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.

TRANSITION METAL CATALYSIS IN CONTROLLED RADICAL POLYMERIZATION: ATOM TRANSFER RADICAL POLYMERIZATION. (R826735)

EPA Science Inventory

Novel and diversified macromolecular structures, which include polymers with designed topologies (top), compostions (middle), and functionalities (bottom), can be prepared by atom transfer radical polymerization processes. These polymers can be synthesized from a large variety of...

Morphological control of conductive polymers utilized electrolysis polymerization technique: trial of fabricating biocircuit.

PubMed

Onoda, Mitsuyoshi

2014-10-01

Conductive polymers are a strong contender for making electronic circuits. The growth pattern in conductive polymer synthesis by the electrolysis polymerization method was examined. The growth pattern is deeply related to the coupling reaction of the radical cation and the deprotonation reaction following it and changes suddenly depending on the kind and concentration of the supporting electrolyte and the solvent used. That is, when the electrophilic substitution coupling reaction becomes predominant, the three-dimensional growth form is observed, and when the radical coupling reaction becomes predominant, the two-dimensional growth morphology is observed. In addition, the growth pattern can be comparatively easily controlled by changing the value of the polymerization constant current, and it is considered that the indicator and development for biocircuit research with neuron-type devices made of conjugated polymers was obtained.

RAFT polymerization and some of its applications.

PubMed

Moad, Graeme; Rizzardo, Ezio; Thang, San H

2013-08-01

Reversible addition-fragmentation chain transfer (RAFT) is one of the most robust and versatile methods for controlling radical polymerization. With appropriate selection of the RAFT agent for the monomers and reaction conditions, it is applicable to the majority of monomers subject to radical polymerization. The process can be used in the synthesis of well-defined homo-, gradient, diblock, triblock, and star polymers and more complex architectures, which include microgels and polymer brushes. In this Focus Review we describe how the development of RAFT and RAFT application has been facilitated by the adoption of continuous flow techniques using tubular reactors and through the use of high-throughput methodology. Applications described include the use of RAFT in the preparation of polymers for optoelectronics, block copolymer therapeutics, and star polymer rheology control agents. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Integration of CuAAC Polymerization and Controlled Radical Polymerization into Electron Transfer Mediated "Click-Radical" Concurrent Polymerization.

PubMed

Xue, Wentao; Wang, Jie; Wen, Ming; Chen, Gaojian; Zhang, Weidong

2017-03-01

The successful chain-growth copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization employing Cu(0)/pentamethyldiethylenetriamine (PMDETA) and alkyl halide as catalyst is first investigated by a combination of nuclear magnetic resonance, gel-permeation chromatography, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. In addition, the electron transfer mediated "click-radical" concurrent polymerization utilizing Cu(0)/PMDETA as catalyst is successfully employed to generate well-defined copolymers, where controlled CuAAC polymerization of clickable ester monomer is progressed in the main chain acting as the polymer backbone, the controlled radical polymerization (CRP) of acrylic monomer is carried out in the side chain. Furthermore, it is found that there is strong collaborative effect and compatibility between CRP and CuAAC polymerization to improve the controllability. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Redline, Erica Marie; Bolintineanu, Dan S.; Lane, J. Matthew

The aim of this study was to alter polymerization chemistry to improve network homogeneity in free-radical crosslinked systems. It was hypothesized that a reduction in heterogeneity of the network would lead to improved mechanical performance. Experiments and simulations were carried out to investigate the connection between polymerization chemistry, network structure and mechanical properties. Experiments were conducted on two different monomer systems - the first is a single monomer system, urethane dimethacrylate (UDMA), and the second is a two-monomer system consisting of bisphenol A glycidyl dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) in a ratio of 70/30 BisGMA/TEGDMA by weight. Themore » methacrylate systems were crosslinked using traditional radical polymeriza- tion (TRP) with azobisisobutyronitrile (AIBN) or benzoyl peroxide (BPO) as an initiator; TRP systems were used as the control. The monomers were also cross-linked using activator regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) as a type of controlled radical polymerization (CRP). FTIR and DSC were used to monitor reac- tion kinetics of the systems. The networks were analyzed using NMR, DSC, X-ray diffraction (XRD), atomic force microscopy (AFM), and small angle X-ray scattering (SAXS). These techniques were employed in an attempt to quantify differences between the traditional and controlled radical polymerizations. While a quantitative methodology for characterizing net- work morphology was not established, SAXS and AFM have shown some promising initial results. Additionally, differences in mechanical behavior were observed between traditional and controlled radical polymerized thermosets in the BisGMA/TEGDMA system but not in the UDMA materials; this finding may be the result of network ductility variations between the two materials. Coarse-grained molecular dynamics simulations employing a novel model of the CRP reaction were carried out for the UDMA system, with parameters calibrated based on fully atomistic simulations of the UDMA monomer in the liquid state. Detailed metrics based on network graph theoretical approaches were implemented to quantify the bond network topology resulting from simulations. For a broad range of polymerization parameters, no discernible differences were seen between TRP and CRP UDMA simulations at equal conversions, although clear differences exist as a function of conversion. Both findings are consistent with experiments. Despite a number of shortcomings, these models have demonstrated the potential of molecular simulations for studying network topology in these systems.« less

Tunable, Quantitative Fenton-RAFT Polymerization via Metered Reagent Addition.

PubMed

Nothling, Mitchell D; McKenzie, Thomas G; Reyhani, Amin; Qiao, Greg G

2018-05-10

A continuous supply of radical species is a key requirement for activating chain growth and accessing quantitative monomer conversions in reversible addition-fragmentation chain transfer (RAFT) polymerization. In Fenton-RAFT, activation is provided by hydroxyl radicals, whose indiscriminate reactivity and short-lived nature poses a challenge to accessing extended polymerization times and quantitative monomer conversions. Here, an alternative Fenton-RAFT procedure is presented, whereby radical generation can be finely controlled via metered dosing of a component of the Fenton redox reaction (H 2 O 2 ) using an external pumping system. By limiting the instantaneous flux of radicals and ensuring sustained radical generation over tunable time periods, metered reagent addition reduces unwanted radical "wasting" reactions and provides access to consistent quantitative monomer conversions with high chain-end fidelity. Fine tuning of radical concentration during polymerization is achieved simply via adjustment of reagent dose rate, offering significant potential for automation. This modular strategy holds promise for extending traditional RAFT initiation toward more tightly regulated radical concentration profiles and affords excellent prospects for the automation of Fenton-RAFT polymerization. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Step Transfer-Addition and Radical-Termination (START) Polymerization of α,ω-Unconjugated Dienes under Irradiation of Blue LED Light.

PubMed

Xu, Tianchi; Yin, Hongnan; Li, Xiaohong; Zhang, Lifen; Cheng, Zhenping; Zhu, Xiulin

2017-07-01

A new polymerization method, termed as step transfer-addition and radical-termination, is developed for the step-growth radical polymerization of α,ω-unconjugated dienes under irradiation of visible light at room temperature (25 °C) for the first time. α,ω-Diiodoperfluoroalkane monomers (signified as A) are added onto α,ω-unconjugated dienes (signified as B) alternatively and efficiently with the generation of perfluorocarbon-containing alternating copolymers (AB) n . Based on the combined analyses of polymerization kinetics and NMR spectra ( 1 H and 19 F), the mechanism of the novel polymerization method, including the side reaction, is proposed. This novel polymerization method provides a new strategy not only for the step-growth radical polymerization of α,ω-unconjugated dienes but also for the construction of high molecular weight perfluorocarbon-containing alternating copolymers. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Copper-mediated homogeneous living radical polymerization of acrylamide with waxy potato starch-based macroinitiator.

PubMed

Fan, Yifei; Cao, Huatang; van Mastrigt, Frank; Pei, Yutao; Picchioni, Francesco

2018-07-15

Cu 0 -mediated living radical polymerization (Cu 0 -mediated LRP) was employed in this research for the synthesis of starch-g-polyacrylamide (St-g-PAM). The use of a controlled radical grafting technique is necessary, as compared to the traditional free-radical polymerization methods, in order to obtain a well-defined structure of the final product. This is in turn essential for studying the relationship between such structure and the end-properties. Waxy potato starch-based water-soluble macroinitiator was first synthesized by esterification with 2-bromopropionyl bromide in the mixture of dimethylacetamide and lithium chloride. With the obtained macroinitiator, St-g-PAM was homogeneously synthesized by aqueous Cu 0 -mediated LRP using CuBr/hexamethylated tris(2-aminoethyl)amine (Me 6 Tren) as catalyst. The successful synthesis of the macroinitiator and St-g-PAM was proved by NMR, FT-IR, SEM, XRD and TGA analysis. The molecular weight and polydispersity of PAM chains were analyzed by gel permeation chromatography (GPC) after hydrolyzing the starch backbone. Monomer conversion was monitored by gas chromatography (GC), on the basis of which the kinetics were determined. A preliminarily rheological study was performed on aqueous solutions of the prepared materials. Copyright © 2018 Elsevier Ltd. All rights reserved.

In Situ Monitoring of RAFT Polymerization by Tetraphenylethylene-Containing Agents with Aggregation-Induced Emission Characteristics.

PubMed

Liu, Shunjie; Cheng, Yanhua; Zhang, Haoke; Qiu, Zijie; Kwok, Ryan T K; Lam, Jacky W Y; Tang, Ben Zhong

2018-05-22

A facile and efficient approach is demonstrated to visualize the polymerization in situ. A group of tetraphenylethylene (TPE)-containing dithiocarbamates were synthesized and screened as agents for reversible addition fragmentation chain transfer (RAFT) polymerizations. The spatial-temporal control characteristics of photochemistry enabled the RAFT polymerizations to be ON and OFF on demand under alternating visible light irradiation. The emission of TPE is sensitive to the local viscosity change owing to its aggregation-induced emission characteristic. Quantitative information could be easily acquired by the naked eye without destroying the reaction system. Furthermore, the versatility of such a technique was well demonstrated by 12 different polymerization systems. The present approach thus demonstrated a powerful platform for understanding the controlled living radical polymerization process. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of nanosized (<20 nm) polymer particles by radical polymerization in miniemulsion employing in situ surfactant formation.

PubMed

Guo, Yi; Zetterlund, Per B

2011-10-18

A novel method for synthesis of ultrafine polymeric nanoparticles of diameters less than 20 nm has been developed. The method is based on miniemulsion polymerization exploiting combination of the in situ surfactant generation approach (whereby the surfactant is formed at the oil-water interface by reaction between an organic acid and a base) and ultrasonication. Conventional radical polymerization and nitroxide-mediated radical polymerization of styrene have been conducted in miniemulsion using oleic acid/potassium hydroxide, demonstrating that particles with diameters less than 20 nm can be obtained by this approach at surfactant contents much lower than traditionally required in microemulsion polymerizations. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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).

Ion-Molecule Association in Acrylonitrile

NASA Technical Reports Server (NTRS)

Wilson, Paul F.; Milligan, Daniel B.; McEwan, Murray J.

1997-01-01

Acrylonitrile (propernenitrile or vinyl cyanide) polymerizes readily via a radical mechanism in solution at room temparature. The propensity to polymerize is sufficiently strong that it is usual to add a radical scavenger to the solution to prevent polymerization when oxygen (an inhibitor) is removed. Polymerization of acrylonitrile is also know to occur via nucleophilic addition of an anion by a michael-type reaction.

ATOM TRANSFER RADICAL POLYMERIZATION OF N-BUTYL METHACRYLATE IN AQUEOUS DISPERSED SYSTEMS: A MINIEMULSION APPROACH. (R826735)

EPA Science Inventory

Ultrasonication was applied in combination with a hydrophobe for the copper-mediated atom transfer radical polymerization of n-butyl methacrylate in an aqueous dispersed system. A controlled polymerization was successfully achieved, as demonstrated by a linear correlation between...

High fluorescence emission silver nano particles coated with poly (styrene-g-soybean oil) graft copolymers: Antibacterial activity and polymerization kinetics.

PubMed

Hazer, Baki; Kalaycı, Özlem A

2017-05-01

Autoxidation of poly unsaturated fatty acids makes negative effect on foods. In this work, this negative effect was turned to a great advantage using autoxidized soybean oil as a macroperoxide nanocomposite initiator containing silver nano particles in free radical polymerization of vinyl monomers. The synthesis of soybean oil macro peroxide was carried out by exposing soybean oil to air oxygen with the presence of silver nanoparticles (Ag NPs) at room temperature. Autoxidized soybean oil macroperoxide containing silver nanoparticles (Agsbox) successfully initiated the free radical polymerization of styrene in order to obtain Polystyrene (PS)-g-soybean oil graft copolymer containing Ag NPs. Both autoxidized soybean oil and PS-g-sbox with Ag NPs showed a surface plasmon resonance and high fluorescence emission. Overall rate constant (K) of styrene polymerization initiated by autoxidized soybean oil macroperoxide with Ag NPs was found to be K=1.95.10 -4 Lmol -1 s -1 at 95°C. Antibacterial efficiency was observed in the PS-g-soybean oil graft copolymer film samples containing Ag NPs. 1 H NMR and GPC techniques were used for the structural analysis of the fractionated polymeric oils. Copyright © 2016 Elsevier B.V. All rights reserved.

Analyses and comparison of a novel, hybrid, multifunctional orthopedic composite and implant

NASA Astrophysics Data System (ADS)

Dicicco, Michael

In the orthopedic/medical device industry, 2, 2' -bis-(4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (Bis-GMA)- and diurethanedimethacrylate (DUDMA)-based polymeric biomaterials have become well-known substitutes for polymethylmethacrylate (PMMA)- and ultra-high molecular weight polyethylene (UHMWPE)-based biomaterials, respectively. The development of these polymeric biomaterials cannot continue without direct comparison studies against currently marketed materials. The initiative for this research stems wholly from developing analytical methodologies that assist in qualifying novel biomaterials under development, by evaluating their chemical properties, performance, and safety. The goals of this research were: (i) Characterize the assay/quality of every resin component and quantify elution of extractable monomers from novel, DUDMA-based RHAKOSS(TM) implant, (ii) Determine degree of conversion (alpha) and rate of polymerization (Rp) for novel, Bis-GMA-based CORTOSS(TM) composite, (iii) Assess risk for radical-induced post-surgical cytotoxicity for CORTOSS, (iv) Determine if surface radical chemistries occur for sterilized RHAKOSS and assess its oxidative stability, and (v) Quantify antibiotic elution from antibiotic-impregnated CORTOSS and identify factors that control elution. The phenomena studied necessitated the utilization of several analytical spectroscopic techniques; fluorometry, differential scanning calorimetry (DSC), electron paramagnetic resonance (EPR), ultraviolet-visible (UV-VIS), attenuated total reflectance---Fourier-transform infrared (ATR-FTIR), and high performance liquid chromatography (HPLC). A battery of lateral chemical techniques were employed as well; including molecular derivatization/tagging, phase partitioning, spin-trapping, and thermal annealing. Results demonstrated that RHAKOSS monomer percent compositions were prepared according to formulations and monomer elution was virtually undetectable, serving as an empirical gauge to portend degree of polymerization (DOP). A high alpha was reported for CORTOSS and essentially all bifunctional monomers had at least one functional group polymerized, stressing low monomer elution potential. Regarding cytotoxicity, CORTOSS impeded further production of hydroxyl radicals (•OH), whereas RHAKOSS did not facilitate the Fenton reaction but displayed some chelating abilities. Residual radicals in RHAKOSS were easily terminated, thus not projected to form oxidative degradants. Additionally, significant antibiotic concentrations, over extended durations, eluted from CORTOSS in linear-type fashion, advocating a sustained therapeutic effect, and phase partitioning correlated antibiotic release to hydrophilicity. The incurred data comprehensively argues in favor of the excellent biocompatibility that CORTOSS and RHAKOSS inherently possess, and was definitive in rendering them as advanced biomaterials, possessing favorable chemical properties.

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.

Hydrolyzable Poly[Poly(Ethylene Glycol) Methyl Ether Acrylate]-Colistin Prodrugs through Copper-Mediated Photoinduced Living Radical Polymerization.

PubMed

Zhu, Chongyu; Schneider, Elena K; Nikolaou, Vasiliki; Klein, Tobias; Li, Jian; Davis, Thomas P; Whittaker, Michael R; Wilson, Paul; Kempe, Kristian; Velkov, Tony; Haddleton, David M

2017-07-19

Through the recently developed copper-mediated photoinduced living radical polymerization (CP-LRP), a novel and well-defined polymeric prodrug of the antimicrobial lipopeptide colistin has been developed. A colistin initiator (Boc 5 -col-Br 2 ) was synthesized through the modification of colistin on both of its threonine residues using a cleavable initiator linker, 2-(2-bromo-2-methylpropanoyloxy) acetic acid (BMPAA), and used for the polymerization of acrylates via CP-LRP. Polymerization proceeds from both sites of the colistin initiator, and through the polymerization of poly(ethylene glycol) methyl ether acrylate (PEGA 480 ), three water-soluble polymer-colistin conjugates (col-PPEGA, having degrees of polymerization of 5, 10, and 20) were achieved with high yield (conversion of ≥93%) and narrow dispersities (Đ < 1.3) in 2-4 h. Little or no effect on the structure and activity of the colistin was observed during the synthesis, and most of the active colistin can be recovered from the conjugates in vitro within 2 days. Furthermore, in vitro biological analyses including disk diffusion, broth microdilution, and time-kill studies suggested that all of the conjugates have the ability to inhibit the growth of multidrug-resistant (MDR) Gram-negative bacteria, of which col-PPEGA DP5 and DP10 showed similar or better antibacterial performance compared to the clinically relevant colistin prodrug CMS, indicating their potential as an alternative antimicrobial therapy. Moreover, considering the control over the polymerization, the CP-LRP technique has the potential to provide an alternative platform for the development of polymer bioconjugates.

Near-Infrared Free-Radical and Free-Radical-Promoted Cationic Photopolymerizations by In-Source Lighting Using Upconverting Glass.

PubMed

Kocaarslan, Azra; Tabanli, Sevcan; Eryurek, Gonul; Yagci, Yusuf

2017-11-13

A method is presented for the initiation of free-radical and free-radical-promoted cationic photopolymerizations by in-source lighting in the near-infrared (NIR) region using upconverting glass (UCG). This approach utilizes laser irradiation of UCG at 975 nm in the presence of fluorescein (FL) and pentamethyldiethylene triamine (PMDETA). FL excited by light emitted from the UCG undergoes electron-transfer reactions with PMDETA to form free radicals capable of initiating polymerization of methyl methacrylate. To execute the corresponding free-radical-promoted cationic polymerization of cyclohexene oxide, isobutyl vinyl ether, and N-vinyl carbazole, it was necessary to use FL, dimethyl aniline (DMA), and diphenyliodonium hexafluorophosphate as sensitizer, coinitiator, and oxidant, respectively. Iodonium ions promptly oxidize DMA radicals formed to the corresponding cations. Thus, cationic polymerization with efficiency comparable to the conventional irradiation source was achieved. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Radical molecule and ion-molecule mechanisms in the polymerization of hydrocarbons and chlorosilanes in R.F. plasmas at low pressures (below 1.0 Torr)

NASA Technical Reports Server (NTRS)

Avni, R.; Carmi, U.; Inspektor, A.; Rosenthal, I.

1984-01-01

The ion-molecule and the radical-molecule mechanisms are responsible for the dissociation of hydrocarbons, and chlorosilane monomers and the formation of polymerized species, respectively, in the plasma state of a RF discharge. In the plasma, of a mixture of monomer with Ar, the rate determining step for both dissociation and polymerization is governed by an ion-molecular type interaction. Additions of H2 or NH3 to the monomer Ar(+) mixture transforms the rate determining step from an ion-molecular interaction to a radical-molecule type interaction for both monomer dissociation and polymerization processes.

Radical and ion molecule mechanisms in the polymerization of hydrocarbons and chlorosilanes in RF plasmas at low pressures ( 1.0 torr)

NASA Technical Reports Server (NTRS)

Avni, R.; Carmi, U.; Inspektor, A.; Rosenthal, I.

1984-01-01

The ion-molecule and the radical-molecule mechanisms are responsible for the dissociation of hydrocarbons, and chlorosilane monomers and the formation of polymerized species, respectively, in the plasma state of a RF discharge. In the plasma, of a mixture of monomer with Ar, the rate determining step for both dissociation and polymerization is governed by an ion-molecular type interaction. Additions of H2 or NH3 to the monomer Ar(+) mixture transforms the rate determining step from an ion-molecular interaction to a radical-molecule type interaction for both monomer dissociation and polymerization processes.

Protein-Polymer Conjugates: Synthetic Approaches by Controlled Radical Polymerizations & Interesting Applications

PubMed Central

Grover, Gregory N.; Maynard, Heather D.

2011-01-01

Protein-polymer conjugates are of interest to researchers in diverse fields. Attachment of polymers to proteins results in improved pharmacokinetics, which is important in medicine. From an engineering standpoint, conjugates are exciting because they exhibit properties of both the biomolecules and synthetic polymers. This allows the activity of the protein to be altered or tuned, a key aspect in therapeutic design, anchoring conjugates to surfaces, and utilizing these materials for supramolecular self-assembly. Thus, there is broad interest in straightforward synthetic methods to make protein-polymer conjugates. Controlled radical polymerization (CRP) techniques have emerged as excellent strategies to make conjugates because the resulting polymers have narrow molecular weight distributions, targeted molecular weights, and attach to specific sites on proteins. Herein, recent advances in the synthesis and application of protein-polymer conjugates by CRP are highlighted. PMID:21071260

Photoinitiated polymerization of 1-vinylimidazole

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

Joshi, M.G.; Rodriguez, F.

1984-04-01

The photoinitiated polymerization of 1-vinylimidazole (VI) does not follow the classical kinetic scheme for free radical polymerization. Kinetic results for VI suggest a degradative addition reaction between the macroradical and the monomer to produce a relatively stable, unreactive radical, which does not reinitiate polymerization, is low, 1.5 kcal/mol. Among the 3 photoinitiators used, the highest quantum efficiency was demonstrated by 2,2'-diethoxyacetophenone followed by bezoin methyl ether and benzoin isopropyl ether. Under the experimental conditions used, the polymerization of VI does not proceed to complete conversion, and the phenomenon of dead-end polymerization is observed.

A Self-Reporting Photocatalyst for Online Fluorescence Monitoring of High Throughput RAFT Polymerization.

PubMed

Yeow, Jonathan; Joshi, Sanket; Chapman, Robert; Boyer, Cyrille Andre Jean Marie

2018-04-25

Translating controlled/living radical polymerization (CLRP) from batch to the high throughput production of polymer libraries presents several challenges in terms of both polymer synthesis and characterization. Although recently there have been significant advances in the field of low volume, high throughput CLRP, techniques able to simultaneously monitor multiple polymerizations in an "online" manner have not yet been developed. Here, we report our discovery that 5,10,15,20-tetraphenyl-21H,23H-porphine zinc (ZnTPP) is a self-reporting photocatalyst that can mediate PET-RAFT polymerization as well as report on monomer conversion via changes in its fluorescence properties. This enables the use of a microplate reader to conduct high throughput "online" monitoring of PET-RAFT polymerizations performed directly in 384-well, low volume microtiter plates. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Well-Defined High Molecular Weight Polystyrene with High Rates and High Livingness Synthesized via Two-Stage RAFT Emulsion Polymerization.

PubMed

Yan, Kun; Gao, Xiang; Luo, Yingwu

2015-07-01

A highly living polymer with over 100 kg mol(-1) molecular weight is very difficult to achieve by controlled radical polymerization since the unavoidable side reactions of irreversible radical termination and radical chain transfer to monomer reaction become significant. It is reported that over 500 kg mol(-1) polystyrene with high livingness and low dispersity could be synthesized by a facile two-stage reversible addition-fragmentation transfer emulsion polymerization. The monomer conversion reaches 90% within 10 h. High livingness of the product is ascribed to the extremely low initiator concentration and the chain transfer constant for monomer unexpectedly much lower than the well-accepted values in the conventional radical polymerization. The two-stage monomer feeding policy much decreases the dispersity of the product. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanism of Cyclic Dye Regeneration During Eosin-Sensitized Photoinitiation in the Presence of Polymerization Inhibitors

PubMed Central

Avens, Heather J.; Bowman, Christopher N.

2009-01-01

A visible light photoinitiator, eosin, in combination with a tertiary amine coinitiator is found to initiate polymerization despite the presence of at least 1000-fold excess dissolved oxygen which functions as an inhibitor of radical polymerizations. Additionally, 0.4 µM eosin is able to overcome 100-fold excess (40 µM) 2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMPO) inhibitor, initiating polymerization after only a 2 minute inhibition period. In contrast, 40 µM Irgacure-2959, a standard cleavage-type initiator, is unable to overcome even an equivalent amount of inhibitor (40 µM TEMPO). Through additional comparisons of these two initiation systems, a reaction mechanism is developed which is consistent with the kinetic data and provides an explanation for eosin’s relative insensitivity to oxygen, TEMPO and other inhibitors. A cyclic mechanism is proposed in which semi-reduced eosin radicals react by disproportionation with radical inhibitors and radical intermediates in the inhibition process to regenerate eosin and effectively consume inhibitor. In behavior similar to that of eosin, rose bengal, fluorescein, and riboflavin are also found to initiate polymerization despite the presence of excess TEMPO, indicating that cyclic regeneration likely enhances the photoinitiation kinetics of many dye photosensitizers. Selection of such dye initiation systems constitutes a valuable strategy for alleviating inhibitory effects in radical polymerizations. PMID:20098667

Photonic devices based on patterning by two photon induced polymerization techniques

NASA Astrophysics Data System (ADS)

Fortunati, I.; Dainese, T.; Signorini, R.; Bozio, R.; Tagliazucca, V.; Dirè, S.; Lemercier, G.; Mulatier, J.-C.; Andraud, C.; Schiavuta, P.; Rinaldi, A.; Licoccia, S.; Bottazzo, J.; Franco Perez, A.; Guglielmi, M.; Brusatin, G.

2008-04-01

Two and three dimensional structures with micron and submicron resolution have been achieved in commercial resists, polymeric materials and sol-gel materials by several lithographic techniques. In this context, silicon-based sol-gel materials are particularly interesting because of their versatility, chemical and thermal stability, amount of embeddable active compounds. Compared with other micro- and nano-fabrication schemes, the Two Photon Induced Polymerization is unique in its 3D processing capability. The photopolymerization is performed with laser beam in the near-IR region, where samples show less absorption and less scattering, giving rise to a deeper penetration of the light. The use of ultrashort laser pulses allows the starting of nonlinear processes like multiphoton absorption at relatively low average power without thermally damaging the samples. In this work we report results on the photopolymerization process in hybrid organic-inorganic films based photopolymerizable methacrylate-containing Si-nanobuilding blocks. Films, obtained through sol-gel synthesis, are doped with a photo-initiator allowing a radical polymerization of methacrylic groups. The photo-initiator is activated by femtosecond laser source, at different input energies. The development of the unexposed regions is performed with a suitable solvent and the photopolymerized structures are characterized by microscopy techniques.

Nanoporous thermosetting polymers.

PubMed

Raman, Vijay I; Palmese, Giuseppe R

2005-02-15

Potential applications of nanoporous thermosetting polymers include polyelectrolytes in fuel cells, separation membranes, adsorption media, and sensors. Design of nanoporous polymers for such applications entails controlling permeability by tailoring pore size, structure, and interface chemistry. Nanoporous thermosetting polymers are often synthesized via free radical mechanisms using solvents that phase separate during polymerization. In this work, a novel technique for the synthesis of nanoporous thermosets is presented that is based on the reactive encapsulation of an inert solvent using step-growth cross-linking polymerization without micro/macroscopic phase separation. The criteria for selecting such a monomer-polymer-solvent system are discussed based on FTIR analysis, observed micro/macroscopic phase separation, and thermodynamics of swelling. Investigation of resulting network pore structures by scanning electron microscopy (SEM) and small-angle X-ray scattering following extraction and supercritical drying using carbon dioxide showed that nanoporous polymeric materials with pore sizes ranging from 1 to 50 nm can be synthesized by varying the solvent content. The differences in the porous morphology of these materials compared to more common free radically polymerized analogues that exhibit phase separation were evident from SEM imaging. Furthermore, it was demonstrated that the chemical activity of the nanoporous materials obtained by our method could be tailored by grafting appropriate functional groups at the pore interface.

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.

Applicability of samarium(III) complexes for the role of luminescent molecular sensors for monitoring progress of photopolymerization processes and control of the thickness of polymer coatings

NASA Astrophysics Data System (ADS)

Topa, Monika; Ortyl, Joanna; Chachaj-Brekiesz, Anna; Kamińska-Borek, Iwona; Pilch, Maciej; Popielarz, Roman

2018-06-01

Applicability of 15 trivalent samarium complexes as novel luminescent probes for monitoring progress of photopolymerization processes or thickness of polymer coatings by the Fluorescence Probe Technique (FPT) was studied. Three groups of samarium(III) complexes were evaluated in cationic photopolymerization of triethylene glycol divinyl ether monomer (TEGDVE) and free-radical photopolymerization of trimethylolpropane triacrylate (TMPTA). The complexes were the derivatives of tris(4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionate)samarium(III), tris(4,4,4-trifluoro-1-phenyl-1,3-butanedionate)samarium(III) and tris(4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedionate)samarium(III), which were further coordinated with auxiliary ligands, such as 1,10-phenanthroline, triphenylphosphine oxide, tributylphosphine oxide and trioctylphosphine oxide. It has been found that most of the complexes studied are sensitive enough to be used as luminescent probes for monitoring progress of cationic photopolymerization of vinyl ether monomers over entire range of monomer conversions. In the case of free-radical polymerization processes, the samarium(III) complexes are not sensitive enough to changes of microviscosity and/or micropolarity of the medium, so they cannot be used to monitor progress of the polymerization. However, high stability of luminescence intensity of some of these complexes under free-radical polymerization conditions makes them good candidates for application as thickness sensors for polymer coatings prepared by free-radical photopolymerization. A quantitative relationship between a coating thickness and the luminescence intensity of the samarium(III) probes has been derived and verified experimentally within a broad range of the thicknesses.

Syntheses and Post-Polymerization Modifications of Well-Defined Styrenic Polymers Containing Three-Membered Heterocyclic Functionalities

NASA Astrophysics Data System (ADS)

McLeod, David Charles

Macromolecules that contain electrophilic moieties, such as benzyl halides, activated esters, and epoxides, will readily undergo efficient nucleophilic substitution reactions with a wide variety of compounds under mild conditions, and are therefore ideally suited to act as "universal" precursors to functional materials. Epoxide-containing polymers derived from the radical polymerization of commercially-available glycidyl methacrylate are often employed in this role; however, methacrylic polymers suffer from certain limitations as a result of the incorporated ester groups, which are not stabile in the presence of strong nucleophiles, acids, bases, or esterase enzymes. Styrenic polymers that do not contain labile carbonyl moieties are usually the precursors of choice when high chemical stability is desired in the end product, but the production of functional materials from epoxide-containing styrenic polymers is relatively unexplored. In this dissertation, improved methods were developed for synthesizing 4-vinylphenyloxirane (4VPO) and 4-vinylphenyl glycidyl ether (4VPGE), two of the better-known epoxide-containing styrenic monomers, in high-yield and purity. Well-defined, epoxide-containing styrenic polymers with targeted molecular weights, narrow molecular weight distributions, and controlled architectures (specifically, linear and star-shaped homopolymers, as well as linear block copolymers with styrene) were produced from 4VPO and 4VPGE for the first time using reversible-deactivation radical polymerization techniques, such as low-catalyst-concentration atom transfer radical polymerization (LCC ATRP) and reversible addition-fragmentation chain-transfer (RAFT) polymerization. The robust nature and utility of poly4VPO and poly4VPGE were then demonstrated by the efficient, ring-opening modification of the pendant epoxide groups with a structurally- and functionally-diverse array of alcohols under acidic conditions at ambient temperature. The macromolecular compositions, architectures, and thermal stabilities of the resulting ?-hydroxy ether-functionalized homopolymers were evaluated using NMR and FTIR spectroscopy, size exclusion chromatography, and thermal gravimetric analysis. Aziridines and thiiranes (saturated, three-membered heterocycles containing either a single nitrogen or sulfur atom, respectively) are also susceptible to nucleophilic ring-opening reactions, and functional materials derived from aziridine- or thiirane-containing polymers could potentially have many interesting properties as a result of their high amine or thiol content, such as the ability to form pH- or redox-responsive structures. The synthesis of polymers containing aziridines that are activated towards nucleophilic ring-opening by C-aryl and/or N-sulfonyl substituents is unprecedented in the literature. Efficient methods for synthesizing styrenic monomers that contain these highly-reactive functionalities, namely 2-(4-vinylphenyl)aziridine (VPA) and its sulfonyl-activated derivative, N-mesyl-2-(4-vinylphenyl)aziridine (NMVPA), were developed utilizing 4VPO as a starting material. VPA was polymerized under LCC ATRP and RAFT conditions, but these methods were ineffective at producing well-defined polymers due to side reactions between the aziridine groups and the polymerization mediating compounds. Nitroxide-mediated radical polymerization (NMRP) produced well-defined polyVPA at low to moderate conversions of monomer, but cross-linking side reactions were evident at higher monomer conversions. Nearly all undesirable side reactions were prevented by attaching a mesyl group to the aziridine nitrogen atom, and well-defined polyNMVPA was realized under RAFT and NMRP conditions. Under ATRP conditions, reactions between the aziridine groups and catalyst still occurred, so the polymerization of NMVPA was not controlled using this technique. The synthesis of thiirane-containing styrenic polymers from either 2-(4-vinylphenyl)thiirane (VPT) or 2-((4-vinylphenoxy)methyl)thiirane (VPOMT), which were produced in a facile manner from 4VPO or 4VPGE, respectively, was attempted under conventional radical polymerization and RAFT polymerization conditions. Rapid desulfurization or ring-opening polymerization of VPT occurred when elevated temperatures or UV radiation was applied to reactions containing this monomer. The more-stable VPOMT monomer was successfully polymerized at elevated temperatures using thermally-labile azo-type initiators, and, under RAFT conditions, polymers of VPOMT increased in molecular weight as higher conversions of monomer were reached; however, the polymers produced under RAFT conditions were ill-defined and eventually underwent macrogelation, due to cross-linking side reactions of the thiirane moieties.

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.

A guide to the synthesis of block copolymers using reversible-addition fragmentation chain transfer (RAFT) polymerization.

PubMed

Keddie, Daniel J

2014-01-21

The discovery of reversible-deactivation radical polymerization (RDRP) has provided an avenue for the synthesis of a vast array of polymers with a rich variety of functionality and architecture. The preparation of block copolymers has received significant focus in this burgeoning research field, due to their diverse properties and potential in a wide range of research environments. This tutorial review will address the important concepts behind the design and synthesis of block copolymers using reversible addition-fragmentation chain transfer (RAFT) polymerization. RAFT polymerization is arguably the most versatile of the RDRP methods due to its compatibility with a wide range of functional monomers and reaction media along with its relative ease of use. With an ever increasing array of researchers that possess a variety of backgrounds now turning to RDRP, and RAFT in particular, to prepare their required polymeric materials, it is pertinent to discuss the important points which enable the preparation of high purity functional block copolymers with targeted molar mass and narrow molar mass distribution using RAFT polymerization. The key principles of appropriate RAFT agent selection, the order of monomer addition in block synthesis and potential issues with maintaining high end-group fidelity are addressed. Additionally, techniques which allow block copolymers to be accessed using a combination of RAFT polymerization and complementary techniques are touched upon.

The role of living/controlled radical polymerization in the formation of improved imprinted polymers.

PubMed

Salian, Vishal D; Vaughan, Asa D; Byrne, Mark E

2012-06-01

In this work, living/controlled radical polymerization (LRP) is compared with conventional free radical polymerization in the creation of highly and weakly cross-linked imprinted poly(methacrylic acid-co-ethylene glycol dimethacrylate) networks. It elucidates, for the first time, the effect of LRP on the chain level and begins to explain why the efficiency of the imprinting process is improved using LRP. Imprinted polymers produced via LRP exhibited significantly higher template affinity and capacity compared with polymers prepared using conventional methods. The use of LRP in the creation of highly cross-linked imprinted polymers resulted in a fourfold increase in binding capacity without a decrease in affinity; whereas weakly cross-linked gels demonstrated a nearly threefold increase in binding capacity at equivalent affinity when LRP was used. In addition, by adjusting the double bond conversion, we can choose to increase either the capacity or the affinity in highly cross-linked imprinted polymers, thus allowing the creation of imprinted polymers with tailorable binding parameters. Using free radical polymerization in the creation of polymer chains, as the template-monomer ratio increased, the average molecular weight of the polymer chains decreased despite a slight increase in the double bond conversion. Thus, the polymer chains formed were shorter but greater in number. Using LRP neutralized the effect of the template. The addition of chain transfer agent resulted in slow, uniform, simultaneous chain growth, resulting in the formation of longer more monodisperse chains. Reaction analysis revealed that propagation time was extended threefold in the formation of highly cross-linked polymers when LRP techniques were used. This delayed the transition to the diffusion-controlled stage of the reaction, which in turn led to the observed enhanced binding properties, decreased polydispersity in the chains, and a more homogeneous macromolecular architecture. Copyright © 2012 John Wiley & Sons, Ltd.

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

Comparative study of the molecularly imprinted polymers prepared by reversible addition-fragmentation chain transfer "bulk" polymerization and traditional radical "bulk" polymerization.

PubMed

Ma, Yue; Pan, Guoqing; Zhang, Ying; Guo, Xianzhi; Zhang, Huiqi

2013-05-01

Bisphenol A (BPA) and propranolol-imprinted polymers have been prepared via both reversible addition-fragmentation chain transfer "bulk" polymerization (RAFTBP) and traditional radical "bulk" polymerization (TRBP) under similar reaction conditions, and their equilibrium binding properties were compared in detail for the first time. The chemical compositions, specific surface areas, equilibrium bindings, and selectivity of the obtained molecularly imprinted polymers (MIPs) were systematically characterized. The experimental results showed that the MIPs with molecular imprinting effects and quite fast binding kinetics could be readily prepared via RAFTBP, but they did not show improved template binding properties in comparison with those prepared via TRBP, which is in sharp contrast to many previous reports. This could be attributed to the heavily interrupted equilibrium between the dormant species and active radicals in the RAFT mechanism because of the occurrence of fast gelation during RAFTBP. The findings presented here strongly demonstrates that the application of controlled radical polymerizations (CRPs) in molecular imprinting does not always benefit the binding properties of the resultant MIPs, which is of significant importance for the rational use of CRPs in generating MIPs with improved properties. Copyright © 2013 John Wiley & Sons, Ltd.

Titanium Dioxide Photocatalytic Polymerization of Acrylamide for Gel Electrophoresis (TIPPAGE) of Proteins and Structural Identification by Mass Spectrometry

NASA Astrophysics Data System (ADS)

Zhang, Wenyang; Yuan, Zhiwei; Huang, Lulu; Kang, Jie; Jiang, Ruowei; Zhong, Hongying

2016-02-01

Polyacrylamide gel electrophoresis (PAGE) coupled with mass spectrometry has been well established for separating, identifying and quantifying protein mixtures from cell lines, tissues or other biological samples. The copolymerization process of acrylamide and bis-acrylamide is the key to mastering this powerful technique. In general, this is a vinyl addition reaction initiated by free radical-generating reagents such as ammonium persulfate (APS) and tetramethylethylenediamine (TEMED) under basic pH and degassing experimental condition. We report herein a photocatalytic polymerization approach that is based on photo-generated hydroxyl radicals with nanoparticles of titanium dioxide. It was shown that the polymerization process is greatly accelerated in acidic condition when ultraviolet light shots on the gel solution containing TiO2 nanoparticles without degassing. This feature makes it very useful in preparing Triton X-100 acid urea (TAU) gel that has been developed for separating basic proteins such as histones and variants in acidic experimental condition. Additionally, the presence of titanium dioxide in the gel not only improves mechanistic property of gels but also changes the migration pattern of different proteins that have different affinities to titanium dioxide.

Functional Degradable Polymers by Radical Ring-Opening Copolymerization of MDO and Vinyl Bromobutanoate: Synthesis, Degradability and Post-Polymerization Modification.

PubMed

Hedir, Guillaume G; Bell, Craig A; O'Reilly, Rachel K; Dove, Andrew P

2015-07-13

The synthesis of vinyl bromobutanoate (VBr), a new vinyl acetate monomer derivative obtained by the palladium-catalyzed vinyl exchange reaction between vinyl acetate (VAc) and 4-bromobutyric acid is reported. The homopolymerization of this new monomer using the RAFT/MADIX polymerization technique leads to the formation of novel well-defined and controlled polymers containing pendent bromine functional groups able to be modified via postpolymerization modification. Furthermore, the copolymerization of vinyl bromobutanoate with 2-methylene-1,3-dioxepane (MDO) was also performed to deliver a range of novel functional degradable copolymers, poly(MDO-co-VBr). The copolymer composition was shown to be able to be tuned to vary the amount of ester repeat units in the polymer backbone, and hence determine the degradability, while maintaining a control of the final copolymers' molar masses. The addition of functionalities via simple postpolymerization modifications such as azidation and the 1,3-dipolar cycloaddition of a PEG alkyne to an azide is also reported and proven by (1)H NMR spectroscopy, FTIR spectroscopy, and SEC analyses. These studies enable the formation of a novel class of hydrophilic functional degradable copolymers using versatile radical polymerization methods.

Titanium Dioxide Photocatalytic Polymerization of Acrylamide for Gel Electrophoresis (TIPPAGE) of Proteins and Structural Identification by Mass Spectrometry.

PubMed

Zhang, Wenyang; Yuan, Zhiwei; Huang, Lulu; Kang, Jie; Jiang, Ruowei; Zhong, Hongying

2016-02-11

Polyacrylamide gel electrophoresis (PAGE) coupled with mass spectrometry has been well established for separating, identifying and quantifying protein mixtures from cell lines, tissues or other biological samples. The copolymerization process of acrylamide and bis-acrylamide is the key to mastering this powerful technique. In general, this is a vinyl addition reaction initiated by free radical-generating reagents such as ammonium persulfate (APS) and tetramethylethylenediamine (TEMED) under basic pH and degassing experimental condition. We report herein a photocatalytic polymerization approach that is based on photo-generated hydroxyl radicals with nanoparticles of titanium dioxide. It was shown that the polymerization process is greatly accelerated in acidic condition when ultraviolet light shots on the gel solution containing TiO2 nanoparticles without degassing. This feature makes it very useful in preparing Triton X-100 acid urea (TAU) gel that has been developed for separating basic proteins such as histones and variants in acidic experimental condition. Additionally, the presence of titanium dioxide in the gel not only improves mechanistic property of gels but also changes the migration pattern of different proteins that have different affinities to titanium dioxide.

Titanium Dioxide Photocatalytic Polymerization of Acrylamide for Gel Electrophoresis (TIPPAGE) of Proteins and Structural Identification by Mass Spectrometry

PubMed Central

Zhang, Wenyang; Yuan, Zhiwei; Huang, Lulu; Kang, Jie; Jiang, Ruowei; Zhong, Hongying

2016-01-01

Polyacrylamide gel electrophoresis (PAGE) coupled with mass spectrometry has been well established for separating, identifying and quantifying protein mixtures from cell lines, tissues or other biological samples. The copolymerization process of acrylamide and bis-acrylamide is the key to mastering this powerful technique. In general, this is a vinyl addition reaction initiated by free radical-generating reagents such as ammonium persulfate (APS) and tetramethylethylenediamine (TEMED) under basic pH and degassing experimental condition. We report herein a photocatalytic polymerization approach that is based on photo-generated hydroxyl radicals with nanoparticles of titanium dioxide. It was shown that the polymerization process is greatly accelerated in acidic condition when ultraviolet light shots on the gel solution containing TiO2 nanoparticles without degassing. This feature makes it very useful in preparing Triton X-100 acid urea (TAU) gel that has been developed for separating basic proteins such as histones and variants in acidic experimental condition. Additionally, the presence of titanium dioxide in the gel not only improves mechanistic property of gels but also changes the migration pattern of different proteins that have different affinities to titanium dioxide. PMID:26865351

Antifouling coatings via plasma polymerization and atom transfer radical polymerization on thin film composite membranes for reverse osmosis

NASA Astrophysics Data System (ADS)

Hirsch, Ulrike; Ruehl, Marco; Teuscher, Nico; Heilmann, Andreas

2018-04-01

A major drawback to otherwise highly efficient membrane-based desalination techniques like reverse osmosis (RO) is the susceptibility of the membranes to biofouling. In this work, a combination of plasma activation, plasma bromination and surface-initiated atom transfer radical polymerization (si-ATRP) of hydrophilic and zwitterionic monomers, namely hydroxyethyl methacrylate (HEMA), 2-methacryloyloxyethyl phosphorylcholine (MPC) and [2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), was applied to generate non-specific, anti-adhesive coatings on thin film composite (TFC) membranes. The antifouling effect of the coatings was shown by short-time batch as well as long-time steady state cultivation experiments with the microorganism Pseudomonas fluorescens. It could be shown that plasma functionalization and polymerization is possible on delicate thin film composite membranes without restricting their filtration performance. All modified membranes showed an increased resistance towards the adhesion of Pseudomonas fluorescens. On average, the biofilm coverage was reduced by 51.4-12.6% (for HEMA, SBMA, and MPC), the highest reduction was monitored for MPC with a biofilm reduction by 85.4%. The hydrophilic coatings applied did not only suppress the adhesion of Pseudomonas fluorescens, but also significantly increase the permeate flux of the membranes relative to uncoated membranes. The stability of the coatings was however not ideal and will have to be improved for future commercial use.

Polar-Nonpolar Radical Copolymerization under Li+ Catalysis

DTIC Science & Technology

2008-09-21

bonds or aromatic rings. Thus, we propose that a transfer of a methyl radical from CB11Me12C to IB triggers a radical polymerization chain that yields ...b-PIB and the resulting CB11Me11 byproduct concurrently triggers a cationic polymerization chain that yields l-PIB terminated with a carborate anion...tetrahydrofuran and passed through a column of alumina about five times to remove the bulk of the catalyst. A Soxhlet apparatus was used to recover

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.

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

Tang, Mingyi; Xu, Xiaoyang, E-mail: xiaoyangxu2012@163.com; Wu, Tao

Highlights: • Graphene oxide (GO) was modified by chemical reactions to functionalized GO (FGO). • The FGOs and the GO were then subjected to in situ free radical polymerization. • Hydroxyl groups of GO were the most reactive grafting sites. - Abstract: Graphene oxide (GO) was modified using chemical reactions to obtain three types of functionalized GO sheets (FGO). The FGO sheets and the GO were then subjected to in situ free radical polymerization in order to study the grafting polymerization. The FGO and grafted-.FGO were analyzed with Fourier transform infrared spectroscopy, scanning electronic microscopy, thermo-gravimetric analysis (TGA) and X-raymore » photoelectron spectroscopy (XPS). The grafting percentages in the materials were calculated using the TGA and XPS results. The FGO sheets with different functional groups exhibited different grafting abilities, and hydroxyl groups were proven to be the most reactive grafting sites for the in situ free radical grafting polymerization of polyacrylamide.« less

Sieving polymer synthesis by reversible addition fragmentation chain transfer polymerization.

PubMed

Nai, Yi Heng; Jones, Roderick C; Breadmore, Michael C

2013-12-01

Replaceable sieving polymers are the fundamental component for high resolution nucleic acids separation in CE. The choice of polymer and its physical properties play significant roles in influencing separation performance. Recently, reversible addition fragmentation chain transfer (RAFT) polymerization has been shown to be a versatile polymerization technique capable of yielding well defined polymers previously unattainable by conventional free radical polymerization. In this study, a high molecular weight PDMA at 765 000 gmol-1 with a PDI of 1.55 was successfully synthesized with the use of chain transfer agent - 2-propionic acidyl butyl trithiocarbonate (PABTC) in a multi-step sequential RAFT polymerization approach. This study represents the first demonstration of RAFT polymerization for synthesizing polymers with the molecular weight range suitable for high resolution DNA separation in sieving electrophoresis. Adjustment of pH in the reaction was found to be crucial for the successful RAFT polymerization of high molecular weight polymer as the buffered condition minimizes the effect of hydrolysis and aminolysis commonly associated with trithiocarbonate chain transfer agents. The separation efficiency of PABTC-PDMA was found to have marginally superior separation performance compared to a commercial PDMA formulation, POP™-CAP, of similar molecular weight range.

Synthesis of ethylene-propylene rubber graft copolymers by borane approach

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

Chung, T.C.; Janvikul, W.; Bernard, R.

1994-01-01

This paper describes a new method to prepare graft copolymers which have an EP rubber backbone and several free radical polymerized polymers grafted thereto. The process involves hydroboration of commercial EPDM rubbers, such as poly(ethylene-co-propylene-co-1,4-hexadiene) and poly(ethylene-co-propylene-co-5-ethylidene-2-norbornene), with 9-borabicyclononane (9-BBN). The resulting secondary alkyl-9-BBN moieties in the EPDM copolymer were then exposed to oxygen in the presence of free radical polymerizable monomers. Under certain conditions, the selective autoxidation reaction of secondary alkyl-9-BBN took place to create desirable polymeric radicals which can in situ initiate free radical polymerization. High graft efficiency was observed with controllable copolymer compositions. The graft copolymer ofmore » EP-g-PMMA is used to show the chemistry as well as some of the physical properties.« less

Quantitative investigation of free radicals in bio-oil and their potential role in condensed-phase polymerization.

PubMed

Kim, Kwang Ho; Bai, Xianglan; Cady, Sarah; Gable, Preston; Brown, Robert C

2015-03-01

We report on the quantitative analysis of free radicals in bio-oils produced from pyrolysis of cellulose, organosolv lignin, and corn stover by EPR spectroscopy. Also, we investigated their potential role in condensed-phase polymerization. Bio-oils produced from lignin and cellulose show clear evidence of homolytic cleavage reactions during pyrolysis that produce free radicals. The concentration of free radicals in lignin bio-oil was 7.5×10(20)  spin g(-1), which was 375 and 138 times higher than free-radical concentrations in bio-oil from cellulose and corn stover. Pyrolytic lignin had the highest concentration in free radicals, which could be a combination of carbon-centered (benzyl radicals) and oxygen-centered (phenoxy radicals) organic species because they are delocalized in a π system. Free-radical concentrations did not change during accelerated aging tests despite increases in molecular weight of bio-oils, suggesting that free radicals in condensed bio-oils are stable. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Designing of fluorescent and magnetic imprinted polymer for rapid, selective and sensitive detection of imidacloprid via activators regenerated by the electron transfer-atom transfer radical polymerization (ARGET-ATRP) technique

NASA Astrophysics Data System (ADS)

Kumar, Sunil; Karfa, Paramita; Madhuri, Rashmi; Sharma, Prashant K.

2018-05-01

In this work, we report on a dual-behavior electrochemical/optical sensor for sensitive determination of Imidacloprid by fluorescent dye (fluorescein, FL) and imprinted polymer modified europium doped superparamagnetic iron oxide nanoparticles (FL@SPIONs@MIP). The imidacloprid (IMD)-imprinted polymer was directly synthesized on the Eu-SPIONs surface via Activators regenerated by the electron transfer-atom transfer radical polymerization (ARGET-ATRP) technique. Preparation, characterization and application of the prepared FL@SPIONs@MIP were systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), fluorescence spectroscopy and electrochemical techniques. The electrochemical experiments exhibited a remarkable selectivity of the prepared sensor towards IMD. Determination of IMD by the square wave stripping voltammetry method represented a wide linear range of 0.059-0.791 μg L-1 with a detection limit of 0.0125 μg L-1. In addition, the fluorescence method shows a linear range of 0.039-0.942 μg L-1 and LOD of 0.0108 μg L-1. The fluorescence property of prepared FL@SPIONs@MIP was used for rapid, on-spot but selective detection of IMD in real samples. The proposed electrode displayed excellent repeatability and long-term stability and was successfully applied for quantitative and trace level determination of IMD in several real samples.

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

Electron-transfer reactions in cyanine borate ion pairs: photopolymerization initiators sensitive to visible light

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

Chatterjee, S.; Gottschalk, P.; Davis, P.D.

1988-03-30

Photoinitiation of polymerization is a process of immense practical, economic, and theoretical importance. In typical examples the polymerization of an acrylate or styrene-derived monomer is initiated by irradiation of a sensitizer with ultraviolet light. The excited state of the sensitizer may dissociate directly to form active free radicals as in the case of the benzoin ethers, or it may first undergo a bimolecular electron-transfer reaction whose products initiate polymerization as is the case in the benzophenone-dimethylaniline system. Efforts to extend the range of useful photoinitiators of free-radical polymerization to the visible region of the spectrum have heretofore met with onlymore » modest success. These special initiators typically are sensitive only to blue light or suffer from thermal instability and have low quantum efficiencies. The authors report herein the discovery that triphenylalkylborate salts of cyanine dyes (Chart I) are photoinitiators of free-radical polymerization whose sensitivity throughout the entire visible spectral region is the result of a novel intra-ion-pair electron-transfer reaction.« less

Homogeneous reactions of hydrocarbons, silane, and chlorosilanes in radiofrequency plasmas at low pressures

NASA Technical Reports Server (NTRS)

Avni, R.; Carmi, U.; Inspektor, A.; Rosenthal, I.

