surface with a glucose oxidase (GOx)–avidin conjugate. The immobilized GOx is used to initiate polymerization, enabling the detection of the biorecognition event visually or through the use of a plate reader. Assay response is compared to that of an enzymatic substrate utilizing nitroblue tetrazolium in a simplified assay using biotinylated wells. The polymerization substrate exhibits equivalent sensitivity (2 µg/mL of GOx-avidin) and over three times greater signal amplification than this traditional enzymatic substrate since each radical that is enzymatically generated leads to a large number of polymerization events. Enzyme-mediated polymerization proceeds in an ambient atmosphere without the need for external energy sources, which is an improvement upon previous PBA platforms. Substrate formulations are highly sensitive to both glucose and iron concentrations at the lowest enzyme concentrations. Increases in amplification time correspond to higher assay sensitivities with no increase in non-specific signal. Finally, the polymerization substrate generated a signal to noise ratio of 14 at the detection limit (156 ng/mL) in an assay of transforming growth factor-beta. Biotechnol. Bioeng. 2011; 108:1521–1528. © 2011 Wiley Periodicals, Inc. PMID:21337335

Evaluation of Polymerization Efficacy in Composite Resins via FT-IR Spectroscopy and Vickers Microhardness Test.

PubMed

Jafarzadeh, Tahereh-Sadat; Erfan, Mohammad; Behroozibakhsh, Marjan; Fatemi, Mostafa; Masaeli, Reza; Rezaei, Yashar; Bagheri, Hossein; Erfan, Yasaman

2015-01-01

Background and aims. Polymerization efficacy affects the properties and performance of composite resin restorations.The purpose of this study was to evaluate the effectiveness of polymerization of two micro-hybrid, two nano-hybrid and one nano-filled ormocer-based composite resins, cured by two different light-curing systems, using Fourier transformation infrared (FT-IR) spectroscopy and Vickers microhardness testing at two different depths (top surface, 2 mm). Materials and methods. For FT-IR spectrometry, five cylindrical specimens (5mm in diameter × 2 mm in length) were prepared from each composite resin using Teflon molds and polymerized for 20 seconds. Then, 70-μm wafers were sectioned at the top surface and at2mm from the top surface. The degree of conversion for each sample was calculated using FT-IR spectroscopy. For Vickers micro-hardness testing, three cylindrical specimens were prepared from each composite resin and polymerized for 20 seconds. The Vickers microhardness test (Shimadzu, Type M, Japan) was performed at the top and bottom (depth=2 mm) surfaces of each specimen. Three-way ANOVA with independent variables and Tukey tests were performed at 95% significance level. Results. No significant differences were detected in degree of conversion and microhardness between LED and QTH light-curing units except for the ormocer-based specimen, CeramX, which exhibited significantly higher DC by LED. All the composite resins showed a significantly higher degree of conversion at the surface. Microhardness was not significantly affected by depth, except for Herculite XRV Ultra and CeramX, which showed higher values at the surface. Conclusion. Composite resins containing nano-particles generally exhibited more variations in degree of conversion and microhardness.

Heparin-mimicking multilayer coating on polymeric membrane via LbL assembly of cyclodextrin-based supramolecules.

PubMed

Deng, Jie; Liu, Xinyue; Ma, Lang; Cheng, Chong; Shi, Wenbin; Nie, Chuanxiong; Zhao, Changsheng

2014-12-10

In this study, multifunctional and heparin-mimicking star-shaped supramolecules-deposited 3D porous multilayer films with improved biocompatibility were fabricated via a layer-by-layer (LbL) self-assembly method on polymeric membrane substrates. Star-shaped heparin-mimicking polyanions (including poly(styrenesulfonate-co-sodium acrylate; Star-PSS-AANa) and poly(styrenesulfonate-co-poly(ethylene glycol)methyl ether methacrylate; Star-PSS-EGMA)) and polycations (poly(methyl chloride-quaternized 2-(dimethylamino)ethyl methacrylate; Star-PMeDMA) were first synthesized by atom transfer radical polymerization (ATRP) from β-cyclodextrin (β-CD) based cores. Then assembly of 3D porous multilayers onto polymeric membrane surfaces was carried out by alternating deposition of the polyanions and polycations via electrostatic interaction. The surface morphology and composition, water contact angle, blood activation, and thrombotic potential as well as cell viability for the coated heparin-mimicking films were systematically investigated. The results of surface ATR-FTIR spectra and XPS spectra verified successful deposition of the star-shaped supramolecules onto the biomedical membrane surfaces; scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations revealed that the modified substrate had 3D porous surface morphology, which might have a great biological influence on the biointerface. Furthermore, systematic in vitro investigation of protein adsorption, platelet adhesion, human platelet factor 4 (PF4, indicates platelet activation), activate partial thromboplastin time (APTT), thrombin time (TT), coagulation activation (thrombin-antithrombin III complex (TAT, indicates blood coagulant)), and blood-related complement activation (C3a and C5a, indicates inflammation potential) confirmed that the heparin-mimicking multilayer coated membranes exhibited ultralow blood component activations and excellent hemocompatibility. Meanwhile, after surface coating, endothelial cell viability was also promoted, which indicated that the heparin-mimicking multilayer coating might extend the application fields of polymeric membranes in biomedical fields.

Evaluation of Polymerization Efficacy in Composite Resins via FT-IR Spectroscopy and Vickers Microhardness Test

PubMed Central

Jafarzadeh, Tahereh-Sadat; Erfan, Mohammad; Behroozibakhsh, Marjan; Fatemi, Mostafa; Masaeli, Reza; Rezaei, Yashar; Bagheri, Hossein; Erfan, Yasaman

2015-01-01

Background and aims. Polymerization efficacy affects the properties and performance of composite resin restorations.The purpose of this study was to evaluate the effectiveness of polymerization of two micro-hybrid, two nano-hybrid and one nano-filled ormocer-based composite resins, cured by two different light-curing systems, using Fourier transformation infrared (FT-IR) spectroscopy and Vickers microhardness testing at two different depths (top surface, 2 mm). Materials and methods. For FT-IR spectrometry, five cylindrical specimens (5mm in diameter × 2 mm in length) were prepared from each composite resin using Teflon molds and polymerized for 20 seconds. Then, 70-μm wafers were sectioned at the top surface and at2mm from the top surface. The degree of conversion for each sample was calculated using FT-IR spectroscopy. For Vickers micro-hardness testing, three cylindrical specimens were prepared from each composite resin and polymerized for 20 seconds. The Vickers microhardness test (Shimadzu, Type M, Japan) was performed at the top and bottom (depth=2 mm) surfaces of each specimen. Three-way ANOVA with independent variables and Tukey tests were performed at 95% significance level. Results. No significant differences were detected in degree of conversion and microhardness between LED and QTH light-curing units except for the ormocer-based specimen, CeramX, which exhibited significantly higher DC by LED. All the composite resins showed a significantly higher degree of conversion at the surface. Microhardness was not significantly affected by depth, except for Herculite XRV Ultra and CeramX, which showed higher values at the surface. Conclusion. Composite resins containing nano-particles generally exhibited more variations in degree of conversion and microhardness. PMID:26889359

Chemical Polymerization and Langmuir-Blodgett Techniques. 2. The Polymerization of Monolayers of 3-Substituted Pyrroles

DTIC Science & Technology

1993-09-12

the liquid -air interface could be monitored by changes in the surface area. Deposition of monolayers by Langmuir - Blodgett technique is possible and...polymerization product from the LB trough in chloroform solution. Figure 10 Langmuir - Blodgett transfer of poly (3-hexadecyl pyrrole) onto hydrophobized glass... Langmuir - Blodgett Techniques, 2: The Polymerization of Monolayers of 3-Substituted Pyrroles by W.M. Sigmund, C. Marestin, S. Keil, H. Zhou and R.S

Impact de la preparation des anodes crues et des conditions de cuisson sur la fissuration dans des anodes denses

NASA Astrophysics Data System (ADS)

Amrani, Salah

La fabrication de l'aluminium est realisee dans une cellule d'electrolyse, et cette operation utilise des anodes en carbone. L'evaluation de la qualite de ces anodes reste indispensable avant leur utilisation. La presence des fissures dans les anodes provoque une perturbation du procede l'electrolyse et une diminution de sa performance. Ce projet a ete entrepris pour determiner l'impact des differents parametres de procedes de fabrication des anodes sur la fissuration des anodes denses. Ces parametres incluent ceux de la fabrication des anodes crues, des proprietes des matieres premieres et de la cuisson. Une recherche bibliographique a ete effectuee sur tous les aspects de la fissuration des anodes en carbone pour compiler les travaux anterieurs. Une methodologie detaillee a ete mise au point pour faciliter le deroulement des travaux et atteindre les objectifs vises. La majorite de ce document est reservee pour la discussion des resultats obtenus au laboratoire de l'UQAC et au niveau industriel. Concernant les etudes realisees a l'UQAC, une partie des travaux experimentaux est reservee a la recherche des differents mecanismes de fissuration dans les anodes denses utilisees dans l'industrie d'aluminium. L'approche etait d'abord basee sur la caracterisation qualitative du mecanisme de la fissuration en surface et en profondeur. Puis, une caracterisation quantitative a ete realisee pour la determination de la distribution de la largeur de la fissure sur toute sa longueur, ainsi que le pourcentage de sa surface par rapport a la surface totale de l'echantillon. Cette etude a ete realisee par le biais de la technique d'analyse d'image utilisee pour caracteriser la fissuration d'un echantillon d'anode cuite. L'analyse surfacique et en profondeur de cet echantillon a permis de voir clairement la formation des fissures sur une grande partie de la surface analysee. L'autre partie des travaux est basee sur la caracterisation des defauts dans des echantillons d'anodes crues fabriquees industriellement. Cette technique a consiste a determiner le profil des differentes proprietes physiques. En effet, la methode basee sur la mesure de la distribution de la resistivite electrique sur la totalite de l'echantillon est la technique qui a ete utilisee pour localiser la fissuration et les macro-pores. La microscopie optique et l'analyse d'image ont, quant a elles, permis de caracteriser les zones fissurees tout en determinant la structure des echantillons analyses a l'echelle microscopique. D'autres tests ont ete menes, et ils ont consiste a etudier des echantillons cylindriques d'anodes de 50 mm de diametre et de 130 mm de longueur. Ces derniers ont ete cuits dans un four a UQAC a differents taux de chauffage dans le but de pouvoir determiner l'influence des parametres de cuisson sur la formation de la fissuration dans ce genre de carottes. La caracterisation des echantillons d'anodes cuites a ete faite a l'aide de la microscopie electronique a balayage et de l'ultrason. La derniere partie des travaux realises a l'UQAC contient une etude sur la caracterisation des anodes fabriquees au laboratoire sous differentes conditions d'operation. L'evolution de la qualite de ces anodes a ete faite par l'utilisation de plusieurs techniques. L'evolution de la temperature de refroidissement des anodes crues de laboratoire a ete mesuree; et un modele mathematique a ete developpe et valide avec les donnees experimentales. Cela a pour objectif d'estimer la vitesse de refroidissement ainsi que le stress thermique. Toutes les anodes fabriquees ont ete caracterisees avant la cuisson par la determination de certaines proprietes physiques (resistivite electrique, densite apparente, densite optique et pourcentage de defauts). La tomographie et la distribution de la resistivite electrique, qui sont des techniques non destructives, ont ete employees pour evaluer les defauts internes des anodes. Pendant la cuisson des anodes de laboratoire, l'evolution de la resistivite electrique a ete suivie et l'etape de devolatilisation a ete identifiee. Certaines anodes ont ete cuites a differents taux de chauffage (bas, moyen, eleve et un autre combine) dans l'objectif de trouver les meilleures conditions de cuisson en vue de minimiser la fissuration. D'autres anodes ont ete cuites a differents niveaux de cuisson, cela dans le but d'identifier a quelle etape de l'operation de cuisson la fissuration commence a se developper. Apres la cuisson, les anodes ont ete recuperees pour, a nouveau, faire leur caracterisation par les memes techniques utilisees precedemment. L'objectif principal de cette partie etait de reveler l'impact de differents parametres sur le probleme de fissuration, qui sont repartis sur toute la chaine de production des anodes. Le pourcentage de megots, la quantite de brai et la distribution des particules sont des facteurs importants a considerer pour etudier l'effet de la matiere premiere sur le probleme de la fissuration. Concernant l'effet des parametres du procede de fabrication sur le meme probleme, le temps de vibration, la pression de compaction et le procede de refroidissement ont ete a la base de cette etude. Finalement, l'influence de la phase de cuisson sur l'apparition de la fissuration a ete prise en consideration par l'intermediaire du taux de chauffage et du niveau de cuisson. Les travaux realises au niveau industriel ont ete faits lors d'une campagne de mesure dans le but d'evaluer la qualite des anodes de carbone en general et l'investigation du probleme de fissuration en particulier. Ensuite, il s'agissait de reveler les effets de differents parametres sur le probleme de la fissuration. Vingt-quatre anodes cuites ont ete utilisees. Elles ont ete fabriquees avec differentes matieres premieres (brai, coke, megots) et sous diverses conditions (pression, temps de vibration). Le parametre de la densite de fissuration a ete calcule en se basant sur l'inspection visuelle de la fissuration des carottes. Cela permet de classifier les differentes fissurations en plusieurs categories en se basant sur certains criteres tels que le type de fissures (horizontale, verticale et inclinee), leurs localisations longitudinales (bas, milieu et haut de l'anode) et transversales (gauche, centrale et droite). Les effets de la matiere premiere, les parametres de fabrication des anodes crues ainsi que les conditions de cuisson sur la fissuration ont ete etudies. La fissuration des anodes denses en carbones cause un serieux probleme pour l'industrie d'aluminium primaire. La realisation de ce projet a permis la revelation de differents mecanismes de fissuration, la classification de fissuration par plusieurs criteres (position, types localisation) et l'evaluation de l'impact de differents parametres sur la fissuration. Les etudes effectuees dans le domaine de cuisson ont donne la possibilite d'ameliorer l'operation et reduire la fissuration des anodes. Le travail consiste aussi a identifier des techniques capables d'evaluer la qualite d'anodes (l'ultrason, la tomographie et la distribution de la resistivite electrique). La fissuration des anodes en carbone est consideree comme un probleme complexe, car son apparition depend de plusieurs parametres repartis sur toute la chaine de production. Dans ce projet, plusieurs nouvelles etudes ont ete realisees, et elles permettent de donner de l'originalite aux travaux de recherches faits dans le domaine de la fissuration des anodes de carbone pour l'industrie de l'aluminium primaire. Les etudes realisees dans ce projet permettent d'ajouter d'un cote, une valeur scientifique pour mieux comprendre le probleme de fissuration des anodes et d'un autre cote, d'essayer de proposer des methodes qui peuvent reduire ce probleme a l'echelle industrielle.

Effect of surface treatment methods on the shear bond strength of auto-polymerized resin to thermoplastic denture base polymer.

PubMed

Koodaryan, Roodabeh; Hafezeqoran, Ali

2016-12-01

Polyamide polymers do not provide sufficient bond strength to auto-polymerized resins for repairing fractured denture or replacing dislodged denture teeth. Limited treatment methods have been developed to improve the bond strength between auto-polymerized reline resins and polyamide denture base materials. The objective of the present study was to evaluate the effect of surface modification by acetic acid on surface characteristics and bond strength of reline resin to polyamide denture base. 84 polyamide specimens were divided into three surface treatment groups (n=28): control (N), silica-coated (S), and acid-treated (A). Two different auto-polymerized reline resins GC and Triplex resins were bonded to the samples (subgroups T and G, respectively, n=14). The specimens were subjected to shear bond strength test after they were stored in distilled water for 1 week and thermo-cycled for 5000 cycles. Data were analyzed with independent t-test, two-way analysis of variance (ANOVA), and Tukey's post hoc multiple comparison test (α=.05). The bond strength values of A and S were significantly higher than those of N ( P <.001 for both). However, statistically significant difference was not observed between group A and group S. According to the independent Student's t-test, the shear bond strength values of AT were significantly higher than those of AG ( P <.001). The surface treatment of polyamide denture base materials with acetic acid may be an efficient and cost-effective method for increasing the shear bond strength to auto-polymerized reline resin.

Thiol surface functionalization via continuous phase plasma polymerization of allyl mercaptan, with subsequent maleimide-linked conjugation of collagen.

PubMed

Stynes, Gil D; Gengenbach, Thomas R; Kiroff, George K; Morrison, Wayne A; Kirkland, Mark A

2017-07-01

Thiol groups can undergo a large variety of chemical reactions and are used in solution phase to conjugate many bioactive molecules. Previous research on solid substrates with continuous phase glow discharge polymerization of thiol-containing monomers may have been compromised by oxidation. Thiol surface functionalization via glow discharge polymerization has been reported as requiring pulsing. Herein, continuous phase glow discharge polymerization of allyl mercaptan (2-propene-1-thiol) was used to generate significant densities of thiol groups on a mixed macrodiol polyurethane and tantalum. Three general classes of chemistry are used to conjugate proteins to thiol groups, with maleimide linkers being used most commonly. Here the pH specificity of maleimide reactions was used effectively to conjugate surface-bound thiol groups to amine groups in collagen. XPS demonstrated surface-bound thiol groups without evidence of oxidation, along with the subsequent presence of maleimide and collagen. Glow discharge reactor parameters were optimized by testing the resistance of bound collagen to degradation by 8 M urea. The nature of the chemical bonding of collagen to surface thiol groups was effectively assessed by colorimetric assay (ELISA) of residual collagen after incubation in 8 M urea over 8 days and after incubation with keratinocytes over 15 days. The facile creation of useable solid-supported thiol groups via continuous phase glow discharge polymerization of allyl mercaptan opens a route for attaching a vast array of bioactive molecules. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1940-1948, 2017. © 2017 Wiley Periodicals, Inc.

Synthesis of soybean oil-based polymeric surfactants in supercritical carbon dioxide and investigation of their surface properties

USDA-ARS?s Scientific Manuscript database

This paper reports the preparation of polymeric surfactants (HPSO) via a two-step synthetic procedure: polymerization of soybean oil (PSO) in supercritical carbon dioxide and followed by hydrolysis of PSO with a base. HPSO was characterized and identified by using a combination of FTIR, 1H NMR, 13C...

The formation of the smallest fullerene-like carbon cages on metal surfaces.

PubMed

Ben Romdhane, F; Rodríguez-Manzo, J A; Andrieux-Ledier, A; Fossard, F; Hallal, A; Magaud, L; Coraux, J; Loiseau, A; Banhart, F

2016-02-07

The nucleation and growth of carbon on catalytically active metal surfaces is one of the most important techniques to produce nanomaterials such as graphene or nanotubes. Here it is shown by in situ electron microscopy that fullerene-like spherical clusters with diameters down to 0.4 nm and thus much smaller than C60 grow in a polymerized state on Co, Fe, or Ru surfaces. The cages appear on the surface of metallic islands in contact with graphene under heating to at least 650 °C and successively cooling to less than 500 °C. The formation of the small cages is explained by the segregation of carbon on a supersaturated metal, driven by kinetics. First principles energy calculations show that the clusters polymerize and can be attached to defects in graphene. Under compression, the polymerized cages appear in a crystalline structure.

Method for nanoencapsulation of aerogels and nanoencapsulated aerogels produced by such method

NASA Technical Reports Server (NTRS)

Sullivan, Thomas A. (Inventor)

2007-01-01

A method for increasing the compressive modulus of aerogels comprising: providing aerogel substrate comprising a bubble matrix in a chamber; providing monomer to the chamber, the monomer comprising vapor phase monomer which polymerizes substantially free of polymerization byproducts; depositing monomer from the vapor phase onto the surface of the aerogel substrate under deposition conditions effective to produce a vapor pressure sufficient to cause the vapor phase monomer to penetrate into the bubble matrix and deposit onto the surface of the aerogel substrate, producing a substantially uniform monomer film; and, polymerizing the substantially uniform monomer film under polymerization conditions effective to produce polymer coated aerogel comprising a substantially uniform polymer coating substantially free of polymerization byproducts.Polymer coated aerogel comprising aerogel substrate comprising a substantially uniform polymer coating, said polymer coated aerogel comprising porosity and having a compressive modulus greater than the compressive modulus of the aerogel substrate, as measured by a 100 lb. load cell at 1 mm/minute in the linear range of 20% to 40% compression.

Surface water retardation around single-chain polymeric nanoparticles: critical for catalytic function?

PubMed

Stals, Patrick J M; Cheng, Chi-Yuan; van Beek, Lotte; Wauters, Annelies C; Palmans, Anja R A; Han, Songi; Meijer, E W

2016-03-01

A library of water-soluble dynamic single-chain polymeric nanoparticles (SCPN) was prepared using a controlled radical polymerisation technique followed by the introduction of functional groups, including probes at targeted positions. The combined tools of electron paramagnetic resonance (EPR) and Overhauser dynamic nuclear polarization (ODNP) reveal that these SCPNs have structural and surface hydration properties resembling that of enzymes.

Tribochemical synthesis of nano-lubricant films from adsorbed molecules at sliding solid interface: Tribo-polymers from α-pinene, pinane, and n-decane

NASA Astrophysics Data System (ADS)

He, Xin; Barthel, Anthony J.; Kim, Seong H.

2016-06-01

The mechanochemical reactions of adsorbed molecules at sliding interfaces were studied for α-pinene (C10H16), pinane (C10H18), and n-decane (C10H22) on a stainless steel substrate surface. During vapor phase lubrication, molecules adsorbed at the sliding interface could be activated by mechanical shear. Under the equilibrium adsorption condition of these molecules, the friction coefficient of sliding steel surfaces was about 0.2 and a polymeric film was tribochemically produced. The synthesis yield of α-pinene tribo-polymers was about twice as much as pinane tribo-polymers. In contrast to these strained bicyclic hydrocarbons, n-decane showed much weaker activity for tribo-polymerization at the same mechanical shear condition. These results suggested that the mechanical shear at tribological interfaces could induce the opening of the strained ring structure of α-pinene and pinane, which leads to polymerization of adsorbed molecules at the sliding track. On a stainless steel surface, such polymerization reactions of adsorbed molecules do not occur under typical surface reaction conditions. The mechanical properties and boundary lubrication efficiency of the produced tribo-polymer films are discussed.

A biomolecule friendly photolithographic process for fabrication of protein microarrays on polymeric films coated on silicon chips.

PubMed

Petrou, Panagiota S; Chatzichristidi, Margarita; Douvas, Antonios M; Argitis, Panagiotis; Misiakos, Konstantinos; Kakabakos, Sotirios E

2007-04-15

The last years, there is a steadily growing demand for methods and materials appropriate to create patterns of biomolecules for bioanalytical applications. Here, a photolithographic method for patterning biomolecules onto a silicon surface coated with a polymeric layer of high protein binding capacity is presented. The patterning process does not affect the polymeric film and the activity of the immobilized onto the surface biomolecules. Therefore, it permits sequential immobilization of different biomolecules on spatially distinct areas on the same solid support. The polymeric layer is based on a commercially available photoresist (AZ5214) that is cured at high temperature in order to provide a stable substrate for creation of protein microarrays by the developed photolithographic process. The photolithographic material consists of a (meth)acrylate copolymer and a sulfonium salt as a photoacid generator, and it is lithographically processed by thermal treatment at temperatures

Biomimetic PEGylation of carbon nanotubes through surface-initiated RAFT polymerization.

PubMed

Shi, Yingge; Zeng, Guanjian; Xu, Dazhuang; Liu, Meiying; Wang, Ke; Li, Zhen; Fu, Lihua; Zhang, Qingsong; Zhang, Xiaoyong; Wei, Yen

2017-11-01

Carbon nanotubes (CNTs) are a type of one-dimensional carbon nanomaterials that possess excellent physicochemical properties and have been potentially utilized for a variety of applications. Surface modification of CNTs with polymers is a general route to expand and improve the performance of CNTs and has attracted great research interest over the past few decades. Although many methods have been developed previously, most of these methods still showed some disadvantages, such as low efficiency, complex experimental procedure and harsh reaction conditions etc. In this work, we reported a practical and novel way to fabricate CNTs based polymer composites via the combination of mussel inspired chemistry and reversible addition fragmentation chain transfer (RAFT) polymerization. First, the amino group was introduced onto the surface of CNTs via self-polymerization of dopamine. Then, chain transfer agent can be immobilized on the amino groups functionalized CNTs to obtain CNT-PDA-CTA, which can be utilized for surface-initiated RAFT polymerization. A water soluble and biocompatible monomer poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) was adopted to fabricate pPEGMA functionalized CNTs through RAFT polymerization. The successful preparation of CNTs based polymer composites (CNT-pPEGMA) was confirmed by transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy in details. The CNT-pPEGMA showed good dispersibility and desirable biocompatibility, making them highly potential for biomedical applications. More importantly, a large number of CNTs based polymer composites could also be fabricated through the same strategy when different monomers were used due to the good monomer adaptability of RAFT polymerization. Therefore, this strategy should be a general method for preparation of various multifunctional CNTs based polymer composites. Copyright © 2017 Elsevier B.V. All rights reserved.

Mechanism of in situ surface polymerization of gallic acid in an environmental-inspired preparation of carboxylated core-shell magnetite nanoparticles.

PubMed

Tóth, Ildikó Y; Szekeres, Márta; Turcu, Rodica; Sáringer, Szilárd; Illés, Erzsébet; Nesztor, Dániel; Tombácz, Etelka

2014-12-30

Magnetite nanoparticles (MNPs) with biocompatible coatings are good candidates for MRI (magnetic resonance imaging) contrasting, magnetic hyperthermia treatments, and drug delivery systems. The spontaneous surface induced polymerization of dissolved organic matter on environmental mineral particles inspired us to prepare carboxylated core-shell MNPs by using a ubiquitous polyphenolic precursor. Through the adsorption and in situ surface polymerization of gallic acid (GA), a polygallate (PGA) coating is formed on the nanoparticles (PGA@MNP) with possible antioxidant capacity. The present work explores the mechanism of polymerization with the help of potentiometric acid-base titration, dynamic light scattering (for particle size and zeta potential determination), UV-vis (UV-visible light spectroscopy), FTIR-ATR (Fourier-transformed infrared spectroscopy by attenuated total reflection), and XPS (X-ray photoelectron spectroscopy) techniques. We observed the formation of ester and ether linkages between gallate monomers both in solution and in the adsorbed state. Higher polymers were formed in the course of several weeks both on the surface of nanoparticles and in the dispersion medium. The ratio of the absorbances of PGA supernatants at 400 and 600 nm (i.e., the E4/E6 ratio commonly used to characterize the degree of polymerization of humic materials) was determined to be 4.3, similar to that of humic acids. Combined XPS, dynamic light scattering, and FTIR-ATR results revealed that, prior to polymerization, the GA monomers became oxidized to poly(carboxylic acid)s due to ring opening while Fe(3+) ions reduced to Fe(2+). Our published results on the colloidal and chemical stability of PGA@MNPs are referenced thoroughly in the present work. Detailed studies on biocompatibility, antioxidant property, and biomedical applicability of the particles will be published.

Polyethylene Oxide Films Polymerized by Radio Frequency Plasma-Enhanced Chemical Vapour Phase Deposition and Its Adsorption Behaviour of Platelet-Rich Plasma

NASA Astrophysics Data System (ADS)

Hu, Wen-Juan; Xie, Fen-Yan; Chen, Qiang; Weng, Jing

2008-10-01

We present polyethylene oxide (PEO) functional films polymerized by rf plasma-enhanced vapour chemical deposition (rf-PECVD) on p-Si (100) surface with precursor ethylene glycol dimethyl ether (EGDME) and diluted Ar in pulsed plasma mode. The influences of discharge parameters on the film properties and compounds are investigated. The film structure is analysed by Fourier transform infrared (FTIR) spectroscopy. The water contact angle measurement and atomic force microscope (AFM) are employed to examine the surface polarity and to detect surface morphology, respectively. It is concluded that the smaller duty cycle in pulsed plasma mode contributes to the rich C-O-C (EO) group on the surfaces. As an application, the adsorption behaviour of platelet-rich plasma on plasma polymerization films performed in-vitro is explored. The shapes of attached cells are studied in detail by an optic invert microscope, which clarifies that high-density C-O-C groups on surfaces are responsible for non-fouling adsorption behaviour of the PEO films.

Antimicrobial and Antifouling Polymeric Agents for Surface Functionalization of Medical Implants.

PubMed

Zeng, Qiang; Zhu, Yiwen; Yu, Bingran; Sun, Yujie; Ding, Xiaokang; Xu, Chen; Wu, Yu-Wei; Tang, Zhihui; Xu, Fu-Jian

2018-05-09

Combating implant-associated infections is an urgent demand due to the increasing numbers in surgical operations such as joint replacements and dental implantations. Surface functionalization of implantable medical devices with polymeric antimicrobial and antifouling agents is an efficient strategy to prevent bacterial fouling and associated infections. In this work, antimicrobial and antifouling branched polymeric agents (GPEG and GEG) were synthesized via ring-opening reaction involving gentamicin and ethylene glycol species. Due to their rich primary amine groups, they can be readily coated on the polydopamine-modified implant (such as titanium) surfaces. The resultant surface coatings of Ti-GPEG and Ti-GEG produce excellent in vitro antibacterial efficacy toward both Staphylococcus aureus and Escherichia coli, while Ti-GPEG exhibit better antifouling ability. Moreover, the infection model with S. aureus shows that implanted Ti-GPEG possessed excellent antibacterial and antifouling ability in vivo. This study would provide a promising strategy for the surface functionalization of implantable medical devices to prevent implant-associated infections.

Effect of radiation light characteristics on surface hardness of paint-on resin for shade modification.

PubMed

Arikawa, Hiroyuki; Kanie, Takahito; Fujii, Koichi; Ban, Seiji

2005-12-01

The purpose of this study was to investigate the effect of radiation light characteristics--of different types of clinical light-curing unit--on polymerization efficiency, as determined by the surface hardness of light-cured paint-on resins. Four shades of paint-on resin for shade modification of restorative resins were used. Materials were cured using one laboratory and three clinical light-curing units with different light sources, namely tungsten-halogen, LED, plasma arc, and xenon flash lamps. Knoop hardness measurements were taken at both the top and bottom surfaces of the specimens to assess the mechanical properties and degree of polymerization. Both LED and plasma arc light units caused significantly poorer surface hardness than the halogen and laboratory xenon lights. In addition, the transparent shade was more sensitive to surface hardness than other chromatic shades. Our results indicated that the polymerization efficiency of paint-on resin was significantly influenced by the radiation light characteristics of clinical light-curing units.

A short review of radiation-induced raft-mediated graft copolymerization: A powerful combination for modifying the surface properties of polymers in a controlled manner

NASA Astrophysics Data System (ADS)

Barsbay, Murat; Güven, Olgun

2009-12-01

Surface grafting of polymeric materials is attracting increasing attention as it enables the preparation of new materials from known and commercially available polymers having desirable bulk properties such as thermal stability, elasticity, permeability, etc., in conjunction with advantageous newly tailored surface properties such as biocompatibility, biomimicry, adhesion, etc. Ionizing radiation, particularly γ radiation is one of the most powerful tools for preparing graft copolymers as it generates radicals on most substrates. With the advent of living free-radical polymerization techniques, application of γ radiation has been extended to a new era of grafting; grafting in a controlled manner to achieve surfaces with tailored and well-defined properties. This report presents the current use of γ radiation in living free-radical polymerization and highlights the use of both techniques together as a combination to present an advance in the ability to prepare surfaces with desired, tunable and well-defined properties.

Pharmacological Correction of Trafficking Defects in ATP-sensitive Potassium Channels Caused by Sulfonylurea Receptor 1 Mutations*

PubMed Central

Martin, Gregory M.; Rex, Emily A.; Devaraneni, Prasanna; Denton, Jerod S.; Boodhansingh, Kara E.; DeLeon, Diva D.; Stanley, Charles A.; Shyng, Show-Ling

2016-01-01

ATP-sensitive potassium (KATP) channels play a key role in mediating glucose-stimulated insulin secretion by coupling metabolic signals to β-cell membrane potential. Loss of KATP channel function due to mutations in ABCC8 or KCNJ11, genes encoding the sulfonylurea receptor 1 (SUR1) or the inwardly rectifying potassium channel Kir6.2, respectively, results in congenital hyperinsulinism. Many SUR1 mutations prevent trafficking of channel proteins from the endoplasmic reticulum to the cell surface. Channel inhibitors, including sulfonylureas and carbamazepine, have been shown to correct channel trafficking defects. In the present study, we identified 13 novel SUR1 mutations that cause channel trafficking defects, the majority of which are amenable to pharmacological rescue by glibenclamide and carbamazepine. By contrast, none of the mutant channels were rescued by KATP channel openers. Cross-linking experiments showed that KATP channel inhibitors promoted interactions between the N terminus of Kir6.2 and SUR1, whereas channel openers did not, suggesting the inhibitors enhance intersubunit interactions to overcome channel biogenesis and trafficking defects. Functional studies of rescued mutant channels indicate that most mutants rescued to the cell surface exhibited WT-like sensitivity to ATP, MgADP, and diazoxide. In intact cells, recovery of channel function upon trafficking rescue by reversible sulfonylureas or carbamazepine was facilitated by the KATP channel opener diazoxide. Our study expands the list of KATP channel trafficking mutations whose function can be recovered by pharmacological ligands and provides further insight into the structural mechanism by which channel inhibitors correct channel biogenesis and trafficking defects. PMID:27573238

Effect of polyvinyl siloxane impression material on the polymerization of composite resin.

PubMed

Chen, Liang; Kleverlaan, Cornelis Johannes; Liang, Kunneng; Yang, Deqin

2017-04-01

Polyvinyl siloxane impression material has been widely used as a lingual matrix for rebuilding missing tooth structure with composite resin. The composite resin is light polymerized in contact with the polyvinyl siloxane impression material. However, polyvinyl siloxane impression material has been shown to interact with other dental materials. The purpose of this study was to assess the effect of polyvinyl siloxane impression materials on the polymerization of composite resins by assessing the Vickers microhardness and degree of conversion of polyvinyl siloxane. The composite resins were light polymerized in contact with 3 polyvinyl siloxane impression materials (Flexitime Easy Putty; President Light Body; Xantopren L Blue) (n=8) and in contact with a matrix strip as the control group (n=8). Vickers microhardness and degree of conversion on contact surfaces were measured to evaluate the polymerization of composite resins. The depth of the effect was assessed by Vickers microhardness on section surfaces and observed with scanning electron microscopy. The results were analyzed by 1-way analysis of variance and the post hoc Tukey honest significant differences test (α=.05). The Vickers microhardness and degree of conversion values on the contact surfaces of the experiment groups were significantly lower than those of the control group (P<.05); the Vickers microhardness values on the section surfaces indicated that there was no significant difference at the same depth of different groups (P>.05). The scanning electron microscope observation showed that an approximately 10-μm deep unpolymerized layer was found in the experimental group. Polyvinyl siloxane impression materials have an inhibitory effect on the polymerization of the composite resins, but just limited to within approximately 10 μm from the surface in contact with the impression material. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Antibacterial Drug Releasing Materials by Post-Polymerization Surface Modification

NASA Astrophysics Data System (ADS)

Chng, Shuyun; Moloney, Mark G.; Wu, Linda Y. L.

Functional materials are available by the post-polymerization surface modification of diverse polymers in a three-step process mediated, firstly, by carbene insertion chemistry, secondly, by diazonium coupling, and thirdly by modification with a remotely tethered spiropyran unit, and these materials may be used for the reversible binding and release of Penicillin V. Surface loading densities of up to 0.19mmol/g polymer are achievable, leading to materials with higher loading densities and release behavior relative to unmodified controls, and observable antibacterial biocidal activity.

Glucose-sensitive QCM-sensors via direct surface RAFT polymerization.

PubMed

Sugnaux, Caroline; Klok, H-A

2014-08-01

Thin, phenylboronic acid-containing polymer coatings are potentially attractive sensory layers for a range of glucose monitoring systems. This contribution presents the synthesis and properties of glucose-sensitive polymer brushes obtained via surface RAFT polymerization of 3-methacrylamido phenylboronic acid (MAPBA). This synthetic strategy is attractive since it allows the controlled growth of PMAPBA brushes with film thicknesses of up to 20 nm via direct polymerization of MAPBA without the need for additional post-polymerization modification or deprotection steps. QCM-D sensor chips modified with a PMAPBA layer respond with a linear change in the shift of the fundamental resonance frequency over a range of physiologically relevant glucose concentrations and are insensitive toward the presence of fructose, thus validating the potential of these polymer brush films as glucose sensory thin coatings. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Conductivity enhancement of surface-polymerized polyaniline films via control of processing conditions

NASA Astrophysics Data System (ADS)

Park, Chung Hyoi; Jang, Sung Kyu; Kim, Felix Sunjoo

2018-01-01

We investigate a fast and facile approach for the simultaneous synthesis and coating of conducting polyaniline (PANI) onto a substrate and the effects of processing conditions on the electrical properties of the fabricated films. Simultaneous polymerizing and depositing on the substrate forms a thin film with the average thickness of 300 nm and sheet resistance of 304 Ω/sq. Deposition conditions such as polymerization time (3-240 min), temperature (-10 to 40 °C), concentrations of monomer and oxidant (0.1-0.9 M), and type of washing solvents (acetone, water, and/or HCl solution) affect the film thickness, doping state, absorption characteristics, and solid-state nanoscale morphology, therefore affecting the electrical conductivity. Among the conditions, the surface-polymerized PANI film deposited at room temperature with acetone washing showed the highest conductivity of 22.2 S/cm.

Characterization of III-V materials by optical interferometry

NASA Astrophysics Data System (ADS)

Montgomery, P. C.; Vabre, P.; Montaner, D.; Fillard, J. P.

1993-09-01

Digital interference microscopy is a new measuring technique with submicron horizontal resolution and nanometric vertical resolution, that can be used for the three-dimensional analysis of surface defects and device features in many microelectronics applications on bulk materials and epitaxial layers. In this paper we show how certain defects can be analysed on III-V materials and devices using two different interferometric techniques. The choice of the technique depends on the height and the slope of the surface features to be measured. We show that small defects less than λ/2 in height, or surfaces with shallow continuous slopes upto one or two microns high are best profiled with the phase stepping technique (PSM) because of the high vertical resolution of 1 nm and the higher speed and precision. This is illustrated by studies of the surface polish of InP wafers, defects after chemical etching of tin doped InP, defects on an epitaxial layer of GaAs on InP and quantum dot structures on GaAs. For measuring devices which contain mesas and grooves with step heights greater than λ/2, the peak fringe scanning (PFSM) method is the better choice. The vertical resolution is slightly less (4 nm), but the vertical range is higher (upto 15 μm) as demonstrated with the measurement of an etched groove in a laser/detector device on a quaternary layer on InP, and a MESFET device on GaAs. Compared with electron microscopy and the new near field scanning techniques, digital interference microscopy has the advantages of ease of use and speed of analysis and being able to resolve certain problems that are difficult or not possible by other means, such as profiling deep narrow etched grooves, or measuring the relief of a surface hidden under a transparent layer. The main disadvantages are that the horizontal resolution is limited to the resolving power of the objective and that errors due to variations in the optical properties of the sample need to be taken into account. La microscopie interférentielle numérique est une nouvelle méthode de mesure qui a une résolution latérale micronique et une résolution verticale nanométrique. Ceci est utile pour l'analyse tri-dimensionnelle des défauts de surface et de la forme des composants dans beaucoup d'applications sur les matériaux massifs et épitaxiés. Dans cet article nous démontrons comment certains défauts peuvent être analysés sur les matériaux et les composants III-V avec deux méthodes interférométriques différentes. La microscopie à saut de phase est mieux adaptée, avec sa résolution de 1 nm et sa meilleure précision, à la mesure des petits défauts de moins de λ/2 en hauteur, ou des surfaces avec des pentes douces et continues, jusqu'à une altitude de 1 ou 2 μm. Ceci est illustré par les études du polissage de plaquettes d'InP, des défauts sur une couche épitaxiée de GaAs sur InP et des boîtes quantiques sur GaAs. Pour mesurer les motifs, les mésas et les sillons qui ont des marches de plus que λ/2, la microscopie à glissement de franges est le meilleur choix. La résolution verticale est un peu moins bonne que celle de la PSM (4 nm) mais la dynamique verticale est plus grande (15 μm). Ceci est démontré par les mesures d'un sillon gravé dans une structure laser/détecteur sur une couche quaternaire sur InP et d'un MESFET sur GaAs. En comparaison avec la microscopie électronique et les méthodes de champ proche, la microscopie interférentielle numérique a les avantages de la facilité d'utilisation et de la rapidité. Elle est également capable de résoudre certains problèmes difficiles ou insolubles avec les autres techniques, comme par exemple le profil des sillons étroits, ou la mesure des reliefs enterrés sous une couche transparente. Les inconvénients sont la résolution latérale qui est limitée au pouvoir résolutif de l'objectif et l'introduction d'erreurs liées aux variations des propriétés optiques de l'échantillon qui doivent être prises en compte.

Defining an optimal surface chemistry for pluripotent stem cell culture in 2D and 3D

NASA Astrophysics Data System (ADS)

Zonca, Michael R., Jr.

Surface chemistry is critical for growing pluripotent stem cells in an undifferentiated state. There is great potential to engineer the surface chemistry at the nanoscale level to regulate stem cell adhesion. However, the challenge is to identify the optimal surface chemistry of the substrata for ES cell attachment and maintenance. Using a high-throughput polymerization and screening platform, a chemically defined, synthetic polymer grafted coating that supports strong attachment and high expansion capacity of pluripotent stem cells has been discovered using mouse embryonic stem (ES) cells as a model system. This optimal substrate, N-[3-(Dimethylamino)propyl] methacrylamide (DMAPMA) that is grafted on 2D synthetic poly(ether sulfone) (PES) membrane, sustains the self-renewal of ES cells (up to 7 passages). DMAPMA supports cell attachment of ES cells through integrin beta1 in a RGD-independent manner and is similar to another recently reported polymer surface. Next, DMAPMA has been able to be transferred to 3D by grafting to synthetic, polymeric, PES fibrous matrices through both photo-induced and plasma-induced polymerization. These 3D modified fibers exhibited higher cell proliferation and greater expression of pluripotency markers of mouse ES cells than 2D PES membranes. Our results indicated that desirable surfaces in 2D can be scaled to 3D and that both surface chemistry and structural dimension strongly influence the growth and differentiation of pluripotent stem cells. Lastly, the feasibility of incorporating DMAPMA into a widely used natural polymer, alginate, has been tested. Novel adhesive alginate hydrogels have been successfully synthesized by either direct polymerization of DMAPMA and methacrylic acid blended with alginate, or photo-induced DMAPMA polymerization on alginate nanofibrous hydrogels. In particular, DMAPMA-coated alginate hydrogels support strong ES cell attachment, exhibiting a concentration dependency of DMAPMA. This research provides a new avenue for stem cell culture and maintenance using an optimal organic-based chemistry.

Kinetics of successive seeding of monodisperse polystyrene latexes. I - Initiation via potassium persulfate. II - Azo initiators with and without inhibitors

NASA Technical Reports Server (NTRS)

Sudol, E. D.; El-Aasser, M. S.; Vanderhoff, J. W.

1986-01-01

The polymerization kinetics of monodisperse polystyrene latexes with diameters of 1 micron are studied. The monodisperse latexes were prepared by the successive seeding method using 1 mM K2S2O8 with an 8 percent emulsifier surface coverage and 0.5 mM K2S2O8 with a 4 percent emulsifier surface coverage, and the kinetics were measured in a piston/cylinder dialometer. The data reveal that the polymerization rate decreases with increasing particle size; and the surface charge decreases with increasing particle size. The effects of initiators (AIBN and AMBN) and inhibitors (NH24SCN, NaNO2, and hydroquinone) on the product monodispersity and polymerization kinetics of latexes with diameters greater than 1 micron are investigated in a second experiment. It is observed that hydroquinone combined with AMBN are most effective in reducing nucleation without causing flocculation. It is noted that the kinetic transition from emulsion to bulk is complete for a particle size exceeding 1 micron in which the polymerization rate is independent of the particle size.

Surface Effect Ship Structural Producibility. Part 2.

DTIC Science & Technology

1980-05-14

the compressive stresses on the sur - face of the peened joint areas. A coimmon occurrence on welds made from one side against removable back- ing was...polished to remove any scratches or nicks; the plate and weld reinforcement sur - faces were left In the as-received condition. Strain gages were in- fstalled...67I 4 - ES - ’ - 0 < - - - __3 f TT --- ’-~ 131 T:41 -1- I--nI I 44 6,A -- 7:- 00 0 cu at to ___- 106-- *-’-- 7 <-I I S9HS__NKN: B-68 7 AD-A la ?7 437

Methodologie de modelisation aerostructurelle d'une aile utilisant un logiciel de calcul aerodynamique et un logiciel de calcul par elements finis =

NASA Astrophysics Data System (ADS)

Communier, David

Lors de l'etude structurelle d'une aile d'avion, il est difficile de modeliser fidelement les forces aerodynamiques subies par l'aile de l'avion. Pour faciliter l'analyse, on repartit la portance maximale theorique de l'aile sur son longeron principal ou sur ses nervures. La repartition utilisee implique que l'aile entiere sera plus resistante que necessaire et donc que la structure ne sera pas totalement optimisee. Pour pallier ce probleme, il faudrait s'assurer d'appliquer une repartition aerodynamique de la portance sur la surface complete de l'aile. On serait donc en mesure d'obtenir une repartition des charges sur l'aile beaucoup plus fiable. Pour le realiser, nous aurons besoin de coupler les resultats d'un logiciel calculant les charges aerodynamiques de l'aile avec les resultats d'un logiciel permettant sa conception et son analyse structurelle. Dans ce projet, le logiciel utilise pour calculer les coefficients de pression sur l'aile est XFLR5 et le logiciel permettant la conception et l'analyse structurelle sera CATIA V5. Le logiciel XFLR5 permet une analyse rapide d'une aile en se basant sur l'analyse de ses profils. Ce logiciel calcule les performances des profils de la meme maniere que XFOIL et permet de choisir parmi trois methodes de calcul pour obtenir les performances de l'aile : Lifting Line Theory (LLT), Vortex Lattice Method (VLM) et 3D Panels. Dans notre methodologie, nous utilisons la methode de calcul 3D Panels dont la validite a ete testee en soufflerie pour confirmer les calculs sur XFLR5. En ce qui concerne la conception et l'analyse par des elements finis de la structure, le logiciel CATIA V5 est couramment utilise dans le domaine aerospatial. CATIA V5 permet une automatisation des etapes de conception de l'aile. Ainsi, dans ce memoire, nous allons decrire la methodologie permettant l'etude aerostructurelle d'une aile d'avion.

Fabrication of luminescent hydroxyapatite nanorods through surface-initiated RAFT polymerization: Characterization, biological imaging and drug delivery applications

NASA Astrophysics Data System (ADS)

Heng, Chunning; Zheng, Xiaoyan; Liu, Meiying; Xu, Dazhuang; Huang, Hongye; Deng, Fengjie; Hui, Junfeng; Zhang, Xiaoyong; Wei, Yen

2016-11-01

Hydroxyapatite nanomaterials as an important class of nanomaterials, have been widely applied for different biomedical applications for their excellent biocompatibility, biodegradation potential and low cost. In this work, hydroxyapatite nanorods with uniform size and morphology were prepared through hydrothermal synthesis. The surfaces of these hydroxyapatite nanorods are covered with hydrophobic oleic acid, making them poor dispersibility in aqueous solution and difficult for biomedical applications. To overcome this issue, a simple surface initiated polymerization strategy has been developed via combination of the surface ligand exchange and reversible addition fragmentation chain transfer (RAFT) polymerization. Hydroxyapatite nanorods were first modified with Riboflavin-5-phosphate sodium (RPSSD) via ligand exchange reaction between the phosphate group of RPSSD and oleic acid. Then hydroxyl group of nHAp-RPSSD was used to immobilize chain transfer agent, which was used as the initiator for surface-initiated RAFT polymerization. The nHAp-RPSSD-poly(IA-PEGMA) nanocomposites were characterized by means of 1H nuclear magnetic resonance, Fourier transform infrared spectroscopy, fluorescence spectroscopy and thermal gravimetric analysis in detailed. The biocompatibility, biological imaging and drug delivery of nHAp-RPSSD-poly(IA-PEGMA) were also investigated. Results showed that nHAp-RPSSD-poly(IA-PEGMA) exhibited excellent water dispersibility, desirable optical properties, good biocompatibility and high drug loading capability, making them promising candidates for biological imaging and controlled drug delivery applications.

Comparative study on the development of intestinal mucin 2, IgA and polymeric Ig receptor expressions between broiler chickens and Pekin ducks

USDA-ARS?s Scientific Manuscript database

Intestinal mucin2 (MUC2), a major gel-forming mucin, represents a primary barrier component of mucus layers and target site for secretory IgA. Polymeric Ig receptor (pIgR) expressed on the basolateral surface of epithelium, is used to transport polymeric IgA from the lamina propria into luminal muci...

Surface-Initiated Polymerization with Poly(n-hexylisocyanate) to Covalently Functionalize Silica Nanoparticles.

PubMed

Vatansever, Fatma; Hamblin, Michael R

2017-02-01

New methods are needed for covalent functionalization of nanoparticles-surface with organic polymer coronas to generate polymeric nanocomposite in a controlled manner. Here we report the use of a surface-initiated polymerization approach, mediated by titanium (IV) catalysis, to grow poly( n -hexylisocyanate) chains from silica surface. Two pathways were used to generate the interfacing in these nano-hybrids. In the first one, the nanoparticles was "seeded" with SiCl4, followed by reaction with 1,6-hexanediol to form hydroxyl groups attached directly to the surface via O-Si-O bonding. In the second pathway, the nanoparticles were initially exposed to a 9:1 mixture of trimethyl silyl chloride and chlorodimethyl octenyl silane which was then followed by hydroboration of the double bonds, to afford hydroxyl groups with a spatially controlled density and surface-attachment via O-Si-C bonding. These functionalized surfaces were then activated with the titanium tetrachloride catalyst. In our approach, thus surface tethered catalyst provided the sites for n -hexyl isocyanate monomer insertion, to "build up" the surface-grown polymer layers from the "bottom-up". A final end-capping, to seal off the chain ends, was done via acetyl chloride. Compounds were characterized by FT-IR, 1H-NMR, GC-MS, GPC, and thermogravimetric analyses.

Surface-Initiated Polymerization with Poly(n-hexylisocyanate) to Covalently Functionalize Silica Nanoparticles

PubMed Central

Vatansever, Fatma; Hamblin, Michael R.

2017-01-01

New methods are needed for covalent functionalization of nanoparticles-surface with organic polymer coronas to generate polymeric nanocomposite in a controlled manner. Here we report the use of a surface-initiated polymerization approach, mediated by titanium (IV) catalysis, to grow poly(n-hexylisocyanate) chains from silica surface. Two pathways were used to generate the interfacing in these nano-hybrids. In the first one, the nanoparticles was “seeded” with SiCl4, followed by reaction with 1,6-hexanediol to form hydroxyl groups attached directly to the surface via O-Si-O bonding. In the second pathway, the nanoparticles were initially exposed to a 9:1 mixture of trimethyl silyl chloride and chlorodimethyl octenyl silane which was then followed by hydroboration of the double bonds, to afford hydroxyl groups with a spatially controlled density and surface-attachment via O-Si-C bonding. These functionalized surfaces were then activated with the titanium tetrachloride catalyst. In our approach, thus surface tethered catalyst provided the sites for n-hexyl isocyanate monomer insertion, to “build up” the surface-grown polymer layers from the “bottom-up”. A final end-capping, to seal off the chain ends, was done via acetyl chloride. Compounds were characterized by FT-IR, 1H-NMR, GC-MS, GPC, and thermogravimetric analyses. PMID:28989336

The effects of non-ionic polymeric surfactants on the cleaning of biofouled hydrogel materials.

PubMed

Guan, Allan; Li, Zhenyu; Phillips, K Scott

2015-01-01

Block co-polymer surfactants have been used for cleaning hydrogel medical devices that contact the body (e.g., contact lenses) because of their biocompatibility. This work examined the relationship between concentration and detergency of two non-ionic polymeric surfactants (Pluronic F127 and Triton X-100) for cleaning protein soil, with anionic surfactants (sodium dodecyl sulfate and sodium laureth sulfate) as positive controls. Surface plasmon resonance was used to quantify removal of simulated tear soil from self-assembled monolayer surfaces, and a microplate format was used to study the removal of fluorescently labeled soil proteins from contact lenses. While detergency increased as a function of concentration for anionic surfactants, it decreased with concentration for the two polymeric surfactants. The fact that the protein detergency of some non-ionic polymeric surfactants did not increase with concentration above the critical micelle concentration could have implications for optimizing the tradeoff between detergency and biocompatibility.

Radar response to crop residue cover and tillage application on postharvest agricultural surfaces

NASA Astrophysics Data System (ADS)

McNairn, Heather

Les informations sur les pratiques de conservation des sols comme le labourage et la gestion des residus de culture sont requises afin d'estimer avec exactitude les risques d'erosion des sols. Quoique les micro-ondes soient sensibles aux conditions d'humidite et aux proprietes geometriques des surfaces, il n'en demeure pas moins que l'on connait encore peu sur la sensibilite des micro-ondes polarisees lineaires ou des parametres polarimetriques du ROS en fonction des caracteristiques des residus. A partir de donnees prises a l'aide d'un diffusometre monte sur un camion en 1996 et lors d'une mission SIR-C menee en 1994, cette recherche a demontre que les micro-ondes sont sensibles a la fois a la quantite et au type de couverture de residus, de meme qu'a la teneur en eau des residus. La reponse des polarisations croisees lineaires et de plusieurs parametres polarimetriques, incluant la hauteur pedestre, a permis d'observer qu'une diffusion volumique importante avait lieu en presence de vegetation senescente qui se tenait debout et pour les champs non laboures. La diffusion de surface dominait cependant pour les champs avec de faibles quantites de residus et des residus plus fins. La recherche a toutefois demontre que des conditions de surface complexes etaient crees par differentes combinaisons de residus et de pratiques de labourage. Par consequent, il faudra attendre que des donnees multi-polarisees ou polarimetriques soient acquises par les capteurs prevus a bord du satellite canadien RADARSAT-2 et du satellite ENVISAT de l'Agence spatiale europeenne avant de pouvoir completement caracteriser les champs apres la recolte.

Assessment of surface hardness of acrylic resins submitted to accelerated artificial aging.

PubMed

Tornavoi, D C; Agnelli, J A M; Lepri, C P; Mazzetto, M O; Botelho, A L; Soares, R G; Dos Reis, A C

2012-06-01

The aim of this study was to assess the influence of accelerated artificial aging (AAA) on the surface hardness of acrylic resins. The following three commercial brands of acrylic resins were tested: Vipi Flash (autopolymerized resin), Vipi Wave (microwave heat-polymerized resin) and Vipi Cril (conventional heat-polymerized resin). To perform the tests, 21 test specimens (65x10x3 mm) were made, 7 for each resin. Three surface hardness readings were performed for each test specimen, before and after AAA, and the means were submitted to the following tests: Kolmogorov-Smirnov (P>0.05), Levene Statistic, Two-way ANOVA, Tukey Post Hoc (P<0.05) with the SPSS Statistical Software 17.0. The analysis of the factors showed significant differences in the hardness values (P<0.05). Before aging, the autopolymerized acrylic resin Vipi Flash showed lower hardness values when compared with the heat-polymerized resin Vipi Cril (P=0.001). After aging, the 3 materials showed similar performance when compared among them. The Vipi Cril was the only one affected by AAA and showed lower hardness values after this procedure (Pp=0.003). It may be concluded that accelerated artificial aging influenced surface hardness of heat-polymerized acrylic resin Vipi Cril.

Preparation, characterization, and surface conductivity of nanocomposites with hollow graphitic carbon nanospheres as fillers in polymethylmethacrylate matrix

NASA Astrophysics Data System (ADS)

Zhang, Cheng; Gao, Qingshan; Zhou, Bing; Bhargava, Gaurang

2017-08-01

Hollow graphitized carbon nanosphere (CNS) materials with inner diameter of 20 to 50 nm and shell thickness of 10 15 nm were synthesized from the polymerization of resorcinol (R) and formaldehyde (F) in the presence of a well-characterized iron polymeric complex (IPC). The CNS with unique nanostructures was used to fabricate CNS-polymer composites by dispersing CNS as fillers in the polymer matrix. Aggregation of CNS in polymer composites is usually a challenging issue. In this work, we employed in situ polymerization method and melt-mixing method to fabricate CNS-polymethylmethacrylate (PMMA) composites and compared their difference in terms of CNS dispersion in the composites and surface electrical conductivity. Four probes technique was utilized to measure the surface electrical conductivity of the CNS-PMMA composites. The measurements on four points and four silver painted lines on the thin film of CNS-PMMA composites were compared. The in situ polymerization method was found more efficient for better CNS dispersion in PMMA matrix and lower percolation conductivity threshold compared to the melt-mixing method. The enhanced electrical conductivity for CNS-PMMA composites may be attributed to the stronger covalent CNS-PMMA bonding between the surface functional groups and the MMA moieties.

In Situ Investigation of Electrochemically Mediated Surface-Initiated Atom Transfer Radical Polymerization by Electrochemical Surface Plasmon Resonance.

PubMed

Chen, Daqun; Hu, Weihua

2017-04-18

Electrochemically mediated atom transfer radical polymerization (eATRP) initiates/controls the controlled/living ATRP chain propagation process by electrochemically generating (regenerating) the activator (lower-oxidation-state metal complex) from deactivator (higher-oxidation-state metal complex). Despite successful demonstrations in both of the homogeneous polymerization and heterogeneous systems (namely, surface-initiated ATRP, SI-ATRP), the eATRP process itself has never been in situ investigated, and important information regarding this process remains unrevealed. In this work, we report the first investigation of the electrochemically mediated SI-ATRP (eSI-ATRP) by rationally combining the electrochemical technique with real-time surface plasmon resonance (SPR). In the experiment, the potential of a SPR gold chip modified by the self-assembled monolayer of the ATRP initiator was controlled to electrochemically reduce the deactivator to activator to initiate the SI-ATRP, and the whole process was simultaneously monitored by SPR with a high time resolution of 0.1 s. It is found that it is feasible to electrochemically trigger/control the SI-ATRP and the polymerization rate is correlated to the potential applied to the gold chip. This work reveals important kinetic information for eSI-ATRP and offers a powerful platform for in situ investigation of such complicated processes.

Guided in Situ Polymerization of MEH-PPV in Mesoporous Titania Photoanodes.

PubMed

Minar, Norma K; Docampo, Pablo; Fattakhova-Rohlfing, Dina; Bein, Thomas

2015-05-20

Incorporation of conjugated polymers into porous metal oxide networks is a challenging task, which is being pursued via many different approaches. We have developed the guided in situ polymerization of poly(2-methoxy-5-(2'-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV) in porous titania films by means of surface functionalization. The controlled polymerization via the Gilch route was induced by an alkoxide base and by increasing the temperature. The selected and specially designed surface-functionalizing linker molecules mimic the monomer or its activated form, respectively. In this way, we drastically enhanced the amount of MEH-PPV incorporated into the porous titania phase compared to nonfunctionalized samples by a factor of 6. Additionally, photovoltaic measurements were performed. The devices show shunting or series resistance limitations, depending on the surface functionalization prior to in situ polymerization of MEH-PPV. We suggest that the reason for this behavior can be found in the orientation of the grown polymer chains with respect to the titania surface. Therefore, the geometry of the anchoring via the linker molecules is relevant for exploiting the full electronic potential of the conjugated polymer in the resulting hybrid composite. This observation will help to design future synthesis methods for new hybrid materials from conjugated polymers and n-type semiconductors to take full advantage of favorable electronic interactions between the two phases.

Surface plasmon resonance sensor for antibiotics detection based on photo-initiated polymerization molecularly imprinted array.

PubMed

Luo, Qiaohui; Yu, Neng; Shi, Chunfei; Wang, Xiaoping; Wu, Jianmin

2016-12-01

A surface plasmon resonance (SPR) sensor combined with nanoscale molecularly imprinted polymer (MIP) film as recognition element was developed for selective detection of the antibiotic ciprofloxacin (CIP). The MIP film on SPR sensor chip was prepared by in situ photo-initiated polymerization method which has the advantages of short polymerization time, controllable thickness and good uniformity. The surface wettability and thickness of MIP film on SPR sensor chip were characterized by static contact angle measurement and stylus profiler. The MIP-SPR sensor exhibited high selectivity, sensitivity and good stability for ciprofloxacin. The imprinting factors of the MIP-SPR sensor to ciprofloxacin and its structural analogue ofloxacin were 2.63 and 3.80, which is much higher than those to azithromycin, dopamine and penicillin. The SPR response had good linear relation with CIP concentration over the range 10 -11 -10 -7 molL -1 . The MIP-SPR sensor also showed good repeatability and stability during cyclic detections. On the basis of the photo-initiated polymerization method, a surface plasmon resonance imaging (SPRi) chip modified with three types of MIP sensing spots was fabricated. The MIPs-SPRi sensor shows different response patterns to ciprofloxacin and azithromycin, revealing the ability to recognize different antibiotic molecules. Copyright © 2016 Elsevier B.V. All rights reserved.

Polymeric Micelles as Novel Carriers for Poorly Soluble Drugs--A Review.

PubMed

Reddy, B Pavan Kumar; Yadav, Hemant K S; Nagesha, Dattatri K; Raizaday, Abhay; Karim, Abdul

2015-06-01

Polymeric micelles are used as 'smart drug carriers' for targeting certain areas of the body by making them stimuli-sensitive or by attachment of a specific ligand molecule onto their surface. The main aim of using polymeric micelles is to deliver the poorly water soluble drugs. Now-a-days they are used especially in the areas of cancer therapy also. In this article we have reviewed several aspects of polymeric micelles concerning their mechanism of formation, chemical nature, preparation and characterization techniques, and their applications in the areas of drug delivery.