1984-01-01

The ion-molecule and radical-molecule mechanisms are responsible for the dissociation of hydrocarbon, silane, and chlorosilane monomers and the formation of polymerized species, respectively, in an RF plasma discharge. In a plasma containing a mixture of monomer and argon the rate-determining step for both dissociation and polymerization is governed by an ion-molecule type of interaction. Adding hydrogen or ammonia to the monomer-argon mixture transforms the rate-determining step from an ion-molecule interaction to a radical-molecule interaction for both monomer dissociation and polymerization.

Self-Propagating Frontal Polymerization in Water at Ambient Pressure

NASA Technical Reports Server (NTRS)

Olten, Nesrin; Kraigsley, Alison; Ronney, Paul D.

2003-01-01

Advances in polymer chemistry have led to the development of monomers and initiation agents that enable propagating free-radical polymerization fronts to exist. These fronts are driven by the exothermicity of the polymerization reaction and the transport of heat from the polymerized product to the reactant monomer/solvent/initiator solution. The thermal energy transported to the reactant solution causes the initiator to decompose, yielding free radicals, which start the free radical polymerization process as discussed in recent reviews. The use of polymerization processes based on propagating fronts has numerous applications. Perhaps the most important of these is that it enables rapid curing of polymers without external heating since the polymerization process itself provides the high temperatures necessary to initiate and sustain polymerization. This process also enables more uniform curing of arbitrarily thick samples since it does not rely on heat transfer from an external source, which will necessarily cause the temperature history of the sample to vary with distance from the surface according to a diffusion-like process. Frontal polymerization also enables filling and sealing of structures having cavities of arbitrary shape without having to externally heat the structure. Water at atmospheric pressure is most convenient solvent to employ and the most important for practical applications (because of the cost and environmental issues associated with DMSO and other solvents). Nevertheless, to our knowledge, steady, self-propagating polymerization fronts have not been reported in water at atmospheric pressure. Currently, polymerization fronts require a high boiling point solvent (either water at high pressures or an alternative solvent such as dimethyl sulfoxide (DMSO) (boiling point 189 C at atmospheric pressure.) Early work on frontal polymerization, employed pressures up to 5000 atm in order to avoid boiling of the monomer/solvent/initiator solution. High boiling point solutions are needed because in order to produce a propagating front, a high front temperature is needed to produce sufficiently rapid decomposition of the free radical initiator and subsequent free radical polymerization and heat release at a rate faster than heat losses remove thermal energy from the system. (While the conduction heat loss rate increases linearly with temperature, the free radical initiator decomposition is a high activation energy process whose rate increases much more rapidly than linearly with temperature, thus as the temperature decreases, the ratio of heat loss to heat generation increases, eventually leading to extinction of the front if the temperature is too low.) In order to obtain atmospheric pressure frontal polymerization in water, it is necessary to identify a monomer/initiator combination that is water soluble and will not extinguish even when the peak temperature (T*) is less than 100 C. In this work acrylic acid (AA) was chosen as the monomer because is it one of the most reactive monomers and can polymerize readily at low temperatures even without initiators. Ammonium persulfate (AP) was chosen as the initiator because it decomposes readily at low temperatures, produces relatively few bubbles and is commercially available. The propagation rates and extinction conditions of the fronts are studied for a range of AA and AP concentrations. Small amounts of fumed silica powder (Cab-o-sil, Cabot Corporation) were added to the solutions to inhibit buoyancy induced convection in the solutions; future studies will investigate the effects of buoyant convection within the solutions.

Free Radical Addition Polymerization Kinetics without Steady-State Approximations: A Numerical Analysis for the Polymer, Physical, or Advanced Organic Chemistry Course

ERIC Educational Resources Information Center

Iler, H. Darrell; Brown, Amber; Landis, Amanda; Schimke, Greg; Peters, George

2014-01-01

A numerical analysis of the free radical addition polymerization system is described that provides those teaching polymer, physical, or advanced organic chemistry courses the opportunity to introduce students to numerical methods in the context of a simple but mathematically stiff chemical kinetic system. Numerical analysis can lead students to an…

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.

Test of the ``radical-like polymerization'' scheme in molecular dynamics on the behavior of polymers under shock loading

NASA Astrophysics Data System (ADS)

Lemarchand, Claire; Bousquet, David; Schnell, Benoît; Pineau, Nicolas

2017-06-01

The behavior of polymer melts under shock loading is a question attracting more and more attention because of applications such as polymer-bonded explosives, light-weight armor and civilian protective equipment, like sports and car equipment. Molecular dynamics (MD) simulations are a very good tool to characterize the microscopic response of the polymer to a shock wave. To do so, the initial configuration of the polymer melt needs to be realistic. The ``radical-like polymerization'' scheme is a method to obtain near equilibrium configurations of a melt of long polymer chains. It consists in adding one neighboring monomer at a time to each growing chain. Between each polymerization step an MD run is performed to relax the new configuration. We test how details of our implementation of the ``radical-like polymerization'' scheme can impact or not Hugoniot curves and changes of chain configuration under shock. We compare our results to other simulation and experimental results on reference polymers.

THE RADIATION-INDUCED POLYMERIZATION OF ISOBUTENE: A LIQUID PHASE IONIC REACTION

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

Collinson, E.; Dainton, F.S.; Gillis, H.A.

1959-06-01

New evidence is presented in support of the suggestion that the gamma - ray-induced polymerization of liquid isobutene at -78 deg C proceeds solely by a cationic mechanism. Attempts to polymerize isobutene at -78 deg C with free radicals from the photolysis of diacetyl, benzoin and benzil were unsuccessful but the benzil solution irradiated with ultraviolet light at 77 deg K was shown by electron spin resonance measurements to give rise to radicals from the isobutene. Isobutene irradiated in the pure state at a gamma -ray dose rate of 7 x 10/sup 17/ e.v. ml/sup -1/ min/sup -1/ polymerized withmore » G(-C/sub 4/H/sub 8/) = 3.0 plus or minus 1.7 x 10/sup 2/. Solutions of FeCl/sub 3/, DPPH, benzoquinone and iodine in isobutene were also irradiated with gamma -rays. Of these solutes, only benzoquinone reduced the polymerization rate to zero, and DPPH had no significant effect. The effects of FeCl/sub 3/ and I/2 on the polymerization were complicated by other factors. The measured yields of conversion of the solutes after irradiation were G(-DPPH) =3.7 plus or minus 0.2, G(Fe(II)) = 3.0 plus or minus 0.5 and G(-Q) = 1.5 plus or minus 0.2. The electron spin resonance spectrum of isobutene irradiated with gamma -rays at 77 deg K showed the presence of H atoms which disappeared rapidly, and a more stable radical, the spectrum of which consisted of 6 peaks having an over-all spacing of 158 gauss at the operating frequency of 9400 Mc sec./sup -1/. The same six peak pattern was obtained from cyclopropane irradiated with gamma rays at 77 deg K and from a solution of benzil in isoDutene irradiated with ultraviolet light at 77 deg K. It is concluded that the radical responsible for this spectrum is either the cyclopropyl radical or the methyl substituted allyl radical, the latter being the less likely. The most likely initiating ion is considered to be (CH/sub 3/)/sub 3/C/sup +/, and a mechanism consistent with the available data is proposed. (auth)« less

Synthesis and Biomedical Applications of Poly((meth)acrylic acid) Brushes.

PubMed

Qu, Zhenyuan; Xu, Hong; Gu, Hongchen

2015-07-15

Poly((meth)acrylic acid) (P(M)AA) brushes possess a number of distinctive properties that are particularly attractive for biomedical applications. This minireview summarizes recent advances in the synthesis and biomedical applications of P(M)AA brushes and brushes containing P(M)AA segments. First, we review different surface-initiated polymerization (SIP) methods, with a focus on recent progress in the surface-initiated controlled/living radical polymerization (SI-CLRP) techniques used to generate P(M)AA brushes with a tailored structure. Next, we discuss biomolecule immobilization methods for P(M)AA brushes, including physical adsorption, covalent binding, and affinity interactions. Finally, typical biomedical applications of P(M)AA brushes are reviewed, and their performance is discussed based on their unique properties. We conclude that P(M)AA brushes are promising biomaterials, and more potential biomedical applications are expected to emerge with the further development of synthetic techniques and increased understanding of their interactions with biological systems.

Novel polymeric materials from vegetable oils and vinyl monomers: preparation, properties, and applications.

PubMed

Lu, Yongshang; Larock, Richard C

2009-01-01

Veggie-based products: Vegetable-oil-based polymeric materials, prepared by free radical, cationic, and olefin metathesis polymerizations, range from soft rubbers to ductile or rigid plastics, and to high-performance biocomposites and nanocomposites. They display a wide range of thermophysical and mechanical properties and may find promising applications as alternatives to petroleum-based polymers.Vegetable oils are considered to be among the most promising renewable raw materials for polymers, because of their ready availability, inherent biodegradability, and their many versatile applications. Research on and development of vegetable oil based polymeric materials, including thermosetting resins, biocomposites, and nanocomposites, have attracted increasing attention in recent years. This Minireview focuses on the latest developments in the preparation, properties, and applications of vegetable oil based polymeric materials obtained by free radical, cationic, and olefin metathesis polymerizations. The novel vegetable oil based polymeric materials obtained range from soft rubbery materials to ductile or rigid plastics and to high-performance biocomposites and nanocomposites. These vegetable oil based polymeric materials display a wide range of thermophysical and mechanical properties and should find useful applications as alternatives to their petroleum-based counterparts.

Polymerization Initiated at the Sidewalls of Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Tour, James M.; Hudson, Jared L.

2011-01-01

A process has been developed for growing polymer chains via anionic, cationic, or radical polymerization from the side walls of functionalized carbon nanotubes, which will facilitate greater dispersion in polymer matrices, and will greatly enhance reinforcement ability in polymeric material.

Emergent Properties of Giant Vesicles Formed by a Polymerization-Induced Self-Assembly (PISA) Reaction

NASA Astrophysics Data System (ADS)

Albertsen, Anders N.; Szymański, Jan K.; Pérez-Mercader, Juan

2017-01-01

Giant micrometer sized vesicles are of obvious interest to the natural sciences as well as engineering, having potential application in fields ranging from drug delivery to synthetic biology. Their formation often requires elaborate experimental techniques and attempts to obtain giant vesicles from chemical media in a one-pot fashion have so far led to much smaller nanoscale structures. Here we show that a tailored medium undergoing controlled radical polymerization is capable of forming giant polymer vesicles. Using a protocol which allows for an aqueous reaction under mild conditions, we observe the macroscale consequences of amphiphilic polymer synthesis and the resulting molecular self-assembly using fluorescence microscopy. The polymerization process is photoinitiated by blue light granting complete control of the reaction, including on the microscope stage. The self-assembly process leads to giant vesicles with radii larger than 10 microns, exhibiting several emergent properties, including periodic growth and collapse as well as phototaxis.

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.

Copper mediated polymerization without external deoxygenation or oxygen scavengers.

PubMed

Liarou, Evelina; Whitfield, Richard; Anastasaki, Athina; Engelis, Nikolaos G; Jones, Glen R; Velonia, Kelly; Haddleton, David

2018-05-14

Overcoming the challenge of rigorous deoxygenation in copper mediated controlled radical polymerization processes (e.g. ATRP), we report a simple Cu(0)-RDRP system in the absence of external additives (e.g. reducing agents, enzymes etc.). By simply adjusting the headspace of the reaction vessel, a wide range of monomers, namely acrylates, methacrylates, acrylamides and styrene, can be polymerized in a controlled manner yielding polymers with low dispersities, near-quantitative conversions and high end group fidelity. Significantly, this approach is scalable (~ 125 g), tolerant to elevated temperatures, compatible with both organic and aqueous media and does not rely on external stimuli which may limit the monomer pool. The robustness and versatility of this methodology is further demonstrated by the applicability to a number of other copper mediated techniques including conventional ATRP and light-mediated approaches. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of micropatterned hydrogels for neural culture systems using dynamic mask projection photolithography.

PubMed

Curley, J Lowry; Jennings, Scott R; Moore, Michael J

2011-02-11

Increasingly, patterned cell culture environments are becoming a relevant technique to study cellular characteristics, and many researchers believe in the need for 3D environments to represent in vitro experiments which better mimic in vivo qualities. Studies in fields such as cancer research, neural engineering, cardiac physiology, and cell-matrix interaction have shown cell behavior differs substantially between traditional monolayer cultures and 3D constructs. Hydrogels are used as 3D environments because of their variety, versatility and ability to tailor molecular composition through functionalization. Numerous techniques exist for creation of constructs as cell-supportive matrices, including electrospinning, elastomer stamps, inkjet printing, additive photopatterning, static photomask projection-lithography, and dynamic mask microstereolithography. Unfortunately, these methods involve multiple production steps and/or equipment not readily adaptable to conventional cell and tissue culture methods. The technique employed in this protocol adapts the latter two methods, using a digital micromirror device (DMD) to create dynamic photomasks for crosslinking geometrically specific poly-(ethylene glycol) (PEG) hydrogels, induced through UV initiated free radical polymerization. The resulting "2.5D" structures provide a constrained 3D environment for neural growth. We employ a dual-hydrogel approach, where PEG serves as a cell-restrictive region supplying structure to an otherwise shapeless but cell-permissive self-assembling gel made from either Puramatrix or agarose. The process is a quick simple one step fabrication which is highly reproducible and easily adapted for use with conventional cell culture methods and substrates. Whole tissue explants, such as embryonic dorsal root ganglia (DRG), can be incorporated into the dual hydrogel constructs for experimental assays such as neurite outgrowth. Additionally, dissociated cells can be encapsulated in the photocrosslinkable or self polymerizing hydrogel, or selectively adhered to the permeable support membrane using cell-restrictive photopatterning. Using the DMD, we created hydrogel constructs up to ~1mm thick, but thin film (<200 μm) PEG structures were limited by oxygen quenching of the free radical polymerization reaction. We subsequently developed a technique utilizing a layer of oil above the polymerization liquid which allowed thin PEG structure polymerization. In this protocol, we describe the expeditious creation of 3D hydrogel systems for production of microfabricated neural cell and tissue cultures. The dual hydrogel constructs demonstrated herein represent versatile in vitro models that may prove useful for studies in neuroscience involving cell survival, migration, and/or neurite growth and guidance. Moreover, as the protocol can work for many types of hydrogels and cells, the potential applications are both varied and vast.

Radical Polymerization of Diene Hydrocarbons in a Presence of Peroxide of Hydrogen and Solvent. 1. Effectiveness of Initiation and Rate of Expansion H2O2 during Oligomerization in Metallic Equipment

DTIC Science & Technology

1990-04-10

the hydroxyl groups. These are liquid oligobutadienes of brand R-15M and R-45M (firm "Sinclair Retgochemical Suc."/OSA) [5, 6, 10] and hydroxyl... ionic mechanism. Most promising, in view of simplicity and cheapness, is considered the I DOC - 90010000 PAGE - method of the radical polymerization of...Initiators of polimerization in this method are the hydroxyl radicals, which are generated during the homolytic decomposition of peroxide of hydrogen PDO

The effect of polymerization mode on monomer conversion, free radical entrapment, and interaction with hydroxyapatite of commercial self-adhesive cements.

PubMed

D'Alpino, Paulo Henrique Perlatti; Silva, Marília Santos; Vismara, Marcus Vinícius Gonçalves; Di Hipólito, Vinicius; Miranda González, Alejandra Hortencia; de Oliveira Graeff, Carlos Frederico

2015-06-01

This study evaluated the degree of conversion, the free radical entrapment, and the chemical interaction of self-adhesive resin cements mixed with pure hydroxyapatite, as a function of the polymerization activation mode among a variety of commercial self-adhesive cements. Four cements (Embrace WetBond, MaxCem Elite, Bifix SE, and RelyX U200) were mixed, combined with hydroxyapatite, dispensed into molds, and distributed into three groups, according to polymerization protocols: IP (photoactivation for 40s); DP (delayed photoactivation, 10 min self-curing plus 40s light-activated); and CA (chemical activation, no light exposure). Infrared (IR) spectra were obtained and monomer conversion (%) was calculated by comparing the aliphatic-to-aromatic IR absorption peak ratio before and after polymerization (n=10). The free radical entrapment values of the resin cements were characterized using Electron Paramagnetic Resonance (EPR) and the concentration of spins (number of spins/mass) calculated (n=3). Values were compared using two-way ANOVA and Tukey's post-hoc test (α=5%). X-ray diffraction (XRD) characterized the crystallinity of hydroxyapatite as a function of the chemical interactions with the resin cements. The tested parameters varied as a function of resin cement and polymerization protocol. Embrace WetBond and RelyX U200 demonstrated dependence on photoactivation (immediate or delayed), whereas MaxCem Elite exhibited dependence on the chemical activation mode. Bifix SE presented the best balance based on the parameters analyzed, irrespective of the activation protocol. Choice of polymerization protocol affects the degree of conversion, free radical entrapment, and the chemical interaction between hydroxyapatite and self-adhesive resin cement mixtures. Copyright © 2015 Elsevier Ltd. All rights reserved.

Preparation and evaluation of a novel star-shaped polyacid-constructed dental glass-ionomer system.

PubMed

Howard, Leah; Weng, Yiming; Xie, Dong

2014-06-01

The objective of this study was to synthesize and characterize novel star-shaped poly(acrylic acid-co-itaconic acid)s via chain-transfer radical polymerization technique, use these polyacids to formulate the resin-modified glass-ionomer cements, and evaluate the mechanical strengths of the formed cements The star-shaped poly(acrylic acid-co-itaconic acid)s were synthesized via a chain-transfer radical polymerization reaction using a newly synthesized star-shaped chain-transfer agent. The effects of MW, GM-tethering ratio, P/L ratio and aging on the compressive properties of the formed experimental cements were studied. Compressive, diametral tensile as well as flexural strengths were evaluated and compared to those of Fuji II and Fuji II LC cements. The star-shaped polyacids showed significantly lower viscosities in water as compared to their linear counterparts. The cements formulated with these novel polyacids showed significantly improved mechanical strengths i.e., 49% in yield strength, 41% in modulus, 25% in CS, 20% in DTS and 36% in FS, higher than commercial Fuji II LC. After aging in water for 30 days, the compressive strengths of the experimental cements were significantly changed with an increase of 29% in YS, 19% in modulus as well as 23% in CS and a decrease of 5% in toughness, indicating that aging in water enhances the salt-bridge formation and increases brittleness. A novel light-cured glass-ionomer cement system composed of the star-shaped poly(carboxylic acid)s has been developed via a cost-effective and time-efficient chain-transfer radical polymerization. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

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.

Characterization of photochemical-cured acrylates with calorimetric methods

NASA Astrophysics Data System (ADS)

Strehmel, Bernd; Anwand, Dirk; Wetzel, Henrik

1994-05-01

Radical polymerization kinetics of different kinds of diacrylates was investigated in linear polymers (binders) by using an isoperibolic calorimeter. For all experiments benzoin compounds were added as photoinitiator. The ester between acrylic acid and bisphenol-A-diglycidylether (DDGDA) and hexamethylenediacrylate were used as monomers. Both compounds have a high limiting conversion and a large polymerization rate in the binders investigated. Additionally, three kinds of termination reaction were observed: first order, second order, and primary radical termination. The last reaction was mainly found in the case of using the hexamethylenediacrylate monomer. The materials were investigated by DSC to determine the phase behavior. Both monomers form one phase with the binder (polymethylmethacrylate, PMMA). In contrast, a phase separation was observed between the crosslinked hexamethylenediacrylate and PMMA. Formations of semi- interpenetrating networks were found in the case of crosslinked DDGDA and PMMA. The glass transition temperatures were determined at different polymerization degrees also. The obtained results indicate that most of the network formation occurred in the glassy state. Fluorescence probe technique was applied to study changes in the mobility during network formation. The fluorescence probe crystal violet (CV) was used because this compound shows a strong free volume-dependent fluorescence. It was found that in the glassy state, where most of networks were formed, a large variation of the molecular mobility was observed during irradiation of the photopolymers. This result was in agreement with the observations during DSC experiments.

Visible-Light Initiated Free-Radical/Cationic Ring-Opening Hybrid Photopolymerization of Methacrylate/Epoxy: Polymerization Kinetics, Crosslinking Structure, and Dynamic Mechanical Properties.

PubMed

Ge, Xueping; Ye, Qiang; Song, Linyong; Misra, Anil; Spencer, Paulette

2015-04-01

The effects of polymerization kinetics and chemical miscibility on the crosslinking structure and mechanical properties of polymers cured by visible-light initiated free-radical/cationic ring-opening hybrid photopolymerization are determined. A three-component initiator system is used and the monomer system contains methacrylates and epoxides. The photopolymerization kinetics is monitored in situ by Fourier transform infrared-attenuated total reflectance. The crosslinking structure is studied by modulated differential scanning calorimetry and dynamic mechanical analysis. X-ray microcomputed tomography is used to evaluate microphase separation. The mechanical properties of polymers formed by hybrid formed by free-radical polymerization. These investigations mark the first time that the benefits of the chain transfer reaction between epoxy and hydroxyl groups of methacrylate, on the crosslinking network and microphase separation during hybrid visible-light initiated photopolymerization, have been determined.

Radiation-induced polymerization of glass-forming systems. IV. Effect of the homogeneity of polymerization phase and polymer concentration on temperature dependence of initial polymerization rate

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

Kaetsu, I.; Ito, A.; Hayashi, K.

1973-06-01

The effect of homogeneity of polymerization phase and monomer concentration on the temperature dependence of initial polymerization rate was studied in the radiation-induced radical polymerization of binary systems consisting of glass-forming monomer and solvent. In the polymerization of a completely homogeneous system such as HEMA-propylene glycol, a maximum and a minimum in polymerization rates as a function of temperature, characteristic of the polymerization in glass-forming systems, were observed for all monomer concentrations. However, in the heterogeneous polymerization systems such as HEMA-triacetin and HEMAisoamyl acetate, maximum and minimum rates were observed in monomer-rich compositions but not at low monomer concentrations. Furthermore,more » in the HEMA-dioctyl phthalate polymerization system, which is extremely heterogeneous, no maximum and minimum rates were observed at any monomer concentration. The effect of conversion on the temperature dependence of polymerization rate in homogeneous bulk polymerization of HEMA and GMA was investigated. Maximum and minimum rates were observed clearly in conversions less than 10% in the case of HEMA and less than 50% in the case of GMA, but the maximum and minimum changed to a mere inflection in the curve at higher conversions. A similar effect of polymer concentration on the temperature dependence of polymerization rate in the GMA-poly(methyl methacrylate) system was also observed. It is deduced that the change in temperature dependence of polymerization rate is attributed to the decrease in contribution of mutual termination reaction of growing chain radicals to the polymerization rate. (auth)« less

Polymerization Simulator for Introductory Polymer and Material Science Courses

ERIC Educational Resources Information Center

Chirdon, William M.

2010-01-01

This work describes how molecular simulation of polymerization reactions can be used to enrich introductory polymer or material science courses to give students a deeper understanding of free-radical chain and stepwise growth polymerization reactions. These simulations have proven to be effective media for instruction that do not require material…

Methyleneation of peptides by N,N,N,N-tetramethylethylenediamine (TEMED) under conditions used for free radical polymerization: a mechanistic study.

PubMed

Shirangi, Mehrnoosh; Sastre Toraño, Javier; Sellergren, Börje; Hennink, Wim E; Somsen, Govert W; van Nostrum, Cornelus F

2015-01-21

Free radical polymerization is often used to prepare protein and peptide-loaded hydrogels for the design of controlled release systems and molecular imprinting materials. Peroxodisulfates (ammonium peroxodisulfates (APS) or potassium peroxodisulfates (KPS)) with N,N,N,N-tetramethylethylenediamine (TEMED) are frequently used as initiator and catalyst. However, exposure to these free radical polymerization reagents may lead to modification of the protein and peptide. In this work, we show the modification of lysine residues by ammonium peroxodisulfate (APS)/TEMED of the immunostimulant thymopentin (TP5). Parallel studies on a decapeptide and a library of 15 dipeptides were performed to reveal the mechanism of modification. LC-MS of APS/TEMED-exposed TP5 revealed a major reaction product with an increased mass (+12 Da) with respect to TP5. LC-MS(2) and LC-MS(3) were performed to obtain structural information on the modified peptide and localize the actual modification site. Interpretation of the obtained data demonstrates the formation of a methylene bridge between the lysine and arginine residue in the presence of TEMED, while replacing TEMED with a sodium bisulfite catalyst did not show this modification. Studies with the other peptides showed that the TEMED radical can induce methyleneation on peptides when lysine is next to arginine, proline, cysteine, aspargine, glutamine, histidine, tyrosine, tryptophan, and aspartic acid residues. Stability of peptides and protein needs to be considered when using APS/TEMED in in situ polymerization systems. The use of an alternative catalyst such as sodium bisulfite may preserve the chemical integrity of peptides during in situ polymerization.

Polymerization as a Model Chain Reaction

ERIC Educational Resources Information Center

Morton, Maurice

1973-01-01

Describes the features of the free radical, anionic, and cationic mechanisms of chain addition polymerization. Indicates that the nature of chain reactions can be best taught through the study of macromolecules. (CC)

Free-radical solution-polymerization of trifluoronitrosomethane with tetrafluoroethylene

NASA Technical Reports Server (NTRS)

Gdickman, S. A.

1972-01-01

Heavy-walled glass reactor, equipped with aerosol-compatible couplings and needle valve and charged with solvent and initiator, is utilized for polymerization. Polymer conversions and reactor/vessel operation are discussed.

Double-bond-containing polyallene-based triblock copolymers via phenoxyallene and (meth)acrylate

NASA Astrophysics Data System (ADS)

Ding, Aishun; Lu, Guolin; Guo, Hao; Huang, Xiaoyu

2017-03-01

A series of ABA triblock copolymers, consisting of double-bond-containing poly(phenoxyallene) (PPOA), poly(methyl methacrylate) (PMMA), or poly(butyl acrylate) (PBA) segments, were synthesized by sequential free radical polymerization and atom transfer radical polymerization (ATRP). A new bifunctional initiator bearing azo and halogen-containing ATRP initiating groups was first prepared followed by initiating conventional free radical homopolymerization of phenoxyallene with cumulated double bond to give a PPOA-based macroinitiator with ATRP initiating groups at both ends. Next, PMMA-b-PPOA-b-PMMA and PBA-b-PPOA-b-PBA triblock copolymers were synthesized by ATRP of methyl methacrylate and n-butyl acrylate initiated by the PPOA-based macroinitiator through the site transformation strategy. These double-bond-containing triblock copolymers are stable under UV irradiation and free radical circumstances.

Star-shaped Polymers through Simple Wavelength-Selective Free-Radical Photopolymerization.

PubMed

Eibel, Anna; Fast, David E; Sattelkow, Jürgen; Zalibera, Michal; Wang, Jieping; Huber, Alex; Müller, Georgina; Neshchadin, Dmytro; Dietliker, Kurt; Plank, Harald; Grützmacher, Hansjörg; Gescheidt, Georg

2017-11-06

Star-shaped polymers represent highly desired materials in nanotechnology and life sciences, including biomedical applications (e.g., diagnostic imaging, tissue engineering, and targeted drug delivery). Herein, we report a straightforward synthesis of wavelength-selective multifunctional photoinitiators (PIs) that contain a bisacylphosphane oxide (BAPO) group and an α-hydroxy ketone moiety within one molecule. By using three different wavelengths, these photoactive groups can be selectively addressed and activated, thereby allowing the synthesis of ABC-type miktoarm star polymers through a simple, highly selective, and robust free-radical polymerization method. The photochemistry of these new initiators and the feasibility of this concept were investigated in unprecedented detail by using various spectroscopic techniques. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

RAFT-Polymerization-Induced Self-Assembly and Reorganizations: Ultrahigh-Molecular-Weight Polymer and Morphology-Tunable Micro-/Nanoparticles in One Pot.

PubMed

Zhang, Xiao-Yun; Liu, Dong-Ming; Lv, Xin-Hu; Sun, Miao; Sun, Xiao-Li; Wan, Wen-Ming

2016-11-01

A one-pot method is introduced for the successful synthesis of narrow-distributed (Đ = 1.22) vinyl polymer with both ultrahigh molecular weight (UHMW) (M w = 1.31 × 10 6 g mol -1 ) and micro-/nanomorphology under mild conditions. The method involves the following four stages: homogeneous polymerization, polymerization-induced self-assembly (PISA), PISA and reorganization, and PISA and multiple reorganizations. The key points to the production of UHMW polystyrene are to minimize radical termination by segregating radicals in different nanoreactors and to ensure sufficient chain propagation by promoting further reorganizations of these reactors in situ. This method therefore endows polymeric materials with the outstanding properties of both UHMW and tunable micro-/nanoparticles under mild conditions in one pot. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

NMR, ESI/MS, and MALDI-TOF/MS analysis of pear juice polymeric proanthocyanidins with potent free radical scavenging activity.

PubMed

Es-Safi, Nour-Eddine; Guyot, Sylvain; Ducrot, Paul-Henri

2006-09-20

The structure of a polymeric proanthocyanidin fraction isolated from pear juice was characterized by NMR, ESI/MS, and MALDI-TOF/MS analyses, and its antioxidant activity was investigated using the DPPH free radical scavenging method. The results obtained from 13C NMR analysis showed the predominance of signals representative of procyanidins. Typical signals in the chemical shift region between 70 and 90 ppm demonstrated the exclusive presence of epicatechin units. The results obtained through negative ESI/MS analysis showed singly and doubly charged ions corresponding to the molecular mass of procyanidins with a degree of polymerization up to 22. The spectra obtained through MALDI-TOF/MS analysis revealed the presence of two series of tannin oligomers. Supporting the observations from NMR spectroscopy, the first series consists of well-resolved tannin identified as procyanidin polymers units with chain lengths of up to 25. A second series of monogalloyl flavan-3-ols polymers with polymerization degree up to 25 were also detected. This is the first mass spectrometric evidence confirming the existence of galloylated procyanidin oligomers in pear fruits. Within each of these oligomers, various signals exist suggesting the presence of several oligomeric tannins. The antioxidant properties of the polymeric fraction were investigated through reduction of the DPPH free radical, and the results obtained showed that the polymeric fraction exhibited a higher antioxidant power compared to those of (+)-catechin and B3 procyanidin dimer.

Preparation of poly(vinyl alcohol)/kaolinite nanocomposites via in situ polymerization

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

Jia Xin; Department of Chemistry, Hexi University, Zhangye 734000; Li Yanfeng

2008-03-04

Poly(vinyl alcohol)/kaolinite intercalated nanocomposites (Kao-PVA) were prepared via in situ intercalation radical polymerization. Vinyl acetate (VAc) was intercalated into kaolinite by a displacement method using dimethyl sulfoxide/kaolinite (Kao-DMSO) as the intermediate. Then, PVAc/kaolinite (Kao-PVAc) was obtained via radical polymerization with benzoyl peroxide (BPO) as initiator. Last, PVAc/kaolinite was saponified via direct-hydrolysis with NaOH solution in order to obtain PVA/kaolinite nanocomposites, which was characterized by Fourier-Transformation spectroscopy (FTIR), wide X-ray diffraction (WXRD) and transmission electron microscopy (TEM). Their differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) results of the obtained PVA/kaolinite suggested that the thermal properties had an obvious improvement.

Hydroperoxide Traces in Common Cyclic Ethers as Initiators for Controlled RAFT Polymerizations.

PubMed

Eggers, Steffen; Abetz, Volker

2018-04-01

Herein, a reversible addition-fragmentation chain transfer (RAFT) polymerization is introduced for reactive monomers like N-acryloylpyrrolidine or N,N-dimethylacrylamide working without a conventional radical initiator. As a very straightforward proof of principle, the method takes advantage of the usually inconvenient radical-generating hydroperoxide contaminations in cyclic ethers like tetrahydrofuran or 1,4-dioxane, which are very common solvents in polymer sciences. The polymerizations are surprisingly well controlled and the polymers can be extended with a second block, indicating their high livingness. "Solvent-initiated" RAFT polymerizations hence prove to be a feasible access to tailored materials with minimal experimental effort and standard laboratory equipment, only requiring the following ingredients: hydroperoxide-contaminated solvent, monomer, and RAFT agent. In other respects, however, the potential coinitiating ability of the used solvent is to be considered when investigating the kinetics of RAFT polymerizations or aiming for the synthesis of high-livingness polymers, e.g., multiblock copolymers. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Emulsion Polymerization of Butyl Acrylate: Spin Trapping and EPR Study

NASA Technical Reports Server (NTRS)

Kim, S.; Westmoreland, D.

1994-01-01

The propagating radical in the emulsion polymerization reaction of butyl acrylate was detected by Electron Paramagnetic Resonance spectroscopy using two spin trapping agents, 2-methyl-2nitrosopropane and alpha -N-tert-butylnitrone.

Application of an Addition-Fragmentation-Chain Transfer Monomer in Di(meth)acrylate Network Formation to Reduce Polymerization Shrinkage Stress.

PubMed

Shah, Parag K; Stansbury, Jeffrey W; Bowman, Christopher N

2017-08-14

A new addition-fragmentation chain transfer (AFT) capable moiety was incorporated into a dimethacrylate monomer that participated readily in network formation by copolymerizing with multifunctional methacrylates or acrylates. The process of AFT occurred simultaneously with photopolymerization of the AFT monomer (AFM) and other (meth)acrylate monomers leading to polymer stress relaxation via network reconfiguration. At low loading levels of the AFM, a significant reduction in shrinkage stress, especially for acrylate monomers, was observed with nominal effects on conversion. At higher loading levels of the AFM, the photopolymerization reaction kinetics and final double bond conversion were significantly lowered along with a delay in the gel-point conversion. Electron paramagnetic resonance studies during polymerization revealed the presence of a distinct radical species that was present in proportional quantities to the AFM content in the system. The lifetime and the character of the persistent radicals were altered due to the presence of the distinctive radical, in turn affecting the polymerization kinetics. With polymerization conducted at higher irradiance, the differential conversion between the control resin and samples with moderate AFM content was minimal, especially for the methacrylate-based formulations.

Cross-linked β-cyclodextrin and carboxymethyl cellulose hydrogels for controlled drug delivery of acyclovir

PubMed Central

Malik, Nadia Shamshad; Ahmad, Mahmood; Minhas, Muhammad Usman

2017-01-01

To explore the potential role of polymers in the development of drug-delivery systems, this study investigated the use of β-cyclodextrin (β-CD), carboxymethyl cellulose (CMC), acrylic acid (AA) and N’ N’-methylenebis-acrylamide (MBA) in the synthesis of hydrogels for controlled drug delivery of acyclovir (ACV). Different proportions of β-CD, CMC, AA and MBA were blended with each other to fabricate hydrogels via free radical polymerization technique. Fourier transform infrared spectroscopy (FTIR) revealed successful grafting of components into the polymeric network. Thermal and morphological characterization confirmed the formation of thermodynamically stable hydrogels having porous structure. The pH-responsive behaviour of hydrogels has been documented by swelling dynamics and drug release behaviour in simulated gastrointestinal fluids. Drug release kinetics revealed controlled release behaviour of the antiviral drug acyclovir in developed polymeric network. Cross-linked β-cyclodextrin and carboxymethyl cellulose hydrogels can be used as promising candidates for the design and development of controlled drug-delivery systems. PMID:28245257

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.

Preparation and Characterization of InP/Poly(methyl methacrylate) Nanocomposite Films.

PubMed

Kwon, Younghoon; Kim, Jongsung

2017-04-01

Quantum dots (QDs) are nanocrystalline semiconductors with many unusual optical properties. They exhibit very high fluorescence intensities and possess exceptional stability against photo-bleaching. In this study, we report the preparation of InP QDs-poly(methyl methacrylate) (PMMA) hybrids by fabricating QDs via a thermal decomposition reaction, followed by radical polymerization. The InP QDs were synthesized using indium(III) chloride and tris(dimethylamino)phosphine. Flexible composite films were obtained by radical polymerization using methyl methacrylate (MMA) as the monomer and 2,2′-azobis(2-methylpropionitrile) (AIBN) as a radical initiator. The PL intensity of the QDs was lowered upon composite formation with PMMA. However, the composites exhibited higher thermal stability than pure PMMA.

Polymeric phase change nanocomposite (PMMA/Fe:ZnO) for electronic packaging application

NASA Astrophysics Data System (ADS)

Maji, Pranabi; Choudhary, Ram Bilash; Majhi, Malati

2018-01-01

This paper reported the effect of Fe-doped ZnO (Fe:ZnO) nanoparticles on the structural, morphological, thermal, optical and dielectric properties of PMMA matrix. Fe-doped ZnO nanoparticle was synthesized by co-precipitation method, after its surface modification incorporated into the PMMA matrix by free radical polymerization method. The phase analysis and crystal structure were investigated by XRD and FTIR technique. These studies confirmed the chemical structure of the PMMA/Fe:ZnO nanocomposite. FESEM image showed the pyramidal shape and high porosity of PMMA/Fe:ZnO nanocomposite. Thermal analysis of the sample was carried out by thermo-gravimetric analyzer. PMMA/Fe:ZnO nanocomposite was found to have better thermal stability compared to pure one. Broadband dielectric spectroscopic technique was used to investigate the transition of electrical properties of Fe-doped ZnO nanoparticle reinforced PMMA matrix in temperature range 313-373 K. The results elucidated a phase transition from glassy to rubbery state at 344 K.

Living Additive Manufacturing: Transformation of Parent Gels into Diversely Functionalized Daughter Gels Made Possible by Visible Light Photoredox Catalysis

PubMed Central

2017-01-01

Light-initiated additive manufacturing techniques typically rely on layer-by-layer addition or continuous extraction of polymers formed via nonliving, free radical polymerization methods that render the final materials “dead” toward further monomer insertion; the polymer chains within the materials cannot be reactivated to induce chain extension. An alternative “living additive manufacturing” strategy would involve the use of photocontrolled living radical polymerization to spatiotemporally insert monomers into dormant “parent” materials to generate more complex and diversely functionalized “daughter” materials. Here, we demonstrate a proof-of-concept study of living additive manufacturing using end-linked polymer gels embedded with trithiocarbonate iniferters that can be activated by photoinduced single-electron transfer from an organic photoredox catalyst in solution. This system enables the synthesis of a wide range of chemically and mechanically differentiated daughter gels from a single type of parent gel via light-controlled modification of the parent’s average composition, strand length, and/or cross-linking density. Daughter gels that are softer than their parent, stiffer than their parent, larger but with the same modulus as their parent, thermally responsive, polarity responsive, healable, and weldable are all realized. PMID:28280779

Living Additive Manufacturing: Transformation of Parent Gels into Diversely Functionalized Daughter Gels Made Possible by Visible Light Photoredox Catalysis.

PubMed

Chen, Mao; Gu, Yuwei; Singh, Awaneesh; Zhong, Mingjiang; Jordan, Alex M; Biswas, Santidan; Korley, LaShanda T J; Balazs, Anna C; Johnson, Jeremiah A

2017-02-22

Light-initiated additive manufacturing techniques typically rely on layer-by-layer addition or continuous extraction of polymers formed via nonliving, free radical polymerization methods that render the final materials "dead" toward further monomer insertion; the polymer chains within the materials cannot be reactivated to induce chain extension. An alternative "living additive manufacturing" strategy would involve the use of photocontrolled living radical polymerization to spatiotemporally insert monomers into dormant "parent" materials to generate more complex and diversely functionalized "daughter" materials. Here, we demonstrate a proof-of-concept study of living additive manufacturing using end-linked polymer gels embedded with trithiocarbonate iniferters that can be activated by photoinduced single-electron transfer from an organic photoredox catalyst in solution. This system enables the synthesis of a wide range of chemically and mechanically differentiated daughter gels from a single type of parent gel via light-controlled modification of the parent's average composition, strand length, and/or cross-linking density. Daughter gels that are softer than their parent, stiffer than their parent, larger but with the same modulus as their parent, thermally responsive, polarity responsive, healable, and weldable are all realized.

Synthesis of Well-defined Amphiphilic Block Copolymers by Organotellurium-Mediated Living Radical Polymerization (TERP).

PubMed

Kumar, Santosh; Changez, Mohammad; Murthy, C N; Yamago, Shigeru; Lee, Jae-Suk

2011-10-04

Low-molecular weight amphiphilic diblock copolymers, polystyrene-block-poly (2-vinylpyridine) (PS-b-P2VP), and (P2VP-b-PS) with different block ratios were synthesized for the first time via organotellurium-mediated living radical polymerization (TERP). For both the homo- and block copolymerizations, good agreement between the theoretical, and experimental molecular weights was found with nearly 100% yield in every case. The molecular weight distribution for all the samples ranged between 1.10 and 1.24, which is well below the theoretical lower limit of 1.50 for a conventional free radical polymerization. Furthermore, a very simple approach to producing highly dense arrays of titania nanoparticles (TiO2 ) is presented using a site-selective reaction of titanium tetraisopropoxide within the P2VP domains of micellar film of P2VP-b-PS in toluene through the sol-gel method. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Monodisperse, polymeric microspheres produced by irradiation of slowly thawing frozen drops

NASA Technical Reports Server (NTRS)

Rhim, Won-Kyu (Inventor); Hyson, Michael T. (Inventor); Chung, Sang-Kun (Inventor); Colvin, Michael S. (Inventor); Chang, Manchium (Inventor)

1991-01-01

Monodisperse, polymeric microspheres are formed by injecting uniformly shaped droplets of radiation polymerizable monomers, preferably a biocompatible monomer, having covalent binding sites such as hydroxyethylmethacrylate, into a zone, impressing a like charge on the droplet so that they mutually repel each other, spheroidizing the droplets within the zone and collecting the droplets in a pool of cryogenic liquid. As the droplets enter the liquid, they freeze into solid, glassy microspheres, which vaporizes a portion of the cryogenic liquid to form a layer. The like-charged microspheres, suspended within the layer, move to the edge of the vessel holding the pool, are discharged, fall and are collected. The collected microspheres are irradiated while frozen in the cryogenic liquid to form latent free radicals. The frozen microspheres are then slowly thawed to activate the free radicals which polymerize the monomer to form evenly-sized, evenly-shaped, monodisperse polymeric microspheres.

Radical-induced generation of small silver particles in SPEEK/PVA polymer films and solutions: UV-Vis, EPR, and FT-IR studies.

PubMed

Korchev, A S; Konovalova, T; Cammarata, V; Kispert, L; Slaten, L; Mills, G

2006-01-03

The present study is centered on the processes involved in the photochemical generation of nanometer-sized Ag particles via illumination at 350 nm of aqueous solutions and cross linked films containing sulfonated poly(ether ether ketone) and poly(vinyl alcohol). Optical and electron paramagnetic resonance experiments, including electron nuclear double resonance data, proved conclusively that the photogenerated chromophore exhibiting a band with lambda(max) = 565 nm is an alpha-hydroxy aromatic (ketyl) radical of the polymeric ketone. This reducing species was produced by illumination of either solutions or films, but the radical lifetime extended from minutes in the fluid phase to hours in the solid. Direct evidence is presented that this long-lived chromophore reduces Ag(I), Cu(II), and Au(III) ions in solution. A rate constant of k = 1.4 x 10(3) M(-)(1) s(-)(1) was obtained for the reduction of Ag(+) by the ketyl radical from the post-irradiation formation of Ag crystallites. FTIR results confirmed that the photoprocess yielding polymeric ketyl radicals involves a reaction between the macromolecules. The photochemical oxidation of the polymeric alcohol, as well as the formation of light-absorbing macromolecular products and polyols, indicates that the sulfonated polyketone experienced transformations similar to those encountered during illumination of the benzophenone/2-propanol system.

Polymeric Ionic Networks with High Charge Density: Solid-like Electrolytes in Lithium Metal Batteries

DOE PAGES

Zhang, Pengfei; Li, Mingtao; Jiang, Xueguang; ...

2015-11-02

Polymerized ionic networks (PINs) with six ion pairs per repeating unit are synthesized by nucleophilic-substitution-mediated polymerization or radical polymerization of monomers bearing six 1-vinylimidazolium cations. PIN-based solid-like electrolytes show good ionic conductivities (up to 5.32 × 10 -3 S cm -1 at 22 °C), wide electrochemical stability windows (up to 5.6 V), and good interfacial compatibility with the electrodes.

Rapid Three-Dimensional Printing in Water Using Semiconductor-Metal Hybrid Nanoparticles as Photoinitiators.

PubMed

Pawar, Amol Ashok; Halivni, Shira; Waiskopf, Nir; Ben-Shahar, Yuval; Soreni-Harari, Michal; Bergbreiter, Sarah; Banin, Uri; Magdassi, Shlomo

2017-07-12

Additive manufacturing processes enable fabrication of complex and functional three-dimensional (3D) objects ranging from engine parts to artificial organs. Photopolymerization, which is the most versatile technology enabling such processes through 3D printing, utilizes photoinitiators that break into radicals upon light absorption. We report on a new family of photoinitiators for 3D printing based on hybrid semiconductor-metal nanoparticles. Unlike conventional photoinitiators that are consumed upon irradiation, these particles form radicals through a photocatalytic process. Light absorption by the semiconductor nanorod is followed by charge separation and electron transfer to the metal tip, enabling redox reactions to form radicals in aerobic conditions. In particular, we demonstrate their use in 3D printing in water, where they simultaneously form hydroxyl radicals for the polymerization and consume dissolved oxygen that is a known inhibitor. We also demonstrate their potential for two-photon polymerization due to their giant two-photon absorption cross section.

Functionalized and graft copolymers of chitosan and its pharmaceutical applications.

PubMed

Bhavsar, Chintan; Momin, Munira; Gharat, Sankalp; Omri, Abdelwahab

2017-10-01

Chitosan is the second most abundant natural polysaccharide. It belongs a family of polycationic polymers comprised of repetitive units of glucosamine and N-acetylglucosamine. Its biodegradability, nontoxicity, non-immunogenicity and biocompatibility along with properties like mucoadhesion, fungistatic and bacteriogenic have made chitosan an appreciated polymer with numerous applications in the pharmaceutical, comestics and food industry. However, the limited solubility of chitosan at alkaline and neutral pH limits its widespread commercial use. This can be circumvented by fabrication of chitosan by graft copolymerization with acyl, alkyl, monomeric and polymeric moieties. Areas covered: Modifications like quarterization, thiolation, acylation and grafting result in copolymers with higher mucoadhesion strength, increased hydrophobic interactions (advantageous in hydrophobic drug entrapment), and increased solubility in alkaline pH, the ability for adsorption of metal ions, protein and peptide delivery and nutrient delivery. Insights on methods of polymerization, including atomic transfer radical polymerization and click chemistry are discussed. Applications of such modified chitosan copolymers in medical and surgical, and drug delivery, including nasal, oral and buccal delivery have also been covered. Expert opinion: Despite a number of successful investigations, commercialization of chitosan copolymers still remains a challenge. Further advancements in polymerization techniques may address the unmet needs of the healthcare industry.

Squarylium-triazine dyad as a highly sensitive photoradical generator for red light.

PubMed

Kawamura, Koichi; Schmitt, Julien; Barnet, Maxime; Salmi, Hanene; Ley, Christian; Allonas, Xavier

2013-09-16

New dyads, based on squarylium dye and substituted-triazine, were synthesized that exhibit an intramolecular photodissociative electron-transfer reaction. The compounds were used as a red-light photoradical generator. The photochemical activity of the dyad was compared to the corresponding unlinked systems (S+T) by determining the rate constant of electron transfer. The efficiency of the radical generation from the dyad compared to the unlinked system was demonstrated by measuring the maximum rate of free radical polymerization of acrylates in film. An excellent relationship between the rate of electron transfer and the rate of polymerization was found, evidencing the interest of this new approach to efficiently produce radicals under red light. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modeling the chemistry of plasma polymerization using mass spectrometry.

PubMed

Ihrig, D F; Stockhaus, J; Scheide, F; Winkelhake, Oliver; Streuber, Oliver

2003-04-01

The goal of the project is a solvent free painting shop. The environmental technologies laboratory is developing processes of plasma etching and polymerization. Polymerized thin films are first-order corrosion protection and primer for painting. Using pure acetylene we get very nice thin films which were not bonded very well. By using air as bulk gas it is possible to polymerize, in an acetylene plasma, well bonded thin films which are stable first-order corrosion protections and good primers. UV/Vis spectroscopy shows nitrogen oxide radicals in the emission spectra of pure nitrogen and air. But nitrogen oxide is fully suppressed in the presence of acetylene. IR spectroscopy shows only C=O, CH(2) and CH(3) groups but no nitrogen species. With the aid of UV/Vis spectra and the chemistry of ozone formation it is possible to define reactive traps and steps, molecule depletion and processes of proton scavenging and proton loss. Using a numerical model it is possible to evaluate these processes and to calculate theoretical mass spectra. Adjustment of theoretical mass spectra to real measurements leads to specific channels of polymerization which are driven by radicals especially the acetyl radical. The estimated theoretical mass spectra show the specific channels of these chemical processes. It is possible to quantify these channels. This quantification represents the mass flow through this chemical system. With respect to these chemical processes it is possible to have an idea of pollutant production processes.

Nanostructured hybrid hydrogels prepared by a combination of atom transfer radical polymerization and free radical polymerization

PubMed Central

Bencherif, Sidi A.; Siegwart, Daniel J.; Srinivasan, Abiraman; Horkay, Ferenc; Hollinger, Jeffrey O.; Washburn, Newell R.; Matyjaszewski, Krzysztof

2012-01-01

A new method to prepare nanostructured hybrid hydrogels by incorporating well-defined poly(oligo (ethylene oxide) monomethyl ether methacrylate) (POEO300MA) nanogels of sizes 110–120 nm into a larger three-dimensional (3D) matrix was developed for drug delivery scaffolds for tissue engineering applications. Rhodamine B isothiocyanate-labeled dextran (RITC-Dx) or fluorescein isothiocyanate-labeled dextran (FITC-Dx)-loaded POEO300MA nanogels with pendant hydroxyl groups were prepared by activators generated electron transfer atom transfer radical polymerization (AGET ATRP) in cyclohexane inverse miniemulsion. Hydroxyl-containing nanogels were functionalized with methacrylated groups to generate photoreactive nanospheres. 1H NMR spectroscopy confirmed that polymerizable nanogels were successfully incorporated covalently into 3D hyaluronic acid-glycidyl methacrylate (HAGM) hydrogels after free radical photo-polymerization (FRP). The introduction of disulfide moieties into the polymerizable groups resulted in a controlled release of nanogels from cross-linked HAGM hydrogels under a reducing environment. The effect of gel hybridization on the macroscopic properties (swelling and mechanics) was studied. It is shown that swelling and nanogel content are independent of scaffold mechanics. In-vitro assays showed the nanostructured hybrid hydrogels were cytocompatible and the GRGDS (Gly–Arg–Gly–Asp–Ser) contained in the nanogel structure promoted cell–substrate interactions within 4 days of incubation. These nanostructured hydrogels have potential as an artificial extracellular matrix (ECM) impermeable to low molecular weight biomolecules and with controlled pharmaceutical release capability. Moreover, the nanogels can control drug or biomolecule delivery, while hyaluronic acid based-hydrogels can act as a macroscopic scaffold for tissue regeneration and regulator for nanogel release. PMID:19592087

Engineering a horseradish peroxidase C stable to radical attacks by mutating multiple radical coupling sites.

PubMed

Kim, Su Jin; Joo, Jeong Chan; Song, Bong Keun; Yoo, Young Je; Kim, Yong Hwan

2015-04-01

Peroxidases have great potential as industrial biocatalysts. In particular, the oxidative polymerization of phenolic compounds catalyzed by peroxidases has been extensively examined because of the advantage of this method over other conventional chemical methods. However, the industrial application of peroxidases is often limited because of their rapid inactivation by phenoxyl radicals during oxidative polymerization. In this work, we report a novel protein engineering approach to improve the radical stability of horseradish peroxidase isozyme C (HRPC). Phenylalanine residues that are vulnerable to modification by the phenoxyl radicals were identified using mass spectrometry analysis. UV-Vis and CD spectra showed that radical coupling did not change the secondary structure or the active site of HRPC. Four phenylalanine (Phe) residues (F68, F142, F143, and F179) were each mutated to alanine residues to generate single mutants to examine the role of these sites in radical coupling. Despite marginal improvement of radical stability, each single mutant still exhibited rapid radical inactivation. To further reduce inactivation by radical coupling, the four substitution mutations were combined in F68A/F142A/F143A/F179A. This mutant demonstrated dramatic enhancement of radical stability by retaining 41% of its initial activity compared to the wild-type, which was completely inactivated. Structure and sequence alignment revealed that radical-vulnerable Phe residues of HPRC are conserved in homologous peroxidases, which showed the same rapid inactivation tendency as HRPC. Based on our site-directed mutagenesis and biochemical characterization, we have shown that engineering radical-vulnerable residues to eliminate multiple radical coupling can be a good strategy to improve the stability of peroxidases against radical attack. © 2014 Wiley Periodicals, Inc.

Recent Developments of Versatile Photoinitiating Systems for Cationic Ring Opening Polymerization Operating at Any Wavelengths and under Low Light Intensity Sources.

PubMed

Lalevée, Jacques; Mokbel, Haifaa; Fouassier, Jean-Pierre

2015-04-20

Photoinitiators (PI) or photoinitiating systems (PIS) usable in light induced cationic polymerization (CP) and free radical promoted cationic polymerization (FRPCP) reactions (more specifically for cationic ring opening polymerization (ROP)) together with the involved mechanisms are briefly reviewed. The recent developments of novel two- and three-component PISs for CP and FRPCP upon exposure to low intensity blue to red lights is emphasized in details. Examples of such reactions under various experimental conditions are provided.

A Simple and Universal Gel Permeation Chromatography Technique for Precise Molecular Weight Characterization of Well-Defined Poly(ionic liquid)s

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

He, Hongkun; Zhong, Mingjiang; Adzima, Brian

2013-03-20

Poly(ionic liquid)s (PILs) are an important class of technologically relevant materials. However, characterization of well-defined polyionic materials remains a challenge. Herein, we have developed a simple and versatile gel permeation chromatography (GPC) methodology for molecular weight (MW) characterization of PILs with a variety of anions. PILs with narrow MW distributions were synthesized via atom transfer radical polymerization, and the MWs obtained from GPC were further confirmed via nuclear magnetic resonance end group analysis.

Rise and Fall: Poly(phenyl vinyl ketone) Photopolymerization and Photodegradation under Visible and UV Radiation.

PubMed

Reeves, Jennifer A; Allegrezza, Michael L; Konkolewicz, Dominik

2017-07-01

Vinyl ketone polymers, including phenyl vinyl ketone (PVK), are an important class of polymers due to their ability to degrade upon irradiation with ultraviolet light which makes them useful for a variety of applications. However, traditional radical methods for synthesizing PVK polymers give rise to poor control or are unable to produce block copolymers. This work uses reversible addition-fragmentation chain transfer polymerization (RAFT) and photochemistry to polymerize PVK. When visible blue radiation of 440 ± 10 nm is used as the light source for the photopolymerization, rapid polymerization and well-defined polymers are created. This RAFT method uses PVK as both monomer and radical initiator, exciting the PVK mono-mer by 440 ± 10 nm irradiation to avoid the use of an additional radical initiator. Once the poly-mer is synthesized, it is stable against degradation by blue light (440 ± 10 nm), but upon exposure to ultraviolet (UV) radiation (310 ± 20 nm) significant decrease in molecular weight is observed. The degradation is observed for all poly(PVK) materials synthesized. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Poly(meth)acrylates obtained by cascade reaction.

PubMed

Popescu, Dragos; Keul, Helmut; Moeller, Martin

2011-04-04

Preparation, purification, and stabilization of functional (meth)acrylates with a high dipole moment are complex, laborious, and expensive processes. In order to avoid purification and stabilization of the highly reactive functional monomers, a concept of cascade reactions was developed comprising enzymatic monomer synthesis and radical polymerization. Transacylation of methyl acrylate (MA) and methyl methacrylate (MMA) with different functional alcohols, diols, and triols (1,2,6-hexanetriol and glycerol) in the presence of Novozyme 435 led to functional (meth)acrylates. After the removal of the enzyme by means of filtration, removal of excess (meth)acrylate and/or addition of a new monomer, e.g., 2-hydroxyethyl (meth)acrylate the (co)polymerization via free radical (FRP) or nitroxide mediated radical polymerization (NMP) resulted in poly[(meth)acrylate]s with predefined functionalities. Hydrophilic, hydrophobic as well as ionic repeating units were assembled within the copolymer. The transacylation of MA and MMA with diols and triols carried out under mild conditions is an easy and rapid process and is suitable for the preparation of sensitive monomers. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optically active helical vinylterphenyl polymers: chiral teleinduction in radical polymerization and tunable stereomutation.

PubMed

Wang, Rong; Zhang, Jie; Wan, Xinhua

2015-04-01

Helical vinyl aromatic polymers are emerging as interesting chiral materials due to their dynamic tailorability, synthetic simplicity, and outstanding chemical and physical stabilities. This Personal Account discusses long-range chirality transfer in the radical polymerization of vinylterphenyl monomers and tunable stereomutation of the resultant polymers. It begins with a general introduction to the design, synthesis, and characterization of helical poly{(+)-2,5-bis[4'-((S)-2-methylbutyloxy)phenyl]styrene}, the first one of this series of polymers. Then, long-range chirality transfer during radical polymerization of terphenyl-based vinyl monomers is explained. After that, the chiroptical property control of the resultant polymers by means of the transition from kinetically controlled conformation to thermodynamically controlled conformation and external stimulus is described. This Personal Account concludes by discussing the advantages and disadvantages of the strategy of using vinylterphenyls to obtain optically active helical polymers and providing a short outlook, especially emphasizing the importance of tacticity on the chiroptical properties of polymers. Copyright © 2015 The Chemical Society of Japan and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Fundamentals of plasma chemistry and its application to drug engineering].

PubMed

Kuzuya, M

1996-04-01

In this review, our novel research works in both low temperature plasma chemistry and solid state plasma chemistry were described. As for low temperature plasma, the ESR study on plasma-induced radicals of several selected conventional polymers was shown including the detailed analyses of the radical structure and the mechanism by which the radicals were formed on typical degradable methacrylic polymers and cross-linkable polystyrene. One of the pharmaceutical applications of the plasma processing for drug delivery system (DDS) was also described, which includes the preparations of double-compressed tablet consisting of drugs as a core material and various types of polymers as a wall material followed by plasma-irradiation on such a tablet. As for solid state plasma, the detailed reaction mechanism of solid state mechanochemical polymerization was shown including the solid state single electron transfer and the special feature of the resulting polymers. The structural criteria for polymerizable monomer derived from the quantum chemical considerations were also established. Based on the above findings, we synthesized various polymeric prodrugs by mechanochemical polymerization and studied the nature of hydrolyses (drug release).

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.

Synthesis of Novel μ-Star Copolymers with Poly(N-Octyl Benzamide) and Poly(ε-Caprolactone) Miktoarms through Chain-Growth Condensation Polymerization, Styrenics-Assisted Atom Transfer Radical Coupling, and Ring-Opening Polymerization.

PubMed

Huang, Chih-Feng; Aimi, Junko; Lai, Kuan-Yu

2017-02-01

Star copolymers are known to phase separate on the nanoscale, providing useful self-assembled morphologies. In this study, the authors investigate synthesis and assembly behavior of miktoarm star (μ-star) copolymers. The authors employ a new strategy for the synthesis of unprecedented μ-star copolymers presenting poly(N-octyl benzamide) (PBA) and poly(ε-caprolactone) (PCL) arms: a combination of chain-growth condensation polymerization, styrenics-assisted atom transfer radical coupling, and ring-opening polymerization. Gel permeation chromatography, mass-analyzed laser desorption/ionization mass spectrometry, and 1 H NMR spectroscopy reveal the successful synthesis of a well-defined (PBA 11 ) 2 -(PCL 15 ) 4 μ-star copolymer (M n ,NMR ≈ 12 620; Đ = 1.22). Preliminary examination of the PBA 2 PCL 4 μ-star copolymer reveals assembled nanofibers having a uniform diameter of ≈20 nm. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Excimers from stable and persistent supramolecular radical-pairs in red/NIR-emitting organic nanoparticles and polymeric films.

PubMed

Blasi, Davide; Nikolaidou, Domna M; Terenziani, Francesca; Ratera, Imma; Veciana, Jaume

2017-03-29

In this work, the luminescence properties of new materials based on open-shell molecular systems are studied. In particular, we prepared polymeric films and organic nanoparticles (ONPs) doped with triphenylmethyl radical molecules. ONPs exhibit a uniform size distribution, spherical morphology and high colloidal stability. The emission spectrum of low-doped ONP suspensions and low-doped films is very similar to the emission spectrum of TTM in solution, while the luminescence lifetime and the luminescence quantum yield (LQY) are highly increased. Increasing the radical doping leads to a progressive decrease of the LQY and the appearance of a new broad excimeric band at longer wavelengths, both for ONPs and films. Thus, not only the luminescence properties were improved, but also the formation of excimers from stable and persistent supramolecular radical-pairs was observed for the first time. The good stability and luminescence properties with emission in the red-NIR region (650-800 nm), together with the open-shell nature of the emitter, make these free-radical excimer-forming materials promising candidates for optoelectronic and bioimaging applications.

Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization (ATRP) from Poly(vinyl chloride)- co -chlorinated Poly(vinyl chloride) (PVC- co -CPVC) Fiber

DOE PAGES

Brown, Suree; Yue, Yanfeng; Kuo, Li-Jung; ...

2016-03-11

The need to secure future supplies of energy attracts researchers in several countries to a vast resource of nuclear energy fuel: uranium in seawater (estimated at 4.5 billion tons in seawater). In this study, we developed effective adsorbent fibers for the recovery of uranium from seawater via atom-transfer radical polymerization (ATRP) from a poly-(vinyl chloride)-co-chlorinated poly(vinyl chloride) (PVC-co-CPVC) fiber. ATRP was employed in the surface graft polymerization of acrylonitrile (AN) and tert-butyl acrylate (tBA), precursors for uranium-interacting functional groups, from PVC-co-CPVC fiber. The [tBA]/[AN] was systematically varied to identify the optimal ratio between hydrophilic groups (from tBA) and uranyl-binding ligandsmore » (from AN). The best performing adsorbent fiber, the one with the optimal [tBA]/[AN] ratio and a high degree of grafting (1390%), demonstrated uranium adsorption capacities that are significantly greater than those of the Japan Atomic Energy Agency (JAEA) reference fiber in natural seawater tests (2.42 3.24 g/kg in 42 days of seawater exposure and 5.22 g/kg in 49 days of seawater exposure, versus 1.66 g/kg in 42 days of seawater exposure and 1.71 g/kg in 49 days of seawater exposure for JAEA). Lastly, adsorption of other metal ions from seawater and their corresponding kinetics were also studied. The grafting of alternative monomers for the recovery of uranium from seawater is now under development by this versatile technique of ATRP.« less

Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization (ATRP) from Poly(vinyl chloride)- co -chlorinated Poly(vinyl chloride) (PVC- co -CPVC) Fiber

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

Brown, Suree; Yue, Yanfeng; Kuo, Li-Jung

The need to secure future supplies of energy attracts researchers in several countries to a vast resource of nuclear energy fuel: uranium in seawater (estimated at 4.5 billion tons in seawater). In this study, we developed effective adsorbent fibers for the recovery of uranium from seawater via atom-transfer radical polymerization (ATRP) from a poly-(vinyl chloride)-co-chlorinated poly(vinyl chloride) (PVC-co-CPVC) fiber. ATRP was employed in the surface graft polymerization of acrylonitrile (AN) and tert-butyl acrylate (tBA), precursors for uranium-interacting functional groups, from PVC-co-CPVC fiber. The [tBA]/[AN] was systematically varied to identify the optimal ratio between hydrophilic groups (from tBA) and uranyl-binding ligandsmore » (from AN). The best performing adsorbent fiber, the one with the optimal [tBA]/[AN] ratio and a high degree of grafting (1390%), demonstrated uranium adsorption capacities that are significantly greater than those of the Japan Atomic Energy Agency (JAEA) reference fiber in natural seawater tests (2.42 3.24 g/kg in 42 days of seawater exposure and 5.22 g/kg in 49 days of seawater exposure, versus 1.66 g/kg in 42 days of seawater exposure and 1.71 g/kg in 49 days of seawater exposure for JAEA). Lastly, adsorption of other metal ions from seawater and their corresponding kinetics were also studied. The grafting of alternative monomers for the recovery of uranium from seawater is now under development by this versatile technique of ATRP.« less

Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization (ATRP) from Poly(vinyl chloride)- co -chlorinated Poly(vinyl chloride) (PVC- co -CPVC) Fiber

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

Brown, Suree; Yue, Yanfeng; Kuo, Li-Jung

The need to secure future supplies of energy attracts researchers in several countries to a vast resource of nuclear energy fuel: uranium in seawater (estimated at 4.5 billion tons in seawater). In this study, we developed effective adsorbent fibers for the recovery of uranium from seawater via atom-transfer radical polymerization (ATRP) from a poly- (vinyl chloride)-co-chlorinated poly(vinyl chloride) (PVC-co-CPVC) fiber. ATRP was employed in the surface graft polymerization of acrylonitrile (AN) and tert-butyl acrylate (tBA), precursors for uranium-interacting functional groups, from PVC-co-CPVC fiber. The [tBA]/[AN] was systematically varied to identify the optimal ratio between hydrophilic groups (from tBA) and uranyl-bindingmore » ligands (from AN). The best performing adsorbent fiber, the one with the optimal [tBA]/[AN] ratio and a high degree of grafting (1390%), demonstrated uranium adsorption capacities that are significantly greater than those of the Japan Atomic Energy Agency (JAEA) reference fiber in natural seawater tests (2.42-3.24 g/kg in 42 days of seawater exposure and 5.22 g/kg in 49 days of seawater exposure, versus 1.66 g/kg in 42 days of seawater exposure and 1.71 g/kg in 49 days of seawater exposure for JAEA). Adsorption of other metal ions from seawater and their corresponding kinetics were also studied. The grafting of alternative monomers for the recovery of uranium from seawater is now under development by this versatile technique of ATRP.« less

FROM ATOM TRANSFER RADICAL ADDITION TO ATOM TRANSFER RADICAL POLYMERIZATION. (R829580)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Developing new methods for the mono-end functionalization of living ring opening metathesis polymers.

PubMed

Kilbinger, Andreas F M

2012-01-01

In this article we present a review of our recent results in one area of research we are involved in. All research efforts in our group focus on functional polymers and new ways of gaining higher levels of control with regard to the placement of functional groups within these polymers. Here, the living ring opening metathesis polymerization (ROMP) will be reviewed for which end-functionalization methods had been rare until very recently. Polymers carrying particular functional groups only at the chain-ends are, however, very interesting for a variety of industrial and academic applications. Polymeric surfactants and polymer-protein conjugates are two examples for the former and polymer-β-sheet-peptide conjugates one example for the latter. The functionalization of macroscopic or nanoscopic surfaces often relies on mono-end functional polymers. Complex macromolecular architectures are often constructed from macromolecules carrying exactly one functional group at their chain- end. The ring opening metathesis polymerization is particularly interesting in this context as it is one of the most functional group tolerant polymerization methods known. Additionally, high molecular weight polymers are readily accessible with this technique, a feature that living radical polymerizations often struggle to achieve. Finding new ways of functionalizing the polymer chain-end of ROMP polymers has therefore been a task long overdue. Here, we present our contribution to this area of research.

Living additive manufacturing: Transformation of parent gels into diversely functionalized daughter gels made possible by visible light photoredox catalysis

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

Chen, Mao; Gu, Yuwei; Singh, Awaneesh

Light-initiated additive manufacturing techniques typically rely on layer-by-layer addition or continuous extraction of polymers formed via nonliving, free radical polymerization methods that render the final materials “dead” toward further monomer insertion; the polymer chains within the materials cannot be reactivated to induce chain extension. An alternative “living additive manufacturing” strategy would involve the use of photocontrolled living radical polymerization to spatiotemporally insert monomers into dormant “parent” materials to generate more complex and diversely functionalized “daughter” materials. Here, we demonstrate a proof-of-concept study of living additive manufacturing using end-linked polymer gels embedded with trithiocarbonate iniferters that can be activated by photoinducedmore » single-electron transfer from an organic photoredox catalyst in solution. This system enables the synthesis of a wide range of chemically and mechanically differentiated daughter gels from a single type of parent gel via light-controlled modification of the parent’s average composition, strand length, and/or cross-linking density. Furthermore, daughter gels that are softer than their parent, stiffer than their parent, larger but with the same modulus as their parent, thermally responsive, polarity responsive, healable, and weldable are all realized.« less

Living additive manufacturing: Transformation of parent gels into diversely functionalized daughter gels made possible by visible light photoredox catalysis

DOE PAGES

Chen, Mao; Gu, Yuwei; Singh, Awaneesh; ...

2017-01-13

Light-initiated additive manufacturing techniques typically rely on layer-by-layer addition or continuous extraction of polymers formed via nonliving, free radical polymerization methods that render the final materials “dead” toward further monomer insertion; the polymer chains within the materials cannot be reactivated to induce chain extension. An alternative “living additive manufacturing” strategy would involve the use of photocontrolled living radical polymerization to spatiotemporally insert monomers into dormant “parent” materials to generate more complex and diversely functionalized “daughter” materials. Here, we demonstrate a proof-of-concept study of living additive manufacturing using end-linked polymer gels embedded with trithiocarbonate iniferters that can be activated by photoinducedmore » single-electron transfer from an organic photoredox catalyst in solution. This system enables the synthesis of a wide range of chemically and mechanically differentiated daughter gels from a single type of parent gel via light-controlled modification of the parent’s average composition, strand length, and/or cross-linking density. Furthermore, daughter gels that are softer than their parent, stiffer than their parent, larger but with the same modulus as their parent, thermally responsive, polarity responsive, healable, and weldable are all realized.« less

Laser flash photolysis and CIDNP studies of steric effects on coupling rate constants of imidazolidine nitroxide with carbon-centered radicals, methyl isobutyrate-2-yl and tert-butyl propionate-2-yl.

PubMed

Zubenko, Dmitry; Tsentalovich, Yuri; Lebedeva, Nataly; Kirilyuk, Igor; Roshchupkina, Galina; Zhurko, Irina; Reznikov, Vladimir; Marque, Sylvain R A; Bagryanskaya, Elena

2006-08-04

Time-resolved chemically induced dynamic nuclear polarization (TR-CIDNP) and laser flash photolysis (LFP) techniques have been used to measure rate constants for coupling between acrylate-type radicals and a series of newly synthesized stable imidazolidine N-oxyl radicals. The carbon-centered radicals under investigation were generated by photolysis of their corresponding ketone precursors RC(O)R (R = C(CH3)2-C(O)OCH3 and CH(CH3)-C(O)-OtBu) in the presence of stable nitroxides. The coupling rate constants kc for modeling studies of nitroxide-mediated polymerization (NMP) experiments were determined, and the influence of steric and electronic factors on kc values was addressed by using a Hammett linear free energy relationship. The systematic changes in kc due to the varied steric (Es,n) and electronic (sigmaL,n) characters of the substituents are well-described by the biparameter equation log(kc/M- 1s(-1)) = 3.52sigmaL,n + 0.47Es,n + 10.62. Hence, kc decreases with the increasing steric demand and increases with the increasing electron-withdrawing character of the substituents on the nitroxide.

Free-Radical Polymerization Using the Rotating-Sector Method.

ERIC Educational Resources Information Center

Moss, Stephen J.

1982-01-01

Discusses principles of a particular approach in teaching elementary kinetics of polymerization. Although the treatment discussed is more difficult for students to grasp, problems may be reduced using a computer program. The program, written in Applesoft Basic, is available from the author together with sample output. (JN)

Selective extraction of clonazepam from human plasma and urine samples by molecularly imprinted polymeric beads.

PubMed

Panahi, Homayon Ahmad; Mehramizi, Ali; Ghassemi, Somayeh; Moniri, Elham

2014-03-01

A molecularly imprinted polymer (MIP) based on free-radical polymerization was prepared with 1-(N,N-biscarboxymethyl)amino-3-allylglycerol and N,N-dimethylacrylamide as functional monomers, N,N-methylene diacrylamide as the cross-linker, copper ion-clonazepam as the template and 2,2-azobis(2-methylbutyronitrile) as the initiator. The imprinted polymer was characterized by Fourier transform infrared spectroscopy, elemental analysis, thermo-gravimetric analysis, and SEM. The MIP of agglomerated microparticles with multipores was used for SPE. The imprinted polymer sorbent was selective for clonazepam. The optimum pH and sorption capacity were 5 and 0.18 mg/g at 20C, respectively. The profile of the drug uptake by the sorbent reflects good accessibility of the active sites in the imprinted polymer sorbent. The MIP-SPE was the most feasible technique for the extraction of clonazepam with a high recovery from human plasma and urine samples.

Cobalt-Mediated Radical Polymerization of Vinyl Acetate and Acrylonitrile in Supercritical Carbon Dioxide.

PubMed

Kermagoret, Anthony; Chau, Ngoc Do Quyen; Grignard, Bruno; Cordella, Daniela; Debuigne, Antoine; Jérôme, Christine; Detrembleur, Christophe

2016-03-01

Cobalt-mediated radical polymerization (CMRP) of vinyl acetate (VAc) is successfully achieved in supercritical carbon dioxide (scCO2). CMRP of VAc is conducted using an alkyl-cobalt(III) adduct that is soluble in scCO2. Kinetics studies coupled to visual observations of the polymerization medium highlight that the melt viscosity and PVAc molar mass (Mn) are key parameters that affect the CMRP in scCO2. It is noticed that CMRP is controlled for Mn up to 10 000 g mol(-1), but loss of control is progressively observed for higher molar masses when PVAc precipitates in the polymerization medium. Low molar mass PVAc macroinitiator, prepared by CMRP in scCO2, is then successfully used to initiate the acrylonitrile polymerization. PVAc-b-PAN block copolymer is collected as a free flowing powder at the end of the process although the dispersity of the copolymer increases with the reaction time. Although optimization is required to decrease the dispersity of the polymer formed, this CMRP process opens new perspectives for macromolecular engineering in scCO2 without the utilization of fluorinated comonomers or organic solvents. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Visible-Light Organic Photocatalysis for Latent Radical-Initiated Polymerization via 2e–/1H+ Transfers: Initiation with Parallels to Photosynthesis

PubMed Central

2015-01-01

We report the latent production of free radicals from energy stored in a redox potential through a 2e–/1H+ transfer process, analogous to energy harvesting in photosynthesis, using visible-light organic photoredox catalysis (photocatalysis) of methylene blue chromophore with a sacrificial sterically hindered amine reductant and an onium salt oxidant. This enables light-initiated free-radical polymerization to continue over extended time intervals (hours) in the dark after brief (seconds) low-intensity illumination and beyond the spatial reach of light by diffusion of the metastable leuco-methylene blue photoproduct. The present organic photoredox catalysis system functions via a 2e–/1H+ shuttle mechanism, as opposed to the 1e– transfer process typical of organometallic-based and conventional organic multicomponent photoinitiator formulations. This prevents immediate formation of open-shell (radical) intermediates from the amine upon light absorption and enables the “storage” of light-energy without spontaneous initiation of the polymerization. Latent energy release and radical production are then controlled by the subsequent light-independent reaction (analogous to the Calvin cycle) between leuco-methylene blue and the onium salt oxidant that is responsible for regeneration of the organic methylene blue photocatalyst. This robust approach for photocatalysis-based energy harvesting and extended release in the dark enables temporally controlled redox initiation of polymer syntheses under low-intensity short exposure conditions and permits visible-light-mediated synthesis of polymers at least 1 order of magnitude thicker than achievable with conventional photoinitiated formulations and irradiation regimes. PMID:24786755

Visible-light organic photocatalysis for latent radical-initiated polymerization via 2e⁻/1H⁺ transfers: initiation with parallels to photosynthesis.

PubMed

Aguirre-Soto, Alan; Lim, Chern-Hooi; Hwang, Albert T; Musgrave, Charles B; Stansbury, Jeffrey W

2014-05-21

We report the latent production of free radicals from energy stored in a redox potential through a 2e(-)/1H(+) transfer process, analogous to energy harvesting in photosynthesis, using visible-light organic photoredox catalysis (photocatalysis) of methylene blue chromophore with a sacrificial sterically hindered amine reductant and an onium salt oxidant. This enables light-initiated free-radical polymerization to continue over extended time intervals (hours) in the dark after brief (seconds) low-intensity illumination and beyond the spatial reach of light by diffusion of the metastable leuco-methylene blue photoproduct. The present organic photoredox catalysis system functions via a 2e(-)/1H(+) shuttle mechanism, as opposed to the 1e(-) transfer process typical of organometallic-based and conventional organic multicomponent photoinitiator formulations. This prevents immediate formation of open-shell (radical) intermediates from the amine upon light absorption and enables the "storage" of light-energy without spontaneous initiation of the polymerization. Latent energy release and radical production are then controlled by the subsequent light-independent reaction (analogous to the Calvin cycle) between leuco-methylene blue and the onium salt oxidant that is responsible for regeneration of the organic methylene blue photocatalyst. This robust approach for photocatalysis-based energy harvesting and extended release in the dark enables temporally controlled redox initiation of polymer syntheses under low-intensity short exposure conditions and permits visible-light-mediated synthesis of polymers at least 1 order of magnitude thicker than achievable with conventional photoinitiated formulations and irradiation regimes.

One-Pot Synthesis of Multifunctional Polymers by Light-Controlled Radical Polymerization and Enzymatic Catalysis with Candida antarctica Lipase B.

PubMed

Hrsic, Emin; Keul, Helmut; Möller, Martin

2015-12-01

The preparation of multifunctional polymers and block copolymers by a straightforward one-pot reaction process that combines enzymatic transacylation with light-controlled polymerization is described. Functional methacrylate monomers are synthesized by enzymatic transacylation and used in situ for light-controlled polymerization, leading to multifunctional methacrylate-based polymers with well-defined microstructure. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Khezri, Khezrollah, E-mail: kh.khezri@ut.ac.ir; Roghani-Mamaqani, Hossein

Graphical abstract: Effect of mesoporous silica nanoparticles (MCM-41) on the activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP) is investigated. Decrement of conversion and number average molecular weight and also increment of polydispersity index (PDI) values are three main results of addition of MCM-41 nanoparticles. Incorporation of MCM-41 nanoparticles in the polystyrene matrix can clearly increase thermal stability and decrease glass transition temperature of the nanocomposites. - Highlights: • Spherical morphology, hexagonal structure, and high surface area with regular pore diameters of the synthesized MCM-41 nanoparticles are examined. • AGET ATRP of styrene in the presencemore » of MCM-41 nanoparticles is performed. • Effect of MCM-41 nanoparticles addition on the polymerization rate, conversion and molecular weights of the products are discussed. • Improvement in thermal stability of the nanocomposites and decreasing T{sub g} values was also observed by incorporation of MCM-41 nanoparticles. - Abstract: Activator generated by electron transfer for atom transfer radical polymerization was employed to synthesize well-defined mesoporous silica nanoparticles/polystyrene composites. Inherent features of spherical mesoporous silica nanoparticles were evaluated by nitrogen adsorption/desorption isotherm, X-ray diffraction and scanning electron microscopy analysis techniques. Conversion and molecular weight evaluations were carried out using gas and size exclusion chromatography respectively. By the addition of only 3 wt% mesoporous silica nanoparticles, conversion decreases from 81 to 58%. Similarly, number average molecular weight decreases from 17,116 to 12,798 g mol{sup −1}. However, polydispersity index (PDI) values increases from 1.24 to 1.58. A peak around 4.1–4.2 ppm at proton nuclear magnetic resonance spectroscopy results clearly confirms the living nature of the polymerization. Thermogravimetric analysis shows that thermal stability of the nanocomposites increases by adding nanoparticles content. Decrease of glass transition temperature is also demonstrated by the addition of 3 wt% of silica nanoparticles according to the differential scanning calorimetry results.« less

Precision synthesis of functional materials via RAFT polymerization and click-type chemical reactions

NASA Astrophysics Data System (ADS)

Flores, Joel Diez

2011-12-01

The need to tailor polymeric architectures with specific physico-chemical properties via the simplest, cleanest, and most efficient synthetic route possible has become the ultimate goal in polymer synthesis. Recent progress in macromolecular science, such as the discoveries of controlled/"living" free radical polymerization (CRP) methods, has brought about synthetic capabilities to prepare (co)polymers with advanced topologies, predetermined molecular weights, narrow molecular weight distributions, and precisely located functional groups. In addition, the establishment of click chemistry has redefined the selected few highly efficient chemical reactions that become highly useful in post-polymerization modification strategies. Hence, the ability to make well-defined topologies afforded by controlled polymerization techniques and the facile incorporation of functionalities along the chain via click-type reactions have yielded complex architectures, allowing the investigation of physical phenomena which otherwise could not be studied with systems prepared via conventional methods. The overarching theme of the research work described in this dissertation is the fusion of the excellent attributes of reversible addition-fragmentation chain transfer (RAFT) polymerization method, which is one of the CRP techniques, and click-type chemical reactions in the precision of synthesis of advanced functional materials. Chapter IV is divided into three sections. In Section I, the direct RAFT homopolymerization of 2-(acryloyloxy)ethyl isocyanate (AOI) and subsequent post-polymerization modifications are described. The polymerization conditions were optimized in terms of the choice of RAFT chain transfer agent (CTA), polymerization temperature and the reaction medium. Direct RAFT polymerization of AOI requires a neutral CTA, and relatively low reaction temperature to yield AOI homopolymers with low polydispersities. Efficient side-chain functionalization of PAOI homopolymers was achieved via reaction with model amine, thiol and alcohol compounds yielding urea, thiourethane and urethane derivatives, respectively. Reactions with amines and thiols (in the presence of base) were rapid, quantitative and efficient. However, the reaction with alcohols catalyzed by dibutyltin dilaurate (DBTDL) was relatively slow but proceeded to completion. Selective reaction pathways for the addition of difunctional ethanolamine and mercaptoethanol were also investigated. A related strategy is described in Section II wherein a hydroxyl-containing diblock copolymer precursor was transformed into a library of functional copolymers via two sequential post-polymerization modification reactions. A diblock copolymer scaffold, poly[(N,N-dimethylacrylamide)-b-( N-(2-hydroxyethyl)acrylamide] (PDMA-b-PHEA) was first prepared. The hydroxyl groups of the HEA block were then reacted with 2-(acryloyloxy)ethylisocyanate (AOI) and allylisocyanate (AI) resulting in acrylate- and allyl-functionalized copolymer precursors, respectively. The efficiencies of Michael-type and free radical thiol addition reactions were investigated using selected thiols having alkyl, aryl, hydroxyl, carboxylic acid, amine and amino acid functionalities. The steps of RAFT polymerization, isocyanate-hydroxyl coupling and thiol-ene addition are accomplished under mild conditions, thus offering facile and modular routes to synthesize functional copolymers. The synthesis and solution studies of pH- and salt-responsive triblock copolymer are described in Section III. This system is capable of forming self-locked micellar structures which may be controlled by changing solution pH as well as ionic strength. A triblock copolymer containing a permanently hydrophilic poly(N,N-dimethylacrylamide) (PDMA) outer block, a salt-sensitive zwitterionic poly(3[2-(N-methylacrylamido)ethyl dimethylammonio]propanesulfonate) (PMAEDAPS) middle block and a pH-responsive 3-acrylamido-3-methylbutanoic acid (PAMBA) core block was synthesized using aqueous RAFT polymerization. A facile formation of "self-locking" shell cross-linked micelles is achieved by changing solution pH and salt concentration. The reversible "self-locking" is attained from the interactions of zwitterionic groups in the middle block that constitutes the shell of the micelles. The structure slowly dissociates into unimers in 2-3 days at pH above the pKa of the PAMBA block.

Sulfonated poly(ether ether ketone)/poly(vinyl alcohol) sensitizing system for solution photogeneration of small Ag, Au, and Cu crystallites.

PubMed

Korchev, A S; Shulyak, T S; Slaten, B L; Gale, W F; Mills, G

2005-04-28

Illumination of air-free aqueous solutions containing sulfonated poly(ether ether ketone) and poly(vinyl alcohol) with 350 nm light results in benzophenone ketyl radicals of the polyketone. The polymer radicals form with a quantum yield 0.02 and decay with a second-order rate constant 6 orders of magnitude lower than that of typical alpha-hydroxy radicals. Evidence is presented that the polymeric benzophenone ketyl radicals reduce Ag+, Cu2+, and AuCl4- to metal particles of nanometer dimensions. Decreases in the reduction rates with increasing Ag(I), Cu(II), and Au(III) concentrations are explained using a kinetic model in which the metal ions quench the excited state of the polymeric benzophenone groups, which forms the macromolecular radicals. Quenching is fastest for Ag+, whereas Cu2+ and AuCl4- exhibit similar rate constants. Particle formation becomes more complex as the number of equivalents needed to reduce the metal ions increases; the Au(III) system is an extreme case where the radical reactions operate in parallel with secondary light-initiated and thermal reduction channels. For each metal ion, the polymer-initiated photoreactions produce crystallites possessing distinct properties, such as a very strong plasmon in the Ag case or the narrow size distribution exhibited by Au particles.

Photogeneration of H2O2 in SPEEK/PVA aqueous polymer solutions.

PubMed

Little, Brian K; Lockhart, PaviElle; Slaten, B L; Mills, G

2013-05-23

Photolysis of air-saturated aqueous solutions containing sulphonated poly(ether etherketone) and poly(vinyl alcohol) results in the generation of hydrogen peroxide. Consumption of oxygen and H2O2 formation are initially concurrent processes with a quantum yield of peroxide generation of 0.02 in stirred or unstirred solutions within the range of 7 ≤ pH ≤ 9. The results are rationalized in terms of O2 reduction by photogenerated α-hydroxy radicals of the polymeric ketone in competition with radical-radical processes that consume the macromolecular reducing agents. Generation of H2O2 is controlled by the photochemical transformation that produces the polymer radicals, which is most efficient in neutral and slightly alkaline solutions. Quenching of the excited state of the polyketone by both H3O(+) and OH(-) affect the yields of the reducing macromolecular radicals and of H2O2. Deprotonation of the α-hydroxy polymeric radicals at pH > 9 accelerate their decay and contribute to suppressing the peroxide yields in basic solutions. Maxima in [H2O2] are observed when illuminations are performed with static systems, where O2 reduction is faster than diffusion of oxygen into the solutions. Under such conditions H2O2 can compete with O2 for the reducing radicals resulting in a consumption of the peroxide.

Advanced Materials by Atom Transfer Radical Polymerization.

PubMed

Matyjaszewski, Krzysztof

2018-06-01

Atom transfer radical polymerization (ATRP) has been successfully employed for the preparation of various advanced materials with controlled architecture. New catalysts with strongly enhanced activity permit more environmentally benign ATRP procedures using ppm levels of catalyst. Precise control over polymer composition, topology, and incorporation of site specific functionality enables synthesis of well-defined gradient, block, comb copolymers, polymers with (hyper)branched structures including stars, densely grafted molecular brushes or networks, as well as inorganic-organic hybrid materials and bioconjugates. Examples of specific applications of functional materials include thermoplastic elastomers, nanostructured carbons, surfactants, dispersants, functionalized surfaces, and biorelated materials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organocatalyzed atom transfer radical polymerization driven by visible light.

PubMed

Theriot, Jordan C; Lim, Chern-Hooi; Yang, Haishen; Ryan, Matthew D; Musgrave, Charles B; Miyake, Garret M

2016-05-27

Atom transfer radical polymerization (ATRP) has become one of the most implemented methods for polymer synthesis, owing to impressive control over polymer composition and associated properties. However, contamination of the polymer by the metal catalyst remains a major limitation. Organic ATRP photoredox catalysts have been sought to address this difficult challenge but have not achieved the precision performance of metal catalysts. Here, we introduce diaryl dihydrophenazines, identified through computationally directed discovery, as a class of strongly reducing photoredox catalysts. These catalysts achieve high initiator efficiencies through activation by visible light to synthesize polymers with tunable molecular weights and low dispersities. Copyright © 2016, American Association for the Advancement of Science.

Investigation of metal ligand affinities of atom transfer radical polymerization catalysts with a quadrupole ion trap.

PubMed

di Lena, Fabio; Matyjaszewski, Krzysztof

2009-11-07

An electrospray ionization mass spectrometer equipped with a quadrupole ion trap as the mass analyzer provided a powerful tool for the investigation of metal ligand affinities of catalysts for atom transfer radical polymerization. It allowed, in particular, (i) the identification, in a library of ligands, of the most stable, and thus active, copper catalysts; (ii) the assessment of the effects of the reaction medium on the relative stabilities of the catalyst complexes; and (iii) the evaluation of the influence of the nature of the ligand on both the complex halogenophilicity and the metal-ligand stabilities in the gas-phase.

Photo-triggered solvent-free metamorphosis of polymeric materials.

PubMed

Honda, Satoshi; Toyota, Taro

2017-09-11

Liquefaction and solidification of materials are the most fundamental changes observed during thermal phase transitions, yet the design of organic and polymeric soft materials showing isothermal reversible liquid-nonliquid conversion remains challenging. Here, we demonstrate that solvent-free repeatable molecular architectural transformation between liquid-star and nonliquid-network polymers that relies on cleavage and reformation of a covalent bond in hexaarylbiimidazole. Liquid four-armed star-shaped poly(n-butyl acrylate) and poly(dimethyl siloxane) with 2,4,5-triphenylimidazole end groups were first synthesized. Subsequent oxidation of the 2,4,5-triphenylimidazoles into 2,4,5-triphenylimidazoryl radicals and their coupling with these liquid star polymers to form hexaarylbiimidazoles afforded the corresponding nonliquid network polymers. The resulting nonliquid network polymers liquefied upon UV irradiation and produced liquid star-shaped polymers with 2,4,5-triphenylimidazoryl radical end groups that reverted to nonliquid network polymers again by recoupling of the generated 2,4,5-triphenylimidazoryl radicals immediately after terminating UV irradiation.The design of organic and polymeric soft materials showing isothermal reversible liquid-nonliquid conversion is challenging. Here, the authors show solvent-free repeatable molecular architectural transformation between liquid-star and non-liquid-network polymers by the cleavage and reformation of covalent bonds in the polymer chain.

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.

Software for Demonstration of Features of Chain Polymerization Processes

ERIC Educational Resources Information Center

Sosnowski, Stanislaw

2013-01-01

Free software for the demonstration of the features of homo- and copolymerization processes (free radical, controlled radical, and living) is described. The software is based on the Monte Carlo algorithms and offers insight into the kinetics, molecular weight distribution, and microstructure of the macromolecules formed in those processes. It also…

Effect of wall material on the antioxidant activity and physicochemical properties of Rubus fruticosus juice microcapsules.

PubMed

Díaz, Dafne I; Beristain, Cesar I; Azuara, Ebner; Luna, Guadalupe; Jimenez, Maribel

2015-01-01

Blackberry (Rubus fruticosus) juice possesses compounds with antioxidant activity, which can be protected by different biopolymers used in the microencapsulation. Therefore, the effects of cell wall material including maltodextrin (MD), Arabic gum (GA) and whey protein concentrate (WPC) were evaluated on the physicochemical and antioxidant properties of encapsulated blackberries using a spray-drying technique. Anthocyanin concentration, polymeric colour, total polyphenols, radical scavenging activity of the 1,1-diphenyl-2-picrilhydrazil radical, reducing power and the stability at different storage conditions were evaluated. GA and MD conferred a similar protection to the antioxidant compounds when the microcapsules were stored at low water activities (aw < 0.515) in contrast to at a high moisture content (aw > 0.902), whereas WPC presented a high protection. Therefore, the selection of the best wall material for blackberry juice encapsulation depends of the conditions of storage of the powder.

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.

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

Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization in Undergraduate Polymer Science Lab

ERIC Educational Resources Information Center

Nguyen, T. L. U.; Bennet, Francesca; Stenzel, Martina H.; Barner-Kowollik, Christopher

2008-01-01

This 8-hour experiment (spread over two 4-hour sessions) is designed to equip students with essential skills in polymer synthesis, particularly in synthesizing polymers of well-defined molecular weight. The experiment involves the synthesis and characterization of poly(vinyl neodecanoate) via living free radical polymerization, specifically the…

COMBINING ATOM TRANSFER RADICAL POLYMERIZATION AND DISULFIDE /THIOL REDOX CHEMISTRY: A ROUTE TO WELL-DEFINED (BIO)DEGRADABLE POLYMERIC MATERIALS. (R829580)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Homogeneous catalysts for stereoregular olefin polymerization

DOEpatents

Marks, Tobin J.; Eisen, Moris S.; Giardello, Michael A.

1995-01-01

The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C.sub.5 R'.sub.4-x R*.sub.x) A (C.sub.5 R".sub.4-y R"'.sub.y) M Q.sub.p, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R', R", R"', and R* represent substituted and unsubstituted alkyl groups having 1-30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3.ltoreq.p.ltoreq.o. Related complexes may be prepared by alkylation of the corresponding dichorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form "cation-like" species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other .alpha.-olefin polymerization can be effected with very high efficiency and isospecificity.

Homogeneous catalysts for stereoregular olefin polymerization

DOEpatents

Marks, Tobin J.; Eisen, Moris S.; Giardello, Michael A.

1994-01-01

The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C.sub.5 R'.sub.4-x R*.sub.x) A (C.sub.5 R".sub.4-y R'".sub.y) M Q.sub.p, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R', R", R'", and R* represent substituted and unsubstituted alkyl groups having 1-30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3.ltoreq.p.ltoreq.o. Related complexes may be prepared by alkylation of the corresponding dichorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form "cation-like" species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other .alpha.-olefin polymerization can be effected with very high efficiency and isospecificity.

Homogeneous catalysts for stereoregular olefin polymerization

DOEpatents

Marks, T.J.; Eisen, M.S.; Giardello, M.A.

1995-10-03

The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C{sub 5}R{prime}{sub 4{minus}x}R*{sub x})A(C{sub 5}R{double_prime}{sub 4{minus}y}R{double_prime}{prime}{sub y})MQ{sub p}, where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R{prime}, R{double_prime}, R{double_prime}{prime}, and R* represent substituted and unsubstituted alkyl groups having 1--30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3{>=}p{>=}0. Related complexes may be prepared by alkylation of the corresponding dichlorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form ``cation-like`` species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other {alpha}-olefin polymerization can be effected with very high efficiency and isospecificity. 1 fig.

Homogeneous catalysts for stereoregular olefin polymerization

DOEpatents

Marks, T.J.; Eisen, M.S.; Giardello, M.A.

1994-07-19

The synthesis, and use as precatalysts of chiral organozirconium complexes for olefin polymerization are disclosed, having the structure (C[sub 5]R[prime][sub 4[minus]x]R*[sub x])-A-(C[sub 5]R[double prime][sub 4[minus]y]R[prime][double prime][sub y])-M-Q[sub p], where x and y represent the number of unsubstituted locations on the cyclopentadienyl ring; R[prime], R[double prime], R[prime][double prime], and R* represent substituted and unsubstituted alkyl groups having 1--30 carbon atoms and R* is a chiral ligand; A is a fragment containing a Group 13, 14, 15, or 16 element of the Periodic Table; M is a Group 3, 4, or 5 metal of the Periodic Table; and Q is a hydrocarbyl radical, or halogen radical, with 3 [<=] p [<=] 0. Related complexes may be prepared by alkylation of the corresponding dichlorides. In the presence of methylalumoxane or triarylborane cocatalysts, these complexes form cation-like'' species which are highly active for olefin polymerization. In combination with a Lewis acid cocatalyst, propylene or other [alpha]-olefin polymerization can be effected with very high efficiency and isospecificity. 1 fig.

2-hydroxyethyl metahcrylate/gelatin based superporous hydrogels for tissue regeneration

NASA Astrophysics Data System (ADS)

Tomić, Simonida Lj.; Babić, Marija M.; Vuković, Jovana S.; Perišić, Marija D.; Filipović, Vuk V.; Davidović, Sladjana Z.; Filipović, Jovanka M.

2016-05-01

In this study, superporous hydrogels were synthesized by free radical polymerization of 2-hydroxyethyl methacrylate without and in the presence of gelatin. Highly porous hydrogel structures were obtained by two different techniques: using a gas blowing agent, sodium bicarbonate, and a cryogenic treatment followed by freeze-drying. After the gel synthesis, gelatin molecules were covalently immobilised onto PHEMA via glytaraldehyde activation. All samples were characterized for morphological, mechanical, swelling and antibacterial properties. The results obtained show that samples with gelatin show better properties in comparison with PHEMA samples, which make these materials highly attractive for developing hydrogel scaffolds for tissue regeneration.

Design, synthesis, and characterization of new phosphazene related materials, and study the structure property correlations

NASA Astrophysics Data System (ADS)

Tian, Zhicheng

The work described in this thesis is divided into three major parts, and all of which involve the exploration of the chemistry of polyphosphazenes. The first part (chapters 2 and 3) of my research is synthesis and study polyphoshazenes for biomedical applications, including polymer drug conjugates and injectable hydrogels for drug or biomolecule delivery. The second part (chapters 4 and 5) focuses on the synthesis of several organic/inorganic hybrid polymeric structures, such as diblock, star, brush and palm tree copolymers using living cationic polymerization and atom transfer radical polymerization techniques. The last part (chapters 6 and 7) is about exploratory synthesis of new polymeric structures with fluorinated side groups or cycloaliphatic side groups, and the study of new structure property relationships. Chapter 1 is an outline of the fundamental concepts for polymeric materials, as such the history, important definitions, and some introductory material for to polymer chemistry and physics. The chemistry and applications of phopshazenes is also briefly described. Chapter 2 is a description of the design, synthesis, and characterization of development of a new class of polymer drug conjugate materials based on biodegradable polyphosphazenes and antibiotics. Poly(dichlorophosphazene), synthesized by a thermal ring opening polymerization, was reacted with up to 25 mol% of ciprofloxacin or norfloxacin and three different amino acid esters (glycine, alanine, or phenylalanine) as cosubstituents via macromolecular substitutions. Nano/microfibers of several selected polymers were prepared by an electrospinning technique. Chapter 3 is concerned with the development of a class of injectable and biodegradable hydrogels based on water-soluble poly(organophosphazenes) containing oligo(ethylene glycol) methyl ethers and glycine ethyl esters. The hydrogels can be obtained by mixing alpha-cyclodextrin aqueous solution and poly(organophosphazenes) aqueous solution in various gelation rates depending on the polymer structures and the concentrations. The rheological measurements of the supramolecular hydrogels indicate a fast gelation process and flowable character under a large stain. Chapter 4 outlines the preparation of a number of amphiphilic diblock copolymers based on poly[bis(trifluoroethoxy)phosphazene] (TFE) as the hydrophobic block and poly(dimethylaminoethylmethacrylate) (PDMAEMA) as the hydrophilic block. The TFE block was synthesized first by the controlled living cationic polymerization of a phosphoranimine, followed by replacement of all the chlorine atoms using sodium trifluoroethoxide. To allow for the growth of the PDMAEMA block, 3-azidopropyl-2-bromo-2-methylpropanoate, an atom transfer radical polymerization (ATRP) initiator, was grafted onto the endcap of the TFE block via the 'click' reaction followed by the ATRP of 2-(dimethylamino)ethyl methacrylate (DMAEMA). Chapter 5 is a report on the design and assembly of polyphosphazene materials based on the non-covalent "host--guest" interactions either at the terminus of the polymeric main-chains or the pendant side-chains. The supramolecular interaction at the main chain terminus was used to produce amphiphilic palm-tree like pseudo-block copolymers via host-guest interactions between an adamantane end-functionalized polyphosphazene and a 4-armed beta-cyclodextrin (beta-CD) initiated poly[poly(ethylene glycol) methyl ether methacylate] branched-star type polymer. The formation of micelles of the obtained amphiphiles was analyzed by fluorescence technique, dynamic light scattering, transmission electron microscopy, and atomic force microscopy. Chapter 6 is an investigation of the influence of bulky fluoroalkoxy side groups on the properties of polyphosphazenes. A new series of mixed-substituent high polymeric poly(fluoroalkoxyphosphazenes) containing trifluoroethoxy and branched fluoroalkoxy side groups was synthesized and characterized by NMR and GPC methods. These polymers contained 19--29 mol% of di-branched hexafluoropropoxy groups or 4mol% of tri-branched tert-perfluorobutoxy groups, which serve as regio-irregularities to reduce the macromolecular microcrystallinity. The structure--property correlations of the polymers were then analyzed and interpreted by several techniques: specifically by the thermal behavior by DSC and TGA methods, the crystallinity by wide-angle X-ray diffraction, and the surface hydrophobicity/oleophobicity by contact angle measurements. (Abstract shortened by UMI.). Chapter 7 is an outline of the exploratory synthesis of a new series of phosphazene model cyclic trimers and single- and mixed- substituent high polymers containing cyclic aliphatic rings, --CnH2n-1 (where n = 4--8). The cylco-aliphatic side group containing phosphazenes expand the structural and property boundaries of phosphazene chemistry, and suggest additional approaches for studying slow macromolecular substitution reactions and substituent exchange reactions.

Microgel coating of magnetic nanoparticles via bienzyme-mediated free-radical polymerization for colorimetric detection of glucose

NASA Astrophysics Data System (ADS)

Wu, Qing; Wang, Xia; Liao, Chuanan; Wei, Qingcong; Wang, Qigang

2015-10-01

This study describes a new strategy for the fabrication of magnetic core-shell microgels by free-radical polymerization triggered by the cascade reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP). The mild polymerization around the interface of the magnetic nanoparticles permits the mild coating of the microgel layer with excellent characteristics for various applications in biocatalysis and medical diagnostics, as well as in clinical fields. The immobilized bienzyme within the microgel has a largely retained activity relative to the non-immobilized one. The confining effect of the microgel and the well designed distance between the two enzymes can benefit the diffusion of intermediates to the HRP active site. The final microgels can be incontestably employed as sensitive biosensors for colorimetric glucose detection.This study describes a new strategy for the fabrication of magnetic core-shell microgels by free-radical polymerization triggered by the cascade reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP). The mild polymerization around the interface of the magnetic nanoparticles permits the mild coating of the microgel layer with excellent characteristics for various applications in biocatalysis and medical diagnostics, as well as in clinical fields. The immobilized bienzyme within the microgel has a largely retained activity relative to the non-immobilized one. The confining effect of the microgel and the well designed distance between the two enzymes can benefit the diffusion of intermediates to the HRP active site. The final microgels can be incontestably employed as sensitive biosensors for colorimetric glucose detection. Electronic supplementary information (ESI) available: Experimental details and ESI figures. See DOI: 10.1039/c5nr05716g

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.

Stable polymeric carbon radicals. Part 2: Attempts at the preparation of polyradicals of the triphenylmethyl type linked by P-phenylene units

NASA Technical Reports Server (NTRS)

Braun, D.; Lehmann, P.

1985-01-01

As starting materials for the preparation of polyradicals of triphenylmethyl type linked by p-phenylene units bis(4-iodophenylmethane) and bis(4-iodo-2,5-dimethyl-phenylmethane) were synthesized by a Sandmeyer reaction from the corresponding diamino compounds and subsequently transformed into the corresponding polymeric hydrocarbons 6a and 6b by an Ullmann condensation. In the following step 6a and 6b were brominated at the tert. carbon atom by means of N-bromosuccinimide. The reaction of the resulting poly (4,4'-biphenylylen-alpha-bromobenzylidene)s (7a and 7b) with mercury afforded the corresponding radicals, the ESR spectra of which were recorded. From the methyl substituted polymer 7b poly (2,2'5,5-tetramethyl-4,4'-bi-phenylylen)phenylmethylidyne was formed, whereas the unsubstituted product 7a was transformed into a para-quinoide polymer with radical properties.

Development of materials from copolyacrylates via atom transfer radical polymerization

NASA Astrophysics Data System (ADS)

Jones, Melody Mersadez

Homopolymerization of 2-(trimethylsilyl)ethyl acrylate, 3,3-dimethylbutyl acrylate, methyl acrylate, and methyl methacrylate using atom transfer radical polymerization (ATRP) is reported. In addition, polymethyl acrylate and polymethyl methacrylate were used as macroinitiators for diblock copolymerizations (via ATRP) with various monomers to yield pMA-b-TMSEA, pMMA-b-TMSEA, and pMMA-b-GMA copolymers; these results are also reported. Controlled polymerizations were performed using the CuBr/hexamethyltriethylenetetramine catalyst system in combination with methyl bromopropionate as the initiator. The protected acid block copolymers pMA-b-TMSEA and pMMA-b-TMSEA were deprotected to afford acrylic and meth acrylic acid block copolymers pMA-b-AA and pMMA-b-AA. Methylene chloride was used to micellize the amphiphilic copolymers in order to obtain the critical micelle concentration of the polymers (CMCpMA-b-AA = 10 mg/mL, CMCpMMA-b-AA = 0.4 mg/mL). The majority of polymerization were done in bulk; however, since poly(trimethylsilyl)ethyl acrylate displayed polydispersity (Mn = 11459, PDI = 1.437) on the high end of the acceptable range, various solvents were utilized to decrease the polymerization rate and afford low polydispersity materials. This differs from the ATRP of polymethyl acrylate or polymethyl methacrylate using this catalytic system, which do not require the addition of a solvent to obtain well-defined polymers. Also, for this polymerization system three different temperatures (60°C, 90°C, and 120°C) were used, in order to reduce the concentration of radicals and the contribution of termination. The homopolymers and protected acid block copolymers were characterized by gel permeation chromatography to determine the relative molecular weights. Differential scanning calorimetry was used to obtain the glass transition temperature of all polymers. Characterization using NMR (1H and 13C) and FTIR confirmed homopolymerization of 3,3-dimethylbutyl acrylate, 2-(trimethylsilyl)ethyl acrylate and complete cleavage of the (trimethylsilyl)ethyl group from the protected acid copolymers.

Molecular architecture requirements for polymer-grafted lignin superplasticizers.

PubMed

Gupta, Chetali; Sverdlove, Madeline J; Washburn, Newell R

2015-04-07

Superplasticizers are a class of anionic polymer dispersants used to inhibit aggregation in hydraulic cement, lowering the yield stress of cement pastes to improve workability and reduce water requirements. The plant-derived biopolymer lignin is commonly used as a low-cost/low-performance plasticizer, but attempts to improve its effects on cement rheology through copolymerization with synthetic monomers have not led to significant improvements. Here we demonstrate that kraft lignin can form the basis for high-performance superplasticizers in hydraulic cement, but the molecular architecture must be based on a lignin core with a synthetic-polymer corona that can be produced via controlled radical polymerization. Using slump tests of ordinary Portland cement pastes, we show that polyacrylamide-grafted lignin prepared via reversible addition-fragmentation chain transfer polymerization can reduce the yield stress of cement paste to similar levels as a leading commercial polycarboxylate ether superplasticizer at concentrations ten-fold lower, although the lignin material produced via controlled radical polymerization does not appear to reduce the dynamic viscosity of cement paste as effectively as the polycarboxylate superplasticizer, despite having a similar affinity for the individual mineral components of ordinary Portland cement. In contrast, polyacrylamide copolymerized with a methacrylated kraft lignin via conventional free radical polymerization having a similar overall composition did not reduce the yield stress or the viscosity of cement pastes. While further work is required to elucidate the mechanism of this effect, these results indicate that controlling the architecture of polymer-grafted lignin can significantly enhance its performance as a superplasticizer for cement.