ATRP-based synthesis and characterization of light-responsive coatings for transdermal delivery systems

PubMed Central

Pauly, Anja C; Schöller, Katrin; Baumann, Lukas; Rossi, René M; Dustmann, Kathrin; Ziener, Ulrich; de Courten, Damien; Wolf, Martin; Boesel, Luciano F; Scherer, Lukas J

2015-01-01

The grafting of poly(hydroxyethylmethacrylate) on polymeric porous membranes via atom transfer radical polymerization (ATRP) and subsequent modification with a photo-responsive spiropyran derivative is described. This method leads to photo-responsive membranes with desirable properties such as light-controlled permeability changes, exceptional photo-stability and repeatability of the photo-responsive switching. Conventional track etched polyester membranes were first treated with plasma polymer coating introducing anchoring groups, which allowed the attachment of ATRP-initiator molecules on the membrane surface. Surface initiated ARGET–ATRP of hydroxyethylmethacrylate (where ARGET stands for activator regenerated by electron transfer) leads to a membrane covered with a polymer layer, whereas the controlled polymerization procedure allows good control over the thickness of the polymer layer in respect to the polymerization conditions. Therefore, the final permeability of the membranes could be tailored by choice of pore diameter of the initial membranes, applied monomer concentration or polymerization time. Moreover a remarkable switch in permeability (more than 1000%) upon irradiation with UV-light could be achieved. These properties enable possible applications in the field of transdermal drug delivery, filtration, or sensing. PMID:27877791

ATRP-based synthesis and characterization of light-responsive coatings for transdermal delivery systems

NASA Astrophysics Data System (ADS)

Pauly, Anja C.; Schöller, Katrin; Baumann, Lukas; Rossi, René M.; Dustmann, Kathrin; Ziener, Ulrich; de Courten, Damien; Wolf, Martin; Boesel, Luciano F.; Scherer, Lukas J.

2015-06-01

The grafting of poly(hydroxyethylmethacrylate) on polymeric porous membranes via atom transfer radical polymerization (ATRP) and subsequent modification with a photo-responsive spiropyran derivative is described. This method leads to photo-responsive membranes with desirable properties such as light-controlled permeability changes, exceptional photo-stability and repeatability of the photo-responsive switching. Conventional track etched polyester membranes were first treated with plasma polymer coating introducing anchoring groups, which allowed the attachment of ATRP-initiator molecules on the membrane surface. Surface initiated ARGET-ATRP of hydroxyethylmethacrylate (where ARGET stands for activator regenerated by electron transfer) leads to a membrane covered with a polymer layer, whereas the controlled polymerization procedure allows good control over the thickness of the polymer layer in respect to the polymerization conditions. Therefore, the final permeability of the membranes could be tailored by choice of pore diameter of the initial membranes, applied monomer concentration or polymerization time. Moreover a remarkable switch in permeability (more than 1000%) upon irradiation with UV-light could be achieved. These properties enable possible applications in the field of transdermal drug delivery, filtration, or sensing.

Differential natural organic matter fouling of ceramic versus polymeric ultrafiltration membranes.

PubMed

Lee, Seung-Jin; Kim, Jae-Hong

2014-01-01

Ceramic ultrafiltration membranes has drawn increasing attention in drinking water treatment sectors as an alternative to traditional polymeric counterparts, yet only limited information has been made available about the characteristics of ceramic membrane fouling by natural organic matter. The effects of solution chemistry including ionic strength, divalent ion concentration and pH on the flux behavior were comparatively evaluated for ceramic and polymeric ultrafiltration of synthetic water containing model natural organic matter. Filtration characteristics were further probed via resistance-in-series model analysis, fouling visualization using quantum dots, batch adsorption test, contact angle measurement, solute-membrane surface adhesion force measurement, and quantitative comparison of fouling characteristics between ceramic and polymeric membranes. The results collectively suggested that the effects of solution chemistry on fouling behavior of ceramic membranes were generally similar to polymeric counterparts in terms of trends, while the extent varied significantly depending on water quality parameters. Lower fouling tendency and enhanced cleaning efficiency were observed with the ceramic membrane, further promoting the potential for ceramic membrane application to surface water treatment. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effect of Hardness, Surface Finish and Grain Size on Rolling Contact Fatigue Life of M50 Bearing Steel

DTIC Science & Technology

1958-01-01

the surface-finish range desired, differ- cessary in order to establish optimum conditions ent grades of grinding wheels were used on the cen- for...FATIGUEHESULTS 05 MT O AT VARIO0 QRIAIN U- ZES HABLESSES , AND SURFACE INISHE.. TEbT BEOLTJ OF 010 LOBE IN DE1CEtDIh, (’D,6 Hard- Gr-in Sur(...(e Wiebull Ha

Construction of Hierarchical Polymer Brushes on Upconversion Nanoparticles via NIR-Light-Initiated RAFT Polymerization.

PubMed

Xie, Zhongxi; Deng, Xiaoran; Liu, Bei; Huang, Shanshan; Ma, Pingan; Hou, Zhiyao; Cheng, Ziyong; Lin, Jun; Luan, Shifang

2017-09-13

Photoinduced reversible addition-fragmentation chain transfer (RAFT) polymerization generally adopts high-energy ultraviolet (UV) or blue light. In combination with photoredox catalyst, the excitation light wavelength was extended to the visible and even near-infrared (NIR) region for photoinduced electron transfer RAFT polymerization. In this report, we introduce for the first time a surface NIR-light-initiated RAFT polymerization on upconversion nanoparticles (UCNPs) without adding any photocatalyst and construct a functional inorganic core/polymer shell nanohybrid for application in cancer theranostics. The multilayer core-shell UCNPs (NaYF 4 :Yb/Tm@NaYbF 4 :Gd@NaNdF 4 :Yb@NaYF 4 ), with surface anchorings of chain transfer agents, can serve as efficient NIR-to-UV light transducers for initiating the RAFT polymerization. A hierarchical double block copolymer brush, consisting of poly(acrylic acid) (PAA) and poly(oligo(ethylene oxide)methacrylate-co-2-(2-methoxy-ethoxy)ethyl methacrylate) (PEG for short), was grafted from the surface in sequence. The targeting arginine-glycine-aspartic (RGD) peptide was modified at the end of the copolymer through the trithiolcarbonate end group. After loading of doxorubicin, the UCNPs@PAA-b-PEG-RGD exhibited an enhanced U87MG cancer cell uptake efficiency and cytotoxicity. Besides, the unique upconversion luminescence of the nanohybrids was used for the autofluoresence-free cell imaging and labeling. Therefore, our strategy verified that UCNPs could efficiently activate RAFT polymerization by NIR photoirradiation and construct the complex nanohybrids, exhibiting prospective biomedical applications due to the low phototoxicity and deep penetration of NIR light.

Methods For Improving Polymeric Materials For Use In Solar Cell Applications

DOEpatents

Hanoka, Jack I.

2003-07-01

A method of manufacturing a solar cell module includes the use of low cost polymeric materials with improved mechanical properties. A transparent encapsulant layer is placed adjacent a rear surface of a front support layer. Interconnected solar cells are positioned adjacent a rear surface of the transparent encapsulant layer to form a solar cell assembly. A backskin layer is placed adjacent a rear surface of the solar cell assembly. At least one of the transparent encapsulant layer and the backskin layer are predisposed to electron beam radiation.

Methods For Improving Polymeric Materials For Use In Solar Cell Applications

DOEpatents

Hanoka, Jack I.

2001-11-20

A method of manufacturing a solar cell module includes the use of low cost polymeric materials with improved mechanical properties. A transparent encapsulant layer is placed adjacent a rear surface of a front support layer. Interconnected solar cells are positioned adjacent a rear surface of the transparent encapsulant layer to form a solar cell assembly. A backskin layer is placed adjacent a rear surface of the solar cell assembly. At least one of the transparent encapsulant layer and the backskin layer are predisposed to electron beam radiation.

Laminated structures and methods and compositions for producing same

DOEpatents

Fumei, Giancarlo J.; Karabedian, James A.

1977-04-05

Methods for bonding two substrates, one of which is polymeric, which comprise coating the surface of at least one substrate with an adhesive composition comprising a major component which is an adhesive for the first substrate and a minor disperse phase which is a solution of a polymer in a solvent for the polymeric substrate and contacting the coated surface of the one substrate with the surface of the other substrate, together with adhesive compositions useful for joining such substrates, laminates so formed, and articles comprised of such laminates.

Surface-initiated graft polymerization on multiwalled carbon nanotubes pretreated by corona discharge at atmospheric pressure.

PubMed

Xu, Lihua; Fang, Zhengping; Song, Ping'an; Peng, Mao

2010-03-01

Surface-initiated graft polymerization on multi-walled carbon nanotubes pretreated with a corona discharge at atmospheric pressure was explored. The mechanism of the corona-discharge-induced graft polymerization is discussed. The results indicate that MWCNTs were encapsulated by poly(glycidyl methacrylate) (PGMA), demonstrating the formation of PGMA-grafted MWCNTs (PGMA-g-MWCNTs), with a grafting ratio of about 22 wt%. The solubility of PGMA-g-MWCNTs in ethanol was dramatically improved compared to pristine MWCNTs, which could contribute to fabricating high-performance polymer/MWCNTs nanocomposites in the future. Compared with most plasma processes, which operate at low pressures, corona discharge has the merit of working at atmospheric pressure.

Pharmacological Correction of Trafficking Defects in ATP-sensitive Potassium Channels Caused by Sulfonylurea Receptor 1 Mutations.

PubMed

Martin, Gregory M; Rex, Emily A; Devaraneni, Prasanna; Denton, Jerod S; Boodhansingh, Kara E; DeLeon, Diva D; Stanley, Charles A; Shyng, Show-Ling

2016-10-14

ATP-sensitive potassium (K ATP ) channels play a key role in mediating glucose-stimulated insulin secretion by coupling metabolic signals to β-cell membrane potential. Loss of K ATP channel function due to mutations in ABCC8 or KCNJ11, genes encoding the sulfonylurea receptor 1 (SUR1) or the inwardly rectifying potassium channel Kir6.2, respectively, results in congenital hyperinsulinism. Many SUR1 mutations prevent trafficking of channel proteins from the endoplasmic reticulum to the cell surface. Channel inhibitors, including sulfonylureas and carbamazepine, have been shown to correct channel trafficking defects. In the present study, we identified 13 novel SUR1 mutations that cause channel trafficking defects, the majority of which are amenable to pharmacological rescue by glibenclamide and carbamazepine. By contrast, none of the mutant channels were rescued by K ATP channel openers. Cross-linking experiments showed that K ATP channel inhibitors promoted interactions between the N terminus of Kir6.2 and SUR1, whereas channel openers did not, suggesting the inhibitors enhance intersubunit interactions to overcome channel biogenesis and trafficking defects. Functional studies of rescued mutant channels indicate that most mutants rescued to the cell surface exhibited WT-like sensitivity to ATP, MgADP, and diazoxide. In intact cells, recovery of channel function upon trafficking rescue by reversible sulfonylureas or carbamazepine was facilitated by the K ATP channel opener diazoxide. Our study expands the list of K ATP channel trafficking mutations whose function can be recovered by pharmacological ligands and provides further insight into the structural mechanism by which channel inhibitors correct channel biogenesis and trafficking defects. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Extracellular polymeric substances mediate bioleaching/biocorrosion via interfacial processes involving iron(III) ions and acidophilic bacteria.

PubMed

Sand, Wolfgang; Gehrke, Tilman

2006-01-01

Extracellular polymeric substances seem to play a pivotal role in biocorrosion of metals and bioleaching, biocorrosion of metal sulfides for the winning of precious metals as well as acid rock drainage. For better control of both processes, the structure and function of extracellular polymeric substances of corrosion-causing or leaching bacteria are of crucial importance. Our research focused on the extremophilic bacteria Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans, because of the "simplicity" and knowledge about the interactions of these bacteria with their substrate/substratum and their environment. For this purpose, the composition of the corresponding extracellular polymeric substances and their functions were analyzed. The extracellular polymeric substances of both species consist mainly of neutral sugars and lipids. The functions of the exopolymers seem to be: (i) to mediate attachment to a (metal) sulfide surface, and (ii) to concentrate iron(III) ions by complexation through uronic acids or other residues at the mineral surface, thus, allowing an oxidative attack on the sulfide. Consequently, dissolution of the metal sulfide is enhanced, which may result in an acceleration of 20- to 100-fold of the bioleaching process over chemical leaching. Experiments were performed to elucidate the importance of the iron(III) ions complexed by extracellular polymeric substances for strain-specific differences in oxidative activity for pyrite. Strains of A. ferrooxidans with a high amount of iron(III) ions in their extracellular polymeric substances possess greater oxidation activity than those with fewer iron(III) ions. These data provide insight into the function of and consequently the advantages that extracellular polymeric substances provide to bacteria. The role of extracellular polymeric substances for attachment under the conditions of a space station and resulting effects like biofouling, biocorrosion, malodorous gases, etc. will be discussed.

Cell-micropatterning by micromolding in capillary technique based on UV polymerization

NASA Astrophysics Data System (ADS)

Park, Min J.; Choi, Won M.; Park, O. O.

2006-01-01

Although optical lithography or photolithography is one of the most well-established techniques for micro, nano-fabrication, its usage with proteins and cells is restricted by steps that must be carried out in harsh organic solvents. Here, we present simple methods for cell-micropatterning using poly(dimethylsiloxane) (PDMS) as a mold. Cell non-adhesive surface or nonfouling surface providing a physico-chemical barrier to cell attachment was introduced for biomaterial pattering, where cells fail to interact with the surface over desired periods of time determined by each application. Poly(ethylene glycol) (PEG) was selected as nonfouling material to inhibit protein adsorption from biological media. The fouling resistance of PEG polymer is often explained by a steric repulsion interaction, resulting from the compression of PEG chains as proteins approach the surface. We also chose fibronectin to direct cell attachment because it is an extracellular matrix protein that is involved in the adhesion and spreading of anchorage-dependent cells. In our experiment, we propose two methods by application of micromolding in capillary (MIMIC) method based on UV polymerization to obtain a surface of alternating PEG and fibronectin. First to fabricate PEG microstructure via MIMIC method, a pre-patterned PDMS mold is placed on a desired substrate, and then the relief structure in the mold forms a network of empty channels. A drop of ethylene glycol monomer solution containing initiator for UV polymerization is placed at the open ends of the network of channels, which is then polymerized by exposure to UV light at room temperature. Once PEG microstructure is fabricated, incubation of the patterned surface in a fibronectin-containing solution allows back-filling of only the bare regions with fibronectin via adsorption. In the alternative method, a substrate is first incubated in a fibronectin-containing solution, leading to the adsorption of fibronectin over the entire surface, and the fibronectin-adsorbed substrate is then micropatterned with the PEG by MIMIC based on UV polymerization. Both methods create reproducible alternating PEG and fibronectin patterns applicable to cell-surface interactions on the microscale.

Application of Plasma Technology in the Life Sciences

NASA Astrophysics Data System (ADS)

Short, Robert

2002-10-01

This paper explores the versatility of plasma polymerization in the fabrication of surfaces for use in the Life Sciences and Tissue Engineering, highlighting three successful applications of plasma polymerized surfaces. 1. Plasma polymerized acrylic acid surfaces have been used as substrates for the culture and delivery of keratinocytes (skin cells) to chronic wounds. In proof of concept studies weekly delivery of keratinocytes have promoted healing in previously non-healing wounds. These include diabetic foot ulcers and wounds where skin grafts would normally be considered, but were contra-indicated. 2. Surface chemical patterning on the micrometer scale- length, by use of pre-fabricated masks, has been used to control the spatial binding of proteins and cells. This technology makes possible a significant reduction in size of biological assays, reducing the amount of material (e.g. antibody) or cells required. 3. Surface chemical potential gradients, from a few tens of micrometers to a few centrimeters, have been fabricated by "plasma writing", a technique currently being developed in Sheffield. These gradients are being developed to separate mixtures of biomolecules or cells.

Formation of a Crack-Free, Hybrid Skin Layer with Tunable Surface Topography and Improved Gas Permeation Selectivity on Elastomers Using Gel–Liquid Infiltration Polymerization

DOE PAGES

Wang, Mengyuan; Gorham, Justin M.; Killgore, Jason P.; ...

2017-07-31

Surface modifications of elastomers and gels are crucial for emerging applications such as soft robotics and flexible electronics, in large part because they provide a platform to control wettability, adhesion, and permeability. Current surface modification methods via ultraviolet-ozone (UVO) and/or O2 plasma, atomic layer deposition (ALD), plasmas deposition, and chemical treatment impart a dense polymer or inorganic layer on the surface that is brittle and easy to fracture at low strain levels. This paper presents a new method, based on gel–liquid infiltration polymerization, to form hybrid skin layers atop elastomers. The method is unique in that it allows for controlmore » of the skin layer topography, with tunable feature sizes and aspect ratios as high as 1.8 without fracture. Unlike previous techniques, the skin layer formed here dramatically improves the barrier properties of the elastomer, while preserving skin layer flexibility. Furthermore, the method is versatile and likely applicable to most interfacial polymerization systems and network polymers on flat and patterned surfaces.« less

Formation of a Crack-Free, Hybrid Skin Layer with Tunable Surface Topography and Improved Gas Permeation Selectivity on Elastomers Using Gel–Liquid Infiltration Polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Mengyuan; Gorham, Justin M.; Killgore, Jason P.

Surface modifications of elastomers and gels are crucial for emerging applications such as soft robotics and flexible electronics, in large part because they provide a platform to control wettability, adhesion, and permeability. Current surface modification methods via ultraviolet-ozone (UVO) and/or O2 plasma, atomic layer deposition (ALD), plasmas deposition, and chemical treatment impart a dense polymer or inorganic layer on the surface that is brittle and easy to fracture at low strain levels. This paper presents a new method, based on gel–liquid infiltration polymerization, to form hybrid skin layers atop elastomers. The method is unique in that it allows for controlmore » of the skin layer topography, with tunable feature sizes and aspect ratios as high as 1.8 without fracture. Unlike previous techniques, the skin layer formed here dramatically improves the barrier properties of the elastomer, while preserving skin layer flexibility. Furthermore, the method is versatile and likely applicable to most interfacial polymerization systems and network polymers on flat and patterned surfaces.« less

Versatile and Rapid Postfunctionalization from Cyclodextrin Modified Host Polymeric Membrane Substrate.

PubMed

Deng, Jie; Liu, Xinyue; Zhang, Shuqing; Cheng, Chong; Nie, Chuanxiong; Zhao, Changsheng

2015-09-08

Surface modification has long been of great interest to impart desired functionalities to the bioimplants. However, due to the limitations of recent technologies in surface modification, it is highly desirable to explore novel protocols, which can advantageously and efficiently endow the inert material surfaces with versatile biofunctionalities. Herein, to achieve versatile and rapid postfunctionalization of polymeric membrane, we demonstrate a new strategy for the fabrication of β-cyclodextrin (β-CD) modified host membrane substrate that can recognize a series of well-designed guest macromolecules. The surface assembly procedure was driven by the host-guest interaction between adamantane (Ad) and β-CD. β-CD immobilized host membrane was fabricated via two steps: (1) epoxy groups enriched poly(ether sulfone) (PES) membrane was first prepared via in situ cross-linking polymerization and subsequently phase separation; (2) mono-6-deoxy-6-ethylenediamine-β-CD (EDA-β-CD) was then anchored onto the surface of the epoxy functionalized PES membrane to obtain PES-CD. Subsequently, three types of Ad-terminated polymers, including Ad-poly(styrenesulfonate-co-sodium acrylate) (Ad-PSA), Ad-methoxypoly(ethylene glycol) (Ad-PEG), and Ad-poly(methyl chloride-quaternized 2-(dimethylamino)ethyl methacrylate (Ad-PMT), were separately assembled onto the β-CD immobilized surfaces to endow the membranes with anticoagulant, antifouling, and antibacterial capability, respectively. Activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT) measurements were carried out to explore the anticoagulant activity. The antifouling capability was evaluated via protein adsorption and platelet adhesion measurements. Moreover, Staphyllococcous aureus (S. aureus) was selected as model bacteria to evaluate the antibacterial ability of the functionalized membranes. The results indicated that well-regulated blood compatibility, antifouling capability, and bactericidal activity could be achieved by the proposed rapid postfunctionalization on polymeric membranes. This approach of versatile and rapid postfunctionalization is promising for the preparation of multifunctional polymeric membrane materials to meet with various demands for the further applications.

Enhanced protein retention on poly(caprolactone) via surface initiated polymerization of acrylamide

NASA Astrophysics Data System (ADS)

Ma, Yuhao; Cai, Mengtan; He, Liu; Luo, Xianglin

2016-01-01

To enhance the biocompatibility or extend the biomedical application of poly(caprolactone) (PCL), protein retention on PCL surface is often required. In this study, poly(acrylamide) (PAAm) brushes were grown from PCL surface via surface-initiated atom transfer radical polymerization (SI-ATRP) and served as a protein-capturing platform. Grafted PAAm was densely packed on surface and exhibited superior protein retention ability. Captured protein was found to be resistant to washing under detergent environment. Furthermore, protein structure after being captured was investigated by circular dichroism (CD) spectroscopy, and the CD spectra verified that secondary structure of captured proteins was maintained, indicating no denaturation of protein happened for retention process.

Spatial control of actin polymerization during neutrophil chemotaxis

PubMed Central

Weiner, Orion D.; Servant, Guy; Welch, Matthew D.; Mitchison, Timothy J.; Sedat, John W.; Bourne, Henry R.

2010-01-01

Neutrophils respond to chemotactic stimuli by increasing the nucleation and polymerization of actin filaments, but the location and regulation of these processes are not well understood. Here, using a permeabilized-cell assay, we show that chemotactic stimuli cause neutrophils to organize many discrete sites of actin polymerization, the distribution of which is biased by external chemotactic gradients. Furthermore, the Arp2/3 complex, which can nucleate actin polymerization, dynamically redistributes to the region of living neutrophils that receives maximal chemotactic stimulation, and the least-extractable pool of the Arp2/3 complex co-localizes with sites of actin polymerization. Our observations indicate that chemoattractant-stimulated neutrophils may establish discrete foci of actin polymerization that are similar to those generated at the posterior surface of the intracellular bacterium Listeria monocytogenes. We propose that asymmetrical establishment and/or maintenance of sites of actin polymerization produces directional migration of neutrophils in response to chemotactic gradients. PMID:10559877

Spatial control of actin polymerization during neutrophil chemotaxis.

PubMed

Weiner, O D; Servant, G; Welch, M D; Mitchison, T J; Sedat, J W; Bourne, H R

1999-06-01

Neutrophils respond to chemotactic stimuli by increasing the nucleation and polymerization of actin filaments, but the location and regulation of these processes are not well understood. Here, using a permeabilized-cell assay, we show that chemotactic stimuli cause neutrophils to organize many discrete sites of actin polymerization, the distribution of which is biased by external chemotactic gradients. Furthermore, the Arp2/3 complex, which can nucleate actin polymerization, dynamically redistributes to the region of living neutrophils that receives maximal chemotactic stimulation, and the least-extractable pool of the Arp2/3 complex co-localizes with sites of actin polymerization. Our observations indicate that chemoattractant-stimulated neutrophils may establish discrete foci of actin polymerization that are similar to those generated at the posterior surface of the intracellular bacterium Listeria monocytogenes. We propose that asymmetrical establishment and/or maintenance of sites of actin polymerization produces directional migration of neutrophils in response to chemotactic gradients.

Signal amplification strategies for DNA and protein detection based on polymeric nanocomposites and polymerization: A review.

PubMed

Zhou, Shaohong; Yuan, Liang; Hua, Xin; Xu, Lingling; Liu, Songqin

2015-06-02

Demand is increasing for ultrasensitive bioassays for disease diagnosis, environmental monitoring and other research areas. This requires novel signal amplification strategies to maximize the signal output. In this review, we focus on a series of significant signal amplification strategies based on polymeric nanocomposites and polymerization. Some common polymers are used as carriers to increase the local concentration of signal probes and/or biomolecules on their surfaces or in their interiors. Some polymers with special fluorescence and optical properties can efficiently transfer the excitation energy from a single site to the whole polymer backbone. This results in superior fluorescence signal amplification due to the resulting collective effort (integration of signal). Recent polymerization-based signal amplification strategies that employ atom transfer radical polymerization (ATRP) and photo-initiated polymerization are also summarized. Several distinctive applications of polymers in ultrasensitive bioanalysis are highlighted. Copyright © 2015 Elsevier B.V. All rights reserved.

Polymerization in the gas phase, in clusters, and on nanoparticle surfaces.

PubMed

El-Shall, M Samy

2008-07-01

Gas phase and cluster experiments provide unique opportunities to quantitatively study the effects of initiators, solvents, chain transfer agents, and inhibitors on the mechanisms of polymerization. Furthermore, a number of important phenomena, unique structures, and novel properties may exist during gas-phase and cluster polymerization. In this regime, the structure of the growing polymer may change dramatically and the rate coefficient may vary significantly upon the addition of a single molecule of the monomer. These changes would be reflected in the properties of the oligomers deposited from the gas phase. At low pressures, cationic and radical cationic polymerizations may proceed in the gas phase through elimination reactions. In the same systems at high pressure, however, the ionic intermediates may be stabilized, and addition without elimination may occur. In isolated van der Waals clusters of monomer molecules, sequential polymerization with several condensation steps can occur on a time scale of a few microseconds following the ionization of the gas-phase cluster. The cluster reactions, which bridge gas-phase and condensed-phase chemistry, allow examination of the effects of controlled states of aggregation. This Account describes several examples of gas-phase and cluster polymerization studies where the most significant results can be summarized as follows: (1) The carbocation polymerization of isobutene shows slower rates with increasing polymerization steps resulting from entropy barriers, which could explain the need for low temperatures for the efficient propagation of high molecular weight polymers. (2) Radical cation polymerization of propene can be initiated by partial charge transfer from an ionized aromatic molecule such as benzene coupled with covalent condensation of the associated propene molecules. This novel mechanism leads exclusively to the formation of propene oligomer ions and avoids other competitive products. (3) Structural information on the oligomers formed by gas-phase polymerization can be obtained using the mass-selected ion mobility technique where the measured collision cross-sections of the selected oligomer ions and collision-induced dissociation can provide fairly accurate structural identifications. The identification of the structures of the dimers and trimers formed in the gas-phase thermal polymerization of styrene confirms that the polymerization proceeds according to the Mayo mechanism. Similarly, the ion mobility technique has been utilized to confirm the formation of benzene cations by intracluster polymerization following the ionization of acetylene clusters. Finally, it has been shown that polymerization of styrene vapor on the surface of activated nanoparticles can lead to the incorporation of a variety of metal and metal oxide nanoparticles within polystyrene films. The ability to probe the reactivity and structure of the small growing oligomers in the gas phase can provide fundamental insight into mechanisms of polymerization that are difficult to obtain from condensed-phase studies. These experiments are also important for understanding the growth mechanisms of complex organics in flames, combustion processes, interstellar clouds, and solar nebula where gas-phase reactions, cluster polymerization, and surface catalysis on dust nanoparticles represent the major synthetic pathways. This research can lead to the discovery of novel initiation mechanisms and reaction pathways with applications in the synthesis of oligomers and nanocomposites with unique and improved properties.

Biaxially oriented film on flexible polymeric substrate

DOEpatents

Finkikoglu, Alp T [Los Alamos, NM; Matias, Vladimir [Santa Fe, NM

2009-10-13

A flexible polymer-based template having a biaxially oriented film grown on the surface of a polymeric substrate. The template having the biaxially oriented film can be used for further epitaxial growth of films of interest for applications such as photovoltaic cells, light emitting diodes, and the like. Methods of forming such a flexible template and providing the polymeric substrate with a biaxially oriented film deposited thereon are also described.

Caracterisation thermique de modules de refroidissement pour la photovoltaique concentree

NASA Astrophysics Data System (ADS)

Collin, Louis-Michel

Pour rentabiliser la technologie des cellules solaires, une reduction du cout d'exploitation et de fabrication est necessaire. L'utilisation de materiaux photovoltaiques a un impact appreciable sur le prix final par quantite d'energie produite. Une technologie en developpement consiste a concentrer la lumiere sur les cellules solaires afin de reduire cette quantite de materiaux. Or, concentrer la lumiere augmente la temperature de la cellule et diminue ainsi son efficacite. Il faut donc assurer a la cellule un refroidissement efficace. La charge thermique a evacuer de la cellule passe au travers du recepteur, soit la composante soutenant physiquement la cellule. Le recepteur transmet le flux thermique de la cellule a un systeme de refroidissement. L'ensemble recepteur-systeme de refroidissement se nomme module de refroidissement. Habituellement, la surface du recepteur est plus grande que celle de la cellule. La chaleur se propage donc lateralement dans le recepteur au fur et a mesure qu'elle traverse le recepteur. Une telle propagation de la chaleur fournit une plus grande surface effective, reduisant la resistance thermique apparente des interfaces thermiques et du systeme de refroidissement en aval vers le module de refroidissement. Actuellement, aucune installation ni methode ne semble exister afin de caracteriser les performances thermiques des recepteurs. Ce projet traite d'une nouvelle technique de caracterisation pour definir la diffusion thermique du recepteur a l'interieur d'un module de refroidissement. Des indices de performance sont issus de resistances thermiques mesurees experimentalement sur les modules. Une plateforme de caracterisation est realisee afin de mesurer experimentalement les criteres de performance. Cette plateforme injecte un flux thermique controle sur une zone localisee de la surface superieure du recepteur. L'injection de chaleur remplace le flux thermique normalement fourni par la cellule. Un systeme de refroidissement est installe a la surface opposee du recepteur pour evacuer la chaleur injectee. Les resultats mettent egalement en evidence l'importance des interfaces thermiques et les avantages de diffuser la chaleur dans les couches metalliques avant de la conduire au travers des couches dielectriques du recepteur. Des recepteurs de multiples compositions ont ete caracterises, demontrant que les outils developpes peuvent definir la capacite de diffusion thermique. La repetabilite de la plateforme est evaluee par l'analyse de l'etendue des mesures repetees sur des echantillons selectionnes. La plateforme demontre une precision et reproductibilite de +/- 0.14 ° C/W. Ce travail fournit des outils pour la conception des recepteurs en proposant une mesure qui permet de comparer et d'evaluer l'impact thermique de ces recepteurs integres a uri module de refroidissement. Mots-cles : cellule solaire, photovoltaique, transfert de chaleur, concentration, resistances thermiques, plateforme de caracterisation, refroidissement

Chimeric protein identification of dystrophic, Pierson and other laminin polymerization residues

PubMed Central

McKee, Karen K.; Aleksandrova, Maya; Yurchenco, Peter D.

2018-01-01

Laminin polymerization is a key step of basement membrane self-assembly that depends on the binding of the three different N-terminal globular LN domains. Several mutations in the LN domains cause LAMA2-deficient muscular dystrophy and LAMB2-deficient Pierson syndrome. These mutations may affect polymerization. A novel approach to identify the amino acid residues required for polymerization has been applied to an analysis of these and other laminin LN mutations. The approach utilizes laminin-nidogen chimeric fusion proteins that bind to recombinant non-polymerizing laminins to provide a missing functional LN domain. Single amino acid substitutions introduced into these chimeras were tested to determine if polymerization activity and the ability to assemble on cell surfaces were lost. Several laminin-deficient muscular dystrophy mutations, renal Pierson syndrome mutations, and Drosophila mutations causing defects of heart development were identified as ones causing loss of laminin polymerization. In addition, two novel residues required for polymerization were identified in the laminin γ1 LN domain. PMID:29408412

Bacterial adhesion on conventional and self-ligating metallic brackets after surface treatment with plasma-polymerized hexamethyldisiloxane.

PubMed

Tupinambá, Rogerio Amaral; Claro, Cristiane Aparecida de Assis; Pereira, Cristiane Aparecida; Nobrega, Celestino José Prudente; Claro, Ana Paula Rosifini Alves

2017-01-01

Plasma-polymerized film deposition was created to modify metallic orthodontic brackets surface properties in order to inhibit bacterial adhesion. Hexamethyldisiloxane (HMDSO) polymer films were deposited on conventional (n = 10) and self-ligating (n = 10) stainless steel orthodontic brackets using the Plasma-Enhanced Chemical Vapor Deposition (PECVD) radio frequency technique. The samples were divided into two groups according to the kind of bracket and two subgroups after surface treatment. Scanning Electron Microscopy (SEM) analysis was performed to assess the presence of bacterial adhesion over samples surfaces (slot and wings region) and film layer integrity. Surface roughness was assessed by Confocal Interferometry (CI) and surface wettability, by goniometry. For bacterial adhesion analysis, samples were exposed for 72 hours to a Streptococcus mutans solution for biofilm formation. The values obtained for surface roughness were analyzed using the Mann-Whitney test while biofilm adhesion were assessed by Kruskal-Wallis and SNK test. Significant statistical differences (p< 0.05) for surface roughness and bacterial adhesion reduction were observed on conventional brackets after surface treatment and between conventional and self-ligating brackets; no significant statistical differences were observed between self-ligating groups (p> 0.05). Plasma-polymerized film deposition was only effective on reducing surface roughness and bacterial adhesion in conventional brackets. It was also noted that conventional brackets showed lower biofilm adhesion than self-ligating brackets despite the absence of film.

NiTi shape memory alloys treated by plasma-polymerized tetrafluoroethylene. A physicochemical and electrochemical characterization.

PubMed

Yahia, L H; Lombardi, S; Piron, D; Klemberg-Sapieha, J E; Wertheimer, M R

NiTi alloy specimens were plasma cleaned and then coated with a thin film of plasma-polymerized tetrafluoroethylene (TFE) in a Radio-Frequency reactor. The corrosion protection provided by these films was studied by potentiodynamic tests performed in Hank's physiological solution. Surface properties which determine biocompatibility were characterized by X-ray photoelectron spectroscopy (XPS). The results showed that the surface of untreated NiTi was mostly composed by oxygen, carbon, titanium oxide (TiO2) with traces of nickel oxides (NiO and Ni2O3) and metallic Ni. The passivity of untreated NiTi was found to be unstable in the simulated human body media. After plasma treatment, the NiTi surface contained only carbon and fluor. The plasma-polymerized thin film was found to stabilize the NiTi passivity and to increase its pitting potential. This treatment provides a good protection against dissolution of nickel from NiTi alloys.

Preparing high-density polymer brushes by mechanically assisted polymer assembly (MAPA)

NASA Astrophysics Data System (ADS)

Wu, Tao; Efimenko, Kirill; Genzer, Jan

2001-03-01

We introduce a novel method of modifying the surface properties of materials. This technique, called MAPA (="mechanically assisted polymer assembly"), is based on: 1) chemically attaching polymerization initiators to the surface of an elastomeric network that has been previously stretched by a certain length, Δx, and 2) growing end-anchored macromolecules using surface initiated ("grafting from") atom transfer living radical polymerization. After the polymerization, the strain is removed from the substrate, which returns to its original size causing the grafted macromolecules to stretch away from the substrate and form a dense polymer brush. We demonstrate the feasibility of the MAPA method by preparing high-density polymer brushes of poly(acryl amide), PAAm. We show that, as expected, the grafting density of the PAAm brushes can be increased by increasing Δx. We demonstrate that polymer brushes with extremely high grafting densities can be successfully prepared by MAPA.

Polymerization on the rocks: beta-amino acids and arginine

NASA Technical Reports Server (NTRS)

Liu, R.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

1998-01-01

We have studied the accumulation of long oligomers of beta-amino acids on the surface of minerals using the 'polymerization on the rocks' protocol. We find that long oligopeptides of beta-glutamic acid which cannot be formed in homogeneous aqueous solution are accumulated efficiently on the surface of hydroxylapatite using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) as condensing agent. The EDAC-induced oligomerization of aspartic acid on hydroxylapatite proceeds even more efficiently. Hydroxylapatite can also facilitate the ligation of the tripeptide (glu)3. The 'polymerization on the rocks' scenario is not restricted to negatively-charged amino acids. Oligoarginines are accumulated on the surface of illite using carbonyldiimidizole (CDI) as condensing agent. We find that FeS2 catalyzes the CDI-induced oligomerization of arginine, although it does not adsorb oligoarginines. These results are relevant to the formation of polypeptides on the primitive earth.

Preparation of thermo-responsive polymer brushes on hydrophilic polymeric beads by surface-initiated atom transfer radical polymerization for a highly resolutive separation of peptides.

PubMed

Mizutani, Aya; Nagase, Kenichi; Kikuchi, Akihiko; Kanazawa, Hideko; Akiyama, Yoshikatsu; Kobayashi, Jun; Annaka, Masahiko; Okano, Teruo

2010-09-17

Poly(N-isopropylacrylamide-co-N-tert-butylacrylamide) [P(IPAAm-co-tBAAm)] brushes were prepared on poly(hydroxy methacrylate) (PHMA) [hydrolyzed poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate)] beads having large pores by surface-initiated atom transfer radical polymerization (ATRP) and applied to the stationary phases of thermo-responsive chromatography. Optimized amount of copolymer brushes grafted PHMA beads were able to separate peptides and proteins with narrow peaks and a high resolution. The beads were found to have a specific surface area of 43.0 m(2)/g by nitrogen gas adsorption method. Copolymer brush of P(IPAAm-co-tBAAm) grafted PHMA beads improved the stationary phase of thermo-responsive chromatography for the all-aqueous separation of peptides and proteins. 2010 Elsevier B.V. All rights reserved.

Mussel inspired polymerized P(TA-TETA) for facile functionalization of carbon nanotube

NASA Astrophysics Data System (ADS)

Si, Shuxian; Gao, Tingting; Wang, Junhao; Liu, Qinze; Zhou, Guowei

2018-03-01

This article describes a novel and effective approach for non-covalent modification of carbon nanotube (CNT) via the mussel inspired polymerization of tannic acid (TA) and triethylenetetramine (TETA) and subsequent surface initiated atom transfer radical polymerization (SI-ATRP). Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and photograph were used to study the successful preparation of polymer brush grafted CNT (CNT-P(TA-TETA)-PDMAEMA) composite as well as the pH-responsive behavior of the composite. Furthermore, by amine protonation and in situ reduction, gold nanoparticles were successfully uploaded and the catalytic property of CNT-P(TA-TETA)-PDMAEMA/Au was investigated. We believe that the surface functionalization strategy can be extended to graphene and other substrates, and the surface properties can be regulated by grafting polymer brushes with different functionalities.

Deposition of functionalized polymer layers in surface plasmon resonance immunosensors by in-situ polymerization in the evanescent wave field.

PubMed

Chegel, Vladimir; Whitcombe, Michael J; Turner, Nicholas W; Piletsky, Sergey A

2009-01-01

Traditionally, the integration of sensing gel layers in surface plasmon resonance (SPR) is achieved via "bulk" methods, such as precipitation, spin-coating or in-situ polymerization onto the total surface of the sensor chip, combined with covalent attachment of the antibody or receptor to the gel surface. This is wasteful in terms of materials as the sensing only occurs at the point of resonance interrogated by the laser. By isolating the sensing materials (antibodies, enzymes, aptamers, polymers, MIPs, etc.) to this exact spot a more efficient use of these recognition elements will be achieved. Here we present a method for the in-situ formation of polymers, using the energy of the evanescent wave field on the surface of an SPR device, specifically localized at the point of interrogation. Using the photo-initiator couple of methylene blue (sensitizing dye) and sodium p-toluenesulfinate (reducing agent) we polymerized a mixture of N,N-methylene-bis-acrylamide and methacrylic acid in water at the focal point of SPR. No polymerization was seen in solution or at any other sites on the sensor surface. Varying parameters such as monomer concentration and exposure time allowed precise control over the polymer thickness (from 20-200 nm). Standard coupling with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide was used for the immobilization of protein G which was used to bind IgG in a typical biosensor format. This model system demonstrated the characteristic performance for this type of immunosensor, validating our deposition method.

Dynamic bioactive stimuli-responsive polymeric surfaces

NASA Astrophysics Data System (ADS)

Pearson, Heather Marie

This dissertation focuses on the design, synthesis, and development of antimicrobial and anticoagulant surfaces of polyethylene (PE), polypropylene (PP), and poly(tetrafluoroethylene) (PTFE) polymers. Aliphatic polymeric surfaces of PE and PP polymers functionalized using click chemistry reactions by the attachment of --COOH groups via microwave plasma reactions followed by functionalization with alkyne moieties. Azide containing ampicillin (AMP) was synthesized and subsequently clicked into the alkyne prepared PE and PP surfaces. Compared to non-functionalized PP and PE surfaces, the AMP clicked surfaces exhibited substantially enhanced antimicrobial activity against Staphylococcus aureus bacteria. To expand the biocompatibility of polymeric surface anticoagulant attributes, PE and PTFE surfaces were functionalized with pH-responsive poly(2-vinyl pyridine) (P2VP) and poly(acrylic acid) (PAA) polyelectrolyte tethers terminated with NH2 and COOH groups. The goal of these studies was to develop switchable stimuli-responsive polymeric surfaces that interact with biological environments and display simultaneous antimicrobial and anticoagulant properties. Antimicrobial AMP was covalently attached to --COOH terminal ends of protected PAA, while anticoagulant heparin (HEP) was attached to terminal --NH2 groups of P2VP. When pH < 2.3, the P2VP segments are protonated and extend, but for pH > 5.5, they collapse while the PAA segments extend. Such surfaces, when exposed to Staphylococcus aureus, inhibit bacterial growth due to the presence of AMP, as well as are effective anticoagulants due to the presence of covalently attached HEP. Comparison of these "dynamic" pH responsive surfaces with "static" surfaces terminated with AMP entities show significant enhancement of longevity and surface activity against microbial film formation. The last portion of this dissertation focuses on the covalent attachment of living T1 and Φ11 bacteriophages (phages) on PE and PTFE surface. This was accomplished by carbodiimide coupling between --COOH groups on PE and PTFE surfaces and --NH2 moieties present on T1 and Φ11 phages. These studies show that covalently attached T1 and Φ11 phages retain their antimicrobial activity manifested by the effective destruction of both Gram negative Escherichia coli (Φ11) phages and Gram positive Staphylococcus aureus bacteria (T1).

Preparation and surface characterization of plasma-treated and biomolecular-micropatterned polymer substrates

NASA Astrophysics Data System (ADS)

Langowski, Bryan Alfred

A micropatterning process creates distinct microscale domains on substrate surfaces that differ from the surfaces' original chemical/physical properties. Numerous micropatterning methods exist, each having relative advantages and disadvantages in terms of cost, ease, reproducibility, and versatility. Polymeric surfaces micropatterned with biomolecules have many applications, but are specifically utilized in tissue engineering as cell scaffolds that attempt to controlled tissue generation in vivo and ex vivo. As the physical and chemical cues presented by micropatterned substrates control resulting cellular behavior, characterization of these cues via surface-sensitive analytical techniques is essential in developing cell scaffolds that mimic complex in vivo physicochemical environments. The initial focus of this thesis is the chemical and physical characterization of plasma-treated, microcontact-printed (muCP) polymeric substrates used to direct nerve cell behavior. Unmodified and oxygen plasma-treated poly(methyl methacrylate) (PMMA) substrates were analyzed by surface sensitive techniques to monitor plasma-induced chemical and physical modifications. Additionally, protein-micropattern homogeneity and size were microscopically evaluated. Lastly, poly(dimethylsiloxane) (PDMS) stamps and contaminated PMMA substrates were characterized by spectroscopic and microscopic methods to identify a contamination source during microcontact printing. The final focus of this thesis is the development of microscale plasma-initiated patterning (muPIP) as a versatile, reproducible micropatterning method. Using muPIP, polymeric substrates were micropatterned with several biologically relevant inks. Polymeric substrates were characterized following muPIP by surface-sensitive techniques to identify the technique's underlying physical and chemical bases. In addition, neural stem cell response to muPIP-generated laminin micropatterns was microscopically and biologically evaluated. Finally, enhanced versatility of muPIP in generating microscale poly-L-lysine gradients was demonstrated.

Shape-Persistent, Thermoresponsive Polypeptide Brushes Prepared by Vapor Deposition Surface-Initiated Ring-Opening Polymerization of α-Amino Acid N -Carboxyanhydrides

DOE PAGES

Shen, Yong; Desseaux, Solenne; Aden, Bethany; ...

2015-04-20

We report that surface-grafting thermoresponsive polymers allows the preparation of thin polymer brush coatings with surface properties that can be manipulated by variation of temperature. In most instances, thermoresponsive polymer brushes are produced using polymers that dehydrate and collapse above a certain temperature. This report presents the preparation and properties of polymer brushes that show thermoresponsive surface properties, yet are shape-persistent in that they do not undergo main chain collapse. The polymer brushes presented here are obtained via vapor deposition surface-initiated ring-opening polymerization (SI-ROP) of γ-di- or tri(ethylene glycol)-modified glutamic acid N-carboxyanhydrides. Vapor deposition SI-ROP of γ-di- or tri(ethylene glycol)-modifiedmore » L- or D-glutamic acid N-carboxyanhydrides affords helical surface-tethered polymer chains that do not show any changes in secondary structure between 10 and 70 °C. QCM-D experiments, however, revealed significant dehydration of poly(γ-(2-(2-methoxyethoxy)ethyl)-l-glutamate) (poly(L-EG 2-Glu)) brushes upon heating from 10 to 40 °C. At the same time, AFM and ellipsometry studies did not reveal significant variations in film thickness over this temperature range, which is consistent with the shape-persistent nature of these polypeptide brushes and indicates that the thermoresponsiveness of the films is primarily due to hydration and dehydration of the oligo(ethylene glycol) side chains. The results we present here illustrate the potential of surface-initiated NCA ring-opening polymerization to generate densely grafted assemblies of polymer chains that possess well-defined secondary structures and tunable surface properties. These polypeptide brushes complement their conformationally unordered counterparts that can be generated via surface-initiated polymerization of vinyl-type monomers and represent another step forward to biomimetic surfaces and interfaces.« less

JPRS Report, Science & Technology, USSR: Chemistry.

DTIC Science & Technology

1988-12-23

Escape Accidents at Nuclear Power Plant With Water Moderated Reactors [S. A. Kabakehi, M. A. Budayev, et al.; KHIMIYA VYSOKIKH ENERGIY, Vol 22 No 4...water on the reactor surface also lowered loss of radicals. In general, the extent and temperature function Study of Radicals Desorbing From Surface... reactor sur- Alcohols With Oxygen face, by adsorption of the reagents and reaction products 184100 13f Moscow KHIMICHESKA YA FIZIKA on this surface and the

Development of a Dynamic Biomechanical Model for Load Carriage: Phase IV Part C1: Assessment of Pressure Measurement Systems on Flat Surfaces for use in Human Load Carriage

DTIC Science & Technology

2005-08-01

iv Sommaire Les études sur les effets de la pression de contact produite par une charge d’un sac à dos sont essentielles, étant...mobilité des soldats et amenuiser leur capacité de combat. Afin de mieux comprendre les effets de la pression d’un sac à dos sur le confort et la... de mesure de pression qui pourraient être utilisés pour établir les valeurs de tolérance de la peau aux pressions durant le transport d’une charge

Fabrication of high-capacity polyelectrolyte brush-grafted porous AAO-silica composite membrane via RAFT polymerization.

PubMed

Song, Cunfeng; Wang, Meijie; Liu, Xin; Wang, He; Chen, Xiaoling; Dai, Lizong

2017-09-01

Surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization has been utilized to fabricate high-capacity strong anion-exchange (AEX) membrane for the separation of protein. By means of RAFT polymerization, quaternized poly(3-(methacrylamidomethyl)-pyridine) brushes formed 3-dimensional nanolayers on the surface of porous anodic aluminum oxide (AAO)-silica composite membrane. The surface properties of the membranes were analyzed by SEM, water contact angle, ATR-FTIR, XPS and TGA. To investigate the adsorption performance, the new AEX membranes were applied to recover a model protein, ovalbumin (OVA). High adsorption capacities of 95.8mg/g membranes (static) and 65.3mg/g membranes (dynamic) were obtained at ambient temperature. In the further studies, up to 90% of the adsorbed OVA was efficiently eluted by using phosphate buffer-1M NaCl as elution medium. The successful separation of OVA with high purity from a mixture protein solution was also achieved by using the AEX membranes. The present study demonstrated that under mild reaction condition, RAFT polymerization can be used to fabricate ion-exchange membrane which has many remarkable features, such as high capacity and selectivity, easy elution and so on. Copyright © 2017. Published by Elsevier B.V.

Tailoring the nanoscale morphology of HKUST-1 thin films via codeposition and seeded growth

PubMed Central

Brower, Landon J; Gentry, Lauren K; Napier, Amanda L

2017-01-01

Integration of surface-anchored metal-organic frameworks (surMOFs) within hierarchical architectures is necessary for potential sensing, electronic, optical, or separation applications. It is important to understand the fundamentals of film formation for these surMOFs in order to develop strategies for their incorporation with nanoscale control over lateral and vertical dimensions. This research identified processing parameters to control the film morphology for surMOFs of HKUST-1 fabricated by codeposition and seeded deposition. Time and temperature were investigated to observe film formation, to control film thickness, and to tune morphology. Film thickness was investigated by ellipsometry, while film structure and film roughness were characterized by atomic force microscopy. Films formed via codeposition resulted in nanocrystallites anchored to the gold substrate. A dynamic process at the interface was observed with a low density of large particulates (above 100 nm) initially forming on the substrate; and over time these particulates were slowly replaced by the prevalence of smaller crystallites (ca. 10 nm) covering the substrate at a high density. Elevated temperature was found to expedite the growth process to obtain the full range of surface morphologies with reasonable processing times. Seed crystals formed by the codeposition method were stable and nucleated growth throughout a subsequent layer-by-layer deposition process. These seed crystals templated the final film structure and tailor the features in lateral and vertical directions. Using codeposition and seeded growth, different surface morphologies with controllable nanoscale dimensions can be designed and fabricated for integration of MOF systems directly into device architectures and sensor platforms. PMID:29181287

Tailoring the nanoscale morphology of HKUST-1 thin films via codeposition and seeded growth.

PubMed

Brower, Landon J; Gentry, Lauren K; Napier, Amanda L; Anderson, Mary E

2017-01-01

Integration of surface-anchored metal-organic frameworks (surMOFs) within hierarchical architectures is necessary for potential sensing, electronic, optical, or separation applications. It is important to understand the fundamentals of film formation for these surMOFs in order to develop strategies for their incorporation with nanoscale control over lateral and vertical dimensions. This research identified processing parameters to control the film morphology for surMOFs of HKUST-1 fabricated by codeposition and seeded deposition. Time and temperature were investigated to observe film formation, to control film thickness, and to tune morphology. Film thickness was investigated by ellipsometry, while film structure and film roughness were characterized by atomic force microscopy. Films formed via codeposition resulted in nanocrystallites anchored to the gold substrate. A dynamic process at the interface was observed with a low density of large particulates (above 100 nm) initially forming on the substrate; and over time these particulates were slowly replaced by the prevalence of smaller crystallites (ca. 10 nm) covering the substrate at a high density. Elevated temperature was found to expedite the growth process to obtain the full range of surface morphologies with reasonable processing times. Seed crystals formed by the codeposition method were stable and nucleated growth throughout a subsequent layer-by-layer deposition process. These seed crystals templated the final film structure and tailor the features in lateral and vertical directions. Using codeposition and seeded growth, different surface morphologies with controllable nanoscale dimensions can be designed and fabricated for integration of MOF systems directly into device architectures and sensor platforms.

Method of making controlled morphology metal-oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ozcan, Soydan; Lu, Yuan

2016-05-17

A method of making metal oxides having a preselected morphology includes preparing a suspension that includes a solvent, polymeric nanostructures having multiplicities of hydroxyl surface groups and/or carboxyl surface groups, and a metal oxide precursor. The suspension has a preselected ratio of the polymeric nanostructures to the metal oxide precursor of at least 1:3, the preselected ratio corresponding to a preselected morphology. Subsequent steps include depositing the suspension onto a substrate, removing the solvent to form a film, removing the film from the substrate, and annealing the film to volatilize the polymeric nanostructures and convert the metal oxide precursor tomore » metal oxide nanoparticles having the preselected morphology or to a metal oxide nanosheet including conjoined nanoparticles having the preselected morphology.« less

Characterization of Surface Modification of Polyethersulfone Membrane

USDA-ARS?s Scientific Manuscript database

Surface modification of polyethersulfone (PES) membrane surface using UV/ozone-treated grafting and interfacial polymerization on membrane surface was investigated in order to improve the resistance of membrane surface to protein adsorption. These methods of surface modification were compared in te...

A novel approach for UV-patterning with binary polymer brushes.

PubMed

Li, Lifu; Nakaji-Hirabayashi, Tadashi; Kitano, Hiromi; Ohno, Kohji; Saruwatari, Yoshiyuki; Matsuoka, Kazuyoshi

2018-01-01

A mixed self-assembled monolayer (SAM) of an initiator (3-(2-bromo-2-isobutyryloxy)propyl triethoxysilane) for atom transfer radical polymerization (ATRP) and an agent (6-(triethoxysilyl)hexyl 2-(((methylthio)carbonothioyl)thio)-2-phenylacetate) for reversible addition-fragmentation chain transfer (RAFT) polymerization was constructed on the surface of a silicon wafer or glass plate by a silane coupling reaction. When a UV light at 254nm was irradiated at the mixed SAM through a photomask, the surface density of the bromine atom at the end of BPE in the irradiated region was drastically reduced by UV-driven scission of the BrC bond, as observed by X-ray photoelectron spectroscopy. Consequently, the surface-initiated (SI)-ATRP of 2-ethylhexyl methacrylate (EHMA) was used to easily construct the poly(EHMA) (PEHMA) brush domain. Subsequently, SI-RAFT polymerization of a zwitterionic vinyl monomer, carboxymethyl betaine (CMB), was performed. Using the sequential polymerization, the PCMB and PEHMA brush domains on the solid substrate could be very easily patterned. Patterning proteins and cells with the binary polymer brush is expected because the PCMB brush indicated strong suppression of protein adsorption and cell adhesion, and the PEHMA brush had non-polar properties. This technique is very simple and useful for regulating the shape and size of bio-fouling and anti-biofouling domains on solid surfaces. Copyright © 2017 Elsevier B.V. All rights reserved.

Universal Surface-initiated Polymerization of Antifouling Zwitterionic Brushes Using A Mussel-Mimetic Peptide Initiator

PubMed Central

Kuang, Jinghao; Messersmith, Phillip B.

2012-01-01

We report a universal method for the surface-initated polymerization (SIP) of a antifouling polymer brush on various classes of surfaces, including noble metals, metal oxides and inert polymers. Inspired by the versatility of mussel adhesive proteins, we synthesized a novel bifunctional tripeptide bromide (BrYKY) which combines an atom transfer radical polymerization (ATRP) initiating alkyl bromide with l-3,4-dihydroxyphenylalanine (DOPA) and lysine. Simple dip-coating of substrates with variable wetting properties and compositions, including Teflon®, in a BrYKY solution at pH 8.5 led to formation of a thin film of cross-linked BrYKY. Subsequently, we showed that the BrYKY layer initiated the ATRP of a zwitterionic monomer, sulfobetaine methacrylate (SBMA) on all substrates, resulting in high density antifouling pSBMA brushes. Both BrYKY deposition and pSBMA grafting were unambiguously confirmed by ellipsometry, X-ray photoelectron spectroscopy and goniometry. All substrates that were coated with BrYKY/pSBMA dramatically reduced bacterial adhesion for 24 h and also resisted mammalian cell adhesion for at least 4 months, demonstrating the long-term stability of the BrYKY anchoring and antifouling properties of pSBMA. The use of BrYKY as a primer and polymerization initiator has the potential to be widely employed in surface grafted polymer brush modifications for biomedical and other applications. PMID:22506651

Effect of sodium hypochlorite and peracetic acid on the surface roughness of acrylic resin polymerized by heated water for short and long cycles.

PubMed

Sczepanski, Felipe; Sczepanski, Claudia Roberta Brunnquell; Berger, Sandrine Bittencourt; Consani, Rafael Leonardo Xediek; Gonini-Júnior, Alcides; Guiraldo, Ricardo Danil

2014-10-01

To evaluate the surface roughness of acrylic resin submitted to chemical disinfection via 1% sodium hypochlorite (NaClO) or 1% peracetic acid (C2H4O3). The disc-shaped resin specimens (30 mm diameter ×4 mm height) were polymerized by heated water using two cycles (short cycle: 1 h at 74°C and 30 min at 100°C; conventional long cycle: 9 h at 74°C). The release of substances by these specimens in water solution was also quantified. Specimens were fabricated, divided into four groups (n = 10) depending on the polymerization time and disinfectant. After polishing, the specimens were stored in distilled deionized water. Specimens were immersed in 1% NaClO or 1% C2H4O3 for 30 min, and then were immersed in distilled deionized water for 20 min. The release of C2H4O3 and NaClO was measured via visual colorimetric analysis. Roughness was measured before and after disinfection. Roughness data were subjected to two-way ANOVA and Tukey's test. There was no interaction between polymerization time and disinfectant in influencing the average surface roughness (Ra, P = 0.957). Considering these factors independently, there were significant differences between short and conventional long cycles (P = 0.012), but no significant difference between the disinfectants hypochlorite and C2H4O3 (P = 0.366). Visual colorimetric analysis did not detect release of substances. It was concluded that there was the difference in surface roughness between short and conventional long cycles, and disinfection at acrylic resins polymerized by heated water using a short cycle modified the properties of roughness.

Effect of sodium hypochlorite and peracetic acid on the surface roughness of acrylic resin polymerized by heated water for short and long cycles

PubMed Central

Sczepanski, Felipe; Sczepanski, Claudia Roberta Brunnquell; Berger, Sandrine Bittencourt; Consani, Rafael Leonardo Xediek; Gonini-Júnior, Alcides; Guiraldo, Ricardo Danil

2014-01-01

Objective: To evaluate the surface roughness of acrylic resin submitted to chemical disinfection via 1% sodium hypochlorite (NaClO) or 1% peracetic acid (C2H4O3). Materials and Methods: The disc-shaped resin specimens (30 mm diameter ×4 mm height) were polymerized by heated water using two cycles (short cycle: 1 h at 74°C and 30 min at 100°C; conventional long cycle: 9 h at 74°C). The release of substances by these specimens in water solution was also quantified. Specimens were fabricated, divided into four groups (n = 10) depending on the polymerization time and disinfectant. After polishing, the specimens were stored in distilled deionized water. Specimens were immersed in 1% NaClO or 1% C2H4O3 for 30 min, and then were immersed in distilled deionized water for 20 min. The release of C2H4O3 and NaClO was measured via visual colorimetric analysis. Roughness was measured before and after disinfection. Roughness data were subjected to two-way ANOVA and Tukey's test. Results: There was no interaction between polymerization time and disinfectant in influencing the average surface roughness (Ra, P = 0.957). Considering these factors independently, there were significant differences between short and conventional long cycles (P = 0.012), but no significant difference between the disinfectants hypochlorite and C2H4O3 (P = 0.366). Visual colorimetric analysis did not detect release of substances. Conclusion: It was concluded that there was the difference in surface roughness between short and conventional long cycles, and disinfection at acrylic resins polymerized by heated water using a short cycle modified the properties of roughness. PMID:25512737

Polymethyl methacrylate-co-methacrylic acid coatings with controllable concentration of surface carboxyl groups: A novel approach in fabrication of polymeric platforms for potential bio-diagnostic devices

NASA Astrophysics Data System (ADS)

Hosseini, Samira; Ibrahim, Fatimah; Djordjevic, Ivan; Koole, Leo H.

2014-05-01

The generally accepted strategy in development of bio-diagnostic devices is to immobilize proteins on polymeric surfaces as a part of detection process for diseases and viruses through antibody/antigen coupling. In that perspective, polymer surface properties such as concentration of functional groups must be closely controlled in order to preserve the protein activity. In order to improve the surface characteristics of transparent polymethacrylate plastics that are used for diagnostic devices, we have developed an effective fabrication procedure of polymethylmetacrylate-co-metacrylic acid (PMMA-co-MAA) coatings with controlled number of surface carboxyl groups. The polymers were processed effectively with the spin-coating technique and the detailed control over surface properties is here by demonstrated through the variation of a single synthesis reaction parameter. The chemical structure of synthesized and processed co-polymers has been investigated with nuclear magnetic resonance spectroscopy (NMR) and matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-ToF-MS). The surface morphology of polymer coatings have been analyzed with atomic force microscopy (AFM) and scanning electron microscopy (SEM). We demonstrate that the surface morphology and the concentration of surface -COOH groups (determined with UV-vis surface titration) on the processed PMMA-co-MAA coatings can be precisely controlled by variation of initial molar ratio of reactants in the free-radical polymerization reaction. The wettability of developed polymer surfaces also varies with macromolecular structure.

3D full field strain analysis of polymerization shrinkage in a dental composite.

PubMed

Martinsen, Michael; El-Hajjar, Rani F; Berzins, David W

2013-08-01

The objective of this research was to study the polymerization shrinkage in a dental composite using 3D digital image correlation (DIC). Using 2 coupled cameras, digital images were taken of bar-shaped composite (Premise Universal Composite; Kerr) specimens before light curing and after for 10 min. Three-dimensional DIC was used to assess in-plane and out-of-plane deformations associated with polymerization shrinkage. The results show the polymerization shrinkage to be highly variable with the peak values occurring 0.6-0.8mm away from the surface. Volumetric shrinkage began to significantly decrease at 3.2mm from the specimen surface and reached a minimum at 4mm within the composite. Approximately 25-30% of the strain registered at 5 min occurred after light-activation. Application of 3D DIC dental applications can be performed without the need for assumptions on the deformation field. Understanding the local deformations and strain fields from the initial polymerization shrinkage can lead to a better understanding of the composite material and interaction with surrounding tooth structure, aiding in their further development and clinical prognosis. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Bactericidal Specificity and Resistance Profile of Poly(Quaternary Ammonium) Polymers and Protein-Poly(Quaternary Ammonium) Conjugates.

PubMed

Ji, Weihang; Koepsel, Richard R; Murata, Hironobu; Zadan, Sawyer; Campbell, Alan S; Russell, Alan J

2017-08-14

Antibacterial polymers are potentially powerful biocides that can destroy bacteria on contact. Debate in the literature has surrounded the mechanism of action of polymeric biocides and the propensity for bacteria to develop resistance to them. There has been particular interest in whether surfaces with covalently coupled polymeric biocides have the same mechanism of action and resistance profile as similar soluble polymeric biocides. We designed and synthesized a series of poly(quaternary ammonium) polymers, with tailorable molecular structures and architectures, to engineer their antibacterial specificity and their ability to delay the development of bacterial resistance. These linear poly(quaternary ammonium) homopolymers and block copolymers, generated using atom transfer radical polymerization, had structure-dependent antibacterial specificity toward Gram positive and negative bacterial species. When single block copolymers contained two polymer segments of differing antibacterial specificity, the polymer combined the specificities of its two components. Nanoparticulate human serum albumin-poly(quaternary ammonium) conjugates of these same polymers, synthesized via "grafting from" atom transfer radical polymerization, were strongly biocidal and also exhibited a marked decrease in the rate of bacterial resistance development relative to linear polymers. These protein-biocide conjugates mimicked the behavior of surface-presented polycationic biocides rather than their nonproteinaceous counterparts.