Spatially controlled, in situ synthesis of polymers

DOEpatents

Caneba, Gerard T.; Tirumala, Vijaya Raghavan; Mancini, Derrick C.; Wang, Hsien-Hau

2005-03-22

An in situ polymer microstructure formation method. The monomer mixture is polymerized in a solvent/precipitant through exposure to ionizing radiation in the absence any chemical mediators. If an exposure mask is employed to block out certain regions of the radiation cross section, then a patterned microstructure is formed. The polymerization mechanism is based on the so-called free-radical retrograde-precipitation polymerization process, in which polymerization occurs while the system is phase separating above the lower critical solution temperature. This method was extended to produce a crosslinked line grid-pattern of poly (N-isopropylacrylamide), which has been known to have thermoreversible properties.

Radical graft polymerization of an Allyl Monomer onto Hydrophilic Polymers and their antibacterial nanofibrous membranes

USDA-ARS?s Scientific Manuscript database

Hydrophilic poly (vinyl alcohol-co-ethylene) (PVA-co-PE) copolymers with 27 mol %, 32 mol % and 44 mol % ethylene were functionalized by melt radical graft copolymerization with 2,4-diamino-6-diallylamino-1,3,5-triazine (NDAM) using reactive extrusion. This functionalization imparts antibacterial pr...

Improving the organic and biological fouling resistance and removal of pharmaceutical and personal care products through nanofiltration by using in situ radical graft polymerization.

PubMed

Lin, Yi-Li; Tsai, Chia-Cheng; Zheng, Nai-Yun

2018-09-01

In this study, an insitu radical graft polarization technique using monomers of 3-sulfopropyl methacrylate potassium salt (SPM) and 2-hydroxyethyl methacrylate (HEMA) was applied to a commercial nanofiltration membrane (NF90) to improve its removal of six commonly detected pharmaceutical and personal care products (PPCPs) and mitigate organic and biological fouling by humic acid (HA) and sodium alginate (SA). Compared with the virgin membrane, the modified NF90 membrane exhibited considerably improved fouling resistance and an increased reversible fouling percentage, especially for SA+HA composite fouling Moreover, the PPCP removal of the modified NF90 membrane was higher than that of the virgin membrane after SA and SA+HA fouling, respectively. Triclosan and carbamazepine, which are poorly rejected, could be effectively removed by modified membrane after SA or SA+HA fouling. Both monomers modified the membrane surface by increasing the hydrophilicity and decreasing the contact angle. The degree of grafting was quantified using attenuated total reflection Fourier-transform infrared spectroscopy. The mitigation in the fouling was evident from the low quantity of deposit formed on the modified membrane, as observed using scanning electron microscopy. A considerable amount of highly hydrophobic triclosan was adsorbed on the SA-fouled virgin membrane and penetrated through it. By contrast, the adsorption of triclosan was substantially lower in the SPM-modified membrane. After membrane modification, the fouling mechanism changed from solely intermediate blocking to both intermediate blocking and complete blocking after membrane modification. Thus, the in situ radical graft polymerization method effectively reduces organic and biological fouling and provides high PPCP removal, which is beneficial for fouling control and produces permeate of satisfactory quality for application in the field of membrane technology. Copyright © 2018 Elsevier B.V. All rights reserved.

An Engineered Monolignol 4-O-Methyltransferase Depresses Lignin Biosynthesis and Confers Novel Metabolic Capability in Arabidopsis[C][W][OA

PubMed Central

Zhang, Kewei; Bhuiya, Mohammad-Wadud; Pazo, Jorge Rencoret; Miao, Yuchen; Kim, Hoon; Ralph, John; Liu, Chang-Jun

2012-01-01

Although the practice of protein engineering is industrially fruitful in creating biocatalysts and therapeutic proteins, applications of analogous techniques in the field of plant metabolic engineering are still in their infancy. Lignins are aromatic natural polymers derived from the oxidative polymerization of primarily three different hydroxycinnamyl alcohols, the monolignols. Polymerization of lignin starts with the oxidation of monolignols, followed by endwise cross-coupling of (radicals of) a monolignol and the growing oligomer/polymer. The para-hydroxyl of each monolignol is crucial for radical generation and subsequent coupling. Here, we describe the structure-function analysis and catalytic improvement of an artificial monolignol 4-O-methyltransferase created by iterative saturation mutagenesis and its use in modulating lignin and phenylpropanoid biosynthesis. We show that expressing the created enzyme in planta, thus etherifying the para-hydroxyls of lignin monomeric precursors, denies the derived monolignols any participation in the subsequent coupling process, substantially reducing lignification and, ultimately, lignin content. Concomitantly, the transgenic plants accumulated de novo synthesized 4-O-methylated soluble phenolics and wall-bound esters. The lower lignin levels of transgenic plants resulted in higher saccharification yields. Our study, through a structure-based protein engineering approach, offers a novel strategy for modulating phenylpropanoid/lignin biosynthesis to improve cell wall digestibility and diversify the repertories of biologically active compounds. PMID:22851762

Polymerization of ethylene through reversible addition-fragmentation chain transfer (RAFT).

PubMed

Dommanget, Cédric; D'Agosto, Franck; Monteil, Vincent

2014-06-23

The present paper reports the first example of a controlled radical polymerization of ethylene using reversible addition-fragmentation chain transfer (RAFT) in the presence of xanthates (Alkyl-OC(=S)S-R) as controlling agents under relative mild conditions (70 °C, <200 bars). The specific reactivity of the produced alkyl-type propagating radicals induces a side fragmentation reaction of the stabilizing O-alkyl Z group of the controlling agents. This fragmentation, rarely observed in RAFT, was proven by NMR analyses. In addition, semicrystalline copolymers of ethylene and vinyl acetate were also prepared with a similar level of control. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polyethylene glycol grafted polyethylene: a versatile platform for nonmigratory active packaging applications.

PubMed

Barish, Jeffrey A; Goddard, Julie M

2011-01-01

Nonmigratory active packaging, in which bioactive components are tethered to the package, offers the potential to reduce the need for additives in food products while maintaining safety and quality. A challenge in developing nonmigratory active packaging materials is the loss of biomolecular activity that can occur when biomolecules are immobilized. In this work, we describe a method in which a biocompatible polymer (polyethylene glycol, PEG) is grafted from the surface of ozone-treated low-density polyethylene (LDPE) resulting in a surface functionalized polyethylene to which a range of amine-terminated bioactive molecules can be immobilized. Free radical graft polymerization is used to graft PEG onto the LDPE surface, followed by immobilization of ethylenediamine onto the PEG tether. Ethylenediamine was used to demonstrate that amine-terminated molecules could be covalently attached to the PEG-grafted film. Changes in surface chemistry and topography were measured by attenuated total reflectance Fourier transform infrared spectroscopy, contact angle, atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. We demonstrate the ability to graft PEG onto the surface of polymer packaging films by free radical graft polymerization, and to covalently link an amine-terminated molecule to the PEG tether, demonstrating that amine-terminated bioactive compounds (such as peptides, enzymes, and some antimicrobials) can be immobilized onto PEG-grafted LDPE in the development of nonmigratory active packaging.   Nonmigratory active packaging offers the potential for improving food safety and quality while minimizing the migration of the active agent into food. In this paper, we describe a technique to modify polyethylene packaging films such that active agents can be covalently immobilized by a biocompatible tether. Such a technique can be adapted to a number of applications such as antimicrobial, antioxidant, or immobilized enzyme active packaging. © 2011 Institute of Food Technologists®

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.

Anionic polymerization of p-(2,2'-diphenylethyl)styrene and applications to graft copolymers.

PubMed

Huang, Minglu; Han, Bingyong; Lu, Jianmin; Yang, Wantai; Fu, Zhifeng

2017-01-01

Well-controlled anionic polymerization of an initiator-functionalized monomer, p -(2,2'-diphenylethyl)styrene (DPES), was achieved for the first time. The polymerization was performed in a mixed solvent of cyclohexane and tetrahydrofuran (THF) at 40 °C with n -BuLi as initiator. When the volume ratio of cyclohexane to THF was 20, the anionic polymerization of DPES showed living polymerization characteristics, and well-defined block copolymer PDPES- b -PS was successfully synthesized. Furthermore, radical polymerization of methyl methacrylate in the presence of PDPES effectively afforded a graft copolymer composed of a polystyrene backbone and poly(methyl methacrylate) branches. The designation of analogous monomers and polymers was of great significance to synthesize a variety of sophisticated copolymer and functionalize polymer materials.

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.

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.

Application of controlled radical polymerization (CRP) in the design of functional biomedical architectures

NASA Astrophysics Data System (ADS)

Siegwart, Daniel John

In this thesis, atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization were utilized in the design of synthetic polymers to create tissue engineering scaffolds and drug delivery systems with improved control over structure and functionality. Thermo-sensitive injectable hydrogels based on poly(NIPAAm) with degradable ester units within the polymer backbone and at the cross-linking sites were prepared using ATRP and RAFT. Solvent induced morphologies of poly(methyl methacrylate-b-ethylene oxide-b-methyl methacrylate) triblock copolymers synthesized by ATRP were described. A micellar structure, composed of a hydrophobic PMMA core and a PEO shell was constructed for delivery of hydrophobic drugs. ATRP was carried out in inverse miniemulsion to prepare well defined functional nanogels that were capable of entrapping and releasing various molecules (Doxorubicin, carbohydrate-based drugs, fluorophores, and gold nanoparticles). The results demonstrated that nanogels prepared by ATRP in inverse miniemulsion could be internalized into cells via clathrin-mediated endocytosis. Nanogels functionalized with integrin-binding peptides increased cellular uptake. A process called Atom Transfer Radical Coupling (ATRC) was also described, which illustrated the power of functionality in ATRP. Finally, linear polymers and cross-linked nanogels were synthesized by ATRP and functionalized with biotin, pyrene, and peptide sequences, tying together the overall themes of structural control and functionality.

Study on the role of active radicals on plasma sterilization inside small diameter flexible polymeric tubes

NASA Astrophysics Data System (ADS)

Mstsuura, Hiroto; Fujiyama, Takatomo; Okuno, Yasuki; Furuta, Masakazu; Okuda, Shuichi; Takemura, Yuichiro

2015-09-01

Recently, atmospheric pressure discharge plasma has gathered attention in various fields. Among them, plasma sterilization with many types of plasma source has studied for decades and its mechanism is still an open question. If active radicals produced in plasma has main contribution of killing bacterias, direct contact of the so-called plasma flame might not be necessary. To confirm this, sterilization inside small diameter flexible polymeric tubes is studied in present work. DBD type plasma jet is produce by flowing helium gas in a glass tube. A long polymeric tube is connected and plasma jet is introduced into it. Plasma flame length depends on helium gas flow rate, but limited to about 10 cm in our experimental condition. E.colis set at the exit plasma source is easily killed during 10 min irradiation. At the tube end (about 20 cm away from plasma source exit), sterilization is possible with 30 min operation. This result shows that active radical is produced with helium plasma and mist contained in sample, and it can be transferred more than 20 cm during it life time. More plasma diagnostic data will also be shown at the conference. This work was partially supported by the ''ZE Research Program, IAE(ZE27B-4).

Scavenging of free-radical metabolites of aniline xenobiotics and drugs by amino acid derivatives: toxicological implications of radical-transfer reactions.

PubMed

Michail, Karim; Baghdasarian, Argishti; Narwaley, Malyaj; Aljuhani, Naif; Siraki, Arno G

2013-12-16

We investigated a novel scavenging mechanism of arylamine free radicals by poly- and monoaminocarboxylates. Free radicals of arylamine xenobiotics and drugs did not react with oxygen in peroxidase-catalyzed reactions; however, they showed marked oxygen uptake in the presence of an aminocarboxylate. These free-radical intermediates were identified using the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and electron paramagnetic resonance (EPR) spectrometry. Diethylenetriaminepentaacetic acid (DTPA), a polyaminocarboxylate, caused a concentration-dependent attenuation of N-centered radicals produced by the peroxidative metabolism of arylamines with the subsequent formation of secondary aliphatic carbon-centered radicals stemming from the cosubstrate molecule. Analogously, N,N-dimethylglycine (DMG) and N-methyliminodiacetate (MIDA), but not iminodiacetic acid (IDA), demonstrated a similar scavenging effect of arylamine-derived free radicals in a horseradish peroxidase/H2O2 system. Using human promyelocytic leukemia (HL-60) cell lysate as a model of human neutrophils, DTPA, MIDA, and DMG readily reduced anilinium cation radicals derived from the arylamines and gave rise to the corresponding carbon radicals. The rate of peroxidase-triggered polymerization of aniline was studied as a measure of nitrogen-radical scavenging. Although, IDA had no effect on the rate of aniline polymerization, this was almost nullified in the presence of DTPA and MIDA at half of the molar concentration of the aniline substrate, whereas a 20 molar excess of DMPO caused only a partial inhibition. Furthermore, the yield of formaldehyde, a specific reaction endproduct of the oxidation of aminocarboxylates by aniline free-radical metabolites, was quantitatively determined. Azobenzene, a specific reaction product of peroxidase-catalyzed free-radical dimerization of aniline, was fully abrogated in the presence of DTPA, as confirmed by GC/MS. Under aerobic conditions, a radical-transfer reaction is proposed between aminocarboxylates and arylamine free radicals via the carboxylic group-linked tertiary nitrogen of the deprotonated amino acid derivatives. These findings may have significant implications for the biological fate of arylamine xenobiotic and drug free-radical metabolites.

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.

Well-Defined Macromolecules Using Horseradish Peroxidase as a RAFT Initiase.

PubMed

Danielson, Alex P; Bailey-Van Kuren, Dylan; Lucius, Melissa E; Makaroff, Katherine; Williams, Cameron; Page, Richard C; Berberich, Jason A; Konkolewicz, Dominik

2016-02-01

Enzymatic catalysis and control over macromolecular architectures from reversible addition-fragmentation chain transfer polymerization (RAFT) are combined to give a new method of making polymers. Horseradish peroxidase (HRP) is used to catalytically generate radicals using hydrogen peroxide and acetylacetone as a mediator. RAFT is used to control the polymer structure. HRP catalyzed RAFT polymerization gives acrylate and acrylamide polymers with relatively narrow molecular weight distributions. The polymerization is rapid, typically exceeding 90% monomer conversion in 30 min. Complex macromolecular architectures including a block copolymer and a protein-polymer conjugate are synthesized using HRP to catalytically initiate RAFT polymerization. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sulfonated amphiphilic block copolymers : synthesis, self-assembly in water, and application as stabilizer in emulsion polymerization

Treesearch

Jiguang Zhang; Matthew R. Dubay; Carl J. Houtman; Steven J. Severtson

2009-01-01

Described is the synthesis of diblock copolymers generated via sequential atom transfer radical polymerization (ATRP) of poly(n-butyl acrylate) (PnBA) followed by chain augmentation with either sulfonated poly(2-hydroxyethyl methacrylate) (PHEMA) or poly(2-hydroxyethyl acrylate) (PHEA) blocks. ATRP of PHEMA or PHEA from PnBA macroinitiator was conducted in acetone/...

Controlled aqueous polymerization of acrylamides and acrylates and "in situ" depolymerization in the presence of dissolved CO2.

PubMed

Lloyd, Danielle J; Nikolaou, Vasiliki; Collins, Jennifer; Waldron, Christopher; Anastasaki, Athina; Bassett, Simon P; Howdle, Steven M; Blanazs, Adam; Wilson, Paul; Kempe, Kristian; Haddleton, David M

2016-05-05

Aqueous copper-mediated radical polymerization of acrylamides and acrylates in carbonated water resulted in high monomer conversions (t < 10 min) before undergoing depolymerization (60 min > t > 10 min). The regenerated monomer was characterized and repolymerized following deoxygenation of the resulting solutions to reyield polymers in high conversions that exhibit low dispersities.

pH dependent antioxidant activity of lettuce (L. sativa) and synergism with added phenolic antioxidants.

PubMed

Altunkaya, Arzu; Gökmen, Vural; Skibsted, Leif H

2016-01-01

Influence of pH on the antioxidant activities of combinations of lettuce extract (LE) with quercetin (QC), green tea extract (GTE) or grape seed extract (GSE) was investigated for both reduction of Fremy's salt in aqueous solution using direct electron spin resonance (ESR) spectroscopy and in L-α-phosphatidylcholine liposome peroxidation assay measured following formation of conjugated dienes. All examined phenolic antioxidants showed increasing radical scavenging effect with increasing pH values by using both methods. QC, GTE and GSE acted synergistically in combination with LE against oxidation of peroxidating liposomes and with QC showing the largest effect. The pH dependent increase of the antioxidant activity of the phenols is due to an increase of their electron-donating ability upon deprotonation and to their stabilization in alkaline solutions leading to polymerization reaction. Such polymerization reactions of polyphenolic antioxidants can form new oxidizable -OH moieties in their polymeric products resulting in a higher radical scavenging activity. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

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

End-group-functionalized poly(N,N-diethylacrylamide) via free-radical chain transfer polymerization: Influence of sulfur oxidation and cyclodextrin on self-organization and cloud points in water

PubMed Central

Reinelt, Sebastian; Steinke, Daniel

2014-01-01

Summary In this work we report the synthesis of thermo-, oxidation- and cyclodextrin- (CD) responsive end-group-functionalized polymers, based on N,N-diethylacrylamide (DEAAm). In a classical free-radical chain transfer polymerization, using thiol-functionalized 4-alkylphenols, namely 3-(4-(1,1-dimethylethan-1-yl)phenoxy)propane-1-thiol and 3-(4-(2,4,4-trimethylpentan-2-yl)phenoxy)propane-1-thiol, poly(N,N-diethylacrylamide) (PDEAAm) with well-defined hydrophobic end-groups is obtained. These end-group-functionalized polymers show different cloud point values, depending on the degree of polymerization and the presence of randomly methylated β-cyclodextrin (RAMEB-CD). Additionally, the influence of the oxidation of the incorporated thioether linkages on the cloud point is investigated. The resulting hydrophilic sulfoxides show higher cloud point values for the lower critical solution temperature (LCST). A high degree of functionalization is supported by 1H NMR-, SEC-, FTIR- and MALDI–TOF measurements. PMID:24778720

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.

Free-radical concentrations and other properties of pile-irradiated coals

USGS Publications Warehouse

Friedel, R.A.; Breger, I.A.

1959-01-01

Five coals reacted quite differently when they were exposed to pile-irradiation. Little or no change was found in free-radical content for the three coals of lowest carbon content, whereas the two coals of highest carbon content were found to have a considerable increase in free-radical content. The infrared spectra and the apparent hardness of the irradiated coals of higher carbon content indicate that polymerization occurred. Radiation of these coals in chemical reagents may promote reactivity.

Folate-conjugated pH-responsive nanocarrier designed for active tumor targeting and controlled release of doxorubicin

NASA Astrophysics Data System (ADS)

Wei, Lulu; Lu, Beibei; Cui, Lin; Peng, Xueying; Wu, Jianning; Li, Deqiang; Liu, Zhiyong; Guo, Xuhong

2017-12-01

A novel type of amphiphilic pH-responsive folate-poly(ɛ-caprolactone)- block-poly(2-hydroxyethylmethacrylate)- co-poly(2-(dimethylamino)-ethylmethacrylate) (FA-PCL- b-P(HEMA- co-DMAEMA)) (MFP) block copolymers were designed and synthesized via atom transfer radical polymerization (ATRP) and ring opening polymerization (ROP) techniques. The molecular structures of the copolymers were confirmed with 1H NMR, FTIR and GPC measurements. The critical micelle concentration (CMC) of MFP in aqueous solution was extremely low (about 6.54 mg/L). The in vitro release behavior of DOX-loaded micelles was significantly accelerated when the pH value of solution decreased from 7.4 to 5.0. In vitro antitumor efficiency was evaluated by incubating DOX-loaded micelles with Hela cells. The results demonstrated that this copolymer possessed excellent biocompatibility, and FA-decorated micelles MFP showed higher cellular uptake than those micelles without the FA moiety, indicating their unique targetability. These folate-conjugated biodegradable micelles are highly promising for targeted cancer chemothe-rapy.

Europium-doped aluminum oxide phosphors as indicators for frontal polymerization dynamics

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

Carranza, Arturo; Gewin, Mariah; Pojman, John A., E-mail: japojman@lsu.edu

2014-06-15

In this study, we present an inexpensive and practical method that allows the monitoring and visualization of front polymerization, propagation, and dynamics. Commercially available europium-doped aluminum oxide powders were combined with video imaging to visualize free-radical propagating polymer fronts. In order to demonstrate the applicability of this method, frontal copolymerization reactions of propoxylated glycerin triacrylate (EB53), pentaerythritol triacrylate (PETA), and pentaerythritol tetra-acrylate (PETEA) with 1,1-Bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane (Luperox 231®) as an initiator were studied and compared to the results obtained by IR imaging. Systems exhibiting higher filler loading, higher EB53 content, and less acrylated monomers showed a marked decrease in front velocity,more » while those with more acrylated monomers and higher crosslinking density showed a marked increase in front velocity. Finally, in order to show the potential of the imaging technique, we studied fronts propagating in planar and spherical geometries.« less

TiO2 reinforced PMMA-TiO2 nanocomposite for its application in organic light emitting diode (OLED) as electron transport layer material

NASA Astrophysics Data System (ADS)

Kandulna, R.; Choudhary, R. B.; Singh, R.

2018-04-01

PMMA, TiO2 and PMMA-TiO2 nanocomposite were successfully synthesized in the laboratory via free radical polymerization process. The formation of PMMA corresponding change in the nanostructure with the embodiment of TiO2 nanofillers was confirmed by X-ray diffraction technique (XRD) analysis. Irregular tetragonal bipyramidal arrangement of TiO2 was formed within the spherical type structure of PMMA polymeric matrix, as examined by the surface morphological image. Relatively higher electron-hole non-radiative recombination of PMMA-TiO2 nanocomposite corresponded to blue-violet band, blue band, and green band was examined from PL spectra. An enhanced current density ˜ 165 % was observed with significantly improved p-type conductivity for PMMA-TiO2 nanocomposite. The improved specific capacitance with high dielectric constant and high electron-hole recombination rate confirmed that it can possibly use as electron transport layer material in the OLED devices fabrication.

Non-thermal atmospheric pressure plasma source techniques on 3,7- bis (dimethylamino)-phenothiazin-5-ium chloride

NASA Astrophysics Data System (ADS)

Kotowich, Steven

Studies of a non-thermal atmospheric pressure plasma source on an organic heterocycle were conducted to determine reaction parameters and rearrangement conditions. The target compound 3,7-bis(dimethylamino)-phenothiazin-5-ium chloride, commonly referred to as methylene blue, was determine to polymerize after exposure to a non-thermal atmospheric pressure plasma source. The presence of charge retention and a free electron radical were detected inherent to the polymer. Evaluation of the structure and mechanism of the polymer were also presented for evidence and clarification. Additional description of the plasma source environment was correlated to the manipulation of the target compound.

Application of pseudo-template molecularly imprinted polymers by atom transfer radical polymerization to the solid-phase extraction of pyrethroids.

PubMed

Zhang, Ming; He, Juan; Shen, Yanzheng; He, Weiye; Li, Yuanyuan; Zhao, Dongxin; Zhang, Shusheng

2018-02-01

A polymer-based adsorption medium with molecular recognition ability for homologs of pyrethroids was prepared by atom transfer radical polymer iration using a fragment imprinting technique. Phenyl ether-biphenyl eutectic was utilized as a pseudo-template molecule, and the adsorption medium prepared was evaluated by solid-phase extraction and gas chromatography. Selectivity of the medium for pyrethroids was evaluated using it as solid phase extraction packing by Gas Chromatography. The results demonstrated that the absorption amount of bifenthrin, fenpropathrin, permethrin, cypermethrin, fenvalerate, Dursban and pentachloronitrobenzene for molecularly imprinted polymers were 2.32, 2.12, 2.18, 2.20, 2.30, 1.30 and 1.40mgg -1 , respectively, while the non-imprinted polymers were 1.20, 1.13, 1.25, 1.05, 1.20, 1.23 and 1.32mgg -1 , respectively. The rebinding test based on the molecularly imprinted solid phase extraction column technique showed the recoveries of honey sample spiked with seven insecticides within 88.5-106.2%, with relative standard deviations of 2.38-5.63%. Finally, the method was successfully applied to the analysis of pyrethroids in a honey sample. Copyright © 2017 Elsevier B.V. All rights reserved.

Composition and method of preparation of solid state dye laser rods

DOEpatents

Hermes, Robert E.

1992-01-01

The present invention includes solid polymeric-host laser rods prepared using bulk polymerization of acrylic acid ester comonomers which, when admixed with dye(s) capable of supporting laser oscillation and polymerized with a free radical initiator under mild thermal conditions, produce a solid product having the preferred properties for efficient lasing. Unsaturated polymerizable laser dyes can also be employed as one of the comonomers. Additionally, a method is disclosed which alleviates induced optical stress without having to anneal the polymers at elevated temperatures (>85.degree. C.).

Survey Study of Trunk Materials for Direct ATRP Grafting

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

Saito, Tomonori; Chatterjee, Sabornie; Johnson, Joseph C.

2015-02-01

In previous study, we demonstrated a new method to prepare polymeric fiber adsorbents via a chemical-grafting method, namely atom-transfer radical polymerization (ATRP), and identified parameters affecting their uranium adsorption capacity. However, ATRP chemical grafting in the previous study still utilized conventional radiation-induced graft polymerization (RIGP) to introduce initiation sites on fibers. Therefore, the objective of the present study is to perform survey study of trunk fiber materials for direct ATRP chemical grafting method without RIGP for the preparation of fiber adsorbents for uranium recovery from seawater.

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.

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

Y Hu; D Samanta; S Parelkar

Controlled free radical polymerization chemistry is used to graft polymer chains to the corona of horse spleen ferritin (HSF) nanocages. Specifically, poly(methacryloyloxyethyl phosphorylcholine) (polyMPC) and poly(PEG methacrylate) (polyPEGMA) chains are grafted onto the nanocages by atom transfer radical polymerization (ATRP), in which the molecular weight of the polymer grafts is controlled by the monomer-to-initiator feed ratio. PolyMPC and polyPEGMA-grafted ferritin show a generally suppressed inclusion into diblock copolymer films relative to native ferritin, and the polymer coating is seen to mask the ferritin nanocages from antibody recognition. The solubility of polyPEGMA-coated ferritin in organic solvents enables its processing with polystyrene-block-poly(ethylenemore » oxide) copolymers, and selective integration into the PEO domains of microphase-separated copolymer structures.« less

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.

Two new Ni(II) supramolecular complexes based on ethyl isonicotinate and ethyl nicotinate for removal of acid blue 92 dye

NASA Astrophysics Data System (ADS)

Etaiw, Safaa El-din H.; Marie, Hassan

2018-03-01

Two new luminescent supramolecular complexes (SC); [Ni(EIN)4(NCS)2] SC1 and [Ni2(EN)8(NCS)4] SC2, (EIN = ethyl isonicotinate, EN = ethyl nicotinate), have been synthesized by self-assembly method and structurally characterized by X-ray single crystal, FT-IR and UV-Vis spectra, PXRD, elemental and thermogravimetric analyses. Both SC1 and SC2 are monoclinic crystals however, they have different asymmetric units. Ni(II) atoms in both SC are isostructural and have similar hexa-coordinate environment. The structures of SC1 and SC2 consist of parallel polymeric 1D-chains, extended in two and three dimensional supramolecular frameworks by intermolecular hydrogen bonding interactions. SC1 and SC2 are luminescent materials which can be used in applications as molecular sensing systems. SC1 and SC2 were used as heterogeneous catalysts for degradation of acid blue 92 (AB-92) under sun light irradiation. The fluorescence measurements of terephthalic acid technique as a probe molecule were used to determine the •OH radicals. Also the radicals trapping experiments using isopropanol alcohol (IPA) as radical scavenger were discussed. In addition a mechanism of degradation was proposed and discussed.

Presidential Green Chemistry Challenge: 2009 Academic Award

EPA Pesticide Factsheets

Presidential Green Chemistry Challenge 2009 award winner, Professor Krzysztof Matyjaszewski, developed Atom Transfer Radical Polymerization to make polymers with copper catalysts and environmentally friendly reducing agents.

Functionalized Nano and Micro Structured Composite Coatings

DTIC Science & Technology

2011-06-01

created. Contact angles for water, hexadecane and warfare simulants (tributyl phosphate (TBP), methyl salicylate (MS) and 2-chloroethyl ethyl sulfide... methyl salicylate PAA-POEGMA polyacrylic acid-co-poly(oligoethylene glycol methacrylate) PBMA poly(butyl methacrylate) PD-TDES commercial mixture of...polymerized radically (according to a procedure published elsewhere1) to give PGMA, Mn = 300,000 kDa, PDI = 2. The polymerization was carried out in methyl

Hydrocarbon polymeric binder for advanced solid propellant

NASA Technical Reports Server (NTRS)

Potts, J. E. (Editor); Ashcraft, A. C., Jr.; Wise, E. W.

1971-01-01

The results of curing vinyl alcohol terpolymers of ethylene, propylene and vinyl acetate are reported for an average functionality of 1.24 when reacted with an equivalent amount of diisocynate, and saturated polyisoprene derivative is described having terminal methyl ester functionality. The development is reported of two hydroxy-telechelic polyisoprenes prepared by DEAB initiated free radical polymerization followed by LiAlH4 reduction of the end groups.

Polymer-Based Black Phosphorus (bP) Hybrid Materials by in Situ Radical Polymerization: An Effective Tool To Exfoliate bP and Stabilize bP Nanoflakes

PubMed Central

2018-01-01

Black phosphorus (bP) has been recently investigated for next generation nanoelectronic multifunctional devices. However, the intrinsic instability of exfoliated bP (the bP nanoflakes) toward both moisture and air has so far overshadowed its practical implementation. In order to contribute to fill this gap, we report here the preparation of new hybrid polymer-based materials where bP nanoflakes (bPn) exhibit a significantly improved stability. The new materials have been prepared by different synthetic paths including: (i) the mixing of conventionally liquid-phase exfoliated bP (in dimethyl sulfoxide, DMSO) with poly(methyl methacrylate) (PMMA) solution; (ii) the direct exfoliation of bP in a polymeric solution; (iii) the in situ radical polymerization after exfoliating bP in the liquid monomer (methyl methacrylate, MMA). This last methodology concerns the preparation of stable suspensions of bPn–MMA by sonication-assisted liquid-phase exfoliation (LPE) of bP in the presence of MMA followed by radical polymerization. The hybrids characteristics have been compared in order to evaluate the bP dispersion and the effectiveness of the bPn interfacial interactions with polymer chains aimed at their long-term environmental stabilization. The passivation of the bPn is particularly effective when the hybrid material is prepared by in situ polymerization. By using this synthetic methodology, the nanoflakes, even if with a gradient of dispersion (size of aggregates), preserve their chemical structure from oxidation (as proved by both Raman and 31P-solid state NMR studies) and are particularly stable to air and UV light exposure. The feasibility of this approach, capable of efficiently exfoliating bP while protecting the bPn, has been then verified by using different vinyl monomers (styrene and N-vinylpyrrolidone), thus obtaining hybrids where the nanoflakes are embedded in polymer matrices with a variety of intriguing thermal, mechanical, and solubility characteristics.

Combinatorial and high-throughput approaches in polymer science

NASA Astrophysics Data System (ADS)

Zhang, Huiqi; Hoogenboom, Richard; Meier, Michael A. R.; Schubert, Ulrich S.

2005-01-01

Combinatorial and high-throughput approaches have become topics of great interest in the last decade due to their potential ability to significantly increase research productivity. Recent years have witnessed a rapid extension of these approaches in many areas of the discovery of new materials including pharmaceuticals, inorganic materials, catalysts and polymers. This paper mainly highlights our progress in polymer research by using an automated parallel synthesizer, microwave synthesizer and ink-jet printer. The equipment and methodologies in our experiments, the high-throughput experimentation of different polymerizations (such as atom transfer radical polymerization, cationic ring-opening polymerization and emulsion polymerization) and the automated matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS) sample preparation are described.

Removal of Pb(II) from aqueous solutions using waste textiles/poly(acrylic acid) composite synthesized by radical polymerization technique.

PubMed

Zhou, Tao; Xia, Fafa; Deng, Yue; Zhao, Youcai

2018-05-01

Waste textiles (WTs) are the inevitable outcome of human activity and should be separated and recycled in view of sustainable development. In this work, WT was modified through grafting with acrylic acid (AA) via radical polymerization process using ceric ammonium nitrate (CAN) as an initiator and microwave and/or UV irradiation as energy supply. The acrylic acid-grafted waste textiles (WT-g-AA) thus obtained was then used as an adsorbent to remove Pb(II) from Pb(II)-containing wastewater. The effects of pH, initial concentrations of Pb(II) and adsorbent dose were investigated, and around 95% Pb(II) can be removed from the aqueous solution containing 10mg/L at pH6.0-8.0. The experimental adsorption isotherm data was fitted to the Langmuir model with maximum adsorption capacity of 35.7mg Pb/g WT-g-AA. The Pb-absorbed WT-g-AA was stripped using dilute nitric acid solution and the adsorption capacity of Pb-free material decreased from 95.4% (cycle 1) to 91.1% (cycle 3). It was considered that the WT-g-AA adsorption for Pb(II) may be realized through the ion-exchange mechanism between COOH and Pb(II). The promising results manifested that WT-g-AA powder was an efficient, eco-friendly and reusable adsorbent for the removal of Pb(II) from wastewater. Copyright © 2017. Published by Elsevier B.V.

Synthesis of Resveratrol Tetramers via a Stereoconvergent Radical Equilibrium

PubMed Central

Keylor, Mitchell H.; Matsuura, Bryan S.; Griesser, Markus; Chauvin, Jean-Philippe R.; Harding, Ryan A.; Kirillova, Mariia S.; Zhu, Xu; Fischer, Oliver J.; Pratt, Derek A.; Stephenson, Corey R. J.

2017-01-01

Persistent free radicals have become indispensable in the synthesis of organic materials by living radical polymerization. However, examples of their use in the synthesis of small molecules are rare. Herein, we report the application of persistent radical and quinone methide intermediates to the synthesis of the resveratrol tetramers nepalensinol B and vateriaphenol C. The spontaneous cleavage and reconstitution of exceptionally weak carbon-carbon bonds has enabled a stereoconvergent oxidative dimerization of racemic materials in a transformation that likely coincides with the biogenesis of these natural products. The efficient synthesis of higher-order oligomers of resveratrol will facilitate the biological studies necessary to elucidate their mechanism(s) of action. PMID:27940867

Swelling-induced optical anisotropy of thermoresponsive hydrogels based on poly(2-(2-methoxyethoxy)ethyl methacrylate): deswelling kinetics probed by quantitative Mueller matrix polarimetry.

PubMed

Patil, Nagaraj; Soni, Jalpa; Ghosh, Nirmalya; De, Priyadarsi

2012-11-29

Thermodynamically favored polymer-water interactions below the lower critical solution temperature (LCST) caused swelling-induced optical anisotropy (linear retardance) of thermoresponsive hydrogels based on poly(2-(2-methoxyethoxy)ethyl methacrylate). This was exploited to study the macroscopic deswelling kinetics quantitatively by a generalized polarimetry analysis method, based on measurement of the Mueller matrix and its subsequent inverse analysis via the polar decomposition approach. The derived medium polarization parameters, namely, linear retardance (δ), diattenuation (d), and depolarization coefficient (Δ), of the hydrogels showed interesting differences between the gels prepared by conventional free radical polymerization (FRP) and reversible addition-fragmentation chain transfer polymerization (RAFT) and also between dry and swollen state. The effect of temperature, cross-linking density, and polymerization technique employed to synthesize hydrogel on deswelling kinetics was systematically studied via conventional gravimetry and corroborated further with the corresponding Mueller matrix derived quantitative polarimetry characteristics (δ, d, and Δ). The RAFT gels exhibited higher swelling ratio and swelling-induced optical anisotropy compared to FRP gels and also deswelled faster at 30 °C. On the contrary, at 45 °C, deswelling was significantly retarded for the RAFT gels due to formation of a skin layer, which was confirmed and quantified via the enhanced diattenuation and depolarization parameters.

A Visible Light Initiating System for Free Radical Promoted Cationic Polymerization

DTIC Science & Technology

1994-02-02

identify the end groups in the polymer of cyclohexene oxide. N,N-Dimethylnaphthyl amine (DNA), a compound with high fluorescence quantum yield, was used...candidates to be polymerized via a cationic mechanism include cyclic ethers, cyclic formals and acetals, vinyl ethers, and epoxy compounds . Of these...reported sensitizer, bears two dimethylamino groups, is direct evidence that an aromatic amine can be present in a cationically photopolymerizable system

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

Recent Developments in the Synthesis of Biomacromolecules and their Conjugates by Single Electron Transfer-Living Radical Polymerization.

PubMed

Lligadas, Gerard; Grama, Silvia; Percec, Virgil

2017-04-10

Single electron transfer-living radical polymerization (SET-LRP) represents a robust and versatile tool for the synthesis of vinyl polymers with well-defined topology and chain end functionality. The crucial step in SET-LRP is the disproportionation of the Cu(I)X generated by activation with Cu(0) wire, powder, or nascent Cu(0) generated in situ into nascent, extremely reactive Cu(0) atoms and nanoparticles and Cu(II)X 2 . Nascent Cu(0) activates the initiator and dormant chains via a homogeneous or heterogeneous outer-sphere single-electron transfer mechanism (SET-LRP). SET-LRP provides an ultrafast polymerization of a plethora of monomers (e.g., (meth)-acrylates, (meth)-acrylamides, styrene, and vinyl chloride) including hydrophobic and water insoluble to hydrophilic and water soluble. Some advantageous features of SET-LRP are (i) the use of Cu(0) wire or powder as readily available catalysts under mild reaction conditions, (ii) their excellent control over molecular weight evolution and distribution as well as polymer chain ends, (iii) their high functional group tolerance allowing the polymerization of commercial-grade monomers, and (iv) the limited purification required for the resulting polymers. In this Perspective, we highlight the recent advancements of SET-LRP in the synthesis of biomacromolecules and of their conjugates.

A new approach to network heterogeneity: Polymerization Induced Phase Separation in photo-initiated, free-radical methacrylic systems

PubMed Central

Szczepanski, Caroline R.; Pfeifer, Carmem S.; Stansbury, Jeffrey W.

2012-01-01

Non-reactive, thermoplastic prepolymers (poly- methyl, ethyl and butyl methacrylate) were added to a model homopolymer matrix composed of triethylene glycol dimethacrylate (TEGDMA) to form heterogeneous networks via polymerization induced phase separation (PIPS). PIPS creates networks with distinct phase structure that can partially compensate for volumetric shrinkage during polymerization through localized internal volume expansion. This investigation utilizes purely photo-initiated, free-radical systems, broadening the scope of applications for PIPS since these processing conditions have not been studied previously. The introduction of prepolymer into TEGDMA monomer resulted in stable, homogeneous monomer formulations, most of which underwent PIPS upon photo-irradiation, creating heterogeneous networks. During polymerization the presence of prepolymer enhanced autoacceleration, allowing for a more extensive ambient cure of the material. Phase separation, as characterized by dynamic changes in sample turbidity, was monitored simultaneously with monomer conversion and either preceded or was coincident with network gelation. Dynamic mechanical analysis shows a broadening of the tan delta peak and secondary peak formation, characteristic of phase-separated materials, indicating one phase rich in prepolymer and another depleted form upon phase separation. In certain cases, PIPS leads to an enhanced physical reduction of volumetric shrinkage, which is attractive for many applications including dental composite materials. PMID:23109733

Organocatalyzed Photocontrolled Radical Polymerization of Semifluorinated (Meth)acrylates Driven by Visible Light.

PubMed

Gong, Honghong; Zhao, Yucheng; Shen, Xianwang; Lin, Jun; Chen, Mao

2018-01-02

Fluorinated polymers are important materials that are widely used in many areas. Herein, we report the development of a metal-free photocontrolled radical polymerization of semifluorinated (meth)acrylates with a new visible-light-absorbing organocatalyst. This method enabled the production of a variety of semifluorinated polymers with narrow molar-weight distributions from semifluorinated trithiocarbonates or perfluoroalkyl iodides. The high performance of "ON/OFF" control and chain-extension experiments further demonstrate the utility and reliability of this method. Furthermore, to streamline the preparation of semifluorinated polymers, a scalable continuous-flow approach has been developed. Given the broad interest in fluorinated materials and photopolymerization, we expect that this method will facilitate the development of advanced materials with unique properties. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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).

The influence of the quantum dot/polymethylmethacrylate composite preparation method on the stability of its optical properties under laser radiation

NASA Astrophysics Data System (ADS)

Zvaigzne, M. A.; Martynov, I. L.; Krivenkov, V. A.; Samokhvalov, P. S.; Nabiev, I. R.

2017-01-01

Photoluminescent semiconductor nanocrystals, quantum dots (QDs), are nowadays one of the most promising materials for developing a new generation of fluorescent labels, new types of light-emitting devices and displays, flexible electronic components, and solar panels. In many areas the use of QDs is associated with an intense optical excitation, which, in the case of a prolonged exposure, often leads to changes in their optical characteristics. In the present work we examined how the method of preparation of quantum dot/polymethylmethacrylate (QD/PMMA) composite influenced the stability of the optical properties of QD inside the polymer matrix under irradiation by different laser harmonics in the UV (355 nm) and visible (532 nm) spectral regions. The composites were synthesized by spin-coating and radical polymerization methods. Experiments with the samples obtained by spin-coating showed that the properties of the QD/PMMA films remain almost constant at values of the radiation dose below 10 fJ per particle. Irradiating the composites prepared by the radical polymerization method, we observed a monotonic increase in the luminescence quantum yield (QY) accompanied by an increase in the luminescence decay time regardless of the wavelength of the incident radiation. We assume that the observed difference in the optical properties of the samples under exposure to laser radiation is associated with the processes occurring during radical polymerization, in particular, with charge transfer from the radical particles inside QDs. The results of this study are important for understanding photophysical properties of composites on the basis of QDs, as well as for selection of the type of polymer and the composite synthesis method with quantum dots that would allow one to avoid the degradation of their luminescence.

Purification of inkjet ink from water using liquid phase, electric discharge polymerization and cellulosic membrane filtration.

PubMed

Jordan, Alexander T; Hsieh, Jeffery S; Lee, Daniel T

2013-01-01

A method to separate inkjet ink from water was developed using a liquid phase, electric discharge process. The liquid phase, electric discharge process with filtration or sedimentation was shown to remove 97% of inkjet ink from solutions containing between 0.1-0.8 g/L and was consistent over a range of treatment conditions. Additionally, particle size analysis of treated allyl alcohol and treated propanol confirmed the electric discharge treatment has a polymerization mechanism, and small molecule analysis of treated methanol using gas chromatography and mass spectroscopy confirmed the mechanism was free radical initiated polymerization.

Characterization of Phenolic Compounds in Wine Lees

PubMed Central

Zhijing, Ye; Shavandi, Amin; Harrison, Roland; Bekhit, Alaa El-Din A.

2018-01-01

The effect of vinification techniques on phenolic compounds and antioxidant activity of wine lees are poorly understood. The present study investigated the antioxidant activity of white and red wine lees generated at early fermentation and during aging. In this study, the total phenol content (TPC), total tannin content (TTC), mean degree of polymerization (mDP), and antioxidant activities of five white and eight red wine lees samples from different vinification backgrounds were determined. The results showed that vinification techniques had a significant (p < 0.05) impact on total phenol and tannin content of the samples. White wine lees had high mDP content compared with red ones. Catechin (50–62%) and epicatechin contents were the predominant terminal units of polymeric proanthocyanidin extracted from examined samples. Epigallocatechin was the predominant extension unit of white wine lees, whereas epicatechin was the predominant compound in red wine marc. The ORAC (oxygen radical absorbance capacity) assay was strongly correlated with the DPPH (α,α-diphenyl-β-picrylhydrazyl) assay, and the results showed the strong antioxidant activities associated with red wine lees (PN > 35 mg Trolox/g FDM) (PN: Pinot noir lees; FDM: Freeze-dried Material). This study indicates that tannin is one of the major phenolic compounds available in wine lees that can be useful in human and animal health applications. PMID:29587406

Characterization of Phenolic Compounds in Wine Lees.

PubMed

Zhijing, Ye; Shavandi, Amin; Harrison, Roland; Bekhit, Alaa El-Din A

2018-03-25

The effect of vinification techniques on phenolic compounds and antioxidant activity of wine lees are poorly understood. The present study investigated the antioxidant activity of white and red wine lees generated at early fermentation and during aging. In this study, the total phenol content (TPC), total tannin content (TTC), mean degree of polymerization (mDP), and antioxidant activities of five white and eight red wine lees samples from different vinification backgrounds were determined. The results showed that vinification techniques had a significant ( p < 0.05) impact on total phenol and tannin content of the samples. White wine lees had high mDP content compared with red ones. Catechin (50-62%) and epicatechin contents were the predominant terminal units of polymeric proanthocyanidin extracted from examined samples. Epigallocatechin was the predominant extension unit of white wine lees, whereas epicatechin was the predominant compound in red wine marc. The ORAC (oxygen radical absorbance capacity) assay was strongly correlated with the DPPH (α, α-diphenyl-β-picrylhydrazyl) assay, and the results showed the strong antioxidant activities associated with red wine lees (PN > 35 mg Trolox/g FDM) (PN: Pinot noir lees; FDM: Freeze-dried Material). This study indicates that tannin is one of the major phenolic compounds available in wine lees that can be useful in human and animal health applications.

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.

Recyclable crosslinked polymer networks with full property recovery made via one-step controlled radical polymerization

NASA Astrophysics Data System (ADS)

Jin, Kailong; Li, Lingqiao; Torkelson, John

Rubber tires illustrate well the issues ranging from economic loss to environmental problems and sustainability issues that arise with spent, covalently crosslinked polymers. A nitroxide-mediated polymerization (NMP) strategy has been developed that allows for one-step synthesis of recyclable crosslinked polymers from monomers or polymers that contain carbon-carbon double bonds amenable to radical polymerization. Resulting materials possess dynamic alkoxyamine crosslinks that undergo reversible decrosslinking as a function of temperature. Using polybutadiene as starting material, and styrene, an appropriate nitroxide molecule and bifunctional initiator for initial crosslinking, a model for tire rubber can be produced by reaction at temperatures comparable to those employed in tire molding. Upon cooling, the crosslinks are made permanent due to the extraordinarily strong temperature dependence of the reverisible nitroxide capping and uncapping reaction. Based on thermomechanical property characterization, when the original crosslinked model rubber is chopped into bits and remolded in the melt state, a well-consolidated material is obtained which exhibits full recovery of properties reflecting crosslink density after multiple recycling steps.

A novel solid state photocatalyst for living radical polymerization under UV irradiation

NASA Astrophysics Data System (ADS)

Fu, Qiang; McKenzie, Thomas G.; Ren, Jing M.; Tan, Shereen; Nam, Eunhyung; Qiao, Greg G.

2016-02-01

This study presents the development of a novel solid state photocatalyst for the photoinduced controlled radical polymerization of methacrylates under mild UV irradiation (λmax ≈ 365 nm) in the absence of conventional photoinitiators, metal-catalysts or dye sensitizers. The photocatalyst design was based on our previous finding that organic amines can act in a synergistic photochemical reaction with thiocarbonylthio compounds to afford well controlled polymethacrylates under UV irradiation. Therefore, in the current contribution an amine-rich polymer was covalently grafted onto a solid substrate, thus creating a heterogeneous catalyst that would allow for facile removal, recovery and recyclability when employed for such photopolymerization reactions. Importantly, the polymethacrylates synthesized using the solid state photocatalyst (ssPC) show similarly excellent chemical and structural integrity as those catalysed by free amines. Moreover, the ssPC could be readily recovered and re-used, with multiple cycles of polymerization showing minimal effect on the integrity of the catalyst. Finally, the ssPC was employed in various photo-“click” reactions, permitting high yielding conjugations under photochemical control.

Metal-Free Atom Transfer Radical Polymerization of Methyl Methacrylate with ppm Level of Organic Photocatalyst.

PubMed

Huang, Zhicheng; Gu, Yu; Liu, Xiaodong; Zhang, Lifen; Cheng, Zhenping; Zhu, Xiulin

2017-05-01

It is well known that the recently developed photoinduced metal-free atom transfer radical polymerization (ATRP) has been considered as a promising methodology to completely eliminate transition metal residue in polymers. However, a serious problem needs to be improved, namely, large amount of organic photocatalysts should be used to keep the controllability over molecular weights and molecular weight distributions. In this work, a novel photocatalyst 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) with strong excited state reduction potential is successfully used to mediate a metal-free ATRP of methyl methacrylate just with parts per million (ppm) level usage under irradiation of blue light emitting diode at room temperature, using ethyl α-bromophenyl-acetate as a typical initiator with high initiator efficiency. The polymerization kinetic study, multiple controlled "on-off" light switching cycle regulation, and chain extension experiment confirm the "living"/controlled features of this promising photoinduced metal-free ATRP system with good molecular weight control in the presence of ppm level photocatalyst 4CzIPN. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

Acrylate intercalation and in situ polymerization in iron-, cobalt-, or manganese-substituted nickel hydroxides.

PubMed

Vaysse, C; Guerlou-Demourgues, L; Duguet, E; Delmas, C

2003-07-28

A chimie douce route based on successive redox and exchange reactions has allowed us to prepare new hybrid organic-inorganic materials, composed of polyacrylate macromolecules intercalated into layered double hydroxides (LDHs), deriving from Ni(OH)(2). Monomer intercalation and in situ polymerization mechanisms have appeared to be strongly dependent upon the nature of the substituting cation in the slabs. In the case of iron-based LDHs, a phase containing acrylate monomeric intercalates has been isolated and identified by X-ray diffraction and infrared spectroscopy. Second, interslab free-radical polymerization of acrylate anions has been successfully initiated using potassium persulfate. In cobalt- or manganese-based LDHs, one-step polymerization has been observed, leading directly to a material containing polyacrylate intercalate.

Interference lithography for optical devices and coatings

NASA Astrophysics Data System (ADS)

Juhl, Abigail Therese

Interference lithography can create large-area, defect-free nanostructures with unique optical properties. In this thesis, interference lithography will be utilized to create photonic crystals for functional devices or coatings. For instance, typical lithographic processing techniques were used to create 1, 2 and 3 dimensional photonic crystals in SU8 photoresist. These structures were in-filled with birefringent liquid crystal to make active devices, and the orientation of the liquid crystal directors within the SU8 matrix was studied. Most of this thesis will be focused on utilizing polymerization induced phase separation as a single-step method for fabrication by interference lithography. For example, layered polymer/nanoparticle composites have been created through the one-step two-beam interference lithographic exposure of a dispersion of 25 and 50 nm silica particles within a photopolymerizable mixture at a wavelength of 532 nm. In the areas of constructive interference, the monomer begins to polymerize via a free-radical process and concurrently the nanoparticles move into the regions of destructive interference. The holographic exposure of the particles within the monomer resin offers a single-step method to anisotropically structure the nanoconstituents within a composite. A one-step holographic exposure was also used to fabricate self-healing coatings that use water from the environment to catalyze polymerization. Polymerization induced phase separation was used to sequester an isocyanate monomer within an acrylate matrix. Due to the periodic modulation of the index of refraction between the monomer and polymer, the coating can reflect a desired wavelength, allowing for tunable coloration. When the coating is scratched, polymerization of the liquid isocyanate is catalyzed by moisture in air; if the indices of the two polymers are matched, the coatings turn transparent after healing. Interference lithography offers a method of creating multifunctional self-healing coatings that readout when damage has occurred.

Biocompatibility of 4-META/MMA-TBB resin used as a dental luting agent.

PubMed

Nakagawa, Kaori; Saita, Makiko; Ikeda, Takayuki; Hirota, Makoto; Park, Wonhee; Lee, Masaichi Chang-Il; Ogawa, Takahiro

2015-07-01

The bonding and biological properties of currently used luting/cementing materials need to be improved. 4-Acryloyloxyethyl trimellitate anhydride/methyl methacrylate-tri-n-butylborane (4-META/MMA-TBB) resin is primarily used for splinting mobile teeth or treating fractured teeth. It undergoes moisture-resistant polymerization and bonds strongly to dentin and metals. The purpose of this in vitro study was to compare the biological and biochemical properties META/MMA-TBB resin with those of conventional polymethyl methacrylate (PMMA)-MMA resin and other currently used luting materials in order to determine whether it may be a viable dental luting agent. The degree of polymerization of 4-META/MMA-TBB resin, PMMA-MMA autopolymerizing resin, 10-methacryloyloxydecyl dihydrogen phosphate-dimethacrylate (MDP-DMA) adhesive resin, and a glass ionomer cement was measured by Fourier-transformed infrared spectroscopy. Free radical production during setting was evaluated by electron spin resonance (ESR) spectroscopy. Rat dental pulp cells cultured on these materials were examined for cell viability, attachment, proliferation, and functional phenotype. The degree of polymerization of 4-META/MMA-TBB resin was 82% thirty minutes after preparation, compared to 66% for PMMA-MMA autopolymerizing resin. ESR spectroscopy revealed free radical production from 4-META/MMA-TBB resin and glass ionomer cement was equivalent 24 hours after preparation, with no spike in radical generation observed. In contrast, free radical production from PMMA-MMA and MDP-DMA adhesive resins was rapid and sustained and 10 to 20 times greater than that from 4-META/MMA-TBB. The percentage of viable dental pulp cells 24 hours after seeding was considerably higher on MDP-DMA and 4-META/MMA-TBB resin than on glass ionomer cement. Cell number, proliferation, and alkaline phosphatase activity were highest on 4-META/MMA-TBB resin and lowest on the glass ionomer cement. 4-META/MMA-TBB resin is at least as biocompatible, and perhaps even more biocompatible, than other current luting materials, with fast, favorable, and nontoxic polymerization properties. Further in vivo and human studies of 4-META/MMA-TBB resin as a dental luting agent are warranted. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

INHIBITING THE POLYMERIZATION OF NUCLEAR COOLANTS

DOEpatents

Colichman, E.L.

1959-10-20

>The formation of new reactor coolants which contain an additive tbat suppresses polymerization of the primary dissoclation free radical products of the pyrolytic and radiation decomposition of the organic coolants is described. The coolants consist of polyphenyls and condensed ring compounds having from two to about four carbon rings and from 0.1 to 5% of a powdered metal hydride chosen from the group consisting of the group IIA and IVA dispersed in the hydrocarbon.

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.

Encapsidated Atom-Transfer Radical Polymerization in Qβ Virus-like Nanoparticles

PubMed Central

2015-01-01

Virus-like particles (VLPs) are unique macromolecular structures that hold great promise in biomedical and biomaterial applications. The interior of the 30 nm-diameter Qβ VLP was functionalized by a three-step process: (1) hydrolytic removal of endogenously packaged RNA, (2) covalent attachment of initiator molecules to unnatural amino acid residues located on the interior capsid surface, and (3) atom-transfer radical polymerization of tertiary amine-bearing methacrylate monomers. The resulting polymer-containing particles were moderately expanded in size; however, biotin-derivatized polymer strands were only very weakly accessible to avidin, suggesting that most of the polymer was confined within the protein shell. The polymer-containing particles were also found to exhibit physical and chemical properties characteristic of positively charged nanostructures, including the ability to easily enter mammalian cells and deliver functional small interfering RNA. PMID:25073013

Processable high-carbon-yielding polymer for micro- and nanofabrication

NASA Astrophysics Data System (ADS)

Perpall, Mark W.; Zengin, Huseyin; Perera, K. Prasanna U.; Zhou, Wensheng; Shah, Hiren; Wu, Xinyu; Creager, Stephen E.; Smith, Dennis W., Jr.; Foulger, Stephen H.; Ballato, John M.

2003-01-01

Bis-ortho-Diynyl Arene (BODA) monomers polymerize to network polynapthalene by the thermally-driven Bergman cyclization and subsequent radical polymerization via oligomeric intermediates that can be melt or solution processed. Further heating of the network to 1000 °C affords a high-yield glassy carbon structure that retains the approximate size and dimensions of the polymer precursor. The higher carbon-yield for BODA networks (75- 80 % by mass) is significantly greater than that of traditional phenol-formaldehyde resins and other carbon precursor polymers leading to its greater dimensional stability. Phenyl terminated BODA derived polymers were fabricated using microprocessing such as the micromolding in capillaries (MIMIC) technique, direct microtransfer molding, and molding in quartz capillary tubes. Nano-scale fabrication using closed packed silica spheres as templates was demonstrated with an hydroxy-terminated monomer which exhibits greatly enhanced compatibility for silica surfaces. After pyrolysis to glassy carbon, the silica is chemically etched leaving an inverse carbon opal photonic crystal which is electrically conductive. The wavelength of light diffracted is a function of the average refractive index of the carbon/ filler composite, which can be modified for use as sensitive detector elements.

Structural, optical and photo thermal properties of Er3+:Y2O3 doped PMMA nanocomposite

NASA Astrophysics Data System (ADS)

Tabanli, Sevcan; Eryurek, Gonul

2018-02-01

Thermal decomposition technique was employed to synthesize of phosphors of yttria (Y2O3) doped with erbium (Er3+) ions. After the synthesized procedure, the nano-sized crystalline powders were annealed at 800oC for 24 h. Annealed powders were embedded in poly(methyl methacrylate) (PMMA) by free radical polymerization to fabricate nanocomposite polymer materials. The crystalline structure of the powder and doped PMMA nanocomposite samples were determined using X-ray diffraction technique. Scherrer's equation and the FW1/5/4/5M method were used to determine average crystalline size and grain size distributions, respectively. The spectroscopic properties of the powders and doped PMMA nanocomposites were studied by measuring the upconversion emission spectra under near-infrared laser excitation at room temperature. The laser-induced photo thermal behaviors of Er3+:Y2O3 nano-powders and doped PMMA nanocomposite were investigated using the fluorescence intensity ratio (FIR) technique.

Controlled release of mitomycin C from PHEMAH-Cu(II) cryogel membranes.

PubMed

Bakhshpour, Monireh; Yavuz, Handan; Denizli, Adil

2018-02-19

Molecular imprinting technique was used for the preparation of antibiotic and anti-neoplastic chemotherapy drug (mitomycin C) imprinted cryogel membranes (MMC-ICM). The membranes were synthezied by using metal ion coordination interactions with N-methacryloyl-(l)-histidine methyl ester (MAH) functional monomer and template molecules (i.e. MMC). The 2-hydroxyethyl methacrylate (HEMA) monomer and methylene bisacrylamide (MBAAm) crosslinker were used for the preparation of mitomycin C imprinted cryogel membranes by radical suspension polymerization technique. The imprinted cryogel membranes were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and swelling degree measurements. Cytotoxicity of MMC-ICMs was investigated using mouse fibroblast cell line L929. Time-dependent release of MMC was demonstrated within 150 h from cryogel membranes. Cryogels demonstrated very high MMC loading efficiency (70-80%) and sustained MMC release over hours.

End-Functionalized Palladium SCS Pincer Polymers via Controlled Radical Polymerizations.

PubMed

Lye, Diane S; Cohen, Aaron E; Wong, Madeleine Z; Weck, Marcus

2017-07-01

A direct and facile route toward semitelechelic polymers, end-functionalized with palladated sulfur-carbon-sulfur pincer (Pd II -pincer) complexes is reported that avoids any post-polymerization step. Key to our methodology is the combination of reversible addition-fragmentation chain-transfer (RAFT) polymerization with functionalized chain-transfer agents. This strategy yields Pd end-group-functionalized materials with monomodal molar mass dispersities (Đ) of 1.18-1.44. The RAFT polymerization is investigated using a Pd II -pincer chain-transfer agent for three classes of monomers: styrene, tert-butyl acrylate, and N-isopropylacrylamide. The ensuing Pd II -pincer end-functionalized polymers are analyzed using 1 H NMR spectroscopy, gel-permeation chromatography, and elemental analysis. The RAFT polymerization methodology provides a direct pathway for the fabrication of Pd II -pincer functionalized polymers with complete end-group functionalization. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Effect of techniques of composite resin insertion and polymerization on microleakage and microhardness].

PubMed

Amaral, Cristiane Mariote; Castro, Ana Karina Barbieri Bedran de; Pimenta, Luiz André Freire; Ambrosano, Glaucia Maria Boni

2002-01-01

The aim of this study was to evaluate the influence of techniques of composite resin polymerization and insertion on microleakage and microhardness. One hundred and eighty class II cavities were prepared in bovine teeth and assigned to six groups: G1 - bulk filling + conventional polymerization; G2 - bucco-lingual increments + conventional polymerization; G3 - bulk filling + soft-start polymerization; G4 - bucco-lingual increments + soft-start polymerization; G5 - bulk filling + progressive polymerization; G6 - bucco-lingual increments + progressive polymerization. All cavities were restored with the Z100/Single Bond system (3M). After thermocycling, the samples were immersed in 2% methylene blue dye solution for 4 hours. Half of the samples were embedded in polystyrene resin, and Knoop microhardness was measured. The Kruskal-Wallis test did not reveal statistical differences (p > 0.05) between the polymerization and insertion techniques as to microleakage. Regarding microhardness, the two-way ANOVA and the Tukey test did not reveal statistical differences between the restorative techniques (p > 0.05), but progressive polymerization (G5 and G6) was associated with smaller Knoop microhardness values (p < 0.05): G = 144.11; G2 = 143.89; G3 = 141.14; G4 = 142.79; G5 = 132.15; G6 = 131.67. It was concluded that the evaluated polymerization and insertion techniques did not affect marginal microleakage, but a decrease in microhardness occurred when progressive polymerization was carried out.

Controlled Radical Polymerization as an Enabling Approach for the Next Generation of Protein-Polymer Conjugates.

PubMed

Pelegri-O'Day, Emma M; Maynard, Heather D

2016-09-20

Protein-polymer conjugates are unique constructs that combine the chemical properties of a synthetic polymer chain with the biological properties of a biomacromolecule. This often leads to improved stabilities, solubilities, and in vivo half-lives of the resulting conjugates, and expands the range of applications for the proteins. However, early chemical methods for protein-polymer conjugation often required multiple polymer modifications, which were tedious and low yielding. To solve these issues, work in our laboratory has focused on the development of controlled radical polymerization (CRP) techniques to improve synthesis of protein-polymer conjugates. Initial efforts focused on the one-step syntheses of protein-reactive polymers through the use of functionalized initiators and chain transfer agents. A variety of functional groups such as maleimide and pyridyl disulfide could be installed with high end-group retention, which could then react with protein functional groups through mild and biocompatible chemistries. While this grafting to method represented a significant advance in conjugation technique, purification and steric hindrance between large biomacromolecules and polymer chains often led to low conjugation yields. Therefore, a grafting from approach was developed, wherein a polymer chain is grown from an initiating site on a functionalized protein. These conjugates have demonstrated improved homogeneity, characterization, and easier purification, while maintaining protein activity. Much of this early work utilizing CRP techniques focused on polymers made up of biocompatible but nonfunctional monomer units, often containing oligoethylene glycol meth(acrylate) or N-isopropylacrylamide. These branched polymers have significant advantages compared to the historically used linear poly(ethylene glycols) including decreased viscosities and thermally responsive behavior, respectively. Recently, we were motivated to use CRP techniques to develop polymers with rationally designed and functional biological properties for conjugate preparation. Specifically, two families of saccharide-inspired polymers were developed for stabilization and activation of therapeutic biomolecules. A series of polymers with trehalose side-chains and vinyl backbones were prepared and used to stabilize proteins against heat and lyophilization stress as both conjugates and additives. These materials, which combine properties of osmolytes with nonionic surfactants, have significant potential for in vivo therapeutic use. Additionally, polymers that mimic the structure of the naturally occurring polysaccharide heparin were prepared. These polymers contained negatively charged sulfonate groups and imparted stabilization to a heparin-binding growth factor after conjugation. A screen of other sulfonated polymers led to the development of a polymer with improved heparin mimesis, enhancing both stability and activity of the protein to which it was attached. Chemical improvements over the past decade have enabled the preparation of a diverse set of protein-polymer conjugates by controlled polymerization techniques. Now, the field should thoroughly explore and expand both the range of polymer structures and also the applications available to protein-polymer conjugates. As we move beyond medicine toward broader applications, increased collaboration and interdisciplinary work will result in the further development of this exciting field.

A Hybrid Nanomaterial for the Controlled Generation of Free Radicals and Oxidative Destruction of Hypoxic Cancer Cells.

PubMed

Shen, Song; Zhu, Chunlei; Huo, Da; Yang, Miaoxin; Xue, Jiajia; Xia, Younan

2017-07-17

Anticancer modalities based on oxygen free radicals, including photodynamic therapy and radiotherapy, have emerged as promising treatments in the clinic. However, the hypoxic environment in tumor tissue prevents the formation of oxygen free radicals. Here we introduce a novel strategy that employs oxygen-independent free radicals generated from a polymerization initiator for eradicating cancer cells. The initiator is mixed with a phase-change material and loaded into the cavities of gold nanocages. Upon irradiation by a near-infrared laser, the phase-change material is melted due to the photothermal effect of gold nanocages, leading to the release and decomposition of the loaded initiator to generate free radicals. The free radicals produced in this way are highly effective in inducing apoptosis in hypoxic cancer cells. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Assessment of novel maleic anhydride copolymers prepared via nitroxide-mediated radical polymerization as CaSO4 crystal growth inhibitors.

PubMed

Al-Roomi, Yousef Mohammad; Hussain, Kaneez Fatema

2017-04-01

Calcium sulfate is one of the dominant scales which, unlike carbonate scale, are not easily removable by acid. To inhibit CaSO 4 scale formation in artificial cooling water systems, well-defined low molecular weight maleic anhydride and n-alkylacrylamide copolymers (YMR-S series) were synthesized via nitroxide-mediated radical polymerization initiated by benzoyl peroxide in the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy at varying concentrations. These polymerizations exhibit living polymerization characteristics; that is, they show linear growth in chain length as a function of monomer conversion, and have narrow molecular weight distributions. Resultant polymers were characterized by means of 1 H-NMR and 13 C-NMR. The inhibition behavior of these YMR-S series polymers against CaSO 4 was evaluated using the static scale inhibition method and a dynamic tube block test. The inhibition ability on the CaSO 4 scale is 99.5% with 9 ppm dosage level at pH 10.45 and temperature 70°C. Scanning electronic microscope analysis proved the morphological changes of the CaSO 4 scales due to the strong inhibition action of YMR-S polymers. It is also observed that the antiscaling effect of the copolymers greatly depends on the molecular weight, and the optimum range is below 20,000 and approximately in the range 500-2000.

Preparation of magnetic molecularly imprinted polymers by atom transfer radical polymerization for the rapid extraction of avermectin from fish samples.

PubMed

You, Xiaoxiao; Gao, Lei; Qin, Dongli; Chen, Ligang

2017-01-01

A novel and highly efficient approach to obtain magnetic molecularly imprinted polymers is described to detect avermectin in fish samples. The magnetic molecularly imprinted polymers were synthesized by surface imprinting polymerization using magnetic multiwalled carbon nanotubes as the support materials, atom transfer radical polymerization as the polymerization method, avermectin as template, acrylamide as functional monomer, and ethylene glycol dimethacrylate as crosslinker. The characteristics of the magnetic molecularly imprinted polymers were assessed by using transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, vibrating sample magnetometry, X-ray diffraction, and thermogravimetric analysis. The binding characteristics of magnetic molecularly imprinted polymers were researched through isothermal adsorption experiment, kinetics adsorption experiment, and the selectivity experiment. Coupled with ultra high performance liquid chromatography and tandem mass spectrometry, the extraction conditions of the magnetic molecularly imprinted polymers as adsorbents for avermectin were investigated in detail. The recovery of avermectin was 84.2-97.0%, and the limit of detection was 0.075 μg/kg. Relative standard deviations of intra- and inter-day precisions were in the range of 1.7-2.9% and 3.4-5.6%, respectively. The results demonstrated that the extraction method not only has high selectivity and accuracy, but also is convenient for the determination of avermectin in fish samples. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nucleophilically assisted and cationic ring-opening polymerization of tin-bridged [1]ferrocenophanes.

PubMed

Baumgartner, Thomas; Jäkle, Frieder; Rulkens, Ron; Zech, Gernot; Lough, Alan J; Manners, Ian

2002-08-28

To obtain mechanistic insight, detailed studies of the intriguing "spontaneous" ambient temperature ring-opening polymerization (ROP) of tin-bridged [1]ferrocenophanes Fe(eta-C(5)H(4))(2)SnR(2) 3a (R = t-Bu) and 3b (R = Mes) in solution have been performed. The investigations explored the influence of non-nucleophilic additives such as radicals and radical traps, neutral and anionic nucleophiles, Lewis acids, protic species, and other cationic electrophiles. Significantly, two novel methodologies and mechanisms for the ROP of strained [1]ferrocenophanes are proposed based on this study. First, as the addition of amine nucleophiles such as pyridine was found to strongly accelerate the polymerization rate in solution, a new nucleophilicallyassisted ROP methodology was proposed. This operates at ambient temperature in solution even in the presence of chlorosilanes but, unlike the anionic polymerization of ferrocenophanes, does not involve cyclopentadienyl anions. Second, the addition of small quantities of the electrophilic species H(+) and Bu(3)Sn(+) was found to lead to a cationic ROP process. These studies suggest that the "spontaneous" ROP of tin-bridged [1]ferrocenophanes may be a consequence of the presence of spurious, trace quantities of Lewis basic or acidic impurities. The new ROP mechanisms reported are likely to be of general significance for the ROP of other metallocenophanes (e.g., for thermal ROP in the melt) and for other metallacycles containing group 14 elements.

UV-Vis/FT-NIR in situ monitoring of visible-light induced polymerization of PEGDA hydrogels initiated by eosin/triethanolamine/O2.

PubMed

Kaastrup, Kaja; Aguirre-Soto, Alan; Wang, Chen; Bowman, Christopher N; Stansbury, Jeffery; Sikes, Hadley D

In conjunction with a tertiary amine coinitiator, eosin, a photoreducible dye, has been shown to successfully circumvent oxygen inhibition in radical photopolymerization reactions. However, the role of O 2 in the initiation and polymerization processes remains inconclusive. Here, we employ a UV-Vis/FT-NIR analytical tool for real-time, simultaneous monitoring of chromophore and monomer reactive group concentrations to investigate the eosin-activated photopolymerization of PEGDA-based hydrogels under ambient conditions. First, we address the challenges associated with spectroscopic monitoring of the polymerization of hydrogels using UV-Vis and FT-NIR, proposing metrics for quantifying the extent of signal loss from reflection and scattering, and showing their relation to microgelation and network formation. Second, having established a method for extracting kinetic information by eliminating the effects of changing refractive index and scattering, the coupled UV-Vis/FT-NIR system is applied to the study of eosin-activated photopolymerization of PEGDA in the presence of O 2 . Analysis of the inhibition time, rate of polymerization, and rate of eosin consumption under ambient and purged conditions indicates that regeneration of eosin in the presence of oxygen and consumption of oxygen occur via a nonchain process. This suggests that the uniquely high O 2 resilience is due to alternative processes such as energy transfer from photo-activated eosin to oxygen. Uncovering the intricacies of the role of O 2 in eosin-mediated initiation aids the design of O 2 resistant free radical polymerization systems relevant to photonics, optoelectronics, biomaterials, and biosensing.

UV-Vis/FT-NIR in situ monitoring of visible-light induced polymerization of PEGDA hydrogels initiated by eosin/triethanolamine/O2

PubMed Central

Kaastrup, Kaja; Aguirre-Soto, Alan; Wang, Chen; Bowman, Christopher N.; Stansbury, Jeffery; Sikes, Hadley D.

2016-01-01

In conjunction with a tertiary amine coinitiator, eosin, a photoreducible dye, has been shown to successfully circumvent oxygen inhibition in radical photopolymerization reactions. However, the role of O2 in the initiation and polymerization processes remains inconclusive. Here, we employ a UV-Vis/FT-NIR analytical tool for real-time, simultaneous monitoring of chromophore and monomer reactive group concentrations to investigate the eosin-activated photopolymerization of PEGDA-based hydrogels under ambient conditions. First, we address the challenges associated with spectroscopic monitoring of the polymerization of hydrogels using UV-Vis and FT-NIR, proposing metrics for quantifying the extent of signal loss from reflection and scattering, and showing their relation to microgelation and network formation. Second, having established a method for extracting kinetic information by eliminating the effects of changing refractive index and scattering, the coupled UV-Vis/FT-NIR system is applied to the study of eosin-activated photopolymerization of PEGDA in the presence of O2. Analysis of the inhibition time, rate of polymerization, and rate of eosin consumption under ambient and purged conditions indicates that regeneration of eosin in the presence of oxygen and consumption of oxygen occur via a nonchain process. This suggests that the uniquely high O2 resilience is due to alternative processes such as energy transfer from photo-activated eosin to oxygen. Uncovering the intricacies of the role of O2 in eosin-mediated initiation aids the design of O2 resistant free radical polymerization systems relevant to photonics, optoelectronics, biomaterials, and biosensing. PMID:26755925

Characterization of γ-radiation induced polymerization in ethyl methacrylate and methyl acrylate monomers solutions

NASA Astrophysics Data System (ADS)

Baccaro, Stefania; Casieri, Cinzia; Cemmi, Alessia; Chiarini, Marco; D'Aiuto, Virginia; Tortora, Mariagrazia

2017-12-01

The present work is focused on the γ-radiation induced polymerization of ethyl methacrylate (EMA) and methyl acrylate (MA) monomers mixture to obtain a co-polymer with specific features. The effect of the irradiation parameters (radiation absorbed dose, dose rate) and of the environmental atmosphere on the features of the final products was investigated. Attenuated Total Reflectance - Fourier Transform Infrared Spectroscopy (ATR-FTIR) and Nuclear Magnetic Resonance high-resolution analyses of hydrogen and carbon nuclei (1H and 13C NMR) were applied to follow the γ-induced modifications by monitoring the co-polymerization process and allowed the irradiation parameters optimization. Diffusion-Ordered NMR (DOSY-NMR) data were used to evaluate the co-polymers polydispersity and polymerization degree. Since the last parameter is strongly influenced by the γ radiation and environmental conditions, a comparison among samples prepared and irradiated in air and under nitrogen atmosphere was carried out. In presence of oxygen, higher radiation was required to obtain a full solid co-polymer since a partial amount of energy released to the samples was involved in competitive processes, i.e. oxygen-containing free radicals formation and primary radicals recombination. Irrespectively to the environmental atmosphere, more homogeneous samples in term of polymerization degree dispersion was achieved at lower dose rates. At radiation absorbed doses higher than those needed for the formation of the co-polymer, while in case of samples irradiated in air heavy depolymerization was verified, a sensible increase of the samples stability was attained if the irradiation was performed under nitrogen atmosphere.

Polymeric peptide pigments with sequence-encoded properties

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

Lampel, Ayala; McPhee, Scott A.; Park, Hang-Ah

Melanins are a family of heterogeneous polymeric pigments that provide ultraviolet (UV) light protection, structural support, coloration, and free radical scavenging. Formed by oxidative oligomerization of catecholic small molecules, the physical properties of melanins are influenced by covalent and noncovalent disorder. We report the use of tyrosine-containing tripeptides as tunable precursors for polymeric pigments. In these structures, phenols are presented in a (supra-)molecular context dictated by the positions of the amino acids in the peptide sequence. Oxidative polymerization can be tuned in a sequence-dependent manner, resulting in peptide sequence–encoded properties such as UV absorbance, morphology, coloration, and electrochemical properties overmore » a considerable range. Short peptides have low barriers to application and can be easily scaled, suggesting near-term applications in cosmetics and biomedicine.« less

Glycosylated polyacrylate nanoparticles by emulsion polymerization

PubMed Central

Abeylath, Sampath C.; Turos, Edward

2007-01-01

A selection of glycosylated polyacrylate nanoparticles has been prepared by radical-initiated emulsion polymerization in aqueous media. Using ethyl acrylate as a co-monomer, carbohydrate acrylates were incorporated into the poly(ethyl acrylate) framework to give stable emulsions of glyconanoparticles with an average particle size of around 40 nm. Using this technique a variety of glyconanoparticles were prepared from 3-O-acryloyl-1,2:5,6-di-O-isopropylidene-α-D-glucofuranose, 1-O-acryloyl-2,3:5,6-di-O-isopropylidene-α-D-mannofuranose, 6-O-acryloyl-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose, 2-N-acryloyl-1,3,4,6-tetra-O-acetyl-β-D-glucosamine, 5-O-acryloyl-2,3-isopropylidene-1-methoxy-β-D-ribofuranose and 4-N-acetyl-5’-O-acryloyl-2’,3’-O-isopropylidene cytidine. Scanning electron microscopy, dynamic light scattering and proton NMR analysis of the emulsions indicated essentially 100% incorporation of the carbohydrate acrylate monomer into the polymer with the exception of O-benzyl- and O-benzoyl-protected carbohydrate acrylates, which gave incomplete incorporation. Formation of larger glyconanoparticles of ~80nm with (unprotected) 3-O-acryloyl-D-glucose and 5-O-acryloyl-1-methoxy-β-D-ribofuranose revealed the influence of free hydroxyl groups in the monomer on the particle size during polymerization, a feature which is also apparently dependent on the amount of carbohydrate in the matrix. This methodology allows for a new, simple route to the synthesis of polymeric glyconanoparticles with potential applications in targeted drug delivery and materials development. PMID:18677404

Ultra-high vacuum surface analysis study of rhodopsin incorporation into supported lipid bilayers.

PubMed

Michel, Roger; Subramaniam, Varuni; McArthur, Sally L; Bondurant, Bruce; D'Ambruoso, Gemma D; Hall, Henry K; Brown, Michael F; Ross, Eric E; Saavedra, S Scott; Castner, David G

2008-05-06

Planar supported lipid bilayers that are stable under ambient atmospheric and ultra-high-vacuum conditions were prepared by cross-linking polymerization of bis-sorbylphosphatidylcholine (bis-SorbPC). X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were employed to investigate bilayers that were cross-linked using either redox-initiated radical polymerization or ultraviolet photopolymerization. The redox method yields a more structurally intact bilayer; however, the UV method is more compatible with incorporation of transmembrane proteins. UV polymerization was therefore used to prepare cross-linked bilayers with incorporated bovine rhodopsin, a light-activated, G-protein-coupled receptor (GPCR). A previous study (Subramaniam, V.; Alves, I. D.; Salgado, G. F. J.; Lau, P. W.; Wysocki, R. J.; Salamon, Z.; Tollin, G.; Hruby, V. J.; Brown, M. F.; Saavedra, S. S. J. Am. Chem. Soc. 2005, 127, 5320-5321) showed that rhodopsin retains photoactivity after incorporation into UV-polymerized bis-SorbPC, but did not address how the protein is associated with the bilayer. In this study, we show that rhodopsin is retained in supported bilayers of poly(bis-SorbPC) under ultra-high-vacuum conditions, on the basis of the increase in the XPS nitrogen concentration and the presence of characteristic amino acid peaks in the ToF-SIMS data. Angle-resolved XPS data show that the protein is inserted into the bilayer, rather than adsorbed on the bilayer surface. This is the first study to demonstrate the use of ultra-high-vacuum techniques for structural studies of supported proteolipid bilayers.

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.

Effects of radical initiators, polymerization inhibitors, and other agents on the sonochemical unzipping of double-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Fukumori, Minoru; Hara, Shinnosuke; Ogawa, Takuji; Tanaka, Hirofumi

2018-03-01

The mechanism of graphene nanoribbon synthesis by the sonication-assisted unzipping of carbon nanotubes (CNTs) was investigated utilizing 4-methoxyphenol and 1,4-dimethoxybenzene as moieties of poly[(m-phenylenevinylene)-co-(2,5-dioctoxy-p-phenylenevinylene)]. The obtained results revealed that unzipping was promoted by 4-methoxyphenol owing to the facile abstraction of its phenolic hydrogen by sonication-generated radicals on CNTs, whereas 1,4-dimethoxybenzene did not facilitate unzipping, since its methoxy hydrogens were hardly abstracted. Moreover, unzipping was also facilitated by trans-stilbene, the double bond of which reacts with CNT radicals. Furthermore, we succeeded in using a general radical initiator, namely, 2,2‧-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride to promote unzipping, confirming that it is promoted by radical donors/trapping agents.

Polyimides and Process for Preparing Polyimides Having Thermal-Oxidative Stability

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B. (Inventor)

2001-01-01

Polyimides and the process for preparing polyimides having improved thermal-oxidative stability derived from the polymerization of effective amounts of one or more of the polyamines such as the aromatic diamines, one or more of the tetracarboxylic dianhydrides and a novel dicarboxylic endcap having formula with an R1 group of either hydrogen or an alkyl radical of one to four carbons, an R2 group of either OH, NH2, F, or Cl radical, an R3 group of either H, OH, NH2, F, Cl or an alkylene radical, an R4 group of either an alkyl, aryl, aryloxy, nitro, F, or Cl radical, and/or an R5 group of either H, alkyl, aryl, alkoxy, aryloxy, nitro, F, or Cl radical. The polyimides are useful particularly in the preparation of prepegs and PMR composites.

Synthesis and characterization of poly (benzyl trimethyl ammonium chloride) ionic polymer

NASA Astrophysics Data System (ADS)

Mathew, Manjusha Elizabeth; Ahmad, Ishak; Thomas, Sabu; Daik, Rusli; Kassim, Muhammad

2018-04-01

Poly vinyl benzyl chloride (PVBC) was synthesized by free radical polymerization of 4-vinyl benzyl chloride (VBC) using benzoyl peroxide initiator at 80°C. Amine functionalised polymer prepared by treatment of PVBC with trimethyl amine in different solvents such as water, ethanol, tetra hydro furan(THF) and dimethyl formamide(DMF). The polymers characterized structurally by nuclear magnetic resonance and infrared spectroscopic techniques. The thermal decomposition of the polymer is studied by Thermo Gravimetric Analysis(TGA) and found that the polymer has stability up to 230°C. The nitrogen content of the aminated polymer determined by elemental analysis. The nitrogen content obtained from tetra hydro furan and dimethyl formamide solvents are 20.1% and 19.9% respectively.

Bismesitoylphosphinic Acid (BAPO-OH): A Ligand for Copper Complexes and Four-Electron Photoreductant for the Preparation of Copper Nanomaterials.

PubMed

Beil, Andreas; Müller, Georgina; Käser, Debora; Hattendorf, Bodo; Li, Zhongshu; Krumeich, Frank; Rosenthal, Amos; Rana, Vijay Kumar; Schönberg, Hartmut; Benkő, Zoltán; Grützmacher, Hansjörg

2018-05-16

Bismesitoylphosphinic acid, (HO)PO(COMes) 2 (BAPO-OH), is an efficient photoinitiator for free-radical polymerizations of olefins in aqueous phase. Described here are the structures of various copper(II) and copper(I) complexes with BAPO-OH as the ligand. The complex Cu II (BAPO-O) 2 (H 2 O) 2 is photoactive, and under irradiation with UV light in aqueous phase, it serves as a source of metallic copper in high purity and yield (>80 %). Simultaneously, the radical polymerization of acrylates can be initiated and allows the preparation of nanoparticle/polymer nanocomposites in which the metallic Cu nanoparticles are protected against oxidation. The determination of the stoichiometry of the photoreductions suggests an almost quantitative conversion from Cu II into Cu 0 with half an equivalent of BAPO-OH, which serves as a four-electron photoreductant. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of poly(MAA-g-EG) hydrogel nanoparticles by a thermally-initiated free radical dispersion polymerization.

PubMed

Deng, Liandong; He, Xiaohua; Li, Aigui; Yang, Qiuxia; Dong, Anjie

2007-02-01

Poly(methacrylic acid-grafted-poly(ethylene glycol)) (P(MAA-g-EG)) hydrogel nanoparticles (HNPs) were prepared by a thermally-initiated free radical dispersion polymerization method. The effects of various reaction parameters on the preparation of HNPs were investigated, including the quantity of monomer, temperature, initiator dosage, crosslinker dosage, and co-stabilizer concentration. The reaction temperature at 75 degrees C was found to be suitable for preparing stable and small P(MAA-g-EG) HNPs. By adding a little amount of polyvinyl alcohol in the reaction media, P(MAA-g-EG) HNPs with narrow size distribution could be obtained. The effects of pH and the crosslinker dosage on the equilibrium swelling behavior of P(MAA-g-EG) HNPs were also studied. The P(MAA-g-EG) HNPs perform pH-responsive swelling behavior, which is strongly influenced by the crosslinker dosage.

Synthesis of perm-selective membranes by grafting acrylic acid into air-irradiated Teflon-FEP films

NASA Astrophysics Data System (ADS)

Bozzi, Annick; Chapiro, Adolphe

Grafting acrylic acid into air-irradiated Teflon-FEP films was investigated. Pre-irradiation doses ranged from 0.5 to 10 kGy. Grafting occurred at 45 or 60°C. Homopolymerization inhibitors, ferrous ions or methylene blue, were added to the system. It was found that after completion of the reaction, within 40-100 min, membranes were obtained with very low electric resistivities. The influence of added inhibitors, pre-irradiation dose and grafting temperature was studied. From the results it is concluded that the initiating centers in air-irradiated Teflon-FEP are, on the one hand, peroxides of structure POOP', in which P is a polymeric radical and Pprime; a small fragment, and on the other trapped PO .2 radicals. The latter only react after losing their oxygen. In the presence of polymerization inhibitors, initiation involves a redox process which reduces the overall activation energy.

New core-pyrene π structure organophotocatalysts usable as highly efficient photoinitiators

PubMed Central

Telitel, Sofia; Dumur, Frédéric; Faury, Thomas; Graff, Bernadette; Tehfe, Mohamad-Ali; Fouassier, Jean-Pierre

2013-01-01

Summary Eleven di- and trifunctional compounds based on a core-pyrene π structure (Co_Py) were synthesized and investigated for the formation of free radicals. The application of two- and three-component photoinitiating systems (different Co_Pys with the addition of iodonium or sulfonium salts, alkyl halide or amine) was investigated in detail for cationic and radical photopolymerization reactions under near-UV–vis light. The proposed compounds can behave as new photocatalysts. Successful results in terms of rates of polymerization and final conversions were obtained. The strong MO coupling between the six different cores and the pyrene moiety was studied by DFT calculations. The different chemical intermediates are characterized by ESR and laser flash photolysis experiments. The mechanisms involved in the initiation step are discussed, and relationships between the core structure, the Co_Py absorption property, and the polymerization ability are tentatively proposed. PMID:23766803

Cyclic Multiblock Copolymers via Combination of Iterative Cu(0)-Mediated Radical Polymerization and Cu(I)-Catalyzed Azide-Alkyne Cycloaddition Reaction.

PubMed

Xiao, Lifen; Zhu, Wen; Chen, Jiqiang; Zhang, Ke

2017-02-01

Cyclic multiblock polymers with high-order blocks are synthesized via the combination of single-electron transfer living radical polymerization (SET-LRP) and copper-catalyzed azide-alkyne cycloaddition (CuAAC). The linear α,ω-telechelic multiblock copolymer is prepared via SET-LRP by sequential addition of different monomers. The SET-LRP approach allows well control of the block length and sequence as A-B-C-D-E, etc. The CuAAC is then performed to intramolecularly couple the azide and alkyne end groups of the linear copolymer and produce the corresponding cyclic copolymer. The block sequence and the cyclic topology of the resultant cyclic copolymer are confirmed by the characterization of 1 H nuclear magnetic resonance spectroscopy, gel permeation chromatography, Fourier transform infrared spectroscopy, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Controlled crosslinking of trimethylolpropane trimethacrylate for preparation of organic monolithic columns for capillary liquid chromatography.

PubMed

Gama, Mariana R; Aggarwal, Pankaj; Lee, Milton L; Bottoli, Carla B G

2017-11-01

Organic monolithic columns based on single crosslinking of trimethylolpropane trimethacrylate (TRIM) monomer were prepared in a single step by living/controlled free-radical polymerization. Full optimization of the preparation, such as using different percentages of TRIM and different amounts of radical promoter as well as various porogen solvents were explored. The resulting monolithic columns were characterized by scanning electronic microscopy and nitrogen sorption for structure morphology studies and surface area measurements, respectively. Using capillary liquid chromatography, 150 μm i.d. columns were applied to separate a mixture of small hydrophobic molecules. The results indicated that column performance is highly sensitive to the type and the amount of porogen solvents used in the polymerization mixture composition. Good resolution factors and methylene selectivity were obtained, indicating the promising potential of this material for capillary liquid chromatography separations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

3-Acetyl-11-keto-beta-boswellic acid loaded-polymeric nanomicelles for topical anti-inflammatory and anti-arthritic activity.

PubMed

Goel, Amit; Ahmad, Farhan Jalees; Singh, Raman Mohan; Singh, Gyanendra Nath

2010-02-01

The aim of this study was to develop 3-acetyl-11-keto-beta-boswellic acid (AKBA)-loaded polymeric nanomicelles for topical anti-inflammatory and anti-arthritic activity. Polymeric nanomicelles of AKBA were developed by a radical polymerization method using N-isopropylacrylamide, vinylpyrrolidone and acrylic acid. The polymeric nanomicelles obtained were characterized by Fourier transform infrared (FTIR), transmission electron microscopy (TEM) and dynamic light scattering (DLS). In-vitro and in-vivo evaluations of AKBA polymeric nanomicelles gel were carried out for enhanced skin permeability and anti-inflammatory and anti-arthritic activity. TEM and DLS results demonstrated that polymeric nanomicelles were spherical with a mean diameter approximately 45 nm. FTIR data indicated a weak interaction between polymer and AKBA in the encapsulated system. The release of drug in aqueous buffer (pH 7.4) from the polymeric nanomicelles was 23 and 55% after 2 and 8 h, respectively, indicating sustained release. In-vitro skin permeation studies through excised abdominal skin indicated a threefold increase in skin permeability compared with AKBA gel containing the same amount of AKBA as the AKBA polymeric nanomicelles gel. The AKBA polymeric nanomicelle gel showed significantly enhanced anti-inflammatory and anti-arthritic activity compared with the AKBA gel. This study suggested that AKBA polymeric nanomicelle gel significantly enhanced skin permeability, and anti-inflammatory and anti-arthritic activity.

Radical-initiated controlled synthesis of homo- and copolymers based on acrylonitrile

NASA Astrophysics Data System (ADS)

Grishin, D. F.; Grishin, I. D.

2015-07-01

Data on the controlled synthesis of polyacrylonitrile and acrylonitrile copolymers with other (meth)acrylic and vinyl monomers upon radical initiation and metal complex catalysis are analyzed. Primary attention is given to the use of metal complexes for the synthesis of acrylonitrile-based (co)polymers with defined molecular weight and polydispersity in living mode by atom transfer radical polymerization. The prospects for using known methods of controlled synthesis of macromolecules for the preparation of acrylonitrile homo- and copolymers as carbon fibre precursors are estimated. The major array of published data analyzed in the review refers to the last decade. The bibliography includes 175 references.

Fastest Formation Routes of Nanocarbons in Solution Plasma Processes.

PubMed

Morishita, Tetsunori; Ueno, Tomonaga; Panomsuwan, Gasidit; Hieda, Junko; Yoshida, Akihito; Bratescu, Maria Antoaneta; Saito, Nagahiro

2016-11-14

Although solution-plasma processing enables room-temperature synthesis of nanocarbons, the underlying mechanisms are not well understood. We investigated the routes of solution-plasma-induced nanocarbon formation from hexane, hexadecane, cyclohexane, and benzene. The synthesis rate from benzene was the highest. However, the nanocarbons from linear molecules were more crystalline than those from ring molecules. Linear molecules decomposed into shorter olefins, whereas ring molecules were reconstructed in the plasma. In the saturated ring molecules, C-H dissociation proceeded, followed by conversion into unsaturated ring molecules. However, unsaturated ring molecules were directly polymerized through cation radicals, such as benzene radical cation, and were converted into two- and three-ring molecules at the plasma-solution interface. The nanocarbons from linear molecules were synthesized in plasma from small molecules such as C 2 under heat; the obtained products were the same as those obtained via pyrolysis synthesis. Conversely, the nanocarbons obtained from ring molecules were directly synthesized through an intermediate, such as benzene radical cation, at the interface between plasma and solution, resulting in the same products as those obtained via polymerization. These two different reaction fields provide a reasonable explanation for the fastest synthesis rate observed in the case of benzene.

Fastest Formation Routes of Nanocarbons in Solution Plasma Processes

PubMed Central

Morishita, Tetsunori; Ueno, Tomonaga; Panomsuwan, Gasidit; Hieda, Junko; Yoshida, Akihito; Bratescu, Maria Antoaneta; Saito, Nagahiro

2016-01-01

Although solution-plasma processing enables room-temperature synthesis of nanocarbons, the underlying mechanisms are not well understood. We investigated the routes of solution-plasma-induced nanocarbon formation from hexane, hexadecane, cyclohexane, and benzene. The synthesis rate from benzene was the highest. However, the nanocarbons from linear molecules were more crystalline than those from ring molecules. Linear molecules decomposed into shorter olefins, whereas ring molecules were reconstructed in the plasma. In the saturated ring molecules, C–H dissociation proceeded, followed by conversion into unsaturated ring molecules. However, unsaturated ring molecules were directly polymerized through cation radicals, such as benzene radical cation, and were converted into two- and three-ring molecules at the plasma–solution interface. The nanocarbons from linear molecules were synthesized in plasma from small molecules such as C2 under heat; the obtained products were the same as those obtained via pyrolysis synthesis. Conversely, the nanocarbons obtained from ring molecules were directly synthesized through an intermediate, such as benzene radical cation, at the interface between plasma and solution, resulting in the same products as those obtained via polymerization. These two different reaction fields provide a reasonable explanation for the fastest synthesis rate observed in the case of benzene. PMID:27841288

Radical routes to interstellar glycolaldehyde. The possibility of stereoselectivity in gas-phase polymerization reactions involving CH(2)O and ˙CH(2)OH.

PubMed

Wang, Tianfang; Bowie, John H

2010-10-21

A previous report that the interstellar molecule glycolaldehyde (HOCH(2)CHO) can be made from hydroxymethylene (HOCH:) and formaldehyde has been revisited at the CCSD(T)/6-311++G(3df,2p)//MP2/6-311++G(3df,2p) level of theory. This reaction competes with the formation of acetic acid and methylformate, molecules which have also been detected in interstellar clouds. Other possible modes of formation of glycolaldehyde by radical/radical reactions have been shown to be viable theoretically as follows: HO˙+˙CH2CHO -->HOCH2CHO [ΔG(Γ)(298K)=-303kJ mol⁻¹] HOCH2˙+˙CHO-->HOCH2CHO (-259kJ mol⁻¹). The species in these two processes are known interstellar molecules. Key radicals ˙CH(2)CHO and ˙CH(2)OH in these sequences have been shown to be stable for the microsecond duration of neutralization/reionization experiments in the dual collision cells of a VG ZAB 2HF mass spectrometer. The polymerization reaction HOCH(2)CH˙OH + nCH(2)O → HOCH(2)[CH(OH)](n)˙CHOH (n = 1 to 3) has been studied theoretically and shown to be energetically feasible, as is the cyclization reaction of HOCH(2)[(CH(2)OH)(4)]˙CHOH (in the presence of one molecule of water at the reacting centre) to form glucose. The probability of such a reaction sequence is small even if polymerization were to occur in interstellar ice containing a significant concentration of CH(2)O. The large number of stereoisomers produced by such a reaction sequence makes the formation of a particular sugar, again for example glucose, an inefficient synthesis. The possibility of stereoselectivity occurring during the polymerization was investigated for two diastereoisomers of HOCH(2)[(CHOH)](2)˙CHOH. No significant difference was found in the transition state energies for addition of CH(2)O to these two diastereoisomers, but a barrier difference of 12 kJ mol(-1) was found for the H transfer reactions ˙OCH(2)[(CHOH)](2)CH(2)OH → HOCH(2)[(CHOH)(2)˙CHOH of the two diastereoisomers.

Enhanced removal of aqueous acetaminophen by a laccase-catalyzed oxidative coupling reaction under a dual-pH optimization strategy.

PubMed

Wang, Kaidong; Huang, Ke; Jiang, Guoqiang

2018-03-01

Acetaminophen is one kind of pharmaceutical contaminant that has been detected in municipal water and is hard to digest. A laccase-catalyzed oxidative coupling reaction is a potential method of removing acetaminophen from water. In the present study, the kinetics of radical polymerization combined with precipitation was studied, and the dual-pH optimization strategy (the enzyme solution at pH7.4 being added to the substrate solution at pH4.2) was proposed to enhance the removal efficiency of acetaminophen. The reaction kinetics that consisted of the laccase-catalyzed oxidation, radical polymerization and precipitation were studied by UV in situ, LC-MS and DLS (dynamic light scattering) in situ. The results showed that the laccase-catalyzed oxidation is the rate-limiting step in the whole process. The higher rate of enzyme-catalyzed oxidation under a dual-pH optimization strategy led to much faster formation of the dimer, trimer and tetramer. Similarly, the formation of polymerized products that could precipitate naturally from water was faster. Under the dual-pH optimization strategy, the initial laccase activity was increased approximately 2.9-fold, and the activity remained higher for >250s, during which approximately 63.7% of the total acetaminophen was transformed into biologically inactive polymerized products, and part of these polymerized products precipitated from the water. Laccase belongs to the family of multi-copper oxidases, and the present study provides a universal method to improve the activity of multi-copper oxidases for the high-performance removal of phenol and its derivatives. Copyright © 2017 Elsevier B.V. All rights reserved.

Degradation and polymerization of monolignols by Abortiporus biennis, and induction of its degradation with a reducing agent.

PubMed

Hong, Chang-Young; Park, Se-Yeong; Kim, Seon-Hong; Lee, Su-Yeon; Choi, Won-Sil; Choi, In-Gyu

2016-10-01

This study was carried out to better understand the characteristic modification mechanisms of monolignols by enzyme system of Abortiporus biennis and to induce the degradation of monolignols. Degradation and polymerization of monolignols were simultaneously induced by A. biennis. Whole cells of A. biennis degraded coniferyl alcohol to vanillin and coniferyl aldehyde, and degraded sinapyl alcohol to 2,6-dimethoxybenzene- 1,4-diol, with the production of dimers. The molecular weight of monolignols treated with A. biennis increased drastically. The activities of lignin degrading enzymes were monitored for 24 h to determine whether there was any correlation between monolignol biomodification and ligninolytic enzymes. We concluded that complex enzyme systems were involved in the degradation and polymerization of monolignols. To degrade monolignols, ascorbic acid was added to the culture medium as a reducing agent. In the presence of ascorbic acid, the molecular weight was less increased in the case of coniferyl alcohol, while that of sinapyl alcohol was similar to that of the control. Furthermore, the addition of ascorbic acid led to the production of various degraded compounds: syringaldehyde and acid compounds. Accordingly, these results demonstrated that ascorbic acid prevented the rapid polymerization of monolignols, thus stabilizing radicals generated by enzymes of A. biennis. Thereafter, A. biennis catalyzed the oxidation of stable monolignols. As a result, ascorbic acid facilitated predominantly monolignols degradation by A. biennis through the stabilization of radicals. These findings showed outstanding ability of A. biennis to modify the lignin compounds rapidly and usefully.

Diffusion-regulated phase-transfer catalysis for atom transfer radical polymerization of methyl methacrylate in an aqueous/organic biphasic system.

PubMed

Ding, Mingqiang; Jiang, Xiaowu; Peng, Jinying; Zhang, Lifen; Cheng, Zhenping; Zhu, Xiulin

2015-03-01

A concept based on diffusion-regulated phase-transfer catalysis (DRPTC) in an aqueous-organic biphasic system with copper-mediated initiators for continuous activator regeneration is successfully developed for atom transfer radical polymerization (ICAR ATRP) (termed DRPTC-based ICAR ATRP here), using methyl methacrylate (MMA) as a model monomer, ethyl α-bromophenylacetate (EBrPA) as an initiator, and tris(2-pyridylmethyl)amine (TPMA) as a ligand. In this system, the monomer and initiating species in toluene (organic phase) and the catalyst complexes in water (aqueous phase) are simply mixed under stirring at room temperature. The trace catalyst complexes transfer into the organic phase via diffusion to trigger ICAR ATRP of MMA with ppm level catalyst content once the system is heated to the polymerization temperature (75 °C). It is found that well-defined PMMA with controlled molecular weights and narrow molecular weight distributions can be obtained easily. Furthermore, the polymerization can be conducted in the presence of limited amounts of air without using tedious degassed procedures. After cooling to room temperature, the upper organic phase is decanted and the lower aqueous phase is reused for another 10 recycling turnovers with ultra low loss of catalyst and ligand loading. At the same time, all the recycled catalyst complexes retain nearly perfect catalytic activity and controllability, indicating a facile and economical strategy for catalyst removal and recycling. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

Light-Regulated Polymerization under Near-Infrared/Far-Red Irradiation Catalyzed by Bacteriochlorophyll a.

PubMed

Shanmugam, Sivaprakash; Xu, Jiangtao; Boyer, Cyrille

2016-01-18

Photoregulated polymerizations are typically conducted using high-energy (UV and blue) light, which may lead to undesired side reactions. Furthermore, as the penetration of visible light is rather limited, the range of applications with such wavelengths is likewise limited. We herein report the first living radical polymerization that can be activated and deactivated by irradiation with near-infrared (NIR) and far-red light. Bacteriochlorophyll a (Bachl a) was employed as a photoredox catalyst for photoinduced electron transfer/reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. Well-defined polymers were thus synthesized within a few hours under NIR (λ=850 nm) and far-red (λ=780 nm) irradiation with excellent control over the molecular weight (M(n)/M(w)<1.25). Taking advantage of the good penetration of NIR light, we showed that the polymerization also proceeded smoothly when a translucent barrier was placed between light source and reaction vessel. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

TRANSITION METAL CATALYZED ATOM TRANSFER RADICAL POLYMERIZATION. (R826735)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

REVERSE ATOM TRANSFER RADICAL POLYMERIZATION IN MINIEMULSION. (R829580)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

ATOM TRANSFER RADICAL POLYMERIZATION IN SUPERCRITICAL CARBON DIOXIDE. (R826735)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

COPPER(I)-CATALYZED ATOM TRANSFER RADICAL POLYMERIZATIONS. (R826735)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

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

Various aspects of ultrasound assisted emulsion polymerization process.

PubMed

Korkut, Ibrahim; Bayramoglu, Mahmut

2014-07-01

In this paper, the effects of ultrasonic (US) power, pulse ratio, probe area and recipe composition were investigated on two process responses namely, monomer (methyl methacrylate, MMA) conversion and electrical energy consumption per mass of product polymer (PMMA). Pulsed mode US is more suitable than continuous mode US for emulsion polymerization. The probe (tip) area has little effect on the yield of polymerization when comparing 19 and 13 mm probes, 13 mm probe performing slightly better for high conversion levels. Meanwhile, large probe area is beneficial for high conversion efficiency of electric energy to US energy as well as for high radical generation yield per energy consumed. The conversion increased slightly and electrical energy consumption decreased substantially by using a recipe with high SDS and monomer concentrations. Conclusions presented in this paper may be useful for scale-up of US assisted emulsion polymerization. Copyright © 2014 Elsevier B.V. All rights reserved.

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

Wei, Chan Yi, E-mail: vicchanyiwei@hotmail.com; Ongkudon, Clarence M., E-mail: clarence@ums.edu.my; Kansil, Tamar, E-mail: tamarkansil87@gmail.com

Modern day synthesis protocols of methacrylate monolithic polymer adsorbent are based on existing polymerization blueprint without a thorough understanding of the dynamics of pore structure and formation. This has resulted in unproductiveness of polymer adsorbent consequently affecting purity and recovery of final product, productivity, retention time and cost effectiveness of the whole process. The problems magnified in monolith scaling-up where internal heat buildup resulting from external heating and high exothermic polymerization reaction was reflected in cracking of the adsorbent. We believe that through careful and precise control of the polymerization kinetics and parameters, it is possible to prepare macroporous methacrylatemore » monolithic adsorbents with controlled pore structures despite being carried out in an unstirred mould. This research involved the study of the effect of scaling-up on pore morphology of monolith, in other words, porous polymethacrylate adsorbents that were prepared via bulk free radical polymerization process by imaging the porous morphology of polymethacrylate with scanning electron microscope.« less

Synthesis of nanostructured bio-related materials by hybridization of synthetic polymers with polysaccharides or saccharide residues.

PubMed

Kaneko, Yoshiro; Kadokawa, Jun-Ichi

2006-01-01

In the first part of this review, we describe the synthesis of nanostructured hybrid materials composed of polysaccharides and synthetic polymers. Amylose-synthetic polymer inclusion complexes were synthesized by amylose-forming polymerization using phosphorylase enzyme in the presence of synthetic polymers such as polyethers and polyesters. Alginate-polymethacrylate hybrid materials were prepared by free-radical polymerization of cationic methacrylate in the presence of sodium alginate. These methods allow the simultaneous control of the nanostructure with polymerization, giving well-defined hybrid materials. In the second part of this review, we describe the synthesis of novel glycopolymers with rigid structures. Polyaniline-based glycopolymers were synthesized by means of oxidative polymerization of N-glycosylaniline. Polysiloxane-based glycopolymers were prepared by means of introduction of sugar-lactone to the rodlike polysiloxane. These glycopolymers had regular higher-ordered structures due to their rigid polymer backbones, resulting in control of the three-dimensional array of sugar-residues.

ION EXCHANGE SUBSTANCES BY SAPONIFICATION OF ALLYL PHOSPHATE POLYMERS

DOEpatents

Kennedy, J.

1959-04-14

An ion exchange resin having a relatively high adsorption capacity tor uranyl ion as compared with many common cations is reported. The resin comprises an alphyl-allyl hydrogen phosphate polymer, the alphyl group being either allyl or a lower alkyl group having up to 5 carbon atoins. The resin is prepared by polymerizing compounds such as alkyl-diallyl phosphate and triallyl phosphate in the presence of a free radical generating substance and then partially hydrolyzing the resulting polymer to cause partial replacement of organic radicals by cations. A preferred free radical gencrating agent is dibenzoyl peroxide. The partial hydrolysis is brought about by refluxing the polymer with concentrated aqueous NaOH for three or four hours.

Oligosaccharide/silicon-containing block copolymers with 5 nm features for lithographic applications.