Multi-functional Textiles for Military Applications

NASA Astrophysics Data System (ADS)

Malshe, Priyadarshini

The objective of this research was to develop the standard rip-stop weave military uniform fabric made of 50/50 nylon/cotton (NyCo) to achieve a repellent front surface and an antibacterial bulk for protection from chemical-biological warfare agents. Diallyldimethylammonium chloride (DADMAC), a quaternary ammonium salt monomer was graft polymerized on NyCo fabric to impart antimicrobial capability using atmospheric pressure glow discharge plasma. Plasma was used to induce free radical chain polymerization of the DADMAC monomer to introduce a graft polymerized network on the fabric with durable antimicrobial properties. Pentaerythritol tertraacrylate was used as a cross-linking agent to obtain a highly cross-linked, durable polymer network. The presence of polyDADMAC on the fabric surface was confirmed using acid dye staining, SEM, and TOF-SIMS. Antibacterial performance was evaluated using standard AATCC test method 100 for both gram positive and gram negative bacteria. Results showed 99.9% reduction in the bacterial activities of K. pneumoniae and S. aureus. To achieve repellency on NyCo front surface, an environmentally benign C6 fluorocarbon monomer, 2-(perfluorohexyl) ethyl acrylate was graft polymerized using plasma on the front surface of the NyCo fabric which was already grafted with polyDADMAC for anti-microbial properties. The surface was characterized by IR spectroscopy and XPS. The presence of fluorine on the surface was mapped and confirmed by TOF-SIMS. SEM images showed a uniform layer of fluorocarbon polymer on the fiber surface. High water contact angle of 144° was obtained on the surface. The surface also achieved a high AATCC Test Method 193 rating of 9 and AATCC Test Method 118 rating of 5, indicating that the surface could repel a fluid with surface tension as low as 24 dynes/cm. Appropriate experimental designs and statistical modeling of data helped identify the experimental space and optimal factor combinations for best response. The study helped create a multi-functional fabric with an anti-bacterial bulk, hydrophilic back surface and repellent front surface for enhanced protective and aesthetic values.

Iodine versus Bromine Functionalization for Bottom-Up Graphene Nanoribbon Growth: Role of Diffusion

DOE PAGES

Bronner, Christopher; Marangoni, Tomas; Rizzo, Daniel J.; ...

2017-08-08

Deterministic bottom-up approaches for synthesizing atomically well-defined graphene nanoribbons (GNRs) largely rely on the surface-catalyzed activation of selected labile bonds in a molecular precursor followed by step-growth polymerization and cyclodehydrogenation. While the majority of successful GNR precursors rely on the homolytic cleavage of thermally labile C–Br bonds, the introduction of weaker C–I bonds provides access to monomers that can be polymerized at significantly lower temperatures, thus helping to increase the flexibility of the GNR synthesis process. Scanning tunneling microscopy imaging of molecular precursors, activated intermediates, and polymers resulting from stepwise thermal annealing of both Br and I substituted precursors formore » chevron GNRs reveals that the polymerization of both precursors proceeds at similar temperatures on Au(111). Finally, this surprising observation is consistent with diffusion-controlled polymerization of the surface-stabilized radical intermediates that emerge from homolytic cleavage of either the C–Br or the C–I bonds.« less

Localized in situ polymerization on graphene surfaces for stabilized graphene dispersions.

PubMed

Das, Sriya; Wajid, Ahmed S; Shelburne, John L; Liao, Yen-Chih; Green, Micah J

2011-06-01

We demonstrate a novel in situ polymerization technique to develop localized polymer coatings on the surface of dispersed pristine graphene sheets. Graphene sheets show great promise as strong, conductive fillers in polymer nanocomposites; however, difficulties in dispersion quality and interfacial strength between filler and matrix have been a persistent problem for graphene-based nanocomposites, particularly for pristine graphene. With this in mind, a physisorbed polymer layer is used to stabilize graphene sheets in solution. To create this protective layer, we formed an organic microenvironment around dispersed graphene sheets in surfactant solutions, and created a nylon 6, 10 or nylon 6, 6 coating via interfacial polymerization. Technique lies at the intersection of emulsion and admicellar polymerization; a similar technique was originally developed to protect luminescent properties of carbon nanotubes in solution. These coated graphene dispersions are aggregation-resistant and may be reversibly redispersed in water even after freeze-drying. The coated graphene holds promise for a number of applications, including multifunctional graphene-polymer nanocomposites. © 2011 American Chemical Society

Preparation of polymethacrylic acid-grafted HEMA/PVP microspheres and preliminary study on basic protein adsorption.

PubMed

Gao, Baojiao; Hu, Hongyan; Guo, Jianfeng; Li, Yanbin

2010-06-01

The crosslinked copolymeric microspheres (HEMA/NVP) of N-vinylpyrrolidone (NVP) and 2-hydroxyethyl methacrylate (HEMA) were prepared using inverse suspension polymerization method. Subsequently, the reaction of methacryloyl chloride with the hydroxyl groups on the surfaces of HEMA/NVP microspheres was performed, leading to the introduction of polymerisable double bonds onto the surfaces of microspheres HEMA/NVP. Afterward, methacrylic acid was allowed to be graft-polymerized on microspheres HEMA/NVP in the manner of "grafting from", resulting in the grafted microspheres PMAA-HEMA/NVP. The grafted microspheres PMAA-HEMA/NVP were fully characterized with several means. The graft-polymerization of MAA on microspheres HEMA/NVP was studied in detail, and the optimal reaction conditions were determined. Thereafter, the adsorption property of the grafted microspheres PMAA-HEMA/NVP for lysozyme as a basic protein model was preliminarily examined to explore the feasibility of removing deleterious basic protein such as density lipoprotein from blood. The experimental results indicate that the PMAA grafting degree on microspheres HEMA/NVP is limited because an enwinding polymer layer as a kinetic barrier on the surfaces of HEMA/NVP microspheres will be formed during the graft-polymerization, and block the graft-polymerization. In order to enhance PMAA grafting degree, reaction temperature, monomer concentration and the used amount of initiator should be effectively controlled. The experimental results also reveal that the grafted microspheres PMAA-HEMA/NVP possess very strong adsorption ability for lysozyme by right of strong electrostatic interaction. Copyright 2010 Elsevier B.V. All rights reserved.

Preparation of a polymeric ionic liquid-coated solid-phase microextraction fiber by surface radical chain-transfer polymerization with stainless steel wire as support.

PubMed

Feng, Juanjuan; Sun, Min; Xu, Lili; Li, Jubai; Liu, Xia; Jiang, Shengxiang

2011-10-28

Polymeric 1-vinyl-3-octylimidazolium hexafluorophosphate was synthesized in situ on stainless steel wire by surface radical chain-transfer polymerization and used as sensitive coatings in solid-phase microextraction. The outer surface of the stainless steel wire was firstly coated with microstructured silver layer via silver mirror reaction and then functionalized with self-assembled monolayers of 1,8-octanedithiol, which acted as chain transfer agent in the polymerization. Coupled to gas chromatography, extraction performance of the fiber was studied with both headspace and direct-immersion modes using benzene, toluene, ethylbenzene and xylenes (BTEX), phenols and polycyclic aromatic hydrocarbon (PAHs) as model analytes. In combination with the microstructured silver layer, the PIL-coated fiber exhibited high extraction efficiency. Linear ranges for BTEX with headspace mode were in the range of 0.2-1000 μg L(-1) for benzene, and 0.1-1000 μg L(-1) for toluene, ethylbenzene and xylenes. Limits of detection (LODs) were from 0.02 to 0.05 μg L(-1). Wide linear ranges of direct-immersion mode for the extraction of several phenols and PAHs were also obtained with correlation coefficients (R) from 0.9943 to 0.9997. The proposed fiber showed good durability with long lifetime. RSDs of 56 times extraction were still in an acceptable range, from 8.85 to 22.8%. Copyright © 2011 Elsevier B.V. All rights reserved.

Atomic Oxygen Textured Polymers

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; Rutledge, Sharon K.; Hunt, Jason D.; Drobotij, Erin; Cales, Michael R.; Cantrell, Gidget

1995-01-01

Atomic oxygen can be used to microscopically alter the surface morphology of polymeric materials in space or in ground laboratory facilities. For polymeric materials whose sole oxidation products are volatile species, directed atomic oxygen reactions produce surfaces of microscopic cones. However, isotropic atomic oxygen exposure results in polymer surfaces covered with lower aspect ratio sharp-edged craters. Isotropic atomic oxygen plasma exposure of polymers typically causes a significant decrease in water contact angle as well as altered coefficient of static friction. Such surface alterations may be of benefit for industrial and biomedical applications. The results of atomic oxygen plasma exposure of thirty-three (33) different polymers are presented, including typical morphology changes, effects on water contact angle, and coefficient of static friction.

Algorithmes de couplage RANS et ecoulement potentiel

NASA Astrophysics Data System (ADS)

Gallay, Sylvain

Dans le processus de developpement d'avion, la solution retenue doit satisfaire de nombreux criteres dans de nombreux domaines, comme par exemple le domaine de la structure, de l'aerodynamique, de la stabilite et controle, de la performance ou encore de la securite, tout en respectant des echeanciers precis et minimisant les couts. Les geometries candidates sont nombreuses dans les premieres etapes de definition du produit et de design preliminaire, et des environnements d'optimisations multidisciplinaires sont developpes par les differentes industries aeronautiques. Differentes methodes impliquant differents niveaux de modelisations sont necessaires pour les differentes phases de developpement du projet. Lors des phases de definition et de design preliminaires, des methodes rapides sont necessaires afin d'etudier les candidats efficacement. Le developpement de methodes ameliorant la precision des methodes existantes tout en gardant un cout de calcul faible permet d'obtenir un niveau de fidelite plus eleve dans les premieres phases de developpement du projet et ainsi grandement diminuer les risques associes. Dans le domaine de l'aerodynamisme, les developpements des algorithmes de couplage visqueux/non visqueux permettent d'ameliorer les methodes de calcul lineaires non visqueuses en methodes non lineaires prenant en compte les effets visqueux. Ces methodes permettent ainsi de caracteriser l'ecoulement visqueux sur les configurations et predire entre autre les mecanismes de decrochage ou encore la position des ondes de chocs sur les surfaces portantes. Cette these se focalise sur le couplage entre une methode d'ecoulement potentiel tridimensionnelle et des donnees de section bidimensionnelles visqueuses. Les methodes existantes sont implementees et leurs limites identifiees. Une methode originale est ensuite developpee et validee. Les resultats sur une aile elliptique demontrent la capacite de l'algorithme a de grands angles d'attaques et dans la region post-decrochage. L'algorithme de couplage a ete compare a des donnees de plus haute fidelite sur des configurations issues de la litterature. Un modele de fuselage base sur des relations empiriques et des simulations RANS a ete teste et valide. Les coefficients de portance, de trainee et de moment de tangage ainsi que les coefficients de pression extraits le long de l'envergure ont montre un bon accord avec les donnees de soufflerie et les modeles RANS pour des configurations transsoniques. Une configuration a geometrie hypersustentatoire a permis d'etudier la modelisation des surfaces hypersustentees de la methode d'ecoulement potentiel, demontrant que la cambrure peut etre prise en compte uniquement dans les donnees visqueuses.

Adsorption and electron-induced polymerization of methyl methacrylate on Ru(101xAF0)

NASA Astrophysics Data System (ADS)

Hedhili, M. N.; Yakshinskiy, B. V.; Wasielewski, R.; Ciszewski, A.; Madey, T. E.

2008-05-01

The adsorption and electron irradiation of methyl methacrylate (MMA) on a Ru(101¯0) surface have been studied using x-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), and low energy ion scattering. TPD analysis indicates that a monolayer of MMA chemisorbs and dissociates on the Ru(101¯0) surface. The reaction products observed upon heating include H2, CO, CO2, and a small amount of MMA. Physisorbed multilayers of MMA desorb at temperatures around 170K. Electron irradiation of physisorbed MMA at 140K leads to a modification of the MMA film: The XPS spectra show an increase in thermal stability of the film with retention of the MMA structure, and indicate that electron irradiation induces polymerization. An increase in the electron bombardment fluence induces a degradation of the formed polymerized species and leads to the accumulation of carbon on the Ru surface. These results are relevant to the accumulation of carbon on surfaces of Ru films that serve as capping layers on Mo /Si multilayer mirrors used in extreme ultraviolet lithography.

CAD/CAM milled complete removable dental prostheses: An in vitro evaluation of biocompatibility, mechanical properties, and surface roughness.

PubMed

Srinivasan, Murali; Gjengedal, Harald; Cattani-Lorente, Maria; Moussa, Mira; Durual, Stéphane; Schimmel, Martin; Müller, Frauke

2018-03-06

This study compared the biocompatibility, mechanical properties, and surface roughness of a pre-polymerized polymethyl methacrylate (PMMA) resin for CAD/CAM complete removable dental prostheses (CRDPs) and a traditional heat-polymerized PMMA resin. Two groups of resin substrates [Control (RC): conventional PMMA; Test (RA): CAD/CAM PMMA] were fabricated. Human primary osteoblasts and mouse embryonic-fibroblasts were cultured for biocompatibility assays. Mechanical properties and surface roughness were compared. ANOVA revealed no difference between the resin groups in the biocompatibility assays. RA demonstrated a higher elastic modulus (p=0.002), young's modulus (p=0.002), plastic energy (p=0.002), ultimate strength (p=0.0004), yield point (p=0.016), strain at yield point (p=0.037), and toughness (p<0.0001); while RC displayed a higher elastic energy (p<0.0001). Laser profilometry concluded a rougher surface profile (p<0.0001) for RA. This study concluded that the tested CAD/CAM resin was equally biocompatible and presented with improved mechanical properties than the traditional heat-polymerized PMMA resin used in the fabrication of CRDPs.

Releasing the brakes while hanging on: Cortactin effects on actin-driven motility.

PubMed

Gov, Nir S; Bernheim-Groswasser, Anne

2012-01-01

Actin polymerization plays a major role in many cellular processes, including cell motility, vesicle trafficking, and pathogen propulsion. The transformation of the (protrusive) polymerization forces into directed motion requires that the growing filaments are positioned next to the surface. This is achieved by localization of surface actin nucleators (WASP), which then activate Arp2/3 complex to form new actin branches. Yet, the same surface-bound WASP molecule which initiates the nucleation of new actin branches, also inherently prevents the translation of the polymerization forces into motion, essentially because the WASP molecule has to be in contact with the network during the formation of the new branch. In our recent paper we show that cortactin relaxes this internal inhibition by enhancing the release of WASP-VCA molecule from the new branching site after nucleation is initiated. We show that this enhanced release has two major effects; it increases the turnover rate of branching per WASP molecule, and it decreases the friction-like force caused by the binding of the moving surface with respect to the growing actin network.

Rapidly-Deposited Polydopamine Coating via High Temperature and Vigorous Stirring: Formation, Characterization and Biofunctional Evaluation

PubMed Central

Zhou, Ping; Deng, Yi; Lyu, Beier; Zhang, Ranran; Zhang, Hai; Ma, Hongwei; Lyu, Yalin; Wei, Shicheng

2014-01-01

Polydopamine (PDA) coating provides a promising approach for immobilization of biomolecules onto almost all kinds of solid substrates. However, the deposition kinetics of PDA coating as a function of temperature and reaction method is not well elucidated. Since dopamine self-polymerization usually takes a long time, therefore, rapid-formation of PDA film becomes imperative for surface modification of biomaterials and medical devices. In the present study, a practical method for preparation of rapidly-deposited PDA coating was developed using a uniquely designed device, and the kinetics of dopamine self-polymerization was investigated by QCM sensor system. It was found that high temperature and vigorous stirring could dramatically speed up the formation of PDA film on QCM chip surface. Surface characterization, BSA binding study, cell viability assay and antibacterial test demonstrates that the polydopamine coating after polymerization for 30 min by our approach exhibits similar properties to those of 24 h counterpart. The method has a great potential for rapid-deposition of polydopamine films to modify biomaterial surfaces. PMID:25415328

Plasma Surface Modification for Immobilization of Bone Morphogenic Protein-2 on Polycaprolactone Scaffolds

NASA Astrophysics Data System (ADS)

Kim, Byung Hoon; Myung, Sung Woon; Jung, Sang Chul; Ko, Yeong Mu

2013-11-01

The immobilization of recombinant human bone formation protein-2 (rhBMP-2) on polycaprolactone (PCL) scaffolds was performed by plasma polymerization. RhBMP-2, which induces osteoblast differentiation in various cell types, is a growth factor that plays an important role in bone formation and repair. The surface of the PCL scaffold was functionalized with the carboxyl groups of plasma-polymerized acrylic acid (PPAA) thin films. Plasma polymerization was carried out at a discharge power of 60 W at an acrylic acid flow rate of 7 sccm for 5 min. The PPAA thin film exhibited moderate hydrophilic properties and possessed a high density of carboxyl groups. Carboxyl groups and rhBMP-2 on the PCL scaffolds surface were identified by attenuated total reflection Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, respectively. The alkaline phosphatase activity assay showed that the rhBMP-2 immobilized PCL scaffold increased the level of MG-63 cell differentiation. Plasma surface modification for the preparation of biomaterials, such as biofunctionalized polymer scaffolds, can be used for the binding of bioactive molecules in tissue engineering.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinez, Andre P.; Carrillo, Jan-Michael Y.; Dobrynin, Andrey V.

The molecular weight and polydispersity of the chains in a polymer brush are critical parameters determining the brush properties. However, the characterization of polymer brushes is hindered by the vanishingly small mass of polymer present in brush layers. In this study, in order to obtain sufficient quantities of polymer for analysis, polymer brushes were grown from high surface area fibrous nylon membranes by ATRP. We synthesized the brushes with varying surface initiator densities, polymerization times, and amounts of sacrificial initiator, then cleaved from the substrate, and analyzed by GPC and NMR. Characterization showed that the surface-grown polymer chains were moremore » polydisperse and had lower average molecular weight compared to solution-grown polymers synthesized concurrently. Furthermore, the molecular weight distribution of the polymer brushes was observed to be bimodal, with a low molecular weight population of chains representing a significant mass fraction of the polymer chains at high surface initiator densities. Moreover, the origin of this low MW polymer fraction is proposed to be the termination of growing chains by recombination during the early stages of polymerization, a mechanism confirmed by molecular dynamics simulations of brush polymerization.« less

Bacterial adhesion on conventional and self-ligating metallic brackets after surface treatment with plasma-polymerized hexamethyldisiloxane

PubMed Central

Tupinambá, Rogerio Amaral; Claro, Cristiane Aparecida de Assis; Pereira, Cristiane Aparecida; Nobrega, Celestino José Prudente; Claro, Ana Paula Rosifini Alves

2017-01-01

ABSTRACT Introduction: Plasma-polymerized film deposition was created to modify metallic orthodontic brackets surface properties in order to inhibit bacterial adhesion. Methods: Hexamethyldisiloxane (HMDSO) polymer films were deposited on conventional (n = 10) and self-ligating (n = 10) stainless steel orthodontic brackets using the Plasma-Enhanced Chemical Vapor Deposition (PECVD) radio frequency technique. The samples were divided into two groups according to the kind of bracket and two subgroups after surface treatment. Scanning Electron Microscopy (SEM) analysis was performed to assess the presence of bacterial adhesion over samples surfaces (slot and wings region) and film layer integrity. Surface roughness was assessed by Confocal Interferometry (CI) and surface wettability, by goniometry. For bacterial adhesion analysis, samples were exposed for 72 hours to a Streptococcus mutans solution for biofilm formation. The values obtained for surface roughness were analyzed using the Mann-Whitney test while biofilm adhesion were assessed by Kruskal-Wallis and SNK test. Results: Significant statistical differences (p< 0.05) for surface roughness and bacterial adhesion reduction were observed on conventional brackets after surface treatment and between conventional and self-ligating brackets; no significant statistical differences were observed between self-ligating groups (p> 0.05). Conclusion: Plasma-polymerized film deposition was only effective on reducing surface roughness and bacterial adhesion in conventional brackets. It was also noted that conventional brackets showed lower biofilm adhesion than self-ligating brackets despite the absence of film. PMID:28902253

Characteristics of low polymerization shrinkage flowable resin composites in newly-developed cavity base materials for bulk filling technique.

PubMed

Nitta, Keiko; Nomoto, Rie; Tsubota, Yuji; Tsuchikawa, Masuji; Hayakawa, Tohru

2017-11-29

The purpose of this study was to evaluate polymerization shrinkage and other physical properties of newly-developed cavity base materials for bulk filling technique, with the brand name BULK BASE (BBS). Polymerization shrinkage was measured according to ISO/FDIS 17304. BBS showed the significantly lowest polymerization shrinkage and significantly higher depth of cure than conventional flowable resin composites (p<0.05). The Knoop hardness, flexural strength and elastic modulus of that were significantly lower than conventional flowable resin composites (p<0.05). BBS had the significantly greatest filler content (p<0.05). SEM images of the surface showed failure of fillers. The lowest polymerization shrinkage was due to the incorporation of a new type of low shrinkage monomer, which has urethane moieties. There were no clear correlations between inorganic filler contents and polymerization shrinkage, flexural strength and elastic modulus. In conclusion, the low polymerization shrinkage of BBS will be useful for cavity treatment in dental clinics.

Polymeric Janus Nanoparticles: Recent Advances in Synthetic Strategies, Materials Properties, and Applications.

PubMed

Fan, Xiaoshan; Yang, Jing; Loh, Xian Jun; Li, Zibiao

2018-06-13

Polymeric Janus nanoparticles with two sides of incompatible chemistry have received increasing attention due to their tunable asymmetric structure and unique material characteristics. Recently, with the rapid progress in controlled polymerization combined with novel fabrication techniques, a large array of functional polymeric Janus particles are diversified with sophisticated architecture and applications. In this review, the most recently developed strategies for controlled synthesis of polymeric Janus nanoparticles with well-defined size and complex superstructures are summarized. In addition, the pros and cons of each approach in mediating the anisotropic shapes of polymeric Janus particles as well as their asymmetric spatial distribution of chemical compositions and functionalities are discussed and compared. Finally, these newly developed structural nanoparticles with specific shapes and surface functions orientated applications in different domains are also discussed, followed by the perspectives and challenges faced in the further advancement of polymeric Janus nanoparticles as high performance materials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Supported metallocene catalysts by surface organometallic chemistry. Synthesis, characterization, and reactivity in ethylene polymerization of oxide-supported mono- and biscyclopentadienyl zirconium alkyl complexes: establishment of structure/reactivity relationships.

PubMed

Jezequel, M; Dufaud, V; Ruiz-Garcia, M J; Carrillo-Hermosilla, F; Neugebauer, U; Niccolai, G P; Lefebvre, F; Bayard, F; Corker, J; Fiddy, S; Evans, J; Broyer, J P; Malinge, J; Basset, J M

2001-04-18

The reactions of CpZr(CH(3))(3), 1, and Cp(2)Zr(CH(3))(2), 2, with partially dehydroxylated silica, silica-alumina, and alumina surfaces have been carried out with careful identification of the resulting surface organometallic complexes in order to probe the relationship between catalyst structure and polymerization activity. The characterization of the supported complexes has been achieved in most cases by in situ infrared spectroscopy, surface microanalysis, qualitative and quantitative analysis of evolved gases during surface reactions with labeled surface, solid state (1)H and (13)C NMR using (13)C-enriched compounds, and EXAFS. 1 and 2 react with silica(500) and silica-alumina(500) by simple protonolysis of one Zr-Me bond by surface silanols with formation of a single well-defined neutral compound. In the case of silica-alumina, a fraction of the supported complexes exhibits some interactions with electronically unsaturated surface aluminum sites. 1 and 2 also react with the hydroxyl groups of gamma-alumina(500), leading to several surface structures. Correlation between EXAFS and (13)C NMR data suggests, in short, two main surface structures having different environments for the methyl group: [Al](3)-OZrCp(CH(3))(2) and [Al](2)-OZrCp(CH(3))(mu-CH(3))-[Al] for the monoCp series and [Al](2)-OZrCp(2)(CH(3)) and [Al]-OZrCp(2)(mu-CH(3))-[Al] for the bisCp series. Ethylene polymerization has been carried out with all the supported complexes under various reaction conditions. Silica-supported catalysts in the absence of any cocatalyst exhibited no activity whatsoever for ethylene polymerization. When the oxide contained Lewis acidic sites, the resulting surface species were active. The activity, although improved by the presence of additional cocatalysts, remained very low by comparison with that of the homogeneous metallocene systems. This trend has been interpreted on the basis of various possible parameters, including the (p-pi)-(d-pi) back-donation of surface oxygen atoms to the zirconium center.

Polymeric surfaces exhibiting photocatalytic activity and controlled anisotropic wettability

NASA Astrophysics Data System (ADS)

Anastasiadis, Spiros H.; Frysali, Melani A.; Papoutsakis, Lampros; Kenanakis, George; Stratakis, Emmanuel; Vamvakaki, Maria; Mountrichas, Grigoris; Pispas, Stergios

2015-03-01

In this work we focus on surfaces, which exhibit controlled, switchable wettability in response to one or more external stimuli as well as photocatalytic activity. For this we are inspired from nature to produce surfaces with a dual-scale hierarchical roughness and combine them with the appropriate inorganic and/or polymer coating. The combination of the hierarchical surface with a ZnO coating and a pH- or temperature-responsive polymer results in efficient photo-active properties as well as reversible superhydrophobic / superhydrophilic surfaces. Furthermore, we fabricate surfaces with unidirectional wettability variation. Overall, such complex surfaces require advanced design, combining hierarchically structured surfaces with suitable polymeric materials. Acknowledgment: This research was partially supported by the European Union (European Social Fund, ESF) and Greek national funds through the ``ARISTEIA II'' Action (SMART-SURF) of the Operational Programme ``Education and Lifelong Learning,'' NSRF 2007-2013, via the General Secretariat for Research & Technology, Ministry of Education and Religious Affairs, Greece.

Nano-interconnection for microelectronics and polymers with benzo-triazole

NASA Technical Reports Server (NTRS)

Park, Yeonjoon; Choi, Sang H.; Noh, Hyunpil; Kuk, Young

2006-01-01

Benzo-Triazole (BTA) is considered as an important bridging material that can connect an organic polymer to the metal electrode on silicon wafers as a part of the microelectronics fabrication technology. We report a detailed process of surface induced 3-D polymerization of BTA on the Cu electrode material which was measured with the Ultraviolet Photoemission Spectroscopy (UPS), X-ray Photoemission Spectroscopy (XPS), and Scanning Tunneling Microscope (STM). The electric utilization of shield and chain polymerization of BTA on Cu surface is contemplated in this study.

Targeted polymeric nanoparticles for cancer gene therapy

PubMed Central

Kim, Jayoung; Wilson, David R.; Zamboni, Camila G.; Green, Jordan J.

2015-01-01

In this article, advances in designing polymeric nanoparticles for targeted cancer gene therapy are reviewed. Characterization and evaluation of biomaterials, targeting ligands, and transcriptional elements are each discussed. Advances in biomaterials have driven improvements to nanoparticle stability and tissue targeting, conjugation of ligands to the surface of polymeric nanoparticles enable binding to specific cancer cells, and the design of transcriptional elements has enabled selective DNA expression specific to the cancer cells. Together, these features have improved the performance of polymeric nanoparticles as targeted non-viral gene delivery vectors to treat cancer. As polymeric nanoparticles can be designed to be biodegradable, non-toxic, and to have reduced immunogenicity and tumorigenicity compared to viral platforms, they have significant potential for clinical use. Results of polymeric gene therapy in clinical trials and future directions for the engineering of nanoparticle systems for targeted cancer gene therapy are also presented. PMID:26061296

Biodegradable polymeric microsphere-based vaccines and their applications in infectious diseases.

PubMed

Lin, Chi-Ying; Lin, Shih-Jie; Yang, Yi-Chen; Wang, Der-Yuan; Cheng, Hwei-Fang; Yeh, Ming-Kung

2015-01-01

Vaccination, which provides effective, safe infectious disease protection, is among the most important recent public health and immunological achievements. However, infectious disease remains the leading cause of death in developing countries because several vaccines require repeated administrations and children are often incompletely immunized. Microsphere-based systems, providing controlled release delivery, can obviate the need for repeat immunizations. Here, we review the function of sustained and pulsatile release of biodegradable polymeric microspheres in parenteral and mucosal single-dose vaccine administration. We also review the active-targeting function of polymeric particles. With their shield and co-delivery functions, polymeric particles are applied to develop single-dose and mucosally administered vaccines as well as to improve subunit vaccines. Because polymeric particles are easily surface-modified, they have been recently used in vaccine development for cancers and many infectious diseases without effective vaccines (e.g., human immunodeficiency virus infection). These polymeric particle functions yield important vaccine carriers and multiple benefits.

The Triangle: a Multiprocessor Architecture for Fast Curve and Surface Generation.

DTIC Science & Technology

1987-08-01

design , curves and surfaces, graphics hardware. 20...curves, B-splines, computer-aided geometric design ; curves and sur- faces, graphics hardware. (k 12). -/ .... This work was supported in part by the...34 Electronic Design , October 30, 1986. 21. M. A. Penna and R. R. Patterson, Projective Geometry and its Applications to Computer Graphics , Prentice-Hall, Englewood Cliffs, N.J., 1985. 70,e, 41100vr -~ ~ - -- --

Polyelectrolyte brushes grafted from cellulose nanocrystals using Cu-mediated surface-initiated controlled radical polymerization.

PubMed

Majoinen, Johanna; Walther, Andreas; McKee, Jason R; Kontturi, Eero; Aseyev, Vladimir; Malho, Jani Markus; Ruokolainen, Janne; Ikkala, Olli

2011-08-08

Herein we report the synthesis of cellulose nanocrystals (CNCs) grafted with poly(acrylic acid) (PAA) chains of different lengths using Cu-mediated surface initiated-controlled radical polymerization (SI-CRP). First, poly(tert-butylacrylate) (PtBA) brushes were synthesized; then, subsequent acid hydrolysis was used to furnish PAA brushes tethered onto the CNC surfaces. The CNCs were chemically modified to create initiator moieties on the CNC surfaces using chemical vapor deposition (CVD) and continued in solvent phase in DMF. A density of initiator groups of 4.6 bromine ester groups/nm(2) on the CNC surface was reached, suggesting a dense functionalization and a promising starting point for the controlled/living radical polymerization. The SI-CRP of tert-butylacrylate proceeded in a well-controlled manner with the aid of added sacrificial initiator, yielding polymer brushes with polydispersity values typically well below 1.12. We calculated the polymer brush grafting density to almost 0.3 chains/nm(2), corresponding to high grafting densities and dense polymer brush formation on the nanocrystals. Successful rapid acid hydrolysis to remove the tert-butyl groups yielded pH-responsive PAA-polyelectrolyte brushes bound to the CNC surface. Individually dispersed rod-like nanoparticles with brushes of PtBA or PAA were clearly visualized by AFM and TEM imaging.

Competitive concurrence of surface wrinkling and dewetting of liquid crystalline polymer films on non-wettable substrates.

PubMed

Song, Sung E; Choi, Gwan H; Yi, Gi-Ra; Yoo, Pil J

2017-11-01

Polymeric thin films coated on non-wettable substrates undergo film-instabilities, which are usually manifested as surface deformation in the form of dewetting or wrinkling. The former takes place in fluidic films, whereas the latter occurs in solid films. Therefore, there have rarely been reports of systems involving simultaneous deformations of dewetting and wrinkling. In this study, we propose polymeric thin films of liquid crystalline (LC) mesogens prepared on a non-wettable Si substrate and apply a treatment of plasma irradiation to form a thin polymerized layer at the surface. The resulting compressive stress generated in the surface region drives the formation of wrinkles, while at the same time, dipolar attraction between LC molecules induces competitive cohesive dewetting. Intriguing surface structures were obtained whereby dewetting-like hole arrays are nested inside the randomly propagated wrinkles. The structural features are readily controlled by the degree of surface cross-linking, hydrophilicity of the substrates, and the LC film thickness. In particular, dewetting of LC mesogens is observed to be restricted to occur at the trough regions of wrinkles, exhibiting the typical behavior of geometrically confined dewetting. Finally, wrinkling-dewetting mixed structures are separated from the substrate in the form of free standing films to demonstrate the potential applicability as membranes.

Effet de la substitution du cuivre par du lithium sur les proprietes de l'oxyde spinelle lithium(x)cuivre(y-x)cobalt(3-y)oxygen(4) etudie pour l'electrocatalyse de la reaction de degagement de l'oxygene en milieu alcalin

NASA Astrophysics Data System (ADS)

Fatih, Khalid

L'electrolyse de l'eau demeure la seule technologie industrielle de generation de l'hydrogene et de l'oxygene tres purs sans rejet de CO2 dans l'atmosphere, ce qui le rend tres attrayant par rapport a la combustion de carburants fossiles qui provoque presentement de serieux problemes environnementaux. Dans le but d'ameliorer le rendement de ce procede, nous avons developpe de nouveaux materiaux d'anode peu couteux, a base de l'oxyde mixte CuyCo3-yO 4, qui possedent une cinetique rapide pour la reaction de degagement de l'oxygene (RDO). Cette reaction suscite un interet particulier en raison de la surtension d'activation relativement elevee a l'anode qui cause la principale perte de rendement du procede. Une etude systematique a ete effectuee sur la substitution du Cu par du Li (0 a 40%), afin d'elucider les proprietes electrocatalytiques des oxydes LixCuy-xCo3-yO4. Ces oxydes, prepares sous forme de poudres par decomposition thermique des nitrates precurseurs entre 300 et 500°C, ont montre (DRX et FTIR) une structure spinelle inverse non-stcechiometrique avec une diminution du volume de la maille cristalline. La surface specifique par BET est d'environ 6 m2 g-1. Le pcn, obtenu par titrage acido-basique, a indique une diminution de la force du lien M-OH avec le taux du Li dans l'oxyde. Les analyses par XPS, realisees sur des films d'oxyde prepares par nebulisation reactive sur un substrat lisse de nickel, revelent un enrichissement de la surface en Cu a partir de 30% Li, et la presence des cations de surface Co2+, Co3+, Cu +, Cu2+ et Cu3+. La concentration de ce dernier montre un maximum a 10 et 20% Li. Suite a la substitution du Cu par du Li, la compensation de la charge serait assuree principalement par la formation d'especes Cu3+ pour les oxydes contenant jusqu'a 20% Li, et par la formation d'especes Co3+ aux taux de substitution superieurs. Les micrographies MEB montrent une morphologie hemispherique des particules d'oxyde reparties uniformement sur le substrat de nickel avec une tendance a l'agglomeration lorsque le taux de Li est accru. Les micrographies AFM revelent une micro-porosite de ces particules d'oxyde. Les films minces deposes sur un substrat de verre ont montre une conductivite tres interessante de l'ordre de 103O-1 cm-1 pour LixCuy-x Co3-yO4 comparee a 2,8 O-1 cm-1 pour Co3O4. La spectroscopie d'impedance a permis de distinguer les processus de la surface interne des films d'oxydes de ceux de l'interface electrode/electrolyte. Les courbes Mott-Schottky (1/C2 en fonction du potentiel) montrent que les films d'oxyde se comportent comme des semi-conducteurs de type p tres dopes (degeneres). Le potentiel de bandes plates et la densite des porteurs de charge majoritaires des oxydes LixCuy-xCo3-yO4 sont de l'ordre de 0,48 a 0,52 V et 1019 a 10 20 cm-3 respectivement. Pour Co 3O4 ces parametres sont de 0,47 V et ≈10 18 cm-3. (Abstract shortened by UMI.)

Method for forming polymerized microfluidic devices

DOEpatents

Sommer, Gregory J [Livermore, CA; Hatch, Anson V [Tracy, CA; Wang, Ying-Chih [Pleasanton, CA; Singh, Anup K [Danville, CA; Renzi, Ronald F [Tracy, CA; Claudnic, Mark R [Livermore, CA

2011-11-01

Methods for making a micofluidic device according to embodiments of the present invention include defining a cavity. Polymer precursor solution is positioned in the cavity, and exposed to light to begin the polymerization process and define a microchannel. In some embodiments, after the polymerization process is partially complete, a solvent rinse is performed, or fresh polymer precursor introduced into the microchannel. This may promote removal of unpolymerized material from the microchannel and enable smaller feature sizes. The polymer precursor solution may contain an iniferter. Polymerized features therefore may be capped with the iniferter, which is photoactive. The iniferter may aid later binding of a polyacrylamide gel to the microchannel surface.

Method for forming polymerized microfluidic devices

DOEpatents

Sommer, Gregory J.; Hatch, Anson V.; Wang, Ying-Chih; Singh, Anup K.; Renzi, Ronald F.; Claudnic, Mark R.

2013-03-12

Methods for making a microfluidic device according to embodiments of the present invention include defining.about.cavity. Polymer precursor solution is positioned in the cavity, and exposed to light to begin the polymerization process and define a microchannel. In some embodiments, after the polymerization process is partially complete, a solvent rinse is performed, or fresh polymer precursor introduced into the microchannel. This may promote removal of unpolymerized material from the microchannel and enable smaller feature sizes. The polymer precursor solution may contain an iniferter. Polymerized features therefore may be capped with the iniferter, which is photoactive. The iniferter may aid later binding of a polyacrylamide gel to the microchannel surface.

Synthesis of silica-polymer core-shell nanoparticles by reversible addition-fragmentation chain transfer polymerization.

PubMed

Moraes, John; Ohno, Kohji; Maschmeyer, Thomas; Perrier, Sébastien

2013-10-14

Hybrid nanoparticles hold great promise for a range of applications such as drug-delivery vectors or colloidal crystal self-assemblies. The challenge of preparing highly monodisperse particles for these applications has recently been overcome by using living radical polymerization techniques. In particular, the use of reversible addition-fragmentation chain transfer (RAFT), initiated from silica surfaces, yields well-defined particles from a range of precursor monomers resulting in nanoparticles of tailored sizes that are accessible via the rational selection of polymerization conditions. Furthermore, using RAFT allows post-polymerization modification to afford multifunctional, monodisperse, nanostructures under mild and non-stringent reaction conditions.

Neonatal Diabetes Caused by Mutations in Sulfonylurea Receptor 1: Interplay between Expression and Mg-Nucleotide Gating Defects of ATP-Sensitive Potassium Channels

PubMed Central

Zhou, Qing; Garin, Intza; Castaño, Luis; Argente, Jesús; Muñoz-Calvo, Ma. Teresa; Perez de Nanclares, Guiomar; Shyng, Show-Ling

2010-01-01

Context: ATP-sensitive potassium (KATP) channels regulate insulin secretion by coupling glucose metabolism to β-cell membrane potential. Gain-of-function mutations in the sulfonylurea receptor 1 (SUR1) or Kir6.2 channel subunit underlie neonatal diabetes. Objective: The objective of the study was to determine the mechanisms by which two SUR1 mutations, E208K and V324M, associated with transient neonatal diabetes affect KATP channel function. Design: E208K or V324M mutant SUR1 was coexpressed with Kir6.2 in COS cells, and expression and gating properties of the resulting channels were assessed biochemically and electrophysiologically. Results: Both E208K and V324M augment channel response to MgADP stimulation without altering sensitivity to ATP4− or sulfonylureas. Surprisingly, whereas E208K causes only a small increase in MgADP response consistent with the mild transient diabetes phenotype, V324M causes a severe activating gating defect. Unlike E208K, V324M also impairs channel expression at the cell surface, which is expected to dampen its functional impact on β-cells. When either mutation was combined with a mutation in the second nucleotide binding domain of SUR1 previously shown to abolish Mg-nucleotide response, the activating effect of E208K and V324M was also abolished. Moreover, combination of E208K and V324M results in channels with Mg-nucleotide sensitivity greater than that seen in individual mutations alone. Conclusion: The results demonstrate that E208K and V324M, located in distinct domains of SUR1, enhance transduction of Mg-nucleotide stimulation from the SUR1 nucleotide binding folds to Kir6.2. Furthermore, they suggest that diabetes severity is determined by interplay between effects of a mutation on channel expression and channel gating. PMID:20810569

A Study of Ziegler–Natta Propylene Polymerization Catalysts by Spectroscopic Methods

PubMed Central

Tkachenko, Olga P.; Kucherov, Alexey V.; Kustov, Leonid M.; Virkkunen, Ville; Leinonen, Timo; Denifl, Peter

2017-01-01

Ziegler–Natta polymerization catalysts were characterized by a complex of surface- and bulk-sensitive methods (DRIFTS, XPS, ESR, and XAS = XANES + EXAFS). A diffuse-reflectance Fourier-transform IR spectroscopy (DRIFTS) study showed the presence of strong Lewis acid sites in different concentrations and absence of strong basic sites in the polymerization catalysts. X-ray photoelectron spectroscopy (XPS), electron-spin resonance (ESR), and (X-ray absorption near-edge structure (XANES) analysis revealed the presence of Ti4+, Ti3+, Ti2+, and Ti1+ species in the surface layers and in the bulk of catalysts. The samples under study differ drastically in terms of the number of ESR-visible paramagnetic sites. The EXAFS study shows the presence of a Cl atom as a nearest neighbor of the absorbing Ti atom. PMID:28772850

In situ chemical oxidative polymerization preparation of poly(3,4-ethylenedioxythiophene)/graphene nanocomposites with enhanced thermoelectric performance.

PubMed

Xu, Kongli; Chen, Guangming; Qiu, Dong

2015-05-01

Three different in situ chemical oxidative polymerization routes, that is, (A) spin-coating and subsequent liquid layer polymerization, (B) spin-coating followed by vapor phase polymerization, and (C) in situ polymerization and then post-treatment by immersion in ethylene glycol (EG), have been developed to achieve poly(3,4-ethylenedioxythiophene)/reduced graphene oxide (PEDOT/rGO) nanocomposites. As demonstrated by scanning electron microscopic and energy-dispersive X-ray spectroscopic techniques, PEDOT has been successfully coated on the surface of the rGO nanosheets by each of the three preparation routes. Importantly, all of the nanocomposites display a greatly enhanced thermoelectric performance (power factors) relative to those of the corresponding neat PEDOT. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An efficient polymeric micromotor doped with Pt nanoparticle@carbon nanotubes for complex bio-media.

PubMed

Li, Yana; Wu, Jie; Xie, Yuzhe; Ju, Huangxian

2015-04-14

A highly efficient polymeric tubular micromotor doped with Pt nanoparticle@carbon nanotubes is fabricated by template-assisted electrochemical growth. The micromotors preserve good navigation in multi-media and surface modification, along with simple synthesis, easy functionalization and good biocompatibility, displaying great promise in biological applications.

Method for fabricating thin films of pyrolytic carbon

DOEpatents

Brassell, G.W.; Lewis, J. Jr.; Weber, G.W.

1980-03-13

The present invention relates to a method for fabricating ultrathin films of pyrolytic carbon. Pyrolytic carbon is vapor deposited onto a concave surface of a heated substrate to a total uniform thickness in the range of about 0.1 to 1.0 micrometer. The carbon film on the substrate is provided with a layer of adherent polymeric resin. The resulting composite film of pyrolytic carbon and polymeric resin is then easily separated from the substrate by shrinking the 10 polymeric resin coating with thermally induced forces.

Method for fabricating thin films of pyrolytic carbon

DOEpatents

Brassell, Gilbert W.; Lewis, Jr., John; Weber, Gary W.

1982-01-01

The present invention relates to a method for fabricating ultra-thin films of pyrolytic carbon. Pyrolytic carbon is vapor deposited onto a concave surface of a heated substrate to a total uniform thickness in the range of about 0.1 to 1.0 micrometer. The carbon film on the substrate is provided with a layer of adherent polymeric resin. The resulting composite film of pyrolytic carbon and polymeric resin is then easily separated from the substrate by shrinking the polymeric resin coating with thermally induced forces.

Modification of Silicone Elastomer Surfaces with Zwitterionic Polymers: Short-Term Fouling Resistance and Triggered Biofouling Release.

PubMed

Shivapooja, Phanindhar; Yu, Qian; Orihuela, Beatriz; Mays, Robin; Rittschof, Daniel; Genzer, Jan; López, Gabriel P

2015-11-25

We present a method for dual-mode-management of biofouling by modifying surface of silicone elastomers with zwitterionic polymeric grafts. Poly(sulfobetaine methacrylate) was grafted from poly(vinylmethylsiloxane) elastomer substrates using thiol-ene click chemistry and surface-initiated, controlled radical polymerization. These surfaces exhibited both fouling resistance and triggered fouling-release functionality. The zwitterionic polymers exhibited fouling resistance over short-term (∼hours) exposure to bacteria and barnacle cyprids. The biofilms that eventually accumulated over prolonged-exposure (∼days) were easily detached by applying mechanical strain to the elastomer substrate. Such dual-functional surfaces may be useful in developing environmentally and biologically friendly coatings for biofouling management on marine, industrial, and biomedical equipment because they can obviate the use of toxic compounds.

Kinetic Modulation of Pulsed Chrono-potentiometric Polymeric Membrane Ion Sensors by Polyelectrolyte Multilayers

PubMed Central

Xu, Yida; Xu, Chao; Shvarev, Alexey; Becker, Thomas; De Marco, Roland

2010-01-01

Polymeric membrane ion selective electrodes are normally interrogated by zero current potentiometry, and their selectivity is understood to be primarily dependent on an extraction/ion-exchange equilibrium between the aqueous sample and polymeric membrane. If concentration gradients in the contacting diffusion layers are insubstantial, the membrane response is thought to be rather independent of kinetic processes such as surface blocking effects. In this work, the surface of calcium-selective polymeric ion-selective electrodes is coated with polyelectrolyte multilayers as evidenced by zeta potential measurements, atomic force microscopy and electrochemical impedance spectroscopy. Indeed, such multilayers have no effect on their potentiometric response if the membranes are formulated in a traditional manner, containing a lipophilic ion-exchanger and a calcium-selective ionophore. However, drastic changes in the potential response are observed if the membranes are operated in a recently introduced kinetic mode using pulsed chronopotentiometry. The results suggest that the assembled nanostructured multilayers drastically alter the kinetics of ion transport to the sensing membrane, making use of the effect that polyelectrolyte multilayers have different permeabilities toward ions with different valences. The results have implications to the design of chemically selective ion sensors since surface localized kinetic limitations can now be used as an additional dimension to tune the operational ion selectivity. PMID:17711298

PEG Molecular Net-Cloth Grafted on Polymeric Substrates and Its Bio-Merits

NASA Astrophysics Data System (ADS)

Zhao, Changwen; Lin, Zhifeng; Yin, Huabing; Ma, Yuhong; Xu, Fujian; Yang, Wantai

2014-05-01

Polymer brushes and hydrogels are sensitive to the environment, which can cause uncontrolled variations on their performance. Herein, for the first time, we report a non-swelling ``PEG molecular net-cloth'' on a solid surface, fabricated using a novel ``visible light induced surface controlled graft cross-linking polymerization'' (VSCGCP) technique. Via this method, we show that 1) the 3D-network structure of the net-cloth can be precisely modulated and its thickness controlled; 2) the PEG net-cloth has excellent resistance to non-specific protein adsorption and cell adhesion; 3) the mild polymerization conditions (i.e. visible light and room temperature) provided an ideal tool for in situ encapsulation of delicate biomolecules such as enzymes; 4) the successive grafting of reactive three-dimensional patterns on the PEG net-cloth enables the creation of protein microarrays with high signal to noise ratio. Importantly, this strategy is applicable to any C-H containing surface, and can be easily tailored for a broad range of applications.

A novel surface modification technique for forming porous polymer monoliths in poly(dimethylsiloxane).

PubMed

Burke, Jeffrey M; Smela, Elisabeth

2012-03-01

A new method of surface modification is described for enabling the in situ formation of homogenous porous polymer monoliths (PPMs) within poly(dimethylsiloxane) (PDMS) microfluidic channels that uses 365 nm UV illumination for polymerization. Porous polymer monolith formation in PDMS can be challenging because PDMS readily absorbs the monomers and solvents, changing the final monolith morphology, and because PDMS absorbs oxygen, which inhibits free-radical polymerization. The new approach is based on sequentially absorbing a non-hydrogen-abstracting photoinitiator and the monomers methyl methacrylate and ethylene diacrylate within the walls of the microchannel, and then polymerizing the surface treatment polymer within the PDMS, entangled with it but not covalently bound. Four different monolith compositions were tested, all of which yielded monoliths that were securely anchored and could withstand pressures exceeding the bonding strength of PDMS (40 psi) without dislodging. One was a recipe that was optimized to give a larger average pore size, required for low back pressure. This monolith was used to concentrate and subsequently mechanical lyse B lymphocytes.

Influence de revetements bioactifs sur les cellules endotheliales: Vers des protheses vasculaires non thrombotiques

NASA Astrophysics Data System (ADS)

Fadlallah, Hicham

Developing vascular prostheses of small diameter to replace vessels closed by atherosclerosis remains a challenge because of the risk of thrombosis. Seeding of endothelial cells, which have antithrombogenic properties, is a promising solution, but we must create surfaces which promote their adhesion and retention to resist shear stresses created by the blood flow on the surface. This master's project aimed at investigating the effect of a plasma polymerized coating rich in primary amines (called LP), with or without elements of the extracellular matrix (Fibronectin (FN) or chondroitin sulphate (CS)) on the endothelial cells and hemocompatibility of polyethylene terephthalate (PET). The adhesion, growth and retention of human umbilical vein endothelial cells (HUVECs) on PET and LP, in the presence and absence of FN or CS, have been studied. In addition, platelet adhesion on different surfaces was evaluated by a perfusion test with whole blood, platelets being previously labeled with rhodamine. Finally a double fluorescent labeling (using Cellview Maroon to mark the HUVECs and CD61 antibody for platelets) was developed to study the retention of endothelial cells, under blood flow and verify their non thrombogenic character. The results obtained show that both the LP coating and the adsorbed FN, strongly increase both the cellular adhesion and growth on PET; however they have no additional effect when the two are combined. They also augment cellular retention to surface, but this remains incomplete. Moreover we observed that the plasma coating (LP) greatly increases the thrombogenicity of the surface, with strong platelet adhesion and activation. This thrombogenicity is extremely reduced when endothelial cells cover the surface, but cell loss under the effect of shear produced by the perfusion creates significant areas of platelet adhesion. The grafting of CS on LP also permits good HUVECs adhesion, growth and retention under shear stress on HUVEC, with no difference from the LP alone. In addition, the CS sharply decreases the platelet adhesion, which is found below the value observed for PET. The double cell labeling also showed that cells adhered on LP+CS has an anti-thrombotic phenotype and can resist blood flow. These studies suggest that a coating of CS is a promising strategy for vascular prosthesis given the combination of the good adhesion of endothelial cells and the low thrombogenicity of the underlying surface. Keywords: vascular prostheses, polymers, bioactive coating, thrombogenicity, HUVECs.

Membrane surface engineering for protein separations: experiments and simulations.

PubMed

Liu, Zizhao; Du, Hongbo; Wickramasinghe, S Ranil; Qian, Xianghong

2014-09-09

A bisphosphonate derived ligand was successfully synthesized and grafted from the surface of regenerated cellulose membrane using atom transfer radical polymerization (ATRP) for protein separations. This ligand has a remarkable affinity for arginine (Arg) residues on protein surface. Hydrophilic residues N-(2-hydroxypropyl) methacrylamide (HPMA) was copolymerized to enhance the flexibility of the copolymer ligand and further improve specific protein adsorption. The polymerization of bisphosphonate derivatives was successful for the first time using ATRP. Static and dynamic binding capacities were determined for binding and elution of Arg rich lysozyme. The interaction mechanism between the copolymer ligand and lysozyme was elucidated using classical molecular dynamics (MD) simulations.

Method of fabricating nested shells and resulting product

DOEpatents

Henderson, Timothy M.; Kool, Lawrence B.

1982-01-01

A multiple shell structure and a method of manufacturing such structure wherein a hollow glass microsphere is surface treated in an organosilane solution so as to render the shell outer surface hydrophobic. The surface treated glass shell is then suspended in the oil phase of an oil-aqueous phase dispersion. The oil phase includes an organic film-forming monomer, a polymerization initiator and a blowing agent. A polymeric film forms at each phase boundary of the dispersion and is then expanded in a blowing operation so as to form an outer homogeneously integral monocellular substantially spherical thermoplastic shell encapsulating an inner glass shell of lesser diameter.

Validation de modeles d'eclairement incident a la surface de l'eau en Arctique

NASA Astrophysics Data System (ADS)

Julien, Laliberte

Dans ce memoire, deux methodes d'estimation d'eclairement incident a la surface de l'Arctique sont evaluees. Une base de donnees in situ a ete constituee a partir de 16 campagnes oceanographiques en Arctique. Pour les dates ou l'eclairement est mesure, les estimations d'eclairement journalier incident a la surface obtenues a partir des satellites de la couleur de l'eau (Frouin et al. 2003) et a partir des satellites meteorologiques (Belanger et al. 2013) sont produites. De meme, un exercise de comparaison entre les estimations satellitaires est produit pour l'annee 2004 sur tout le territoire Arctique. La comparaison entre les donnees observees et les donnees estimees a partir des satellites meteorologiques donnent un biais de 6% et une quadratique moyenne 33%. La comparaison entre les observations et les satellites de la couleur de l'eau donnent un biais de 2% et 20%. Finalement, la difference moyenne entre les estimations des 2 methodes d'estimation satellitaires pour tout l'Arctique pour l'annee 2004 est de 0,29 Einstein/m2/jour avec un ecart-type de 6,78 Einstein/m2/jour. Les resultats montrent entre autres que la methode qui utilise les satellites de la couleur de l'eau est plus precise pour estimer l'eclairement sur une petite superficie puisqu'elle rend mieux les variations locales dans l'eclairement. La methode qui utilise les satellites meteorologique est plus precise pour estimer l'eclairement sur une grande superficie, puisqu'elle est moins restreinte dans les conditions qui permettent de fournir une estimation. Ainsi, la methode qui utilise les satellites meteorologiques montre qu'un eclairement annuel de l'Arctique de 38% n'est pas prise en compte par les satellites de la couleur de l'eau.

Prédiction du comportement à long terme des matériaux polymères

NASA Astrophysics Data System (ADS)

Lemaire, J.

1998-06-01

Most of the world activity on research, development and control of polymer durability is still based on empirical techniques developed in the early ages of polymer uses. Those techniques should be critically analysed considering the state of the art in the fundamental understanding of these complex phenomena. A more rational approach is described, especially to predict the lifetime of polymeric materials in environmental conditions. That approach is based on the recognition of the chemical evolution mechanisms. Les activités de recherche, développement et contrôle de durabilité des matériaux polymères sont encore, pour une part très importante, basées sur l'emploi de techniques empiriques dont les principes ont été énoncés dès le début de l'exploitation de ces matériaux. Une analyse critique de ces méthodes s'impose aujourd'hui en tenant compte de l'avancement des connaissances. Une approche plus rationnelle est décrite, approche basée sur la reconnaissance des mécanismes d'évolution chimique. A titre d'exemple, le mécanisme d'évolution du PVC sous contraintes conjuguées de l'UV, de la chaleur et de l'oxygène, est décrit. Des études récentes de photooxydation de polymères conducteurs au sein de polyéthylène sont également succinctement rapportées.

Flow Control

DTIC Science & Technology

2013-04-08

estimator will relate an array of surface mounted sensor signals, de- fined as p( xs , t), to the flow state which is modeled by the time coefficients of a POD...layer growth, separation points, etc.) are chosen and defined as ( xs ) within the numeric simulation. A surface POD analysis, p( xs , t)≃ k ∑ p=1 asp(t)ϕsp... xs ), (30) yields surface POD modes φ sp( xs ). The resulting locations of the maxima and minima of the sur- face modes show where the largest

Origin of the Energy Barrier to Chemical Reactions of O2 on Al(111): Evidence for Charge Transfer, Not Spin Selection

DTIC Science & Technology

2012-11-08

change of O2 spin, at the barrier [Fig. 3]; i.e., the corresponding diabatic surfaces cross. Far from the Al surface, the triplet state is...previous theoretical models, in particular nonadiabatic [17] or diabatic [16] approaches, which also find an energy barrier consistent with experiment...crossings of different diabatic O2 spin configuration sur- faces are accommodated by small spin fluctuations within the metal surface. For parallel

Plasma-grafting polymerization on carbon fibers and its effect on their composite properties

NASA Astrophysics Data System (ADS)

Zhang, Huanxia; Li, Wei

2015-11-01

Interfacial adhesion between matrix and fibers plays a crucial role in controlling the performance of composites. Carbon fibers have the major constraint of chemical interness and hence have limited adhesion with the matrix. Surface treatment of fibers is the best solution to this problem. In this work, carbon fibers were activated by plasma and grafting polymerization. The grafting ratio of polymerization was obtained by acid-base titration. The chemical and physical changes induced by the treatments on carbon fiber surface was examined using contact angle measurements, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) technique. The interfacial adhesion of CF/EP (carbon fiber/epoxy) composites were analyzed by a single fiber composite (SFC) for filament fragmentation test. Experimental results show that the grafting rate was not only the function of the plasma-treat time but also the concentration of the grafting polymerization. The oxygen-containing groups (such as Csbnd O, Cdbnd O, and Osbnd Cdbnd O) and the interfacial shear strength (IFSS) of the plasma-grafting carbon fiber increased more significantly than the carbon fiber without plasma treatment grafted with MAH. This demonstrates that the surfaces of the carbon fiber samples are more active, hydrophilic, and rough after plasma-grafting treatments using a DBD operating in ambient argon mixture with oxygen. With DBD (dielectric barrier discharges) operating in ambient argon mixture with oxygen, the more active, hydrophilic, and rough surface was obtained by the plasma-grafting treatments.

Clinical use and material wear of polymeric tracheostomy tubes.

PubMed

Björling, Gunilla; Axelsson, Sara; Johansson, Unn-Britt; Lysdahl, Michael; Markström, Agneta; Schedin, Ulla; Aune, Ragnhild E; Frostell, Claes; Karlsson, Sigbritt

2007-09-01

The objectives were to compare the duration of use of polymeric tracheostomy tubes, i.e., silicone (Si), polyvinyl chloride (PVC), and polyurethane (PU), and to determine whether surface changes in the materials could be observed after 30 days of patient use. Data were collected from patient and technical records for all tracheostomized patients attending the National Respiratory Center in Sweden. In the surface study, 19 patients with long-term tracheostomy were included: six with Bivona TTS Si tubes, eight with Shiley PVC tubes, and five with Trachoe Twist PU tubes. All tubes were exposed in the trachea for 30 days before being analyzed by scanning electron microscopy (SEM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). New tubes and tubes exposed in phosphate-buffered saline were used as reference. Si tubes are used for longer periods of time than those made of PVC (P<.0001) and PU (P=.021). In general, all polymeric tubes were used longer than the recommended 30-day period. Eighteen of the 19 tubes exposed in patients demonstrated, in one or more areas of the tube, evident surface changes. The morphologic changes identified by SEM correlate well with the results obtained by ATR-FTIR. Si tracheostomy tubes are in general used longer than those made of PVC and PU. Most of the tubes exposed in the trachea for 30 days suffered evident surface changes, with degradation of the polymeric chains as a result.

Fabrication of a platform to isolate the influences of surface nanotopography from chemistry on bacterial attachment and growth.

PubMed

Pegalajar-Jurado, Adoracion; Easton, Christopher D; Crawford, Russell J; McArthur, Sally L

2015-03-26

Billions of dollars are spent annually worldwide to combat the adverse effects of bacterial attachment and biofilm formation in industries as varied as maritime, food, and health. While advances in the fabrication of antifouling surfaces have been reported recently, a number of the essential aspects responsible for the formation of biofilms remain unresolved, including the important initial stages of bacterial attachment to a substrate surface. The reduction of bacterial attachment to surfaces is a key concept in the prevention or minimization of biofilm formation. The chemical and physical characteristics of both the substrate and bacteria are important in understanding the attachment process, but substrate modification is likely the most practical route to enable the extent of bacterial attachment taking place to be effectively controlled. The microtopography and chemistry of the surface are known to influence bacterial attachment. The role of surface chemistry versus nanotopography and their interplay, however, remain unclear. Most methods used for imparting nanotopographical patterns onto a surface also induce changes in the surface chemistry and vice versa. In this study, the authors combine colloidal lithography and plasma polymerization to fabricate homogeneous, reproducible, and periodic nanotopographies with a controllable surface chemistry. The attachment of Escherichia coli bacteria onto carboxyl (plasma polymerized acrylic acid, ppAAc) and hydrocarbon (plasma polymerized octadiene, ppOct) rich plasma polymer films on either flat or colloidal array surfaces revealed that the surface chemistry plays a critical role in bacterial attachment, whereas the effect of surface nanotopography on the bacterial attachment appears to be more difficult to define. This platform represents a promising approach to allow a greater understanding of the role that surface chemistry and nanotopography play on bacterial attachment and the subsequent biofouling of the surface.

Surface modification of boron nitride nanosheets by polyelectrolytes via atom transfer radical polymerization

NASA Astrophysics Data System (ADS)

Wu, Yuanpeng; Guo, Meiling; Liu, Guanfei; Xue, Shishan; Xia, Yuanmeng; Liu, Dan; Lei, Weiwei

2018-04-01

In this study, the surface modification of boron nitride nanosheets (BNNSs) with poly 2-acrylamido-2-methyl- propanesulfonate (PAMPS) brushes is achieved through electron transfer atom transfer radical polymerization (ARGET ATRP). BNNSs surface was first modified with α-bromoisobutyryl bromide (BIBB) via hydroxyl groups, then PAMPS brushes were grown on the surface through ARGET ATRP. Polyelectrolyte brushes modified BNNSs were further characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyses (TGA), x-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The concentraction of water-dispersion of BNNSs have been enhanced significantly by PAMPS and the high water-dispersible functional BNNSs/PAMPS composites are expected to have potential applications in biomedical and thermal management in electronics.

Polymeric micelles for ocular drug delivery: From structural frameworks to recent preclinical studies.