PubMed

Cushen, Julia D; Otsuka, Issei; Bates, Christopher M; Halila, Sami; Fort, Sébastien; Rochas, Cyrille; Easley, Jeffrey A; Rausch, Erica L; Thio, Anthony; Borsali, Redouane; Willson, C Grant; Ellison, Christopher J

2012-04-24

Block copolymers demonstrate potential for use in next-generation lithography due to their ability to self-assemble into well-ordered periodic arrays on the 3-100 nm length scale. The successful lithographic application of block copolymers relies on three critical conditions being met: high Flory-Huggins interaction parameters (χ), which enable formation of <10 nm features, etch selectivity between blocks for facile pattern transfer, and thin film self-assembly control. The present paper describes the synthesis and self-assembly of block copolymers composed of naturally derived oligosaccharides coupled to a silicon-containing polystyrene derivative synthesized by activators regenerated by electron transfer atom transfer radical polymerization. The block copolymers have a large χ and a low degree of polymerization (N) enabling formation of 5 nm feature diameters, incorporate silicon in one block for oxygen reactive ion etch contrast, and exhibit bulk and thin film self-assembly of hexagonally packed cylinders facilitated by a combination of spin coating and solvent annealing techniques. As observed by small angle X-ray scattering and atomic force microscopy, these materials exhibit some of the smallest block copolymer features in the bulk and in thin films reported to date.

Synthesis of hollow spherical calcium phosphate nanoparticles using polymeric nanotemplates

NASA Astrophysics Data System (ADS)

Tjandra, Wiliana; Ravi, Palaniswamy; Yao, Jia; Tam, Kam C.

2006-12-01

Poly(methylmethacrylate)-block-poly(methacrylic acid) (PMMA-b-PMAA) copolymer was synthesized by an atom transfer radical polymerization (ATRP) technique. The block copolymer was employed as a template for the controlled precipitation of calcium phosphate from aqueous solution at different pH values. A Ca2+ ion selective electrode was used to study the interactions between Ca2+ ions and the polymer, which indicated a possible weak interaction between Ca2+ and un-ionized MAA segments at pH~4.0 in addition to electrostatic interaction between Ca2+ and ionized MAA segments at higher pH. An interesting structure representing that of a superstructure consisting of hybrid nano-filaments was observed by the transmission electron microscope at pH~4.0. The filaments originated from a core of similar size to primary polymer aggregates, suggesting that cooperative interactions at a local level between dissolving calcium phosphate clusters and disassembling polymer segments are responsible for the secondary growth process. A hollow spherical morphology was obtained at pH~7.0 and 9.0. Such calcium phosphate/polymer monohybrids with complex morphologies are interesting and might be useful as novel drug delivery carriers, ceramics precursors, reinforcing fillers or biomedical implants.

Facile synthesis of main-chain degradable block copolymers for performance enhanced dismantlable adhesion.

PubMed

Sato, Eriko; Hagihara, Takashi; Matsumoto, Akikazu

2012-04-01

Block copolymers consisting of readily degradable polyperoxides and non-degradable vinyl polymers as the block segments were successfully synthesized by reversible chain transfer catalyzed polymerization, which is one of living radical polymerization techniques. The block copolymers showed characteristic morphology and wettability being different from the polymer blends. When block copolymers containing polyperoxide and polymethacrylate blocks were heated below 150 °C, the polyperoxide blocks were completely degraded and the polymethacrylate blocks were recovered without degradation. Block copolymers containing a poly(2-ethylhexyl methacrylate) block were then investigated as a dismantlable adhesion material, which requires adequate bonding strength during use and easy debonding on demand. Among the several block copolymers, the one consisting of poly(2-ethylhexyl methacrylate) and polyperoxide from methyl sorbate (PPMS) (M(n) = 4900) exhibited good performance as a pressure-sensitive adhesive (PSA). After heating the test specimens in a temperature range from 60 to 100 °C, PSA performance, which was evaluated by 180° peel strength and shear holding power measurements, was significantly diminished. Especially, after heating at 100 °C for 1 h, spontaneous debonding of some test specimens was observed because of the evolution of volatile acetaldehyde from PPMS.

Covalent Immobilization of (-)-Riboflavin on Polymer Functionalized Silica Particles: Application in the Photocatalytic E→Z Isomerization of Polarized Alkenes.

PubMed

Metternich, Jan B; Sagebiel, Sven; Lückener, Anne; Lamping, Sebastian; Ravoo, Bart Jan; Gilmour, Ryan

2018-03-20

The covalent immobilization of the biomimetic, photo-organocatalyst (-)-riboflavin on silica micro- and nanoparticles via atom transfer radical polymerization (ATRP) is disclosed. Given the effectiveness of (-)-riboflavin as a versatile, environmentally benign photocatalyst, an immobilization strategy based on acrylate-linker modification of the catalyst core and controlled polymerization on initiator pre-functionalized silica particles has been developed. Validation of this approach is demonstrated in the E→Z isomerization of a benchmark cinnamonitrile (Z/E up to 88:12) with 0.97 mol % catalyst loading. Characterization of the immobilized photocatalyst supports covalent embedding of the catalyst in the polymeric brushes on the silica particle surface. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymerization reactivity of sulfomethylated alkali lignin modified with horseradish peroxidase.

PubMed

Yang, Dongjie; Wu, Xiaolei; Qiu, Xueqing; Chang, Yaqi; Lou, Hongming

2014-03-01

Alkali lignin (AL) was employed as raw materials in the present study. Sulfomethylation was conducted to improve the solubility of AL, while sulfomethylated alkali lignin (SAL) was further polymerized by horseradish peroxidase (HRP). HRP modification caused a significant increase in molecular weight of SAL which was over 20 times. It was also found to increase the amount of sulfonic and carboxyl groups while decrease the amount of phenolic and methoxyl groups in SAL. The adsorption quantity of self-assembled SAL film was improved after HRP modification. Sulfonation and HRP modification were mutually promoted. The polymerization reactivity of SAL in HRP modification was increased with its sulfonation degree. Meanwhile, HRP modification facilitated SAL's radical-sulfonation reaction. Copyright © 2014. Published by Elsevier Ltd.

Photo-induced living radical polymerization of acrylates utilizing a discrete copper(II)-formate complex.

PubMed

Anastasaki, Athina; Nikolaou, Vasiliki; Brandford-Adams, Francesca; Nurumbetov, Gabit; Zhang, Qiang; Clarkson, Guy J; Fox, David J; Wilson, Paul; Kempe, Kristian; Haddleton, David M

2015-04-04

A photo-polymerization protocol, utilizing a pre-formed and well-characterized Cu(II) formate complex, [Cu(Me6-Tren)(O2CH)](ClO4), mediated by UV light is described. In the absence of additional reducing agents and/or photosensitizers, ppm concentrations of the oxidatively stable [Cu(Me6-Tren)(O2CH)](ClO4), furnish near-quantitative conversions within 2 h, yielding poly(acrylates) with low dispersities (∼1.10) and exceptional end-group fidelity, capable of undergoing in situ chain extension and block copolymerization.

Electron-deficient triarylborane block copolymers: synthesis by controlled free radical polymerization and application in the detection of fluoride ions.

PubMed

Cheng, Fei; Bonder, Edward M; Jäkle, Frieder

2013-11-20

Luminescent triarylborane homo and block copolymers with well-defined chain architectures were synthesized via reversible addition-fragmentation chain transfer polymerization of a vinyl-functionalized borane monomer. The Lewis acid properties of the polymers were exploited in the luminescent detection of fluoride ions. A dual-responsive fluoride sensor was developed by taking advantage of the reversible self-assembly of a PNIPAM-based amphiphilic block copolymer. Anion detection in aqueous solution was realized by introducing positively charged pyridinium moieties along the polymer chain.

PHOTOLYTIC AND FREE RADICAL POLYMERIZATION OF EPOXIDIZED PLANT OIL TRIGLYCERIDES. (R829576)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Fundamentals of Atom Transfer Radical Polymerization

ERIC Educational Resources Information Center

Coessens, Veerle M. C.; Matyjaszewski, Krzysztof

2010-01-01

Today's market increasingly demands sophisticated materials for advanced technologies and high-value applications, such as nanocomposites, optoelectronic, or biomedical materials. Therefore, the demand for well-defined polymers with very specific molecular architecture and properties increases. Until recently, these kinds of polymers could only be…

IMMOBILIZATION OF THE COPPER CATALYST IN ATOM TRANSFER RADICAL POLYMERIZATION. (R826735)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

ATOM TRANSFER RADICAL POLYMERIZATION OF STYRENE IN TOLUENE-WATER MIXTURES. (R829580)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

TEMPO addition into pre-irradiated fluoropolymers and living-radical graft polymerization of styrene for preparation of polymer electrolyte membranes

NASA Astrophysics Data System (ADS)

Sawada, Shin-ichi; Suzuki, Akihiro; Terai, Takayuki; Maekawa, Yasunari

2010-04-01

We prepared proton exchange membranes (PEMs) by 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO)-mediated living-radical graft polymerization (LRGP) of styrene into fluoropolymer films and subsequent sulfonation. Poly(vinylidene fluoride) (PVDF) and poly(ethylene- co-tetrafluoroethylene) (ETFE) films were first irradiated and then treated with TEMPO solutions in various solvents. TEMPO addition was confirmed by the test of styrene grafting into TEMPO-treated films at 60 °C, at which the LRGP never proceeds. This test enabled us to differentiate the LRGP from the conventional graft polymerization. In order to gain a deep insight about TEMPO-addition reaction, the TEMPO-penetration behavior into the base polymer films was examined by a permeation experiment and computer simulation. Xylene and dioxane were appropriate solvents for the complete introduction of TEMPO into PVDF and ETFE films, respectively. Then, the LRGP of styrene was performed based on the fully TEMPO-capped films at 125 °C with various solvents. By using an alcoholic solvent, the degree of grafting was enhanced and it reached a maximum of 38%. This grafted film was sulfonated to prepare a PEM showing an ion exchange capacity of 2.2 meq/g and proton conductivity of 1.6×10 -1 S/cm.

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

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.

Poly(vinyl Chloride) Photostabilization in the Presence of Schiff Bases Containing a Thiadiazole Moiety.

PubMed

Shaalan, Naser; Laftah, Nawres; El-Hiti, Gamal A; Alotaibi, Mohammad Hayal; Muslih, Raad; Ahmed, Dina S; Yousif, Emad

2018-04-15

Five Schiff bases containing a thiadiazole moiety have been used as poly(vinyl chloride) photostabilizers at low concentrations. The efficiency of Schiff bases as photostabilizers was investigated using various techniques, for example, the changes in poly(vinyl chloride) infrared spectra, molecular weight, chain scission quantum yield, and surface morphology were monitored upon irradiation with an ultraviolet light. Evidently, all the additives used inhibited poly(vinyl chloride) photodegradation at a significant level. The most efficient Schiff base exhibited a high level of aromaticity and contained a hydroxyl group. It seems possible that such photostabilization could be due to the direct absorption of ultraviolet radiation by the additives. In addition, Schiff bases could act as radical scavengers and proton transfer facilitators to stabilize the polymeric materials.

MIPs in Aqueous Environments.

PubMed

Wan, Ying-chun; Ma, Hui-ting; Lu, Bin

2015-01-01

When organic solvent-compatible molecularly imprinted polymers (MIPs) are used in aqueous environment, how to reduce nonspecific binding is a major challenge. By modifying the binding solvents and introducing appropriate washing and elution steps, even relatively hydrophobic MIPs can gain optimal rebinding selectivity in aqueous conditions. Furthermore, water-compatible MIPs that can be used to treat aqueous samples directly have been prepared. The use of hydrophilic co-monomers, the controlled surface modification through controlled radical polymerization, and the new interfacial molecular imprinting methods are different strategies to prepare water-compatible MIPs. By combining MIPs with other techniques, both organic solvent-compatible and water-compatible MIPs can display better functional performances in aqueous conditions. Intensive studies on MIPs in aqueous conditions can provide new MIPs with much-improved compatibilities that will lead to more interesting applications in biomedicine and biotechnology.

A technique for improved maxillary record base adaptation through controlled polymerization of light-activated dental resins.

PubMed

Hopkins, D S; Phoenix, R D; Abrahamsen, T C

1997-09-01

A technique for the fabrication of light-activated maxillary record bases is described. The use of a segmental polymerization process provides improved palatal adaptation by minimizing the effects of polymerization shrinkage. Utilization of this technique results in record bases that are well adapted to the corresponding master casts.

Poly-N-Isopropylacrylamide/acrylic Acid Copolymers for the Generation of Nanostructures at Mica Surfaces and as Hydrophobic Host Systems for the Porin MspA from Mycobacterium smegmatis.

PubMed

Gamage, Pubudu; Basel, Matthew T; Lovell, Kimberly; Pokhrel, Megh Raj; Battle, Deletria; Ito, Takashi; Pavlenok, Mikhail; Niederweis, Michael; Bossmann, Stefan H

2009-09-17

The work presented here aims at utilizing poly-N-isopropyl-acrylamide/acrylic acid copolymers to create nanostructured layers on mica surfaces by a simple spin-casting procedure. The average composition of the copolymers determined by elemental analysis correlates excellently with the feed composition indicating that the radical polymerization process is statistical. The resulting surfaces were characterized by Atomic Force Microscopy (magnetic AC-mode) at the copolymer/air interface. Postpolymerization modification of the acrylic acid functions with perfluoro-octyl-iodide decreased the tendency towards spontaneous formation of nanopores. Crosslinking of individual polymer chains permitted the generation of ultraflat layers, which hosted the mycobacterial channel protein MspA, without compromising its channel function. The comparison of copolymers of very similar chemical composition that have been prepared by living radical polymerization and classic radical polymerization indicated that differences in polydispersity played only a minor role when poly-N-isopropyl-acrylamide/acrylic acid copolymers were spincast, but a major role when copolymers featuring the strongly hydrophobic perfluoro-octyl-labels were used. The mean pore diameters were 23.8+/-4.4 nm for P[(NIPAM)(95.5)-co-(AA)(4.5)] (PDI (polydispersity index)=1.55) and 21.8+/-4.2 nm for P[(NIPAM)(95.3)-co-(AA)(4.7)] (PDI=1.25). The depth of the nanopores was approx. 4 nm. When depositing P[(NIPAM)(95)-co-(AA)(2.8)-AAC(8)F(17 2.2)] (PDI=1.29) on Mica, the resulting mean pore diameter was 35.8+/-7.1 nm, with a depth of only 2 nm.

Poly-N-Isopropylacrylamide/acrylic Acid Copolymers for the Generation of Nanostructures at Mica Surfaces and as Hydrophobic Host Systems for the Porin MspA from Mycobacterium smegmatis

PubMed Central

Gamage, Pubudu; Basel, Matthew T.; Lovell, Kimberly; Pokhrel, Megh Raj; Battle, Deletria; Ito, Takashi; Pavlenok, Mikhail; Niederweis, Michael

2009-01-01

The work presented here aims at utilizing poly-N-isopropyl-acrylamide/acrylic acid copolymers to create nanostructured layers on mica surfaces by a simple spin-casting procedure. The average composition of the copolymers determined by elemental analysis correlates excellently with the feed composition indicating that the radical polymerization process is statistical. The resulting surfaces were characterized by Atomic Force Microscopy (magnetic AC-mode) at the copolymer/air interface. Postpolymerization modification of the acrylic acid functions with perfluoro-octyl-iodide decreased the tendency towards spontaneous formation of nanopores. Crosslinking of individual polymer chains permitted the generation of ultraflat layers, which hosted the mycobacterial channel protein MspA, without compromising its channel function. The comparison of copolymers of very similar chemical composition that have been prepared by living radical polymerization and classic radical polymerization indicated that differences in polydispersity played only a minor role when poly-N-isopropyl-acrylamide/acrylic acid copolymers were spincast, but a major role when copolymers featuring the strongly hydrophobic perfluoro-octyl-labels were used. The mean pore diameters were 23.8±4.4 nm for P[(NIPAM)95.5-co-(AA)4.5] (PDI (polydispersity index)=1.55) and 21.8±4.2 nm for P[(NIPAM)95.3-co-(AA)4.7] (PDI=1.25). The depth of the nanopores was approx. 4 nm. When depositing P[(NIPAM)95-co-(AA)2.8-AAC8F17 2.2] (PDI=1.29) on Mica, the resulting mean pore diameter was 35.8±7.1 nm, with a depth of only 2 nm. PMID:20161351

Molecularly Imprinted Polymers: Novel Discovery for Drug Delivery.

PubMed

Dhanashree, Surve; Priyanka, Mohite; Manisha, Karpe; Vilasrao, Kadam

2016-01-01

Molecularly imprinted polymers (MIP) are novel carriers synthesized by imprinting of a template over a polymer. This paper presents the recent application of MIP for diagnostic and therapeutic drug delivery. MIP owing to their 3D polymeric structures and due to bond formation with the template serves as a reservoir of active causing stimuli sensitive, enantioselective, targetted and/or controlled release. The review elaborates about key factors for optimization of MIP, controlled release by MIP for various administration routes various forms like patches, contact lenses, nanowires along with illustrations. To overcome the limitation of organic solvent usage causing increased cost, water compatible MIP and use of supercritical fluid technology for molecular imprinting were developed. Novel methods for developing water compatible MIP like pickering emulsion polymerization, co-precipitation method, cyclodextrin imprinting, surface grafting, controlled/living radical chain polymerization methods are described with illustration in this review. Various protein imprinting methods like bulk, epitope and surface imprinting are described along with illustrations. Further, application of MIP in microdevices as biomimetic sensing element for personalized therapy is elaborated. Although development and application of MIP in drug delivery is still at its infancy, constant efforts of researchers will lead to a novel intelligent drug delivery with commercial value. Efforts should be directed in developing solid oral dosage forms consisting of MIP for therapeutic protein and peptide delivery and targeted release of potent drugs addressing life threatening disease like cancer. Amalgamation of bio-engineering and pharmaceutical techniques can make these future prospects into reality.

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.

Synthesis of sharply thermo and PH responsive PMA-b-PNIPAM-b-PEG-b-PNIPAM-b-PMA by RAFT radical polymerization and its schizophrenic micellization in aqueous solutions.

PubMed

Ahmadkhani, Lida; Abbasian, Mojtaba; Akbarzadeh, Abolfazl

2017-01-01

Sharply thermo- and pH-responsive pentablock terpolymer with a core-shell-corona structure was prepared by RAFT polymerization of N-isopropylacrylamide and methacrylic acid monomers using PEG-based benzoate-type of RAFT agent. The PEG-based RAFT agent could be easily synthesized by dihydroxyl-capped PEG with 4-cyano-4-(thiobenzoyl) sulfanylpentanoic acids, using esterification reaction. This pentablock terpolymer was characterized by 1 H NMR, FT-IR, and GPC. The PDI was obtained by GPC, indicating that the molecular weight distribution was narrow and the polymerization was well controlled. The thermo- and pH-responsive micellization of the pentablock terpolymer in aqueous solution was investigated using fluorescence spectroscopy technique, UV-vis transmittance, and TEM. The LCST of pentablock terpolymer increased (over 50 °C) compared to the NIPAM homopolymer (~32 °C), due to the incorporation of the hydrophilic PEG and PMA blocks in pentablock terpolymer (PNIPAM block as the core, PEG the block and the hydrophilic PMA block as the shell and the corona). Also, pH-dependent phase transition behavior shows at a pH value of about ~5.8, according to pKa of MAA. Thus, in acidic solution at room temperature, the pentablock terpolymer self-assembled to form core-shell-corona micelles, with the hydrophobic PMA block as the core, the PNIPAM block and the hydrophilic PEG block as the shell and the corona, respectively.

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.

Retention of denture bases fabricated by three different processing techniques – An in vivo study

PubMed Central

Chalapathi Kumar, V. H.; Surapaneni, Hemchand; Ravikiran, V.; Chandra, B. Sarat; Balusu, Srilatha; Reddy, V. Naveen

2016-01-01

Aim: Distortion due to Polymerization shrinkage compromises the retention. To evaluate the amount of retention of denture bases fabricated by conventional, anchorized, and injection molding polymerization techniques. Materials and Methods: Ten completely edentulous patients were selected, impressions were made, and master cast obtained was duplicated to fabricate denture bases by three polymerization techniques. Loop was attached to the finished denture bases to estimate the force required to dislodge them by retention apparatus. Readings were subjected to nonparametric Friedman two-way analysis of variance followed by Bonferroni correction methods and Wilcoxon matched-pairs signed-ranks test. Results: Denture bases fabricated by injection molding (3740 g), anchorized techniques (2913 g) recorded greater retention values than conventional technique (2468 g). Significant difference was seen between these techniques. Conclusions: Denture bases obtained by injection molding polymerization technique exhibited maximum retention, followed by anchorized technique, and least retention was seen in conventional molding technique. PMID:27382542

Making Polymeric Microspheres

NASA Technical Reports Server (NTRS)

Rhim, Won-Kyu; Hyson, Michael T.; Chung, Sang-Kun; Colvin, Michael S.; Chang, Manchium

1989-01-01

Combination of advanced techniques yields uniform particles for biomedical applications. Process combines ink-jet and irradiation/freeze-polymerization techniques to make polymeric microspheres of uniform size in diameters from 100 to 400 micrometer. Microspheres used in chromatography, cell sorting, cell labeling, and manufacture of pharmaceutical materials.

Impact of reaction conditions on grafting acrylamide onto starch

USDA-ARS?s Scientific Manuscript database

We have explored the radical initiated graft polymerization reaction of acrylamide onto starch where the solvent, concentration, temperature and reaction times were varied. We have found that the morphology of the resulting grafted polymer is dramatically different and is dependent on the reaction c...

Competency Based Modular Experiments in Polymer Science and Technology.

ERIC Educational Resources Information Center

Pearce, Eli M; And Others

1980-01-01

Describes a competency-based, modular laboratory course emphasizing the synthesis and characterization of polymers and directed toward senior undergraduate and/or first-year graduate students in science and engineering. One module, free-radical polymerization kinetics by dilatometry, is included as a sample. (CS)

40 CFR 61.61 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... polymerization process which initiates from free radical catalyst sites and is sold undried. (i) Bulk resin means... as follows: (a) Ethylene dichloride plant includes any plant which produces ethylene dichloride by reaction of oxygen and hydrogen chloride with ethylene. (b) Vinyl chloride plant includes any plant which...

40 CFR 61.61 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... polymerization process which initiates from free radical catalyst sites and is sold undried. (i) Bulk resin means... as follows: (a) Ethylene dichloride plant includes any plant which produces ethylene dichloride by reaction of oxygen and hydrogen chloride with ethylene. (b) Vinyl chloride plant includes any plant which...

REMOVAL OF CATALYST IN ATOM TRANSFER RADICAL POLYMERIZATION USING ION EXCHANGE RESINS. (R826735)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

WATER-BORNE BLOCK AND STATISTICAL COPOLYMERS SYNTHESIZED USING ATOM TRANSFER RADICAL POLYMERIZATION. (R826735)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Improving Hemocompatibility of Membranes for Extracorporeal Membrane Oxygenators by Grafting Nonthrombogenic Polymer Brushes.

PubMed

Obstals, Fabian; Vorobii, Mariia; Riedel, Tomáš; de Los Santos Pereira, Andres; Bruns, Michael; Singh, Smriti; Rodriguez-Emmenegger, Cesar

2018-03-01

Nonthrombogenic modifications of membranes for extracorporeal membrane oxygenators (ECMOs) are of key interest. The absence of hemocompatibility of these membranes and the need of anticoagulation of patients result in severe and potentially life-threatening complications during ECMO treatment. To address the lack of hemocompatibility of the membrane, surface modifications are developed, which act as barriers to protein adsorption on the membrane and, in this way, prevent activation of the coagulation cascade. The modifications are based on nonionic and zwitterionic polymer brushes grafted directly from poly(4-methyl-1-pentene) (TPX) membranes via single electron transfer-living radical polymerization. Notably, this work introduces the first example of well-controlled surface-initiated radical polymerization of zwitterionic brushes. The antifouling layers markedly increase the recalcification time (a proxy of initiation of coagulation) compared to bare TPX membranes. Furthermore, platelet and leukocyte adhesion is drastically decreased, rendering the ECMO membranes hemocompatible. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

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.

Features of separation on polymeric reversed phase for two classes of higher saturated fatty acids esters

NASA Astrophysics Data System (ADS)

Deineka, V. I.; Lapshova, M. S.; Zakharenko, E. V.; Deineka, L. A.

2013-11-01

The principles of sorption on polymeric reversed phase (PRP) YMS C30 for members of the two classes of esters formed by higher saturated fatty acids, i.e., lutein diesters ( I) and triacylglycerols ( II), are investigated. It is shown that the logarithm of the retention factor increases nonlinearly with an increase of the length of the acid radical, although the retention on PRP is higher in the case of I and lower in the case of II, compared to their retention on traditional monomeric reversed phase (MRP) Kromasil-100 5C18; however, the equivalence of the contributions to the retention of I that correspond to an identical change in acids, does not depend on the length of the hydrocarbon radical of the second acid. It is noted that the Van't Hoff plot for PRP contains a curve break, indicating a change in the retention mechanism upon a rise in temperature.

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.

Thiol-Ene functionalized siloxanes for use as elastomeric dental impression materials

PubMed Central

Cole, Megan A.; Jankousky, Katherine C.; Bowman, Christopher N.

2014-01-01

Objectives Thiol- and allyl-functionalized siloxane oligomers are synthesized and evaluated for use as a radical-mediated, rapid set elastomeric dental impression material. Thiol-ene siloxane formulations are crosslinked using a redox-initiated polymerization scheme, and the mechanical properties of the thiol-ene network are manipulated through the incorporation of varying degrees of plasticizer and kaolin filler. Formulations with medium and light body consistencies are further evaluated for their ability to accurately replicate features on both the gross and microscopic levels. We hypothesize that thiol-ene functionalized siloxane systems will exhibit faster setting times and greater detail reproduction than commercially available polyvinylsiloxane (PVS) materials of comparable consistencies. Methods Thiol-ene functionalized siloxane mixtures formulated with varying levels of redox initiators, plasticizer, and kaolin filler are made and evaluated for their polymerization speed (FTIR), consistency (ISO4823.9.2), and surface energy (goniometer). Feature replication is evaluated quantitatively by SEM. The Tg, storage modulus, and creep behavior are determined by DMA. Results Increasing redox initiation rate increases the polymerization rate but at high levels also limits working time. Combining 0.86 wt% oxidizing agent with up to 5 wt% plasticizer gave a working time of 3 min and a setting time of 2 min. The selected medium and light body thiol-ene formulations also achieved greater qualitative detail reproduction than the commercial material and reproduced micrometer patterns with 98% accuracy. Significance Improving detail reproduction and setting speed is a primary focus of dental impression material design and synthesis. Radical-mediated polymerizations, particularly thiol-ene reactions, are recognized for their speed, reduced shrinkage, and ‘click’ nature. PMID:24553250

Polystyrene/Fe3O4 magnetic emulsion and nanocomposite prepared by ultrasonically initiated miniemulsion polymerization.

PubMed

Qiu, Guihua; Wang, Qi; Wang, Chao; Lau, Willie; Guo, Yili

2007-01-01

Ultrasonically initiated miniemulsion polymerization of styrene in the presence of Fe3O4 nanoparticles was successfully employed to prepare polystyrene (PS)/Fe3O4 magnetic emulsion and nanocomposite. The effects of Fe3O4 nanoparticles on miniemulsion polymerization process, the structure, morphology and properties of PS/Fe3O4 nanocomposite were investigated. The increase in the amount of Fe3O4 nanoparticles drastically increases the polymerization rate due to that Fe3O4 nanoparticles increase the number of radicals and the cavitation bubbles. Polymerization kinetics of ultrasonically initiated miniemulsion polymerization is similar to that of conventional miniemulsion polymerization. PS/Fe3O4 magnetic emulsion consists of two types of particles: latex particles with Fe3O4 nanoparticles and latex particles with no encapsulated Fe3O4 nanoparticles. Fe3O4 nanoparticles lower the molecular weight of PS and broaden the molecular weight and particle size distribution. Thermal stability of PS/Fe3O4 nanocomposite increases with the increase in Fe3O4 content. PS/Fe3O4 emulsion and nanocomposite exhibit magnetic properties. PS/Fe3O4 magnetic particles can be separated from the magnetic emulsion by an external magnetic field and redispersed into the emulsion with agitation.

Chromatographic assessment of two hybrid monoliths prepared via epoxy-amine ring-opening polymerization and methacrylate-based free radical polymerization using methacrylate epoxy cyclosiloxane as functional monomer.

PubMed

Wang, Hongwei; Ou, Junjie; Lin, Hui; Liu, Zhongshan; Huang, Guang; Dong, Jing; Zou, Hanfa

2014-11-07

Two kinds of hybrid monolithic columns were prepared by using methacrylate epoxy cyclosiloxane (epoxy-MA) as functional monomer, containing three epoxy moieties and one methacrylate group. One column was in situ fabricated by ring-opening polymerization of epoxy-MA and 1,10-diaminodecane (DAD) using a porogenic system consisting of isopropanol (IPA), H2O and ethanol at 65°C for 12h. The other was prepared by free radical polymerization of epoxy-MA and ethylene dimethacrylate (EDMA) using 1-propanol and 1,4-butanediol as the porogenic solvents at 60°C for 12h. Two hybrid monoliths were investigated on the morphology and chromatographic assessment. Although two kinds of monolithic columns were prepared with epoxy-MA, their morphologies looked rather different. It could be found that the epoxy-MA-DAD monolith possessed higher column efficiencies (25,000-34,000plates/m) for the separation of alkylbenzenes than the epoxy-MA-EDMA monolith (12,000-13,000plates/m) in reversed-phase nano-liquid chromatography (nano-LC). Depending on the remaining epoxy or methacrylate groups on the surface of two pristine monoliths, the epoxy-MA-EDMA monolith could be easily modified with 1-octadecylamine (ODA) via ring-opening reaction, while the epoxy-MA-DAD monolith could be modified with stearyl methacrylate (SMA) via free radical reaction. The chromatographic performance for the separation of alkylbenzenes on SMA-modified epoxy-MA-DAD monolith was remarkably improved (42,000-54,000 plates/m) when compared with that on pristine epoxy-MA-DAD monolith, while it was not obviously enhanced on ODA-modified epoxy-MA-EDMA monolith when compared with that on pristine epoxy-MA-EDMA monolith. The enhancement of the column efficiency of epoxy-MA-DAD monolith after modification might be ascribed to the decreased mass-transfer resistence. The two kinds of hybrid monoliths were also applied for separations of six phenols and seven basic compounds in nano-LC. Copyright © 2014 Elsevier B.V. All rights reserved.

NMR MONITORING OF CHAIN-END FUNCTIONALITY IN ATOM TRANSFER RADICAL POLYMERIZATION OF STYRENE. (R829580)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

THE EFFECT OF LIGANDS ON ATOM TRANSFER RADICAL POLYMERIZATION IN WATER-BORNE SYSTEMS. (R826735)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

REMOVAL OF COPPER-BASED CATALYST IN ATOM TRANSFER RADICAL POLYMERIZATION USING ION EXCHANGE RESINS. (R826735)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

RATIONAL DESIGN OF THE CATALYST FOR ATOM TRANSFER RADICAL POLYMERIZATION IN AQUEOUS MEDIA. (R829580)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

REMOVAL OF CATALYST IN ATOM TRANSFER RADICAL POLYMERIZATION USING CROSSLINKED POLYSTRYRENE ION-EXCHANGE RESINS. (R826735)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Plasma dye coating as straightforward and widely applicable procedure for dye immobilization on polymeric materials.

PubMed

De Smet, Lieselot; Vancoillie, Gertjan; Minshall, Peter; Lava, Kathleen; Steyaert, Iline; Schoolaert, Ella; Van De Walle, Elke; Dubruel, Peter; De Clerck, Karen; Hoogenboom, Richard

2018-03-16

Here, we introduce a novel concept for the fabrication of colored materials with significantly reduced dye leaching through covalent immobilization of the desired dye using plasma-generated surface radicals. This plasma dye coating (PDC) procedure immobilizes a pre-adsorbed layer of a dye functionalized with a radical sensitive group on the surface through radical addition caused by a short plasma treatment. The non-specific nature of the plasma-generated surface radicals allows for a wide variety of dyes including azobenzenes and sulfonphthaleins, functionalized with radical sensitive groups to avoid significant dye degradation, to be combined with various materials including PP, PE, PA6, cellulose, and PTFE. The wide applicability, low consumption of dye, relatively short procedure time, and the possibility of continuous PDC using an atmospheric plasma reactor make this procedure economically interesting for various applications ranging from simple coloring of a material to the fabrication of chromic sensor fabrics as demonstrated by preparing a range of halochromic materials.

Light-harvesting organic photoinitiators of polymerization.

PubMed

Lalevée, Jacques; Tehfe, Mohamad-Ali; Dumur, Frédéric; Gigmes, Didier; Graff, Bernadette; Morlet-Savary, Fabrice; Fouassier, Jean-Pierre

2013-02-12

Two new photoinitiators with unprecedented light absorption properties are proposed on the basis of a suitable truxene skeleton where several UV photoinitiators PI units such as benzophenone and thioxanthone are introduced at the periphery and whose molecular orbitals MO can be coupled with those of the PI units: a red-shifted absorption and a strong increase of the molecular extinction coefficients (by a ≈ 20-1000 fold factor) are found. These compounds are highly efficient light-harvesting photoinitiators. The scope and practicality of these photoinitiators of polymerization can be dramatically expanded, that is, both radical and cationic polymerization processes are accessible upon very soft irradiation conditions (halogen lamp, LED…︁) thanks to the unique light absorption properties of the new proposed structures. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photoinduced Reversible Morphological Transformation of Azobenzene-Containing Pseudo-2D Polymers.

PubMed

Li, Zili; Tang, Miao; Jiang, Chen; Bai, Ruke; Bai, Wei

2018-05-02

2D polymer sheets containing azobenzene are successfully prepared by a facile strategy of "2D self-assembly polymerization (2DSP)" via free radical polymerization in solution. A bola amphiphile containing azobenzene as a novel monomer is designed and synthesized. The results indicate that single-layer covalent pseudo-2D polymers on a micrometer scale are obtained after polymerization with vinyl monomers. Moreover, the 2D polymer sheets are highly sensitive to UV light due to incorporation of azobenzene groups into the polymer. Upon alternative irradiation with UV and visible light, the morphological transformation between sheets and rolled-up nanotubes can be achieved based on the reversible trans-to-cis photoisomerization of azobenzene units in the 2D polymer sheets. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Light-Directed Tuning of Plasmon Resonances via Plasmon-Induced Polymerization Using Hot Electrons

PubMed Central

2017-01-01

The precise morphology of nanoscale gaps between noble-metal nanostructures controls their resonant wavelengths. Here we show photocatalytic plasmon-induced polymerization can locally enlarge the gap size and tune the plasmon resonances. We demonstrate light-directed programmable tuning of plasmons can be self-limiting. Selective control of polymer growth around individual plasmonic nanoparticles is achieved, with simultaneous real-time monitoring of the polymerization process in situ using dark-field spectroscopy. Even without initiators present, we show light-triggered chain growth of various monomers, implying plasmon initiation of free radicals via hot-electron transfer to monomers at the Au surface. This concept not only provides a programmable way to fine-tune plasmons for many applications but also provides a window on polymer chemistry at the sub-nanoscale. PMID:28670601

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.

Oil-in-oil emulsions: a unique tool for the formation of polymer nanoparticles.

PubMed

Klapper, Markus; Nenov, Svetlin; Haschick, Robert; Müller, Kevin; Müllen, Klaus

2008-09-01

Polymer latex particles are nanofunctional materials with widespread applications including electronics, pharmaceuticals, photonics, cosmetics, and coatings. These materials are typically prepared using waterborne heterogeneous systems such as emulsion, miniemulsion, and suspension polymerization. However, all of these processes are limited to water-stable catalysts and monomers mainly polymerizable via radical polymerization. In this Account, we describe a method to overcome this limitation: nonaqueous emulsions can serve as a versatile tool for the synthesis of new types of polymer nanoparticles. To form these emulsions, we first needed to find two nonmiscible nonpolar/polar aprotic organic solvents. We used solvent mixtures of either DMF or acetonitrile in alkanes and carefully designed amphiphilic block and statistical copolymers, such as polyisoprene- b-poly(methyl methacrylate) (PI- b-PMMA), as additives to stabilize these emulsions. Unlike aqueous emulsions, these new emulsion systems allowed the use of water-sensitive monomers and catalysts. Although polyaddition and polycondensation reactions usually lead to a large number of side products and only to oligomers in the aqueous phase, these new conditions resulted in high-molecular-weight, defect-free polymers. Furthermore, conducting nanoparticles were produced by the iron(III)-induced synthesis of poly(ethylenedioxythiophene) (PEDOT) in an emulsion of acetonitrile in cyclohexane. Because metallocenes are sensitive to nitrile and carbonyl groups, the acetonitrile and DMF emulsions were not suitable for carrying out metallocene-catalyzed olefin polymerization. Instead, we developed a second system, which consists of alkanes dispersed in perfluoroalkanes. In this case, we designed a new amphipolar polymeric emulsifier with fluorous and aliphatic side chains to stabilize the emulsions. Such heterogeneous mixtures facilitated the catalytic polymerization of ethylene or propylene to give spherical nanoparticles of high molecular weight polyolefins. These nonaqueous systems also allow for the combination of different polymerization techniques to obtain complex architectures such as core-shell structures. Previously, such structures primarily used vinylic monomers, which greatly limited the number of polymer combinations. We have demonstrated how nonaqueous emulsions allow the use of a broad variety of hydrolyzable monomers and sensitive catalysts to yield polyester, polyurethane, polyamide, conducting polymers, and polyolefin latex particles in one step under ambient reaction conditions. This nonpolar emulsion strategy dramatically increases the chemical palette of polymers that can form nanoparticles via emulsion polymerization.

Comparative Effect of Different Polymerization Techniques on the Flexural and Surface Properties of Acrylic Denture Bases.

PubMed

Gad, Mohammed M; Fouda, Shaimaa M; ArRejaie, Aws S; Al-Thobity, Ahmad M

2017-05-22

Polymerization techniques have been modified to improve physical and mechanical properties of polymethylmethacrylate (PMMA) denture base, as have the laboratory procedures that facilitate denture construction techniques. The purpose of the present study was to investigate the effect of autoclave polymerization on flexural strength, elastic modulus, surface roughness, and the hardness of PMMA denture base resins. Major Base and Vertex Implacryl heat-polymerized acrylic resins were used to fabricate 180 specimens. According to the polymerization technique, tested groups were divided into: group I (water-bath polymerization), group II (short autoclave polymerization cycle, 60°C for 30 minutes, then 130°C for 10 minutes), and group III (long autoclave polymerization cycle, 60°C for 30 minutes, then 130°C for 20 minutes). Each group was divided into two subgroups based on the materials used. Flexural strength and elastic modulus were determined by a three-point bending test. Surface roughness and hardness were evaluated with a profilometer and Vickers hardness (VH) test, respectively. One-way ANOVA and the Tukey-Kramer multiple-comparison test were used for results analysis, which were statistically significant at p ≤ 0.05. Autoclave polymerization showed a significant increase in flexural strength and hardness of the two resins (p < 0.05). The elastic modulus showed a significant increase in the major base resin, while a significant decrease was seen for Vertex Implacryl in all groups (p < 0.05); however, there was no significant difference in surface roughness between autoclave polymerization and water-bath polymerization (p > 0.05). Autoclave polymerization significantly increased the flexural properties and hardness of PMMA denture bases, while the surface roughness was within acceptable clinical limits. For a long autoclave polymerization cycle, it could be used as an alternative to water-bath polymerization. © 2017 by the American College of Prosthodontists.

Styrene Polymerization under Ambient Conditions by using a Transient 1,3,2-Diazaphospholane-2-oxyl Complex.

PubMed

Heurich, Tobias; Qu, Zheng-Wang; Kunzmann, Robert; Schnakenburg, Gregor; Engeser, Marianne; Nožinović, Senada; Streubel, Rainer

2018-04-25

A combined theoretical and experimental study on the formation and reactivity of a P-OTEMP (P-bound TEMPO (TEMPO=2,2,6,6-tetramethyl-piperidin-1-oxyl)) substituted 1,3,2-diazaphospholane W(CO) 5 complex is presented, including DFT-based mechanistic details. The complex possesses a thermally labile O-N bond that cleaves homolytically yielding the transient 1,3,2-diazaphospholane-2-oxyl complex [(CO) 5 W(R 2 PO . )], which acts as a radical initiator for styrene polymerization under ambient conditions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Monomer and metallopolymer compounds of Tb(III) as precursors for OLEDs

NASA Astrophysics Data System (ADS)

Irina, Savchenko; Oleksandra, Berezhnytska; Olena, Trunova; Yaroslav, Fedorov; Sergiy, Smola; Nataliya, Rusakova

2018-03-01

The Terbium (III) complexes [Tb(III)-water, mixed-ligand complex Tb(III)-phenanthroline] with 2-methyl-5-phenyl-1-pentene-3,5-dione were synthesized. The polycomplex was obtained by free-radical polymerization. The results of above studies have shown that the configuration of the chelate unit is unchanged during the polymerization. As a result, the type of coordination was determined and the structure of coordination polyhedra was assumed. The luminescence spectra of obtained metallocomplexes and polymer were investigated and analyzed. The solubilization of terbium complex with phenanthroline, was shown to change luminescence intensity in this complex.

Comparison of In Situ Polymerization and Solution-Dispersion Techniques in the Preparation of Polyimide/Montmorillonite (MMT) Nanocomposites

PubMed Central

Ahmad, Mansor Bin; Gharayebi, Yadollah; Salit, Mohd. Sapuan; Hussein, Mohd. Zobir; Shameli, Kamyar

2011-01-01

In this paper, Polyimide/Montmorillonite Nanocomposites (PI/MMT NCs), based on aromatic diamine (4-Aminophenyl sulfone) (APS) and aromatic dianhydride (3,3′,4,4′-benzophenonetetracarboxylic dianhydride) (BTDA) were prepared using in situ polymerization and solution-dispersion techniques. The prepared PI/MMT NCs films were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The XRD results showed that at the content of 1.0 wt % Organo Montmorillonite (OMMT) for two techniques and 3.0 wt % OMMT for the in situ polymerization technique, the OMMT was well-intercalated, exfoliated and dispersed into polyimide matrix. The OMMT agglomerated when its amount exceeded 10 wt % and 3.0 wt % for solution-dispersion and in situ polymerization techniques respectively. These results were confirmed by the TEM images of the prepared PI/MMT NCs. The TGA thermograms indicated that thermal stability of prepared PI/MMT NCs were increased with the increase of loading that, the effect is higher for the samples prepared by in situ polymerization technique. PMID:22016643

Comparison of in situ polymerization and solution-dispersion techniques in the preparation of Polyimide/Montmorillonite (MMT) Nanocomposites.

PubMed

Ahmad, Mansor Bin; Gharayebi, Yadollah; Salit, Mohd Sapuan; Hussein, Mohd Zobir; Shameli, Kamyar

2011-01-01

In this paper, Polyimide/Montmorillonite Nanocomposites (PI/MMT NCs), based on aromatic diamine (4-Aminophenyl sulfone) (APS) and aromatic dianhydride (3,3',4,4'-benzophenonetetracarboxylic dianhydride) (BTDA) were prepared using in situ polymerization and solution-dispersion techniques. The prepared PI/MMT NCs films were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The XRD results showed that at the content of 1.0 wt % Organo Montmorillonite (OMMT) for two techniques and 3.0 wt % OMMT for the in situ polymerization technique, the OMMT was well-intercalated, exfoliated and dispersed into polyimide matrix. The OMMT agglomerated when its amount exceeded 10 wt % and 3.0 wt % for solution-dispersion and in situ polymerization techniques respectively. These results were confirmed by the TEM images of the prepared PI/MMT NCs. The TGA thermograms indicated that thermal stability of prepared PI/MMT NCs were increased with the increase of loading that, the effect is higher for the samples prepared by in situ polymerization technique.

Nanoreinforced biocompatible hydrogels from wood hemicelluloses and cellulose whiskers

Treesearch

Muzaffer Ahmet Karaaslan; Mandla A. Tshabalala; Daniel J. Yelle; Gisela Buschle-Diller

2011-01-01

Nanoreinforced hydrogels with a unique network structure were prepared from wood cellulose whiskers coated with chemically modified wood hemicelluloses. The hemicelluloses were modified with 2-hydroxyethylmethacrylate prior to adsorption onto the cellulose whiskers in aqueous medium. Synthesis of the hydrogels was accomplished by in situ radical polymerization of the...

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

EFFECT OF (PSEUDO)HALIDE INITIATORS AND COPPER COMPLEXES WITH NON-HALOGEN ANIONS ON THE ATOM TRANSFER RADICAL POLYMERIZATION. (R829580)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

MECHANISTIC ASPECT OF REVERSE ATOM TRANSFER RADICAL POLYMERIZATION OF N-BUTYL METHACRYLATE IN AQUEOUS DISPERSED SYSTEM. (R826735)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

The Preparation and Simple Analysis of a Clay Nanoparticle Composite Hydrogel

ERIC Educational Resources Information Center

Warren, David S.; Sutherland, Sam P. H.; Kao, Jacqueline Y.; Weal, Geoffrey R.; Mackay, Sean M.

2017-01-01

Samples of a composite hydrogel incorporating clay (Laponite XLG and S-482) nanoparticles were prepared using N-isopropylacrylamide. The hydrogels were formed via a radical-initiated addition polymerization using potassium persulfate and N,N,N',N'-tetramethylethylenediamine. Students then measured the force required to stretch the gels and…

Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization from Chlorinated Polypropylene and Polyethylene Trunk Fibers

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

Brown, Suree; Chatterjee, Sabornie; Li, Meijun

Seawater contains a large amount of uranium (~4.5 billion tons) which can serve as a limitless supply of an energy source. However, in order to make the recovery of uranium from seawater economically feasible, lower manufacturing and deployment costs are required, and thus, solid adsorbents must have high uranium uptake, reusability, and high selectivity toward uranium. In this study, atom-transfer radical polymerization (ATRP), without the radiation-induced graft polymerization (RIGP), was used for grafting acrylonitrile (AN) and tert-butyl acrylate (tBA) from a new class of trunk fibers, forming adsorbents in a readily deployable form. The new class of trunk fibers wasmore » prepared by the chlorination of PP round fiber, hollow-gear-shaped PP fiber, and hollow-gear-shaped PE fiber. During ATRP, degrees of grafting (d.g.) varied according to the structure of active chlorine sites on trunk fibers and ATRP conditions, and the d.g. as high as 2570% was obtained. Resulting adsorbent fibers were evaluated in U-spiked simulated seawater and the maximum adsorption capacity of 146.6 g U/kg, much higher than that of a standard adsorbent JAEA fiber (75.1 g/kg), was obtained. This new type of trunk fibers can be used for grafting a variety of uranium-interacting ligands, including designed ligands that are highly selective toward uranium.« less

Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization from Chlorinated Polypropylene and Polyethylene Trunk Fibers

DOE PAGES

Brown, Suree; Chatterjee, Sabornie; Li, Meijun; ...

2015-12-10

Seawater contains a large amount of uranium (~4.5 billion tons) which can serve as a limitless supply of an energy source. However, in order to make the recovery of uranium from seawater economically feasible, lower manufacturing and deployment costs are required, and thus, solid adsorbents must have high uranium uptake, reusability, and high selectivity toward uranium. In this study, atom-transfer radical polymerization (ATRP), without the radiation-induced graft polymerization (RIGP), was used for grafting acrylonitrile (AN) and tert-butyl acrylate (tBA) from a new class of trunk fibers, forming adsorbents in a readily deployable form. The new class of trunk fibers wasmore » prepared by the chlorination of PP round fiber, hollow-gear-shaped PP fiber, and hollow-gear-shaped PE fiber. During ATRP, degrees of grafting (d.g.) varied according to the structure of active chlorine sites on trunk fibers and ATRP conditions, and the d.g. as high as 2570% was obtained. Resulting adsorbent fibers were evaluated in U-spiked simulated seawater and the maximum adsorption capacity of 146.6 g U/kg, much higher than that of a standard adsorbent JAEA fiber (75.1 g/kg), was obtained. This new type of trunk fibers can be used for grafting a variety of uranium-interacting ligands, including designed ligands that are highly selective toward uranium.« less

Synthesis of well-defined bisbenzoin end-functionalized poly(ε-caprolactone) macrophotoinitiator by combination of ROP and click chemistry and its use in the synthesis of star copolymers by photoinduced free radical promoted cationic polymerization

PubMed Central

Uyar, Zafer; Degirmenci, Mustafa; Genli, Nasrettin; Yilmaz, Ayse

2017-01-01

Abstract A new well-defined bisbenzoin group end-functionalized poly(ε-caprolactone) macrophotoinitiator (PCL-(PI)2) was synthesized by combination of ring opening polymerization (ROP) and click chemistry. The ROP of ε-CL monomer in bulk at 110 °C, by means of a hydroxyl functional initiator namely, 3-cyclohexene-1-methanol in conjunction with stannous-2-ethylhexanoate, (Sn(Oct)2), yielded a well-defined PCL with a cyclohexene end-chain group (PCL-CH). The bromination and subsequent azidation of the cyclohexene end-chain group gave bisazido functionalized poly(ε-caprolactone) (PCL-(N3)2). Separately, an acetylene functionalized benzoin photoinitiator (PI-alkyne) was synthesized by using benzoin and propargyl bromide. Then the click reaction between PCL-(N3)2 and PI-alkyne was performed by Cu(I) catalysis. The spectroscopic studies revealed that poly(ε-caprolactone) with bisbenzoin photoactive functional group at the chain end (PCL-(PI)2) with controlled chain length and low-polydispersity was obtained. This PCL-(PI)2 macrophotoinitiator was used as a precursor in photoinduced free radical promoted cationic polymerization to synthesize an AB2-type miktoarm star copolymer consisting of poly(ε-caprolactone) (PCL, as A block) and poly(cyclohexene oxide) (PCHO, as B block), namely PCL(PCHO)2. PMID:29491778

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

Coherent X-ray diffraction imaging of nanoengineered polymeric capsules

NASA Astrophysics Data System (ADS)

Erokhina, S.; Pastorino, L.; Di Lisa, D.; Kiiamov, A. G.; Faizullina, A. R.; Tayurskii, D. A.; Iannotta, S.; Erokhin, V.

2017-10-01

For the first time, nanoengineered polymeric capsules and their architecture have been studied with coherent X-ray diffraction imaging technique. The use of coherent X-ray diffraction imaging technique allowed us to analyze the samples immersed in a liquid. We report about the significant difference between polymeric capsule architectures under dry and liquid conditions.

Newly Developed Techniques on Polycondensation, Ring-Opening Polymerization and Polymer Modification: Focus on Poly(Lactic Acid)

PubMed Central

Hu, Yunzi; Daoud, Walid A.; Cheuk, Kevin Ka Leung; Lin, Carol Sze Ki

2016-01-01

Polycondensation and ring-opening polymerization are two important polymer synthesis methods. Poly(lactic acid), the most typical biodegradable polymer, has been researched extensively from 1900s. It is of significant importance to have an up-to-date review on the recent improvement in techniques for biodegradable polymers. This review takes poly(lactic acid) as the example to present newly developed polymer synthesis techniques on polycondensation and ring-opening polymerization reported in the recent decade (2005–2015) on the basis of industrial technique modifications and advanced laboratory research. Different polymerization methods, including various solvents, heating programs, reaction apparatus and catalyst systems, are summarized and compared with the current industrial production situation. Newly developed modification techniques for polymer properties improvement are also discussed based on the case of poly(lactic acid). PMID:28773260

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

Fast preparation of hybrid monolithic columns via photo-initiated thiol-yne polymerization for capillary liquid chromatography.

PubMed

Ma, Shujuan; Zhang, Haiyang; Li, Ya; Li, Yanan; Zhang, Na; Ou, Junjie; Ye, Mingliang; Wei, Yinmao

2018-02-23

Although several approaches have been developed to fabricate hybrid monoliths, it would still take a few hours to finish the formation of monoliths. Herein, photo-initiated thiol-yne polymerization was first adopted to in situ fabricate hybrid monoliths within the confines of UV-transparent fused-silica capillary. A silicon-containing diyne (1,3-diethynyltetramethyl-disiloxane, DYDS) was copolymerized with three multithiols, 1,6-hexanedithiol, trimethylolpropane tris(3-mercaptopropionate) and pentaerythriol tetrakis(3-mercaptopropionate), by using a binary porogenic system of diethylene glycol diethyl ether (DEGDE)/poly(ethylene glycol) (PEG200) within 10 min. Several characterizations of three hybrid monoliths (assigned as I, II and III, respectively) were performed. The results showed that these hybrid monoliths possessed bicontinuous porous structure, which was remarkably different from that via typical free-radical polymerization. The highest column efficiency of 76,000 plates per meter for butylbenzene was obtained on the column I in reversed-phase liquid chromatography (RPLC). It was observed that the efficiencies for strong-retained butylbenzene were almost close to those of weak-retained benzene, indicating a retention-independent efficient performance of small molecules on hybrid column I. The surface area of this hybrid monolith was very small in the dry state (less than 10.0 m 2 /g), and the chromatographic behavior of hybrid monolithic columns would be possibly explained by radical-mediated step-growth process of thiol-yne polymerization. Finally, the column I was applied for separation of BSA tryptic digest by cLC-MS/MS, indicating satisfactory separation ability for complicated samples. Copyright © 2018 Elsevier B.V. All rights reserved.

Using solvent-free sample preparation to promote protonation of poly(ethylene oxide)s with labile end-groups in matrix-assisted laser desorption/ionisation.