PubMed

Mandal, Abhirup; Bisht, Rohit; Rupenthal, Ilva D; Mitra, Ashim K

2017-02-28

Effective intraocular drug delivery poses a major challenge due to the presence of various elimination mechanisms and physiological barriers that result in low ocular bioavailability after topical application. Over the past decades, polymeric micelles have emerged as one of the most promising drug delivery platforms for the management of ocular diseases affecting the anterior (dry eye syndrome) and posterior (age-related macular degeneration, diabetic retinopathy and glaucoma) segments of the eye. Promising preclinical efficacy results from both in-vitro and in-vivo animal studies have led to their steady progression through clinical trials. The mucoadhesive nature of these polymeric micelles results in enhanced contact with the ocular surface while their small size allows better tissue penetration. Most importantly, being highly water soluble, these polymeric micelles generate clear aqueous solutions which allows easy application in the form of eye drops without any vision interference. Enhanced stability, larger cargo capacity, non-toxicity, ease of surface modification and controlled drug release are additional advantages with polymeric micelles. Finally, simple and cost effective fabrication techniques render their industrial acceptance relatively high. This review summarizes structural frameworks, methods of preparation, physicochemical properties, patented inventions and recent advances of these micelles as effective carriers for ocular drug delivery highlighting their performance in preclinical studies. Copyright © 2017 Elsevier B.V. All rights reserved.

Bioremediation of phenolic compounds from water with plant root surface peroxidases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adler, P.R.; Arora, R.; El Ghaouth, A.

1994-09-01

Peroxidases have been shown to polymerize phenolic compounds, thereby removing them from solution by precipitation. Others have studied the role of root surface associated peroxidases as a defense against fungal root pathogens; however, their use in detoxification of organic pollutants in vivo at the root surface has not been studied. Two plant species, waterhyacinth [Eichhornia crassipes (C. Mart) Solms-Laub.] and tomato (Lycopersicon esculentum L.), were tested for both in vitro and in vivo peroxidase activity on the root surface. In vitro studies indicated that root surface peroxidase activities were 181 and 78 nmol tetraguaiacol formed min{sup -1} g{sup -1} rootmore » fresh wt., for tomato and waterhyacinth, respectively. Light microscope studies revealed that guaiacol was polymerized in vivo at the root surface. Although peroxidase was evenly distributed on tomato roots, it was distributed patchily on waterhyacinth roots. In vitro studies using gas chromatography-mass spectrometry (GC-MS) showed that the efficiency of peroxidase to polymerize phenols vary with phenolic compound. We suggest that plants may be utilized as a source of peroxidases for removal of phenolic compounds that are on the EPA priority pollutant list and that root surface peroxidases may minimize the absorption of phenolic compounds into plants by precipitating them at the root surface. In this study we have identified a new use for root-associated proteins in ecologically engineering plant systems for bioremediation of phenolic compounds in the soil and water environment. 25 refs., 2 figs., 2 tabs.« less

Regulating the surface poly(ethylene glycol) density of polymeric nanoparticles and evaluating its role in drug delivery in vivo.

PubMed

Du, Xiao-Jiao; Wang, Ji-Long; Liu, Wei-Wei; Yang, Jin-Xian; Sun, Chun-Yang; Sun, Rong; Li, Hong-Jun; Shen, Song; Luo, Ying-Li; Ye, Xiao-Dong; Zhu, Yan-Hua; Yang, Xian-Zhu; Wang, Jun

2015-11-01

Poly(ethylene glycol) (PEG) is usually used to protect nanoparticles from rapid clearance in blood. The effects are highly dependent on the surface PEG density of nanoparticles. However, there lacks a detailed and informative study in PEG density and in vivo drug delivery due to the critical techniques to precisely control the surface PEG density when maintaining other nano-properties. Here, we regulated the polymeric nanoparticles' size and surface PEG density by incorporating poly(ε-caprolactone) (PCL) homopolymer into poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-PCL) and adjusting the mass ratio of PCL to PEG-PCL during the nanoparticles preparation. We further developed a library of polymeric nanoparticles with different but controllable sizes and surface PEG densities by changing the molecular weight of the PCL block in PEG-PCL and tuning the molar ratio of repeating units of PCL (CL) to that of PEG (EG). We thus obtained a group of nanoparticles with variable surface PEG densities but with other nano-properties identical, and investigated the effects of surface PEG densities on the biological behaviors of nanoparticles in mice. We found that, high surface PEG density made the nanoparticles resistant to absorption of serum protein and uptake by macrophages, leading to a greater accumulation of nanoparticles in tumor tissue, which recuperated the defects of decreased internalization by tumor cells, resulting in superior antitumor efficacy when carrying docetaxel. Copyright © 2015 Elsevier Ltd. All rights reserved.

Microhardness of resin composites polymerized by plasma arc or conventional visible light curing.

PubMed

Park, S Ho; Krejci, I; Lutz, F

2002-01-01

This study evaluated the effectiveness of the plasma arc curing (PAC) unit for composite curing. To compare its effectiveness with conventional quartz tungsten halogen (QTH) light curing units, the microhardness of two composites (Z100 and Tetric Ceram) that had been light cured by the PAC or QTH units, were compared according to the depth from the composite surface. In addition, linear polymerization shrinkage was compared using a custom-made linometer between composites which were light cured by PAC or QTH units. Measuring polymerization shrinkage for two resin composites (Z100 and Tetric Ceram) was performed after polymerization with either QTH or PAC units. In the case of curing with the PAC unit, the composite was light cured with Apollo 95E for two (Group 1), three (Group 2), six (Group 3) or 2 x 6 (Group 4) seconds. For light curing with the QTH unit, the composite was light cured for 60 seconds with Optilux 500 (Group 5). The linear polymerization shrinkage of composites was determined in the linometer. Two resin composites were used to measure microhardness. Two-mm thick samples were light cured for three seconds (Group 1), six seconds (Group 2) or 12 (2 x 6) seconds (Group 3) with Apollo 95E or they were conventionally light cured with Optilux 500 for 30 seconds (Group 4) or 60 seconds (Group 5). For 3 mm thick samples, the composites were light cured for six seconds (Group 1), 12 (2 x 6) seconds (Group 2) or 18 (3 x 6) seconds (Group 3) with Apollo 95E or they were conventionally light cured with Optilux 500 for 30 seconds (Group 4) or 60 seconds (Group 5). Twenty samples were assigned to each group. The microhardness of the upper and lower surfaces was measured with a Vickers hardness-measuring instrument under load. The difference in microhardness between the upper and lower surfaces in each group was analyzed by paired t-test. For the upper or lower surfaces, one-way ANOVA with Tukey was used. For Tetric Ceram, the amount of polymerization shrinkage was lower when cured with the Apollo 95E for two or three seconds than when cured for six and 12 (2 x 6) seconds, or for 60 seconds with Optilux 500 (p<0.05). For Z100, the amount of linear polymerization shrinkage was lower when cured with the Apollo 95E for two, three and six seconds than for 12 (2 x 6) seconds with Apollo 95E or for 60 seconds with the Optilux 500 (p<0.05). The results of the microhardness test indicated that there was no statistically significant difference in microhardness between groups for the upper surface. However, for the lower surface, when the composites were light cured with Apollo 95E for three seconds as recommended by the manufacturer, microhardness of the lower surface was usually lower than that of the upper surface and did not cure sufficiently. Conclusively, when compared with conventional QTH unit, the PAC unit, Apollo 95E did not properly cure the lower composite surface when the layer thickness exceeded 2 mm. In addition, three seconds of curing time, which the manufacturer recommended, was insufficient for optimal curing of composites.

Formation and properties of surface-anchored polymer assemblies with tunable physico-chemical characteristics

NASA Astrophysics Data System (ADS)

Wu, Tao

We describe two new methodologies leading to the formation of novel surface-anchored polymer assemblies on solid substrates. While the main goal is to understand the fundamentals pertaining to the preparation and properties of the surface-bound polymer assemblies (including neutral and chargeable polymers), several examples also are mentioned throughout the Thesis that point out to practical applications of such structures. The first method is based on generating assemblies comprising anchored polymers with a gradual variation of grafting densities on solid substrates. These structures are prepared by first covering the substrate with a molecular gradient of the polymerization initiator, followed by polymerization from these substrate-bound initiator centers ("grafting from"). We apply this technique to prepare grafting density gradients of poly(acryl amide) (PAAm) and poly(acrylic acid) (PAA) on silica-covered substrates. We show that using the grafting density gradient geometry, the characteristics of surface-anchored polymers in both the low grafting density ("mushroom") regime as well as the high grafting density ("brush") regime can be accessed conveniently on a single sample. We use a battery of experimental methods, including Fourier transform infrared spectroscopy (FTIR), Near-edge absorption fine structure spectroscopy (NEXAFS), contact angle, ellipsometry, to study the characteristics of the surface-bound polymer layers. We also probe the scaling laws of neutral polymer as a function of grafting density, and for weak polyelectrolyte, in addition to the grafting density, we study the affect of solution ionic strength and pH values. In the second novel method, which we coined as "mechanically assisted polymer assembly" (MAPA), we form surface anchored polymers by "grafting from" polymerization initiators deposited on elastic surfaces that have been previously extended uniaxially by a certain length increment, Deltax. Upon releasing the strain in the substrate after completion of polymerization, we show the grafting density of the polymers grafted to flexible substrates can be tuned as a function of Deltax.

Control of Fibrinogen Assembly by Changing a Polarity of Surfaces

NASA Astrophysics Data System (ADS)

Koo, Jaseung; Liu, Ying; Snow, Sara; Rambhia, Pooja; Koga, Tadanori; Rafailovich, Miriam; Galanakis, Dennis

2009-03-01

Thrombogenesis causes various problems associated with an interruption in the blood flow (e.g., myocardial and cerebral infarction), and a hindrance to use of blood-contact vascular biomaterials (e.g., hemodialysis and cardiopulmonary bypass) with long-term patency since undesired adsorption of blood components occurs on vessels or biomaterials, such as surface-induced thrombosis. we showed that this clotting procedure can be occurred on hydrophobic polymeric surfaces without thrombin cleavage. However, the fibrinogen fibers were not formed on the polar surface such as spun-cast polymer film with pyridine and phenol groups. We also found that αC domains play an important role in initiation of polymerization on surface. Therefore, molecular association was inhibited on the polar surfaces due to confinement of αC chains on the surfaces. These findings were directly applied to stent surface modification. The commercial stent consist of Co-Cr alloy forms undesired fiber formation. However, PS-r-PVPh (13% phenol) coated stent surfaces completely prevent fiber formation.

Bio-Functional, Lanthanide-Labeled Polymer Particles by Seeded Emulsion Polymerization and their Characterization by Novel ICP-MS Detection.

PubMed

Thickett, Stuart C; Abdelrahman, Ahmed I; Ornatsky, Olga; Bandura, Dmitry; Baranov, Vladimir; Winnik, Mitchell A

2010-01-01

We present the synthesis and characterization of monodisperse, sub-micron poly(styrene) (PS) particles loaded with up to and including 10(7) lanthanide (Ln) ions per particle. These particles have been synthesized by seeded emulsion polymerization with a mixture of monomer and a pre-formed Ln complex, and analyzed on a particle-by-particle basis by a unique inductively coupled plasma mass cytometer. Seed particles were prepared by surfactant-free emulsion polymerization (SFEP) to obtain large particle sizes in aqueous media. Extensive surface acid functionality was introduced using the acid-functional initiator ACVA, either during seed latex synthesis or in the second stage of polymerization. The loading of particles with three different Ln ions (Eu, Tb, and Ho) has proven to be close to 100 % efficient on an individual and combined basis. Covalent attachment of metal-tagged peptides and proteins such as Neutravidin to the particle surface was shown to be successful and the number of bound species can be readily determined. We believe these particles can serve as precursors for multiplexed, bead-based bio-assays utilizing mass cytometric detection.

Bio-Functional, Lanthanide-Labeled Polymer Particles by Seeded Emulsion Polymerization and their Characterization by Novel ICP-MS Detection

PubMed Central

Thickett, Stuart C.; Abdelrahman, Ahmed I.; Ornatsky, Olga; Bandura, Dmitry; Baranov, Vladimir; Winnik, Mitchell A.

2010-01-01

We present the synthesis and characterization of monodisperse, sub-micron poly(styrene) (PS) particles loaded with up to and including 107 lanthanide (Ln) ions per particle. These particles have been synthesized by seeded emulsion polymerization with a mixture of monomer and a pre-formed Ln complex, and analyzed on a particle-by-particle basis by a unique inductively coupled plasma mass cytometer. Seed particles were prepared by surfactant-free emulsion polymerization (SFEP) to obtain large particle sizes in aqueous media. Extensive surface acid functionality was introduced using the acid-functional initiator ACVA, either during seed latex synthesis or in the second stage of polymerization. The loading of particles with three different Ln ions (Eu, Tb, and Ho) has proven to be close to 100 % efficient on an individual and combined basis. Covalent attachment of metal-tagged peptides and proteins such as Neutravidin to the particle surface was shown to be successful and the number of bound species can be readily determined. We believe these particles can serve as precursors for multiplexed, bead-based bio-assays utilizing mass cytometric detection. PMID:20396648

Adsorption of trichloroethylene and benzene vapors onto hypercrosslinked polymeric resin.

PubMed

Liu, Peng; Long, Chao; Li, Qifen; Qian, Hongming; Li, Aimin; Zhang, Quanxing

2009-07-15

In this research, the adsorption equilibria of trichloroethylene (TCE) and benzene vapors onto hypercrosslinked polymeric resin (NDA201) were investigated by the column adsorption method in the temperature range from 303 to 333 K and pressures up to 8 kPa for TCE, 12 kPa for benzene. The Toth and Dubinin-Astakov (D-A) equations were tested to correlate experimental isotherms, and the experimental data were found to fit well by them. The good fits and characteristic curves of D-A equation provided evidence that a pore-filling phenomenon was involved during the adsorption of TCE and benzene onto NDA-201. Moreover, thermodynamic properties such as the Henry's constant and the isosteric enthalpy of adsorption were calculated. The isosteric enthalpy curves varied with the surface loading for each adsorbate, indicating that the hypercrosslinked polymeric resin has an energetically heterogeneous surface. In addition, a simple mathematic model developed by Yoon and Nelson was applied to investigate the breakthrough behavior on a hypercrosslinked polymeric resin column at 303 K and the calculated breakthrough curves were in high agreement with corresponding experimental data.

[The influence of polymerization time on physicochemical properties of the acrylic resin Vertex RS].

PubMed

Fraczak, Bogumiła; Sobolewska, Ewa; Ey-Chmielewska, Halina; Skowronek, Maria; Błazewicz, Stanisław

2009-01-01

A good denture can only be produced through proper actions during the clinical and laboratory stages of the production process. The aim of this study was to determine if a change in polymerization time affects the physicochemical properties of polymethacrylate material used for dentures. We examined the acrylic resin Vertex R.S. polymerized for 15, 25, 40, or 60 minutes. Palapress Vario was taken as reference material. Static bending, microhardness, surface wettability, and susceptibility to abrasion were determined. The microhardness test showed that most of the samples had similar Vickers hardness (VS) values, except for the sample polymerized for 25 min. which demonstrated a significantly higher value. Grindability was affected by a change in polymerization time. Mass loss was greatest for samples polymerized for 15, 25, and 60 min. and smallest for Vertex 40 and Palapress Vario. We also observed differences in the wetting angle. Vertex 40 and 60 had a relatively low wetting angle signifying that longer polymerization time results in lower hydrophobicity of the material. The present study has demonstrated that polymerization time has a significant effect on the hardness and some mechanical properties of the acrylic resin.

Bloch surface waves confined in one dimension with a single polymeric nanofibre

NASA Astrophysics Data System (ADS)

Wang, Ruxue; Xia, Hongyan; Zhang, Douguo; Chen, Junxue; Zhu, Liangfu; Wang, Yong; Yang, Erchan; Zang, Tianyang; Wen, Xiaolei; Zou, Gang; Wang, Pei; Ming, Hai; Badugu, Ramachandram; Lakowicz, Joseph R.

2017-02-01

Polymeric fibres with small radii (such as ≤125 nm) are delicate to handle and should be laid down on a solid substrate to obtain practical devices. However, placing these nanofibres on commonly used glass substrates prevents them from guiding light. In this study, we numerically and experimentally demonstrate that when the nanofibre is placed on a suitable dielectric multilayer, it supports a guided mode, a Bloch surface wave (BSW) confined in one dimension. The physical origin of this new mode is discussed in comparison with the typical two-dimensional BSW mode. Polymeric nanofibres are easily fabricated to contain fluorophores, which make the dielectric nanofibre and multilayer configuration suitable for developing a large range of new nanometric scale devices, such as processor-memory interconnections, devices with sensitivity to target analytes, incident polarization and multi-colour BSW modes.

Engineering the mobility increment in pentacene-based field-effect transistors by fast cooling of polymeric modification layer

NASA Astrophysics Data System (ADS)

Ling, Haifeng; Zhang, Chenxi; Chen, Yan; Shao, Yaqing; Li, Wen; Li, Huanqun; Chen, Xudong; Yi, Mingdong; Xie, Linghai; Huang, Wei

2017-06-01

In this work, we investigate the effect of the cooling rate of polymeric modification layers (PMLs) on the mobility improvement of pentacene-based organic field-effect transistors (OFETs). In contrast to slow cooling (SC), the OFETs fabricated through fast cooling (FC) with PMLs containing side chain-phenyl rings, such as polystyrene (PS) and poly (4-vinylphenol) (PVP), show an obvious mobility incensement compared with that of π-group free polymethylmethacrylate (PMMA). Atomic force microscopy (AFM) images and x-ray diffraction (XRD) characterizations have showed that fast-cooled PMLs could effectively enhance the crystallinity of pentacene, which might be related to the optimized homogeneity of surface energy on the surface of polymeric dielectrics. Our work has demonstrated that FC treatment could be a potential strategy for performance modulation of OFETs.

Seed-Surface Grafting Precipitation Polymerization for Preparing Microsized Optically Active Helical Polymer Core/Shell Particles and Their Application in Enantioselective Crystallization.

PubMed

Zhao, Biao; Lin, Jiangfeng; Deng, Jianping; Liu, Dong

2018-05-14

Core/shell particles constructed by polymer shell and silica core have constituted a significant category of advanced functional materials. However, constructing microsized optically active helical polymer core/shell particles still remains as a big academic challenge due to the lack of effective and universal preparation methods. In this study, a seed-surface grafting precipitation polymerization (SSGPP) strategy is developed for preparing microsized core/shell particles with SiO 2 as core on which helically substituted polyacetylene is covalently bonded as shell. The resulting core/shell particles exhibit fascinating optical activity and efficiently induce enantioselective crystallization of racemic threonine. Taking advantage of the preparation strategy, novel achiral polymeric and hybrid core/shell particles are also expected. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biochemical separations by continuous-bed chromatography.

PubMed

Tisch, T L; Frost, R; Liao, J L; Lam, W K; Remy, A; Scheinpflug, E; Siebert, C; Song, H; Stapleton, A

1998-08-07

Innovations in column-packing media for biomolecule purification have progressed from large spherical, porous polysaccharide beads to advanced polymeric supports. Continuous-bed technology is a radical new technology for chromatography based on the polymerization of advanced monomers and ionomers directly in the chromatographic column. The polymer chains form aggregates which coalesce into a dense, homogeneous network of interconnected nodules consisting of microparticles with an average diameter of 3000 A. The voids or channels between the nodules are large enough to permit a high hydrodynamic flow. Due to the high cross-linking of the polymer matrix, the surface of each nodule is nonporous yet the polymeric microparticles provide a very large surface area for high binding capacity. This paper will demonstrate the properties and advantages of using a continuous bed support for high resolution biomolecule separations at high flow-rates without sacrificing capacity.

High throughput atmospheric pressure plasma-induced graft polymerization for identifying protein-resistant surfaces.

PubMed

Gu, Minghao; Kilduff, James E; Belfort, Georges

2012-02-01

Three critical aspects of searching for and understanding how to find highly resistant surfaces to protein adhesion are addressed here with specific application to synthetic membrane filtration. They include the (i) discovery of a series of previously unreported monomers from a large library of monomers with high protein resistance and subsequent low fouling characteristics for membrane ultrafiltration of protein-containing fluids, (ii) development of a new approach to investigate protein-resistant mechanisms from structure-property relationships, and (iii) adaptation of a new surface modification method, called atmospheric pressure plasma-induced graft polymerization (APP), together with a high throughput platform (HTP), for low cost vacuum-free synthesis of anti-fouling membranes. Several new high-performing chemistries comprising two polyethylene glycol (PEG), two amines and one zwitterionic monomers were identified from a library (44 commercial monomers) of five different classes of monomers as strong protein-resistant monomers. Combining our analysis here, using the Hansen solubility parameters (HSP) approach, and data from the literature, we conclude that strong interactions with water (hydrogen bonding) and surface flexibility are necessary for producing the highest protein resistance. Superior protein-resistant surfaces and subsequent anti-fouling performance was obtained with the HTP-APP as compared with our earlier HTP-photo graft-induced polymerization (PGP). Copyright © 2011 Elsevier Ltd. All rights reserved.

Controlled Fab installation onto polymeric micelle nanoparticles for tuned bioactivity

NASA Astrophysics Data System (ADS)

Chen, Shaoyi; Florinas, Stelios; Teitgen, Abigail; Xu, Ze-Qi; Gao, Changshou; Wu, Herren; Kataoka, Kazunori; Cabral, Horacio; Christie, R. James

2017-12-01

Antibodies and antigen-binding fragments (Fabs) can be used to modify the surface of nanoparticles for enhanced target binding. In our previous work, site-specific conjugation of Fabs to polymeric micelles using conventional methods was limited to approximately 30% efficiency, possibly due to steric hindrance related to macromolecular reactants. Here, we report a new method that enables conjugation of Fabs onto a micelle surface in a controlled manner with up to quantitative conversion of nanoparticle reactive groups. Variation of (i) PEG spacer length in a heterofunctionalized cross-linker and (ii) Fab/polymer feed ratios resulted in production of nanoparticles with a range of Fab densities on the surface up to the theoretical maximum value. The biological impact of variable Fab density was evaluated in vitro with respect to cell uptake and cytotoxicity of a drug-loaded (SN38) targeted polymeric micelle bearing anti-EphA2 Fabs. Fab conjugation increased cell uptake and potency compared with non-targeted micelles, although a Fab density of 60% resulted in decreased uptake and potency of the targeted micelles. Altogether, our findings demonstrate that conjugation strategies can be optimized to allow control of Fab density on the surface of nanoparticles and also that Fab density may need to be optimized for a given cell-surface target to achieve the highest bioactivity.

Occlusion of Sulfate-Based Diblock Copolymer Nanoparticles within Calcite: Effect of Varying the Surface Density of Anionic Stabilizer Chains.

PubMed

Ning, Yin; Fielding, Lee A; Ratcliffe, Liam P D; Wang, Yun-Wei; Meldrum, Fiona C; Armes, Steven P

2016-09-14

Polymerization-induced self-assembly (PISA) offers a highly versatile and efficient route to a wide range of organic nanoparticles. In this article, we demonstrate for the first time that poly(ammonium 2-sulfatoethyl methacrylate)-poly(benzyl methacrylate) [PSEM-PBzMA] diblock copolymer nanoparticles can be prepared with either a high or low PSEM stabilizer surface density using either RAFT dispersion polymerization in a 2:1 v/v ethanol/water mixture or RAFT aqueous emulsion polymerization, respectively. We then use these model nanoparticles to gain new insight into a key topic in materials chemistry: the occlusion of organic additives into inorganic crystals. Substantial differences are observed for the extent of occlusion of these two types of anionic nanoparticles into calcite (CaCO3), which serves as a suitable model host crystal. A low PSEM stabilizer surface density leads to uniform nanoparticle occlusion within calcite at up to 7.5% w/w (16% v/v), while minimal occlusion occurs when using nanoparticles with a high PSEM stabilizer surface density. This counter-intuitive observation suggests that an optimum anionic surface density is required for efficient occlusion, which provides a hitherto unexpected design rule for the incorporation of nanoparticles within crystals.

Formation of conductive polymers using nitrosyl ion as an oxidizing agent

DOEpatents

Choi, Kyoung-Shin; Jung, Yongju; Singh, Nikhilendra

2016-06-07

A method of forming a conductive polymer deposit on a substrate is disclosed. The method may include the steps of preparing a composition comprising monomers of the conductive polymer and a nitrosyl precursor, contacting the substrate with the composition so as to allow formation of nitrosyl ion on the exterior surface of the substrate, and allowing the monomer to polymerize into the conductive polymer, wherein the polymerization is initiated by the nitrosyl ion and the conductive polymer is deposited on the exterior surface of the substrate. The conductive polymer may be polypyrrole.

Biofouling on polymeric heat exchanger surfaces with E. coli and native biofilms.

PubMed

Pohl, S; Madzgalla, M; Manz, W; Bart, H J

2015-01-01

The biofouling affinity of different polymeric surfaces (polypropylene, polysulfone, polyethylene terephthalate, and polyether ether ketone) in comparison to stainless steel (SS) was studied for the model bacterium Escherichia coli K12 DSM 498 and native biofilms originating from Rhine water. The biofilm mass deposited on the polymer surfaces was minimized by several magnitudes compared to SS. The cell count and the accumulated biomass of E. coli on the polymer surfaces showed an opposing linear trend. The promising low biofilm formation on the polymers is attributed to the combination of inherent surface properties (roughness, surface energy and hydrophobicity) when compared to SS. The fouling characteristics of E. coli biofilms show good conformity with the more complex native biofilms investigated. The results can be utilized for the development of new polymer heat exchangers when using untreated river water as coolant or for other processes needing antifouling materials.

Surface PEGylation of mesoporous silica materials via surface-initiated chain transfer free radical polymerization: Characterization and controlled drug release.

PubMed

Huang, Long; Liu, Meiying; Mao, Liucheng; Huang, Qiang; Huang, Hongye; Wan, Qing; Tian, Jianwen; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

2017-12-01

As a new type of mesoporous silica materials with large pore diameter (pore size between 2 and 50nm) and high specific surface areas, SBA-15 has been widely explored for different applications especially in the biomedical fields. The surface modification of SBA-15 with functional polymers has demonstrated to be an effective way for improving its properties and performance. In this work, we reported the preparation of PEGylated SBA-15 polymer composites through surface-initiated chain transfer free radical polymerization for the first time. The thiol group was first introduced on SBA-15 via co-condensation with γ-mercaptopropyltrimethoxysilane (MPTS), that were utilized to initiate the chain transfer free radical polymerization using poly(ethylene glycol) methyl ether methacrylate (PEGMA) and itaconic acid (IA) as the monomers. The successful modification of SBA-15 with poly(PEGMA-co-IA) copolymers was evidenced by a series of characterization techniques, including 1 H NMR, FT-IR, TGA and XPS. The final SBA-15-SH- poly(PEGMA-co-IA) composites display well water dispersity and high loading capability towards cisplatin (CDDP) owing to the introduction of hydrophilic PEGMA and carboxyl groups. Furthermore, the CDDP could be released from SBA-15-SH-poly(PEGMA-co-IA)-CDDP complexes in a pH dependent behavior, suggesting the potential controlled drug delivery of SBA-15-SH-poly(PEGMA-co-IA). More importantly, the strategy should be also useful for fabrication of many other functional materials for biomedical applications owing to the advantages of SBA-15 and well monomer adoptability of chain transfer free radical polymerization. Copyright © 2017 Elsevier B.V. All rights reserved.

Surface modification of nano-silica on the ligament advanced reinforcement system for accelerated bone formation: primary human osteoblasts testing in vitro and animal testing in vivo

NASA Astrophysics Data System (ADS)

Li, Mengmeng; Wang, Shiwen; Jiang, Jia; Sun, Jiashu; Li, Yuzhuo; Huang, Deyong; Long, Yun-Ze; Zheng, Wenfu; Chen, Shiyi; Jiang, Xingyu

2015-04-01

The Ligament Advanced Reinforcement System (LARS) has been considered as a promising graft for ligament reconstruction. To improve its biocompatibility and effectiveness on new bone formation, we modified the surface of a polyethylene terephthalate (PET) ligament with nanoscale silica using atom transfer radical polymerization (ATRP) and silica polymerization. The modified ligament is tested by both in vitro and in vivo experiments. Human osteoblast testing in vitro exhibits an ~21% higher value in cell viability for silica-modified grafts compared with original grafts. Animal testing in vivo shows that there is new formed bone in the case of a nanoscale silica-coated ligament. These results demonstrate that our approach for nanoscale silica surface modification on LARS could be potentially applied for ligament reconstruction.The Ligament Advanced Reinforcement System (LARS) has been considered as a promising graft for ligament reconstruction. To improve its biocompatibility and effectiveness on new bone formation, we modified the surface of a polyethylene terephthalate (PET) ligament with nanoscale silica using atom transfer radical polymerization (ATRP) and silica polymerization. The modified ligament is tested by both in vitro and in vivo experiments. Human osteoblast testing in vitro exhibits an ~21% higher value in cell viability for silica-modified grafts compared with original grafts. Animal testing in vivo shows that there is new formed bone in the case of a nanoscale silica-coated ligament. These results demonstrate that our approach for nanoscale silica surface modification on LARS could be potentially applied for ligament reconstruction. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01439e

Conjugation of arginine-glycine-aspartic acid peptides to poly(ethylene oxide)-b-poly(epsilon-caprolactone) micelles for enhanced intracellular drug delivery to metastatic tumor cells.

PubMed

Xiong, Xiao-Bing; Mahmud, Abdullah; Uludağ, Hasan; Lavasanifar, Afsaneh

2007-03-01

An arginine-glycine-aspartic acid (RGD) containing model peptide was conjugated to the surface of poly(ethylene oxide)-block-poly(epsilon-caprolactone) (PEO-b-PCL) micelles as a ligand that can recognize adhesion molecules overexpressed on the surface of metastatic cancer cells, that is, integrins, and that can enhance the micellar delivery of encapsulated hydrophobic drug into a tumor cell. Toward this goal, PEO-b-PCL copolymers bearing acetal groups on the PEO end were synthesized, characterized, and assembled to polymeric micelles. The acetal group on the surface of the PEO-b-PCL micelles was converted to reactive aldehyde under acidic condition at room temperature. An RGD-containing linear peptide, GRGDS, was conjugated on the surface of the aldehyde-decorated PEO-b-PCL micelles by incubation at room temperature. A hydrophobic fluorescent probe, that is, DiI, was physically loaded in prepared polymeric micelles to imitate hydrophobic drugs loaded in micellar carrier. The cellular uptake of DiI loaded GRGDS-modified micelles by melanoma B16-F10 cells was investigated at 4 and 37 degrees C by fluorescent spectroscopy and confocal microscopy techniques and was compared to the uptake of DiI loaded valine-PEO-b-PCL micelles (as the irrelevant ligand decorated micelles) and free DiI. GRGDS conjugation to polymeric micelles significantly facilitated the cellular uptake of encapsulated hydrophobic DiI most probably by intergrin-mediated cell attachment and endocytosis. The results indicate that acetal-terminated PEO-b-PCL micelles are amenable for introducing targeting moieties on the surface of polymeric micelles and that RGD-peptide conjugated PEO-b-PCL micelles are promising ligand-targeted carriers for enhanced drug delivery to metastatic tumor cells.

L’utilisation d’objets comme outils: un développement continu

PubMed Central

Kahrs, Björn Alexander; Lockman, Jeffrey J.

2014-01-01

Le débat autour des origines développementales de la capacité humaine à utiliser des outils de manière souple reste ouvert. Alors que l’approche dominante se focalise sur un changement qualitatif cognitif vers la fin de la première année, la théorie perception-action fournit des indices importants sur la manière dont les comportements exploratoires plus précoces des nourrissons jettent les bases pour l’émergence de cette capacité. En particulier, nous nous intéressons à la manière dont les tentatives des nourrissons de mettre en rapport les objets et les surfaces leur permettent d’apprendre comment les objets peuvent servir d’extension de la main et fournissent l’occasion d’exercer des actions qui seront recrutées plus tard pour l’utilisation d’outils. Dans ce contexte, nous discutons des études comportementales et cinématiques portant sur la manipulation d’objets, qui montrent que les nourrissons font interagir les objets et les surfaces avec discernement et que leur contrôle de la frappe (banging) augmente au cours de leur première année. En conclusion, une perspective perception-action suggère que l’utilisation d’outils émerge de manière plus continue au cours du développement que ce qui a été traditionnellement envisagé. PMID:24511151

Crystalline TiO 2 grafted with poly(2-methacryloyloxyethyl phosphorylcholine) via surface-initiated atom-transfer radical polymerization

NASA Astrophysics Data System (ADS)

Zhao, Yuancong; Tu, Qiufen; Wang, Jin; Huang, Qiongjian; Huang, Nan

2010-12-01

Crystalline TiO 2 films were prepared by unbalanced magnetron sputtering and the structure was confirmed by XRD. An organic layer of 11-hydroxyundecylphosphonic acid (HUPA) was prepared on the TiO 2 films by self-assembling, and the HUPA on TiO 2 films was confirmed by FTIR analysis. Simultaneously, hydroxyl groups were introduced in the phosphonic acid molecules to provide a functionality for further chemical modification. 2-Methacryloyloxyethyl phosphorylcholine (MPC), a biomimetic monomer, was chemically grafted on the HUPA surfaces at room temperature by surface-initiated atom-transfer radical polymerization. The surface characters of TiO 2 films modified by poly-MPC were confirmed by FTIR, XPS and SEM analysis. Platelet adhesion experiment revealed that poly-MPC modified surface was effective to inhibit platelet adhesion in vitro.

Method for providing mirror surfaces with protective strippable polymeric film

DOEpatents

Edwards, Charlene C.; Day, Jack R.

1980-01-01

This invention is a method for forming a protective, strippable, elastomeric film on a highly reflective surface. The method is especially well suited for protecting diamond-machined metallic mirrors, which are susceptible not only to abrasion and mechanical damage but also to contamination and corrosion by various fluids. In a typical use of the invention, a diamond-machined copper mirror surface is coated uniformly with a solution comprising a completely polymerized and completely cured thermoplastic urethane elastomer dissolved in tetrahydrofuran. The applied coating is evaporated to dryness, forming a tough, adherent, impermeable, and transparent film which encapsulates dust and other particulates on the surface. The film may be left in place for many months. When desired, the film may be stripped intact, removing the entrapped particulates and leaving no residue on the mirror surface.

Plasma Surface Modification of Polyaramid Fibers for Protective Clothing

NASA Astrophysics Data System (ADS)

Widodo, Mohamad

2011-12-01

The purpose of this research was to develop a novel process that would achieve biocidal properties on Kevlar fabric via atmospheric pressure plasma jet (APPJ) induced-graft polymerization of monomers. In the course of the study, experiments were carried out to understand plasma-monomer-substrate interactions, particularly, how each of the main parameters in the plasma processing affects the formation of surface radicals and eventually the degree of graft polymerization of monomers. The study also served to explore the possibility of developing plasma-initiated and plasma-controlled graft polymerization for continuous operation. In this regards, three methods of processing were studied, which included two-step plasma graft-polymerization with immersion, two-step and one-step plasma graft-polymerization with pad-dry. In general, plasma treatment did not cause visible damage to the surface of Kevlar fibers, except for the appearance of tiny globules distributed almost uniformly indicating a minor effect of plasma treatment to the surface morphology of the polymer. From the examination of SEM images, however, it was found that a very localized surface etching seemed to have taken place, especially at high RF power (800 W) and long time of exposure (60 s), even in plasma downstream mode of operation. It was suggested that a small amount of charged particles might have escaped and reached the substrate surface. High density of surface radicals, which is the prerequisite for high graft density and high antimicrobial activity, was achieved by the combination of high RF power and short exposure time or low RF power and long time of exposure. This was a clear indication that the formation of surface radicals is a function of amount of the dissipated energy, which also explained the two-factor interaction between the two process parameters. XPS results showed that hydrolysis of the anilide bond of PPTA chains took place to some extent on the surface of Kevlar, leading to the formation carboxylic and phenyl amine groups, which may provide additional active sites for grafting by way of hydrogen abstraction from the latter. Further analysis of XPS data, however, showed that macroradicals and active sites of grafting were formed at least at one of the carbon atoms in the aromatic ring. A reduction of microbial activity up to 3-log reduction was achieved by plasma treated Kevlar grafted by either diallyl diammonium chloride (DADMAC) or 3- ((trimethoxysilyl)-propyl) dimethylammonium chloride (TMS), with the latter being the one with better performance. It was found that high antimicrobial activity was obtained by the combination of high RF power, short time of exposure, and low concentration of monomer. Of the three processing methods studied, the one with immersion method produced higher graft yield. However, one-step plasma graft-polymerization with pad-dry method has proven itself more interesting due to its potential for an open continuous process. This research has been successful in producing effective antimicrobial properties on Kevlar fabric by plasma-initiated and plasma-controlled graft polymerization, which is unprecedented. The design of experiments showed that better results with higher order of log reduction can be obtained by process optimization, e.g. by using response surface methods. It would also be very beneficial to continue the research for the development of plasma graft-polymerization process with more rigorous design, which involves the use of crosslinker and antimicrobial monomers with different chemistry. A study that involves the development of a robust design for processes that perform consistently as intended under a wide range of user's conditions and yet produce high-level performance with high reliability would also be advantageous. The major implication of the findings from this research for the finishing of Kevlar is that a wide array of different surface functionalities may become more readily available now than ever. Plasma technology has made surface chemistry functionalization of Kevlar more straightforward and easier to perform, which opens new avenues for achieving functional and multifunctional Kevlar fabrics using a fast, more economic and environmentally friendly continuous process for niche market such as military applications and protective clothing for emergency responders.

In Situ Preparation of Biomimetic Thin Films and Their Surface-Shielding Effect for Organisms in High Vacuum

PubMed Central

Muranaka, Yoshinori; Shimomura, Masatsugu; Hariyama, Takahiko

2013-01-01

Self-standing biocompatible films have yet to be prepared by physical or chemical vapor deposition assisted by plasma polymerization because gaseous monomers have thus far been used to create only polymer membranes. Using a nongaseous monomer, we previously found a simple fabrication method for a free-standing thin film prepared from solution by plasma polymerization, and a nano-suit made by polyoxyethylene (20) sorbitan monolaurate can render multicellular organisms highly tolerant to high vacuum. Here we report thin films prepared by plasma polymerization from various monomer solutions. The films had a flat surface at the irradiated site and were similar to films produced by vapor deposition of gaseous monomers. However, they also exhibited unique characteristics, such as a pinhole-free surface, transparency, solvent stability, flexibility, and a unique out-of-plane molecular density gradient from the irradiated to the unirradiated surface of the film. Additionally, covering mosquito larvae with the films protected the shape of the organism and kept them alive under the high vacuum conditions in a field emission-scanning electron microscope. Our method will be useful for numerous applications, particularly in the biological sciences. PMID:24236023

Distribution of Chains in Polymer Brushes Produced by a “Grafting From” Mechanism

DOE PAGES

Martinez, Andre P.; Carrillo, Jan-Michael Y.; Dobrynin, Andrey V.; ...

2016-01-11

The molecular weight and polydispersity of the chains in a polymer brush are critical parameters determining the brush properties. However, the characterization of polymer brushes is hindered by the vanishingly small mass of polymer present in brush layers. In this study, in order to obtain sufficient quantities of polymer for analysis, polymer brushes were grown from high surface area fibrous nylon membranes by ATRP. We synthesized the brushes with varying surface initiator densities, polymerization times, and amounts of sacrificial initiator, then cleaved from the substrate, and analyzed by GPC and NMR. Characterization showed that the surface-grown polymer chains were moremore » polydisperse and had lower average molecular weight compared to solution-grown polymers synthesized concurrently. Furthermore, the molecular weight distribution of the polymer brushes was observed to be bimodal, with a low molecular weight population of chains representing a significant mass fraction of the polymer chains at high surface initiator densities. Moreover, the origin of this low MW polymer fraction is proposed to be the termination of growing chains by recombination during the early stages of polymerization, a mechanism confirmed by molecular dynamics simulations of brush polymerization.« less

Durcissement superficiel de la fonte grise Ft25 induit par un traitement de surface dans le moule

NASA Astrophysics Data System (ADS)

Bouitna, Mohamed; Boutarek-Zaourar, Naïma; Mansour, Samir; Chentouf, Samir Mourad; Mossang, Eric

2018-02-01

L'objectif de cette étude est la consolidation en surface de la fonte grise lamellaire Ft25 par un dépôt riche en manganèse en développant une méthode combinant en une seule opération l'élaboration et le traitement de surface dans le moule. Les effets de la granulométrie du ferro-manganèse (80 % Mn + 20 % Fe), ainsi que l'épaisseur des pièces en fontes sur les couches formées ont été étudiés. On a retenu trois granulométries du ferro-manganèse de 0,18 mm, 0,25 mm et 0,5 mm pour le traitement des pièces en fontes présentant des épaisseurs de 25 mm, 100 mm et 200 mm. Parmi les résultats obtenus, on distingue une consolidation des propriétés en surface induite par la formation d'une couche riche en manganèse continue et homogène. L'effet de la granulométrie du ferro-manganèse sur l'épaisseur de la couche traitée a été mis en évidence. La variation de l'épaisseur des couches formées diminue avec l'augmentation de la granulométrie du ferro-manganèse. Pour une pièce de 100 mm d'épaisseur, la couche formée est estimée à 350 μm pour une granulométrie de 0,18 alors qu'elle n'est que de 180 μm pour une granulométrie de 0,5. L'effet de l'épaisseur de la pièce n'est en revanche pas assez prononcé sur la taille des couches formées. Une amélioration nette de la résistance, à l'usure de la fonte traitée en relation avec les transformations en surface, a été mise en évidence.

The effect of polymer surface modification on polymer-protein interaction via interfacial polymerization and hydrophilic polymer grafting

USDA-ARS?s Scientific Manuscript database

Protein membrane separation is prone to fouling on the membrane surface resulting from protein adsorption onto the surface. Surface modification of synthetic membranes is one way to reduce fouling. We investigated surface modification of polyethersulfone (PES) as a way of improving hydrophilicity ...

Biodegradable polymeric microsphere-based vaccines and their applications in infectious diseases

PubMed Central

Lin, Chi-Ying; Lin, Shih-Jie; Yang, Yi-Chen; Wang, Der-Yuan; Cheng, Hwei-Fang; Yeh, Ming-Kung

2015-01-01

Vaccination, which provides effective, safe infectious disease protection, is among the most important recent public health and immunological achievements. However, infectious disease remains the leading cause of death in developing countries because several vaccines require repeated administrations and children are often incompletely immunized. Microsphere-based systems, providing controlled release delivery, can obviate the need for repeat immunizations. Here, we review the function of sustained and pulsatile release of biodegradable polymeric microspheres in parenteral and mucosal single-dose vaccine administration. We also review the active-targeting function of polymeric particles. With their shield and co-delivery functions, polymeric particles are applied to develop single-dose and mucosally administered vaccines as well as to improve subunit vaccines. Because polymeric particles are easily surface-modified, they have been recently used in vaccine development for cancers and many infectious diseases without effective vaccines (e.g., human immunodeficiency virus infection). These polymeric particle functions yield important vaccine carriers and multiple benefits. PMID:25839217

Applications of polymeric micelles with tumor targeted in chemotherapy

NASA Astrophysics Data System (ADS)

Ding, Hui; Wang, Xiaojun; Zhang, Song; Liu, Xinli

2012-11-01

Polymeric micelles (PMs) have gained more progress as a carrier system with the quick development of biological and nanoparticle techniques. In particular, PMs with smart targeting can deliver anti-cancer drugs directly into tumor cells at a sustained rate. PMs with core-shell structure (with diameters of 10 100 nm) have been prepared by a variety of biodegradable and biocompatible polymers via a self-assembly process. The preparation of polymeric micelles with stimuli-responsive block copolymers or modification of target molecules on polymeric micelles' surface are able to significantly improve the efficiency of drug delivery. Polymeric micelles, which have been considered as a novel promising drug carrier for cancer therapeutics, are rapidly evolving and being introduced in an attempt to overcome several limitations of traditional chemotherapeutics, including water solubility, tumor-specific accumulation, anti-tumor efficacy, and non-specific toxicity. This review describes the preparation of polymeric micelles and the targeted modification which greatly enhance the effects of chemotherapeutic agents.

Polymeric carbon nitride for solar hydrogen production.

PubMed

Li, Xiaobo; Masters, Anthony F; Maschmeyer, Thomas

2017-07-04

If solar hydrogen production from water is to be a realistic candidate for industrial hydrogen production, the development of photocatalysts, which avoid the use of expensive and/or toxic elements is highly desirable from a scalability, cost and environmental perspective. Metal-free polymeric carbon nitride is an attractive material that can absorb visible light and produce hydrogen from water. This article reviews recent developments in polymeric carbon nitride as used in photocatalysis and then develops the discussion focusing on the three primary processes of a photocatalytic reaction: light-harvesting, carrier generation/separation/transportation and surface reactions.

Fabricating small-scale, curved, polymeric structures with convex and concave menisci through interfacial free energy equilibrium.

PubMed

Cheng, Chao-Min; Matsuura, Koji; Wang, I-Jan; Kuroda, Yuka; LeDuc, Philip R; Naruse, Keiji

2009-11-21

Polymeric curved structures are widely used in imaging systems including optical fibers and microfluidic channels. Here, we demonstrate that small-scale, poly(dimethylsiloxane) (PDMS)-based, curved structures can be fabricated through controlling interfacial free energy equilibrium. Resultant structures have a smooth, symmetric, curved surface, and may be convex or concave in form based on surface tension balance. Their curvatures are controlled by surface characteristics (i.e., hydrophobicity and hydrophilicity) of the molds and semi-liquid PDMS. In addition, these structures are shown to be biocompatible for cell culture. Our system provides a simple, efficient and economical method for generating integrateable optical components without costly fabrication facilities.

Crumb waste tire rubber surface modification by plasma polymerization of ethanol and its application on oil-well cement

NASA Astrophysics Data System (ADS)

Xiaowei, Cheng; Sheng, Huang; Xiaoyang, Guo; Wenhui, Duan

2017-07-01

Crumb waste tire rubber (WTR) was pretreated by oxygen low temperature plasma (LTP) and modified by LTP polymerization process of ethanol monomer to improve the adhesion property with oil-well cement matrix and the mechanical properties of cement. The surface properties of modified crumb WTR and the mechanical properties and structures of modified oil-well cement were investigated by means of contact angle measurement, dispersion test, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), mechanics performance tests, permeability test and scanning electron microscopy (SEM). It was demonstrated that LTP treatment changed both the surface composition and roughness. The contact angle of pretreated crumb WTR dramatically fell from 122° to 34°, and sample with ethanol LPT polymer film decreased even further to 11°. The ATR-FTIR and XPS analysis results demonstrated that hydrophilic groups, such as -COOH, C-OH, and -CHO, were introduced on the WTR surface. The oxygen atomic percent increased from 8.11% to 14.50% and 24.83%. The mechanical properties, porosity and permeability of raw cement were compared to samples modified by untreated crumb WTR, pretreated crumb WTR and ethanol LTP polymerization treated crumb WTR. It was found that after 28 days, the compressive strength of the samples with the untreated crumb WTR decreased to 80% with respect to raw cement. The tensile strength and flexural strength also had a slight reduction compared with the raw cement. On the contrary, after 28 days, the tensile strength of cement modified by LTP polymerization treated WTR increased 11.03% and 13.36%, and the flexural strength increased 9.65% and 7.31%, respectively. A decrease in the compressive strength also occurred but was inconspicuous. A tight interface bonding for ethanol LTP polymerization treated WTR with cement matrix was observed via an SEM image.

Functionalizing the Surface of Lithium-Metal Anodes

DOE PAGES

Buonaiuto, Megan; Neuhold, Susanna; Schroeder, David J.; ...

2014-09-03

Metal-air batteries are an important aspect of many beyond lithium ion research efforts. However, as our understanding of how molecular oxygen can act as a rechargeable cathode has progressed; the problems associated with how these materials at various states of charge interact with the lithium metal anode are only beginning to come to the surface. In this study we have devised a method to coat the surface a lithium with a functional group to act as either an anchor for further derivation studies or be polymerized to create a nanometer thick polymer coating attached to the surface by silane groups.more » These stable films, formed by polymerization of vinyl substituents, lower cell impedance at the electrode and over the first 50 cycles, increase cycling efficiency and demonstrate lower capacity fade.« less

Acrylic acid plasma polymerization for biomedical use

NASA Astrophysics Data System (ADS)

Bitar, Rim; Cools, Pieter; De Geyter, Nathalie; Morent, Rino

2018-08-01

Since a few decades, polymeric materials have played a central role in regenerative medicine and tissue engineering as artificial tissue replacements and organ transplantation devices. Chemical and topographical surface modifications of biomaterials are often required to achieve an overall better biocompatibility. Non-thermal plasma is a non-invasive, solvent-free alternative for modifying polymeric surface properties without affecting the bulk of the material. Plasma polymerization of organic compounds has proven to be an effective tool for thin film production with specific surface chemistries, useful for biomedical applications. These polymer layers have received a growing interest in tissue regeneration and biomolecules immobilization processes. Many different types of chemical functional groups can be introduced, but the focus of this review will be on carboxylic acid groups. Thin films consisting of carboxylic acid functional groups are considered attractive for biomedical applications since these are known for stimulating the adhesion and proliferation of fibroblasts and other kind of cells. Therefore, an overview on the use of acrylic acid (AAc) as a precursor or for the plasma-assisted deposition of carboxylic-group containing-films in bio-interface research activities, will be described in this review. The review will specifically focus on plasma polymerized acrylic acid (PPAA) coatings that are obtained using a variety of plasma deposition techniques. Moreover, the influence of plasma parameters on surface properties such as wettability, surface topography and chemical composition will be discussed in detail. The correlation between different parameters will be studied and a general recipe leading to the successful deposition of COOH-rich stable coatings will be extracted and linked to their ability to improve cell growth, proliferation and differentiation, all leading to the further progress in the biomedical field. A lot of publications claim to have developed suitable coatings for biomedical applications, but neglect the importance of coating stability. For those publications exhibiting sufficient coating stability, a lot of initial in vitro experiments were performed, but the number in-depth studies on the mechanisms behind the cell-material interactions is limited. Although AAc forms an excellent precursor for biomedical coatings, its potential still needs to be explored in more details.

Surface-induced polymerization of actin.

PubMed Central

Renault, A; Lenne, P F; Zakri, C; Aradian, A; Vénien-Bryan, C; Amblard, F

1999-01-01

Living cells contain a very large amount of membrane surface area, which potentially influences the direction, the kinetics, and the localization of biochemical reactions. This paper quantitatively evaluates the possibility that a lipid monolayer can adsorb actin from a nonpolymerizing solution, induce its polymerization, and form a 2D network of individual actin filaments, in conditions that forbid bulk polymerization. G- and F-actin solutions were studied beneath saturated Langmuir monolayers containing phosphatidylcholine (PC, neutral) and stearylamine (SA, a positively charged surfactant) at PC:SA = 3:1 molar ratio. Ellipsometry, tensiometry, shear elastic measurements, electron microscopy, and dark-field light microscopy were used to characterize the adsorption kinetics and the interfacial polymerization of actin. In all cases studied, actin follows a monoexponential reaction-limited adsorption with similar time constants (approximately 10(3) s). At a longer time scale the shear elasticity of the monomeric actin adsorbate increases only in the presence of lipids, to a 2D shear elastic modulus of mu approximately 30 mN/m, indicating the formation of a structure coupled to the monolayer. Electron microscopy shows the formation of a 2D network of actin filaments at the PC:SA surface, and several arguments strongly suggest that this network is indeed causing the observed elasticity. Adsorption of F-actin to PC:SA leads more quickly to a slightly more rigid interface with a modulus of mu approximately 50 mN/m. PMID:10049338

Evaluation of Ocean Models Using Observed and Simulated Drifter Trajectories: Impact of Sea Surface Height on Synthetic Profiles for Data Assimilation

DTIC Science & Technology

2007-07-17

in the study of Lumpkin and North Atlantic 0°-80’N 100*-0°W 29 Pazos [2007]. North Brazil Current 00-20ON 70°-40OW 36 [IS] Simulated trajectories are...ShelfRes., 21, 47-67. field. The observed drifter is a sample among many possible Lumpkin, R., and M. Pazos (2007), Measuring surface currents with Sur

Interfacial Stacks of Polymeric Nanofilms on Soft Biological Surfaces that Release Multiple Agents.

PubMed

Herron, Maggie; Schurr, Michael J; Murphy, Christopher J; McAnulty, Jonathan F; Czuprynski, Charles J; Abbott, Nicholas L

2016-10-03

We report a general and facile method that permits the transfer (stacking) of multiple independently fabricated and nanoscopically thin polymeric films, each containing a distinct bioactive agent, onto soft biomedically relevant surfaces (e.g., collagen-based wound dressings). By using polyelectrolyte multilayer films (PEMs) formed from poly(allyl amine hydrochloride) and poly(acrylic acid) as representative polymeric nanofilms and micrometer-thick water-soluble poly(vinyl alcohol) sacrificial films to stack the PEMs, we demonstrate that it is possible to create stacked polymeric constructs containing multiple bioactive agents (e.g., antimicrobial and antibiofilm agents) on soft and chemically complex surfaces onto which PEMs cannot be routinely transferred by stamping. We illustrate the characteristics and merits of the approach by fabricating stacks of Ga 3+ (antibiofilm agent)- and Ag + (antimicrobial agent)-loaded PEMs as prototypical examples of agent-containing PEMs and demonstrate that the stacked PEMs incorporate precise loadings of the agents and provide flexibility in terms of tuning release rates. Specifically, we show that simultaneous release of Ga 3+ and Ag + from the stacked PEMs on collagen-based wound dressings can lead to synergistic effects on bacteria, killing and dispersing biofilms formed by Pseudomonas aeruginosa (two strains: ATCC 27853 and MPAO1) at sufficiently low loadings of agents such that cytotoxic effects on mammalian cells are avoided. The approach is general (a wide range of bioactive agents other than Ga 3+ and Ag + can be incorporated into PEMs), and the modular nature of the approach potentially allows end-user functionalization of soft biological surfaces for programmed release of multiple bioactive agents.

Analyse chronometrique intersexes de la resolution de la tache d'horizontalite des liquides

NASA Astrophysics Data System (ADS)

Berthiaume, Francois

D'abondantes recherches ont demontre que la reussite a la tache d'horizontalite des liquides est en moyenne plus elevee chez les individus de sexe masculin que chez ceux de sexe feminin. Deux facteurs principaux ont ete proposes: il s'agit de la connaissance du principe physique de l'invariance de l'orientation des liquides et de certaines habiletes perceptives d'ordre visuel. Le but de la presente recherche est d'etablir la duree detaillee de la resolution de la tache d'horizontalite des liquides chez 185 filles et 180 garcons, ages de 15 a 19 ans et repartis en 8 groupes. Dans une version informatisee, le premier groupe trace la position de la surface de l'eau a l'interieur d'un contenant dans diverses inclinaisons et le deuxieme evalue si l'orientation d'une ligne y represente bien cette position; le troisieme groupe trace une horizontale dans un rectangle et le quatrieme juge si la ligne illustree y est bien horizontale. Quatre autres groupes executent respectivement les memes taches dans la version classique papier-crayon. Le temps accorde a la reflexion avant de commencer le trace, le temps de tracage comme tel et le temps de verification du trace complete sont calcules. Chez les groupes qui evaluent l'orientation d'une ligne sur support informatique, le temps requis pour y parvenir est note. Enfin, un questionnaire estime si les participants connaissent ou non le principe physique d'invariance de l'orientation de la surface d'un liquide. Les resultats revelent que cette connaissance est plus frequente chez les garcons dans l'ensemble des groupes. Dans le cas ou les sujets ont a tracer une ligne, les filles reussissent moins d'essais que les garcons s'il faut, sur support informatique, tracer la surface de l'eau dans un contenant incline ou a l'horizontale. Il en va de meme s'il faut, sur support papier, tracer une horizontale dans un contenant incline. Le trace de la surface de l'eau est plus exact chez les sujets connaissant le principe d'invariance et l'ecart intersexes disparait si l'analyse tient compte de cette connaissance. Sur le plan du temps de reponse, les deux sexes ne se distinguent que lors du trace de la surface de l'eau dans un contenant incline, les garcons reflechissant alors plus longtemps. Le temps mis a produire, puis a verifier un trace, ne differe pas selon le sexe des participants. Dans l'evaluation de l'orientation d'une ligne cependant, les filles ne se distinguent pas des garcons et les participants connaissant le principe d'invariance reussissent mieux que ceux l'ignorant. Par ailleurs, les filles procedent toujours moins rapidement que les garcons. Pour les contenants inclines ou a l'horizontale, si la ligne represente la surface de l'eau, la difference intersexes est annulee quand la connaissance du principe est prise en compte. (Abstract shortened by UMI.)

Covalent bonding of polycations to small polymeric particles

NASA Technical Reports Server (NTRS)

Rembaum, A.

1975-01-01

Process produces small spherical polymeric particles which have polycations bound to them. In emulsion form, particles present large positively charged surface which is available to absorb polyanions. This properly can be used in removing heparin from blood or bile acids from the digestive tract. Other anions, such as DNA and RNA, can also be removed from aqueous solutions.

Polymeric Microcapsule Arrays.

DTIC Science & Technology

1995-03-24

support, microencapsulation and entrapment within a membrane/film or gel. The ideal enzyme immobilization method would (1) Employ mild chemical...yields hollow polymeric microcapsules of uniform diameter and length. These microcapsules are arranged in a high density array in which the...individual capsules protrude from a surface like the bristles of a brush. We have developed procedures for filling these microcapsules with high

Soy-based polymeric surfactants prepared in carbon dioxide media and influence of structure on their surface properties

USDA-ARS?s Scientific Manuscript database

Soybean oil (SO) and epoxidized soybean oil (ESO) were polymerized in the CO2 media (supercritical and sub-supercritical) by BF3•OEt2 catalyst. The resulting polymers (PSO and PESO) were hydrolyzed into polysoaps (HPSO) and (HPESO) with Na+, K+, or TEA+ (triethanolamine, ammonium salt) counter ions....

Poly(vinyl alcohol) stabilization of acrylic emulsion polymers using the miniemulsion approach

NASA Astrophysics Data System (ADS)

Kim, Noma

Miniemulsion approach was employed to obtain stable acrylic latexes of n-butyl acrylate and methyl methacrylate (50/50 wt%) stabilized with poly(vinyl alcohol) (PVA) and to enhance the grafting reaction between PVA and acrylic monomers at the water/droplet interface. The stability of miniemulsions were studied in terms of the type and concentration of' the stabilizer, and the PVA partitioning were determined as a function of the PVA concentration. Using the comparison of PVA partitioning at droplet surface and grafted PVA as a function of concentration, it was suggested that the water/monomer interface is the main grafting site in the miniemulsion polymerization. Seeded emulsion and miniemulsion copolymerizations initiated with water-soluble (hydrogen peroxide, HPO), partially water-soluble (t-butyl peroxide, TBHP), and oil-soluble (t-butyl peroxyoctoate, TBPO) initiators were carried out to further investigate the oil/water interface as the grafting site for PVA. The interaction between the capillary wall in the CHDF (capillary hydrodynamic fractionation) chromatographic particle sizer and the water-soluble polymers adsorbed on the particle surface was studied using different types of water-soluble polymers and eluants. Different grafting architectures depending on the initiation site were suggested based on the CHDF results. The amounts of grafted PVA produced in miniemulsion polymers initiated with TBHP and TBPO were substantially less than those in the corresponding seeded emulsion polymerizations. The effect on the internal viscosity at the interface was proposed to explain the difference in grafting in terms of polymerization methods. Aqueous phase and interface grafting were studied using the measurement of the degree of hydrolysis (DH) of the serum PVA and adsorbed PVA after miniemulsion polymerizations. Based on the results, it was found that aqueous phase and interface grafting occurred in the HPO system; however, interface grafting dominated the TBHP system. Colloidal instability in conventional emulsion polymerizations was investigated and compared with the corresponding miniemulsion polymerization. It was found that the grafted PVA in conventional emulsion polymerizations was more hydrophobic presumably due to a greater amount of grafted chains than that in similar miniemulsion polymerizations and this could be correlated with the colloidal instability during conventional emulsion polymerizations.

A general strategy to synthesize chemically and topologically anisotropic Janus particles

PubMed Central

Fan, Jun-Bing; Song, Yongyang; Liu, Hong; Lu, Zhongyuan; Zhang, Feilong; Liu, Hongliang; Meng, Jingxin; Gu, Lin; Wang, Shutao; Jiang, Lei

2017-01-01

Emulsion polymerization is the most widely used synthetic technique for fabricating polymeric particles. The interfacial tension generated with this technique limits the ability to tune the topology and chemistry of the resultant particles. We demonstrate a general emulsion interfacial polymerization approach that involves introduction of additional anchoring molecules surrounding the microdroplets to synthesize a large variety of Janus particles with controllable topological and chemical anisotropy. This strategy is based on interfacial polymerization mediated by an anchoring effect at the interface of microdroplets. Along the interface of the microdroplets, the diverse topology and surface chemistry features of the Janus particles can be precisely tuned by regulating the monomer type and concentration as well as polymerization time. This method is applicable to a wide variety of monomers, including positively charged, neutrally charged, and negatively charged monomers, thereby enriching the community of Janus particles. PMID:28691089

Development of a multilayered polymeric DNA biosensor using radio frequency technology with gold and magnetic nanoparticles.

PubMed

Yang, Cheng-Hao; Kuo, Long-Sheng; Chen, Ping-Hei; Yang, Chii-Rong; Tsai, Zuo-Min

2012-01-15

This study utilized the radio frequency (RF) technology to develop a multilayered polymeric DNA sensor with the help of gold and magnetic nanoparticles. The flexible polymeric materials, poly (p-xylylene) (Parylene) and polyethylene naphtholate (PEN), were used as substrates to replace the conventional rigid substrates such as glass and silicon wafers. The multilayered polymeric RF biosensor, including the two polymer layers and two copper transmission structure layers, was developed to reduce the total sensor size and further enhance the sensitivity of the biochip in the RF DNA detection. Thioglycolic acid (TGA) was used on the surface of the proposed biochip to form a thiolate-modified sensing surface for DNA hybridization. Gold nanoparticles (AuNPs) and magnetic nanoparticles (MNPs) were used to immobilize on the surface of the biosensor to enhance overall detection sensitivity. In addition to gold nanoparticles, the magnetic nanoparticles has been demonstrated the applicability for RF DNA detection. The performance of the proposed biosensor was evaluated by the shift of the center frequency of the RF biosensor because the electromagnetic characteristic of the biosensors can be altered by the immobilized multilayer nanoparticles on the biosensor. The experimental results show that the detection limit of the DNA concentration can reach as low as 10 pM, and the largest shift of the center frequency with triple-layer AuNPs and MNPs can approach 0.9 and 0.7 GHz, respectively. Such the achievement implies that the developed biosensor can offer an alternative inexpensive, disposable, and highly sensitive option for application in biomedicine diagnostic systems because the price and size of each biochip can be effectively reduced by using fully polymeric materials and multilayer-detecting structures. Copyright © 2011 Elsevier B.V. All rights reserved.

Nateglinide, a D-phenylalanine derivative lacking either a sulfonylurea or benzamido moiety, specifically inhibits pancreatic beta-cell-type K(ATP) channels.

PubMed

Chachin, Motohiko; Yamada, Mitsuhiko; Fujita, Akikazu; Matsuoka, Tetsuro; Matsushita, Kenji; Kurachi, Yoshihisa

2003-03-01

A novel antidiabetic agent, nateglinide, is a D-phenylalanine derivative lacking either a sulfonylurea or benzamido moiety. We examined with the patch-clamp method the effect of nateglinide on recombinant ATP-sensitive K(+) (K(ATP)) channels expressed in human embryonic kidney 293T cells transfected with a Kir6.2 subunit and either of a sulfonylurea receptor (SUR) 1, SUR2A, and SUR2B. In inside-out patches, nateglinide reversibly inhibited the spontaneous openings of all three types of SUR/Kir6.2 channels. Nateglinide inhibited SUR1/Kir6.2 channels with high and low affinities (K(i) = 75 nM and 114 microM) but SUR2A/Kir6.2 and SUR2B/Kir6.2 channels only with low affinity (K(i) = 105 and 111 microM, respectively). Nateglinide inhibited the K(ATP) current mediated by Kir6.2 lacking C-terminal 26 amino acids only with low affinity (K(i) = 290 microM) in the absence of SUR. Replacement of serine at position 1237 of SUR1 to tyrosine [SUR1(S1237Y)] specifically abolished the high-affinity inhibition of SUR1/Kir6.2 channels by nateglinide. MgADP or MgUDP (100 microM) augmented the inhibitory effect of nateglinide on SUR1/Kir6.2 but not SUR1(S1237Y)/Kir6.2 or SUR2A/Kir6.2 channels. This augmenting effect of MgADP was also observed with the SUR1/Kir6.2(K185Q) channel, which was not inhibited by MgADP, but not with the SUR1(K1384A)/Kir6.2 channel, which was not activated by MgADP. These results indicate that therapeutic concentrations of nateglinide (approximately 10 microM) may selectively inhibit pancreatic type SUR1/Kir6.2 channels through SUR1, especially when the channel is activated by intracellular MgADP, even though the agent does not contain either a sulfonylurea or benzamido moiety.

Electron spin resonance and electron spin echo modulation studies of N,N,N prime ,N prime -tetramethylbenzidine photoionization adsorbed at the interface of polymeric latices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baglioni, P.; Rivara-Minten, E.; Kevan, L.

1989-02-23

Electron spin resonance (ESR) and electron spin echo modulation (ESEM) of photoionized N,N,N{prime},N{prime}-tetramethylbenzidine (TMB) cation adsorbed at the interface of butadiene-acrylonitrile-methacrylic acid and butadiene-styrene-acrylic acid polymeric latices have been studied as a function of sodium dodecyl sulfate (SDS) concentration adsorbed at the latex interface. The photoionization yield of TMB in frozen latices mainly depends on the strength of TMB{sup +}-water interactions, which are enhanced by added SDS as measured by ESEM. An increase in the negative surface potential of the latex particles, due to the adsorption of SDS at the latex surface, does not affect the photoionization yield, showing thatmore » the particle surface potential has, for negatively charged systems, a secondary role in promoting the photoionization yield. Differences in the TMB{sup +} yield are found for the two polymeric latices and are attributed to the different latex compositions and/or different interfacial structures.« less

Morphology and Surface Energy of a Si Containing Semifluorinated Di-block Copolymer Thin Films.

NASA Astrophysics Data System (ADS)

Shrestha, Umesh; Clarson, Stephen; Perahia, Dvora

2013-03-01

The structure and composition of an interface influence stability, adhesiveness and response to external stimuli of thin polymeric films. Incorporation of fluorine affects interfacial energy as well as thermal and chemical stability of the layers. The incompatibility between the fluorinated and non-fluorinated blocks induces segregation that leads to long range correlations where the tendency of the fluorine to migrate to interfaces impacts the surface tension of the films. Concurrently Si in a polymeric backbone enhances the flexibility of polymeric chains. Our previous studies of poly trifluoro propyl methyl siloxane-polystyrene thin films with SiF fraction 0.03-0.5 as a function of temperature have shown that the SiF block drives layering parallel to the surface of the diblock. Here in we report the structure and interfacial energies of SiF-PS in the plane of the films, as a function of the volume fraction of the SiF block obtained from Atomic Force microscopy and contact angle measurement studies. This work is supported by NSF DMR - 0907390

The Role of the Polymeric Immunoglobulin Receptor and Secretory Immunoglobulins during Mucosal Infection and Immunity.

PubMed

Turula, Holly; Wobus, Christiane E

2018-05-03

The gastrointestinal tract houses millions of microbes, and thus has evolved several host defense mechanisms to keep them at bay, and prevent their entry into the host. One such mucosal surface defense is the secretion of secretory immunoglobulins (SIg). Secretion of SIg depends on the polymeric immunoglobulin receptor (pIgR), which transports polymeric Ig (IgA or IgM) from the basolateral surface of the epithelium to the apical side. Upon reaching the luminal side, a portion of pIgR, called secretory component (SC) is cleaved off to release Ig, forming SIg. Through antigen-specific and non-specific binding, SIg can modulate microbial communities and pathogenic microbes via several mechanisms: agglutination and exclusion from the epithelial surface, neutralization, or via host immunity and complement activation. Given the crucial role of SIg as a microbial scavenger, some pathogens also evolved ways to modulate and utilize pIgR and SIg to facilitate infection. This review will cover the regulation of the pIgR/SIg cycle, mechanisms of SIg-mediated mucosal protection as well as pathogen utilization of SIg.

Enhanced linearly polarized lasing emission from nanoimprinted surface-emitting distributed feedback laser based on polymeric liquid crystals

NASA Astrophysics Data System (ADS)

Jeong, Soon Moon; Ha, Na Young; Chee, Mu Guen; Araoka, Fumito; Ishikawa, Ken; Takezoe, Hideo; Nishimura, Suzushi; Suzaki, Goro

2008-12-01

The authors have demonstrated the enhancement of linearly polarized lasing emission intensity using a structure made by a simple fabrication process. The enhanced lasing is achieved using a nanoimprinted distributed feedback structure together with spin-coated polymeric liquid crystals. The backward linearly TE-polarized lasing emission is transformed to left-handed circularly polarized light (L-CPL) by employing a dye-doped polymeric nematic liquid crystal (PNLC) film as a (-1/4)λ[=(3/4)λ] plate. The L-CPL is effectively reflected by a L-polymeric cholesteric liquid crystal film as a reflector and transformed back to TE-polarized light by the PNLC film; as a result one-directional emission intensity is enhanced.

NMR relaxation dispersion of Miglyol molecules confined inside polymeric micro-capsules.

PubMed

Nechifor, Ruben; Ardelean, Ioan; Mattea, Carlos; Stapf, Siegfried; Bogdan, Mircea

2011-11-01

Frequency dependent NMR relaxation studies have been carried out on Miglyol molecules confined inside core shell polymeric capsules to obtain a correlation between capsule dimension and the measurable parameters. The polymeric capsules were prepared using an interfacial polymerization technique for three different concentrations of Miglyol. It was shown that the variation of Miglyol concentration influences the capsule dimension. Their average size was estimated using the pulsed field gradient diffusometry technique. The relaxation dispersion curves were obtained at room temperature by a combined use of a fast field cycling instrument and a high-field instrument. The frequency dependence of relaxation rate shows a transition from a diffusion-limited to a surface-limited relaxation regime. Copyright © 2011 John Wiley & Sons, Ltd.

Lasing properties of polymerized chiral nematic Bragg onion microlasers.

PubMed

Humar, Matjaž; Araoka, Fumito; Takezoe, Hideo; Muševič, Igor

2016-08-22

Dye doped photocurable cholesteric liquid crystal was used to produce solid Bragg onion omnidirectional lasers. The lasers were produced by dispersing and polymerizing chiral nematic LC with parallel surface anchoring of LC molecules at the interface, extracted and transferred into another medium. Lasing characteristics were studied in carrier medium with different refractive index. The lasing in spherical cholesteric liquid crystal was attributed to two mechanisms, photonic bandedge lasing and lasing of whispering-gallery modes. The latter can be suppressed by using a higher index carrier fluid to prevent total internal reflection on the interface of the spheres. Pulse-to-pulse stability and threshold characteristics were also studied and compared to non-polymerized lasers. The polymerization process greatly increases the lasing stability.

Ion Beam Sputtered Coatings of Bioglass

NASA Technical Reports Server (NTRS)

Hench, Larry L.; Wilson, J.; Ruzakowski, Patricia Henrietta Anne

1982-01-01

The ion beam sputtering technique available at the NASA-Lewis was used to apply coatings of bioglass to ceramic, metallic, and polymeric substrates. Experiments in vivo and in vitro described investigate these coatings. Some degree of substrate masking was obtained in all samples although stability and reactivity equivalent to bulk bioglass was not observed in all coated samples. Some degree of stability was seen in all coated samples that were reacted in vitro. Both metallic and ceramic substrates coated in this manner failed to show significantly improved coatings over those obtained with existing techniques. Implantation of the coated ceramic substrate samples in bone gave no definite bonding as seen with bulk glass; however, partial and patchy bonding was seen. Polymeric substrates in these studies showed promise of success. The coatings applied were sufficient to mask the underlying reactive test surface and tissue adhesion of collagen to bioglass was seen. Hydrophilic, hydrophobic, charged, and uncharged polymeric surfaces were successfully coated.

Enhancement of Fluorescence-Based Sandwich Immunoassay Using Multilayered Microplates Modified with Plasma-Polymerized Films

PubMed Central

Yano, Kazuyoshi; Iwasaki, Akira

2016-01-01

A functional modification of the surface of a 96-well microplate coupled with a thin layer deposition technique is demonstrated for enhanced fluorescence-based sandwich immunoassays. The plasma polymerization technique enabling the deposition of organic thin films was employed for the modification of the well surface of a microplate. A silver layer and a plasma-polymerized film were consecutively deposited on the microplate as a metal mirror and the optical interference layer, respectively. When Cy3-labeled antibody was applied to the wells of the resulting multilayered microplate without any immobilization step, greatly enhanced fluorescence was observed compared with that obtained with the unmodified one. The same effect could be also exhibited for an immunoassay targeting antigen directly adsorbed on the multilayered microplate. Furthermore, a sandwich immunoassay for the detection of interleukin 2 (IL-2) was performed with the multilayered microplates, resulting in specific and 88-fold–enhanced fluorescence detection. PMID:28029144

Bloch surface waves confined in one dimension with a single polymeric nanofibre

PubMed Central

Wang, Ruxue; Xia, Hongyan; Zhang, Douguo; Chen, Junxue; Zhu, Liangfu; Wang, Yong; Yang, Erchan; Zang, Tianyang; Wen, Xiaolei; Zou, Gang; Wang, Pei; Ming, Hai; Badugu, Ramachandram; Lakowicz, Joseph R.

2017-01-01

Polymeric fibres with small radii (such as ≤125 nm) are delicate to handle and should be laid down on a solid substrate to obtain practical devices. However, placing these nanofibres on commonly used glass substrates prevents them from guiding light. In this study, we numerically and experimentally demonstrate that when the nanofibre is placed on a suitable dielectric multilayer, it supports a guided mode, a Bloch surface wave (BSW) confined in one dimension. The physical origin of this new mode is discussed in comparison with the typical two-dimensional BSW mode. Polymeric nanofibres are easily fabricated to contain fluorophores, which make the dielectric nanofibre and multilayer configuration suitable for developing a large range of new nanometric scale devices, such as processor–memory interconnections, devices with sensitivity to target analytes, incident polarization and multi-colour BSW modes. PMID:28155871

Prebiotic Polymerization: Oxidative Polymerization of 2,3 Dimercapto-1- Propanol on the Surface of Iron(III) Hydroxide Oxide

NASA Technical Reports Server (NTRS)

Weber, Arthur L.

1995-01-01

The oxidation of 2,3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the FE(OH)O phase. Reactions carried out at the same ratio of dithiol to FE(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

Prebiotic polymerization: Oxidative polymerization of 2, 3-dimercapto-1-propanol on the surface of iron(III) hydroxide oxide

NASA Technical Reports Server (NTRS)

Weber, Arthur L.

1995-01-01

The oxidation of 2, 3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the Fe(OH)O phase. Reactions carried out at the same ratio of dithiol to Fe(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

In vitro biocompatibility of plasma-aided surface-modified 316L stainless steel for intracoronary stents.

PubMed

Bayram, Cem; Mizrak, Alpay Koray; Aktürk, Selçuk; Kurşaklioğlu, Hurkan; Iyisoy, Atila; Ifran, Ahmet; Denkbaş, Emir Baki

2010-10-01

316L-type stainless steel is a raw material mostly used for manufacturing metallic coronary stents. The purpose of this study was to examine the chemical, wettability, cytotoxic and haemocompatibility properties of 316L stainless steel stents which were modified by plasma polymerization. Six different polymeric compounds, polyethylene glycol, 2-hydroxyethyl methacrylate, ethylenediamine, acrylic acid, hexamethyldisilane and hexamethyldisiloxane, were used in a radio frequency glow discharge plasma polymerization system. As a model antiproliferative drug, mitomycin-C was chosen for covalent coupling onto the stent surface. Modified SS 316L stents were characterized by water contact angle measurements (goniometer) and x-ray photoelectron spectroscopy. C1s binding energies showed a good correlation with the literature. Haemocompatibility tests of coated SS 316L stents showed significant latency (t-test, p < 0.05) with respect to SS 316L and control groups in each test.

Nanoengineered analytical immobilized metal affinity chromatography stationary phase by atom transfer radical polymerization: Separation of synthetic prion peptides

PubMed Central

McCarthy, P.; Chattopadhyay, M.; Millhauser, G.L.; Tsarevsky, N.V.; Bombalski, L.; Matyjaszewski, K.; Shimmin, D.; Avdalovic, N.; Pohl, C.

2010-01-01

Atom transfer radical polymerization (ATRP) was employed to create isolated, metal-containing nanoparticles on the surface of non-porous polymeric beads with the goal of developing a new immobilized metal affnity chromatography (IMAC) stationary phase for separating prion peptides and proteins. Transmission electron microscopy was used to visualize nanoparticles on the substrate surface. Individual ferritin molecules were also visualized as ferritin–nanoparticle complexes. The column's resolving power was tested by synthesizing peptide analogs to the copper binding region of prion protein and injecting mixtures of these analogs onto the column. As expected, the column was capable of separating prion-related peptides differing in number of octapeptide repeat units (PHGGGWGQ), (PHGGGWGQ)2, and (PHGGGWGQ)4. Unexpectedly, the column could also resolve peptides containing the same number of repeats but differing only in the presence of a hydrophilic tail, Q → A substitution, or amide nitrogen methylation. PMID:17481564

Template Synthesis of Nanostructured Polymeric Membranes by Inkjet Printing.

PubMed

Gao, Peng; Hunter, Aaron; Benavides, Sherwood; Summe, Mark J; Gao, Feng; Phillip, William A

2016-02-10

The fabrication of functional nanomaterials with complex structures has been serving great scientific and practical interests, but current fabrication and patterning methods are generally costly and laborious. Here, we introduce a versatile, reliable, and rapid method for fabricating nanostructured polymeric materials. The novel method is based on a combination of inkjet printing and template synthesis, and its utility and advantages in the fabrication of polymeric nanomaterials is demonstrated through three examples: the generation of polymeric nanotubes, nanowires, and thin films. Layer-by-layer-assembled nanotubes can be synthesized in a polycarbonate track-etched (PCTE) membrane by printing poly(allylamine hydrochloride) and poly(styrenesulfonate) sequentially. This sequential deposition of polyelectrolyte ink enables control over the surface charge within the nanotubes. By a simple change of the printing conditions, polymeric nanotubes or nanowires were prepared by printing poly(vinyl alcohol) in a PCTE template. In this case, the high-throughput nature of the method enables functional nanomaterials to be generated in under 3 min. Furthermore, we demonstrate that inkjet printing paired with template synthesis can be used to generate patterns comprised of chemically distinct nanomaterials. Thin polymeric films of layer-by-layer-assembled poly(allylamine hydrochloride) and poly(styrenesulfonate) are printed on a PCTE membrane. Track-etched membranes covered with the deposited thin films reject ions and can potentially be utilized as nanofiltration membranes. When the fabrication of these different classes of nanostructured materials is demonstrated, the advantages of pairing template synthesis with inkjet printing, which include fast and reliable deposition, judicious use of the deposited materials, and the ability to design chemically patterned surfaces, are highlighted.

Surface morphology of refractive-index waveguide gratings fabricated in polymer films

NASA Astrophysics Data System (ADS)

Dong, Yi; Song, Yan-fang; Ma, Lei; Gao, Fang-fang

2016-09-01

The characteristic modifications are reported on the surface of polymeric waveguide film in the process of volume- grating fabrication. The light from a mode-locked 76 MHz femtosecond laser with pulse duration of 200 fs and wavelength of 800 nm is focused normal to the surface of the sample. The surface morphology modifications are ascribed to a fact that surface swelling occurs during the process. Periodic micro-structure is inscribed with increasing incident power. The laser-induced swelling threshold on the grating, which is higher than that of two-photon initiated photo-polymerization (TPIP) (8 mW), is verified to be about 20 mW. It is feasible to enhance the surface smoothness of integrated optics devices for further encapsulation. The variation of modulation depth is studied for different values of incident power and scan spacing. Ablation accompanied with surface swelling appears when the power is higher. By optimizing the laser carving parameters, highly efficient grating devices can be fabricated.

Novel "anchor modification" of polymeric biomaterial surfaces by the utilization of cyclodextrin inclusion complex supramolecules.

PubMed

Zhao, Xiaobin; Courtney, James M

2009-07-01

In this article, a novel approach for the surface modification of polymeric biomaterials by the utilization of supramolecules was studied. The supramolecules selected were cyclodextrin inclusion complexes (CICs). The biomaterial selected for surface modification was plasticized poly (vinyl chloride) (PVC-P). Results indicate that when the CICs were blended into PVC-P, they tend to migrate and "anchor" on the surface to achieve a remarkable protein-resistant surface, with improved blood compatibility. In comparison with a physical mixture of cyclodextrins and a "guest" molecule, such as poly(ethylene oxide) (PEO)-poly(propylene oxide) (PPO)-PEO and PPO-PEO-PPO for PVC-P modification, CICs modified PVC-P are more consistent in processing and achieve reproducible surface characteristics. Based on this study, a novel "anchor modification" was proposed regarding CICs modified surface. This "anchor modification" is likely to reduce plasticizer extraction from PVC-P and also can be utilized for the modification of polymers other than PVC-P.

Caractérisation de l'état de surface et des contraintes résiduelles engendrées par meulage

NASA Astrophysics Data System (ADS)

Gognau, D.; Blehaut, H.; Dürr, J.; Hariri, S.; Khouchaf, L.; Flahaut, P.

2002-07-01

grinding operations are generally used to prepare surfaces or improve surface state before or after welding. These operations, when carried out manually with portable machines, induce superficial work hardening, modification of the structure of material and residual stresses. An experimental study about the influence of grinding has been carried out on two metallic materials, a low carbon steel (A42-CP) and an austenitic stainless steel (316L), in order to characterise the grinding effects. Manual grinding being difficult to control (no repeatable effects), a test rig using a portable machine has been made. This test rig enables to control the grinding parameters in order to obtain repeatable grinding operations. Characterisation of the ground surfaces was made by 2D profilometry and measurements of residual stresses have been carried out with a Set-X Elphyse apparatus. The profiles of residual stresses obtained show, on the one hand, that on each material, identical grindings generate identical states of stresses and on the other hand, that materials have not the same behaviour, From a metallurgical point of view, we also observe that the grinding effects are different for both materials. The grinding of the A42 steel highlights a crushing of the grain near the surface while the 316L stainless steel grinding reveals sliding bands. Des opérations de meulage sont régulièrement effectuées sur des matériaux métalliques pour préparer les surfaces ou pour améliorer l'état de ces surfaces après soudage. Ces opérations réalisées manuellement engendrent un écrouissage superficiel, une modification de la structure du matériau et par conséquent des contraintes résiduelles. Une étude expérimentale a été menée sur un acier à bas carbone (A42-CP) et un acier inoxydable austénitique (316L) afin de caractériser les effets du meulage. Le meulage manuel étant difficile à maîtriser (effets non reproductibles), un banc d'essai utilisant une machine portative a été réalisé afin de contrôler les différents paramètres caractéristiques des opérations de meulage. Ensuite, la détermination de la rugosité des surfaces meulées s'est faite par profilornétrie 2D et les contraintes résiduelles ont été mesurées sur un appareil Set-X Elphyse. Les profils de contraintes obtenus montrent d'une part que sur un même matériau, des meulages réalisés dans les mêmes conditions aboutissent à des résultats semblables et d'autre part, que les deux matériaux utilises se comportent différemment. Ainsi, d'un point de vue métallurgique, on observe que le meulage de l'acier A42 favorise un écrasement des grains proches de la surface alors que le meulage de l'acier inoxydable 316L fait apparaître de nombreuses bandes de glissement.

Purification of boron nitride nanotubes via polymer wrapping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Jin-Hyuk; Kim, Jaewoo; WCI Quantum Beam based Radiation Research Center, Korea Atomic Energy Research Institute, 1045 Daedukdaero, Daejeon 305-353

2013-03-15

Highlights: ► Surface modification of boron nitride nanotubes using polymeric materials. ► Surface-modified BNNT was purified with a simple dilution-centrifugation step. ► Surface-modified BNNT can be directly used for polymer composite fabrication ► Degree of purification was analyzed by Raman spectroscopy. - Abstract: Boron nitride nanotubes (BNNT) synthesized by a ball milling-annealing were surface-modified using three different types of polymeric materials. Those materials were chosen depending on future applications especially in polymer nanocomposite fabrications. We found that the surface-modified BNNT can be purified with a simple dilution-centrifugation step, which would be suitable for large-scale purification. Degree of purification was monitoredmore » by means of the center peak position and FWHM of E{sub 2g} mode of BNNT in Raman spectra. As the purification of BNNT develops, the peak position was up-shifted while FWHM of the peak was narrowed.« less

Three-dimensional plotter technology for fabricating polymeric scaffolds with micro-grooved surfaces.

PubMed

Son, JoonGon; Kim, GeunHyung

2009-01-01

Various mechanical techniques have been used to fabricate biomedical scaffolds, including rapid prototyping (RP) devices that operate from CAD files of the target feature information. The three-dimensional (3-D) bio-plotter is one RP system that can produce design-based scaffolds with good mechanical properties for mimicking cartilage and bones. However, the scaffolds fabricated by RP have very smooth surfaces, which tend to discourage initial cell attachment. Initial cell attachment, migration, differentiation and proliferation are strongly dependent on the chemical and physical characteristics of the scaffold surface. In this study, we propose a new 3-D plotting method supplemented with a piezoelectric system for fabricating surface-modified scaffolds. The effects of the physically-modified surface on the mechanical and hydrophilic properties were investigated, and the results of cell culturing of chondrocytes indicate that this technique is a feasible new method for fabricating high-quality 3-D polymeric scaffolds.

Surface properties of poly(acrylonitrile) (PAN) precipitation polymerized in supercritical CO2 and the influence of the molecular weight.

PubMed

Shen, Qing; Gu, Qing-Feng; Hu, Jian-Feng; Teng, Xin-Rong; Zhu, Yun-Feng

2003-11-15

In this paper, the surface properties, e.g., the total surface free energy and the related Lifshitz-van der Waals and Lewis acid-base components, of polyacrylonitrile (PAN) precipitation polymerized in supercritical CO(2) have been characterized. Moreover, the influence of molecular weight varying has been also investigated. Results show that the surface properties of PAN resulting from supercritical CO(2) are different from those obtained by the conventional method. Of these data, one important finding is that the supercritical CO(2) PAN seems to decrease the surface free energy with the increased molecular weight. Based on previous recorded NMR spectra of this PAN and especially compared to commercial PAN, such phenomena are discussed and ascribed to an increase of the H-bonds and a reduction of the isotacticity in the supercritical CO(2) condition for PAN.

Unprecedented covalently attached ATRP initiator onto OH-functionalized mica surfaces.

PubMed

Lego, Béatrice; Skene, W G; Giasson, Suzanne

2008-01-15

Mica substrates were activated by a plasma method leading to OH-functionalized surfaces to which an atom transfer radical polymerization (ATRP) radical initiator was covalently bound using standard siloxane protocols. The unprecedented covalently immobilized initiator underwent radical polymerization with tert-butyl acrylate, yielding for the first time end-grafted polymer brushes that are covalently linked to mica. The initiator grafting on the mica substrate was confirmed by time-of-flight secondary ion mass spectrometry (TOF-SIMS), while the change in the water contact angle of the OH-activated mica surface was used to follow the change in surface coverage of the initiator on the surface. The polymer brush and initiator film thicknesses relative to the virgin mica were confirmed by atomic force microscopy (AFM). This was done by comparing the atomic step-height difference between a protected area of freshly cleaved mica and a zone exposed to plasma activation, initiator immobilization, and then ATRP.

Kir6.2 activation by sulfonylurea receptors: a different mechanism of action for SUR1 and SUR2A subunits via the same residues

PubMed Central

Principalli, Maria A; Dupuis, Julien P; Moreau, Christophe J; Vivaudou, Michel; Revilloud, Jean

2015-01-01

ATP-sensitive potassium channels (K-ATP channels) play a key role in adjusting the membrane potential to the metabolic state of cells. They result from the unique combination of two proteins: the sulfonylurea receptor (SUR), an ATP-binding cassette (ABC) protein, and the inward rectifier K+ channel Kir6.2. Both subunits associate to form a heterooctamer (4 SUR/4 Kir6.2). SUR modulates channel gating in response to the binding of nucleotides or drugs and Kir6.2 conducts potassium ions. The activity of K-ATP channels varies with their localization. In pancreatic β-cells, SUR1/Kir6.2 channels are partly active at rest while in cardiomyocytes SUR2A/Kir6.2 channels are mostly closed. This divergence of function could be related to differences in the interaction of SUR1 and SUR2A with Kir6.2. Three residues (E1305, I1310, L1313) located in the linker region between transmembrane domain 2 and nucleotide-binding domain 2 of SUR2A were previously found to be involved in the activation pathway linking binding of openers onto SUR2A and channel opening. To determine the role of the equivalent residues in the SUR1 isoform, we designed chimeras between SUR1 and the ABC transporter multidrug resistance-associated protein 1 (MRP1), and used patch clamp recordings on Xenopus oocytes to assess the functionality of SUR1/MRP1 chimeric K-ATP channels. Our results reveal that the same residues in SUR1 and SUR2A are involved in the functional association with Kir6.2, but they display unexpected side-chain specificities which could account for the contrasted properties of pancreatic and cardiac K-ATP channels. PMID:26416970

Estimation of degree of polymerization of poly-acrylonitrile-grafted carbon nanotubes using Guinier plot of small angle x-ray scattering

NASA Astrophysics Data System (ADS)

Cho, Hyunjung; Jin, Kyeong Sik; Lee, Jaegeun; Lee, Kun-Hong

2018-07-01

Small angle x-ray scattering (SAXS) was used to estimate the degree of polymerization of polymer-grafted carbon nanotubes (CNTs) synthesized using a ‘grafting from’ method. This analysis characterizes the grafted polymer chains without cleaving them from CNTs, and provides reliable data that can complement conventional methods such as thermogravimetric analysis or transmittance electron microscopy. Acrylonitrile was polymerized from the surface of the CNTs by using redox initiation to produce poly-acrylonitrile-grafted CNTs (PAN-CNTs). Polymerization time and the initiation rate were varied to control the degree of polymerization. Radius of gyration (R g ) of PAN-CNTs was determined using the Guinier plot obtained from SAXS solution analysis. The results showed consistent values according to the polymerization condition, up to a maximum R g = 125.70 Å whereas that of pristine CNTs was 99.23 Å. The dispersibility of PAN-CNTs in N,N-dimethylformamide was tested using ultraviolet–visible-near infrared spectroscopy and was confirmed to increase as the degree of polymerization increased. This analysis will be helpful to estimate the degree of polymerization of any polymer-grafted CNTs synthesized using the ‘grafting from’ method and to fabricate polymer/CNT composite materials.

Estimation of degree of polymerization of poly-acrylonitrile-grafted carbon nanotubes using Guinier plot of small angle x-ray scattering.

PubMed

Cho, Hyunjung; Jin, Kyeong Sik; Lee, Jaegeun; Lee, Kun-Hong

2018-07-06

Small angle x-ray scattering (SAXS) was used to estimate the degree of polymerization of polymer-grafted carbon nanotubes (CNTs) synthesized using a 'grafting from' method. This analysis characterizes the grafted polymer chains without cleaving them from CNTs, and provides reliable data that can complement conventional methods such as thermogravimetric analysis or transmittance electron microscopy. Acrylonitrile was polymerized from the surface of the CNTs by using redox initiation to produce poly-acrylonitrile-grafted CNTs (PAN-CNTs). Polymerization time and the initiation rate were varied to control the degree of polymerization. Radius of gyration (R g ) of PAN-CNTs was determined using the Guinier plot obtained from SAXS solution analysis. The results showed consistent values according to the polymerization condition, up to a maximum R g  = 125.70 Å whereas that of pristine CNTs was 99.23 Å. The dispersibility of PAN-CNTs in N,N-dimethylformamide was tested using ultraviolet-visible-near infrared spectroscopy and was confirmed to increase as the degree of polymerization increased. This analysis will be helpful to estimate the degree of polymerization of any polymer-grafted CNTs synthesized using the 'grafting from' method and to fabricate polymer/CNT composite materials.

Carbamazepine as a novel small molecule corrector of trafficking-impaired ATP-sensitive potassium channels identified in congenital hyperinsulinism.

PubMed

Chen, Pei-Chun; Olson, Erik M; Zhou, Qing; Kryukova, Yelena; Sampson, Heidi M; Thomas, David Y; Shyng, Show-Ling

2013-07-19

ATP-sensitive potassium (KATP) channels consisting of sulfonylurea receptor 1 (SUR1) and the potassium channel Kir6.2 play a key role in insulin secretion by coupling metabolic signals to β-cell membrane potential. Mutations in SUR1 and Kir6.2 that impair channel trafficking to the cell surface lead to loss of channel function and congenital hyperinsulinism. We report that carbamazepine, an anticonvulsant, corrects the trafficking defects of mutant KATP channels previously identified in congenital hyperinsulinism. Strikingly, of the 19 SUR1 mutations examined, only those located in the first transmembrane domain of SUR1 responded to the drug. We show that unlike that reported for several other protein misfolding diseases, carbamazepine did not correct KATP channel trafficking defects by activating autophagy; rather, it directly improved the biogenesis efficiency of mutant channels along the secretory pathway. In addition to its effect on channel trafficking, carbamazepine also inhibited KATP channel activity. Upon subsequent removal of carbamazepine, however, the function of rescued channels was recovered. Importantly, combination of the KATP channel opener diazoxide and carbamazepine led to enhanced mutant channel function without carbamazepine washout. The corrector effect of carbamazepine on mutant KATP channels was also demonstrated in rat and human β-cells with an accompanying increase in channel activity. Our findings identify carbamazepine as a novel small molecule corrector that may be used to restore KATP channel expression and function in a subset of congenital hyperinsulinism patients.

Plates-formes de microscopie et fluorescence par resonance de plasmons de surface appliquees a l'imagerie cellulaire

NASA Astrophysics Data System (ADS)

Chabot, Vincent

L'elaboration de nouveaux medicaments repose sur les etudes pharmacologiques, dont le role est d'identifier de nouveaux composes actifs ou de nouvelles cibles pharmacologiques agissant entre autres au niveau cellulaire. Recemment, la detection basee sur la resonance des plasmons de surface (SPR) a ete appliquee a l'etude de reponses cellulaires. Cette methode de detection, permettant d'observer des variations d'indice de refraction associes a de faibles changements de masse a la surface d'un metal, a l'avantage de permettre l'etude d'une population de cellules vivantes en temps reel, sans necessiter l'introduction d'agents de marquage. Pour effectuer la detection au niveau de cellules individuelles, on peut employer la microscopie SPR, qui consiste a localiser spatialement la detection par un systeme d'imagerie. Cependant, la detection basee sur la SPR est une mesure sans marquage et les signaux mesures sont attribues a une reponse moyennee des differentes sources cellulaires. Afin de mieux comprendre et identifier les composantes cellulaires generant le signal mesure en SPR, il est pertinent de combiner la microscopie SPR avec une modalite complementaire, soit l'imagerie de fluorescence. C'est dans cette problematique que s'insere ce projet de these, consistant a concevoir deux plates-formes distinctes de microscopie SPR et de fluorescence optimisees pour l'etude cellulaire, de sorte a evaluer les possibilites d'integration de ces deux modalites en un seul systeme. Des substrats adaptes pour chaque plate-forme ont ete concus et realises. Ces substrats employaient une couche d'argent passivee par l'ajout d'une mince couche d'or. La stabilite et la biocompatibilite des substrats ont ete validees pour l'etude cellulaire. Deux configurations permettant d'ameliorer la sensibilite en sondant les cellules plus profondement ont ete evaluees, soit l'emploi de plasmons de surface a longue portee et de guides d'onde a gaine metallique. La sensibilite accrue de ces configurations a aussi ete demontree pour un usage en biodetection cellulaire. Une plate-forme permettant de mesurer la spectroscopie SPR simultanement avec l'acquisition d'images de fluorescence a ete realisee. Cette plate-forme a ensuite ete validee par l'etude de reponses cellulaires suite a une stimulation pharmacologique. Puis, un systeme base sur la microscopie SPR a ete concu et caracterise. Son emploi pour l'etude de reponses au niveau de cellules individuelles a ete demontre. Finalement, les forces et faiblesses des substrats et des plates-formes realisees au cours de la these ont ete evaluees. Des possibilites d'amelioration sont mises de l'avant et l'integration des modalites de microscopie SPR et de fluorescence suite aux travaux de la these est discutee. Les realisations au cours de cette etude ont donc permis d'identifier les composantes cellulaires impliquees dans la generation du signal mesure en biodetection SPR. Mots-cles : Resonance des plasmons de surface, microscopie SPR, plasmons de surface a longue portee LRSPR, guide d'onde a gaine metallique MCWG, fluorescence exaltee par plasmons de surface SPEF, biodetection cellulaire, imagerie SPR.

Selective protection of poly(tetra-fluoroethylene) from effects of chemical etching

DOEpatents

Martinez, Robert J.; Rye, Robert R.

1991-01-01

A photolithographic method for treating an article formed of polymeric material comprises subjecting portions of a surface of the polymeric article to ionizing radiation; and then subjecting the surface to chemical etching. The ionizing radiation treatment according to the present invention minimizes the effect of the subseuent chemical etching treatment. Thus, selective protection from the effects of chemical etching can be easily provided. The present invention has particular applicability to articles formed of fluorocarbons, such as PTFE. The ionizing radiation employed in the method may comprise Mg(k.alpha.) X-rays or lower-energy electrons.

Surface-initiated polymerization within mesoporous silica spheres for the modular design of charge-neutral polymer particles.

PubMed

Müllner, Markus; Cui, Jiwei; Noi, Ka Fung; Gunawan, Sylvia T; Caruso, Frank

2014-06-03

We report a templating approach for the preparation of functional polymer replica particles via surface-initiated polymerization in mesoporous silica templates. Subsequent removal of the template resulted in discrete polymer particles. Furthermore, redox-responsive replica particles could be engineered to disassemble in a reducing environment. Particles, made of poly(methacryloyloxyethyl phosphorylcholine) (PMPC) or poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA), exhibited very low association to human cancer cells (below 5%), which renders the reported charge-neutral polymer particles a modular and versatile class of highly functional carriers with potential applications in drug delivery.

In situ thermal polymerisation of natural oils as novel sustainable approach in nanographite particle production

NASA Astrophysics Data System (ADS)

Datsyuk, Vitaliy; Trotsenko, Svitlana; Reich, Stephanie

2018-01-01

A sustainable approach to graphite exfoliation via in situ thermal polymerization of fish oil results in the production of nanographite particles. The material was characterized by elemental analysis, transmission electron microscopy, and Raman spectroscopy. The thermal polymerization of fish oil was controlled by monitoring the viscosity and measuring the iodine number. The number of structural defects on the graphitic surface remained constant during the synthesis. The protocol leads to a hydrophobization of the nanographite surface. Immobilized polyoil islands create sterical hindrance and stabilize the nanographite particles in engineering polymers.

Occurrence and Speciation of Polymeric Chromium(III), Monomeric Chromium(III) and Chromium(VI) in Environmental Samples

PubMed Central

HU, LIGANG; CAI, YONG; JIANG, GUIBIN

2016-01-01

Laboratory experiments suggest that polymeric Cr(III) could exist in aqueous solution for a relative long period of time. However, the occurrence of polymeric Cr(III) has not been reported in environmental media due partially to the lack of method for speciating polymeric Cr. We observed an unknown Cr species during the course of study on speciation of Cr in the leachates of chromated-copper-arsenate (CCA)-treated wood. Efforts were made to identify structure of the unknown Cr species. Considering the forms of Cr existed in the CCA-treated woods, we mainly focused our efforts to determine if the unknown species were polymeric Cr(III), complex of Cr/As or complex of Cr with dissolved organic matter (DOM). In order to evaluate whether polymeric Cr(III) largely exist in wood leachates, high performance liquid chromatography coupled with inductively coupled mass spectrometry (HPLC-ICPMS was used) for simultaneous speciation of monomeric Cr(III), polymeric Cr(III), and Cr(VI). In addition to wood leachates where polymeric Cr (III) ranged from 39.1 to 67.4 %, occurrence of the unknown Cr species in other environmental matrices, including surface waters, tap and waste waters, was also investigated. It was found that polymeric Cr(III) could exist in environmental samples containing μg/L level of Cr, at a level up to 60% of total Cr, suggesting that polymeric Cr(III) could significantly exist in natural environments. Failure in quantifying polymeric Cr(III) would lead to the underestimation of total Cr and bias in Cr speciation. The environmental implication of the presence of polymeric Cr(III) species in the environment deserves further study. PMID:27156211

Ullmann-type coupling of brominated tetrathienoanthracene on copper and silver

NASA Astrophysics Data System (ADS)

Gutzler, Rico; Cardenas, Luis; Lipton-Duffin, Josh; El Garah, Mohamed; Dinca, Laurentiu E.; Szakacs, Csaba E.; Fu, Chaoying; Gallagher, Mark; Vondráček, Martin; Rybachuk, Maksym; Perepichka, Dmitrii F.; Rosei, Federico

2014-02-01

We report the synthesis of extended two-dimensional organic networks on Cu(111), Ag(111), Cu(110), and Ag(110) from thiophene-based molecules. A combination of scanning tunnelling microscopy and X-ray photoemission spectroscopy yields insight into the reaction pathways from single molecules towards the formation of two-dimensional organometallic and polymeric structures via Ullmann reaction dehalogenation and C-C coupling. The thermal stability of the molecular networks is probed by annealing at elevated temperatures of up to 500 °C. On Cu(111) only organometallic structures are formed, while on Ag(111) both organometallic and covalent polymeric networks were found to coexist. The ratio between organometallic and covalent bonds could be controlled by means of the annealing temperature. The thiophene moieties start degrading at 200 °C on the copper surface, whereas on silver the degradation process becomes significant only at 400 °C. Our work reveals how the interplay of a specific surface type and temperature steers the formation of organometallic and polymeric networks and describes how these factors influence the structural integrity of two-dimensional organic networks.We report the synthesis of extended two-dimensional organic networks on Cu(111), Ag(111), Cu(110), and Ag(110) from thiophene-based molecules. A combination of scanning tunnelling microscopy and X-ray photoemission spectroscopy yields insight into the reaction pathways from single molecules towards the formation of two-dimensional organometallic and polymeric structures via Ullmann reaction dehalogenation and C-C coupling. The thermal stability of the molecular networks is probed by annealing at elevated temperatures of up to 500 °C. On Cu(111) only organometallic structures are formed, while on Ag(111) both organometallic and covalent polymeric networks were found to coexist. The ratio between organometallic and covalent bonds could be controlled by means of the annealing temperature. The thiophene moieties start degrading at 200 °C on the copper surface, whereas on silver the degradation process becomes significant only at 400 °C. Our work reveals how the interplay of a specific surface type and temperature steers the formation of organometallic and polymeric networks and describes how these factors influence the structural integrity of two-dimensional organic networks. Electronic supplementary information (ESI) available: Additional STM data and DFT results. See DOI: 10.1039/c3nr05710k

Surface functionalization of copper via oxidative graft polymerization of 2,2'-bithiophene and immobilization of silver nanoparticles for combating biocorrosion.

PubMed

Wan, Dong; Yuan, Shaojun; Neoh, K G; Kang, E T

2010-06-01

An environmentally benign approach to surface modification was developed to impart copper surface with enhanced resistance to corrosion, bacterial adhesion and biocorrosion. Oxidative graft polymerization of 2,2'-bithiophene from the copper surface with self-assembled 2,2'-bithiophene monolayer, and subsequent reduction of silver ions to silver nanoparticles (Ag NPs) on the surface, give rise to a homogeneous bithiophene polymer (PBT) film with densely coupled Ag NPs on the copper surface (Cu-g-PBT-Ag NP surface). The immobilized Ag NPs were found to significantly inhibit bacterial adhesion and enhance the antibacterial properties of the PBT modified copper surface. The corrosion inhibition performance of the functionalized copper substrates was evaluated by Tafel polarization curves and electrochemical impedance spectroscopy. Arising from the chemical affinity of thiols for the noble and coinage metals, the copper surface functionalized with both PBT brushes and Ag NPs also exhibits long-term stability, and is thus potentially useful for combating the combined problems of corrosion and biocorrosion in harsh marine and aquatic environments.

Multilayer Choline Phosphate Molecule Modified Surface with Enhanced Cell Adhesion but Resistance to Protein Adsorption.

PubMed

Chen, Xingyu; Yang, Ming; Liu, Botao; Li, Zhiqiang; Tan, Hong; Li, Jianshu

2017-08-22

Choline phosphate (CP), which is a new zwitterionic molecule, and has the reverse order of phosphate choline (PC) and could bind to the cell membrane though the unique CP-PC interaction. Here we modified a glass surface with multilayer CP molecules using surface-initiated atom-transfer radical polymerization (SI-ATRP) and the ring-opening method. Polymeric brushes of (dimethylamino)ethyl methacrylate (DMAEMA) were synthesized by SI-ATRP from the glass surface. Then the grafted PDMAEMA brushes were used to introduce CP groups to fabricate the multilayer CP molecule modified surface. The protein adsorption experiment and cell culture test were used to evaluate the biocompatibility of the modified surfaces by using human umbilical veinendothelial cells (HUVECs). The protein adsorption results demonstrated that the multilayer CP molecule decorated surface could prevent the adsorption of fibrinogen and serum protein. The adhesion and proliferation of cells were improved significantly on the multilayer CP molecule modified surface. Therefore, the biocompatibility of the material surface could be improved by the modified multilayer CP molecule, which exhibits great potential for biomedical applications, e.g., scaffolds in tissue engineering.

Measurement of conformability and adhesion energy of polymeric ultrathin film to skin model

NASA Astrophysics Data System (ADS)

Sugano, Junki; Fujie, Toshinori; Iwata, Hiroyasu; Iwase, Eiji

2018-06-01

We measured the conformability and adhesion energy of a polymeric ultrathin film “nanosheet” with hundreds of nanometer thickness to a skin model with epidermal depressions. To compare the confirmability of the nanosheets with different thicknesses and/or under different attaching conditions, we proposed a measurement method using skin models with the same surface profile and defined the surface strain εS as the quantified value of the conformability. Then, we measured the adhesion energy of the nanosheet at each conformability through a vertical tensile test. Experimental results indicate that the adhesion energy does not depend on the liquid used in wetting the nanosheet before attaching to the skin model and increases monotonously as the surface strain εS increases.

Nanopatterned submicron pores as a shield for nonspecific binding in surface plasmon resonance-based sensing.

PubMed

Raz, Sabina Rebe; Marchesini, Gerardo R; Bremer, Maria G E G; Colpo, Pascal; Garcia, Cesar Pascual; Guidetti, Guido; Norde, Willem; Rossi, Francois

2012-11-21

We present a novel approach to tackle the most common drawback of using surface plasmon resonance for analyte screening in complex biological matrices--the nonspecific binding to the sensor chip surface. By using a perforated membrane supported by a polymeric gel structure at the evanescent wave penetration depth, we have fabricated a non-fouling sieve above the sensing region. The sieve shields the evanescent wave from nonspecific interactions which interfere with SPR sensing by minimizing the fouled area of the polymeric gel and preventing the translocation of large particles, e.g. micelles or aggregates. The nanopatterned macropores were fabricated by means of colloidal lithography and plasma enhanced chemical vapor deposition of a polyethylene oxide-like film on top of a polymeric gel matrix commonly used in surface plasmon resonance analysis. The sieve was characterized using surface plasmon resonance imaging, contact angle, atomic force microscopy and scanning electron microscopy. The performance of the sieve was studied using an immunoassay for detection of antibiotic residues in full fat milk and porcine serum. The non-fouling membrane presented pores in the 92-138 nm range organized in a hexagonal crystal lattice with a clearance of about 5% of the total surface. Functionally, the membrane with the nanopatterned macropores showed significant improvements in immunoassay robustness and sensitivity in untreated complex samples. The utilization of the sensor built-in sieve for measurements in complex matrices offers reduction in pre-analytical sample preparation steps and thus shortens the total analysis time.

Interpenetrating polymer network ion exchange membranes and method for preparing same

DOEpatents

Alexandratos, Spiro D.; Danesi, Pier R.; Horwitz, E. Philip

1989-01-01

Interpenetrating polymer network ion exchange membranes include a microporous polymeric support film interpenetrated by an ion exchange polymer and are produced by absorbing and polymerizing monomers within the support film. The ion exchange polymer provides ion exchange ligands at the surface of and throughout the support film which have sufficient ligand mobility to extract and transport ions across the membrane.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Yong; Desseaux, Solenne; Aden, Bethany

We report that surface-grafting thermoresponsive polymers allows the preparation of thin polymer brush coatings with surface properties that can be manipulated by variation of temperature. In most instances, thermoresponsive polymer brushes are produced using polymers that dehydrate and collapse above a certain temperature. This report presents the preparation and properties of polymer brushes that show thermoresponsive surface properties, yet are shape-persistent in that they do not undergo main chain collapse. The polymer brushes presented here are obtained via vapor deposition surface-initiated ring-opening polymerization (SI-ROP) of γ-di- or tri(ethylene glycol)-modified glutamic acid N-carboxyanhydrides. Vapor deposition SI-ROP of γ-di- or tri(ethylene glycol)-modifiedmore » L- or D-glutamic acid N-carboxyanhydrides affords helical surface-tethered polymer chains that do not show any changes in secondary structure between 10 and 70 °C. QCM-D experiments, however, revealed significant dehydration of poly(γ-(2-(2-methoxyethoxy)ethyl)-l-glutamate) (poly(L-EG 2-Glu)) brushes upon heating from 10 to 40 °C. At the same time, AFM and ellipsometry studies did not reveal significant variations in film thickness over this temperature range, which is consistent with the shape-persistent nature of these polypeptide brushes and indicates that the thermoresponsiveness of the films is primarily due to hydration and dehydration of the oligo(ethylene glycol) side chains. The results we present here illustrate the potential of surface-initiated NCA ring-opening polymerization to generate densely grafted assemblies of polymer chains that possess well-defined secondary structures and tunable surface properties. These polypeptide brushes complement their conformationally unordered counterparts that can be generated via surface-initiated polymerization of vinyl-type monomers and represent another step forward to biomimetic surfaces and interfaces.« less

Surface modification of blood-contacting biomaterials by plasma-polymerized superhydrophobic films using hexamethyldisiloxane and tetrafluoromethane as precursors

NASA Astrophysics Data System (ADS)

Hsiao, Chaio-Ru; Lin, Cheng-Wei; Chou, Chia-Man; Chung, Chi-Jen; He, Ju-Liang

2015-08-01

This paper proposes a plasma polymerization system that can be used to modify the surface of the widely used biomaterial, polyurethane (PU), by employing low-cost hexamethyldisiloxane (HMDSO) and tetrafluoromethane (CF4) as precursors; this system features a pulsed-dc power supply. Plasma-polymerized HMDSO/CF4 (pp-HC) with coexisting micro- and nanoscale morphology was obtained as a superhydrophobic coating material by controlling the HMDSO/CF4 (fH) monomer flow ratio. The developed surface modification technology can be applied to medical devices, because it is non-cytotoxic and has favorable hemocompatibility, and no blood clots form when the device surface direct contacts. Experimental results reveal that the obtained pp-HC films contained SiOx nanoparticles randomly dispersed on the micron-scale three-dimensional network film surface. The sbnd CF functional group, sbnd CF2 bonding, and SiOx were detected on the film surface. The maximal water contact angle of the pp-HC coating was 161.2°, apparently attributable to the synergistic effect of the coexisting micro- and nanoscale surface morphology featuring a low surface-energy layer. The superhydrophobic and antifouling characteristics of the coating were retained even after it was rubbed 20 times with a steel wool tester. Results of in vitro cytotoxicity, fibrinogen adsorption, and platelet adhesion tests revealed favorable myoblast cell proliferation and the virtual absence of fibrinogen adsorption and platelet adhesion on the pp-HC coated specimens. These quantitative findings imply that the pp-HC coating can potentially prevent the formation of thrombi and provide an alternative means of modifying the surfaces of blood-contacting biomaterials.

A novel approach to fabricate dye-encapsulated polymeric micro- and nanoparticles by thin film dewetting technique.

PubMed

Chatterjee, Manosree; Hens, Abhiram; Mahato, Kuldeep; Jaiswal, Namita; Mahato, Nivedita; Nagahanumaiah; Chanda, Nripen

2017-11-15

A new method is reported for fabrication of polymeric micro- and nanoparticles from an intermediate patterned surface originated by dewetting of a polymeric thin film. Poly (d, l-lactide-co-glycolide) or PLGA, a biocompatible polymer is used to develop a thin film over a clean glass substrate which dewets spontaneously in the micro-/nano-patterned surface of size range 50nm to 3.5µm. Since another water-soluble polymer, poly vinyl alcohol (PVA) is coated on the same glass substrate before PLGA thin film formation, developed micro-/nano-patterns are easily extracted in water in the form of micro- and nanoparticle mixture of size range 50nm to 3.0µm. This simplified method is also used to effectively encapsulate a dye molecule, rhodamine B inside the PLGA micro-/nanoparticles. The developed dye-encapsulated nanoparticles, PLGA-rhodamine are separated from the mixture and tested for in-vitro delivery application of external molecules inside human lung cancer cells. For the first time, the use of thin film dewetting technique is reported as a potential route for the synthesis of polymeric micro-/nanoparticles and effective encapsulation of external species therein. Copyright © 2017 Elsevier Inc. All rights reserved.

Transient inter-cellular polymeric linker.

PubMed

Ong, Siew-Min; He, Lijuan; Thuy Linh, Nguyen Thi; Tee, Yee-Han; Arooz, Talha; Tang, Guping; Tan, Choon-Hong; Yu, Hanry

2007-09-01

Three-dimensional (3D) tissue-engineered constructs with bio-mimicry cell-cell and cell-matrix interactions are useful in regenerative medicine. In cell-dense and matrix-poor tissues of the internal organs, cells support one another via cell-cell interactions, supplemented by small amount of the extra-cellular matrices (ECM) secreted by the cells. Here we connect HepG2 cells directly but transiently with inter-cellular polymeric linker to facilitate cell-cell interaction and aggregation. The linker consists of a non-toxic low molecular-weight polyethyleneimine (PEI) backbone conjugated with multiple hydrazide groups that can aggregate cells within 30 min by reacting with the aldehyde handles on the chemically modified cell-surface glycoproteins. The cells in the cellular aggregates proliferated; and maintained the cortical actin distribution of the 3D cell morphology while non-aggregated cells died over 7 days of suspension culture. The aggregates lost distinguishable cell-cell boundaries within 3 days; and the ECM fibers became visible around cells from day 3 onwards while the inter-cellular polymeric linker disappeared from the cell surfaces over time. The transient inter-cellular polymeric linker can be useful for forming 3D cellular and tissue constructs without bulk biomaterials or extensive network of engineered ECM for various applications.

Modulation of release kinetics by plasma polymerization of ampicillin-loaded β-TCP ceramics

NASA Astrophysics Data System (ADS)

Labay, C.; Buxadera-Palomero, J.; Avilés, M.; Canal, C.; Ginebra, M. P.

2016-08-01

Beta-tricalcium phosphate (β-TCP) bioceramics are employed in bone repair surgery. Their local implantation in bone defects puts them in the limelight as potential materials for local drug delivery. However, obtaining suitable release patterns fitting the required therapeutics is a challenge. Here, plasma polymerization of ampicillin-loaded β-TCP is studied for the design of a novel antibiotic delivery system. Polyethylene glycol-like (PEG-like) coating of β-TCP by low pressure plasma polymerization was performed using diglyme as precursor, and nanometric PEG-like layers were obtained by simple and double plasma polymerization processes. A significant increase in hydrophobicity, and the presence of plasma polymer was visible on the surface by SEM and quantified by XPS. As a main consequence of the plasma polymerisation, the release kinetics were successfully modified, avoiding burst release, and slowing down the initial rate of release leading to a 4.5 h delay in reaching the same antibiotic release percentage, whilst conservation of the activity of the antibiotic was simultaneously maintained. Thus, plasma polymerisation on the surface of bioceramics may be a good strategy to design controlled drug delivery matrices for local bone therapies.

Y2O3:Eu phosphor particles prepared by spray pyrolysis from a solution containing citric acid and polyethylene glycol

NASA Astrophysics Data System (ADS)

Roh, H. S.; Kang, Y. C.; Park, H. D.; Park, S. B.

Y2O3:Eu phosphor particles were prepared by large-scale spray pyrolysis. The morphological control of Y2O3:Eu particles in spray pyrolysis was attempted by adding polymeric precursors to the spray solution. The effect of composition and amount of polymeric precursors on the morphology, crystallinity and photoluminescence characteristics of Y2O3:Eu particles was investigated. Particles prepared from a solution containing polyethylene glycol (PEG) with an average molecular weight of 200 had a hollow structure, while those prepared from solutions containing adequate amounts of citric acid (CA) and PEG had a spherical shape, filled morphology and clean surfaces after post-treatment at high temperature. Y2O3:Eu particles prepared from an aqueous solution with no polymeric precursors had a hollow structure and rough surfaces after post-treatment. The phosphor particles prepared from solutions with inadequate amounts of CA and/or PEG also had hollow and/or fragmented structures. The particles prepared from the solution containing 0.3 M CA and 0.3 M PEG had the highest photoluminescence emission intensity, which was 56% higher than that of the particles prepared from aqueous solution without polymeric precursors.

Nanocapsule of cationic liposomes obtained using "in situ" acrylic acid polymerization: stability, surface charge and biocompatibility.

PubMed

Scarioti, Giovana Danieli; Lubambo, Adriana; Feitosa, Judith P A; Sierakowski, Maria Rita; Bresolin, Tania M B; de Freitas, Rilton Alves

2011-10-15

In this work, didecyldimethylammonium bromide (DDAB) and 1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine (DOPE) (2.5:1) were used to prepare liposomes coated with polyacrylic acid (PAA) using "in situ" polymerization with 2.5, 5 and 25 mM of acrylic acid (AA). The PAA concentrations were chosen to achieve partially to fully covered capsules, and the polymerization reaction was observed with real-time monitoring using dynamic light scattering (NanoDLS). The DDAB:DOPE liposomes showed stability in the tested temperature range (25-70°C), whereas the results confirmed the success of the polymerization according to superficial charge (zeta potential of +66.7±1.2 mV) results and AFM images. For the liposomes that were fully coated with PAA (zeta potential of +0.3±3.9 mV), cytotoxicity was independent of the concentration of albumin. Cationic liposomes and nanocapsules of the stable liposomes coated with PAA were obtained by controlling the surface charge, which was the most important factor related to cytotoxicity. Thus, a potential, safe drug nanocarrier was successfully developed in this work. Copyright © 2011 Elsevier B.V. All rights reserved.

Detection Of Uric Acid Based On Multi-Walled Carbon Nanotubes Polymerized With A Layer Of Molecularly Imprinted PMAA

NASA Astrophysics Data System (ADS)

Chen, Po-Yen; Lin, Chia-Yu; Ho, Kuo-Chuan

2009-05-01

A molecularly imprinted poly-metharylic acid (PMAA), polymerizing on the surface of multi-walled carbon nanotube (MWCNT), was synthesized. The MWCNT was modified by a layer of carboxylic acid and reacted with EDC and NHS to activate the carboxylic acid, which was prepared for the purpose of bonding allyl amine and getting an unsaturated side chain (-C=C). The resultant structure is abbreviated as MWCNTs-CH=CH2. It is well known that the vinyl group side chain provides good attachment between the MWCNTs and the molecularly imprinted polymer (MIP). The MIP based on PMAA was polymerized on the surface of MWCNTs-CH=CH2 with the addition of uric acid (UA). The non-imprinted polymer (NIP) was polymerized without adding UA. The adsorbed amount of UA approached the equilibrium value upon 60 min adsorption. The adsorption isotherm was obtained by immersing 10 mg of MIP or NIP in 5 mL aqueous solution containing different concentrations of UA. The adsorbed amounts were measured via a UV-Vis spectrometer at a wavelength of 292 nm. From the adsorption isotherm, it is seen that the MIP particles possess a good imprinting efficiency of about 4.41.

Semipermeable thin-film membranes comprising siloxane, alkoxysilyl and aryloxysilyl oligomers and copolymers

DOEpatents

Babcock, W.C.; Friesen, D.T.

1988-11-01

Novel semipermeable membranes and thin film composite (TFC) gas separation membranes useful in the separation of oxygen, nitrogen, hydrogen, water vapor, methane, carbon dioxide, hydrogen sulfide, lower hydrocarbons, and other gases are disclosed. The novel semipermeable membranes comprise the polycondensation reaction product of two complementary polyfunctional compounds, each having at least two functional groups that are mutually reactive in a condensation polymerization reaction, and at least one of which is selected from siloxanes, alkoxsilyls and aryloxysilyls. The TFC membrane comprises a microporous polymeric support, the surface of which has the novel semipermeable film formed thereon, preferably by interfacial polymerization.

Semipermeable thin-film membranes comprising siloxane, alkoxysilyl and aryloxysilyl oligomers and copolymers

DOEpatents

Babcock, Walter C.; Friesen, Dwayne T.

1988-01-01

Novel semiperimeable membranes and thin film composite (TFC) gas separation membranes useful in the separation of oxygen, nitrogen, hydrogen, water vapor, methane, carbon dioxide, hydrogen sulfide, lower hydrocarbons, and other gases are disclosed. The novel semipermeable membranes comprise the polycondensation reaction product of two complementary polyfunctional compounds, each having at least two functional groups that are mutually reactive in a condensation polymerization reaction, and at least one of which is selected from siloxanes, alkoxsilyls and aryloxysilyls. The TFC membrane comprises a microporous polymeric support, the surface of which has the novel semipermeable film formed thereon, preferably by interfacial polymerization.

Facile Synthesis of Thick Films of Poly(methyl methacrylate), Poly(styrene), and Poly(vinyl pyridine) from Au Surfaces

PubMed Central

Saha, Sampa

2011-01-01

Atom transfer radical polymerization (ATRP) is commonly used to grow polymer brushes from Au surfaces, but the resulting film thicknesses are usually significantly less than with ATRP from SiO2 substrates. On Au, growth of poly(methyl methacrylate) (PMMA) blocks from poly(tert-butyl acrylate) brushes occurs more rapidly than growth of PMMA from initiator monolayers, suggesting that the disparity between growth rates from Au and SiO2 stems from the Au surface. Radical quenching by electron transfer from Au is probably not the termination mechanism because polymerization from thin, cross-linked initiators gives film thicknesses that are essentially the same as the thicknesses of films grown from SiO2 under the same polymerization conditions. However, this result is consistent with termination through desorption of thiols from non-cross-linked films, and reaction of these thiols with growing polymer chains. The enhanced stability of cross-linked initiators allows ATRP at temperatures up to ~100 °C and enables the growth of thick films of PMMA (350 nm), polystyrene (120 nm) and poly(vinyl pyridine) (200 nm) from Au surfaces in 1 hour. At temperatures >100 °C, the polymer brush layers delaminate as large area films. PMID:21728374

Intriguing Morphology Evolution from Noncrosslinked Poly(tert-butyl acrylate) Seeds with Polar Functional Groups in Soap-Free Emulsion Polymerization of Styrene.

PubMed

Wang, Lu; Pan, Mingwang; Song, Shaofeng; Zhu, Lei; Yuan, Jinfeng; Liu, Gang

2016-08-09

Herein, we demonstrate a facile approach to prepare anisotropic poly(tert-butyl acrylate)/polystyrene (PtBA/PS) composite particles with controllable morphologies by soap-free seeded emulsion polymerization (SSEP). In the first step, noncrosslinked PtBA seeds with self-stabilizing polar functional groups (e.g., ester groups and radicals) are synthesized by soap-free emulsion polymerization. During the subsequent SSEP of styrene (St), PS bulges are nucleated on the PtBA seeds due to the microphase separation confined in the latex particles. The morphology evolution of PtBA/PS composite particles is tailored by varying the monomer/seed feed ratio, polymerization time, and polymerization temperature. Many intriguing morphologies, including hamburger-like, litchi-like, mushroom-like, strawberry-like, bowl-like, and snowman-like, have been acquired for PtBA/PS composite particles. The polar groups on the PtBA seed surface greatly influence the formation and further merging of PS/St bulges during the polymerization. A possible formation mechanism is proposed on the basis of experimental results. These complex composite particles are promising for applications in superhydrophobic coatings.