PubMed

Mazarin, Michael; Phan, Trang N T; Charles, Laurence

2008-12-01

Protonation is usually required to observe intact ions during matrix-assisted laser desorption/ionization (MALDI) of polymers containing fragile end-groups while cation adduction induces chain-end degradation. These polymers, generally obtained via living free radical polymerization techniques, are terminated with a functionality in which a bond is prone to homolytic cleavage, as required by the polymerization process. A solvent-free sample preparation method was used here to avoid salt contaminant from the solvent traditionally used in the dried-droplet MALDI procedure. Solvent-based and solvent-free sample preparations were compared for a series of three poly(ethylene oxide) polymers functionalized with a labile end-group in a nitroxide-mediated polymerization reaction, using 2,4,6-trihydroxyacetophenone (THAP) as the matrix without any added salt. Intact oligomer ions could only be produced as protonated molecules in solvent-free MALDI while sodium adducts of degraded polymers were formed from the dried-droplet samples. Although MALDI analysis was performed at the laser threshold, fragmentation of protonated macromolecules was still observed to occur. However, in contrast to sodiated molecules, dissociation of protonated oligomers does not involve the labile C--ON bond of the end-group. As the macromolecule size increased, protonation appeared to be less efficient and sodium adduction became the dominant ionization process, although no sodium salt was added in the preparation. Formation of sodiated degraded macromolecules would be dictated by increasing cation affinity as the size of the oligomers increases and would reveal the presence of salts at trace levels in the MALDI samples.

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.

Powering up the future: radical polymers for battery applications.

PubMed

Janoschka, Tobias; Hager, Martin D; Schubert, Ulrich S

2012-12-18

Our society's dependency on portable electric energy, i.e., rechargeable batteries, which permit power consumption at any place and in any time, will eventually culminate in resource wars on limited commodities like lithium, cobalt, and rare earth metals. The substitution of conventional metals as means of electric charge storage by organic and polymeric materials, which may ultimately be derived from renewable resources, appears to be the only feasible way out. In this context, the novel class of organic radical batteries (ORBs) excelling in rate capability (i.e., charging speed) and cycling stability (>1000 cycles) sets new standards in battery research. This review examines stable nitroxide radical bearing polymers, their processing to battery systems, and their promising performance. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficient, environmentally-friendly and specific valorization of lignin: promising role of non-radical lignolytic enzymes.

PubMed

Wang, Wenya; Zhang, Chao; Sun, Xinxiao; Su, Sisi; Li, Qiang; Linhardt, Robert J

2017-06-01

Lignin is the second most abundant bio-resource in nature. It is increasingly important to convert lignin into high value-added chemicals to accelerate the development of the lignocellulose biorefinery. Over the past several decades, physical and chemical methods have been widely explored to degrade lignin and convert it into valuable chemicals. Unfortunately, these developments have lagged because of several difficulties, of which high energy consumption and non-specific cleavage of chemical bonds in lignin remain the greatest challenges. A large number of enzymes have been discovered for lignin degradation and these are classified as radical lignolytic enzymes and non-radical lignolytic enzymes. Radical lignolytic enzymes, including laccases, lignin peroxidases, manganese peroxidases and versatile peroxidases, are radical-based bio-catalysts, which degrade lignins through non-specific cleavage of chemical bonds but can also catalyze the radical-based re-polymerization of lignin fragments. In contrast, non-radical lignolytic enzymes selectively cleave chemical bonds in lignin and lignin model compounds and, thus, show promise for use in the preparation of high value-added chemicals. In this mini-review, recent developments on non-radical lignolytic enzymes are discussed. These include recently discovered non-radical lignolytic enzymes, their metabolic pathways for lignin conversion, their recent application in the lignin biorefinery, and the combination of bio-catalysts with physical/chemical methods for industrial development of the lignin refinery.

The structural, morphological and thermal properties of grafted pH-sensitive interpenetrating highly porous polymeric composites of sodium alginate/acrylic acid copolymers for controlled delivery of diclofenac potassium.

PubMed

Jalil, Aamir; Khan, Samiullah; Naeem, Fahad; Haider, Malik Suleman; Sarwar, Shoaib; Riaz, Amna; Ranjha, Nazar Muhammad

2017-01-01

In present investigation new formulations of Sodium Alginate/Acrylic acid hydrogels with high porous structure were synthesized by free radical polymerization technique for the controlled drug delivery of analgesic agent to colon. Many structural parameters like molecular weight between crosslinks ( M c ), crosslink density ( M r ), volume interaction parameter ( v 2, s ), Flory Huggins water interaction parameter and diffusion coefficient ( Q ) were calculated. Water uptake studies was conducted in different USP phosphate buffer solutions. All samples showed higher swelling ratio with increasing pH values because of ionization of carboxylic groups at higher pH values. Porosity and gel fraction of all the samples were calculated. New selected samples were loaded with the model drug (diclofenac potassium).The amount of drug loaded and released was determined and it was found that all the samples showed higher release of drug at higher pH values. Release of diclofenac potassium was found to be dependent on the ratio of sodium alginate/acrylic acid, EGDMA and pH of the medium. Experimental data was fitted to various model equations and corresponding parameters were calculated to study the release mechanism. The Structural, Morphological and Thermal Properties of interpenetrating hydrogels were studied by FTIR, XRD, DSC, and SEM.

Chromatic changes to artificial irises produced using different techniques

NASA Astrophysics Data System (ADS)

Bannwart, Lisiane Cristina; Goiato, Marcelo Coelho; dos Santos, Daniela Micheline; Moreno, Amália; Pesqueira, Aldiéris Alves; Haddad, Marcela Filié; Andreotti, Agda Marobo; de Medeiros, Rodrigo Antonio

2013-05-01

Ocular prostheses are important determinants of their users' aesthetic recovery and self-esteem. Because of use, ocular prostheses longevity is strongly affected by instability of the iris color due to polymerization. The goal of this study is to examine how the color of the artificial iris button is affected by different techniques of artificial wear and by the application of varnish following polymerization of the colorless acrylic resin that covers the colored paint. We produce 60 samples (n=10) according to the wear technique applied: conventional technique without varnish (PE); conventional technique with varnish (PEV); technique involving a prefabricated cap without varnish (CA); technique involving a prefabricated cap with varnish (CAV); technique involving inverted painting without varnish (PI); and technique involving inverted painting with varnish (PIV). Color readings using a spectrophotometer are taken before and after polymerization. We submitted the data obtained to analyses of variance and Tukey's test (P<0.05). The color test shows significant changes after polymerization in all groups. The PE and PI techniques have clinically acceptable values of ΔE, independent of whether we apply varnish to protect the paint. The PI technique produces the least color change, whereas the PE and CA techniques significantly improve color stability.

Ab initio evaluation of the thermodynamic and electrochemical properties of alkyl halides and radicals and their mechanistic implications for atom transfer radical polymerization.

PubMed

Lin, Ching Yeh; Coote, Michelle L; Gennaro, Armando; Matyjaszewski, Krzysztof

2008-09-24

High-level ab initio molecular orbital calculations are used to study the thermodynamics and electrochemistry relevant to the mechanism of atom transfer radical polymerization (ATRP). Homolytic bond dissociation energies (BDEs) and standard reduction potentials (SRPs) are reported for a series of alkyl halides (R-X; R = CH 2CN, CH(CH 3)CN, C(CH 3) 2CN, CH 2COOC 2H 5, CH(CH 3)COOCH 3, C(CH 3) 2COOCH 3, C(CH 3) 2COOC 2H 5, CH 2Ph, CH(CH 3)Ph, CH(CH 3)Cl, CH(CH 3)OCOCH 3, CH(Ph)COOCH 3, SO 2Ph, Ph; X = Cl, Br, I) both in the gas phase and in two common organic solvents, acetonitrile and dimethylformamide. The SRPs of the corresponding alkyl radicals, R (*), are also examined. The computational results are in a very good agreement with the experimental data. For all alkyl halides examined, it is found that, in the solution phase, one-electron reduction results in the fragmentation of the R-X bond to the corresponding alkyl radical and halide anion; hence it may be concluded that a hypothetical outer-sphere electron transfer (OSET) in ATRP should occur via concerted dissociative electron transfer rather than a two-step process with radical anion intermediates. Both the homolytic and heterolytic reactions are favored by electron-withdrawing substituents and/or those that stabilize the product alkyl radical, which explains why monomers such as acrylonitrile and styrene require less active ATRP catalysts than vinyl chloride and vinyl acetate. The rate constant of the hypothetical OSET reaction between bromoacetonitrile and Cu (I)/TPMA complex was estimated using Marcus theory for the electron-transfer processes. The estimated rate constant k OSET = approximately 10 (-11) M (-1) s (-1) is significantly smaller than the experimentally measured activation rate constant ( k ISET = approximately 82 M (-1) s (-1) at 25 degrees C in acetonitrile) for the concerted atom transfer mechanism (inner-sphere electron transfer, ISET), implying that the ISET mechanism is preferred. For monomers bearing electron-withdrawing groups, the one-electron reduction of the propagating alkyl radical to the carbanion is thermodynamically and kinetically favored over the one-electron reduction of the corresponding alkyl halide unless the monomer bears strong radical-stabilizing groups. Thus, for monomers such as acrylates, catalysts favoring ISET over OSET are required in order to avoid chain-breaking side reactions.

An Undergraduate Chemistry Laboratory: Synthesis of Well-Defined Polymers by Low-Catalyst-Concentration ATRP and Postpolymerization Modification to Fluorescent Materials

ERIC Educational Resources Information Center

Tsarevsky, Nicolay V.; Woodruf, Shannon R.; Wisian-Neilson, Patty J.

2016-01-01

A two-session experiment is designed to introduce undergraduate students to concepts in catalysis, transition metal complexes, polymer synthesis, and postpolymerization modifications. In the first session, students synthesize poly(glycidyl methacrylate) via low-catalyst-concentration atom transfer radical polymerization (ATRP). The…

Use of the interior cavity of the P22 capsid for site-specific initiation of atom-transfer radical polymerization with high-density cargo loading

NASA Astrophysics Data System (ADS)

Lucon, Janice; Qazi, Shefah; Uchida, Masaki; Bedwell, Gregory J.; Lafrance, Ben; Prevelige, Peter E.; Douglas, Trevor

2012-10-01

Virus-like particles (VLPs) have emerged as important and versatile architectures for chemical manipulation in the development of functional hybrid nanostructures. Here we demonstrate a successful site-selective initiation of atom-transfer radical polymerization reactions to form an addressable polymer constrained within the interior cavity of a VLP. Potentially, this protein-polymer hybrid of P22 and cross-linked poly(2-aminoethyl methacrylate) could be useful as a new high-density delivery vehicle for the encapsulation and delivery of small-molecule cargos. In particular, the encapsulated polymer can act as a scaffold for the attachment of small functional molecules, such as fluorescein dye or the magnetic resonance imaging (MRI) contrast agent Gd-diethylenetriaminepentacetate, through reactions with its pendant primary amine groups. Using this approach, a significant increase in the labelling density of the VLP, compared to that of previous modifications of VLPs, can be achieved. These results highlight the use of multimeric protein-polymer conjugates for their potential utility in the development of VLP-based MRI contrast agents with the possibility of loading other cargos.

Antibacterial inorganic-organic hybrid coatings on stainless steel via consecutive surface-initiated atom transfer radical polymerization for biocorrosion prevention.

PubMed

Yuan, S J; Pehkonen, S O; Ting, Y P; Neoh, K G; Kang, E T

2010-05-04

To enhance the corrosion resistance of stainless steel (SS) and to impart its surface with antibacterial functionality for inhibiting biofilm formation and biocorrosion, well-defined inorganic-organic hybrid coatings, consisting of a polysilsesquioxane inner layer and quaternized poly(2-(dimethyamino)ethyl methacrylate) (P(DMAEMA)) outer blocks, were prepared via successive surface-initiated atom transfer radical polymerization (ATRP) of 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA). The cross-linked P(TMASPMA), or polysilsesquioxane, inner layer provided a durable and resistant coating to electrolytes. The pendant tertiary amino groups of the P(DMAEMA) outer block were quaternized with alkyl halide to produce a high concentration of quaternary ammonium groups with biocidal functionality. The so-synthesized inorganic-organic hybrid coatings on the SS substrates exhibited good anticorrosion and antibacterial effects and inhibited biocorrosion induced by sulfate-reducing bacteria (SRB) in seawater media, as revealed by antibacterial assay and electrochemical analyses, and they are potentially useful to steel-based equipment under harsh industrial and marine environments.

Solution Properties of Amphoteric Random Copolymers Bearing Pendant Sulfonate and Quaternary Ammonium Groups with Controlled Structures.

PubMed

Nakahata, Rina; Yusa, Shin-Ichi

2018-01-05

Amphoteric random copolymers P(AMPS/APTAC50) x , where x = 41, 89, and 117, composed of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS) and 3-acrylamidopropyltrimethylammonium chloride (APTAC) were prepared via reversible addition-fragmentation chain transfer radical polymerization. P(AMPS/APTAC50) x can dissolve in pure water to form small interpolymer aggregates. In aqueous solutions of NaCl, P(AMPS/APTAC50) x can dissolve in the unimer state. Amphoteric random copolymer P(AMPS/APTAC50) c with high molecular weight was prepared via conventional free-radical polymerization. Although P(AMPS/APTAC50) c cannot dissolve in pure water, it can dissolve in aqueous solutions of NaCl. In amphoteric random copolymers with high molecular weight, the possibility of continuous sequences of monomers with the same charge may increase, which may cause strong interactions between polymer chains. When fetal bovine serum (FBS) and polyelectrolytes were mixed in phosphate-buffered saline, the hydrodynamic radius and light-scattering intensity increased. There was no interaction between P(AMPS/APTAC50) x and FBS because corresponding increases could not be observed.

Model of diffusion-assisted direct laser writing by means of nanopolymerization in the presence of radical quencher

NASA Astrophysics Data System (ADS)

Pikulin, Alexander; Bityurin, Nikita; Sokolov, Viktor I.

2015-12-01

Diffusion-assisted direct laser writing (DA-DLW) by multiphoton polymerization has been recently shown to be one of the most promising methods for the high-resolution 3D nanofabrication [I. Sakellari, et al., ACS Nano 6, 2302 (2012)]. The improvement of the writing spatial resolution has been observed under certain conditions when the mobile radical quencher (polymerization inhibitor) is added to the photosensitive composition. In this work, we present a theoretical study of this method, focusing on the resolution capabilities and optimal writing parameters. The laser beam absorption in the polymerizable composition causes the localized depletion of the quencher molecules. If the quencher depletion is balanced by its diffusion from the outside of the focal volume, the quasi-stationary non-equillibrium concentration spatial profile with zero minimum can be obtained. The polymer is then effectively formed only in the domain where the quencher is depleted. The spatially-distributed quencher, in this case, has the effect similar to that of the vortex beam in STimulated Emission Microscopy (STED).

A poly(acrylonitrile)-functionalized porous aromatic framework synthesized by atom-transfer radical polymerization for the extraction of uranium from seawater

DOE PAGES

Yue, Yanfeng; Zhang, Chenxi; Tang, Qing; ...

2015-10-30

In order to ensure a sustainable reserve of fuel for nuclear power generation, tremendous research efforts have been devoted to developing advanced sorbent materials for extracting uranium from seawater. In this work, a porous aromatic framework (PAF) was surface-functionalized with poly(acrylonitrile) through atom-transfer radical polymerization (ATRP). Batches of this adsorbent were conditioned with potassium hydroxide (KOH) at room temperature or 80 °C prior to contact with a uranium-spiked seawater simulant, with minimal differences in uptake observed as a function of conditioning temperature. A maximum capacity of 4.81 g-U/kg-ads was obtained following 42 days contact with uranium-spiked filtered environmental seawater, whichmore » demonstrates a comparable adsorption rate. A kinetic investigation revealed extremely rapid uranyl uptake, with more than 80% saturation reached within 14 days. Furthermore, relying on the semiordered structure of the PAF adsorbent, density functional theory (DFT) calculations reveal cooperative interactions between multiple adsorbent groups yield a strong driving force for uranium binding.« less

Model of diffusion-assisted direct laser writing by means of nanopolymerization in the presence of radical quencher

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

Pikulin, Alexander, E-mail: pikulin@ufp.appl.sci-nnov.ru; Bityurin, Nikita; Institute of Applied Physics of Russian Academy of Sciences, 46, Ul’yanov Str., Nizhniy Novgorod, 603950

Diffusion-assisted direct laser writing (DA-DLW) by multiphoton polymerization has been recently shown to be one of the most promising methods for the high-resolution 3D nanofabrication [I. Sakellari, et al., ACS Nano 6, 2302 (2012)]. The improvement of the writing spatial resolution has been observed under certain conditions when the mobile radical quencher (polymerization inhibitor) is added to the photosensitive composition. In this work, we present a theoretical study of this method, focusing on the resolution capabilities and optimal writing parameters. The laser beam absorption in the polymerizable composition causes the localized depletion of the quencher molecules. If the quencher depletionmore » is balanced by its diffusion from the outside of the focal volume, the quasi-stationary non-equillibrium concentration spatial profile with zero minimum can be obtained. The polymer is then effectively formed only in the domain where the quencher is depleted. The spatially-distributed quencher, in this case, has the effect similar to that of the vortex beam in STimulated Emission Microscopy (STED)« less

Preparation and evaluation of diblock copolymer-grafted silica by sequential surface initiated-atom transfer radical polymerization for reverse-phase/ion-exchange mixed-mode chromatography.

PubMed

Bo, Chun Miao; Wang, Chaozhan; Wei, Yin Mao

2017-12-01

A novel approach that involved the grafting of diblock copolymer with two types of monomer onto substrate by sequential surface initiated-atom transfer radical polymerization was proposed to prepare a mixed-mode chromatographic stationary phase. The distinguishing feature of this method is that it can be applied in the preparation of various mixed-mode stationary phases. In this study, a new reverse-phase/ion-exchange stationary phase was prepared by grafting hydrophobic styrene and cationic sodium 4-styrenesulfonate by the proposed approach onto silica surface. The chromatographic properties of the prepared stationary phase were evaluated by the separation of benzene derivatives, anilines, and β-agonists, and by the effect of pH values and acetonitrile content on the retention. Compared with typical RP columns, the prepared stationary phase achieved the better resolution and higher selectivity at a shorter separation time and lower organic content. Moreover, the application of the prepared column was proved by separating widely distributed polar and charged compounds simultaneously. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ development of self-reinforced cellulose nanocrystals based thermoplastic elastomers by atom transfer radical polymerization.

PubMed

Yu, Juan; Wang, Chunpeng; Wang, Jifu; Chu, Fuxiang

2016-05-05

Recently, the utilization of cellulose nanocrystals (CNCs) as a reinforcing material has received a great attention due to its high elastic modulus. In this article, a novel strategy for the synthesis of self-reinforced CNCs based thermoplastic elastomers (CTPEs) is presented. CNCs were first surface functionalized with an initiator for surface-initiated atom transfer radical polymerization (SI-ATRP). Subsequently, SI-ATRP of methyl methacrylate (MMA) and butyl acrylate (BA) was carried out in the presence of sacrificial initiator to form CTPEs in situ. The CTPEs together with the simple blends of CNCs and linear poly(MMA-co-BA) copolymer (P(MMA-co-BA)) were characterized for comparative study. The results indicated that P(MMA-co-BA) was successfully grafted onto the surface of CNCs and the compatibility between CNCs and the polymer matrix in CTPEs was greatly enhanced. Specially, the CTPEs containing 2.15wt% CNCs increased Tg by 19.2°C and tensile strength by 100% as compared to the linear P(MMA-co-BA). Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

Block copolymers from ionic liquids for the preparation of thin carbonaceous shells

PubMed Central

Hanif, Sadaf; Oschmann, Bernd; Spetter, Dmitri; Tahir, Muhammad Nawaz; Tremel, Wolfgang

2017-01-01

This paper describes the controlled radical polymerization of an ionic-liquid monomer by RAFT polymerization. This allows the control over the molecular weight of ionic liquid blocks in the range of 8000 and 22000 and of the block-copolymer synthesis. In this work we focus on block copolymers with an anchor block. They can be used to control the formation of TiO2 nanoparticles, which are functionalized thereafter with a block of ionic-liquid polymer. Pyrolysis of these polymer functionalized inorganic nanoparticles leads to TiO2 nanoparticles coated with a thin carbonaceous shell. Such materials may, e.g., be interesting as battery materials. PMID:28904612

Block copolymers from ionic liquids for the preparation of thin carbonaceous shells.

PubMed

Hanif, Sadaf; Oschmann, Bernd; Spetter, Dmitri; Tahir, Muhammad Nawaz; Tremel, Wolfgang; Zentel, Rudolf

2017-01-01

This paper describes the controlled radical polymerization of an ionic-liquid monomer by RAFT polymerization. This allows the control over the molecular weight of ionic liquid blocks in the range of 8000 and 22000 and of the block-copolymer synthesis. In this work we focus on block copolymers with an anchor block. They can be used to control the formation of TiO 2 nanoparticles, which are functionalized thereafter with a block of ionic-liquid polymer. Pyrolysis of these polymer functionalized inorganic nanoparticles leads to TiO 2 nanoparticles coated with a thin carbonaceous shell. Such materials may, e.g., be interesting as battery materials.

A new initiating system based on [(SiMes)Ru(PPh3)(Ind)Cl2] combined with azo-bis-isobutyronitrile in the polymerization and copolymerization of styrene and methyl methacrylate.

PubMed

Al-Majid, Abdullah M; Shamsan, Waseem Sharaf; Al-Odayn, Abdel-Basit Mohammed; Nahra, Fady; Aouak, Taieb; Nolan, Steven P

2017-01-01

The homopolymerization and copolymerization of styrene and methyl methacrylate, initiated for the first time by the combination of azo-bis-isobutyronitrile (AIBN) with [(SiMes)Ru(PPh 3 )(Ind)Cl 2 ] complex. The reactions were successfully carried out, on a large scale, in presence this complex at 80 °C. It was concluded from the data obtained that the association of AIBN with the ruthenium complex reduces considerably the transfer reactions and leads to the controlled radical polymerization and the well-defined polymers.

Chemical control of rate and onset temperature of nadimide polymerization

NASA Technical Reports Server (NTRS)

Lauver, R. W.

1985-01-01

The chemistry of norbornenyl capped imide compounds (nadimides) is briefly reviewed with emphasis on the contribution of Diels-Alder reversion in controlling the rate and onset of the thermal polymerization reaction. Control of onset temperature of the cure exotherm by adjusting the concentration of maleimide is demonstrated using selected model compounds. The effects of nitrophenyl compounds as free radical retarders on nadimide reactivity are discussed. A simple copolymerization model is proposed for the overall nadimide cure reaction. An approximate numerical analysis is carried out to demonstrate the ability of the model to simulate the trends observed for both maleimide and nitrophenyl additions.

pH-sensitive Itaconic acid based polymeric hydrogels for dye removal applications.

PubMed

Sakthivel, M; Franklin, D S; Guhanathan, S

2016-12-01

A series of Itaconic Acid (IA) based pH-sensitive polymeric hydrogels were synthesized by condensation polymerization of Itaconic Acid (IA) with Ethylene Glycol (EG) in the presence of an acid medium resulted into pre-polymer. Further, pre-polymer were co-polymerized with Acrylic Acid (AA) through free radical polymerization using Potassium persulphate (KPS). The structural and surface morphological characterizations of the synthesized hydrogels were studied using FT-IR spectroscopy and Scanning Electron Microscope (SEM) respectively. The swelling and swelling equilibrium were performed at varies pH (4.0-10.0). Further, the effects of IA, EG and AA on swelling properties have also been investigated. Thermal stability of synthesized hydrogels have been investigated by TGA, DTA and DSC. The synthesized hydrogels have shown good ability to uptake a Cationic dye. The Methylene blue has been chosen as a model cationic dye. The results of dye removal using IA hydrogels found to have excellent dye removal capacity. Such kind of IA based hydrogels may be recommended for eco-friendly environmental application. viz., removal of dyes and metal ions and sewage water treatment, purification of water etc. Copyright © 2015 Elsevier Inc. All rights reserved.

Preparation of clenbuterol imprinted monolithic polymer with hydrophilic outer layers by reversible addition-fragmentation chain transfer radical polymerization and its application in the clenbuterol determination from human serum by on-line solid-phase extraction/HPLC analysis.

PubMed

Li, Xiaobing; Zhou, Man; Turson, Mamat; Lin, Shen; Jiang, Ping; Dong, Xiangchao

2013-05-21

A novel imprinted monolithic material with the ability of protein exclusion was developed for the selective extraction of clenbuterol (CLE) from biological samples by direct injection in the HPLC analysis. The material has an imprinted inner structure and hydrophilic outer layer. The reversible addition-fragmentation chain transfer (RAFT) polymerization was employed in the material preparation by a two-step procedure. In the first step, clenbuterol imprinted monolithic polymer was synthesized by combining the molecular imprinting and the RAFT polymerization techniques. The resulting monolithic polymer has a RAFT chain transfer agent (trithioester groups) in its structure, which was used to graft poly(glycerol mono-methacrylate) [pGMMA] in the second step by post-RAFT polymerization. The hydrophilic pGMMA layers grafted on the surface of the imprinted monolith created barriers for protein diffusion. More than 90% of bovine serum albumin can be excluded from the pGMMA coated monolithic column. Meanwhile the clenbuterol was retained selectively with a large retention factor. The result indicated that the column, denoted as RA-MIM, has both the merits of a molecularly imprinted polymer and restricted access material. By using RA-MIM as the solid-phase extraction pre-column, an on-line column-switching HPLC method for the determination of clenbuterol in human serum has been established and validated. The recoveries of clenbuterol from the serum were 87.3-96.9% in the spiked level 2-1000 ng mL(-1). Both good linearity (R = 0.999) and acceptable reproducibility (RSD < 7.0%) were obtained. The limit of detection and the limit of quantitation were 0.7 ng mL(-1) and 2.0 ng mL(-1) respectively, which is sensitive in terms of UV detection. The results have demonstrated that the RAFT polymerization can be used to synthesize bi-functional monolithic columns by using its living reaction property. The resulting RA-MIM in this research can be used for efficient clenbuterol determination by HPLC from biological samples.

Recyclable zero-valent iron activating peroxymonosulfate synchronously combined with thermal treatment enhances sludge dewaterability by altering physicochemical and biological properties.

PubMed

Li, Yifu; Yuan, Xingzhong; Wang, Dongbo; Wang, Hou; Wu, Zhibin; Jiang, Longbo; Mo, Dan; Yang, Guojing; Guan, Renpeng; Zeng, Guangming

2018-04-21

In this study, zero valent iron (ZVI) activated peroxymonosulfate (PMS) as novel technique (i.e. ZVI-PMS technology) was employed to enhance sludge dewatering. In optimal sludge dewatering conditions of ZVI and KHSO 5 dosages, the specific resistance to filtration (SRF) was reduced by 83.6%, which was further decreased to 90.6% after combination of ZVI-PMS with thermal treatment at 50 °C (i.e. ZVI-PMS-T technology). Subsequently, the ESR spectrum and quenching tests demonstrated that OH, rather than SO 4 - , was predominant radicals in ZVI-PMS conditioning. Thereafter, the variation of physicochemical properties and the distributions and compositions of extracellular polymeric substances (EPS) were further investigated to uncover the influence of these techniques on sludge bulk properties. The results indicated that sludge particles were disintegrated into smaller particles and surface charges were neutralized, sludge flowability were elevated obviously after treatments. In ZVI cycle experiment, the high dewatering efficiency was maintained by ZVI-PMS and ZVI-PMS-T pretreatment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Dark Photocatalysis: Storage of Solar Energy in Carbon Nitride for Time-Delayed Hydrogen Generation.

PubMed

Lau, Vincent Wing-Hei; Klose, Daniel; Kasap, Hatice; Podjaski, Filip; Pignié, Marie-Claire; Reisner, Erwin; Jeschke, Gunnar; Lotsch, Bettina V

2017-01-09

While natural photosynthesis serves as the model system for efficient charge separation and decoupling of redox reactions, bio-inspired artificial systems typically lack applicability owing to synthetic challenges and structural complexity. We present herein a simple and inexpensive system that, under solar irradiation, forms highly reductive radicals in the presence of an electron donor, with lifetimes exceeding the diurnal cycle. This radical species is formed within a cyanamide-functionalized polymeric network of heptazine units and can give off its trapped electrons in the dark to yield H 2 , triggered by a co-catalyst, thus enabling the temporal decoupling of the light and dark reactions of photocatalytic hydrogen production through the radical's longevity. The system introduced here thus demonstrates a new approach for storing sunlight as long-lived radicals, and provides the structural basis for designing photocatalysts with long-lived photo-induced states. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

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

Carranza, Arturo; Gewin, Mariah; Pojman, John A., E-mail: japojman@lsu.edu

In this study, we present an inexpensive and practical method that allows the monitoring and visualization of front polymerization, propagation, and dynamics. Commercially available europium-doped aluminum oxide powders were combined with video imaging to visualize free-radical propagating polymer fronts. In order to demonstrate the applicability of this method, frontal copolymerization reactions of propoxylated glycerin triacrylate (EB53), pentaerythritol triacrylate (PETA), and pentaerythritol tetra-acrylate (PETEA) with 1,1-Bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane (Luperox 231®) as an initiator were studied and compared to the results obtained by IR imaging. Systems exhibiting higher filler loading, higher EB53 content, and less acrylated monomers showed a marked decrease in front velocity,more » while those with more acrylated monomers and higher crosslinking density showed a marked increase in front velocity. Finally, in order to show the potential of the imaging technique, we studied fronts propagating in planar and spherical geometries.« less

Backfilling-Free Strategy for Biopatterning on Intrinsically Dual-Functionalized Poly[2-Aminoethyl Methacrylate-co-Oligo(Ethylene Glycol) Methacrylate] Films.

PubMed

Lee, Bong Soo; Lee, Juno; Han, Gyeongyeop; Ha, EunRae; Choi, Insung S; Lee, Jungkyu K

2016-07-20

We demonstrated protein and cellular patterning with a soft lithography technique using poly[2-aminoethyl methacrylate-co-oligo(ethylene glycol) methacrylate] films on gold surfaces without employing a backfilling process. The backfilling process plays an important role in successfully generating biopatterns; however, it has potential disadvantages in several interesting research and technical applications. To overcome the issue, a copolymer system having highly reactive functional groups and bioinert properties was introduced through a surface-initiated controlled radical polymerization with 2-aminoethyl methacrylate hydrochloride (AMA) and oligo(ethylene glycol) methacrylate (OEGMA). The prepared poly(AMA-co-OEGMA) film was fully characterized, and among the films having different thicknesses, the 35 nm-thick biotinylated, poly(AMA-co-OEGMA) film exhibited an optimum performance, such as the lowest nonspecific adsorption and the highest specific binding capability toward proteins. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis, characterization, and corrosion protection properties of poly( N-(methacryloyloxymethyl) benzotriazole- co-methyl methacrylate) on mild steel

NASA Astrophysics Data System (ADS)

Srikanth, A. P.; Lavanya, A.; Nanjundan, S.; Rajendran, N.

2006-12-01

The copolymers from different feed ratios of N-(methacryloyloxymethyl) benzotriazole (MMBT) and methyl methacrylate (MMA) has been synthesised using free radical solution polymerization technique and characterized using FT-IR and 13C NMR spectroscopy. The thermal stability of the polymers was studied using theremogravimetrtic analysis (TGA). The corrosion behaviors of mild steel specimens dip coated with different composition of copolymers have been evaluated by potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) method. These electrochemical properties were observed in 0.1 M HCl medium. The polarization and impedance measurements showed different corrosion protection efficiency with change in composition of the copolymers. It was found that the corrosion protection properties are owing to the barrier effect of the polymer layer covered on the mild steel surfaces. However, it was observed that the copolymer obtained from 1:1 mole ratio of MMBT and MMA exhibited better protection efficiency than other combinations.

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

Bolton, Justin; Rzayev, Javid

Polystyrene–poly(methyl methacrylate)–polylactide (PS–PMMA–PLA) triblock bottlebrush copolymer with nearly symmetric volume fractions was synthesized by grafting from a symmetrical triblock backbone and the resulting melt was characterized by scanning electron microscopy and small-angle X-ray scattering. The copolymer backbone was prepared by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization of solketal methacrylate (SM), 2-(bromoisobutyryl)ethyl methacrylate (BIEM), and 5-(trimethylsilyl)-4-pentyn-1-ol methacrylate (TPYM). PMMA branches were grafted by atom transfer radical polymerization from the poly(BIEM) segment, PS branches were grafted by RAFT polymerization from the poly(TPYM) block after installment of the RAFT agents, while PLA side chains were grafted from the deprotected poly(SM) block. Themore » resulting copolymer was found to exhibit a lamellae morphology with a domain spacing of 79 nm. Differential scanning calorimetry analysis indicated that PMMA was preferentially mixing with PS while phase separating from PLA domains.« less

Rapid removal of aniline from contaminated water by a novel polymeric adsorbent.

PubMed

Huang, Yunhong; Xu, Yang; He, Qinghua; Cao, Yusheng; Du, Bibai

2014-01-01

Dummy molecularly imprinted polymers (DMIPs) for aniline were synthesized by a thermal polymerization method using acrylamide as a functional monomer, ethylene dimethacrylate as a crosslinker, 2,2-azobisisobutyronitrile as a free radical initiator, acetonitrile as a porogenic solvent, and analogues of aniline, namely sulfadiazine, as the template. The DMIPs that were obtained showed a high affinity to aniline compared to non-imprinted polymers. It was proven that the DMIPs obtained using sulfadiazine as the template were much better than the molecularly imprinted polymers using aniline as the template. The results indicated that the Freundlich model was fit for the adsorption model of DMIP for aniline and the adsorption model of the DMIP for aniline was multilayer adsorption. Furthermore, the results showed that the DMIP synthesized by bulk polymerization could be used as a novel adsorbent for removal of aniline from contaminated water.

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.

Poly(ionic liquid) based chemosensors for detection of basic amino acids in aqueous medium

NASA Astrophysics Data System (ADS)

Li, Xinjuan; Wang, Kai; Ma, Nana; Jia, Xianbin

2017-09-01

Naked-eye detection of amino acids in water is of great significance in the field of bio-analytical applications. Herein, polymerized ionic liquids (PILs) with controlled chain length structures were synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerization and post-quaternization approach. The amino acids recognition performance of PILs with different alkyl chain lengths and molecular weights was evaluated by naked-eye color change and ultraviolet-visible (UV-vis) spectral studies. These PILs were successfully used for highly sensitive and selective detection of Arg, Lys and His in water. The recognition performance was improved effectively with increased molecular weight of PILs. The biosensitivity of the PILs in water was strongly dependent on their aggregation effect and polarization effect. Highly sensitive and selective detection of amino acids was successfully accomplished by introducing positively charged pyridinium moieties and controlled RAFT radical polymerization.

Synthesis of CO2/N2-triggered reversible stability-controllable poly(2-(diethylamino)ethyl methacrylate)-grafted-AuNPs by surface-initiated atom transfer radical polymerization.

PubMed

Kitayama, Yukiya; Takeuchi, Toshifumi

2014-10-28

CO2/N2-triggered stability-controllable gold nanoparticles (AuNPs) grafted with poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) layers (PDEAEMA-g-AuNPs) were synthesized by the surface-initiated atom transfer radical polymerization of DEAEMA with AuNPs bearing the bis[2-(2-bromoisobutyryloxy)undecyl] layer (grafting from method). Extension of the PDEAEMA chain length increased the stability of the PDEAEMA-g-AuNPs in CO2-bubbled water because of the electrosteric repulsion of the protonated PDEAEMA layer. The chain-length-dependent stability of PDEAEMA-g-AuNPs was confirmed by DLS and UV-vis spectra by using the localized surface plasmon resonance property of the AuNPs, where the extinction wavelength was shifted toward shorter wavelength with increasing PDEAEMA chain length. The reversible stability change with the gas stimuli of CO2/N2 was also successfully demonstrated. Finally, the transfer across the immiscible interface between water and organic solvent was successfully demonstrated by N2-triggered insolubilization of PDEAEMA layer on AuNPs in the aqueous phase, leading to the successful collection of AuNPs using organic solvent from the aqueous phase. Our "grafting from" method of reversible stability-controllable AuNPs can be applied to develop advanced materials such as reusable optical AuNP-based nanosensors because the molecular recognition layer can be constructed by two-step polymerization.

Pathogenic Roles for Fungal Melanins

PubMed Central

Jacobson, Eric S.

2000-01-01

Melanins represent virulence factors for several pathogenic fungi; the number of examples is growing. Thus, albino mutants of several genera (in one case, mutated precisely in the melanizing enzyme) exhibit decreased virulence in mice. We consider the phenomenon in relation to known chemical properties of melanin, beginning with biosynthesis from ortho-hydroquinone precursors which, when oxidized enzymatically to quinones, polymerize spontaneously to melanin. It follows that melanizing intermediates are cross-linking reagents; melanization stabilizes the external cell wall against hydrolysis and is thought to determine semipermeability in the osmotic ram (the appressorium) of certain plant pathogens. Polymeric melanins undergo reversible oxidation-reduction reactions between cell wall-penetrating quinone and hydroquinone oxidation states and thus represent polymeric redox buffers; using strong oxidants, it is possible to titrate the melanin on living cells and thereby demonstrate protection conferred by melanin in several species. The amount of buffering per cell approximately neutralizes the amount of oxidant generated by a single macrophage. Moreover, the intermediate oxidation state, the semiquinone, is a very stable free radical and is thought to trap unpaired electrons. We have suggested that the oxidation state of external melanin may be regulated by external Fe(II). An independent hypothesis holds that in Cryptococcus neoformans, an important function of the melanizing enzyme (apart from melanization) is the oxidation of Fe(II) to Fe(III), thereby forestalling generation of the harmful hydroxyl radical from H2O2. Thus, problems in fungal pathogenesis have led to evolving hypotheses regarding melanin functioning. PMID:11023965

Preparation of heterocyclic block copolymer from perfluoroalkylene oxide alpha, omega-diamidoximes

NASA Technical Reports Server (NTRS)

Ross, L. O.; Rosser, R. W.; Iannone, M. (Inventor)

1979-01-01

Diamidoxime monomers are intermolecularly and thermally condensed to form a heat and chemical resistant polymer containing 1,2,4-oxadiazole linkages with identical bivalent organic radicals or any combination of bivalent organic radicals selected from the group consisting of -(CX(sub 2))p-, wherein P ranges from 2 to 8 when X is fluorine and 2 to 18 when X is hydrogen, chlorine, nitro or aryl; arylene; and an oligometric or polymeric radical prepared by reacting a dicarboxylic acid halide with a fluorinated epoxide and having the formula: (CFY(OCF(sub 2)CFY)sub m)O(CX(sub 2))(sub p)O(CFYCF(sub 2)O)(sub n)CFY wherein Y is flourine or tryifluoromethyl, X is nitro, aryl, hydrogen, chlorine or fluorine, preferably the latter, p ranges from 1 to 18 and m+n ranges from 2 to 7.

Radical nature of C- lignin

Treesearch

Laura Berstis; Thomas Elder; Michael Crowley; Gregg T. Beckham

2016-01-01

The recently discovered lignin composed of caffeoyl alcohol monolignols or C-lignin is particularly intriguing given its homogeneous, linear polymeric structure and exclusive benzodioxane linkage between monomers. By virtue of this simplified chemistry, the potential emerges for improved valorization strategies with C-lignin relative to other natural heterogeneous...

Synthesis and Characterization of Polymer-Metal Nanostructured Membranes

DTIC Science & Technology

ions creating unique polymer -metal nanostructured membranes. A comprehensive materials characterization study was performed to understand their...fluoropolymers were also investigated. First the polymer -metal nanostructure of Nafion with several counter-ions was studied upon supercritical fluid CO2...processing. Then, novel fluorinated block copolymers were synthesized using atom transfer radical polymerization (ATRP) and their resulting nanostructure was

Oil-soluble hairy nanoparticles as lubricant additives

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

Zhao, Bin

Oil-soluble polymer brush-grafted nanoparticles (hairy NPs) were synthesized by surface-initiated atom transfer radical polymerization of lauryl methacrylate from initiator-functionalized silica nanoparticles and used as an additive for polyalphaolefin (PAO) for friction and wear reduction. Addition of 1 wt% hairy nanoparticles into PAO led to significant friction and wear reduction compared with PAO base oil.

WATER-BORNE BLOCK COPOLYMER SYNTHESIS AND A SIMPLE AND EFFECTIVE ONE-POT SYNTHESIS OF ACRYLATE-METHACRYLATE BLOCK COPOLYMERS BY ATOM TRANSFER RADICAL POLYMERIZATION. (R826735)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Self-Assembled Colloidal Particle Clusters from In Situ Pickering-Like Emulsion Polymerization via Single Electron Transfer Mechanism.

PubMed

Yuan, Jinfeng; Zhao, Weiting; Pan, Mingwang; Zhu, Lei

2016-08-01

A simple route is reported to synthesize colloidal particle clusters (CPCs) from self-assembly of in situ poly(vinylidene fluoride)/poly(styrene-co-tert-butyl acrylate) [PVDF/P(St-co-tBA)] Janus particles through one-pot seeded emulsion single electron transfer radical polymerization. In the in situ Pickering-like emulsion polymerization, the tBA/St/PVDF feed ratio and polymerization temperature are important for the formation of well-defined CPCs. When the tBA/St/PVDF feed ratio is 0.75 g/2.5 g/0.5 g and the reaction temperature is 35 °C, relatively uniform raspberry-like CPCs are obtained. The hydrophobicity of the P(St-co-tBA) domains and the affinity of PVDF to the aqueous environment are considered to be the driving force for the self-assembly of the in situ formed PVDF/P(St-co-tBA) Janus particles. The resultant raspberry-like CPCs with PVDF particles protruding outward may be promising for superhydrophobic smart coatings. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Radiation-induced polymerization of glass forming systems. VI. Polymerization rate at higher conversion in binary systems

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

Kaetsu, I.; Ito, A.; Hayashi, K.

1973-08-01

The effect of temperature and composition on the inflection point in the time-conversion curve and the saturated conversion was investigated in the gamma -radio-induced radical polymerization of binary systems consisting of a glass- forming monomer and a solvent. In the polymerization of completely homogeneous systems such as glycidyl methacrylate (GMA) -triacetin and hydroxyethyl methacrylate (HEMA) --propylene glycol systems, the time-conversion curve has an inflection point at polymerization temperatures between T/sub vm/(T/sub v/ of monomer system) and T/sub vp/ (T/sub v/ of polymer system). Such conversions at the inflection point changed monotonically between 0 and 100% in this temperature range. T/submore » v/ was found to be 30 to 50 deg C higher than T/sub g/ (glass transition temperature) and a monotonic function of composition (monomer -- polymer -- solvent). The acceleration effect continued to 100% conversion above T/sub vp/, and no acceleration effect was observed below T/sub vm/. The saturated conversion in homogeneous systems changed monotonically between 0 and 100% for polymerization temperatures between T/sub gm/ (T/sub g/ of monomer system) and T/sub gp/(T of polymer system). T/sub g/ was also a monotonic function of composition. No saturation in conversion was observed above T/sub gp/ , and no polymerization occurred below T/sub gm/. In the polymerization of completely heterogeneous systems such as HEMA-dioctyl phthalate, no acceleration effect was observed at any temperature and composition. The saturated conversion was 100% sbove T/sub g/ of pure HEMA, and no polymerization occurred below this temperature in this system. (auth)« less

Anodic Cyclization Reactions and the Mechanistic Strategies That Enable Optimization.

PubMed

Feng, Ruozhu; Smith, Jake A; Moeller, Kevin D

2017-09-19

Oxidation reactions are powerful tools for synthesis because they allow us to reverse the polarity of electron-rich functional groups, generate highly reactive intermediates, and increase the functionality of molecules. For this reason, oxidation reactions have been and continue to be the subject of intense study. Central to these efforts is the development of mechanism-based strategies that allow us to think about the reactive intermediates that are frequently central to the success of the reactions and the mechanistic pathways that those intermediates trigger. For example, consider oxidative cyclization reactions that are triggered by the removal of an electron from an electron-rich olefin and lead to cyclic products that are functionalized for further elaboration. For these reactions to be successful, the radical cation intermediate must first be generated using conditions that limit its polymerization and then channeled down a productive desired pathway. Following the cyclization, a second oxidation step is necessary for product formation, after which the resulting cation must be quenched in a controlled fashion to avoid undesired elimination reactions. Problems can arise at any one or all of these steps, a fact that frequently complicates reaction optimization and can discourage the development of new transformations. Fortunately, anodic electrochemistry offers an outstanding opportunity to systematically probe the mechanism of oxidative cyclization reactions. The use of electrochemical methods allows for the generation of radical cations under neutral conditions in an environment that helps prevent polymerization of the intermediate. Once the intermediates have been generated, a series of "telltale indicators" can be used to diagnose which step in an oxidative cyclization is problematic for less successful transformation. A set of potential solutions to address each type of problem encountered has been developed. For example, problems with the initial cyclization reaction leading to either polymerization of the radical cation, elimination of a proton from or solvent trapping of that intermediate, or solvent trapping of the radical cation can be identified in the proton NMR spectrum of the crude reaction material. Such an NMR spectrum shows retention of the trapping group. The problems can be addressed by tuning the radical cation, altering the trapping group, or channeling the reactive intermediate down a radical pathway. Specific examples each are shown in this Account. Problems with the second oxidation step can be identified by poor current efficiency or general decomposition in spite of cyclic voltammetry evidence for a rapid cyclization. Solutions involve improving the oxidation conditions for the radical after cyclization by either the addition of a properly placed electron-donating group in the substrate or an increase in the concentration of electrolyte in the reaction (a change that stabilizes the cation generated from the second oxidation step). Problems with the final cation typically lead to overoxidation. Solutions to this problem require an approach that either slows down elimination side reactions or changes the reaction conditions so that the cation can be quickly trapped in an irreversible fashion. Again, this Account highlights these strategies along with the specific experimental protocols utilized.

Design and evaluation of artificial cornea with core-skirt design using polyhydroxyethyl methacrylate and graphite.

PubMed

Sinha, Mukty; Gupte, Tanvi

2017-06-10

Artificial cornea is the effective treatment option for corneal blindness. One of the challenges with the artificial cornea is limited, or no tissue integration necessitates reimplantation due to necrosis or corneal melting. We propose here a new formulation approach for core-skirt incorporating graphite in the outer skirt region to improve cell adhesion. Hydroxyethyl methacrylate (HEMA) and ethylene glycol dimethacrylate were procured from Sigma-Aldrich. Polyhydroxyethyl methacrylate (PHEMA) was synthesized by free radical polymerization of HEMA. PHEMA hydrogel core with graphite incorporated skirt was developed with the help of mould and spacer. Pores were introduced into the skirt by salt leaching technique using sodium chloride as porogen. The porous skirt was improved for its aesthetic appeal of black colour and mechanical strength to sustain intraocular pressure by incorporating graphite. The material properties of the newly developed design were evaluated in terms of wetting behaviour, mechanical strength, water vapour permeability, degradation profile and cell adhesion. The polymerization of HEMA was confirmed by thin layer chromatography and FTIR. Water content of the polymeric film was optimized at 50% where maximum transparency with required refractive index of 1.4 was obtained. The concentration of salt vital for the essential porosity was also optimized using optical microscopy and scanning electron microscopy. Other properties, namely mechanical strength, water vapour transmission rate and degradation behaviour, showed that the developed design is suitable for ocular applications. Furthermore, cell adhesion study confirmed tissue adhesion in the skirt region but absent in the core. The core-skirt design may offer an efficient cornea replacement alternative with enhanced tissue integration in addition to desired mechanical behaviour with a clear and aesthetic vision.

D-Optimal mixture experimental design for stealth biodegradable crosslinked docetaxel-loaded poly-ε-caprolactone nanoparticles manufactured by dispersion polymerization.

PubMed

Ogunwuyi, O; Adesina, S; Akala, E O

2015-03-01

We report here our efforts on the development of stealth biodegradable crosslinked poly-ε-caprolactone nanoparticles by free radical dispersion polymerization suitable for the delivery of bioactive agents. The uniqueness of the dispersion polymerization technique is that it is surfactant free, thereby obviating the problems known to be associated with the use of surfactants in the fabrication of nanoparticles for biomedical applications. Aided by a statistical software for experimental design and analysis, we used D-optimal mixture statistical experimental design to generate thirty batches of nanoparticles prepared by varying the proportion of the components (poly-ε-caprolactone macromonomer, crosslinker, initiators and stabilizer) in acetone/water system. Morphology of the nanoparticles was examined using scanning electron microscopy (SEM). Particle size and zeta potential were measured by dynamic light scattering (DLS). Scheffe polynomial models were generated to predict particle size (nm) and particle surface zeta potential (mV) as functions of the proportion of the components. Solutions were returned from simultaneous optimization of the response variables for component combinations to (a) minimize nanoparticle size (small nanoparticles are internalized into disease organs easily, avoid reticuloendothelial clearance and lung filtration) and (b) maximization of the negative zeta potential values, as it is known that, following injection into the blood stream, nanoparticles with a positive zeta potential pose a threat of causing transient embolism and rapid clearance compared to negatively charged particles. In vitro availability isotherms show that the nanoparticles sustained the release of docetaxel for 72 to 120 hours depending on the formulation. The data show that nanotechnology platforms for controlled delivery of bioactive agents can be developed based on the nanoparticles.

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.

Antimicrobial bacterial cellulose nanocomposites prepared by in situ polymerization of 2-aminoethyl methacrylate.

PubMed

Figueiredo, Ana R P; Figueiredo, Andrea G P R; Silva, Nuno H C S; Barros-Timmons, Ana; Almeida, Adelaide; Silvestre, Armando J D; Freire, Carmen S R

2015-06-05

Antimicrobial bacterial cellulose/poly(2-aminoethyl methacrylate) (BC/PAEM) nanocomposites were prepared by in situ radical polymerization of 2-aminoethyl methacrylate, using variable amounts of N,N-methylenebis(acrylamide) (MBA) as cross-linker. The obtained nanocomposites were characterized in terms of their structure, morphology, thermal stability, mechanical properties and antibacterial activity. The ensuing composite membranes were significantly more transparent than those of pure BC and showed improved thermal and mechanical properties. The antibacterial activity of the obtained nanocomposites was assessed towards a recombinant bioluminescent Escherichia coli and only the non-crosslinked nanocomposite (BC/PAEM) proved to have antibacterial activity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Penicillin-Bound Polyacrylate Nanoparticles: Restoring the Activity of β-Lactam Antibiotics Against MRSA

PubMed Central

Reddy, G. Suresh Kumar; Greenhalgh, Kerriann; Ramaraju, Praveen; Abeylath, Sampath C.; Jang, Seyoung; Dickey, Sonja; Lim, Daniel V.

2007-01-01

This report describes the preparation of antibacterially-active emulsified polyacrylate nanoparticles in which a penicillin antibiotic is covalently conjugated onto the polymeric framework. These nanoparticles were prepared in water by emulsion polymerization of an acrylated penicillin analogue pre-dissolved in a 7:3 (w:w) mixture of butyl acrylate and styrene in the presence of sodium dodecyl sulfate (surfactant) and potassium persulfate (radical initiator). Dynamic light scattering analysis and atomic force microscopy images show that the emulsions contain nanoparticles of approximately 40 nm in diameter. The nanoparticles have equipotent in vitro antibacterial properties against methicillin-susceptible and methicillin-resistant forms of Staphylococcus aureus and indefinite stability towards β-lactamase. PMID:17420125

Roles of Segmental and Oligomeric Diffusion on the Gel Effect in Free Radical Polymerization

NASA Astrophysics Data System (ADS)

Wisnudel, M. B.; Torkelson, J. M.

1996-03-01

Termination between radicals has been simulated by phosphorescence quenching, showing strong roles for segmental and oligomeric radical self-diffusion in the origin of the gel effect. Quenching rate constants (k_q) were measured between benzil-terminated polymer as a function of anthracene-terminated polymer in polymer solutions. In dilute solution, interactions between 10k or 73k MW benzil-terminated polystyrene (PS- B) and anthracence-terminated polystyrene (PS-A) of varying MW, the MW effect is weaker than the Smoluchowski eq. prediction (kq MW^- 0.5). At higher concentration, interactions of PS-B and PS-A of like MW show only weak dependence of kq on MW and a concentration dependence similar to that of segmental mobility, indicating that segmental diffusion is important in termination. Finally, with interactions between 73k MW PS-B and PS-A of varying MW at 35 wt% PS, kq decreases by a factor of 10 in going from MW's of 100 to 1000 g/mol; beyond 1000 g/mol, kq is MW independent. Such effects cannot be explained by polymer-radical self-diffusion. However, they support the notion that the gel effect onset is associated with the concentration dependence of oligomeric radical self-diffusion and polymer radical chain-end segmental mobility.

Synthesis and Characterization of Graft Copolymers Poly(isoprene-g-styrene) of High Molecular Weight by a Combination of Anionic Polymerization and Emulsion Polymerization

DOE PAGES

Wang, Wenwen; Wang, Weiyu; Li, Hui; ...

2015-01-14

In this study, high molecular weight “comb-shaped” graft copolymers, poly(isoprene-g-styrene), with polyisoprene as the backbone and polystyrene as side chains, were synthesized via free radical emulsion polymerization by copolymerization of isoprene with a polystyrene macromonomer synthesized using anionic polymerization. A small amount of toluene was used in order to successfully disperse the macromonomer. Both a redox and thermal initiation system were used in the emulsion polymerization, and the latex particle size and distribution were investigated by dynamic light scattering. The structural characteristics of the macromonomer and comb graft copolymers were investigated through use of size exclusion chromatography, spectroscopy, microscopy, thermalmore » analysis, and rheology. While the macromonomer was successfully copolymerized to obtain the desired multigraft copolymers, small amounts of unreacted macromonomer remained in the products, reflecting its reduced reactivity due to steric effects. Nevertheless, the multigraft copolymers obtained were very high in molecular weight (5–12 × 10 5 g/mol) and up to 10 branches per chain, on average, could be incorporated. A material incorporating 29 wt% polystyrene exhibits a disordered microphase separated morphology and elastomeric properties. As a result, these materials show promise as new, highly tunable, and potentially low cost thermoplastic elastomers.« less

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.