Flush mounting of thin film sensors

NASA Technical Reports Server (NTRS)

Moore, Thomas C., Sr. (Inventor)

1992-01-01

Flush mounting of a sensor on a surface is provided by first forming a recessed area on the surface. Next, an adhesive bonding mixture is introduced into the recessed area. The adhesive bonding mixture is chosen to provide thermal expansion matching with the surface surrounding the recessed area. A strip of high performance polymeric tape is provided, with the sensor attached to the underside thereof, and the tape is positioned over the recessed area so that it acts as a carrier of the sensor. A shim having flexibility so that it will conform to the surface surrounding the recessed area is placed over the tape, and a vacuum pad is placed over the shim. The area above the surface is then evacuated while holding the sensor flush with the surface during curing of the adhesive bonding mixture. After such curing, the pad, shim, and tape are removed from the sensor, electrical connections for the sensor are provided, after which the remaining space in the recessed area is filled with a polymeric foam.

Polymer brush covalently attached to OH-functionalized mica surface via surface-initiated ATRP: control of grafting density and polymer chain length.

PubMed

Lego, Béatrice; François, Marion; Skene, W G; Giasson, Suzanne

2009-05-05

The controlled grafting density of poly(tert-butyl acrylate) was studied on OH-activated mica substrates via surface-initiated atom-transfer radical polymerization (ATRP). By properly adjusting parameters such as the immobilization reaction time and the concentration of an ATRP initiator, a wide range of initiator surface coverages and hence polymer densities on mica were possible. The covalently immobilized initiator successfully promoted the polymerization of tert-butyl acrylate on mica surfaces. The resulting polymer layer thickness was measured by AFM using a step-height method. Linear relationships of the polymer thickness with respect to the molecular weight of the free polymer and with respect to the monomer conversion were observed, suggesting that ATRP is well controlled and relatively densely end-grafted layers were obtained. The polymer grafting density controlled by adjusting the initiator surface coverage was confirmed by the polymer layer swelling capacity and film thickness measurements.

Non-fouling surfaces produced by gas phase pulsed plasma polymerization of an ultra low molecular weight ethylene oxide containing monomer.

PubMed

Wu; Timmons; Jen; Molock

2000-10-01

The pulsed plasma polymerization of low molecular weight molecules containing only one (ethylene oxide vinyl ether) and two (diethylene oxide vinyl ether) ethylene oxide units were investigated. The surface density of EO units retained in the polymer films increases sharply with decreasing average power input during deposition, particularly at very low plasma duty cycles. The protein adsorption properties of these plasma synthesized polymer were investigated using 125I-labeled albumin and fibrinogen. Surprisingly effective, non-fouling surfaces were observed with films synthesized from the monomer containing two ethylene oxide units; however, the monomer containing only one EO unit gave surfaces that were not particularly effective in preventing protein adsorptions. The results obtained show that ultra short chain length PEO modified surfaces can be biologically non-fouling. This, in turn, has interesting consequences in terms of trying to identify the basic reason for the effectiveness of EO units in preventing biomolecule adsorptions on surfaces.

Electron-beam-induced post-grafting polymerization of acrylic acid onto the surface of Kevlar fibers

NASA Astrophysics Data System (ADS)

Xu, Lu; Hu, Jiangtao; Ma, Hongjuan; Wu, Guozhong

2018-04-01

The surface of Kevlar fibers was successfully modified by electron beam (EB)-induced post-grafting of acrylic acid (AA). The generation of radicals in the fibers was confirmed by electron spin resonance (ESR) measurements, and the concentration of radicals was shown to increase as the absorbed dose increased, but decrease with increasing temperature. The influence of the synthesis conditions on the degree of grafting was also investigated. The surface microstructure and chemical composition of the modified Kevlar fibers were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The SEM images revealed that the surface of the grafted fibers was rougher than those of the pristine and irradiated fibers. XPS analysis confirmed an increase in C(O)OH groups on the surface of the Kevlar fibers, suggesting successful grafting of AA. These results indicate that EB-induced post-grafting polymerization is effective for modifying the surface properties of Kevlar fibers.

The sorption properties of polymers with molecular imprints of 2,4-dichlorophenoxyacetic acid synthesized by various methods

NASA Astrophysics Data System (ADS)

Dmitrienko, S. G.; Popov, S. A.; Chumichkina, Yu. A.; Zolotov, Yu. A.

2011-03-01

New sorbents, polymers with molecular imprints of 2,4-dichlorophenoxyacetic acid (2,4-D), were prepared on the basis of acrylamide. The sorbents were synthesized by thermal polymerization methods with and without the use of ultrasound, photopolymerization, and suspension polymerization. The specific surface area of the products was estimated and their sorption properties were studied. Polymers with molecular imprints prepared by thermal polymerization with the use of ultrasound and by suspension polymerization showed the best ability to repeatedly bind 2,4-D. The selectivity of polymers was estimated for the example of structurally related compounds. It was shown that the method of synthesis decisively influenced not only the ability of sorbents to repeatedly bind 2,4-D but also their selectivity.

A MASS BALANCE OF SURFACE WATER GENOTOXICITY IN PROVIDENCE RIVER (RHODE ISLAND USA)

EPA Science Inventory

White and Rasmussen (Mutation Res. 410:223-236) used a mass balance approach to demonstrate that over 85% of the total genotoxic loading to the St. Lawrence River at Montreal is non-industrial. To validate the mass balance approach and investigate the sources of genotoxins in sur...

Development Report for the 10 KW Sound Attenuation Program (Preproduction ’F’ Kit).

DTIC Science & Technology

1981-12-02

3.2 Panel Design The panels were to be constructed from solid aluminum sheet metal on all ex- ; terior surfaces and acoustic fiberglass or mineral ... wool bill overlayed with a synthetic film and encapsulated with perforated aluminum on the interior sur- faces. Per design, the acoustic panels on the

ETV, LT2 and You: How the Environmental Technology Verification Program Can Assist with the Long Term 2 Enhanced Surface Water Treatment Rule

EPA Science Inventory

The Environmental Technology Verification (ETV) Drinking Water Systems (DWS) Center has verified the performance of treatment technologies that may be used by communities in meeting the newly promulgated (2006) U.S. Environmental Protection Agency (USEPA) Long Term 2 Enhanced Sur...

Emergence of spacetime dynamics in entropy corrected and braneworld models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheykhi, A.; Dehghani, M.H.; Hosseini, S.E., E-mail: asheykhi@shirazu.ac.ir, E-mail: mhd@shirazu.ac.ir, E-mail: elahehhosseini90@gmail.com

2013-04-01

A very interesting new proposal on the origin of the cosmic expansion was recently suggested by Padmanabhan [arXiv:1206.4916]. He argued that the difference between the surface degrees of freedom and the bulk degrees of freedom in a region of space drives the accelerated expansion of the universe, as well as the standard Friedmann equation through relation ΔV = Δt(N{sub sur}−N{sub bulk}). In this paper, we first present the general expression for the number of degrees of freedom on the holographic surface, N{sub sur}, using the general entropy corrected formula S = A/(4L{sub p}{sup 2})+s(A). Then, as two example, by applyingmore » the Padmanabhan's idea we extract the corresponding Friedmann equations in the presence of power-law and logarithmic correction terms in the entropy. We also extend the study to RS II and DGP braneworld models and derive successfully the correct form of the Friedmann equations in these theories. Our study further supports the viability of Padmanabhan's proposal.« less

Putative subunits of the rat mesangial KATP: a type 2B sulfonylurea receptor and an inwardly rectifying K+ channel.

PubMed

Szamosfalvi, Balázs; Cortes, Pedro; Alviani, Rebecca; Asano, Kenichiro; Riser, Bruce L; Zasuwa, Gary; Yee, Jerry

2002-05-01

Sulfonylurea agents exert their physiological effects in many cell types via binding to specific sulfonylurea receptors (SUR). SUR couple to inwardly-rectifying K+ channel (Kir6.x) to form tetradimeric ATP-sensitive K+ channels (KATP). The SUR subunits confer ATP-sensitivity on KATP and also provide the binding sites for sulfonylureas and other pharmacological agents. Our previous work demonstrated that the exposure of mesangial cells (MC) to sulfonylureas generated profound effects on MC glucose uptake and matrix metabolism and induced heightened cell contractility in association with Ca2+ transients. Because these responses likely resulted from the binding of sulfonylurea to a mesangial SUR2, we subsequently documented [3H]-glibenclamide binding to MC and the gene expression of several mesangial SUR2 transcripts. From these data, we inferred that MC expressed the components of a mesangial KATP and sought to establish their presence in primary MC. To obtain mesangial SUR2 cDNA sequences, rapid amplification of cDNA ends (RACE) was utilized. DNA sequences were established by the fluorescent dye termination method. Gene expression of mesangial SUR2 and Kir6.1/2 was examined by reverse transcription polymerase chain reaction (RT-PCR) and Northern analysis. SUR2 proteins were identified by immunoblotting of mesangial proteins from membrane-enriched fractions with polyclonal antiserum directed against SUR2. RACE cloning yielded two mesangial SUR2 cDNAs of 4.8 and 6.7 kbp whose open reading frames translated proteins of 964 and 1535 aa, respectively. Using probes specific to each cDNA, the presence of a unique, 5.5 kbp serum-regulated mesangial SUR2 splice variant was established. The sequence of this mesangial SUR2 (mcSUR2B) shares identity with the recently cloned rat SUR2B (rSUR2B), but, in comparison to rSUR2B, is truncated by 12 exons at the N-terminus where it contains a unique insert of 16 aa. Immunoblotting studies with anti-SUR2 antiserum demonstrated SUR2 proteins of 108 and 170 kD in membrane-enriched fractions of MC protein extracts. Complementary studies showed abundant gene expression of Kir6.1, thereby establishing gene expression of both components of KATP. Based upon analogy to vascular smooth muscle cells (VSMC), there are at least two putative mesangial KATP that most likely represent hetero-octamers, comprised of either rSUR2B or mcSUR2 in complex with Kir6.1. Our results define the mesangial SUR2B as the possible first link in a chain of cellular events that culminates in MC contraction and altered extracellular matrix metabolism following exposure to sulfonylureas. In addition, our results serve as the basis for the future elucidation of the electrophysiologic characteristics of the mesangial KATP and the study of endogenous regulators of mesangial cell contractility.

Evaluation of a combined drug-delivery system for proteins assembled with polymeric nanoparticles and porous microspheres; characterization and protein integrity studies.

PubMed

Alcalá-Alcalá, Sergio; Benítez-Cardoza, Claudia G; Lima-Muñoz, Enrique J; Piñón-Segundo, Elizabeth; Quintanar-Guerrero, David

2015-07-15

This work presents an evaluation of the adsorption/infiltration process in relation to the loading of a model protein, α-amylase, into an assembled biodegradable polymeric system, free of organic solvents and made up of poly(D,L-lactide-co-glycolide) acid (PLGA). Systems were assembled in a friendly aqueous medium by adsorbing and infiltrating polymeric nanoparticles into porous microspheres. These assembled systems are able to load therapeutic amounts of the drug through adsorption of the protein onto the large surface area characteristic of polymeric nanoparticles. The subsequent infiltration of nanoparticles adsorbed with the protein into porous microspheres enabled the controlled release of the protein as a function of the amount of infiltrated nanoparticles, since the surface area available on the porous structure is saturated at different levels, thus modifying the protein release rate. Findings were confirmed by both the BET technique (N2 isotherms) and in vitro release studies. During the adsorption process, the pH of the medium plays an important role by creating an environment that favors adsorption between the surfaces of the micro- and nano-structures and the protein. Finally, assays of α-amylase activity using 2-chloro-4-nitrophenyl-α-D-maltotrioside (CNP-G3) as the substrate and the circular dichroism technique confirmed that when this new approach was used no conformational changes were observed in the protein after release. Copyright © 2015 Elsevier B.V. All rights reserved.

Measurement of the full-field polymerization shrinkage and depth of cure of dental composites using digital image correlation.

PubMed

Li, Jianying; Fok, Alex S L; Satterthwaite, Julian; Watts, David C

2009-05-01

The aim of this study was to measure the full-field polymerization shrinkage of dental composites using optical image correlation method. Bar specimens of cross-section 4mm x 2mm and length 10mm approximately were light cured with two irradiances, 450 mW/cm(2) and 180 mW/cm(2), respectively. The curing light was generated with Optilux 501 (Kerr) and the two different irradiances were achieved by adjusting the distance between the light tip and the specimen. A single-camera 2D measuring system was used to record the deformation of the composite specimen for 30 min at a frequency of 0.1 Hz. The specimen surface under observation was sprayed with paint to produce sufficient contrast to allow tracking of individual points on the surface. The curing light was applied to one end of the specimen for 40s during which the painted surface was fully covered. After curing, the cover was removed immediately so that deformation of the painted surface could be recorded by the camera. The images were then analyzed with specialist software and the volumetric shrinkage determined along the beam length. A typical shrinkage strain field obtained on a specimen surface was highly non-uniform, even at positions of constant distance from the irradiation surface, indicating possible heterogeneity in material composition and shrinkage behavior in the composite. The maximum volumetric shrinkage strain of approximately 1.5% occurred at a subsurface distance of about 1mm, instead of at the irradiation surface. After reaching its peak value, the shrinkage strain then gradually decreased with increasing distance along the beam length, before leveling off to a value of approximately 0.2% at a distance of 4-5mm. The maximum volumetric shrinkage obtained agreed well with the value of 1.6% reported by the manufacturer for the composite examined in this work. Using irradiance of 180 mW/cm(2) resulted in only slightly less polymerization shrinkage than using irradiance of 450 mW/cm(2). Compared to the other measurement methods, the image correlation method is capable of producing full-field information about the polymerization shrinkage behavior of dental composites.

Aubrite and Impact Melt Enstatite Chondrite Meteorites as Potential Analogs to Mercury

NASA Technical Reports Server (NTRS)

Wilbur, Z. E.; Udry, A.; Mccubbin, Francis M.; McCubbin, F. M.; Combs, L. M.; Rahib, R. R.; McCoy, C.; McCoy, T. J.

2018-01-01

The MESSENGER (MErcury Sur-face, Space ENvironment, GEochemistry and Ranging) orbiter measured the Mercurian surface abundances of key rock-forming elements to help us better understand the planet's surface and bulk geochemistry. A major discovery is that the Mercurian surface and interior are characterized by an extremely low oxygen fugacity (ƒO2; Iron-Wüstite (IW) -7.3 to IW-2.6. This is supported by low Fe and high S abundances on the surface. This low ƒO2 causes a different elemental partioning from what is observed on Earth. Using surface composition, it was shown that the Mercurian surface mainly consists of normative plagioclase, pyroxene, olivine, and exotic sulfides, such as niningerite ((Mg,Mn, Fe)S) and oldhamite (CaS).

The ATP-sensitive potassium (KATP) channel-encoded dSUR gene is required for Drosophila heart function and is regulated by tinman

PubMed Central

Akasaka, Takeshi; Klinedinst, Susan; Ocorr, Karen; Bustamante, Erika L.; Kim, Seung K.; Bodmer, Rolf

2006-01-01

The homeobox transcription factor Tinman plays an important role in the initiation of heart development. Later functions of Tinman, including the target genes involved in cardiac physiology, are less well studied. We focused on the dSUR gene, which encodes an ATP-binding cassette transmembrane protein that is expressed in the heart. Mammalian SUR genes are associated with KATP (ATP-sensitive potassium) channels, which are involved in metabolic homeostasis. We provide experimental evidence that Tinman directly regulates dSUR expression in the developing heart. We identified a cis-regulatory element in the first intron of dSUR, which contains Tinman consensus binding sites and is sufficient for faithful dSUR expression in the fly’s myocardium. Site-directed mutagenesis of this element shows that these Tinman sites are critical to dSUR expression, and further genetic manipulations suggest that the GATA transcription factor Pannier is synergistically involved in cardiac-restricted dSUR expression in vivo. Physiological analysis of dSUR knock-down flies supports the idea that dSUR plays a protective role against hypoxic stress and pacing-induced heart failure. Because dSUR expression dramatically decreases with age, it is likely to be a factor involved in the cardiac aging phenotype of Drosophila. dSUR provides a model for addressing how embryonic regulators of myocardial cell commitment can contribute to the establishment and maintenance of cardiac performance. PMID:16882722

Finite element analysis of heat generation from different light-polymerization sources during cementation of all-ceramic crowns.

PubMed

Tunc, Elif Pak

2007-06-01

Exothermic composite resin chemical reactions and visible light generators can produce heat during a restorative polymerization process. These thermal changes in restored teeth may cause pain and irreversible pulpitis. The purpose of this study was to analyze the temperature distribution and heat flow patterns of a crowned mandibular second premolar tooth model using 3 different light-polymerization technologies and a finite element technique. A 2-dimensional finite element model was used to simulate a clinical condition. Heat flow and thermal stress distribution in a tooth during cementation of an all-ceramic crown using 4 commercially available light-polymerization units (LPUs), each with different wavelengths (Elipar TriLight, Elipar Freelight, Apollo 95 E, and ADT 1000 PAC), were investigated. The temperature values were measured at 3, 10, 12, and 40 seconds for each light-polymerizing unit (LPU) at 6 different finite element nodes. Two-dimensional temporal and spatial distribution of the thermal stress within the tooth, including the thermal coefficients and boundary conditions of the dental materials, were obtained and evaluated. The temperature at the nodal points did not exceed 42 degrees C, which is a threshold value for tissue vitality within the recommended operating periods at the dentin and pulp surface for all LPUs, except for Elipar TriLight. In the case of Elipar TriLlight, the temperatures at the dentin and pulp surfaces were 47 degrees C and 42 degrees C, respectively. When the light-polymerization units were used according to the manufacturers' operating procedures and without prolonged operating periods, with the exception of Elipar TriLight, the investigated LPUs did not produce significant heat. However, when the operating periods were prolonged, unacceptable temperature increases were observed, especially with the high-intensity LPUs.

Contact angle and surface free energy of experimental resin-based dental restorative materials after chewing simulation.

PubMed

Rüttermann, Stefan; Beikler, Thomas; Janda, Ralf

2014-06-01

To investigate contact angle and surface free energy of experimental dental resin composites containing novel delivery systems of polymeric hollow beads and low-surface tension agents after chewing simulation test. A delivery system of novel polymeric hollow beads differently loaded with two low-surface tension agents was used in different amounts to modify commonly formulated experimental dental resin composites. The non-modified resin was used as standard. Surface roughness Ra, contact angle Θ, total surface free energy γS, its apolar γS(LW), polar γS(AB), Lewis acid γS(+) and base γS(-) terms were determined and the results prior to and after chewing simulation test were compared. Significance was p<0.05. After chewing simulation Ra increased, Θ decreased, Ra increased for two test materials and γS decreased or remained constant for the standard or the test materials after chewing simulation. Ra of one test material was higher than of the standard, Θ and γS of the test materials remained lower than of the standard and, indicating their highly hydrophobic character (Θ≈60-75°, γS≈30mJm(-2)). γS(LW), and γS(-) of the test materials were lower than of the standard. Some of the test materials had lower γS(AB) and γS(+) than of the standard. Delivery systems based on novel polymeric hollow beads highly loaded with low-surface tension agents were found to significantly increase contact angle and thus to reduce surface free energy of experimental dental resin composites prior to and after chewing simulation test. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Effect of denture cleaning on abrasion resistance and surface topography of polymerized CAD CAM acrylic resin denture base

PubMed Central

Shinawi, Lana Ahmed

2017-01-01

Background The application of computer-aided design computer-aided manufacturing (CAD CAM) technology in the fabrication of complete dentures, offers numerous advantages as it provides optimum fit and eliminates polymerization shrinkage of the acrylic base. Additionally, the porosity and surface roughness of CAD CAM resins is less compared to conventionally processed resins which leads to a decrease in the adhesion of bacteria on the denture base, which is associated with many conditions including halitosis and aspiration pneumonia in elderly denture wearers. Aim To evaluate the influence of tooth brushing with dentifrices on CAD CAM resin blocks in terms of abrasion resistance, surface roughness and scanning electron photomicrography. Methods This experimental study was carried out at the Faculty of Dentistry of King Abdulaziz University during 2016. A total of 40 rectangular shaped polymerized CAD CAM resin samples were subjected to 40.000 and 60.000 brushing strokes under a 200-gram vertical load simulating three years of tooth brushing strokes using commercially available denture cleaning dentifrice. Data were analyzed by SPSS version 20, using descriptive statistics and ANOVA. Results ANOVA test revealed a statistical significant weight loss of CAD CAM acrylic resin denture base specimens following 40.000 and 60.000 brushing strokes as well as a statistical significant change (p=0.0.5) in the surface roughness following brushing. The CAD CAM resin samples SEM baseline imaging revealed a relatively smooth homogenous surface, but following 40,000 and 60,000 brushing strokes, imaging displayed the presence of small scratches on the surface. Conclusion CAD CAM resin displayed a homogenous surface initially with low surface roughness that was significantly affected following simulating three years of manual brushing, but despite the significant weight loss, the findings are within the clinically acceptable limits. PMID:28713496

Effect of denture cleaning on abrasion resistance and surface topography of polymerized CAD CAM acrylic resin denture base.

PubMed

Shinawi, Lana Ahmed

2017-05-01

The application of computer-aided design computer-aided manufacturing (CAD CAM) technology in the fabrication of complete dentures, offers numerous advantages as it provides optimum fit and eliminates polymerization shrinkage of the acrylic base. Additionally, the porosity and surface roughness of CAD CAM resins is less compared to conventionally processed resins which leads to a decrease in the adhesion of bacteria on the denture base, which is associated with many conditions including halitosis and aspiration pneumonia in elderly denture wearers. To evaluate the influence of tooth brushing with dentifrices on CAD CAM resin blocks in terms of abrasion resistance, surface roughness and scanning electron photomicrography. This experimental study was carried out at the Faculty of Dentistry of King Abdulaziz University during 2016. A total of 40 rectangular shaped polymerized CAD CAM resin samples were subjected to 40.000 and 60.000 brushing strokes under a 200-gram vertical load simulating three years of tooth brushing strokes using commercially available denture cleaning dentifrice. Data were analyzed by SPSS version 20, using descriptive statistics and ANOVA. ANOVA test revealed a statistical significant weight loss of CAD CAM acrylic resin denture base specimens following 40.000 and 60.000 brushing strokes as well as a statistical significant change (p=0.0.5) in the surface roughness following brushing. The CAD CAM resin samples SEM baseline imaging revealed a relatively smooth homogenous surface, but following 40,000 and 60,000 brushing strokes, imaging displayed the presence of small scratches on the surface. CAD CAM resin displayed a homogenous surface initially with low surface roughness that was significantly affected following simulating three years of manual brushing, but despite the significant weight loss, the findings are within the clinically acceptable limits.

Light transmittance and surface roughness of a feldspathic ceramic CAD-CAM material as a function of different surface treatments.

PubMed

Ural, Çağrı; Duran, İbrahim; Evmek, Betül; Kavut, İdris; Cengiz, Seda; Yuzbasioglu, Emir

2016-07-15

The aim of the present study was to determine the effect of different surface treatments on light transmission of aesthetic feldspathic ceramics used in CAD-CAM chairside restorations. Forty eight feldspatic ceramic test specimens were prepared from prefabricated CAD-CAM blocks by using a slow speed diamond saw. Test specimens were prepared and divided into 4 groups (n = 12). In the control group, no surface treatments were applied on the feldspathic ceramic surfaces. In the hydrofluoric acid group, the bonding surfaces of feldspathic ceramics were etched with 9.5 % hydrofluoric acid. In the sandblasting group the feldspathic ceramic surfaces were air-abraded with 30-μm alumium oxide (Al2O3) particles and Er:YAG laser was used to irradiate the ceramic surfaces. The incident light power given by the LED device and the transmitted light power through each ceramic sample was registered using a digital LED radiometer device. Each polymerization light had a light guide with 8-mm-diameter tips. Light transmission of feldspathic ceramic samples was determined by placing it on the radiometer and irradiating the specimen for 10 s at the highest setting for each light polymerization. All specimens were coated with gold using a sputter coater and examined under a field emission scanning electron microscope. Surface roughness measurement each group were evaluated with 3D optical surface and tactile profilometers. One-way ANOVA test results revealed that both surface conditioning method significantly affect the light transmittance (F:412.437; p < 0.001) and the surface roughness values (F:16.386; p < 0.001). Al2O3 and Er-YAG laser application reduced the light transmission significantly (p < 0.05). The laser and Al2O3 applications reduced the light transmission of 1.5 mm thickness feldspathic ceramic material below the value of 400 mW/cm(2) which is critical limit for safe polymerization.

Towards Well-Defined Polysilylenes and Polyphosphazenes

DTIC Science & Technology

1992-05-25

distribution), non - controlled degrees of polymerization and unknown end cyclopentasilanes 2 8 . The anionic intermediates have been observed groups. Some... control in polysilanes will be presented: ring-opening polymerization, and polymer modications.. Block and graft copolymers based on polysilanes will be...34sticks" to the surface of alkali metal and continues to grow to high possible to prepare polymers with controlled molecular weight, with low m"m

The effect of environmental pH on polymeric transfection efficiency.

PubMed

Kang, Han Chang; Samsonova, Olga; Kang, Sun-Woong; Bae, You Han

2012-02-01

Although polymers, polyplexes, and cells are exposed to various extracellular and intracellular pH environments during polyplex preparation and polymeric transfection, the impact of environmental pH on polymeric transfection has not yet been investigated. This study aims to understand the influence of environmental pH on polymeric transfection by modulating the pH of the transfection medium or the culture medium. Changes in the extracellular pH affected polymeric transfection by way of complex factors such as pH-induced changes in polymer characteristics (e.g., proton buffering capacity and ionization), polyplex characteristics (e.g., size, surface charge, and decomplexation), and cellular characteristics (e.g., cellular uptake, cell cycle phases, and intracellular pH environment). Notably, acidic medium delayed endocytosis, endosomal acidification, cytosolic release, and decomplexation of polyplexes, thereby negatively affecting gene expression. However, acidic medium inhibited mitosis and reduced dilution of gene expression, resulting in increased transfection efficiency. Compared to pH 7.4 medium, acidic transfection medium reduced gene expression 1.6-7.7-fold whereas acidic culture medium enhanced transfection efficiency 2.1-2.6-fold. Polymeric transfection was affected more by the culture medium than by the transfection medium. Understanding the effects of extracellular pH during polymeric transfection may stimulate new strategies for determining effective and safe polymeric gene carriers. Copyright © 2011 Elsevier Ltd. All rights reserved.

Impact of low-pressure glow-discharge-pulsed plasma polymerization on properties of polyaniline thin films

NASA Astrophysics Data System (ADS)

Jatratkar, Aviraj A.; Yadav, Jyotiprakash B.; Deshmukh, R. R.; Barshilia, Harish C.; Puri, Vijaya; Puri, R. K.

2016-12-01

This study reports on polyaniline thin films deposited on a glass substrate using a low-pressure glow-discharge-pulsed plasma polymerization method. The polyaniline thin film obtained by pulsed plasma polymerization has been successfully demonstrated as an optical waveguide with a transmission loss of 3.93 dB cm-1, and has the potential to be employed in integrated optics. An attempt has been made to investigate the effect of plasma OFF-time on the structural, optical as well as surface properties of polyaniline thin film. The plasma ON-time has been kept constant and the plasma OFF-time has been varied throughout the work. The plasma OFF-time strongly influenced the properties of the polyaniline thin film, and a nanostructured and compact surface was revealed in the morphological studies. The plasma OFF-time was found to enhance film thickness, roughness, refractive index and optical transmission loss, whereas it reduced the optical band gap of the polyaniline thin films. Retention in the aromatic structure was confirmed by FTIR results. Optical studies revealed a π-π* electronic transition at about 317 nm as well as the formation of a branched structure. As compared with continuous wave plasma, pulsed plasma polymerization shows better properties. Pulsed plasma polymerization reduced the roughness of the film from 1.2 nm to 0.42 nm and the optical transmission loss from 6.56 dB cm-1 to 3.39 dB cm-1.

Prediction of Aerodynamic Characteristics of Fighter Wings at High Angles of Attack.

DTIC Science & Technology

1984-03-01

potential distribution throughout the network of four points on a body surface great- ly facilitates the flow analysis procedure. Tangential velocity...expensive of computer time. For example, as quoted by McLean, using this coarsest grid network , each 0 surface of the 727-200 wing required 10 minutes of...1980. 19. Le Balleur, J.C. and Neron , M., "Calcul D’Ecoulements3 Visqueux Decolles sur Profils D’Ailes par une Approche de Couplage", AGARn CP-291

Theoretical Studies of Defects in Tetrahedral Semiconductors.

DTIC Science & Technology

1980-08-01

pulse. The exact time of the maximal sur- has been measured by Shvarev et al. [I I at 1.0, face temperature depends on pulse duration, thermal 0.7 and...0.4 lAn from 57.50 off normal incidence. diffusivity (which is generally T dependent ), pulse Auston et al. (81 reported the time resolved reflec- shape...surface occur 30 to 40 ns after the peak of their 25 ns HWHM or ripples on the surface or a temperature depend - gaussian pulse rather than within

Études par diffraction haute résolution et réflectivité de films minces épitaxiés

NASA Astrophysics Data System (ADS)

Baulès, P.; Casanove, M. J.; Roucau, C.; Ousset, J. C.; Bobo, J. F.; Snoeck, E.; Magnoux, D.; Gatel, C.

2002-07-01

The studies we present concern the general researches involved in order to understand the growth mechanisms of thin films deposited on oriented substrates. Among the different investigation technics of the thin layers, X-ray diffraction and reflectivity will be discussed through two applications. In a first step, thediffraction presented, illustrated by reciprocal space mapping, will give information about the layer state of stress and the lattice distorsion of La{1-x}SrxMnO3 deposited on SrTiO3. The results obtained are discussed and compared to those given by electron microscopy. In a second step, we will present an application of reflectivity concerning a very roughness surface of platinum deposited on MgO showing an island growth process. We will verify that reflectivity can lead to the determination of the recovered rate of the surface, even if some problems exist in the simulation of the whole data set. Results obtained in electron microscopy will complete those issued from reflectivity. Les études que nous allons présenter sont à replacer dans le contexte général de la compréhension des mécanismes de croissance des films minces déposés sur des substrats orientés. Parmi les diverses techniques d'investigations des couches minces, la diffraction et la réflectivité des rayons X vont être abordées à travers deux applications. Nous verrons tout d'abord que la diffraction, illustrée par la cartographie en deux dimension du réseau réciproque, permet de remonter à l'état de contrainte ainsi qu'à la déformation de la maille de La{1-x}SrxMnO3 déposé sur SrTiO3. Les résultats déduits de ces mesures seront discutés et comparés à ceux obtenus en microscopie électronique. Dans la suite de l'article, nous verrons une des applications de la réflectivité, sur une surface très perturbée de platine déposé sur MgO et présentant une croissance en îlots. Nous verrons que la réflectivité permet d'estimer le taux de recouvrement de la surface, mais que des problèmes persistent dans la simulation de l'intégralité des données expérimentales. Les résultats obtenus en MET viendront compléter ceux issus de la réflectivité.

Polymeric Flexible Immunosensor Based on Piezoresistive Micro-Cantilever with PEDOT/PSS Conductive Layer.

PubMed

Zhao, Rui; Sun, Ying

2018-02-03

In this paper, a fully polymeric micro-cantilever with the surface passivation layer of parylene-C and the strain resistor of poly(3,4-ethylenedioxythiophene)/poly (styrene sulfonate) (PEDOT/PSS) was proposed and demonstrated for immunoassays. By optimizing the design and fabrication of the polymeric micro-cantilever, a square resistance of 220 Ω/□ for PEDOT/PSS conductive layer have been obtained. The experimental spring constant and the deflection sensitivity were measured to be 0.017 N/m and 8.59 × 10 -7 nm -1 , respectively. The biological sensing performances of polymeric micro-cantilever were investigated by the immunoassay for human immunoglobulin G (IgG). The immunosensor was experimentally demonstrated to have a linear behavior for the detection of IgG within the concentrations of 10~100 ng/mL with a limit of detection (LOD) of 10 ng/mL. The experimental results indicate that the proposed polymeric flexible conductive layer-based sensors are capable of detecting trace biological substances.

Plasma-induced graft-polymerization of polyethylene glycol acrylate on polypropylene substrates

NASA Astrophysics Data System (ADS)

Zanini, S.; Orlandi, M.; Colombo, C.; Grimoldi, E.; Riccardi, C.

2009-08-01

A detailed study of argon plasma-induced graft-polymerization of polyethylene glycol acrylate (PEGA) on polypropylene (PP) substrates (membranes and films) is presented. The process consists of four steps: (a) plasma pre-activation of the PP substrates; (b) immersion in a PEGA solution; (c) argon plasma-induced graft-polymerization; (d) washing and drying of the samples. Influence of the solution and plasma parameters on the process efficiency evaluated in terms of amount of grafted polymer, coverage uniformity and substrates wettability, are investigated. The plasma-induced graft-polymerization of PEGA is then followed by sample weighting, water droplet adsorption time and contact angle measurements, attenuated total reflection infrared spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analyses. The stability of the obtained thin films was evaluated in water and in phosphate buffer saline (PBS) at 37 °C. Results clearly indicates that plasma-induced graft-polymerization of PEGA is a practical methodology for anti-fouling surface modification of materials.

Polymeric Flexible Immunosensor Based on Piezoresistive Micro-Cantilever with PEDOT/PSS Conductive Layer

PubMed Central

Sun, Ying

2018-01-01

In this paper, a fully polymeric micro-cantilever with the surface passivation layer of parylene-C and the strain resistor of poly(3,4-ethylenedioxythiophene)/poly (styrene sulfonate) (PEDOT/PSS) was proposed and demonstrated for immunoassays. By optimizing the design and fabrication of the polymeric micro-cantilever, a square resistance of 220 Ω/□ for PEDOT/PSS conductive layer have been obtained. The experimental spring constant and the deflection sensitivity were measured to be 0.017 N/m and 8.59 × 10−7 nm−1, respectively. The biological sensing performances of polymeric micro-cantilever were investigated by the immunoassay for human immunoglobulin G (IgG). The immunosensor was experimentally demonstrated to have a linear behavior for the detection of IgG within the concentrations of 10~100 ng/mL with a limit of detection (LOD) of 10 ng/mL. The experimental results indicate that the proposed polymeric flexible conductive layer-based sensors are capable of detecting trace biological substances. PMID:29401669

Intracellular delivery of polymeric nanocarriers: a matter of size, shape, charge, elasticity and surface composition.

PubMed

Agarwal, Rachit; Roy, Krishnendu

2013-06-01

Recent progress in drug discovery has enabled the targeting of specific intracellular molecules to achieve therapeutic effects. These next-generation therapeutics are often biologics that cannot enter cells by mere diffusion. Therefore, it is imperative that drug carriers are efficiently internalized by cells and reach specific target organelles before releasing their cargo. Nanoscale polymeric carriers are particularly suitable for such intracellular delivery. Although size and surface charge have been the most studied parameters for nanocarriers, it is now well appreciated that other properties, for example, particle shape, elasticity and surface composition, also play a critical role in their transport across physiological barriers. It is proposed that a multivariate design space that considers the interdependence of particle geometry with its mechanical and surface properties must be optimized to formulate drug nanocarriers for effective accumulation at target sites and efficient intracellular delivery.

Hierarchically porous carbon/polyaniline hybrid for use in supercapacitors.

PubMed

Joo, Min Jae; Yun, Young Soo; Jin, Hyoung-Joon

2014-12-01

A hierarchically porous carbon (HPC)/polyaniline (PANI) hybrid electrode was prepared by the polymerization of PANI on the surface of the HPC via rapid-mixing polymerization. The surface morphologies and chemical composition of the HPC/PANI hybrid electrode were characterized using transmission electron microscopy and X-ray photoelectron spectroscopy (XPS), respectively. The surface morphologies and XPS results for the HPC, PANI and HPC/PANI hybrids indicate that PANI is coated on the surface of HPC in the HPC/PANI hybrids which have two different nitrogen groups as a benzenoid amine (-NH-) peak and positively charged nitrogen (N+) peak. The electrochemical performances of the HPC/PANI hybrids were analyzed by performing cyclic voltammetry and galvanostatic charge-discharge tests. The HPC/PANI hybrids showed a better specific capacitance (222 F/g) than HPC (111 F/g) because of effect of pseudocapacitor behavior. In addition, good cycle stabilities were maintained over 1000 cycles.

Quantitative Transmission Electron Microscopy of Nanoparticles and Thin-Film Formation in Electroless Metallization of Polymeric Surfaces

NASA Astrophysics Data System (ADS)

Dutta, Aniruddha; Heinrich, Helge; Kuebler, Stephen; Grabill, Chris; Bhattacharya, Aniket

2011-03-01

Gold nanoparticles(Au-NPs) act as nucleation sites for electroless deposition of silver on functionalized SU8 polymeric surfaces. Here we report the nanoscale morphology of Au and Ag nanoparticles as studied by Transmission Electron Microscopy (TEM). Scanning TEM with a high-angle annular dark-field detector is used to obtain atomic number contrast. From the intensity-calibrated plan-view scanning TEM images we determine the mean thickness and the volume distribution of the Au-NPs on the surface of the functionalized polymer. We also report the height and the radius distribution of the gold nanoparticles obtained from STEM images taking into consideration the experimental errors. The cross sectional TEM images yield the density and the average distance of the Au and Ag nanoparticles on the surface of the polymer. Supported by grant NSF, Chemistry Division.

Facile surface modification of glass with zwitterionic polymers for improving the blood compatibility

NASA Astrophysics Data System (ADS)

Zhang, Lingling; Chen, Xiaojuan; Liu, Pingsheng; Wang, Jing; Zhu, Haomiao; Li, Li

2018-06-01

A facile procedure to modify glass film with zwitterionic polymers for improving the blood compatibility was introduced. The glass slides were first silanized with 3-methacryloxypropyltrimethoxysilane (MPT) to generate methacrylate groups on the surface. Then, N, N’-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) ammonium (DMMSA), a sulfobetaine zwitterionic monomer, was polymerized on the silanized glass substrates by free-radical polymerization in order to graft the zwitterionic polymers onto the substrates. X-ray Photoelectron Spectroscopy (XPS), water contact angle, scanning electron microscope (SEM) and atomic force microscopy (AFM) were utilized to analyze the surface properties of the grafted glass. The blood compatibility of the grafted glass was verified by whole blood contacting and platelet adhesion experiments in vitro. The results showed that the zwitterionic polymers were successfully grafted on the glass surface, and consequently significantly inhibited the platelet adhesion and whole blood cell attachment.

Electron beam-induced graft polymerization of acrylic acid and immobilization of arginine-glycine-aspartic acid-containing peptide onto nanopatterned polycaprolactone.

PubMed

Sun, Hui; Wirsén, Anders; Albertsson, Ann-Christine

2004-01-01

Electron beam- (EB-) induced graft polymerization of acrylic acid and the subsequent immobilization of arginine-glycine-aspartic acid (RGD) peptide onto nanopatterned polycaprolactone with parallel grooves is reported. A high concentration of carboxylic groups was introduced onto the polymer substrate by EB-induced polymerization of acrylic acid. In the coupling of the RGD peptide to the carboxylated polymer surface, a three-step peptide immobilization process was used. This process included the activation of surface carboxylic acid into an active ester intermediate by use of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), the introduction of disulfide groups by use of 2-(2-pyridinyldithio)ethanamine hydrochloride (PDEA), and final immobilization of the peptide via a thiol-disulfide exchange reaction. The extent of coupling was measured by UV spectroscopy. A preliminary study of the in vitro behavior of keratinocytes (NCTC 2544) cultured on the acrylic acid-grafted and RGD peptide-coupled surface showed that most cells grown on the coupled samples had a spread-rounded appearance, while the majority of cells tended to be elongated along the grooves on uncoupled substrates.

Adhesion in ceramics and magnetic media

NASA Technical Reports Server (NTRS)

Miyoshi, Kazuhisa

1989-01-01

When a ceramic is brought into contact with a metal or a polymeric material such as a magnetic medium, strong bonds form between the materials. For ceramic-to-metal contacts, adhesion and friction are strongly dependent on the ductility of the metals. Hardness of metals plays a much more important role in adhesion and friction than does the surface energy of metals. Adhesion, friction, surface energy, and hardness of a metal are all related to its Young's modulus and shear modulus, which have a marked dependence on the electron configuration of the metal. An increase in shear modulus results in a decrease in area of contact that is greater than the corresponding increase in surface energy (the fond energy) with shear modulus. Consequently, the adhesion and friction decrease with increasing shear modulus. For ceramics in contact with polymeric magnetic tapes, environment is extremely important. For example, a nitrogen environment reduces adhesion and friction when ferrite contacts polymeric tape, whereas a vacuum environment strengthens the ferrite-to-tape adhesion and increases friction. Adhesion and friction are strongly dependent on the particle loading of the tape. An increase in magnetic particle concentration increases the complex modulus of the tape, and a lower real area of contact and lower friction result.

Blood clearance and biodistribution of polymer brush-afforded silica particles prepared by surface-initiated living radical polymerization.

PubMed

Ohno, Kohji; Akashi, Tatsuki; Tsujii, Yoshinobu; Yamamoto, Masaya; Tabata, Yasuhiko

2012-03-12

The physiological properties of polymer brush-afforded silica particles prepared by surface-initiated living radical polymerization were investigated in terms of the circulation lifetime in the blood and distribution in tissues. Hydrophilic polymers consisting mainly of poly(poly(ethylene glycol) methyl ether methacrylate) were grafted onto silica particles by surface-initiated atom transfer radical polymerization that was mediated by a copper complex to produce hairy hybrid particles. A series of hybrid particles was synthesized by varying the diameter of the silica core and the chain length of the polymer brush to examine the relationship between their physicochemical and physiological properties. The hybrid particles were injected intravenously into mice to investigate systematically their blood clearance and body distribution. It was revealed that the structural features of the hybrid particles significantly affected their in vivo pharmacokinetics. Some hybrid particles exhibited an excellently prolonged circulation lifetime in the blood with a half life of ∼20 h. When such hybrid particles were injected intravenously into a tumor-bearing mouse, they preferentially accumulated in tumor tissue. The tumor-targeted delivery was optically visualized using hybrid particles grafted with fluorescence-labeled polymer brushes.

Functionalization of multi-walled carbon nanotubes by epoxide ring-opening polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin Fanlong; Rhee, Kyong Yop; Park, Soo-Jin, E-mail: sjpark@inha.ac.kr

2011-12-15

In this study, covalent functionalization of carbon nanotubes (CNTs) was accomplished by surface-initiated epoxide ring-opening polymerization. FT-IR spectra showed that polyether and epoxide group covalently attached to the sidewalls of CNTs. TGA results indicated that the polyether was successfully grown from the CNT surface, with the final products having a polymer weight percentage of ca. 14-74 wt%. The O/C ratio of CNTs increased significantly from 5.1% to 29.8% after surface functionalization of CNTs. SEM and TEM images of functionalized CNTs exhibited that the tubes were enwrapped by polymer chains with thickness of several nanometers, forming core-shell structures with CNTs atmore » the center. - Graphical abstract: Functionalized CNTs were enwrapped by polymer chains with thickness of several nanometers, forming core-shell structures with CNTs at the center. Highlights: Black-Right-Pointing-Pointer CNTs were functionalized by epoxide ring-opening polymerization. Black-Right-Pointing-Pointer Polyether and epoxide group covalently attached to the sidewalls of CNTs. Black-Right-Pointing-Pointer Functionalized CNTs have a polymer weight percentage of ca. 14-74 wt%. Black-Right-Pointing-Pointer Functionalized CNTs were enwrapped by polymer chains with thickness of several nanometers.« less

Coating gigaporous polystyrene microspheres with cross-linked poly(vinyl alcohol) hydrogel as a rapid protein chromatography matrix.

PubMed

Qu, Jian-Bo; Huan, Guan-Sheng; Chen, Yan-Li; Zhou, Wei-Qing; Liu, Jian-Guo; Huang, Fang

2014-08-13

Gigaporous polystyrene (PS) microspheres were hydrophilized by in situ polymerization to give a stable cross-linked poly(vinyl alcohol) (PVA) hydrogel coating, which can shield proteins from the hydrophobic PS surface underneath. The amination of microspheres (PS-NH2) was first carried out through acetylization, oximation and reduction, and then 4,4'-azobis (4-cyanovaleric acid) (ACV), a polymerization initiator, was covalently immobilized on PS-NH2 through amide bond formation, and the cross-linked poly(vinyl acetate) (PVAc) was prepared by radical polymerization at the surfaces of ACV-immobilized PS microspheres (PS-ACV). Finally, the cross-linked PVA hydrogel coated gigaporous PS microspheres (PS-PVA) was easily achieved through alcoholysis of PVAc. Results suggested that the PS microspheres were effectively coated with cross-linked PVA hydrogel, where the gigaporrous structure remained under optimal conditions. After hydrophilic modification (PS-PVA), the protein-resistant ability of microspheres was greatly improved. The hydroxyl-rich PS-PVA surface can be easily derivatized by classical chemical methods. Performance advantages of the PS-PVA column in flow experiment include good permeability, low backpressure, and mechanical stability. These results indicated that PS-PVA should be promising in rapid protein chromatography.

Stabilization of enzymatically polymerized phenolic chemicals in a model soil organic matter-free geomaterial.

PubMed

Palomo, Mónica; Bhandari, Alok

2012-01-01

A variety of remediation methods, including contaminant transformation by peroxidase-mediated oxidative polymerization, have been proposed to manage soils and groundwater contaminated with chlorinated phenols. Phenol stabilization has been successfully observed during cross polymerization between phenolic polymers and soil organic matter (SOM) for soils with SOM >3%. This study evaluates peroxidase-mediated transformation and removal of 2,4-dichlorophenol (DCP) from an aqueous phase in contact with a natural geomaterial modified to contain negligible (<0.3%) SOM. The results are compared with those for soils with higher SOM. The SOM-free sorbent was generated by removing SOM using a NaOCl oxidation. When horseradish peroxidase (HRP) was used to induce polymerization of DCP, the soil-water phase distribution relationship (PDR) of DCP polymerization products (DPP) was complete within 1 d and PDRs did not significantly change over the 28 d of study. The conversion of DCP to DPP was close to 95% efficient. Extractable solute consisted entirely of DPP with 5% or less of unreacted DCP. The aqueous extractability of DPP from SOM-free geomaterial decreased at longer contact times and at smaller residual aqueous concentrations of DPP. DCP stabilization appeared to have resulted from a combination of sorption, precipitation, and ligand exchange between oligomeric products and the exposed mineral surfaces. Modification of the mineral surface through coverage with DPP enhanced the time-dependent retention of the oligomers. DPP stabilization in SOM-free geomaterial was comparable with that reported in the literature with soil containing SOM contents >1%. Results from this study suggest that the effectiveness of HRP-mediated stabilization of phenolic compounds not only depends on the cross-coupling with SOM, but also on the modification of the surface of the sorbent that can augment affinity with oligomers and enhance stabilization. Coverage of the mineral surface by phenolic oligomers may be analogous to SOM that can potentially sorb other xenobiotics. HRP- mediated reactions can be used to stabilize DCP associated with low SOM mineral soils or aquifer media, thereby restricting the transport of phenolic contaminants in the soil environment. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Immobilization of Polyoxometalates on Tailored Polymeric Surfaces.

PubMed

Aguado-Ureta, Saioa; Rodríguez-Hernández, Juan; Del Campo, Adolfo; Perez-Álvarez, Leyre; Ruiz-Rubio, Leire; Vilas, José Luis; Artetxe, Beñat; Reinoso, Santiago; Gutiérrez-Zorrilla, Juan M

2018-03-02

Herein we describe the preparation of hybrid polymer-inorganic interfaces by the immobilization of polyoxometalate nanoclusters on functionalized polymer surfaces. The polymeric surfaces were made of polystyrene- b -poly(acrylic acid)/polystyrene (PS- b -PAA/PS) blends by spin coating on a silicon wafer. The functionalization of the polymer film was obtained by interfacial migration of the amphiphilic block copolymer toward the interface upon water vapor annealing. The carboxylic acid functional groups contained in the PAA block were then employed to anchor the [Ln III (α-SiW 11 O 39 )] 5- polyoxometalates (Ln: Ce, Er). This purpose was achieved by immersing the films in aqueous solutions of the in situ-formed inorganic nanoclusters. X-ray photoelectron and confocal Raman spectroscopies, together with atomic force microscopy, confirmed the immobilization of the inorganic species at the interface.

Hydrogel brushes grafted from stainless steel via surface-initiated atom transfer radical polymerization for marine antifouling

NASA Astrophysics Data System (ADS)

Wang, Jingjing; Wei, Jun

2016-09-01

Crosslinked hydrogel brushes were grafted from stainless steel (SS) surfaces for marine antifouling. The brushes were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-methacryloyloxyethyl phosphorylcholine (MPC) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) respectively with different fractions of crosslinker in the feed. The grafted layers prepared with different thickness were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), ellipsometry and water contact angle measurements. With the increase in the fraction of crosslinker in the feed, the thickness of the grafted layer increased and the surface became smooth. All the brush-coated SS surfaces could effectively reduce the adhesion of bacteria and microalgae and settlement of barnacle cyprids, as compared to the pristine SS surface. The antifouling efficacy of the PEGMA polymer (PPEGMA)-grafted surface was higher than that of the MPC polymer (PMPC)-grafted surfaces. Furthermore, the crosslinked hydrogel brush-grafted surfaces exhibited better fouling resistance than the non-crosslinked polymer brush-grafted surfaces, and the antifouling efficacy increased with the crosslinking density. These hydrogel coatings of low toxicity and excellent anti-adhesive characteristics suggested their useful applications as environmentally friendly antifouling coatings.

Requirement of Sur2 for Efficient Replication of Mouse Adenovirus Type 1

PubMed Central

Fang, Lei; Stevens, Jennitte L.; Berk, Arnold J.; Spindler, Katherine R.

2004-01-01

Mouse adenovirus type 1 (MAV-1) early region 1A (E1A) encodes a virulence gene in viral infection of mice. To broaden our understanding of the functions of E1A in MAV-1 pathogenesis, an unbiased experimental approach, glutathione S-transferase (GST) pulldown, was used to screen for cellular proteins that interact with E1A protein. We identified mouse Sur2, a subunit of Mediator complex, as a protein that binds to MAV-1 E1A. The interaction between Sur2 and MAV-1 E1A was confirmed in virus-infected cells. Conserved region 3 (CR3) of MAV-1 E1A was mapped as the region required for Sur2-E1A interaction, as is the case for human adenovirus E1A. Although it has been proposed that human adenovirus E1A recruits the Mediator complex to transactivate transcription of viral early genes, Sur2 function in adenovirus replication has not been directly tested previously. Studies on the functions of Sur2 with mouse embryonic fibroblasts (MEFs) showed that there was a multiplicity-dependent growth defect of MAV-1 in Sur2−/− MEFs compared to Sur2+/+ MEFs. Comparison of the viral DNA and viral mRNA levels in Sur2+/+ and Sur2−/− MEFs confirmed that Sur2 was important for efficient viral replication. The viral replication defects in Sur2−/− MEFs appeared to be due at least in part to a defect in viral early gene transcription. PMID:15542641

Synthesis and Free Radical Polymerization of Fluorinated Polyhedral Oligomeric Silsesquioxane (F-POSS) Macromers: Precursors for Low Surface Energy Materials and Devices

DTIC Science & Technology

2012-10-01

Methylene Iodide Water Superhydrophobic /oleophilic dip-coated fabric Tuteja et al, Science, 2007, 318, 1618 Superamphiphobic electrospun surfaces...door for use a building block material for low surface energy materials • Applications – Mechanical robust superhydrophobic /oleophobic/omniphobic

Multifunctional Surface Modification of Nanodiamonds Based on Dopamine Polymerization.

PubMed

Zeng, Yun; Liu, Wenyan; Wang, Zheyu; Singamaneni, Srikanth; Wang, Risheng

2018-04-03

Surface functionalization of nanodiamonds (NDs), which is of great interest in advanced material and therapeutic applications, requires the immobilization of functional species, such as nucleic acids, bioprobes, drugs, and metal nanoparticles, onto NDs' surfaces to form stable nanoconjugates. However, it is still challenging to modify the surface of NDs due to the complexity of their surface chemistry and the low density of each functional group on the surfaces of NDs. In this work, we demonstrate a general applicable surface functionalization approach for the preparation of ND-based core-shell nanoconjugates using dopamine polymerization. By taking advantage of the universal adhesion and versatile reactivity of polydopamine, we have effectively conjugated DNA and silver nanoparticles onto NDs. Moreover, the catalytic activity of ND-supported silver nanoparticle was characterized by the reduction of 4-nitrophenol, and the addressability of NDs was tested through DNA hybridization that formed satellite ND-gold nanorod conjugation. This simple and robust method we have presented may significantly improve the capability for attaching various functionalities onto NDs and open up new platforms for applications of NDs.

The molecular basis of the specificity of action of KATP channel openers

PubMed Central

Moreau, Christophe; Jacquet, Hélène; Prost, Anne-Lise; D’hahan, Nathalie; Vivaudou, Michel

2000-01-01

KATP channels incorporate a regulatory subunit of the ATP-binding cassette (ABC) transporter family, the sulfonylurea receptor (SUR), which defines their pharmacology. The therapeutically important K+ channel openers (e.g. pinacidil, cromakalim, nicorandil) act specifically on the SUR2 muscle isoforms but, except for diazoxide, remain ineffective on the SUR1 neuronal/pancreatic isoform. This SUR1/2 dichotomy underpinned a chimeric strategy designed to identify the structural determinants of opener action, which led to a minimal set of two residues within the last transmembrane helix of SUR. Transfer of either residue from SUR2A to SUR1 conferred opener sensitivity to SUR1, while the reverse operation abolished SUR2A sensitivity. It is therefore likely that these residues form part of the site of interaction of openers with the channel. Thus, openers would target a region that, in other ABC transporters, is known to be tightly involved with the binding of substrates and other ligands. This first glimpse of the site of action of pharmacological openers should permit rapid progress towards understanding the structural determinants of their affinity and specificity. PMID:11118199

Soft Listeria: actin-based propulsion of liquid drops.

PubMed

Boukellal, Hakim; Campás, Otger; Joanny, Jean-François; Prost, Jacques; Sykes, Cécile

2004-06-01

We study the motion of oil drops propelled by actin polymerization in cell extracts. Drops deform and acquire a pearlike shape under the action of the elastic stresses exerted by the actin comet, a tail of cross-linked actin filaments. We solve this free boundary problem and calculate the drop shape taking into account the elasticity of the actin gel and the variation of the polymerization velocity with normal stress. The pressure balance on the liquid drop imposes a zero propulsive force if gradients in surface tension or internal pressure are not taken into account. Quantitative parameters of actin polymerization are obtained by fitting theory to experiment.

Development of self-assembled molecular structures on polymeric surfaces and their applications as ultrasonically responsive barrier coatings for on-demand, pulsatile drug delivery

NASA Astrophysics Data System (ADS)

Kwok, Connie Sau-Kuen

Nature in the form of DNA, proteins, and cells has the remarkable ability to interact with its environment by processing biological information through specific molecular recognition at the interface. As such, materials that are capable of triggering an appropriate biological response need to be engineered at the biomaterial surface. Chemically and structurally well-defined self-assembled monolayers (SAMs), biomimetics of the lipid bilayer in cell membranes, have been created and studied mostly on rigid metallic surfaces. This dissertation is motivated by the lack of methods to generate a molecularly designed surface for biomedical polymers and thus provides an enabling technology to engineer a polymeric surface precisely at a molecular and cellular level. To take this innovation one step further, we demonstrated that such self-assembled molecular structure coated on drug-containing polymeric devices could act as a stimulus-responsive barrier for controlled drug delivery. A simple, one-step procedure for generating ordered, crystalline methylene chains on polymeric surfaces via urethane linkages was successfully developed. The self-assemblies and molecular structures of these crystalline methylene chains are comparable to the SAM model surfaces, as evidenced by various surface characterization techniques (XPS, TOF-SIMS, and FTIR-ATR). For the first time, these self-assembled molecular structures are shown to function collectively as an ultrasound-responsive barrier membrane for pulsatile drug delivery, including delivery of low-molecular-weight ciprofloxacin and high-molecular-weight insulin. Encouraging results, based on the insulin-activated deoxyglucose uptakes in adipocytes, indicate that the released insulin remained biologically active. Both chemical and acoustic analyses suggest that the ultrasound-assisted release mechanism is primarily induced by transient cavitation, which causes temporary disruption of the self-assembled overlayer, and thus allows temporal release of the encapsulated drugs. In addition to acoustic energy, self-assembled surfaces experience order-disorder transition and have a transition temperature higher than body temperature if longer alkyl chains (C18) are used. The C18-assembled surface barrier membrane exhibits a relatively superior impermeable coating than the shorter C12 chains. The versatility of derivatizing the terminal groups of the self-assembled molecular structures is illustrated by attaching poly (ethyleneoxide) oligomers to the alkyl chains to minimize nonspecific protein adsorption. This study lays an important foundation for future work in conjugating other biomolecules to develop surface-based diagnostics and biomaterials. With much success, this original research work of forming self-assembled crystalline structures on synthetic materials still allows for numerous opportunities for new applications and possibly even more new discoveries.

Mesures experimentales de l'impact des revetements hydrophobeset superhydrophobes sur la trainee et la portance d'un profil aerodynamique propre et glace

NASA Astrophysics Data System (ADS)

Villeneuve, Eric

Ce projet, realise a la demande du Laboratoire International des Materiaux Antigivre, a pour but de mesurer et definir experimentalement l'impact de revetements hydrophobes sur les coefficients de trainee et de portance d'un profil NACA 0012. Pour ce faire, la balance aerodynamique du LIMA devait tout d'abord etre amelioree afin d'offrir une sensibilite suffisante pour realiser le projet. Plusieurs ameliorations ont ete faites, comme le changement des cellules de charge, la diminution du nombre de cellules de charge, le changement du cadre de la balance, etc. Une fois ces ameliorations terminees, la reproductibilite, l'exactitude et la sensibilite ont ete valides afin de s'assurer de la fiabilite des resultats offerts par la balance. Pour les angles d'attaque etudies avec les revetements, soient -6° et 0°, la balance a une reproductibilite de +/-2,06% a 360 000 de nombre de Reynolds. Pour valider la sensibilite, des essais a -6° et 0° d'angle d'attaque et des nombres de Reynolds de 360 000 et 500 000 ont ete faits avec des papiers sables. Les resultats de ces essais ont permis de, tracer des courbes de tendances du coefficient de trainee du NACA 0012 en fonction de la rugosite de surface et d'etablir la valeur de la sensibilite de la balance a +/-8 mu m. Cinq revetements populaires ont ete choisis pour l'experimentation, soient le Wearlon, le Staclean, le Hirec, le Phasebreak ainsi que le Nusil. Les revetements sont soumis aux memes conditions experimentales que les papiers sables, et une rugosite equivalente est trouvee par extrapolation des resultats. Cependant, les rugosites equivalentes de surfaces different entre -6° et 0°. Les essais avec le Staclean et le Hirec donnent des coefficients de trainee equivalent a ceux avec l'aluminium, alors que le Wearlon, le Nusil et le Phasebreak donnent une augmentation du coefficient de trainee de 13%, 17% et 25% respectivement par rapport a l'aluminium. Pour les coefficients de portance, la balance ne detecte pas l'effet des revetements, ni des papiers sables, sur la force de portance ce qui signifie qu'il entre dans l'insensibilite de la balance. La derniere etape experimentale consistait a mesurer l'impact des revetements sur la formation de la glace ainsi que sur l'evolution des coefficients de trainee et de portance du NACA 0012 en fonction de l'accumulation de glace sur celui-ci. Le Wearlon a ete choisi comme revetement en raison de sa grande popularite. Des essais a -5°C et -20°C ont ete faits et les resultats ont montres que le Wearlon n'apporte pas d'effet benefique au NACA 0012 en conditions d'accumulations de glace. L'augmentation du coefficient de trainee du profil muni du Wearlon debutait plus rapidement que sur l'aluminium et de l'eau gelait legerement plus loin vers l'arriere du profil pendant les essais, ce qui n'est pas souhaitable. Le coefficient de trainee est superieur d'environ 13% pour le Wearlon par rapport a l'aluminium pendant toute l'accumulation de glace, ce qui correspond au meme ecart lorsque la glace n'est pas en cause. Pour le coefficient de portance, les resultats ne peuvent etre utilises pour une raison qui doit etre investiguee.

Insulation Materials Comprising Fibers Having a Partially Cured Polymer Coating Thereon, Articles Including Such Insulation Materials, and Methods of Forming Such Materials and Articles

NASA Technical Reports Server (NTRS)

Morgan, Richard E. (Inventor); Meeks, Craig L. (Inventor)

2017-01-01

Insulation materials have a coating of a partially cured polymer on a plurality of fibers, and the plurality of coated fibers in a cross-linked polymeric matrix. Insulation may be formed by applying a preceramic polymer to a plurality of fibers, heating the preceramic polymer to form a partially cured polymer over at least portions of the plurality of fibers, disposing the plurality of fibers in a polymeric material, and curing the polymeric material. A rocket motor may be formed by disposing a plurality of coated fibers in an insulation precursor, curing the insulation precursor to form an insulation material without sintering the partially cured polymer, and providing an energetic material over the polymeric material. An article includes an insulation material over at least one surface.

Polymerization-based signal amplification under ambient conditions with thirty-five second reaction times.

PubMed

Kaastrup, Kaja; Sikes, Hadley D

2012-10-21

Although polymerization-based amplification (PBA) has demonstrated promise as an inexpensive technique for use in molecular diagnostics, oxygen inhibition of radical photopolymerization has hindered its implementation in point-of-care devices. The addition of 0.3-0.7 μM eosin to an aqueous acrylate monomer solution containing a tertiary amine allows an interfacial polymerization reaction to proceed in air only near regions of a test surface where additional eosin initiators coupled to proteins have been localized as a function of molecular recognition events. The dose of light required for the reaction is inversely related to eosin concentration. This system achieves sensitivities comparable to those reported for inert gas-purged systems and requires significantly shorter reaction times. We provide several comparisons of this system with other implementations of polymerization-based amplification.

Modification of polymeric surface for improved adhesion via electron beam exposure

DOEpatents

Kelber, Jeffry A.

1989-01-01

Treating polymer surfaces, e.g., Teflon, particularly very thin surfaces, e.g., 50-10,000 .ANG. with low energy electron radiation, e.g., 100-1000 eV, in a high vacuum environment, e.g., less than 10.sup.-6 Torr, to enhance the ability of the surface to be adhered to a variety of substrates.

Preparation and controlled drug delivery applications of mesoporous silica polymer nanocomposites through the visible light induced surface-initiated ATRP

NASA Astrophysics Data System (ADS)

Huang, Long; Liu, Meiying; Mao, Liucheng; Xu, Dazhuang; Wan, Qing; Zeng, Guangjian; Shi, Yingge; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

2017-08-01

The mesoporous materials with large pore size, high specific surface area and high thermal stability have been widely utilized in a variety of fields ranging from environmental remediation to separation and biomedicine. However, surface modification of these silica nanomaterials is required to endow novel properties and achieve better performance for most of these applications. In this work, a new method has been established for surface modification of mesoporous silica nanoparticles (MSNs) that relied on the visible light induced atom transfer radical polymerization (ATRP). In the procedure, the copolymers composited with itaconic acid (IA) and poly(ethylene glycol)methyl acrylate (PEGMA) were grafted from MSNs using IA and PEGMA as the monomers and 10-Phenylphenothiazine(PTH) as the organic catalyst. The successful preparation of final polymer nanocomposites (named as MSNs-NH2-poly(IA-co-PEGMA)) were evidenced by a series of characterization techniques. More importantly, the anticancer agent cisplatin can be effectively loaded on MSNs-NH2-poly(IA-co-PEGMA) and controlled release it from the drug-loading composites with pH responsive behavior. As compared with conventional ATRP, the light induced surface-initiated ATRP could also be utilized for preparation of various silica polymer nanocomposites under rather benign conditions (e.g. absent of transition metal ions, low polymerization temperature and short polymerization time). Taken together, we have developed a rather promising strategy method for fabrication of multifunctional MSNs-NH2-poly(IA-co-PEGMA) with great potential for biomedical applications.

Fabrication of superhydrophobic cotton fabrics using crosslinking polymerization method

NASA Astrophysics Data System (ADS)

Jiang, Bin; Chen, Zhenxing; Sun, Yongli; Yang, Huawei; Zhang, Hongjie; Dou, Haozhen; Zhang, Luhong

2018-05-01

With the aim of removing and recycling oil and organic solvent from water, a facile and low-cost crosslinking polymerization method was first applied on surface modification of cotton fabrics for water/oil separation. Micro-nano hierarchical rough structure was constructed by triethylenetetramine (TETA) and trimesoyl chloride (TMC) that formed a polymeric layer on the surface of the fabric and anchored Al2O3 nanoparticles firmly between the fabric surface and the polymer layer. Superhydrophobic property was further obtained through self-assembly grafting of hydrophobic groups on the rough surface. The as-prepared cotton fabric exhibited superoleophilicity in atmosphere and superhydrophobicity both in atmosphere and under oil with the water contact angle of 153° and 152° respectively. Water/oil separation test showed that the as-prepared cotton fabric can handle with various oil-water mixtures with a high separation efficiency over 99%. More importantly, the separation efficiency remained above 98% over 20 cycles of reusing without losing its superhydrophobicity which demonstrated excellent reusability in oil/water separation process. Moreover, the as-prepared cotton fabric possessed good contamination resistance ability and self-cleaning property. Simulation washing process test showed the superhydrophobic cotton fabric maintained high value of water contact angle above 150° after 100 times washing, indicating great stability and durability. In summary, this work provides a brand-new way to surface modification of cotton fabric and makes it a promising candidate material for oil/water separation.

Binary breath figures for straightforward and controllable self-assembly of microspherical caps.

PubMed

Gong, Jianliang; Xu, Bingang; Tao, Xiaoming; Li, Lei

2016-05-11

The intense interest surrounding asymmetrical microparticles originates from their unique anisotropic properties and promising applications. In this work, direct self-assembly of polymeric microspherical caps without the assistance of any additives has been achieved by using low-surface-tension methanol (MeOH) and high-surface-tension water as binary breath figures (BFs). With the evaporation of polystyrene (PS) solution containing low-boiling-point solvent in the binary vapors, the formed MeOH BFs could quickly diffuse into solution, while water BFs tended to remain at the solution surface. This led to the formation of a gradient nonsolvent layer at the vapor/solution interface, which induced the formation of nuclei and guided further asymmetrical growth of polymer particles. After the spontaneous removal of MeOH, water and residual solvent by evaporation, polymeric microspherical caps were left on the substrate. Through controlling the proportion of water introduced by adjusting the ratios of MeOH and water, polymeric microspherical caps with a range of controllable shapes (divided at different positions of a sphere) were successfully obtained. The formation mechanism was explained based on the difference of vapor pressure, surface tension and miscibility between the employed solvents and nonsolvents. A solvent possessing a high vapor pressure, low surface tension and good miscibility with MeOH contributed to the formation of microspherical caps. This flexible, green and straightforward technique is a nondestructive strategy, and avoids complicated work on design, preparation and removal of hard templates and additives.

Preparation of polystyrene brush film by radical chain-transfer polymerization and micromechanical properties

NASA Astrophysics Data System (ADS)

Zhao, Jing; Chen, Miao; An, Yanqing; Liu, Jianxi; Yan, Fengyuan

2008-12-01

A radical chain-transfer polymerization technique has been applied to graft-polymerize brushes of polystyrene (PSt) on single-crystal silicon substrates. 3-Mercapto-propyltrimethoxysilane (MPTMS), as a chain-transfer agent for grafting, was immobilized on the silicon surface by a self-assembling process. The structure and morphology of the graft-functionalized silicon surfaces were characterized by the means of contact-angle measurement, ellipsometric thickness measurement, Fourier transformation infrared (FTIR) spectroscopy, and atomic force microscopy (AFM). The nanotribological and micromechanical properties of the as-prepared polymer brush films were investigated by frictional force microscopy (FFM), force-volume analysis and scratch test. The results indicate that the friction properties of the grafted polymer films can be improved significantly by the treatment of toluene, and the chemically bonded polystyrene film exhibits superior scratch resistance behavior compared with the spin-coated polystyrene film. The resultant polystyrene brush film is expected to develop as a potential lubrication coating for microelectromechanical systems (MEMS).

Stimuli Responsive Morphological Changes of Pnipa Polymer Brushes Synthesized on Silicon Substrate

NASA Astrophysics Data System (ADS)

Huda, Muhammad Nurul; Kabir, A. N. M. Hamidul

2013-08-01

High-density polymer brushes were grown from the silicon surface by atom transfer radical polymerization of Poly(N-isopropylacrylamide) (PNIPA) at different polymerization conditions. PNIPA brushes were prepared using Copper (I) Chloride/tris(2-(dimetylamino)ethyl)amine (Me6TREN) as a catalytic system in DMSO at 20°C. Free polymer formed during the brush formation was characterized by gel permeation chromatography. The grafting densities up to 0.52 chains/nm2 were obtained. The layer thickness of polymer brush increases with the increase of conversion of the monomer conversion as well as polymerization time. Atomic force microscopy and air bubble contact angle under pH solution were employed to study the surface morphology, reversible conformational changes of and stimulus-response behavior. PNIPA brushes exhibited a different nanomorphology after treatment with different pH solution. It also revealed a unique reversible wetting behavior with pH. The reversible properties of the PNIPA brushes can be used to regulate the adsorption of the sulfonated PS nanoparticles.

Nanospheres Encapsulating Anti-Leishmanial Drugs for Their Specific Macrophage Targeting, Reduced Toxicity, and Deliberate Intracellular Release

PubMed Central

Shukla, Anil Kumar; Patra, Sanjukta

2012-01-01

Abstract The current work focuses on the study of polymeric, biodegradable nanoparticles (NPs) for the encapsulation of doxorubicin and mitomycin C (anti-leishmanial drugs), and their efficient delivery to macrophages, the parasite's home. The biodegradable polymer methoxypoly-(ethylene glycol)-b-poly (lactic acid) (MPEG-PLA) was used to prepare polymeric NPs encapsulating doxorubicin and mitomycin C. The morphology, mean diameter, and surface area of spherical NPs were determined by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and BET surface area analysis. X-ray diffraction was performed to validate drug encapsulation. An in vitro release profile of the drugs suggested a fairly slow release. These polymeric NPs were efficiently capable of releasing drug inside macrophages at a slower pace than the free drug, which was monitored by epi-fluorescence microscopy. Encapsulation of doxorubicin and mitomycin C into NPs also decreases cellular toxicity in mouse macrophages (J774.1A). PMID:22925019

Efficient Functionalization of Polyethylene Fibers for the Uranium Extraction from Seawater through Atom Transfer Radical Polymerization

DOE PAGES

Neti, Venkata S.; Das, Sadananda; Brown, Suree; ...

2017-08-29

Brush-on-brush structures are proposed as one method to overcome support effects in grafted polymers. Utilizing glycidyl methacrylate (GMA) grafted on polyethylene (PE) fibers using radiation-induced graft polymerization (RIGP) provides a hydrophilic surface on the hydrophobic PE. When integrated with atom transfer radical polymerization (ATRP), the grafting of acrylonitrile (AN) and hydroxyethyl acrylate (HEA) can be controlled and manipulated more easily than with RIGP. Poly(acrylonitrile)-co-poly(hydroxyethyl acrylate) chains were grown via ATRP on PE-GMA fibers to generate an adsorbent for the extraction of uranium from seawater. The prepared adsorbents in this study demonstrated promise (159.9 g-U/kg of adsorbent) in laboratory screening testsmore » using a high uranium concentration brine and 1.24 g-U/Kg of adsorbent in the filtered natural seawater in 21-days. Here, the modest capacity in 21-days exceeds previous efforts to generate brush-on-brush adsorbents by ATRP while manipulating the apparent surface hydrophilicity of the trunk material (PE).« less

Facile fabrication of superhydrophobic flower-like polyaniline architectures by using valine as a dopant in polymerization

NASA Astrophysics Data System (ADS)

Sun, Jun; Bi, Hong

2012-03-01

A facile method was developed to fabricate superhydrophobic, flower-like polyanline (PANI) architectures with hierarchical nanostructures by adding valine in polymerization as a dopant. The water contact angle of the prepared PANI film was measured to be 155.3°, and the hydrophobic surface of the PANI architectures can be tuned easily by varying the polymerization time as well as valine doping quantity. It is believed that valine plays an important role in not only growth of the hierarchical PANI structures but also formation of the superhydrophobic surface, for it provides functional groups such as sbnd COOH, sbnd NH2 and a hydrophobic terminal group which may further increase intra-/inter-molecular interactions including hydrogen bonding, π-π stacking and hydrophobic properties. Similar flower-like PANI architectures have been prepared successfully by employing other amino acids such as threonine, proline and arginine. This method makes it possible for widespread applications of superhydrophobic PANI film due to its simplicity and practicability.

Efficient Functionalization of Polyethylene Fibers for the Uranium Extraction from Seawater through Atom Transfer Radical Polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neti, Venkata S.; Das, Sadananda; Brown, Suree

Brush-on-brush structures are proposed as one method to overcome support effects in grafted polymers. Utilizing glycidyl methacrylate (GMA) grafted on polyethylene (PE) fibers using radiation-induced graft polymerization (RIGP) provides a hydrophilic surface on the hydrophobic PE. When integrated with atom transfer radical polymerization (ATRP), the grafting of acrylonitrile (AN) and hydroxyethyl acrylate (HEA) can be controlled and manipulated more easily than with RIGP. Poly(acrylonitrile)-co-poly(hydroxyethyl acrylate) chains were grown via ATRP on PE-GMA fibers to generate an adsorbent for the extraction of uranium from seawater. The prepared adsorbents in this study demonstrated promise (159.9 g-U/kg of adsorbent) in laboratory screening testsmore » using a high uranium concentration brine and 1.24 g-U/Kg of adsorbent in the filtered natural seawater in 21-days. Here, the modest capacity in 21-days exceeds previous efforts to generate brush-on-brush adsorbents by ATRP while manipulating the apparent surface hydrophilicity of the trunk material (PE).« less

Efficient Functionalization of Polyethylene Fibers for the Uranium Extraction from Seawater through Atom Transfer Radical Polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neti, Venkata S.; Das, Sadananda; Brown, Suree

Brush-on-brush structures are proposed as one method to overcome support effects in grafted polymers. Utilizing glycidyl methacrylate (GMA) grafted on polyethylene (PE) fibers using radiation-induced graft polymerization (RIGP) provides a hydrophilic surface on the hydrophobic PE. When integrated with atom transfer radical polymerization (ATRP), the grafting of acrylonitrile (AN) and hydroxyethyl acrylate (HEA) can be controlled and manipulated more easily than with RIGP. Poly(acrylonitrile)-co-poly(hydroxyethyl acrylate) chains were grown via ATRP on PE-GMA fibers to generate an adsorbent for the extraction of uranium from seawater. The prepared adsorbents in this study demonstrated promise (159.9 g- U/kg of adsorbent) in laboratory screeningmore » tests using a high uranium concentration brine and 1.24 g-U/Kg of adsorbent in the filtered natural seawater in 21-days. The modest capacity in 21- days exceeds previous efforts to generate brush-on-brush adsorbents by ATRP while manipulating the apparent surface hydrophilicity of the trunk material (PE).« less

Cell membrane-inspired polymeric micelles as carriers for drug delivery.

PubMed

Liu, Gongyan; Luo, Quanqing; Gao, Haiqi; Chen, Yuan; Wei, Xing; Dai, Hong; Zhang, Zongcai; Ji, Jian

2015-03-01

In cancer therapy, surface engineering of drug delivery systems plays an essential role in their colloidal stability, biocompatibility and prolonged blood circulation. Inspired by the cell membrane consisting of phospholipids and glycolipids, a zwitterionic phosphorylcholine functionalized chitosan oligosaccharide (PC-CSO) was first synthesized to mimic the hydrophilic head groups of those amphipathic lipids. Then hydrophobic stearic acid (SA) similar to lipid fatty acids was grafted onto PC-CSO to form amphiphilic PC-CSO-SA copolymers. Cell membrane-mimetic micelles with a zwitterionic surface and a hydrophobic SA core were prepared by the self-assembly of PC-CSO-SA copolymers, showing excellent stability under extreme conditions including protein containing media, high salt content or a wide pH range. Doxorubicin (DOX) was successfully entrapped into polymeric micelles through the hydrophobic interaction between DOX and SA segments. After fast internalization by cancer cells, sustained drug release from micelles to the cytoplasm and nucleus was achieved. This result suggests that these biomimetic polymeric micelles may be promising drug delivery systems in cancer therapy.

The chocolate-egg problem: Fabrication of thin elastic shells through coating

NASA Astrophysics Data System (ADS)

Lee, Anna; Marthelot, Joel; Brun, Pierre-Thomas; Reis, Pedro M.

2015-03-01

We study the fabrication of thin polymeric shells based on the coating of a curved surface by a viscous fluid. Upon polymerization of the resulting thin film, a slender solid structure is delivered after demolding. This technique is extensively used, empirically, in manufacturing, where it is known as rotational molding, as well as in the food industry, e.g. for chocolate-eggs. This problem is analogous to the Landau-Levich-Derjaguin coating of plates and fibers and Bretherton's problem of film deposition in cylindrical channels, albeit now on a double-curved geometry. Here, the balance between gravity, viscosity, surface tension and polymerization rate can yield a constant thickness film. We seek to identify the physical ingredients that govern the final film thickness and its profile. In our experiments using organosilicon, we systematically vary the properties of the fluid, as well as the curvature of the substrate onto which the film is coated, and characterize the final thickness profile of the shells. A reduced model is developed to rationalize the process.

Kinetic and Mechanistic Study of Vapor-Phase Free Radical Polymerization onto Liquid Surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Malancha

The primary objective of this proposal was to study vapor deposition of polymers onto liquid surfaces. Deposition onto liquid surfaces is a relatively new area of research because the past few decades have focused on deposition onto solid materials. We used initiated chemical vapor deposition to deposit polymers onto the liquid surfaces. The process is a one-step, solventless, free-radical polymerization process in which monomer and initiator molecules are flowed into a vacuum chamber. We found that the surface tension interaction between the polymer and the liquid determines whether a film or nanoparticles are formed. We also found that we couldmore » form gels by using soluble monomers. We found that we could tune the size of the nanoparticles by varying the viscosity of the liquid and the process parameters including pressure and time. These insights allow scalable synthesis of polymer materials for a variety of separation and catalysis applications.« less

Amine-Rich Organic Thin Films for Cell Culture: Possible Electrostatic Effects in Cell-Surface Interactions

NASA Astrophysics Data System (ADS)

Wertheimer, Michael R.; St-Georges-Robillard, Amélie; Lerouge, Sophie; Mwale, Fackson; Elkin, Bentsian; Oehr, Christian; Wirges, Werner; Gerhard, Reimund

2012-11-01

In recent communications from these laboratories, we observed that amine-rich thin organic layers are very efficient surfaces for the adhesion of mammalian cells. We prepare such deposits by plasma polymerization at low pressure, atmospheric pressure, or by vacuum-ultraviolet photo-polymerization. More recently, we have also investigated a commercially available material, Parylene diX AM. In this article we first briefly introduce literature relating to electrostatic interactions between cells, proteins, and charged surfaces. We then present certain selected cell-response results that pertain to applications in orthopedic and cardiovascular medicine: we discuss the influence of surface properties on the observed behaviors of two particular cell lines, human U937 monocytes, and Chinese hamster ovary cells. Particular emphasis is placed on possible electrostatic attractive forces due to positively charged R-NH3+ groups and negatively charged proteins and cells, respectively. Experiments carried out with electrets, polymers with high positive or negative surface potentials are added for comparison.

Polymerization of Fluoroalkyl Polyhedral Oligomeric Silsesquioxane (F-POSS) Macromers

DTIC Science & Technology

2012-12-01

mm Methanol Octane Methylene Iodide Water Superhydrophobic /oleophilic dip-coated fabric Tuteja et al, Science, 2007, 318, 1618 Superamphiphobic...robust superhydrophobic /oleophobic/omniphobic surfaces • Via covalently attached F-POSS to substrate (surface, nanoparticle, polymer matrix) – Effects

Hybrid assemblies of ATP-sensitive K+ channels determine their muscle-type-dependent biophysical and pharmacological properties.

PubMed

Tricarico, Domenico; Mele, Antonietta; Lundquist, Andrew L; Desai, Reshma R; George, Alfred L; Conte Camerino, Diana

2006-01-24

ATP-sensitive K(+) channels (K(ATP)) are an octameric complex of inwardly rectifying K(+) channels (Kir6.1 and Kir6.2) and sulfonylurea receptors (SUR1 and SUR2A/B), which are involved in several diseases. The tissue-selective expression of the subunits leads to different channels; however, the composition and role of the functional channel in native muscle fibers is not known. In this article, the properties of K(ATP) channels of fast-twitch and slow-twitch muscles were compared by combining patch-clamp experiments with measurements of gene expression. We found that the density of K(ATP) currents/area was muscle-type specific, being higher in fast-twitch muscles compared with the slow-twitch muscle. The density of K(ATP) currents/area was correlated with the level of Kir6.2 expression. SUR2A was the most abundant subunit expressed in all muscles, whereas the vascular SUR2B subunit was expressed but at lower levels. A significant expression of the pancreatic SUR1 was also found in fast-twitch muscles. Pharmacological experiments showed that the channel response to the SUR1 agonist diazoxide, SUR2A/B agonist cromakalim, SUR1 antagonist tolbutamide, and the SUR1/SUR2A/B-antagonist glibenclamide matched the SURs expression pattern. Muscle-specific K(ATP) subunit compositions contribute to the physiological performance of different muscle fiber types and determine the pharmacological actions of drugs modulating K(ATP) activity in muscle diseases.

Polymeric Coatings that Mimic the Endothelium: Combining Nitric Oxide Release with Surface-Bound Active Thrombomodulin and Heparin

PubMed Central

Wu, Biyun; Gerlitz, Bruce; Grinnell, Brian W.; Meyerhoff, Mark E.

2007-01-01

Multi-functional bilayer polymeric coatings are prepared with both controlled nitric oxide (NO) release and surface-bound active thrombomodulin (TM) alone or in combination with immobilized heparin. The outer-layer is made of CarboSil, a commercially available copolymer of silicone rubber (SR) and polyurethane (PU). The CarboSil is either carboxylated or aminated via an allophanate reaction with a diisocyanate compound followed by a urea-forming reaction between the generated isocyanate group of the polymer and the amine group of an amino acid (glycine), an oligopeptide (triglycine) or a diamine. The carboxylated CarboSil can then be used to immobilize TM through the formation of an amide bond between the surface carboxylic acid groups and the lysine residues of TM. Aminated CarboSil can also be employed to initially couple heparin to the surface, and then the carboxylic acid groups on heparin can be further used to anchor TM. Both surface-bound TM and heparin’s activity are evaluated by chromogenic assays and found to be at clinically significant levels. The underlying NO release layer is made with another commercial SR-PU copolymer (PurSil) mixed with a lipophilic NO donor (N-diazeniumdiolated dibutylhexanediamine (DBHD/N2O2)). The NO release rate can be tuned by changing the thickness of top coatings, and the duration of NO release at physiologically relevant levels can be as long as 2 weeks. The combination of controlled NO release as well as immobilized active TM and heparin from/on the same polymeric surface mimics the highly thromboresistant endothelium layer. Hence, such multifunctional polymer coatings should provide more blood-compatible surfaces for biomedical devices. PMID:17597201

Importance of Extracellular Polymeric Substances from Thiobacillus ferrooxidans for Bioleaching

PubMed Central

Gehrke, Tilman; Telegdi, Judit; Thierry, Dominique; Sand, Wolfgang

1998-01-01

Leaching bacteria such as Thiobacillus ferrooxidans attach to pyrite or sulfur by means of extracellular polymeric substances (EPS) (lipopolysaccharides). The primary attachment to pyrite at pH 2 is mediated by exopolymer-complexed iron(III) ions in an electrochemical interaction with the negatively charged pyrite surface. EPS from sulfur cells possess increased hydrophobic properties and do not attach to pyrite, indicating adaptability to the substrate or substratum. PMID:9647862

Role of Co-Vapors in Vapor Deposition Polymerization

PubMed Central

Lee, Ji Eun; Lee, Younghee; Ahn, Ki-Jin; Huh, Jinyoung; Shim, Hyeon Woo; Sampath, Gayathri; Im, Won Bin; Huh, Yang–Il; Yoon, Hyeonseok

2015-01-01

Polypyrrole (PPy)/cellulose (PPCL) composite papers were fabricated by vapor phase polymerization. Importantly, the vapor-phase deposition of PPy onto cellulose was assisted by employing different co-vapors namely methanol, ethanol, benzene, water, toluene and hexane, in addition to pyrrole. The resulting PPCL papers possessed high mechanical flexibility, large surface-to-volume ratio, and good redox properties. Their main properties were highly influenced by the nature of the co-vaporized solvent. The morphology and oxidation level of deposited PPy were tuned by employing co-vapors during the polymerization, which in turn led to change in the electrochemical properties of the PPCL papers. When methanol and ethanol were used as co-vapors, the conductivities of PPCL papers were found to have improved five times, which was likely due to the enhanced orientation of PPy chain by the polar co-vapors with high dipole moment. The specific capacitance of PPCL papers obtained using benzene, toluene, water and hexane co-vapors was higher than those of the others, which is attributed to the enlarged effective surface area of the electrode material. The results indicate that the judicious choice and combination of co-vapors in vapor-deposition polymerization (VDP) offers the possibility of tuning the morphological, electrical, and electrochemical properties of deposited conducting polymers. PMID:25673422

Deducing multiple interfacial dynamics during polymeric foaming.

PubMed

Chandan, Mohammed Rehaan; Naskar, Nilanjon; Das, Anuja; Mukherjee, Rabibrata; Harikrishnan, Gopalakrishna Pillai

2018-06-15

Several interfacial phenomena are active during polymeric foaming, the dynamics of which significantly influence terminal stability, cell structure and in turn the thermo-mechanical properties of temporally evolved foam. Understanding these dynamics is important in achieving desired foam properties. Here, we introduce a method to simultaneously portray the time evolution of bubble growth, lamella thinning and Plateau border drainage, occurring during reactive polymeric foaming. In this method, we initially conduct bulk and surface shear rheology under polymerizing and non-foaming conditions. In a subsequent step, foaming experiments were conducted in a rheometer. The microscopic structural dimensions pertaining to the terminal values of the dynamics of each interfacial phenomena are then measured using a combination of scanning electron microscopy, optical microscopy and imaging ellipsometry, after the foaming is over. The measured surface and bulk rheological parameters are incorporated in time evolution equations that are derived from mass and momentum transport occurring when a model viscoelastic fluid is foamed by gas dispersion. Analytical and numerical solutions to these equations portray the dynamics. We demonstrate this method for a series of reactive polyurethane foams generated from different chemical sources. The effectiveness of our method is in simultaneously obtaining these dynamics that are difficult to directly monitor due to short active durations over multiple length scales.

Effect of surface treatments on shear bond strength of denture teeth to denture base resins

PubMed Central

Bahrani, Farideh; Khaledi, Amir Ali Reza

2014-01-01

Background: Debonding of denture teeth from denture bases is the most common failure in removable dentures. The purpose of this study was to evaluate the effect of surface treatments on shear bond strength of denture teeth to heat-polymerized and autopolymerized denture base resins. Materials and Methods: In this experimental in vitro study, 60 maxillary central incisor acrylic teeth were divided into two groups. Group M was polymerized with heat-polymerized acrylic resin (Meliodent) by compression molding technique and group F was processed by autopolymerized acrylic resin (Futura Gen) by injection molding technique. Within each group, specimens were divided into three subgroups according to the teeth surface treatments (n = 10): (1) ground surface as the control group (M1 and F1), (2) ground surface combined with monomer application (M2 and F2), and (3) airborne particle abrasion by 50 μm Al2O3 (M3 and F3). The shear bond strengths of the specimens were tested by universal testing machine with crosshead speed of 5 mm/min. Data were analyzed by two-way analysis of variance (ANOVA) and Tukey's honestly significant difference (HSD) tests (P < 0.05). Results: The mean shear bond strengths of the studied groups were 96.40 ± 14.01, 124.70 ± 15.64, and 118 ± 16.38 N for M1, M2, and M3 and 87.90 ± 13.48, 117 ± 13.88, and 109.70 ± 13.78 N for F1, F2, and F3, respectively. The surface treatment of the denture teeth significantly affected their shear bond strengths to the both the denture base resins (P < 0.001). However, there were no significant differences between the groups treated by monomer or airborne particle abrasion (P = 0.29). The highest percentage of failure mode was mixed in Meliodent and adhesive in Futura Gen. Conclusion: Monomer application and airborne particle abrasion of the ridge lap area of the denture teeth improved their shear bond strengths to the denture base resins regardless of the type of polymerization. PMID:24688570

ATP-sensitive potassium currents from channels formed by Kir6 and a modified cardiac mitochondrial SUR2 variant

PubMed Central

Aggarwal, Nitin T; Shi, Nian-Qing; Makielski, Jonathan C

2013-01-01

Cardiac ATP-sensitive potassium channels (KATP) are found in both the sarcoplasmic reticulum (sarcKATP) and the inner membrane of mitochondria (mitoKATP). SarcKATP are composed of a pore containing subunit Kir6.2 and a regulatory sulfonylurea receptor subunit (SUR2), but the composition of mitoKATP remains unclear. An unusual intra-exonic splice variant of SUR2 (SUR2A-55) was previously identified in mitochondria of mammalian heart and brain, and by analogy with sarcKATP we proposed SUR2A-55 as a candidate regulatory subunit of mitoKATP. Although SUR2A-55 lacks the first nucleotide binding domain (NBD) and 2 transmembrane domains (TMD), it has a hybrid TMD and retains the second NBD. It resembles a hemi-ABC transporter suggesting it could multimerize to function as a regulatory subunit. A putative mitochondrial targeting signal in the N-terminal domain of SUR2A-55 was removed by truncation and when co-expressed with Kir6.1 and Kir6.2 it targeted to the plasma membrane and yielded KATP currents. Single channel conductance, mean open time, and burst open time of SUR2A-55 based KATP was similar to the full-length SUR2A based KATP. However, the SUR2A-55 KATP were 70-fold less sensitive to block by ATP, and twice as resistant to intracellular Ca2+ inhibition compared with the SUR2A KATP, and were markedly insensitive to KATP drugs, pinacidil, diazoxide, and glybenclamide. These results suggest that the SUR2A-55 based channels would tend to be open under physiological conditions and in ischemia, and could account for cardiac and mitochondrial phenotypes protective for ischemia. PMID:24037327

Metal-Free Photoinduced Electron Transfer-Atom Transfer Radical Polymerization Integrated with Bioinspired Polydopamine Chemistry as a Green Strategy for Surface Engineering of Magnetic Nanoparticles.

PubMed

Yang, Yang; Liu, Xuegang; Ye, Gang; Zhu, Shan; Wang, Zhe; Huo, Xiaomei; Matyjaszewski, Krzysztof; Lu, Yuexiang; Chen, Jing

2017-04-19

Developing green and efficient technologies for surface modification of magnetic nanoparticles (MNPs) is of crucial importance for their biomedical and environmental applications. This study reports, for the first time, a novel strategy by integrating metal-free photoinduced electron transfer-atom transfer radical polymerization (PET-ATRP) with the bioinspired polydopamine (PDA) chemistry for controlled architecture of functional polymer brushes from MNPs. Conformal PDA encapsulation layers were initially generated on the surfaces of MNPs, which served as the protective shells while providing an ideal platform for tethering 2-bromo-2-phenylacetic acid (BPA), a highly efficient initiator. Metal-free PET-ATRP technique was then employed for controlled architecture of poly(glycidyl methacrylate) (PGMA) brushes from the core-shell MNPs by using diverse organic dyes as photoredox catalysts. Impacts of light sources (including UV and visible lights), photoredox catalysts, and polymerization time on the composition and morphology of the PGMA brushes were investigated. Moreover, the versatility of the PGMA-functionalized core-shell MNPs was demonstrated by covalent attachment of ethylenediamine (EDA), a model functional molecule, which afforded the MNPs with improved hydrophilicity, dispersibility, and superior binding ability to uranyl ions. The green methodology by integrating metal-free PET-ATRP with facile PDA chemistry would provide better opportunities for surface modification of MNPs and miscellaneous nanomaterials for biomedical and electronic applications.

Absorption of polycyclic aromatic hydrocarbons by a highly absorptive polymeric medium.

PubMed

Francisco, Olga; Idowu, Ifeoluwa; Friesen, Kelsey L; McDougall, Matthew; Choi, Sara Seoin; Bolluch, Patrique; Daramola, Oluwadamilola; Johnson, Wesley; Palace, Vince; Stetefeld, Jörg; Tomy, Gregg T

2018-06-01

The efficacy of a lightly cross-linked polymeric bead to absorb polycyclic aromatic hydrocarbons (PAHs) from the surface of fresh- and salt-water in a simulated oil-spill scenario was assessed in this study. A layer of PAHs at the water surface was created by first preparing the PAHs in hexane and then carefully spiking this mixture onto the surface of water. Beads were then applied to the surface of the organic phase and the amount of hydrocarbons absorbed by the beads was examined at prescribed time intervals and at different temperatures. Absorption of PAHs into the beads was exhaustive with ∼86 ± 4% being selectively removed from the organic phase by 120 s. First order reaction rates best described the uptake kinetics and absorption rates ranged from 0.0085 (naphthalene) to 0.0325 s- 1 (dibenzo[a,h]anthracene). Absorption of PAHs into the beads was driven by molecular volume (A 3 ). Uptake rates increased markedly for PAHs with molecular volumes between 130 A 3 and 190 A 3 . Beyond this molecular volume there was no apparent change in the rate of uptake. This study shows that these polymeric beads have a high affinity for PAHs and can be used under various environmental conditions with negligible difference in absorptive efficacy. Copyright © 2018 Elsevier Ltd. All rights reserved.

Surface and anti-fouling properties of a polyampholyte hydrogel grafted onto a polyethersulfone membrane.

PubMed

Zhang, Wei; Yang, Zhe; Kaufman, Yair; Bernstein, Roy

2018-05-01

Zwitterion polymers have anti-fouling properties; therefore, grafting new zwitterions to surfaces, particularly as hydrogels, is one of the leading research directions for preventing fouling. Specifically, polyampholytes, polymers of random mixed charged subunits with a net-electric charge, offer a synthetically easy alternative for studying new zwitterions with a broad spectrum of charged moieties. Here, a novel polyampholyte hydrogel was grafted onto the surface of polyethersulfone membrane by copolymerizing a mixture of vinylsulfonic acid (VSA) and [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METMAC) as the negatively and positively charged monomers, respectively, using various monomer ratios in the polymerization solution, and with N,N'-methylenebisacrylamide as the crosslinker. The physicochemical, morphological and anti-fouling properties of the modified membranes were systematically investigated. Hydrophilic hydrogels were successfully grafted using monomers at different molar ratios. A thin-film zwitterion hydrogel (∼90 nm) was achieved at a 3:1 [VSA:METMAC] molar ratio in the polymerization solution. Among all examined membranes, the zwitterion polyampholyte-modified membrane demonstrated the lowest adsorption of proteins, humic acid, and sodium alginate. It also had low fouling and high flux recovery following filtration with a protein or with an extracellular polymeric substance solution. These findings suggest that this polyampholyte hydrogel is applicable as a low fouling surface coating. Copyright © 2018 Elsevier Inc. All rights reserved.

DH and ESPI laser interferometry applied to the restoration shrinkage assessment

NASA Astrophysics Data System (ADS)

Campos, L. M. P.; Parra, D. F.; Vasconcelos, M. R.; Vaz, M.; Monteiro, J.

2014-01-01

In dental restoration postoperative marginal leakage is commonly associated to polymerization shrinkage effects. In consequence the longevity and quality of restorative treatment depends on the shrinkage mechanisms of the composite filling during the polymerization. In this work the development of new techniques for evaluation of those effects under light-induced polymerization of dental nano composite fillings is reported. The composite resins activated by visible light, initiate the polymerization process by absorbing light in wavelengths at about 470 nm. The techniques employed in the contraction assessment were digital holography (DH) and Electronic Speckle Pattern Interferometry (ESPI) based on laser interferometry. A satisfactory resolution was achieved in the non-contact displacement field measurements on small objects concerning the experimental dental samples. According to a specific clinical protocol, natural teeth were used (human mandibular premolars). A class I cavity was drilled and restored with nano composite material, according to Black principles. The polymerization was monitored by DH and ESPI in real time during the cure reaction of the restoration. The total displacement reported for the material in relation of the tooth wall was 3.7 μm (natural tooth). The technique showed the entire tooth surface (wall) deforming during polymerization shrinkage.

Plasma polymerized high energy density dielectric films for capacitors

NASA Technical Reports Server (NTRS)

Yamagishi, F. G.

1983-01-01

High energy density polymeric dielectric films were prepared by plasma polymerization of a variety of gaseous monomers. This technique gives thin, reproducible, pinhole free, conformable, adherent, and insoluble coatings and overcomes the processing problems found in the preparation of thin films with bulk polymers. Thus, devices are prepared completely in a vacuum environment. The plasma polymerized films prepared all showed dielectric strengths of greater than 1000 kV/cm and in some cases values of greater than 4000 kV/cm were observed. The dielectric loss of all films was generally less than 1% at frequencies below 10 kHz, but this value increased at higher frequencies. All films were self healing. The dielectric strength was a function of the polymerization technique, whereas the dielectric constant varied with the structure of the starting material. Because of the thin films used (thickness in the submicron range) surface smoothness of the metal electrodes was found to be critical in obtaining high dielectric strengths. High dielectric strength graft copolymers were also prepared. Plasma polymerized ethane was found to be thermally stable up to 150 C in the presence of air and 250 C in the absence of air. No glass transitions were observed for this material.

Wear resistance of thick diamond like carbon coatings against polymeric materials used in single screw plasticizing technology

NASA Astrophysics Data System (ADS)

Zitzenbacher, G.; Liu, K.; Forsich, C.; Heim, D.

2015-05-01

Wear on the screw and barrel surface accompany polymer single screw plasticizing technology from the beginning. In general, wear on screws can be reduced by using nitrided steel surfaces, fused armour alloys on the screw flights and coatings. However, DLC-coatings (Diamond Like Carbon) comprise a number of interesting properties such as a high hardness, a low coefficient of friction and an excellent corrosion resistance due to their amorphous structure. The wear resistance of about 50 µm thick DLC-coatings against polyamide 6.6, polybutylene terephthalate and polypropylene is investigated in this paper. The tribology in the solids conveying zone of a single screw extruder until the beginning of melting is evaluated using a pin on disc tribometer and a so called screw tribometer. The polymeric pins are pressed against coated metal samples using the pin on disc tribometer and the tests are carried out at a defined normal force and sliding velocity. The screw tribometer is used to perform tribological experiments between polymer pellets and rotating coated metal shafts simulating the extruder screw. Long term experiments were performed to evaluate the wear resistance of the DLC-coating. A reduction of the coefficient of friction can be observed after a frictional distance of about 20 kilometers using glass fibre reinforced polymeric materials. This reduction is independent on the polymer and accompanied by a black layer on the wear surface of the polymeric pins. The DLC-coated metal samples show an up to 16 µm deep wear track after the 100 kilometer test period against the glass fiber filled materials only.

One-Pot Enzymatic Production of Lignin-Composites.

PubMed

Ion, Sabina; Opris, Cristina; Cojocaru, Bogdan; Tudorache, Madalina; Zgura, Irina; Galca, Aurelian C; Bodescu, Adina M; Enache, Madalin; Maria, Gabriel-Mihai; Parvulescu, Vasile I

2018-01-01

A novel and efficient one-pot system for green production of artificial lignin bio-composites has been developed. Monolignols such as sinapyl (SA) and coniferyl (CA) alcohols were linked together with caffeic acid (CafAc) affording a polymeric network similar with natural lignin. The interaction of the dissolved SA/CA with CafAc already bound on a solid support (S C2 /S C6 -CafAc) allowed the attachment of the polymeric product direct on the support surface (S C2 /S C6 -CafAc-L 1 and S C2 /S C6 -CafAc-L 2 , from CA and SA, respectively). Accordingly, this procedure offers the advantage of a simultaneous polymer production and deposition. Chemically, oxi-copolymerization of phenolic derivatives (SA/CA and CAfAc) was performed with H 2 O 2 as oxidation reagent using peroxidase enzyme (2-1B mutant of versatile peroxidase from Pleurotus eryngii ) as catalyst. The system performance reached a maximum of conversion for SA and CA of 71.1 and 49.8%, respectively. The conversion is affected by the system polarity as resulted from the addition of a co-solvent (e.g., MeOH, EtOH, or THF). The chemical structure, morphology, and properties of the bio-composites surface were investigated using different techniques, e.g., FTIR, TPD-NH 3 , TGA, contact angle, and SEM. Thus, it was demonstrated that the SA monolignol favored bio-composites with a dense polymeric surface, high acidity, and low hydrophobicity, while CA allowed the production of thinner polymeric layers with high hydrophobicity.

Outbursts formation on low carbon and trip steel grades during hot-dip galvanisation

NASA Astrophysics Data System (ADS)

Petit, E. J.; Lamm, L.; Gilles, M.

2004-12-01

Low carbon and TRIP grade steels have been hot dip galvanised in order to study outbursts formation. Microstructure and texture of intermetallic phases have been observed after selective electrochemical etching by scanning electron microscopy. Potential versus time (chronopotentiometric) characteristics were recorded in order to monitor surface modifications. This combination of techniques enable to quantify and observe intermetallic phase one by one. The overall thickness of coating on both substrates are similar. However, microstructures of Fe-Zn intermetallic phases are very different on both grades. In particular, the V phase is dense on standard steel but develops a highly branched filament structure on TRIP steel. The transformation of V phase to d and G1 are limited on TRIP steel. Differences of texture provide clues for understanding mechanisms of formation of outbursts. They can account for the differences of mechanical properties and corrosion resistance. Silicon from the substrate influences the reactivity of TRIP steels due to capping and local reactions. La formation des outbursts a été étudiée sur un acier bas carbone et sur un acier TRIP galvanisés. Les épaisseurs des revêtements sont similaires. Néanmoins, les observations microscopiques et les érosions électrochimiques montrent que la répartition des phases intermétalliques et leurs microstructures diffèrent sensiblement en fonction de la nature du substrat. Ces différences expliquent les propriétés mécaniques et anticorrosions. L’encapsulation de la surface par les oxydes de silicium freine la transformation de la phase dzêta en delta et gamma sur l’acier TRIP.

Modelisation de la diffusion sur les surfaces metalliques: De l'adatome aux processus de croissance

NASA Astrophysics Data System (ADS)

Boisvert, Ghyslain

Cette these est consacree a l'etude des processus de diffusion en surface dans le but ultime de comprendre, et de modeliser, la croissance d'une couche mince. L'importance de bien mai triser la croissance est primordiale compte tenu de son role dans la miniaturisation des circuits electroniques. Nous etudions ici les surface des metaux nobles et de ceux de la fin de la serie de transition. Dans un premier temps, nous nous interessons a la diffusion d'un simple adatome sur une surface metallique. Nous avons, entre autres, mis en evidence l'apparition d'une correlation entre evenements successifs lorsque la temperature est comparable a la barriere de diffusion, i.e., la diffusion ne peut pas etre associee a une marche aleatoire. Nous proposons un modele phenomenologique simple qui reproduit bien les resultats des simulations. Ces calculs nous ont aussi permis de montrer que la diffusion obeit a la loi de Meyer-Neldel. Cette loi stipule que, pour un processus active, le prefacteur augmente exponentiellement avec la barriere. En plus, ce travail permet de clarifier l'origine physique de cette loi. En comparant les resultats dynamiques aux resultats statiques, on se rend compte que la barriere extraite des calculs dynamiques est essentiellement la meme que celle obtenue par une approche statique, beaucoup plus simple. On peut donc obtenir cette barriere a l'aide de methodes plus precises, i.e., ab initio, comme la theorie de la fonctionnelle de la densite, qui sont aussi malheureusement beaucoup plus lourdes. C'est ce que nous avons fait pour plusieurs systemes metalliques. Nos resultats avec cette derniere approche se comparent tres bien aux resultats experimentaux. Nous nous sommes attardes plus longuement a la surface (111) du platine. Cette surface regorge de particularites interessantes, comme la forme d'equilibre non-hexagonale des i lots et deux sites d'adsorption differents pour l'adatome. De plus, des calculs ab initio precedents n'ont pas reussi a confirmer la forme d'equilibre et surestiment grandement la barriere. Nos calculs, plus complets et dans un formalisme mieux adapte a ce genre de probleme, predisent correctement la forme d'equilibre, qui est en fait due a un relachement different du stress de surface aux deux types de marches qui forment les cotes des i lots. Notre valeur pour la barriere est aussi fortement diminuee lorsqu'on relaxe les forces sur les atomes de la surface, amenant le resultat theorique beaucoup plus pres de la valeur experimentale. Nos calculs pour le cuivre demontre en effet que la diffusion de petits i lots pendant la croissance ne peut pas etre negligee dans ce cas, mettant en doute la valeur des interpretations des mesures experimentales. (Abstract shortened by UMI.)

Polyvinyl pyridine microspheres

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor); Gupta, Amitava (Inventor); Volksen, Willi (Inventor)

1980-01-01

Microspheres are produced by cobalt gamma radiation initiated polymerization of a dilute aqueous vinyl pyridine solution. Addition of cross-linking agent provides higher surface area beads. Addition of monomers such as hydroxyethylmethacrylate acrylamide or methacrylamide increases hydrophilic properties and surface area of the beads. High surface area catalytic supports are formed in the presence of controlled pore glass substrate.

Polyvinyl pyridine microspheres

NASA Technical Reports Server (NTRS)

Rembaum, Alan (Inventor); Gupta, Amitava (Inventor); Volksen, Willi (Inventor)

1979-01-01

Microspheres are produced by cobalt gamma radiation initiated polymerization of a dilute aqueous vinyl pyridine solution. Addition of cross-linking agent provides higher surface area beads. Addition of monomers such as hydroxyethylmethacrylate acrylamide or methacrylamide increases hydrophilic properties and surface area of the beads. High surface area catalytic supports are formed in the presence of controlled pore glass substrate.

Tea stains-inspired initiator primer for surface grafting of antifouling and antimicrobial polymer brush coatings.

PubMed

Pranantyo, Dicky; Xu, Li Qun; Neoh, Koon-Gee; Kang, En-Tang; Ng, Ying Xian; Teo, Serena Lay-Ming

2015-03-09

Inspired by tea stains, plant polyphenolic tannic acid (TA) was beneficially employed as the primer anchor for functional polymer brushes. The brominated TA (TABr) initiator primer was synthesized by partial modification of TA with alkyl bromide functionalities. TABr with trihydroxyphenyl moieties can readily anchor on a wide range of substrates, including metal, metal oxide, polymer, glass, and silicon. Concomitantly, the alkyl bromide terminals serve as initiation sites for atom transfer radical polymerization (ATRP). Cationic [2-(methacryloyloxy)ethyl]trimethylammonium chloride (META) and zwitterionic 2-methacryloyloxyethyl phosphorylcholine (MPC) and N-(3-sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine (SBMA) were graft-polymerized from the TABr-anchored stainless steel (SS) surface. The cationic polymer brushes on the modified surfaces are bactericidal, while the zwitterionic coatings exhibit resistance against bacterial adhesion. In addition, microalgal attachment (microfouling) and barnacle cyprid settlement (macrofouling) on the functional polymer-grafted surfaces were significantly reduced, in comparison to the pristine SS surface. Thus, the bifunctional TABr initiator primer provides a unique surface anchor for the preparation of functional polymer brushes for inhibiting both microfouling and macrofouling.

Effects of ultraviolet irradiation on bonding strength between Co-Cr alloy and citric acid-crosslinked gelatin matrix.

PubMed

Inoue, Motoki; Sasaki, Makoto; Katada, Yasuyuki; Taguchi, Tetsushi

2014-02-01

Novel techniques for creating a strong bond between polymeric matrices and biometals are required. We immobilized polymeric matrices on the surface of biometal for drug-eluting stents through covalent bond. We performed to improve the bonding strength between a cobalt-chromium alloy and a citric acid-crosslinked gelatin matrix by ultraviolet irradiation on the surface of cobalt-chromium alloy. The ultraviolet irradiation effectively generated hydroxyl groups on the surface of the alloy. The bonding strength between the gelatin matrix and the alloy before ultraviolet irradiation was 0.38 ± 0.02 MPa, whereas it increased to 0.48 ± 0.02 MPa after ultraviolet irradiation. Surface analysis showed that the citric acid derivatives occurred on the surface of the cobalt-chromium alloy through ester bond. Therefore, ester bond formation between the citric acid derivatives active esters and the hydroxyl groups on the cobalt-chromium alloy contributed to the enhanced bonding strength. Ultraviolet irradiation and subsequent immobilization of a gelatin matrix using citric acid derivatives is thus an effective way to functionalize biometal surfaces.

Fabrication of an SPR Sensor Surface with Antifouling Properties for Highly Sensitive Detection of 2,4,6-Trinitrotoluene Using Surface-Initiated Atom Transfer Polymerization

PubMed Central

Yatabe, Rui; Onodera, Takeshi; Toko, Kiyoshi

2013-01-01

In this study, we modified a surface plasmon resonance immunosensor chip with a polymer using surface-initiated atom transfer polymerization (SI-ATRP) for the highly sensitive detection of 2,4,6-trinitrotoluene (TNT). To immobilize a TNT analogue on the polymer, mono-2-(methacryloyloxy)ethylsuccinate (MES), which has a carboxyl group, was used in this study. However, the anti-TNT antibody may adsorb non-specifically on the polymer surface by an electrostatic interaction because MES is negatively charged. Therefore, a mixed monomer with MES and diethylaminoethylmethacrylate (DEAEM), which has a tertiary amino group and is positively charged, was prepared to obtain electroneutrality for suppressing the nonspecific adsorption. The detection of TNT was performed by inhibition assay using the polymer surface. To ensure high sensitivity to TNT, the affinity between the surface and the antibody was optimized by controlling the density of the initiator for ATRP by mixing two types of self-assembled monolayer reagents. As a result, a limit of detection of 5.7 pg/mL (ppt) for TNT was achieved using the optimized surface. PMID:23877126

Tuning cell adhesion on polymeric and nanocomposite surfaces: Role of topography versus superhydrophobicity.

PubMed

Zangi, Sepideh; Hejazi, Iman; Seyfi, Javad; Hejazi, Ehsan; Khonakdar, Hossein Ali; Davachi, Seyed Mohammad

2016-06-01

Development of surface modification procedures which allow tuning the cell adhesion on the surface of biomaterials and devices is of great importance. In this study, the effects of different topographies and wettabilities on cell adhesion behavior of polymeric surfaces are investigated. To this end, an improved phase separation method was proposed to impart various wettabilities (hydrophobic and superhydrophobic) on polypropylene surfaces. Surface morphologies and compositions were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Cell culture was conducted to evaluate the adhesion of 4T1 mouse mammary tumor cells. It was found that processing conditions such as drying temperature is highly influential in cell adhesion behavior due to the formation of an utterly different surface topography. It was concluded that surface topography plays a more significant role in cell adhesion behavior rather than superhydrophobicity since the nano-scale topography highly inhibited the cell adhesion as compared to the micro-scale topography. Such cell repellent behavior could be very useful in many biomedical devices such as those in drug delivery and blood contacting applications as well as biosensors. Copyright © 2016 Elsevier B.V. All rights reserved.

BslA(YuaB) forms a hydrophobic layer on the surface of Bacillus subtilis biofilms.

PubMed

Kobayashi, Kazuo; Iwano, Megumi

2012-07-01

Biofilms are surface-associated bacterial aggregates, in which bacteria are enveloped by polymeric substances known as the biofilm matrix. Bacillus subtilis biofilms display persistent resistance to liquid wetting and gas penetration, which probably explains the broad-spectrum resistance of the bacteria in these biofilms to antimicrobial agents. In this study, BslA (formerly YuaB) was identified as a major contributor to the surface repellency of B. subtilis biofilms. Disruption of bslA resulted in the loss of surface repellency and altered the biofilm surface microstructure. BslA localized to the biofilm matrix in an exopolysaccharide-dependent manner. Purified BslA exhibited amphiphilic properties and formed polymers in response to increases in the area of the air-water interface in vitro. Genetic and biochemical analyses showed that the self-polymerization activity of BslA was essential for its ability to localize to the biofilm matrix. Confocal laser scanning microscopy showed that BslA formed a layer on the biofilm surface. Taken together, we propose that BslA, standing for biofilm-surface layer protein, is responsible for the hydrophobic layer on the surface of biofilms. © 2012 Blackwell Publishing Ltd.

Solar Ion Processing of Major Element Surface Compositions of Mature Mare Soils: Insights from Combined XPS and Analytical TEM Observations

NASA Technical Reports Server (NTRS)

Christoffersen, R.; Dukes, C.; Keller, L. P.; Baragiola, R.

2012-01-01

Solar wind ions are capable of altering the sur-face chemistry of the lunar regolith by a number of mechanisms including preferential sputtering, radiation-enhanced diffusion and sputter erosion of space weathered surfaces containing pre-existing compositional profiles. We have previously reported in-situ ion irradiation experiments supported by X-ray photoelectron spectroscopy (XPS) and analytical TEM that show how solar ions potentially drive Fe and Ti reduction at the monolayer scale as well as the 10-100 nm depth scale in lunar soils [1]. Here we report experimental data on the effect of ion irradiation on the major element surface composition in a mature mare soil.

Immobilization of Polyoxometalates on Tailored Polymeric Surfaces

PubMed Central

Aguado-Ureta, Saioa; Rodríguez-Hernández, Juan; del Campo, Adolfo; Perez-Álvarez, Leyre

2018-01-01

Herein we describe the preparation of hybrid polymer–inorganic interfaces by the immobilization of polyoxometalate nanoclusters on functionalized polymer surfaces. The polymeric surfaces were made of polystyrene-b-poly(acrylic acid)/polystyrene (PS-b-PAA/PS) blends by spin coating on a silicon wafer. The functionalization of the polymer film was obtained by interfacial migration of the amphiphilic block copolymer toward the interface upon water vapor annealing. The carboxylic acid functional groups contained in the PAA block were then employed to anchor the [LnIII(α-SiW11O39)]5− polyoxometalates (Ln: Ce, Er). This purpose was achieved by immersing the films in aqueous solutions of the in situ-formed inorganic nanoclusters. X-ray photoelectron and confocal Raman spectroscopies, together with atomic force microscopy, confirmed the immobilization of the inorganic species at the interface. PMID:29498656

Surface modification of nano-silica on the ligament advanced reinforcement system for accelerated bone formation: primary human osteoblasts testing in vitro and animal testing in vivo.

PubMed

Li, Mengmeng; Wang, Shiwen; Jiang, Jia; Sun, Jiashu; Li, Yuzhuo; Huang, Deyong; Long, Yun-Ze; Zheng, Wenfu; Chen, Shiyi; Jiang, Xingyu

2015-05-07

The Ligament Advanced Reinforcement System (LARS) has been considered as a promising graft for ligament reconstruction. To improve its biocompatibility and effectiveness on new bone formation, we modified the surface of a polyethylene terephthalate (PET) ligament with nanoscale silica using atom transfer radical polymerization (ATRP) and silica polymerization. The modified ligament is tested by both in vitro and in vivo experiments. Human osteoblast testing in vitro exhibits an ∼21% higher value in cell viability for silica-modified grafts compared with original grafts. Animal testing in vivo shows that there is new formed bone in the case of a nanoscale silica-coated ligament. These results demonstrate that our approach for nanoscale silica surface modification on LARS could be potentially applied for ligament reconstruction.

Silicone-containing aqueous polymer dispersions with hybrid particle structure.

PubMed

Kozakiewicz, Janusz; Ofat, Izabela; Trzaskowska, Joanna

2015-09-01

In this paper the synthesis, characterization and application of silicone-containing aqueous polymer dispersions (APD) with hybrid particle structure are reviewed based on available literature data. Advantages of synthesis of dispersions with hybrid particle structure over blending of individual dispersions are pointed out. Three main processes leading to silicone-containing hybrid APD are identified and described in detail: (1) emulsion polymerization of organic unsaturated monomers in aqueous dispersions of silicone polymers or copolymers, (2) emulsion copolymerization of unsaturated organic monomers with alkoxysilanes or polysiloxanes with unsaturated functionality and (3) emulsion polymerization of alkoxysilanes (in particular with unsaturated functionality) and/or cyclic siloxanes in organic polymer dispersions. The effect of various factors on the properties of such hybrid APD and films as well as on hybrid particles composition and morphology is presented. It is shown that core-shell morphology where silicones constitute either the core or the shell is predominant in hybrid particles. Main applications of silicone-containing hybrid APD and related hybrid particles are reviewed including (1) coatings which show specific surface properties such as enhanced water repellency or antisoiling or antigraffiti properties due to migration of silicone to the surface, and (2) impact modifiers for thermoplastics and thermosets. Other processes in which silicone-containing particles with hybrid structure can be obtained (miniemulsion polymerization, polymerization in non-aqueous media, hybridization of organic polymer and polysiloxane, emulsion polymerization of silicone monomers in silicone polymer dispersions and physical methods) are also discussed. Prospects for further developments in the area of silicone-containing hybrid APD and related hybrid particles are presented. Copyright © 2015. Published by Elsevier B.V.

Orientational behavior of thin films of poly(3-methylthiophene) on platinium: A FTIR and near edge x-ray absorption fine structure (NEXAFS) study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, X.Q.; Chen, J.; Hale, P.D.

1988-01-01

Near edge x-ray absorption fine structure (NEXAFS) and infrared reflection-absorption spectroscopy (IRRAS) have been used to study the orientational behavior of thin films of poly(3-methylthiophene) electrochemically polymerized on a platinum surface. Clear orientational effects, with the thiophene rings predominantly oriented parallel to the platinum surface, were observed when the thickness of the polymer films were within a few hundred /angstrom/A. It was found that more highly ordered films were produced at lower polymerization potential (1.4V vs SCE) than at higher potential (1.8V vs SCE). 5 refs., 4 figs., 2 tabs.

Eutectic phase in water-ice: a self-assembled environment conducive to metal-catalyzed non-enzymatic RNA polymerization.

PubMed

Monnard, Pierre-Alain; Ziock, Hans

2008-08-01

Information and catalytic polymers play an essential role in contemporary cellular life, and their emergence must have been crucial during the complex processes that led to the assembly of the first living systems. Polymerization reactions producing these molecules would have had to occur in aqueous medium, which is known to disfavor such reactions. Thus, it was proposed early on that these polymerizations had to be supported by particular environments, such as mineral surfaces and eutectic phases in water-ice, which would have led to the concentration of the monomers out of the bulk aqueous medium and their condensation. This review presents the work conducted to understand how the eutectic phases in water-ice might have promoted RNA polymerization, thereby presumably contributing to the emergence of the ancient information and catalytic system envisioned by the 'RNA-World' hypothesis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Hong.

A new technique was developed and demonstrated for combining carbon fibers with aromatic thermoplastic matrices to form a high-quality towpreg. The developed technique utilizes an in-situ electrochemical process (Electrochemical polymerization - ECP) to create the entire polymer matrix surrounding the fiber array by direct polymerization of monomer. Poly-paraxylylene (PPX) and derivatives are successfully polymerized in-situ on carbon fiber surfaces through ECP. A PPX/carbon-fiber towpreg with 40 vol % of matrix is achieved in a fairly short reaction time with a high polymer-coating efficiency. Vapor deposition polymerization (VDP) was also studied. PPX and carbon-fiber towpreg were made successfully by this process.more » A comparison between ECP and VDP was conducted. A study on electrochemical oxidation (ECO) of carbon fibers was also performed. The ECO treatment may be suitable for carbon fibers incorporated in composites with high-temperature curing resins and thermoplastic matrices.« less

Polymeric mechanical amplifiers of immune cytokine-mediated apoptosis

NASA Astrophysics Data System (ADS)

Mitchell, Michael J.; Webster, Jamie; Chung, Amanda; Guimarães, Pedro P. G.; Khan, Omar F.; Langer, Robert

2017-03-01

Physical forces affect tumour growth, progression and metastasis. Here, we develop polymeric mechanical amplifiers that exploit in vitro and in vivo physical forces to increase immune cytokine-mediated tumour cell apoptosis. Mechanical amplifiers, consisting of biodegradable polymeric particles tethered to the tumour cell surface via polyethylene glycol linkers, increase the apoptotic effect of an immune cytokine on tumour cells under fluid shear exposure by as much as 50% compared with treatment under static conditions. We show that targeted polymeric particles delivered to tumour cells in vivo amplify the apoptotic effect of a subsequent treatment of immune cytokine, reduce circulating tumour cells in blood and overall tumour cell burden by over 90% and reduce solid tumour growth in combination with the antioxidant resveratrol. The work introduces a potentially new application for a broad range of micro- and nanoparticles to maximize receptor-mediated signalling and function in the presence of physical forces.

Albumin as a "Trojan Horse" for polymeric nanoconjugate transendothelial transport across tumor vasculatures for improved cancer targeting.

PubMed

Yin, Qian; Tang, Li; Cai, Kaimin; Yang, Xujuan; Yin, Lichen; Zhang, Yanfeng; Dobrucki, Lawrence W; Helferich, William G; Fan, Timothy M; Cheng, Jianjun

2018-05-01

Although polymeric nanoconjugates (NCs) hold great promise for the treatment of cancer patients, their clinical utility has been hindered by the lack of efficient delivery of therapeutics to targeted tumor sites. Here, we describe an albumin-functionalized polymeric NC (Alb-NC) capable of crossing the endothelium barrier through a caveolae-mediated transcytosis pathway to better target cancer. The Alb-NC is prepared by nanoprecipitation of doxorubicin (Doxo) conjugates of poly(phenyl O-carboxyanhydrides) bearing aromatic albumin-binding domains followed by subsequent surface decoration of albumin. The administration of Alb-NCs into mice bearing MCF-7 human breast cancer xenografts with limited tumor vascular permeability resulted in markedly increased tumor accumulation and anti-tumor efficacy compared to their conventional counterpart PEGylated NCs (PEG-NCs). The Alb-NC provides a simple, low-cost and broadly applicable strategy to improve the cancer targeting efficiency and therapeutic effectiveness of polymeric nanomedicine.

Surface Modification of Biodegradable Polymers towards Better Biocompatibility and Lower Thrombogenicity

PubMed Central

Rudolph, Andreas; Teske, Michael; Illner, Sabine; Kiefel, Volker; Sternberg, Katrin; Grabow, Niels; Wree, Andreas; Hovakimyan, Marina

2015-01-01

Purpose Drug-eluting stents (DES) based on permanent polymeric coating matrices have been introduced to overcome the in stent restenosis associated with bare metal stents (BMS). A further step was the development of DES with biodegradable polymeric coatings to address the risk of thrombosis associated with first-generation DES. In this study we evaluate the biocompatibility of biodegradable polymer materials for their potential use as coating matrices for DES or as materials for fully bioabsorbable vascular stents. Materials and Methods Five different polymers, poly(L-lactide) PLLA, poly(D,L-lactide) PDLLA, poly(L-lactide-co-glycolide) P(LLA-co-GA), poly(D,L-lactide-co-glycolide) P(DLLA-co-GA) and poly(L-lactide-co-ε-caprolactone), P(LLA-co-CL) were examined in vitro without and with surface modification. The surface modification of polymers was performed by means of wet-chemical (NaOH and ethylenediamine (EDA)) and plasma-chemical (O2 and NH3) processes. The biocompatibility studies were performed on three different cell types: immortalized mouse fibroblasts (cell line L929), human coronary artery endothelial cells (HCAEC) and human umbilical vein endothelial cells (HUVEC). The biocompatibility was examined quantitatively using in vitro cytotoxicity assay. Cells were investigated immunocytochemically for expression of specific markers, and morphology was visualized using confocal laser scanning (CLSM) and scanning electron (SEM) microscopy. Additionally, polymer surfaces were examined for their thrombogenicity using an established hemocompatibility test. Results Both endothelial cell types exhibited poor viability and adhesion on all five unmodified polymer surfaces. The biocompatibility of the polymers could be influenced positively by surface modifications. In particular, a reproducible effect was observed for NH3-plasma treatment, which enhanced the cell viability, adhesion and morphology on all five polymeric surfaces. Conclusion Surface modification of polymers can provide a useful approach to enhance their biocompatibility. For clinical application, attempts should be made to stabilize the plasma modification and use it for coupling of biomolecules to accelerate the re-endothelialization of stent surfaces in vivo. PMID:26641662

Mechanics model for actin-based motility

NASA Astrophysics Data System (ADS)

Lin, Yuan

2009-02-01

We present here a mechanics model for the force generation by actin polymerization. The possible adhesions between the actin filaments and the load surface, as well as the nucleation and capping of filament tips, are included in this model on top of the well-known elastic Brownian ratchet formulation. A closed form solution is provided from which the force-velocity relationship, summarizing the mechanics of polymerization, can be drawn. Model predictions on the velocity of moving beads driven by actin polymerization are consistent with experiment observations. This model also seems capable of explaining the enhanced actin-based motility of Listeria monocytogenes and beads by the presence of Vasodilator-stimulated phosphoprotein, as observed in recent experiments.

Self-organized internal architectures of chiral micro-particles

NASA Astrophysics Data System (ADS)

Provenzano, Clementina; Mazzulla, Alfredo; Pagliusi, Pasquale; De Santo, Maria P.; Desiderio, Giovanni; Perrotta, Ida; Cipparrone, Gabriella

2014-02-01

The internal architecture of polymeric self-assembled chiral micro-particles is studied by exploring the effect of the chirality, of the particle sizes, and of the interface/surface properties in the ordering of the helicoidal planes. The experimental investigations, performed by means of different microscopy techniques, show that the polymeric beads, resulting from light induced polymerization of cholesteric liquid crystal droplets, preserve both the spherical shape and the internal self-organized structures. The method used to create the micro-particles with controlled internal chiral architectures presents great flexibility providing several advantages connected to the acquired optical and photonics capabilities and allowing to envisage novel strategies for the development of chiral colloidal systems and materials.

Mechanics model for actin-based motility.

PubMed

Lin, Yuan

2009-02-01

We present here a mechanics model for the force generation by actin polymerization. The possible adhesions between the actin filaments and the load surface, as well as the nucleation and capping of filament tips, are included in this model on top of the well-known elastic Brownian ratchet formulation. A closed form solution is provided from which the force-velocity relationship, summarizing the mechanics of polymerization, can be drawn. Model predictions on the velocity of moving beads driven by actin polymerization are consistent with experiment observations. This model also seems capable of explaining the enhanced actin-based motility of Listeria monocytogenes and beads by the presence of Vasodilator-stimulated phosphoprotein, as observed in recent experiments.

Barnacle cement: a polymerization model based on evolutionary concepts

PubMed Central

Dickinson, Gary H.; Vega, Irving E.; Wahl, Kathryn J.; Orihuela, Beatriz; Beyley, Veronica; Rodriguez, Eva N.; Everett, Richard K.; Bonaventura, Joseph; Rittschof, Daniel

2009-01-01

Summary Enzymes and biochemical mechanisms essential to survival are under extreme selective pressure and are highly conserved through evolutionary time. We applied this evolutionary concept to barnacle cement polymerization, a process critical to barnacle fitness that involves aggregation and cross-linking of proteins. The biochemical mechanisms of cement polymerization remain largely unknown. We hypothesized that this process is biochemically similar to blood clotting, a critical physiological response that is also based on aggregation and cross-linking of proteins. Like key elements of vertebrate and invertebrate blood clotting, barnacle cement polymerization was shown to involve proteolytic activation of enzymes and structural precursors, transglutaminase cross-linking and assembly of fibrous proteins. Proteolytic activation of structural proteins maximizes the potential for bonding interactions with other proteins and with the surface. Transglutaminase cross-linking reinforces cement integrity. Remarkably, epitopes and sequences homologous to bovine trypsin and human transglutaminase were identified in barnacle cement with tandem mass spectrometry and/or western blotting. Akin to blood clotting, the peptides generated during proteolytic activation functioned as signal molecules, linking a molecular level event (protein aggregation) to a behavioral response (barnacle larval settlement). Our results draw attention to a highly conserved protein polymerization mechanism and shed light on a long-standing biochemical puzzle. We suggest that barnacle cement polymerization is a specialized form of wound healing. The polymerization mechanism common between barnacle cement and blood may be a theme for many marine animal glues. PMID:19837892

Research regarding biodegradable properties of food polymeric products under microorganism activity

NASA Astrophysics Data System (ADS)

Opran, Constantin; Lazar, Veronica; Fierascu, Radu Claudiu; Ditu, Lia Mara

2018-02-01

Aim of this research is the structural analysis by comparison of the biodegradable properties of two polymeric products made by non-biodegradable polymeric material (polypropylene TIPPLEN H949 A) and biodegradable polymeric material (ECOVIO IS 1335), under microorganism activity in order to give the best solution for the manufacture of food packaging biodegradable products. It presents the results of experimental determinations on comparative analysis of tensile strength for the two types of polymers. The sample weight variations after fungal biodegradation activity revealed that, after 3 months, there are no significant changes in polymeric substratum for non-biodegradable polymeric. The microscopically analysis showed that the fungal filaments did not strongly adhered on the non-biodegradable polymeric material, instead, both filamentous fungi strains adhered and covered the surface of the biodegradable sample with germinated filamentous conidia. The spectral analysis of polymer composition revealed that non-biodegradable polymer polypropylene spectra are identical for control and for samples that were exposed to fungal activity, suggesting that this type of sample was not degraded by the fungi strains. Instead, for biodegradable polymer sample, it was observed significant structural changes across multiple absorption bands, suggesting enzyme activity manifested mainly by Aspergillus niger strain. Structural analysis of interdisciplinary research results, lead, to achieving optimal injection molded technology emphasizing technological parameters, in order to obtain food packaging biodegradable products.

Hydrophobic Coatings on Cotton Obtained by in Situ Plasma Polymerization of a Fluorinated Monomer in Ethanol Solutions.

PubMed

Molina, Ricardo; Teixidó, Josep Maria; Kan, Chi-Wai; Jovančić, Petar

2017-02-15

Plasma polymerization using hydrophobic monomers in the gas phase is a well-known technology to generate hydrophobic coatings. However, synthesis of functional hydrophobic coatings using plasma technology in liquids has not yet been accomplished. This work is consequently focused on polymerization of a liquid fluorinated monomer on cotton fabric initiated by atmospheric plasma in a dielectric barrier discharge configuration. Functional hydrophobic coatings on cotton were successfully achieved using in situ atmospheric plasma-initiated polymerization of fluorinated monomer dissolved in ethanol. Gravimetric measurements reveal that the amount of polymer deposited on cotton substrates can be modulated with the concentration of monomer in ethanol solution, and cross-linking reactions occur during plasma polymerization of a fluorinated monomer even without the presence of a cross-linking agent. FTIR and XPS analysis were used to study the chemical composition of hydrophobic coatings and to get insights into the physicochemical processes involved in plasma treatment. SEM analysis reveals that at high monomer concentration, coatings possess a three-dimensional pattern with a characteristic interconnected porous network structure. EDX analysis reveals that plasma polymerization of fluorinated monomers takes place preferentially at the surface of cotton fabric and negligible polymerization takes place inside the cotton fabric. Wetting time measurements confirm the hydrophobicity of cotton coatings obtained although equilibrium moisture content was slightly decreased. Additionally, the abrasion behavior and resistance to washing of plasma-coated cotton has been evaluated.

Controlled Bioactive Molecules Delivery Strategies for Tendon and Ligament Tissue Engineering using Polymeric Nanofibers.

PubMed

Hiong Teh, Thomas Kok; Hong Goh, James Cho; Toh, Siew Lok

2015-01-01

The interest in polymeric nanofibers has escalated over the past decade given its promise as tissue engineering scaffolds that can mimic the nanoscale structure of the native extracellular matrix. With functionalization of the polymeric nanofibers using bioactive molecules, localized signaling moieties can be established for the attached cells, to stimulate desired biological effects and direct cellular or tissue response. The inherently high surface area per unit mass of polymeric nanofibers can enhance cell adhesion, bioactive molecules loading and release efficiencies, and mass transfer properties. In this review article, the application of polymeric nanofibers for controlled bioactive molecules delivery will be discussed, with a focus on tendon and ligament tissue engineering. Various polymeric materials of different mechanical and degradation properties will be presented along with the nanofiber fabrication techniques explored. The bioactive molecules of interest for tendon and ligament tissue engineering, including growth factors and small molecules, will also be reviewed and compared in terms of their nanofiber incorporation strategies and release profiles. This article will also highlight and compare various innovative strategies to control the release of bioactive molecules spatiotemporally and explore an emerging tissue engineering strategy involving controlled multiple bioactive molecules sequential release. Finally, the review article concludes with challenges and future trends in the innovation and development of bioactive molecules delivery using polymeric nanofibers for tendon and ligament tissue engineering.

Single-molecule resolution of protein dynamics on polymeric membrane surfaces: the roles of spatial and population heterogeneity.

PubMed

Langdon, Blake B; Mirhossaini, Roya B; Mabry, Joshua N; Sriram, Indira; Lajmi, Ajay; Zhang, Yanxia; Rojas, Orlando J; Schwartz, Daniel K

2015-02-18

Although polymeric membranes are widely used in the purification of protein pharmaceuticals, interactions between biomolecules and membrane surfaces can lead to reduced membrane performance and damage to the product. In this study, single-molecule fluorescence microscopy provided direct observation of bovine serum albumin (BSA) and human monoclonal antibody (IgG) dynamics at the interface between aqueous buffer and polymeric membrane materials including regenerated cellulose and unmodified poly(ether sulfone) (PES) blended with either polyvinylpyrrolidone (PVP), polyvinyl acetate-co-polyvinylpyrrolidone (PVAc-PVP), or polyethylene glycol methacrylate (PEGM) before casting. These polymer surfaces were compared with model surfaces composed of hydrophilic bare fused silica and hydrophobic trimethylsilane-coated fused silica. At extremely dilute protein concentrations (10(-3)-10(-7) mg/mL), protein surface exchange was highly dynamic with protein monomers desorbing from the surface within ∼1 s after adsorption. Protein oligomers (e.g., nonspecific dimers, trimers, or larger aggregates), although less common, remained on the surface for 5 times longer than monomers. Using newly developed super-resolution methods, we could localize adsorption sites with ∼50 nm resolution and quantify the spatial heterogeneity of the various surfaces. On a small anomalous subset of the adsorption sites, proteins adsorbed preferentially and tended to reside for significantly longer times (i.e., on "strong" sites). Proteins resided for shorter times overall on surfaces that were more homogeneous and exhibited fewer strong sites (e.g., PVAc-PVP/PES). We propose that strong surface sites may nucleate protein aggregation, initiated preferentially by protein oligomers, and accelerate ultrafiltration membrane fouling. At high protein concentrations (0.3-1.0 mg/mL), fewer strong adsorption sites were observed, and surface residence times were reduced. This suggests that at high concentrations, adsorbed proteins block strong sites from further protein adsorption. Importantly, this demonstrates that strong binding sites can be modified by changing solution conditions. Membrane surfaces are intrinsically heterogeneous; by employing single-molecule techniques, we have provided a new framework for understanding protein interactions with such surfaces.

Identification of Two Suppressors of CSG2 Calcium Sensitivity, SCS7 and SUR2, as Genes Encoding Hydroxylases of the Sphingolipid Biosynthetic Pathway of Saccharomyces cerevisiae

DTIC Science & Technology

1997-12-10

process can adjusted by experimental alteration of thyroid status. Hyperthyroidism speeds up the time table while hypothyroidism retards it. When 88... canine kidney MDCK cells. The relative amounts ofthe labeled products can be differentially recovered from the basolateral and apical surfaces of these

Quantifying the impact of seasonal and short-term manure application decisions on phosphorus loss in surface runoff

USDA-ARS?s Scientific Manuscript database

Agricultural phosphorus (P) management is a pressing research and policy issue due to concerns about P loss from fields and water quality degradation. Better information is especially needed on the risk of P loss from dairy manure applied to fields in winter. We used the SurPhos computer model to as...

Modélisation macroscopique des milieux stratifiés conducteurs

NASA Astrophysics Data System (ADS)

Matagne, E.; Conard, J. Ph.

1997-11-01

Many laminated structures are recognised in Electrotechnics : magnetic cores, flat conductors windings, slotted surfaces... These structures exhibit macroscopic properties, as magnetic than electric ones. This paper shows how these characteristics can be obtained by homogenisation. It deals with linear materials but taking into account the effect of eddy currents, as well on the macroscopic magnetic permeability as on the macroscopic electric conductivity, which become then complex numbers. An example of use of the macroscopic properties is provided. On peut identifier en électrotechnique de nombreuses structures stratifiées: noyaux magnétiques, bobinages formés de conducteurs plats, surfaces encochées... Ces structures présentent des propriétés macroscopiques tant magnétiques qu'électriques. Cet article montre comment ces caractéristiques peuvent être obtenues par homogénéisation. Il se limite au cas de matériaux linéaires mais en prenant en compte l'effet des courants de Foucault aussi bien sur la perméabilité magnétique macroscopique que sur la conductivité électrique macroscopique, grandeurs qui deviennent alors des nombres complexes. Un exemple d'utilisation des caractéristiques macroscopiques est fourni.

Polymerized phospholipid bilayers as permanent coatings for small amine separations using mixed aqueous/organic capillary zone electrophoresis.

PubMed

Pei, Lei; Lucy, Charles A

2012-12-07

Phospholipid bilayer (SPB) coatings have been used in capillary electrophoresis to reduce the nonspecific adsorption between the capillary wall and cationic analytes. This paper describes the use of the polymerizable lipid 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (Diyne PC) as a permanent capillary coating. A supported phospholipid bilayer was formed on the capillary walls and polymerization was performed in situ using ultraviolet irradiation. The polymerization reaction was monitored by UV-visible absorbance spectroscopy and atomic force microscopy. The EOF of the polymerized Diyne PC coating was moderately suppressed (2.0×10(-4)cm(2)/Vs) compared to a non-polymerized Diyne PC bilayer (0.3×10(-4)cm(2)/Vs), but the stability was improved significantly. Separations of benzylamine, veratrylamine, phenylethylamine and tolyethylamine using a poly Diyne PC coated capillary yielded efficiency of 220,000-370,000 plates/m and peak asymmetry factor 0.48-1.18. Specifically, the poly(Diyne PC) coating provided improved separation resolution in NACE due to the reduced surface adsorption. Copyright © 2012 Elsevier B.V. All rights reserved.

Enhancing aerobic digestion potential of municipal waste-activated sludge through removal of extracellular polymeric substance.

PubMed

Merrylin, J; Kaliappan, S; Kumar, S Adish; Yeom, Ick-Tae; Banu, J Rajesh

2014-01-01

A protease-secreting bacteria was used to pretreat municipal sewage sludge to enhance aerobic digestion. To enhance the accessibility of the sludge to the enzyme, extracellular polymeric substances were removed using citric acid thereby removing the flocs in the sludge. The conditions for the bacterial pretreatment were optimized using response surface methodology. The results of the bacterial pretreatment indicated that the suspended solids reduction was 18% in sludge treated with citric acid and 10% in sludge not treated with citric acid whereas in raw sludge, suspended solids reduction was 5.3%. Solubilization was 10.9% in the sludge with extracellular polymeric substances removed in contrast to that of the sludge with extracellular polymeric substances, which was 7.2%, and that of the raw sludge, which was just 4.8%. The suspended solids reduction in the aerobic reactor containing pretreated sludge was 52.4% whereas that in the control reactor was 15.3%. Thus, pretreatment with the protease-secreting bacteria after the removal of extracellular polymeric substances is a cost-effective and environmentally friendly method.

Nanostructural surface engineering of grafted polymers on inorganic oxide substrates for membrane separations

NASA Astrophysics Data System (ADS)

Yoshida, Wayne Hiroshi

Nanostructural engineering of inorganic substrates by free radical graft polymerization was studied with the goal of developing new membrane materials for pervaporation. Graft polymerization consisted of modification of surface hydroxyls with vinyl trimethoxysilane, followed by solution graft polymerization reaction using either vinyl acetate (VAc) or vinyl pyrrolidone (VP). The topology of the modified surfaces was studied by atomic force microscopy (AFM) on both atomically smooth silicon wafer substrates and microporous inorganic membrane supports in order to deduce the effects of modification on the nanostructural properties of the membrane. While unmodified wafers showed a root-mean-square (RMS) surface roughness of 0.21 +/- 0.03 nm, roughness increased to 3.15 +/- 0.23 nm upon silylation. Under poor solvent conditions (i.e., air), surfaces modified with higher poly(vinyl acetate) (PVAc) or poly(vinyl pyrrolidone) (PVP) polymer graft yields displayed lateral inhomogeneities in the polymer layer. Although RMS surface roughness was nearly identical (0.81--0.85 nm) for PVAc-modified surfaces grafted at different monomer concentrations, the skewness of the height distribution decreased from 2.22 to 0.78 as polymer graft yield increased from 0.8 to 3.5 mg/m2. The polymer-modified surfaces were used to create inorganic pervaporation membranes consisting of a single macromolecular separation layer formed by graft polymerization. PVAc grafted silica membranes (500A native pore size) were found selective for MTBE in the separation of 0.1--1% (v/v) MTBE from water, achieving MTBE enrichment factors as high as 371 at a permeate flux of 0.38 l/m2 hr and a Reynolds number of 6390; however, these membranes could not separate anhydrous organic mixtures. Pervaporative separation of methanol/MTBE mixtures was possible with PVAc and PVP-modified alumina supports of 50A native pore size, where the separation layer consisted of grafted polymer chains with estimated radius of gyration 4.5--6.8 times larger than the membrane pore radius. Methanol separation factors for the PVP and PVAc-grafted alumina pervaporation membranes reached values of 26 and 100 (respectively) at total permeate fluxes of 0.055--1.26 kg/m 2 hr and 0.55--6.19 kg/m2 hr. The present study demonstrated that selective pervaporation membranes for separation of both organic/organic and organic/aqueous mixtures can be effectively designed by careful selection of the surface-grafted polymer chain density and the ratio of the polymer chain size to the native support pore size.

Structure of Thermotoga maritima Stationary Phase Survival Protein SurE: A Novel Acid Phosphatase

PubMed Central

Zhang, R.-G.; Skarina, T.; Katz, J.E.; Beasley, S.; Khachatryan, A.; Vyas, S.; Arrowsmith, C.H.; Clarke, S.; Edwards, A.; Joachimiak, A.; Savchenko, A.

2009-01-01

Summary Background The rpoS, nlpD, pcm, and surE genes are among many whose expression is induced during the stationary phase of bacterial growth. rpoS codes for the stationary-phase RNA polymerase σ subunit, and nlpD codes for a lipoprotein. The pcm gene product repairs damaged proteins by converting the atypical isoaspartyl residues back to L-aspartyls. The physiological and biochemical functions of surE are unknown, but its importance in stress is supported by the duplication of the surE gene in E. coli subjected to high-temperature growth. The pcm and surE genes are highly conserved in bacteria, archaea, and plants. Results The structure of SurE from Thermotoga maritima was determined at 2.0 Å. The SurE monomer is composed of two domains; a conserved N-terminal domain, a Rossman fold, and a C-terminal oligomerization domain, a new fold. Monomers form a dimer that assembles into a tetramer. Biochemical analysis suggests that SurE is an acid phosphatase, with an optimum pH of 5.5–6.2. The active site was identified in the N-terminal domain through analysis of conserved residues. Structure-based site-directed point mutations abolished phosphatase activity. T. maritima SurE intra- and inter-subunit salt bridges were identified that may explain the SurE thermostability. Conclusions The structure of SurE provided information about the protein’s fold, oligomeric state, and active site. The protein possessed magnesium-dependent acid phosphatase activity, but the physiologically relevant substrate(s) remains to be identified. The importance of three of the assigned active site residues in catalysis was confirmed by site-directed mutagenesis. PMID:11709173

Immobilization of biomolecules to plasma polymerized pentafluorophenyl methacrylate.

PubMed

Duque, Luis; Menges, Bernhard; Borros, Salvador; Förch, Renate

2010-10-11

Thin films of plasma polymerized pentafluorophenyl methacrylate (pp-PFM) offer highly reactive ester groups throughout the structure of the film that allow for subsequent reactions with different aminated reagents and biological molecules. The present paper follows on from previous work on the plasma deposition of pentafluorophenyl methacrylate (PFM) for optimum functional group retention (Francesch, L.; Borros, S.; Knoll, W.; Foerch, R. Langmuir 2007, 23, 3927) and reactivity in aqueous solution (Duque, L.; Queralto, N.; Francesch, L.; Bumbu, G. G.; Borros, S.; Berger, R.; Förch, R. Plasma Process. Polym. 2010, accepted for publication) to investigate the binding of a biologically active peptide known to induce cellular adhesion (IKVAV) and of biochemically active proteins such as BSA and fibrinogen. Analyses of the films and of the immobilization of the biomolecules were carried out using infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The attachment of the biomolecules on pulsed plasma polymerized pentafluorophenyl methacrylate was monitored using surface plasmon resonance spectroscopy (SPR). SPR analysis confirmed the presence of immobilized biomolecules on the plasma polymer and was used to determine the mass coverage of the peptide and proteins adsorbed onto the films. The combined analysis of the surfaces suggests the covalent binding of the peptide and proteins to the surface of the pp-PFM.

The Nanoconfined Free Radical Polymerization: Reaction Kinetics and Thermodynamics

NASA Astrophysics Data System (ADS)

Zhao, Haoyu; Simon, Sindee

The reaction kinetics and thermodynamics of nanoconfined free radical polymerizations are investigated for methyl methacrylate (MMA) and ethyl methacrylate (EMA) monomers using differential scanning calorimetry. Controlled pore glass is used as the confinement medium with pore diameters as small as 7.5 nm; the influence of both hydrophobic (silanized such that trimethylsilyl groups cover the surface) and hydrophilic (native silanol) surfaces is investigated. Propagation rates increase when monomers are reacted in the hydrophilic pores presumably due to the specific interactions between the carbonyl and silanol groups; however, the more flexible EMA monomer shows weaker effects. On the other hand, initial rates of polymerization in hydrophobic pores are unchanged from the bulk. In both pores, the onset of autoacceleration occurs earlier due to the reduced diffusivity of confined chains, which may be compensated at high temperatures. In addition to changes in kinetics, the reaction thermodynamics can be affected under nanoconfinement. Specifically, the ceiling temperature (Tc) is shifted to lower temperatures in nanopores, with pore surface chemistry showing no significant effects; the equilibrium conversion is also reduced at high temperatures below Tc. These observations are attributed to a larger negative change in entropy on propagation for the confined system, with the MMA system again showing greater effects. Funding from ACS PRF is gratefully acknowledged.

Kir6.2-dependent high-affinity repaglinide binding to β-cell KATP channels

PubMed Central

Hansen, Ann Maria K; Hansen, John Bondo; Carr, Richard D; Ashcroft, Frances M; Wahl, Philip

2005-01-01

The β-cell KATP channel is composed of two types of subunit – the inward rectifier K+ channel (Kir6.2) which forms the channel pore, and the sulphonylurea receptor (SUR1), which serves as a regulatory subunit. The N-terminus of Kir6.2 is involved in transduction of sulphonylurea binding into channel closure, and deletion of the N-terminus (Kir6.2ΔN14) results in functional uncoupling of the two subunits. In this study, we investigate the interaction of the hypoglycaemic agents repaglinide and glibenclamide with SUR1 and the effect of Kir6.2 on this interaction. We further explore how the binding properties of repaglinide and glibenclamide are affected by functional uncoupling of SUR1 and Kir6.2 in Kir6.2ΔN14/SUR1 channels. All binding experiments are performed on membranes in ATP-free buffer at 37°C. Repaglinide was found to bind with low affinity (KD=59±16 nM) to SUR1 alone, but with high affinity (increased ∼150-fold) when SUR1 was co-expressed with Kir6.2 (KD=0.42±0.03 nM). Glibenclamide, tolbutamide and nateglinide all bound with marginally lower affinity to SUR1 than to Kir6.2/SUR1. Repaglinide bound with low affinity (KD=51±23 nM) to SUR1 co-expressed with Kir6.2ΔN14. In contrast, the affinity for glibenclamide, tolbutamide and nateglinide was only mildly changed as compared to wild-type channels. In whole-cell patch-clamp experiments inhibition of Kir6.2ΔN14/SUR1 currents by both repaglinide and nateglinde is abolished. The results suggest that Kir6.2 causes a conformational change in SUR1 required for high-affinity repaglinide binding, or that the high-affinity repaglinide-binding site includes contributions from both SUR1 and Kir6.2. Glibenclamide, tolbutamide and nateglinide binding appear to involve only SUR1. PMID:15678092

Covalent attachment of phospholipid analogous polymers to modify a polymeric membrane surface: a novel approach.

PubMed

Xu, Zhi-Kang; Dai, Qing-Wen; Wu, Jian; Huang, Xiao-Jun; Yang, Qian

2004-02-17

A novel method for the surface modification of a microporous polypropylene membrane by tethering phospholipid analogous polymers (PAPs) is given, which includes the photoinduced graft polymerization of N,N-dimethylaminoethyl methacrylate (DMAEMA) and the ring-opening reaction of grafted poly-(DMAEMA) with 2-alkyloxy-2-oxo-1,3,2-dioxaphospholanes. Five 2-alkyloxy-2-oxo-1,3,2-dioxaphospholanes, containing octyloxy, dodecyloxy, tetradecyloxy, hexadecyloxy, and octadecyloxy groups in the molecular structure, were used to fabricate the PAP-modified polypropylene membranes. The attenuated total reflectance FT-IR spectra of the original, poly(DMAEMA)-grafted, and PAP-modified membranes confirmed the chemical changes on the membrane surface. Scanning electron microscope pictures showed that, compared with the original membrane, the surface porosities ofpoly(DMAEMA)-grafted and PAP-modified membranes were somewhat reduced. Water contact angles measured by the sessile drop method on PAP-modified membranes were slightly lower than that on the original polypropylene membrane, but higher than those on poly(DMAEMA)-grafted membranes with the exception of octyloxy-containing PAP-modified membranes. However, BSA adsorption experiments indicated that the five PAP-modified membranes had a much better protein-resistant property than the original polypropylene membrane and the poly(DMAEMA)-grafted membranes. For hexadecyloxy- and octadecyloxy-containing PAP-modified membranes, almost no protein adsorption was observed when the grafting degree was above 6 wt %. It was also found that the platelet adhesion was remarkably suppressed on the PAP-modified membranes. All these results demonstrate that the described approach is an effective way to improve the surface biocompatibility for polymeric membranes.

Brulures par Diluant

PubMed Central

Benbrahim, A.; Jerrah, H.; Diouri, M.; Bahechar, N.; Boukind, E.H.

2009-01-01

Summary La flamme de diluant est une cause non rare de brûlure dans le contexte marocain. Nous avons jugé intéressant de faire une étude épidémiologique sur la brûlure par flamme de diluant (BFD) au centre national des brûlés (CNB) du CHU Ibn-Rochd de Casablanca. Ce travail a été réalisé sur une période de 10 mois (septembre 2007/juin 2008). Le but du travail est de montrer les caractéristiques de ce type de brûlures pour les prévenir et ce par l'information sur le diluant, produit causant ces brûlures, et ses différents dangers, la brûlure notamment. Durant cette période, nous avons colligé 17 cas de BFD sur un total de 356 patients admis au CNB pour brûlures aiguës toute étiologie confondue. La moyenne d'age des patients concernés est de 32 ans. Ils sont presque tous de sexe masculin (16 hommes/1 femme) et ont des antécédents de toxicomanie et/ou de délinquance. Tous nos patients sont de bas niveau socio-économique et habitent dans des bidonvilles pour la plupart. La brûlure est souvent secondaire à une agression dans la rue (92% des cas). Concernant les caractéristiques de la brûlure, la surface cutanée brûlée moyenne est de 23%; elle est souvent profonde et siège surtout au niveau des membres supérieurs et du tronc. PMID:21991179

Analyse de l'effet des courants induits sur l'impédance d'un système électromagnétique alimenté en tension BF ou HF. Utilisation de la méthode des circuits couplés

NASA Astrophysics Data System (ADS)

Maouche, B.; Feliachi, M.

1997-10-01

In this paper, a study of the interaction between the inductor and the load of an axisymmetrical induction device is proposed. This interaction concerns the effect of the eddy current on both the excitation current and on the system impedance. A half analytical model, based on a numerical discretization of the electromagnetic solution domain, is used. In each cell of the numerical discretization, an analytical calculation using the Moment Method (MM) is considered. In the case of strong skin effect (High Frequency: HF), the formulation makes use of the Impedance Boundary Condition (IBC); in the contrary case (Low Frequency: LF), the interior domain is discretized. Dans cet article nous proposons l'étude de l'influence d'une charge (induit) conductrice sur la répartition du courant inducteur ainsi que sur l'impédance du système. L'inducteur est à géométrie axisymétrique de forme solénoïdale ou pancake destiné au chauffage par induction. Une méthode semi-analytique, basée sur une discrétisation du domaine en mailles élémentaires auxquelles s'applique une formulation intégrale (Méthode des Circuits Couplés : MCC) des grandeurs électromagnétiques, est utilisée. Dans le cas où l'effet de peau est important (Haute Fréquence:HF), la formulation associe la Condition d'Impédance de Surface; dans le cas contraire (Basse Fréquence : BF), un maillage du domaine interne est pratiqué.

Surface modification of polymers for biocompatibility via exposure to extreme ultraviolet radiation.

PubMed

Inam Ul Ahad; Bartnik, Andrzej; Fiedorowicz, Henryk; Kostecki, Jerzy; Korczyc, Barbara; Ciach, Tomasz; Brabazon, Dermot

2014-09-01

Polymeric biomaterials are being widely used for the treatment of various traumata, diseases and defects in human beings due to ease in their synthesis. As biomaterials have direct interaction with the extracellular environment in the biological world, biocompatibility is a topic of great significance. The introduction or enhancement of biocompatibility in certain polymers is still a challenge to overcome. Polymer biocompatibility can be controlled by surface modification. Various physical and chemical methods (e.g., chemical and plasma treatment, ion implantation, and ultraviolet irradiation etc.) are in use or being developed for the modification of polymer surfaces. However an important limitation in their employment is the alteration of bulk material. Different surface and bulk properties of biomaterials are often desirable for biomedical applications. Because extreme ultraviolet (EUV) radiation penetration is quite limited even in low density mediums, it could be possible to use it for surface modification without influencing the bulk material. This article reviews the degree of biocompatibility of different polymeric biomaterials being currently employed in various biomedical applications, the surface properties required to be modified for biocompatibility control, plasma and laser ablation based surface modification techniques, and research studies indicating possible use of EUV for enhancing biocompatibility. © 2013 Wiley Periodicals, Inc.

Synthesis of dodecylamine-functionalized graphene quantum dots and their application as stabilizers in an emulsion polymerization of styrene.

PubMed

Xuan, Wang; Ruiyi, Li; Zaijun, Li; Junkang, Liu

2017-11-01

Pickering emulsions have attracted considerable interest due to their potential applications in many fields, such as the food, pharmaceutical, petroleum and cosmetics industries. The study reports the synthesis of dodecylamine-functionalized graphene quantum dots (d-GQDs) and their implementation as stabilizers in an emulsion polymerization of styrene. First, d-GQDs are prepared by thermal pyrolysis of citric acid and dodecylamine in 0.1M ammonium hydroxide. The resulting d-GQDs consist of small graphene sheets with abundant amino, carboxyl, acylamino, hydroxyl and alkyl chains on the edge. The amphiphilic structure gives the d-GQDs high surface activity. The addition of d-GQDs can reduce the surface tension of water to 30.8mNm -1 and the interfacial tension of paraffin oil/water to 0.0182mNm -1 . The surface activity is much better than that of previously reported solid particle surfactants for Pickering emulsions and is close to that of sodium dodecylbenzenesulfonate, which is, a classical organic surfactants. Then, d-GQDs are employed as solid particle surfactants for stabilizing styrene-in-water emulsions. The emulsions exhibit excellent stability at pH 7. However, stability is lost when the pH is more than 9 or less than 4. The pH-switchable behaviour can be attributed to the protonation of amino groups in a weak acid medium and dissociation of carboxyl groups in a weak base medium. Finally, 2,2'-azobis(2-methylpropionitrile) is introduced into the Pickering emulsions to trigger emulsion polymerization of styrene. The as-prepared polystyrene spheres display a uniform morphology with a narrow diameter distribution. The fluorescent d-GQDs coated their surfaces. This study presents an approach for the fabrication of amphiphilic GQDs and GQDs-based functional materials, which have a wide range of potential applications in emulsion polymerization, as well as in sensors, catalysts, and energy storage. Copyright © 2017 Elsevier Inc. All rights reserved.

Assembly of tobacco mosaic virus into fibrous and macroscopic bundled arrays mediated by surface aniline polymerization.

PubMed

Niu, Zhongwei; Bruckman, Michael A; Li, Siqi; Lee, L Andrew; Lee, Byeongdu; Pingali, Sai Venkatesh; Thiyagarajan, P; Wang, Qian

2007-06-05

One-dimensional (1D) polyaniline/tobacco mosaic virus (TMV) composite nanofibers and macroscopic bundles of such fibers were generated via a self-assembly process of TMV assisted by in-situ polymerization of polyaniline on the surface of TMV. At near-neutral reaction pH, branched polyaniline formed on the surface of TMV preventing lateral association. Therefore, long 1D nanofibers were observed with high aspect ratios and excellent processibility. At a lower pH, transmission electron microscopy (TEM) analysis revealed that initially long nanofibers were formed which resulted in bundled structures upon long-time reaction, presumably mediated by the hydrophobic interaction because of the polyaniline on the surface of TMV. In-situ time-resolved small-angle X-ray scattering study of TMV at different reaction conditions supported this mechanism. This novel strategy to assemble TMV into 1D and 3D supramolecular composites could be utilized in the fabrication of advanced materials for potential applications including electronics, optics, sensing, and biomedical engineering.

Cellulose microfibrils grafted with PBA via surface-initiated atom transfer radical polymerization for biocomposite reinforcement.

PubMed

Li, Shuzhao; Xiao, Miaomiao; Zheng, Anna; Xiao, Huining

2011-09-12

Immobilizing poly(butyl acrylate) (PBA) on cellulose microfibrils (CMFs) by atom transfer radical polymerization (ATRP) of butyl acrylate (BA) on the surface of 2-bromoisobutyryl-functionalized CMF generated highly hydrophobic microfibrils (CMF-PBA) with a hard core and a soft-shell structure. TGA and static water contact angle results suggested that the surfaces of the modified CMF samples were not completely covered by PBA chains until the molecular weight of grafts became sufficiently long. The GPC results indicated that the grafts with low molecular weight showed controlled/"living" characteristics of the surface-initiated ATRP; however, there existed more side reactions with the increase in molecular weights. Biocomposites consisting of polypropylene (PP) and CMF-PBA samples exhibited significantly improved compatibility, interface adhesion, and mechanical properties with the increase in PBA graft length. The findings confirmed that the longer grafts facilitated the better entanglement of PBA grafts with PP macromolecules and thus further improved the mechanical properties.

Highly efficient non-biofouling coating of zwitterionic polymers: poly((3-(methacryloylamino)propyl)-dimethyl(3-sulfopropyl)ammonium hydroxide).

PubMed

Cho, Woo Kyung; Kong, Bokyung; Choi, Insung S

2007-05-08

This work describes the formation of highly efficient non-biofouling polymeric thin films of poly((3-(methacryloylamino)propyl)-dimethyl(3-sulfopropyl)ammonium hydroxide), (poly(MPDSAH)). The poly(MPDSAH) films were generated from the self-assembled monolayers terminating in an initiator of atom transfer radical polymerization (ATRP) by the surface-initiated ATRP of MPDSAH. The poly(MPDSAH) films on a gold surface were characterized by ellipsometry, FT-IR spectroscopy, contact angle goniometery, and X-ray photoelectron spectroscopy. The copper complexes and unpolymerized monomers trapped inside the polymer brushes were completely washed out by soaking the poly(MPDSAH)-coated substrate in water at 40 degrees C for 4 days. The amount of proteins nonspecifically adsorbed onto the poly(MPDSAH) films was evaluated by surface plasmon resonance spectroscopy: the adsorption of proteins was <0.6 ng/cm(2) on the surfaces for all the model proteins. The ability of the poly(MPDSAH) films to resist the nonspecific adsorption of proteins was comparable to that of the best known systems.

Quantification of metallic nanoparticle morphology with tilt series imaging by transmission electron microscopy

NASA Astrophysics Data System (ADS)

Dutta, Aniruddha; Yuan, Biao; Clukay, Christopher J.; Grabill, Christopher N.; Heinrich, Helge; Bhattacharya, Aniket; Kuebler, Stephen M.

2012-02-01

We report on the quantitative analysis of electrolessly deposited Au and Ag nanoparticles (NPs) on SU8 polymer with the help of High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM) in tilt series. Au NPs act as nucleating agents for the electroless deposition of silver. Au NPs were prepared by attachingAu^3+cations to amine functionalized SU8 polymeric surfaces and then reducing it with aqueous NaBH4. The nanoscale morphology of the deposited NPs on the surface of polymer has been studied from the dark field TEM cross sectional images. Ag NPs were deposited on the cross-linked polymeric surface from a silver citrate solution reduced by hydroquinone. HAADF-STEM enables us to determine the distances between the NPs and their exact locations at and near the surface. The particle distribution, sizes and densities provide us with the data necessary to control the parameters for the development of the electroless deposition technique for emerging nanoscale technologies.

Modifying Surface Fluctuations of Polymer Melt Films with Substrate Modification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yang; He, Qiming; Zhang, Fan

Deposition of a plasma polymerized film on a silicon substrate substantially changes the fluctuations on the surface of a sufficiently thin, melt polystyrene (PS) film atop the substrate. Surface fluctuation relaxation times measured with X-ray photon correlation spectroscopy (XPCS) for ca. 4R g thick melt films of 131 kg/mol linear PS on silicon and on a plasma polymer modified silicon wafer can both be described using a hydrodynamic continuum theory (HCT) that assumes the film is characterized throughout its depth by the bulk viscosity. However, when the film thickness is reduced to ~3R g, confinement effects are evident. The surfacemore » fluctuations are slower than predicted using the HCT, and the confinement effect for the PS on silicon is larger than that for the PS on the plasma polymerized film. This deviation is thus due to a difference in the thicknesses of the strongly adsorbed layers at the substrate which are impacted by the substrate surface energy.« less

Improved biocompatibility of poly (styrene-b-(ethylene-co-butylene)-b-styrene) elastomer by a surface graft polymerization of hyaluronic acid.

PubMed

Li, Xiaomeng; Luan, Shifang; Shi, Hengchong; Yang, Huawei; Song, Lingjie; Jin, Jing; Yin, Jinghua; Stagnaro, Paola

2013-02-01

Hyaluronic acid (HA) is an important component of extracellular matrix (ECM) in many tissues, providing a hemocompatible and supportive environment for cell growth. In this study, glycidyl methacrylate-hyaluronic acid (GMHA) was first synthesized and verified by proton nuclear magnetic resonance ((1)H NMR) spectroscopy. GMHA was then grafted to the surface of biomedical elastomer poly (styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) via an UV-initiated polymerization, monitored by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The further improvement of biocompatibility of the GMHA-modified SEBS films was assessed by platelet adhesion experiments and in vitro response of murine osteoblastic cell line MC-3T3-E1 with the virgin SEBS surface as the reference. It showed that the surface modification with HA strongly resisted platelet adhesion whereas improved cell-substrate interactions. Copyright © 2012 Elsevier B.V. All rights reserved.

Modifying Surface Fluctuations of Polymer Melt Films with Substrate Modification

DOE PAGES

Zhou, Yang; He, Qiming; Zhang, Fan; ...

2017-08-14

Deposition of a plasma polymerized film on a silicon substrate substantially changes the fluctuations on the surface of a sufficiently thin, melt polystyrene (PS) film atop the substrate. Surface fluctuation relaxation times measured with X-ray photon correlation spectroscopy (XPCS) for ca. 4R g thick melt films of 131 kg/mol linear PS on silicon and on a plasma polymer modified silicon wafer can both be described using a hydrodynamic continuum theory (HCT) that assumes the film is characterized throughout its depth by the bulk viscosity. However, when the film thickness is reduced to ~3R g, confinement effects are evident. The surfacemore » fluctuations are slower than predicted using the HCT, and the confinement effect for the PS on silicon is larger than that for the PS on the plasma polymerized film. This deviation is thus due to a difference in the thicknesses of the strongly adsorbed layers at the substrate which are impacted by the substrate surface energy.« less

Optical monitoring of thin film electro-polymerization on surface of ITO-coated lossy-mode resonance sensor

NASA Astrophysics Data System (ADS)

Sobaszek, Michał; Dominik, Magdalena; Burnat, Dariusz; Bogdanowicz, Robert; Stranak, Viteszlav; Sezemsky, Petr; Śmietana, Mateusz

2017-04-01

This work presents an optical fiber sensors based on lossy-mode resonance (LMR) phenomenon supported by indium tin oxide (ITO) thin overlay for investigation of electro-polymerization effect on ITO's surface. The ITO overlays were deposited on core of polymer-clad silica (PCS) fibers using reactive magnetron sputtering (RMS) method. Since ITO is electrically conductive and electrochemically active it can be used as a working electrode in 3-electrode cyclic voltammetry setup. For fixed potential applied to the electrode current flow decrease with time what corresponds to polymer layer formation on the ITO surface. Since LMR phenomenon depends on optical properties in proximity of the ITO surface, polymer layer formation can be monitored optically in real time. The electrodeposition process has been performed with Isatin which is a strong endogenous neurochemical regulator in humans as it is a metabolic derivative of adrenaline. It was found that optical detection of Isatin is possible in the proposed configuration.

Homochiral polymerization-driven selective growth of graphene nanoribbons

NASA Astrophysics Data System (ADS)

Sakaguchi, Hiroshi; Song, Shaotang; Kojima, Takahiro; Nakae, Takahiro

2017-01-01

The surface-assisted bottom-up fabrication of graphene nanoribbons (GNRs), which consists of the radical polymerization of precursors followed by dehydrogenation, has attracted attention because of the method's ability to control the edges and widths of the resulting ribbon. Although these reactions on a metal surface are believed to be catalytic, the mechanism has remained unknown. Here, we demonstrate 'conformation-controlled surface catalysis': the two-zone chemical vapour deposition of a 'Z-bar-linkage' precursor, which represents two terphenyl units linked in a 'Z' shape, results in the efficient formation of acene-type GNRs with a width of 1.45 nm through optimized cascade reactions. These precursors exhibit flexibility that allows them to adopt chiral conformations with height asymmetry on a Au(111) surface, which enables the production of self-assembled homochiral polymers in a chain with a planar conformation, followed by dehydrogenation via a conformation-controlled mechanism. This is conceptually analogous to enzymatic catalysis and will be useful for the fabrication of new nanocarbon materials.

Nucleation of polystyrene latex particles in the presence of gamma-methacryloxypropyltrimethoxysilane: functionalized silica particles.

PubMed

Bourgeat-Lami, Elodie; Insulaire, Mickaelle; Reculusa, Stéphane; Perro, Adeline; Ravaine, Serge; Duguet, Etienne

2006-02-01

Silica/polystyrene nanocomposite particles with different morphologies were synthesized through emulsion polymerization of styrene in the presence of silica particles previously modified by gamma-methacryloxypropyltrimethoxysilane (MPS). Grafting of the silane molecule was performed by direct addition of MPS to the aqueous silica suspension in the presence of an anionic surfactant under basic conditions. The MPS grafting density on the silica surface was determined using the depletion method and plotted against the initial MPS concentration. The influence of the MPS grafting density, the silica particles size and concentration and the nature of the surfactant on the polymerization kinetics and the particles morphology was investigated. When the polymerization was performed in the presence of an anionic surfactant, transmission electron microscopy images showed the formation of polymer spheres around silica for MPS grafting densities lower than typically 1 micromole x m(-2) while the conversion versus time curves indicated a strong acceleration effect under such conditions. In contrast, polymerizations performed in the presence of a larger amount of MPS moieties or in the presence of a non ionic emulsifier resulted in the formation of "excentered" core-shell morphologies and lower polymerization rates. The paper identifies the parameters that allow to control particles morphology and polymerization kinetics and describes the mechanism of formation of the nanocomposite colloids.

Influence of light polymerization modes on degree of conversion and crosslink density of dental composites.

PubMed

da Silva, Eduardo Moreira; Poskus, Laiza Tatiana; Guimarães, José Guilherme Antunes; de Araújo Lima Barcellos, Alexandre; Fellows, Carlos Eduardo

2008-03-01

This study analyzed the influence of light polymerization modes on crosslink density (CD) and the degree of conversion (DC) of dental composites. A minifilled hybrid and a nanofilled dental composite were photoactivated with two light polymerization modes: Conventional-850 mW/cm2 for 20 s and Gradual-50 up to 1,000 mW/cm2 for 10 s+1,000 mW/cm2 for 10 s. DC was determined by the use of FT-Raman-spectrometer. A softening test, using Knoop diamond indentation, was carried out at the top and bottom of 2 mm thick dental composite disks, before and after storage in 100% ethanol for 24 h, in order to represent the amount of crosslink density. Data were analyzed by ANOVA and Student-Newman-Keuls' multiple range test (alpha=0.05). The DC was influenced by light polymerization modes, with Gradual mode presenting lower DC. On bottom surfaces, the nanofilled dental composite was more susceptible to softening by ethanol than minifilled hybrid, and gradual light polymerization of nanofilled dental composite resulted in more softening than when conventional light polymerization was used. The results suggest that nanofilled composites are capable undergoing more plasticization if applied in thick increments.

Self-assembled tunable networks of sticky colloidal particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demortiere, Arnaud; Snezhko, Oleksiy Alexey; Sapozhnikov, Maksim

Self-assembled tunable networks of microscopic polymer fibers ranging from wavy colloidal "fur" to highly interconnected networks are created from polymer systems and an applied electric field. The networks emerge via dynamic self-assembly in an alternating (ac) electric field from a non-aqueous suspension of "sticky" polymeric colloidal particles with a controlled degree of polymerization. The resulting architectures are tuned by the frequency and amplitude of the electric field and surface properties of the particles.

Synthesis and electrochemical properties of polyaniline nanofibers by interfacial polymerization.

PubMed

Manuel, James; Ahn, Jou-Hyeon; Kim, Dul-Sun; Ahn, Hyo-Jun; Kim, Ki-Won; Kim, Jae-Kwang; Jacobsson, Per

2012-04-01

Polyaniline nanofibers were prepared by interfacial polymerization with different organic solvents such as chloroform and carbon tetrachloride. Field emission scanning electron microscopy and transmission electron microscopy were used to study the morphological properties of polyaniline nanofibers. Chemical characterization was carried out using Fourier transform infrared spectroscopy, UV-Vis spectroscopy, and X-ray diffraction spectroscopy and surface area was measured using BET isotherm. Polyaniline nanofibers doped with lithium hexafluorophosphate were prepared and their electrochemical properties were evaluated.

Composite plasma polymerized sulfonated polystyrene membrane for PEMFC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nath, Bhabesh Kumar; Khan, Aziz; Chutia, Joyanti, E-mail: jchutiaiasst@gmail.com

2015-10-15

Highlights: • Methyl methane sulfonate (MMS) is used as the sulfonating agent. • The proton conductivity of the membrane is found to be 0.141 S cm{sup −1}. • Power density of fuel cell with styrene/MMS membrane is 0.5 W cm{sup −2}. • The membrane exhibits thermal stability up to 140 °C. - Abstract: This work presents the introduction of an organic compound methyl methane sulfonate (MMS) for the first time in fabrication of polystyrene based proton exchange membrane (PEM) by plasma polymerization process. The membrane is fabricated by co-polymerizing styrene and MMS in capacitively coupled continuous RF plasma. The chemicalmore » composition of the plasma polymerized polymer membrane is investigated using Fourier Transform Infrared Spectroscopy which reveals the formation of composite structure of styrene and MMS. The surface morphology studied using AFM and SEM depicts the effect of higher partial pressure of MMS on surface topography of the membrane. The proton transport property of the membrane studied using electrochemical impedance spectroscopy shows the achievement of maximum proton conductivity of 0.141 S cm{sup −1} which is comparable to Nafion 117 membrane. Fuel cell performance test of the synthesized membrane shows a maximum power density of 500 mW cm{sup −2} and current density of 0.62 A cm{sup −2} at 0.6 V.« less

Surface morphology control of cross-linked polymer particles via dispersion polymerization.

PubMed

Peng, Bo; Imhof, Arnout

2015-05-14

Cross-linked polymer colloids (poly(methyl methacrylate) and polystyrene) with diverse shapes were prepared in polar solvents (ethanol, methanol and water) via dispersion polymerization, in which a linear addition of the cross-linker was used during reaction. Apart from spherical particles we found dented spheres or particles covered with nodules, or a combination of both. A comprehensive investigation was carried out, mainly concentrating on the effect of the experimental conditions (e.g., the addition start time and total addition time, cross-linker density and the solvency of the solvents) on particle morphologies. Consequently, we suggest a number of effective ways for the synthesis of regular (spherical) colloidal particles through maintaining a relatively low concentration of the cross-linker during the entire reaction, or forcing the co-polymerization (of monomer and cross-linker) locus to the continuous medium, or using a high quality or quantity of the stabilizer. Moreover, the size of the particles was also precisely manipulated by varying the polarity of the solvents, the concentration of the cross-linker, and the amount and average molecular weight of the stabilizer. In addition, the formation of the heavily dented particles with a very rough surface prepared under a pure or oxygen-'contaminated' nitrogen environment was monitored over time. The results accumulated in this article are of use for a better understanding of the mechanism of the polymerization and control over the structure and property of polymer particles.

Structural and surface functionality changes in reticulated vitreous carbon produced from poly(furfuryl alcohol) with sodium hydroxide additions

NASA Astrophysics Data System (ADS)

Oishi, Silvia Sizuka; Botelho, Edson Cocchieri; Rezende, Mirabel Cerqueira; Ferreira, Neidenêi Gomes

2017-02-01

The use of sodium hydroxide to neutralize the acid catalyst increases the storage life of poly(furfuryl alcohol) (PFA) resin avoiding its continuous polymerization. In this work, a concentrated sodium hydroxide solution (NaOH) was added directly to the PFA resin in order to minimize the production of wastes generated when PFA is washed with diluted basic solution. Thus, different amounts of this concentrated basic solution were added to the resin up to reaching pH values of around 3, 5, 7, and 9. From these four types of modified PFA two sample sets of reticulated vitreous carbon (RVC) were processed and heat treated at two different temperatures (1000 and 1700 °C). A correlation among cross-link density of PFA and RVC morphology, structural ordering and surface functionalities was systematically studied using Fourier transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy techniques. The PFA neutralization (pH 7) led to its higher polymerization degree, promoting a crystallinity decrease on RVC treated at 1000 °C as well as its highest percentages of carboxylic groups on surface. A NaOH excess (pH 9) substantially increased the RVC oxygen content, but its crystallinity remained similar to those for samples from pH 3 and 5 treated at 1000 °C, probably due to the reduced presence of carboxylic group and the lower polymerization degree of its cured resin. Samples with pH 3 and 5 heat treated at 1000 and 1700 °C can be considered the most ordered which indicated that small quantities of NaOH may be advantageous to minimize continuous polymerization of PFA resin increasing its storage life and improving RVC microstructure.

Comparative evaluation of surface porosities in conventional heat polymerized acrylic resin cured by water bath and microwave energy with microwavable acrylic resin cured by microwave energy

PubMed Central

Singh, Sunint; Palaskar, Jayant N.; Mittal, Sanjeev

2013-01-01

Background: Conventional heat cure poly methyl methacrylate (PMMA) is the most commonly used denture base resin despite having some short comings. Lengthy polymerization time being one of them and in order to overcome this fact microwave curing method was recommended. Unavailability of specially designed microwavable acrylic resin made it unpopular. Therefore, in this study, conventional heat cure PMMA was polymerized by microwave energy. Aim and Objectives: This study was designed to evaluate the surface porosities in PMMA cured by conventional water bath and microwave energy and compare it with microwavable acrylic resin cured by microwave energy. Materials and Methods: Wax samples were obtained by pouring molten wax into a metal mold of 25 mm × 12 mm × 3 mm dimensions. These samples were divided into three groups namely C, CM, and M. Group C denotes conventional heat cure PMMA cured by water bath method, CM denotes conventional heat cure PMMA cured by microwave energy, M denotes specially designed microwavable acrylic denture base resin cured by microwave energy. After polymerization, each sample was scanned in three pre-marked areas for surface porosities using the optical microscope. As per the literature available, this instrument is being used for the first time to measure the porosity in acrylic resin. It is a reliable method of measuring area of surface pores. Portion of the sample being scanned is displayed on the computer and with the help of software area of each pore was measured and data were analyzed. Results: Conventional heat cure PMMA samples cured by microwave energy showed maximum porosities than the samples cured by conventional water bath method and microwavable acrylic resin cured by microwave energy. Higher percentage of porosities was statistically significant, but well within the range to be clinically acceptable. Conclusion: Within the limitations of this in-vitro study, conventional heat cure PMMA can be cured by microwave energy without compromising on its property such as surface porosity. PMID:24015000

Bulk Heterojunction Solar Cell with Nitrogen-Doped Carbon Nanotubes in the Active Layer: Effect of Nanocomposite Synthesis Technique on Photovoltaic Properties

PubMed Central

Keru, Godfrey; Ndungu, Patrick G.; Mola, Genene T.; Nyamori, Vincent O.

2015-01-01

Nanocomposites of poly(3-hexylthiophene) (P3HT) and nitrogen-doped carbon nanotubes (N-CNTs) have been synthesized by two methods; specifically, direct solution mixing and in situ polymerization. The nanocomposites were characterized by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray dispersive spectroscopy, UV-Vis spectrophotometry, photoluminescence spectrophotometry (PL), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis, and dispersive surface energy analysis. The nanocomposites were used in the active layer of a bulk heterojunction organic solar cell with the composition ITO/PEDOT:PSS/P3HT:N-CNTS:PCBM/LiF/Al. TEM and SEM analysis showed that the polymer successfully wrapped the N-CNTs. FTIR results indicated good π-π interaction within the nanocomposite synthesized by in situ polymerization as opposed to samples made by direct solution mixing. Dispersive surface energies of the N-CNTs and nanocomposites supported the fact that polymer covered the N-CNTs well. J-V analysis show that good devices were formed from the two nanocomposites, however, the in situ polymerization nanocomposite showed better photovoltaic characteristics.

In-situ Polymerization of Polyaniline/Polypyrrole Copolymer using Different Techniques

NASA Astrophysics Data System (ADS)

Hammad, A. S.; Noby, H.; Elkady, M. F.; El-Shazly, A. H.

2018-01-01

The morphology and surface area of the poly(aniline-co-pyrrole) copolymer (PANPY) are important properties which improve the efficiency of the copolymer in various applications. In this investigation, different techniques were employed to produce PANPY in different morphologies. Aniline and pyrrole were used as monomers, and ammonium peroxydisulfate (APS) was used as an oxidizer with uniform molar ratio. Rapid mixing, drop-wise mixing, and supercritical carbon dioxide (ScCO2) polymerization techniques were appointed. The chemical structure, crystallinity, porosity, and morphology of the composite were distinguished by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer, Emmett and Teller (BET) analysis, and transmission electron microscopy (TEM) respectively. The characterization tests indicated that the polyaniline/polypyrrole copolymer was successfully prepared with different morphologies. Based on the obtained TEM, hollow nanospheres were formed using rapid mixing technique with acetic acid that have a diameter of 75 nm and thickness 26 nm approximately. Also, according to the XRD, the produced structures have a semi- crystalline structure. The synthesized copolymer with ScCO2-assisted polymerization technique showed improved surface area (38.1 m2/g) with HCl as dopant.

Analysis of the morphology, stability, and folding pathways of ring polymers with supramolecular topological constraints using molecular simulation and nonlinear manifold learning

NASA Astrophysics Data System (ADS)

Wang, Jiang; Ferguson, Andrew

Ring polymers offer a wide range of natural and engineered functions and applications, including as circular bacterial DNA, crown ethers for cation chelation, and ``molecular machines'' such as mechanical nanoswitches. The morphology and dynamics of ring polymers are governed by the chemistry and degree of polymerization of the ring, and intramolecular and supramolecular topological constraints such as knots or mechanically-interlocked rings. We perform molecular dynamics simulations of polyethylene ring polymers as a function of degree of polymerization and in different topological states, including a knotted state, catenane state (two interlocked rings), and borromean state (three interlocked rings). Applying nonlinear manifold learning to our all-atom simulation trajectories, we extract low-dimensional free energy surfaces governing the accessible conformational states and their relative thermodynamic stability. The free energy surfaces reveal how degree of polymerization and topological constraints affect the thermally accessible conformations, chiral symmetry breaking, and folding and collapse pathways of the rings, and present a means to rationally engineer ring size and topology to preferentially stabilize particular conformational states.

Surface grafting of Eu3+ doped luminescent hydroxyapatite nanomaterials through metal free light initiated atom transfer radical polymerization for theranostic applications.

PubMed

Zeng, Guangjian; Liu, Meiying; Jiang, Ruming; Heng, Chunning; Huang, Qiang; Mao, Liucheng; Hui, Junfeng; Deng, Fengjie; Zhang, Xiaoyong; Wei, Yen

2017-08-01

We reported a simple and efficient method to prepare the hydrophilic luminescent HAp polymer nanocomposites through the combination of ligand exchange and metal free light initiated surface-initiated atom transfer radical polymerization (SI-ATRP) using 10-phenylphenothiazine (PTH) as organic catalyst and 2-methacryloyloxyethyl phosphorylcholine (MPC) and itaconic acid (IA) as monomers. The biological imaging and drug delivery performance of HAp-poly(MPC-IA) nanorods were examined to evaluate their potential for biomedical applications. Results suggested that hydrophilic HAp-poly(MPC-IA) nanorods can be successfully prepared. More importantly, the HAp-poly(MPC-IA) exhibited excellent water dispersibility, desirable biocompatibility and good performance for biological imaging and controlled drug delivery applications. As compared with other controlled living polymerization reactions, the metal free light initiated SI-ATRP displayed many advantages such as easy for handle, mild reaction conditions, toxicity and fluorescence quenching from metal catalysts. Therefore, we believe that this strategy should be a useful and effective strategy for preparation of HAp nanomaterials for biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Design of water-repellant coating using dual scale size of hybrid silica nanoparticles on polymer surface

NASA Astrophysics Data System (ADS)

Conti, J.; De Coninck, J.; Ghazzal, M. N.

2018-04-01

The dual-scale size of the silica nanoparticles is commonly aimed at producing dual-scale roughness, also called hierarchical roughness (Lotus effect). In this study, we describe a method to build a stable water-repellant coating with controlled roughness. Hybrid silica nanoparticles are self-assembled over a polymeric surface by alternating consecutive layers. Each one uses homogenously distributed silica nanoparticles of a particular size. The effect of the nanoparticle size of the first layer on the final roughness of the coating is studied. The first layer enables to adjust the distance between the silica nanoparticles of the upper layer, leading to a tuneable and controlled final roughness. An optimal size nanoparticle has been found for higher water-repellency. Furthermore, the stability of the coating on polymeric surface (Polycarbonate substrate) is ensured by photopolymerization of hybridized silica nanoparticles using Vinyl functional groups.

Structure and properties of polymeric composite materials during 1501 days outer space exposure at Salyut-7 orbital station

NASA Technical Reports Server (NTRS)

Startsev, Oleg V.; Nikishin, Eugene F.

1995-01-01

Specimens of polymeric composite materials for aviation and space applications such as glass fiber reinforced plastics (GFRP), carbon fiber reinforced plastics (CFRP), organic fiber reinforced plastics (OFRP), and hybrid plastics (HP) based on epoxy compounds were exposed to the space environment on the surface of Salyut-7 orbital station. The space exposure lasted 1501 days as a maximum. The data relating to the change in mechanical properties, mass losses, glass transition temperature, linear thermal expansion coefficient, and microstructure after various periods of exposure are given. It has been found that the change in properties is caused by the processes of binder postcuring and microerosion of the exposed surface of plastics. The phenomenon of strengthening of the surface layer of hybrid composites, due to which the nature of destruction changes at bending loads, has been revealed.

Core/shell, protuberance-free multiwalled carbon nanotube/polyaniline nanocomposites via interfacial chemistry of aryl diazonium salts.

PubMed

Mekki, Ahmed; Samanta, Soumen; Singh, Ajay; Salmi, Zakaria; Mahmoud, Rachid; Chehimi, Mohamed M; Aswal, Dinesh K

2014-03-15

Highly uniform core-shell like multi-walled carbon nanotubes-polyaniline (MWCNT-PANI) nanocomposites were prepared in two steps (i) surface modification of MWCNTs with a 4-aminodiphenylamine group via in situ diazonium generation process; and (ii) polymerization of aniline onto surface modified MWCNTs. This functionalization helped to easily disperse the MWCNTs in acidic solutions; hence it is suitable for the chemical oxidative polymerization of aniline. It was found that MWCNT-PANI nano-composites with higher MWCNTs loading yield PANI chains with more quinoid units than the pure PANI, which results in significant improvement in the conductivity of the composites. This facile approach of synthesizing core-shell nanocomposites highlights the efficiency of the interfacial chemistry of aryl diazonium salts in generating conductive polymer/MWCNT nanocomposites with enhanced conductivity and high surface area. Copyright © 2013 Elsevier Inc. All rights reserved.

Nicotinamide-rich diet improves physical endurance by up-regulating SUR2A in the heart

PubMed Central

Sukhodub, Andriy; Sudhir, Rajni; Du, Qingyou; Jovanović, Sofija; Reyes, Santiago; Jovanović, Aleksandar

2011-01-01

Abstract SUR2A is an ATP-binding protein that serves as a regulatory subunit of cardioprotective ATP-sensitive K+ (KATP) channels. Based on signalling pathway regulating SUR2A expression and SUR2A role in regulating numbers of fully assembled KATP channels, we have suggested that nicotinamide-rich diet could improve physical endurance by stimulating SUR2A expression. We have found that mice on nicotinamide-rich diet significantly improved physical endurance, which was associated with significant increase in expression of SUR2A. Transgenic mice with solely overexpressed SUR2A on control diet had increased physical endurance in a similar manner as the wild-type mice on nicotinamide-rich diet. The experiments focused on action membrane potential and intracellular Ca2+ concentration have demonstrated that increased SUR2A expression was associated with the activation of sarcolemmal KATP channels and steady Ca2+ levels in cardiomyocytes in response to β-adrenergic stimulation. In contrast, the same challenge in the wild-type was characterized by a lack of the channel activation and rise in intracellular Ca2+. Nicotinamide-rich diet was ineffective to increase physical endurance in mice lacking KATP channels. This study has shown that nicotinamide-rich diet improves physical endurance by increasing expression of SUR2A and that this is a sole mechanism of the nicotinamide-rich diet effect. The obtained results suggest that oral nicotinamide is a regulator of SUR2A expression and has a potential as a drug that can improve physical endurance in conditions where this effect would be desirable. PMID:20731746