Removal of dye by carboxymethyl cellulose, acrylamide and graphene oxide via a free radical polymerization process.

PubMed

Varaprasad, Kokkarachedu; Jayaramudu, Tippabattini; Sadiku, Emmanuel Rotimi

2017-05-15

Carboxymethyl cellulose has been used for the design of novel engineered hydrogels in order to obtain effective three-dimensional structures for industrial applications. In this work, dye removal carboxymethyl cellulose-acrylamide-graphene oxide (CMC-AM-GO) hydrogels were prepared by a free-radical polymerization method. The GO was developed by the modified Hummers method. The CMC-AM-GO and GO were characterized by FTIR, XRD and SEM. The swelling and swelling kinetics were calculated using gravimetric process. The kinetic parameter, swelling exponent values [n=0.59-0.7507] explained the fact that the CMC-AM-GO hydrogles have super Case II diffusion transport mechanism. CMCx-AM-GO (x=1-4) and CMC-AM hydrogels were used for removal of Acid Blue-133. The result explains that composite hydrogels significantly removed the acid blue when compared to the neat hydrogel. The maximum AB absorption (185.45mg/g) capacity was found in the case of CMC 2 -AM-GO hydrogel. Therefore, cellulose-based GO hydrogels can be termed as smart systems for the abstraction of dye in water purification applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

Homogeneous synthesis of cellulose acrylate-g-poly (n-alkyl acrylate) solid-solid phase change materials via free radical polymerization.

PubMed

Qian, Yong-Qiang; Han, Na; Bo, Yi-Wen; Tan, Lin-Li; Zhang, Long-Fei; Zhang, Xing-Xiang

2018-08-01

A novel solid-solid phase change materials, namely, cellulose acrylate-g-poly (n-alkyl acrylate) (CA-g-PAn) (n = 14, 16 and 18) were successfully synthesized by free radical polymerization in N, N-dimethylacetamide (DMAc). The successful grafting was confirmed by fourier transform infrared spectra (FT-IR) and nuclear magnetic resonance (NMR). The properties of the CA-g-PAn copolymers were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA). The phase change temperatures and the melting enthalpies of CA-g-PAn copolymers are in the range of 10.1-53.2 °C and 15-95 J/g, respectively. It can be adjusted by the contents of poly (n-alkyl acrylate) and the length of alkyl side-chain. The thermal resistant temperatures of CA-g-PA14, 16 and 18 copolymers are 308 °C, 292 °C and 273 °C, respectively. It show that all of grafting materials exhibit good thermal stability and shape stability. Therefore, it is expected to be applied in the cellulose-based thermos-regulating field. Copyright © 2018 Elsevier Ltd. All rights reserved.

Grafting of antibacterial polymers on stainless steel via surface-initiated atom transfer radical polymerization for inhibiting biocorrosion by Desulfovibrio desulfuricans.

PubMed

Yuan, S J; Xu, F J; Pehkonen, S O; Ting, Y P; Neoh, K G; Kang, E T

2009-06-01

To enhance the biocorrosion resistance of stainless steel (SS) and to impart its surface with bactericidal function for inhibiting bacterial adhesion and biofilm formation, well-defined functional polymer brushes were grafted via surface-initiated atom transfer radical polymerization (ATRP) from SS substrates. The trichlorosilane coupling agent, containing the alkyl halide ATRP initiator, was first immobilized on the hydroxylated SS (SS-OH) substrates for surface-initiated ATRP of (2-dimethylamino)ethyl methacrylate (DMAEMA). The tertiary amino groups of covalently immobilized DMAEMA polymer or P(DMAEMA), brushes on the SS substrates were quaternized with benzyl halide to produce the biocidal functionality. Alternatively, covalent coupling of viologen moieties to the tertiary amino groups of P(DMAEMA) brushes on the SS surface resulted in an increase in surface concentration of quaternary ammonium groups, accompanied by substantially enhanced antibacterial and anticorrosion capabilities against Desulfovibrio desulfuricans in anaerobic seawater, as revealed by antibacterial assay and electrochemical studies. With the inherent advantages of high corrosion resistance of SS, and the good antibacterial and anticorrosion capabilities of the viologen-quaternized P(DMAEMA) brushes, the functionalized SS is potentially useful in harsh seawater environments and for desalination plants. Copyright 2009 Wiley Periodicals, Inc.

Inorganic-organic hybrid coatings on stainless steel by layer-by-layer deposition and surface-initiated atom-transfer-radical polymerization for combating biocorrosion.

PubMed

Yuan, S J; Pehkonen, S O; Ting, Y P; Neoh, K G; Kang, E T

2009-03-01

To improve the biocorrosion resistance of stainless steel (SS) and to confer the bactericidal function on its surface for inhibiting bacterial adhesion and biofilm formation, well-defined inorganic-organic hybrid coatings, consisting of the inner compact titanium oxide multilayers and outer dense poly(vinyl-N-hexylpyridinium) brushes, were successfully developed. Nanostructured titanium oxide multilayer coatings were first built up on the SS substrates via the layer-by-layer sol-gel deposition process. The trichlorosilane coupling agent, containing the alkyl halide atom-transfer-radical polymerization (ATRP) initiator, was subsequently immobilized on the titanium oxide coatings for surface-initiated ATRP of 4-vinylpyridine (4VP). The pyridium nitrogen moieties of the covalently immobilized 4VP polymer, or P(4VP), brushes were quaternized with hexyl bromide to produce a high concentration of quaternary ammonium salt on the SS surfaces. The excellent antibacterial efficiency of the grafted polycations, poly(vinyl-N-pyridinium bromide), was revealed by viable cell counts and atomic force microscopy images of the surface. The effectiveness of the hybrid coatings in corrosion protection was verified by the Tafel plot and electrochemical impedance spectroscopy measurements.

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.

Colorful Polyelectrolytes: An Atom Transfer Radical Polymerization Route to Fluorescent Polystyrene Sulfonate.

PubMed

Huberty, Wayne; Tong, Xiaowei; Balamurugan, Sreelatha; Deville, Kyle; Russo, Paul S; Zhang, Donghui

2016-03-01

A labeled green fluorescent polystyrene sulfonate (LNaPSS) has been synthesized using atom transfer radical polymerization of a styrene sulfonate monomer with a fluorescent co-monomer, fluorescein thiocyanate-vinyl aniline. As a result this 100 % sulfonated polymer contains no hydrophobic patches along the chain backbone besides the fluorescent marker itself. The concentration of the fluorescent monomer was kept low to maintain the characteristic properties of the anionic polyelectrolyte, LNaPSS. ATRP conditions facilitated the production of polymers spanning a range of molecular weights from 35,000 to 175,000 in gram-scale batches with polydispersity indices of 1.01-1.24. Molecular weight increased with the monomer to initiator ratio. Gel permeation chromatography results show a unimodal distribution, and the polymer structure was also confirmed by (1)H NMR and FT-IR spectroscopy. Fluorescence spectroscopy confirmed covalent bonding of fluorescein isothiocyanate to the polymer, indicating that the polymer is suitable as a probe in fluorescence microscopy. To demonstrate this ability, the polymer was used to locate structural features in salt crystals formed during drying, as in the evaporation of sea mist. A second application to probe diffusion studies is also demonstrated.

The structural, morphological and thermal properties of grafted pH-sensitive interpenetrating highly porous polymeric composites of sodium alginate/acrylic acid copolymers for controlled delivery of diclofenac potassium

PubMed Central

Jalil, Aamir; Khan, Samiullah; Naeem, Fahad; Haider, Malik Suleman; Sarwar, Shoaib; Riaz, Amna; Ranjha, Nazar Muhammad

2017-01-01

Abstract In present investigation new formulations of Sodium Alginate/Acrylic acid hydrogels with high porous structure were synthesized by free radical polymerization technique for the controlled drug delivery of analgesic agent to colon. Many structural parameters like molecular weight between crosslinks (M c), crosslink density (M r), volume interaction parameter (v 2,s), Flory Huggins water interaction parameter and diffusion coefficient (Q) were calculated. Water uptake studies was conducted in different USP phosphate buffer solutions. All samples showed higher swelling ratio with increasing pH values because of ionization of carboxylic groups at higher pH values. Porosity and gel fraction of all the samples were calculated. New selected samples were loaded with the model drug (diclofenac potassium).The amount of drug loaded and released was determined and it was found that all the samples showed higher release of drug at higher pH values. Release of diclofenac potassium was found to be dependent on the ratio of sodium alginate/acrylic acid, EGDMA and pH of the medium. Experimental data was fitted to various model equations and corresponding parameters were calculated to study the release mechanism. The Structural, Morphological and Thermal Properties of interpenetrating hydrogels were studied by FTIR, XRD, DSC, and SEM. PMID:29491802

Adsorbed Polymer Nanolayers on Solids: Mechanism, Structure and Applications

NASA Astrophysics Data System (ADS)

Sen, Mani Kuntal

In this thesis, by combining various advanced x-ray scattering, spectroscopic and other surface sensitive characterization techniques, I report the equilibrium polymer chain conformations, structures, dynamics and properties of polymeric materials at the solid-polymer melt interfaces. Following the introduction, in chapter 2, I highlight that the backbone chains (constituted of CH and CH2 groups) of the flattened polystyrene (PS) chains preferentially orient normal to the weakly interactive substrate surface via thermal annealing regardless of the initial chain conformations, while the orientation of the phenyl rings becomes randomized, thereby increasing the number of surface-segmental contacts (i.e., enthalpic gain) which is the driving force for the flattening process of the polymer chains even onto a weakly interactive solid. In chapter 3, I elucidate the flattened structures in block copolymer (BCP) thin films where both blocks lie flat on the substrate, forming a 2D randomly phase-separated structure irrespective of their microdomain structures and interfacial energetics. In chapter 4, I reveal the presence of an irreversibly adsorbed BCP layer which showed suppressed dynamics even at temperatures far above the individual glass transition temperatures of the blocks. Furthermore, this adsorbed BCP layer plays a crucial role in controlling the microdomain orientation in the entire film. In chapter 5, I report a radically new paradigm of designing a polymeric coating layer of a few nanometers thick ("polymer nanolayer") with anti-biofouling properties.

Click polymerization for the synthesis of reduction-responsive polymeric prodrug

NASA Astrophysics Data System (ADS)

Zhang, Xiaojin; Wang, Hongquan; Dai, Yu

2018-05-01

Click polymerization is a powerful polymerization technique for the construction of new macromolecules with well-defined structures and multifaceted functionalities. Here, we synthesize reduction-responsive polymeric prodrug PEG- b-(PSS- g-MTX)- b-PEG containing disulfide bonds and pendant methotrexate (MTX) via two-step click polymerization followed by conjugating MTX to pendant hydroxyl. MTX content in polymeric prodrug is 13.5%. Polymeric prodrug is able to form polymeric micelles by self-assembly in aqueous solution. Polymeric micelles are spherical nanoparticles with tens of nanometers in size. Of note, polymeric micelles are reduction-responsive due to disulfide bonds in the backbone of PEG- b-(PSS- g-MTX)- b-PEG and could release pendant drugs in the presence of the reducing agents such as dl-dithiothreitol (DTT).

Advances in acrylic-alkyd hybrid synthesis and characterization

NASA Astrophysics Data System (ADS)

Dziczkowski, Jamie

2008-10-01

In situ graft acrylic-alkyd hybrid resins were formed by polymerizing acrylic and acrylic-mixed monomers in the presence of alkyds by introduction of a free radical initiator to promote graft formation. Two-dimensional NMR, specifically gradient heteronuclear multiple quantum coherence (gHMQC), was used to clarify specific graft sites of the hybrid materials. Both individual and mixed-monomer systems were produced to determine any individual monomer preferences and to model current acrylic-alkyd systems. Different classes of initiators were used to determine any initiator effects on graft location. The 2D-NMR results confirm grafting at doubly allylic hydrogens located on the fatty acid chains and the polyol segment of the alkyd backbone. The gHMQC spectra show no evidence of grafting across double bonds on either pendant fatty acid groups or THPA unsaturation sites for any of the monomer or mixed monomer systems. It was also determined that choice of initiator has no effect on graft location. In addition, a design of experiments using response surface methodology was utilized to obtain a better understanding of this commercially available class of materials and relate both the chemical and physical properties to one another. A Box-Behnkin design was used, varying the oil length of the alkyd phase, the degree of unsaturation in the polyester backbone, and acrylic to alkyd ratio. Acrylic-alkyd hybrid resins were reduced with an amine/water mixture. Hydrolytic stability was tested and viscoelastic properties were obtained to determine crosslink density. Cured films were prepared and basic coatings properties were evaluated. It was found that the oil length of the alkyd is the most dominant factor for final coatings properties of the resins. Acrylic to alkyd ratio mainly influences the resin properties such as acid number, average molecular weight, and hydrolytic stability. The degree of unsaturation in the alkyd backbone has minimal effects on resin and film performance. Reversible-addition fragmentation polymerization techniques were employed to create a new class of acrylic-alkyd hybrid materials. Medium and long oil alkyds made from the monoglyceride process using soybean oil, glycerol, and phthalic anhydride were modified with a RAFT chain transfer agent. The alkyd macro-RAFT agents were reached by end-capping a medium oil soya-based alkyd with a carboxy-functional trithiocarbonate. The alkyd macro-RAFT agents were then used to create acrylic-alkyd block structures by polymerizing different acrylic monomers, including both acrylates and methacrylates in the presence of the macro-RAFT agent and 2, 2'-azobisisobutyronitrile (AIBN). Co-acrylic segments were reached by complete polymerization of one monomer followed by the addition of a second monomer and additional free radical initiator. The alkyds, macro-RAFT agents and, acrylic-alkyd blocks were characterized by size-exclusion chromatography (SEC), FTIR, and 1H-NMR. Pseudo-first-order kinetics behavior and conversion vs. molecular weight plots show that the RAFT-mediated reaction afforded a more controlled process for the synthesis of acrylated-alkyd materials. Preliminary coatings tests showed that material properties of acrylated-alkyds achieved by RAFT polymerization exhibit good overall coatings properties including adhesion, gloss, hardness, and impact resistance.

Advanced clay nanocomposites based on in situ photopolymerization utilizing novel polymerizable organoclays

NASA Astrophysics Data System (ADS)

Kim, Soon Ki

Polymer nanocomposite technology has had significant impact on material design. With the environmental advantages of photopolymerization, a research has recently focused on producing nanocomposites utilizing inexpensive clay particles based on in situ photopolymerization. In this research, novel polymerizable organoclays and thiol-ene photopolymerization have been utilized to develop advanced photopolymer clay nanocomposites and to overcome several limitations in conventional free radical photopolymers. To this end, factors important in nanocomposite processes such as monomer composition, clay dispersion, and photopolymerization behavior in combination with the evolution of ultimate nanocomposite properties have been investigated. For monomer-organoclay compositions, higher chemical compatibility of components induces enhanced clay exfoliation, resulting in photopolymerization rate increases due to an amplified clay template effect. Additionally, by affecting the stoichiometric ratio between thiol and acrylate double bond in the clay gallery, thiolated organoclays enhance thiol-ene copolymerization with increased final thiol conversion while acrylated organoclays encourage acrylate homopolymerization. In accordance with the reaction behavior, incorporation of thiolated organoclays makes polymer chains more flexible with decreased glass transition temperature due to higher formation of thio-ether linkages while adding acrylated organoclays significantly increases the modulus. Photopolymer nanocomposites also help overcome two major drawbacks in conventional free radical photopolymerization, namely severe polymerization shrinkage and oxygen inhibition during polymerization. With addition of a low level of thiol monomers, the oxygen inhibition in various acrylate systems can be overcome by addition of only 5wt% thiolated organoclay. The same amount of polymerizable organoclay also induces up to 90% decreases in the shrinkage stress for acrylate or thiol-acrylate systems. However, nonreactive clays do not reduce the stress substantially and even decreases the polymerization rate in air. Additionally, the clay morphology and polymerization behavior are closely related with evolution of ultimate nanocomposite performance. Use of polymerizable organoclay significantly improves overall toughness of nanocomposites by increasing either modulus or elongation at break based on the type of polymerizable organoclay, which demonstrates the promise of this technology as a modulation and/or optimization tool for nanocomposite properties.

Stereo-, Temporal and Chemical Control through Photoactivation of Living Radical Polymerization: Synthesis of Block and Gradient Copolymers.

PubMed

Shanmugam, Sivaprakash; Boyer, Cyrille

2015-08-12

Nature has developed efficient polymerization processes, which allow the synthesis of complex macromolecules with a perfect control of tacticity as well as molecular weight, in response to a specific stimulus. In this contribution, we report the synthesis of various stereopolymers by combining a photoactivated living polymerization, named photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) with Lewis acid mediators. We initially investigated the tolerance of two different photoredox catalysts, i.e., Ir(ppy)3 and Ru(bpy)3, in the presence of a Lewis acid, i.e., Y(OTf)3 and Yb(OTf)3, to mediate the polymerization of N,N-dimethyl acrylamide (DMAA). An excellent control of tacticity as well as molecular weight and dispersity was observed when Ir(ppy)3 and Y(OTf)3 were employed in a methanol/toluene mixture, while no polymerization or poor control was observed with Ru(bpy)3. In comparison to a thermal system, a lower amount of Y(OTf)3 was required to achieve good control over the tacticity. Taking advantage of the temporal control inherent in our system, we were able to design complex macromolecular architectures, such as atactic block-isotactic and isotactic-block-atactic polymers in a one-pot polymerization approach. Furthermore, we discovered that we could modulate the degree of tacticity through a chemical stimulus, by varying [DMSO]0/[Y(OTf)3]0 ratio from 0 to 30 during the polymerization. The stereochemical control afforded by the addition of a low amount of DMSO in conjunction with the inherent temporal control enabled the synthesis of stereogradient polymer consisting of five different stereoblocks in one-pot polymerization.

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

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.

Zirconium oxocluster/polymer hybrid nanoparticles prepared by photoactivated miniemulsion copolymerization

NASA Astrophysics Data System (ADS)

Benedetti, Cesare; Flouda, Paraskevi; Antonello, Alice; Rosenauer, Christine; Pérez-Pla, Francisco F.; Landfester, Katharina; Gross, Silvia; Muñoz-Espí, Rafael

2017-09-01

The photoactivated free radical miniemulsion copolymerization of methyl methacrylate (MMA) and the zirconium oxocluster Zr4O2(methacrylate)12 is used as an effective and fast preparation method for polymer/inorganic hybrid nanoparticles. The oxoclusters, covalently anchored to the polymer network, act as metal-organic cross-linkers, thus improving the thermomechanical properties of the resulting hybrid nanoparticles. Benzoin carbonyl organic compounds were used as photoinitiators. The obtained materials are compared in terms of cross-linking, effectiveness of cluster incorporation, and size distribution with the analogous nanoparticles produced by using conventional thermally induced free radical miniemulsion copolymerization. The kinetics of the polymerization process in the absence and in the presence of the oxocluster is also investigated.

Dimensional change in complete dentures fabricated by injection molding and microwave processing.

PubMed

Keenan, Phillip L J; Radford, David R; Clark, Robert K F

2003-01-01

Acrylic resin complete dentures undergo dimensional changes during polymerization. Techniques with injection molding and polymerization and microwave polymerization are reported to reduce these changes and thereby improve clinical fit. These dimensional changes need to be quantified. The purpose of this study was to compare differences in dimensional changes of simulated maxillary complete dentures during polymerization and storage in water after injection molding and conventional polymerization, or microwave polymerization against a control of conventionally packed and polymerized simulated maxillary complete dentures. Forty identical maxillary denture bases were prepared in dental wax with anatomic teeth. They were invested and the wax eliminated from the molds. Ten specimens each were randomly assigned to 1 of 4 groups. Group 1 was compression molded and conventionally polymerized; group 2 was injection molded and conventionally polymerized (Success); group 3 was injection molded and microwave polymerized (Acron MC); and group 4 was injection molded and microwave polymerized (Microbase). Intermolar width and changes in vertical dimension of occlusion, were determined after polymerization and after storage in water for 28 days. Measurements in triplicate were made between points scribed on the second molar teeth with a traveling microscope (accurate to 0.005 mm). Vertical dimension of occlusion was measured between points scribed on the upper and lower members of an articulator by use of an internal micrometer (accurate to 0.05 mm). Data were analyzed by use of a 1-way analysis of variance with Tukey post-hoc contrasts (P <.05). Polymerization contractions (intermolar widths) for each group were: group 1, -0.24%; group 2, -0.27%; group 3, -0.35%; and group 4, -0.37%. The Microbase specimens had greater shrinkage than conventionally polymerized specimens, but there were no significant differences between the groups. All injection methods had less postpolymerization increase in vertical dimension of occlusion (0.63 to 0.41 mm) than the conventional Trevalon control (0.74 mm), but only group 4 was significantly different (P<.004). After storage in water for 28 days, all specimens increased in vertical dimension of occlusion (0.10% to 0.16%) from polymerization techniques, but there were no significant differences between groups. Within the limitations of this study, injection molding resulted in a slightly less increase of vertical dimension of occlusion than conventional polymerization techniques, the difference being significant for Microbase compared with the conventional Trevalon control.

Radical Nature of C-Lignin

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

Berstis, Laura; Elder, Thomas; Crowley, Michael

The recently discovered lignin composed of caffeoyl alcohol monolignols or C-lignin is particularly intriguing given its homogeneous, linear polymeric structure and exclusive benzodioxane linkage between monomers. By virtue of this simplified chemistry, the potential emerges for improved valorization strategies with C-lignin relative to other natural heterogeneous lignins. To better understand caffeoyl alcohol polymers, we characterize the thermodynamics of the radical recombination dimerization reactions forming the benzodioxane linkage and the bond dissociation into radical monolignol products. These properties are also predicted for the cross-coupling of caffeoyl alcohol with the natural monolignols, coniferyl alcohol, sinapyl alcohol, and p-coumaryl alcohol, in anticipation of polymers potentially enabled by genetic modification. The average BDEs for the C-lignin benzodioxanemore » $$\\alpha$$- and β-bonds are 56.5 and 63.4 kcal/mol, respectively, with similar enthalpies for heterodimers. The BDE of the $$\\alpha$$-bond within the benzodioxane linkage is consistently greater than that of the β-bond in all dimers of each stereochemical arrangement, explained by the ability the $$\\alpha$$-carbon radical generated to delocalize onto the adjacent phenyl ring. Relative thermodynamics of the heterodimers demonstrates that the substituents on the phenyl ring directly neighboring the bond coupling the monolignols more strongly impact the dimer bond strengths and product stability, compared to the substituents present on the terminal phenyl ring. Enthalpy comparisons furthermore demonstrate that the erythro stereochemical configurations of the benzodioxane bond are slightly less thermodynamically stable than the threo configurations. The overall differences in strength of bonds and reaction enthalpies between stereoisomers are generally found to be insignificant, supporting that postcoupling rearomatization is under kinetic control. Projecting the lowest-energy stereoisomer internal coordinates to longer polymer C-lignin strands highlights how significantly the stereochemical outcomes in polymerization may impact the macromolecular structure and in turn material and chemical properties. Lastly, through these comparisons of geometry, bond strengths, and reaction enthalpies, we shed light on the distinctive properties of C-lignin's radical recombination and decomposition chemistry, and its potential as a natural lignin solution for biorefinery feedstocks and unique materials science applications.« less

Radical Nature of C-Lignin

DOE PAGES

Berstis, Laura; Elder, Thomas; Crowley, Michael; ...

2016-05-17

The recently discovered lignin composed of caffeoyl alcohol monolignols or C-lignin is particularly intriguing given its homogeneous, linear polymeric structure and exclusive benzodioxane linkage between monomers. By virtue of this simplified chemistry, the potential emerges for improved valorization strategies with C-lignin relative to other natural heterogeneous lignins. To better understand caffeoyl alcohol polymers, we characterize the thermodynamics of the radical recombination dimerization reactions forming the benzodioxane linkage and the bond dissociation into radical monolignol products. These properties are also predicted for the cross-coupling of caffeoyl alcohol with the natural monolignols, coniferyl alcohol, sinapyl alcohol, and p-coumaryl alcohol, in anticipation of polymers potentially enabled by genetic modification. The average BDEs for the C-lignin benzodioxanemore » $$\\alpha$$- and β-bonds are 56.5 and 63.4 kcal/mol, respectively, with similar enthalpies for heterodimers. The BDE of the $$\\alpha$$-bond within the benzodioxane linkage is consistently greater than that of the β-bond in all dimers of each stereochemical arrangement, explained by the ability the $$\\alpha$$-carbon radical generated to delocalize onto the adjacent phenyl ring. Relative thermodynamics of the heterodimers demonstrates that the substituents on the phenyl ring directly neighboring the bond coupling the monolignols more strongly impact the dimer bond strengths and product stability, compared to the substituents present on the terminal phenyl ring. Enthalpy comparisons furthermore demonstrate that the erythro stereochemical configurations of the benzodioxane bond are slightly less thermodynamically stable than the threo configurations. The overall differences in strength of bonds and reaction enthalpies between stereoisomers are generally found to be insignificant, supporting that postcoupling rearomatization is under kinetic control. Projecting the lowest-energy stereoisomer internal coordinates to longer polymer C-lignin strands highlights how significantly the stereochemical outcomes in polymerization may impact the macromolecular structure and in turn material and chemical properties. Lastly, through these comparisons of geometry, bond strengths, and reaction enthalpies, we shed light on the distinctive properties of C-lignin's radical recombination and decomposition chemistry, and its potential as a natural lignin solution for biorefinery feedstocks and unique materials science applications.« less

Investigation of Solution Polymerizations in Microgravity and 1 G

NASA Technical Reports Server (NTRS)

Kennedy, Alvin P.

1998-01-01

The in-situ dielectric spectra for the solution polymerization of polydiacetylene has been successfully measured. The results show a distinct difference between the response for the bulk solution and surface polymerization. It also shows a low frequency peak in the dissipation factor which is present in both the bulk and surface polymerizations. These features may prove to be significant indicators for important polymerization processes. Future studies will investigate the mechanisms responsible for these dielectric responses. This technique will eventually be used to monitor microgravity polymerizations and provide in-situ data on how microgravity affects solution polymerization.

Analysis of beer volatiles by polymeric imidazolium-solid phase microextraction coatings: Synthesis and characterization of polymeric imidazolium ionic liquids.

PubMed

González-Álvarez, Jaime; Blanco-Gomis, Domingo; Arias-Abrodo, Pilar; Pello-Palma, Jairo; Ríos-Lombardía, Nicolás; Busto, Eduardo; Gotor-Fernández, Vicente; Gutiérrez-Álvarez, María Dolores

2013-08-30

Two polymeric ionic liquids, 3-(but-3″-en-1″-yl)-1-[2'-hydroxycyclohexyl]-1H-imidazol-3-ium bis(trifluoromethanesulfonyl)imide (IL-1) and 1-(2'-hydroxycyclohexyl)-3-(4″-vinylbenzyl)-1H-imidazol-3-ium bis(trifluoromethylsulfonyl)imide (IL-2), have been synthesized by a free radical polymerization reaction and used as coatings for solid-phase microextraction (SPME). These new fibers exhibit good film stability, high thermal stability (270-290°C) and long lifetimes, and are used for the extraction of volatile compounds in lemon beer using gas chromatography separation and flame ionization detection. The scanning electron micrographs of the fiber surface revealed a polymeric ionic liquid (PIL) film, which is distributed homogeneously on the fiber. The developed PIL fiber showed good linearity between 50 and 2000μg/L with regression coefficients in the range of 0.996-0.999. The relative standard deviations (RSD) obtained in the peak area were found to vary between 1% and 12%, which assured that adequate repeatability was achieved. The spiked recoveries for three beer samples ranged from 78.4% to 123.6%. Experimental design has been employed in the optimization of extraction factors and robustness assessment. The polymeric IL-1 butenyl fiber showed a greater efficiency compared to the PDMS-DVB (65μm) and CAR-PDMS (75μm) for the extraction of all of the analytes studied. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

Silane–Acrylate Chemistry for Regulating Network Formation in Radical Photopolymerization

PubMed Central

2017-01-01

Photoinitiated silane–ene chemistry has the potential to pave the way toward spatially resolved organosilicon compounds, which might find application in biomedicine, microelectronics, and other advanced fields. Moreover, this approach could serve as a viable alternative to the popular photoinitiated thiol–ene chemistry, which gives access to defined and functional photopolymer networks. A difunctional bis(trimethylsilyl)silane with abstractable hydrogens (DSiH) was successfully synthesized in a simple one-pot procedure. The radical reactivity of DSiH with various homopolymerizable monomers (i.e., (meth)acrylate, vinyl ester, acrylamide) was assessed via 1H NMR spectroscopic studies. DSiH shows good reactivity with acrylates and vinyl esters. The most promising silane–acrylate system was further investigated in cross-linking formulations toward its reactivity (e.g., heat of polymerization, curing time, occurrence of gelation, double-bond conversion) and compared to state-of-the-art thiol–acrylate resins. The storage stability of prepared resin formulations is greatly improved for silane–acrylate systems vs thiol–ene resins. Double-bond conversion at the gel point (DBCgel) and overall DBC were increased, and polymerization-induced shrinkage stress has been significantly reduced with the introduction of silane–acrylate chemistry. Resulting photopolymer networks exhibit a homogeneous network architecture (indicated by a narrow glass transition) that can be tuned by varying silane concentration, and this confirms the postulated regulation of radical network formation. Similar to thiol–acrylate networks, this leads to more flexible photopolymer networks with increased elongation at break and improved impact resistance. Additionally, swelling tests indicate a high gel fraction for silane–acrylate photopolymers. PMID:29033466

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.

Understanding co-polymerization in amyloid formation by direct observation of mixed oligomers† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c7sc00620a Click here for additional data file.

PubMed Central

Young, Lydia M.; Tu, Ling-Hsien; Raleigh, Daniel P.; Ashcroft, Alison E.

2017-01-01

Although amyloid assembly in vitro is commonly investigated using single protein sequences, fibril formation in vivo can be more heterogeneous, involving co-assembly of proteins of different length, sequence and/or post-translational modifications. Emerging evidence suggests that co-polymerization can alter the rate and/or mechanism of aggregation and can contribute to pathogenicity. Electrospray ionization-ion mobility spectrometry-mass spectrometry (ESI-IMS-MS) is uniquely suited to the study of these heterogeneous ensembles. Here, ESI-IMS-MS combined with analysis of fibrillation rates using thioflavin T (ThT) fluorescence, is used to track the course of aggregation of variants of islet-amyloid polypeptide (IAPP) in isolation and in pairwise mixtures. We identify a sub-population of extended monomers as the key precursors of amyloid assembly, and reveal that the fastest aggregating sequence in peptide mixtures determines the lag time of fibrillation, despite being unable to cross-seed polymerization. The results demonstrate that co-polymerization of IAPP sequences radically alters the rate of amyloid assembly by altering the conformational properties of the mixed oligomers that form. PMID:28970890

Bis(1,3-di-tert-butylimidazolin-2-iminato) titanium complexes as effective catalysts for the monodisperse polymerization of propylene.

PubMed

Sharma, Manab; Yameen, Haneen Simaan; Tumanskii, Boris; Filimon, Sabina-Alexandra; Tamm, Matthias; Eisen, Moris S

2012-10-17

The use of bis(1,3-di-tert-butylimidazolin-2-iminato) titanium dichloride (1) and dimethyl (2) complexes in the polymerization of propylene is presented. The complexes were activated using different amounts of methylalumoxane (MAO), giving in each case a very active catalytic mixture and producing polymers with a narrow molecular weight distribution (polydispersity = 1.10). The use of the cocatalyst triphenylcarbenium (trityl) tetra(pentafluorophenyl)borate totally inhibits the reaction, producing the corresponding bis(1,3-di-tert-butylimidazolin-2-iminato) titanium(III) methyl complex, the trityl radical ((•)CPh(3)), the anionic MeB(C(6)F(5))(4)(-), B(C(6)F(5))(3), and the bis(1,3-di-tert-butylimidazolin-2-iminato) titanium(IV) dimethyl·B(C(6)F(5))(3) complex. The use of a combination of physical methods such as NMR, ESR-C(60), and MALDI-TOF analyses enabled us to propose a plausible mechanism for the polymerization of propylene, presenting that the polymerization is mainly carried out in a living fashion. In addition, we present a slow equilibrium toward a small amount of a dormant species responsible for 2,1-misinsertions and chain transfer processes.

Fast and Selective Preconcentration of Europium from Wastewater and Coal Soil by Graphene Oxide/Silane@Fe3O4 Dendritic Nanostructure.

PubMed

Patra, Santanu; Roy, Ekta; Madhuri, Rashmi; Sharma, Prashant K

2015-05-19

In this study, nanocomposite of graphene oxide and silane modified magnetic nanoparticles (silane@Fe3O4) were synthesized in a form of dendritic structure. For this, silane@Fe3O4 nanoparticle gets sandwiched between two layers of graphene oxide by chemical synthesis route. The synthesized dendritic structure was used as a monomer for synthesis of europium ion imprinted polymer. The synthesis of imprinted polymer was contemplated onto the surface of the vinyl group modified silica fiber by activated generated free radical atom-transfer radical polymerization, that is, AGET-ATRP technique. The synthesized dendritic monomer was characterized by XRD, FT-IR, VSM, FE-SEM, and TEM analyses. The imprinted polymer modified silica fiber was first validated in the aqueous and blood samples for successful extraction and detection of europium ion with limit of detection = 0.050 pg mL(-1) (signal/noise = 3). The imprinted polymer modified silica fiber was also used for preconcentration and separation of europium metal ion from various soil samples of coal mine areas. However, the same silica fiber was also used for wastewater treatment and shows 100% performance for europium removal. The findings herein suggested that dendritic nanocomposite could be potentially used as a highly effective material for the enrichment and preconcentration of europium or other trivalent lanthanides/actinides in nuclear waste management.

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

Sakurada, I.; Okada, T.; Hutakeyama, S.

Experiments on radioinduced graft copolymerization of binary mixtures such as butadiene -- styrene, butadiene-acrylonitrile, styrene-- acrylonitrile and some other systems onto cellulose and PVA (polyvinyl alcohol) fibers were carried out with the use of methanol as a solvent. A very marked maximum of graft was observed in every case at a certain composition of the comonomer mixture. It seemed that such a marked maximum was closely connected with popcorn polymerization for the case of butadiene-- styrene, but popcorn polymerization was not a necessary condition for the appearance of the maximum. Only a combined effect of swelling of the gel, formationmore » of radicals in the gel, homocopolymerization, and some other unknown factors is considered likely to lead to a very high degree of grafting. (auth)« less

Design and Synthesis of Network-Forming Triblock Copolymers Using Tapered Block Interfaces

PubMed Central

Kuan, Wei-Fan; Roy, Raghunath; Rong, Lixia; Hsiao, Benjamin S.; Epps, Thomas H.

2012-01-01

We report a strategy for generating novel dual-tapered poly(isoprene-b-isoprene/styrene-b-styrene-b-styrene/methyl methacrylate-b-methyl methacrylate) [P(I-IS-S-SM-M)] triblock copolymers that combines anionic polymerization, atom transfer radical polymerization (ATRP), and Huisgen 1,3-dipolar cycloaddition click chemistry. The tapered interfaces between blocks were synthesized via a semi-batch feed using programmable syringe pumps. This strategy allows us to manipulate the transition region between copolymer blocks in triblock copolymers providing control over the interfacial interactions in our nanoscale phase-separated materials independent of molecular weight and block constituents. Additionally, we show the ability to retain a desirous and complex multiply-continuous network structure (alternating gyroid) in our dual-tapered triblock material. PMID:23066522

Polystyrene-based Hollow Microsphere Synthesized by γ-ray Irradiation-assisted Polymerization and Self-Assembly and Its Application in Detection of Ionizing Radiation

NASA Astrophysics Data System (ADS)

Fan, Wenhui; Li, Qing; Hu, Liang; Yan, Siqi; Wen, Wanxin; Chai, Zhifang; Liu, Hanzhou

2017-01-01

To simply and multitudinously synthesize hollow microspheres in a pure system is important for relevant research and application. Here, a simple and novel one-pot synthetic strategy to prepare polystyrene (PS) hollow microspheres via irradiation-assisted free-radical polymerizing and self-assembly (IFPS) approach under γ-ray irradiation with no additives introduced into the system is presented. And PS/2,5-Diphenyloxazole (PPO) fluorescent microspheres have been prepared successfully by IFPS reaction, which can be used as scintillators for the detection of ionizing radiation. A linear relationship between emitted luminescence and dose-activity in water is obtained, which suggests that composite microspheres could be used as liquid scintillation in specific environment.

Effect of polymerization technique and glass fiber addition on the surface roughness and hardness of PMMA denture base material.

PubMed

Gad, Mohammed M; Rahoma, Ahmed; Al-Thobity, Ahmad M

2018-06-20

The current study evaluated the effects of autoclave polymerization both with and without glass fiber (GF) reinforcement on the surface roughness and hardness of acrylic denture base material. Ninety disc specimens (30×2.5 mm) were prepared from Vertex resin and divided according to polymerization techniques into a water bath, short and long autoclave polymerization groups. Tested groups were divided into three subgroups according to the GF concentration (0, 2.5, and 5 wt%). Profilometer and Vickers hardness tests were performed to measure surface roughness and hardness. ANOVA and Tukey-Kramer multiple comparison tests analyzed the results, and p≤0.05 was considered statistically significant. Autoclave polymerization significantly decreased the surface roughness and increased the hardness of acrylic resin without GF reinforcement (p<0.05). However, 5 wt% GF addition significantly increased surface roughness and decreased hardness of the autoclave polymerized denture base resin (p<0.05). Surface properties of Polymethyl methacrylate (PMMA) denture base material improved with autoclave polymerization and negatively affected with GFs addition.

Photoredox Catalysis for the Generation of Carbon Centered Radicals.

PubMed

Goddard, Jean-Philippe; Ollivier, Cyril; Fensterbank, Louis

2016-09-20

Radical chemistry has witnessed over the last decades important advances that have positioned it as a methodology of choice in synthetic chemistry. A number of great attributes such as specific reactivities, the knowledge of the kinetics of most elementary processes, the functional group tolerance, and the possibility to operate cascade sequences are clearly responsible for this craze. Nevertheless, at the end of the last century, radical chemistry appeared plagued by several hurdles to overcome such as the use of environmentally problematic mediators or the impossibility of scale up. While the concept of photocatalysis was firmly established in the coordination chemistry community, its diffusion in organic synthetic chemistry remained sporadic for decades until the end of the 2000s with the breakthrough merging of organocatalysis and photocatalysis by the MacMillan group and contemporary reports by the groups of Yoon and Stephenson. Since then, photoredox catalysis has enjoyed particularly active and intense developments. It is now the topic of a still increasing number of publications featuring various applications from asymmetric synthesis, total synthesis of natural products, and polymerization to process (flow) chemistry. In this Account, we survey our own efforts in this domain, focusing on the elaboration of new photocatalytic pathways that could lead to the efficient generation of C-centered functionalized alkyl and aryl radicals. Both reductive and oxidative manifolds are accessible through photoredox catalysis, which has guided us along these lines in our projects. Thus, we studied the photocatalytic reduction of onium salts such as sulfoniums and iodoniums for the production of the elusive aryl radical intermediates. Progressing to more relevant chemistry for synthesis, we examined the cleavage of C-O and the C-Br bonds for the generation of alkyl C-centered radicals. Activated epoxides could serve as valuable substrates of a photocatalyzed variant of the Nugent-RajanBabu-Gansäuer homolytic cleavage of epoxides. Using imidazole based carbamates, we could also devise the first photocatalyzed Barton-McCombie deoxygenation reaction. Finally, bromophenylacetate can be reduced using the [Au2(μ-dppm)2]Cl2 photocatalyst under UVA or visible-light. This was used for the initiation of the controlled atom transfer radical polymerization of methacrylates and acrylates in solution or laminate. Our next endeavors concerned the photocatalyzed oxidation of stabilized carbanions such as enolates of 1,3-dicarbonyl substrates, trifluoroborates, and more extensively bis-catecholato silicates. Because of their low oxidation potentials, the later have proved to be exquisite sources of radical entities, which can be engaged in diverse intermolecular reactions such as vinylation, alkynylation, and conjugate additions. The bis-catecholato silicates were also shown to behave as excellent partners of dual photoredox-nickel catalysis leading in an expeditious manner to libraries of cross coupling products.

Technique for the polymerization of monomers for PPQ/graphite fiber composites

NASA Technical Reports Server (NTRS)

Serafini, T. T.; Delvigs, P.; Vannucci, R. D.

1973-01-01

Impregnation of fiber prior to appreciable polymerization completely eliminates impregnation problems encountered with use of high viscosity high molecular weight polyphenylquinoxalines (PPQ) solutions. Major part of polymerization of reactant mixture is conducted on fiber during solvent removal and final curing stages.

Two-Photon Polymerization of Defects in Photonic Crystals

DTIC Science & Technology

2006-01-01

technique employs two-photon polymerization (TPP) (for description, see Section 2.2) to fabricate high-resolution 3D embedded polymer features within... polymer , and therefore does not influence the polymerization . The image contrast is from the different reflectivities of the interfaces in the system due...Spectroscopy also confirmed for the first time the successful polymerization of a uniform, dense polymer feature throughout the thickness of the

Quantification of OH and HO2 radicals during the low-temperature oxidation of hydrocarbons by Fluorescence Assay by Gas Expansion technique

PubMed Central

Blocquet, Marion; Schoemaecker, Coralie; Amedro, Damien; Herbinet, Olivier; Battin-Leclerc, Frédérique; Fittschen, Christa

2013-01-01

•OH and •HO2 radicals are known to be the key species in the development of ignition. A direct measurement of these radicals under low-temperature oxidation conditions (T = 550–1,000 K) has been achieved by coupling a technique named fluorescence assay by gas expansion, an experimental technique designed for the quantification of these radicals in the free atmosphere, to a jet-stirred reactor, an experimental device designed for the study of low-temperature combustion chemistry. Calibration allows conversion of relative fluorescence signals to absolute mole fractions. Such radical mole fraction profiles will serve as a benchmark for testing chemical models developed to improve the understanding of combustion processes. PMID:24277836

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

Nitroxide-mediated radical ring-opening copolymerization: chain-end investigation and block copolymer synthesis.

PubMed

Delplace, Vianney; Harrisson, Simon; Tardy, Antoine; Gigmes, Didier; Guillaneuf, Yohann; Nicolas, Julien

2014-02-01

Well-defined, degradable copolymers are successfully prepared by nitroxide-mediated radical ring opening polymerization (NMrROP) of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) or methyl methacrylate (MMA), a small amount of acrylonitrile (AN) and cyclic ketene acetals (CKAs) of different structures. Phosphorous nuclear magnetic resonance allows in-depth chain-end characterization and gives crucial insights into the nature of the copoly-mer terminal sequences and the living chain fractions. By using a small library of P(OEGMA-co-AN-co-CKA) and P(MMA-co-AN-co-CKA) as macroinitiators, chain extensions with styrene are performed to furnish (amphiphilic) block copolymers comprising a degradable segment. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Functional lignocellulosic materials prepared by ATRP from a wood scaffold.

PubMed

Cabane, Etienne; Keplinger, Tobias; Künniger, Tina; Merk, Vivian; Burgert, Ingo

2016-08-10

Wood, a natural and abundant source of organic polymers, has been used as a scaffold to develop novel wood-polymer hybrid materials. Through a two-step surface-initiated Atom Transfer Radical Polymerization (ATRP), the porous wood structure can be effectively modified with polymer chains of various nature. In the present study, polystyrene and poly(N-isopropylacrylamide) were used. As shown with various characterization techniques including confocal Raman microscopy, FTIR, and SEM/EDX, the native wood ultrastructure and features are retained and the polymer chains can be introduced deep within the wood, i.e. inside the wood cell walls. The physical properties of the new materials have been studied, and results indicate that the insertion of polymer chains inside the wood cell wall alters the intrinsic properties of wood to yield a hybrid composite material with new functionalities. This approach to the functionalization of wood could lead to the fabrication of a new class of interesting functional materials and promote innovative utilizations of the renewable resource wood.

A green approach to prepare silver nanoparticles loaded gum acacia/poly(acrylate) hydrogels.

PubMed

Bajpai, S K; Kumari, Mamta

2015-09-01

In this work, gum acacia (GA)/poly(sodium acrylate) semi-interpenetrating polymer networks (Semi-IPN) have been fabricated via free radical initiated aqueous polymerization of monomer sodium acrylate (SA) in the presence of dissolved Gum acacia (GA), using N,N'-methylenebisacrylamide (MB) as cross-linker and potassium persulphate (KPS) as initiator. The semi-IPNs, synthesized, were characterized by various techniques such as X-ray diffraction (XRD), thermo gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The dynamic water uptake behavior of semi-IPNs was investigated and the data were interpreted by various kinetic models. The equilibrium swelling data were used to evaluate various network parameters. The semi-IPNs were used as template for the in situ preparation of silver nanoparticles using extract of Syzygium aromaticum (clove). The formation of silver nanoparticles was confirmed by surface plasmon resonance (SPR), XRD and transmission electron microscopy (TEM). Finally, the antibacterial activity of GA/poly(SA)/silver nanocomposites was tested against E. coli. Copyright © 2015 Elsevier B.V. All rights reserved.

Green synthesis of tea Ag nanocomposite hydrogels via mint leaf extraction for effective antibacterial activity.

PubMed

Jayaramudu, Tippabattini; Varaprasad, Kokkarachedu; Raghavendra, Gownolla Malegowd; Sadiku, E R; Mohana Raju, Konduru; Amalraj, John

2017-10-01

In this report, we investigated the swelling behavior and antibacterial property of nanosilver composite hydrogels made from tea with polyacrylamide via a free-radical polymerization and green process technique. This is probably for the first time; tea-based nano silver composite hydrogels were developed. The composite hydrogels comprise embedded nano silver particles in the tea hydrogel matrix via a green process with mint leaf extract. The size of the nano silver particles in the hydrogel matrix was found to be < 10 nm. The nano silver composite hydrogels formed and their blank hydrogels from the mint leaf were characterized by using ultraviolet-visible spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, transmission electron microscopy, thermogravimetric analysis and X-ray diffraction studies. The nano silver composite hydrogels developed exhibit eminent antibacterial activity against Escherichia coli and Staphylococcus aureus. This clearly indicates that the nano silver composite hydrogels are potential candidates for antimicrobial applications.

Efficient synthetic access to thermo-responsive core/shell nanoparticles

NASA Astrophysics Data System (ADS)

Dine, Enaam Jamal Al; Ferjaoui, Zied; Roques-Carmes, Thibault; Schjen, Aleksandra; Meftah, Abdelaziz; Hamieh, Tayssir; Toufaily, Joumana; Schneider, Raphaël; Gaffet, Eric; Alem, Halima

2017-03-01

Core/shell nanostructures based on silica, fluorescent ZnO quantum dots (QDs) and superparamagnetic Fe3O4 nanoparticles (NPs) were prepared and fully characterized by the combination of different techniques and the physical properties of the nanostructures were studied. We demonstrate the efficiency of the atom transfer radical polymerization with activators regenerated by electron transfer process to graft (co-)polymers of different structures and polarity at the surface of metal oxide NPs. The influence of the polymer chain configuration on the optical properties of the ZnO/polymer core/shell QDs was enlightened. Concerning the magnetic properties of the Fe3O4/polymer nanostructures, only the amount of the grafted polymer plays a role on the saturation magnetization of the NPs and no influence of the aggregation was evidenced. The simple and fast process described in this work is efficient for the grafting of copolymers from surfaces and the derived NPs display the combination of the physical properties of the core and the macromolecular behavior of the shell.

Study the friction behaviour of poly[2-(dimethylamino)ethyl methacrylate] brush with AFM probes in contact mechanics

NASA Astrophysics Data System (ADS)

Raftari, Maryam; Zhang, Zhenyu; Leggett, Graham J.; Geoghegan, Mark

2011-10-01

We have studied the frictional behaviour of grafted poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) films using friction force microscopy (FFM). The films were prepared on native oxide-terminated silicon substrates using the technique of atom transfer radical polymerization (ATRP). We show that single asperity contact mechanics (Johnson-Kendall-Roberts(JKR) and Derjaguin-Muller-Toporov(DMT)) as well as a linear (Amontons) relation between applied load and frictional load depending on the pH of the FFM probe. Measurements were made using functionalized and unfunctionalized silicon nitride triangular probes. Functionalized probes included gold-coated probes, and ones coated with a self-assembled monolayer of dodecanethiol (DDT). The frictional behaviour between PDMAEMA and all tips immersed in pH from 3 to 11 are corresponded to the DMT or JKR model and are linear in pH=1, 2, and 12. These results show that contact mechanics of polyelectrolytes in water is complex and strongly dependent on the environmental pH.

Frictional properties of the end-grafted polymer layer in presence of salt solution

NASA Astrophysics Data System (ADS)

Raftari, Maryam; Zhang, Zhenyu; Leggett, Graham J.; Geoghegan, Mark

2012-02-01

We have studied the frictional behaviour of grafted poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) films using friction force microscopy (FFM). The films were prepared on native oxide-terminated silicon substrates using the technique of atom transfer radical polymerization (ATRP). These brushes had constant grafting density (1.18 nm2), and of a thickness of ˜66 nm, as measured by ellipsometry. We show that single asperity contact mechanics (Johnson-Kendall-Roberts (JKR) and Derjaguin-M"uller-Toporov (DMT) models) as well as a linear (Amontons) relation between applied load and frictional load all apply to these systems depending on the concentration of salt and the nature of the FFM probe. Measurements were made using gold-coating and polymer functionalized silicon nitride triangular probes. Polymer functionalized probe included growth the PDMAEMA with same method on tips. The frictional behaviour are investigated between PDMAEMA and gold coated and PDMAEMA tips immersed in different concentrations of KCl, KBr and KI.

Efficient synthetic access to thermo-responsive core/shell nanoparticles.

PubMed

Dine, Enaam Jamal Al; Ferjaoui, Zied; Roques-Carmes, Thibault; Schjen, Aleksandra; Meftah, Abdelaziz; Hamieh, Tayssir; Toufaily, Joumana; Schneider, Raphaël; Gaffet, Eric; Alem, Halima

2017-03-24

Core/shell nanostructures based on silica, fluorescent ZnO quantum dots (QDs) and superparamagnetic Fe 3 O 4 nanoparticles (NPs) were prepared and fully characterized by the combination of different techniques and the physical properties of the nanostructures were studied. We demonstrate the efficiency of the atom transfer radical polymerization with activators regenerated by electron transfer process to graft (co-)polymers of different structures and polarity at the surface of metal oxide NPs. The influence of the polymer chain configuration on the optical properties of the ZnO/polymer core/shell QDs was enlightened. Concerning the magnetic properties of the Fe 3 O 4 /polymer nanostructures, only the amount of the grafted polymer plays a role on the saturation magnetization of the NPs and no influence of the aggregation was evidenced. The simple and fast process described in this work is efficient for the grafting of copolymers from surfaces and the derived NPs display the combination of the physical properties of the core and the macromolecular behavior of the shell.

Functional lignocellulosic materials prepared by ATRP from a wood scaffold

PubMed Central

Cabane, Etienne; Keplinger, Tobias; Künniger, Tina; Merk, Vivian; Burgert, Ingo

2016-01-01

Wood, a natural and abundant source of organic polymers, has been used as a scaffold to develop novel wood-polymer hybrid materials. Through a two-step surface-initiated Atom Transfer Radical Polymerization (ATRP), the porous wood structure can be effectively modified with polymer chains of various nature. In the present study, polystyrene and poly(N-isopropylacrylamide) were used. As shown with various characterization techniques including confocal Raman microscopy, FTIR, and SEM/EDX, the native wood ultrastructure and features are retained and the polymer chains can be introduced deep within the wood, i.e. inside the wood cell walls. The physical properties of the new materials have been studied, and results indicate that the insertion of polymer chains inside the wood cell wall alters the intrinsic properties of wood to yield a hybrid composite material with new functionalities. This approach to the functionalization of wood could lead to the fabrication of a new class of interesting functional materials and promote innovative utilizations of the renewable resource wood. PMID:27506369

Dual signal amplification of surface plasmon resonance imaging for sensitive immunoassay of tumor marker.

PubMed

Hu, Weihua; Chen, Hongming; Shi, Zhuanzhuan; Yu, Ling

2014-05-15

Surface plasmon resonance imaging (SPRi) is an intriguing technique for immunoassay with the inherent advantages of being high throughput, real time, and label free, but its sensitivity needs essential improvement for practical applications. Here, we report a dual signal amplification strategy using functional gold nanoparticles (AuNPs) followed by on-chip atom transfer radical polymerization (ATRP) for sensitive SPRi immunoassay of tumor biomarker in human serum. The AuNPs are grafted with an initiator of ATRP as well as a recognition antibody, where the antibody directs the specific binding of functional AuNPs onto the SPRi sensing surface to form immunocomplexes for first signal amplification and the initiator allows for on-chip ATRP of 2-hydroxyethyl methacrylate (HEMA) from the AuNPs to further enhance the SPRi signal. High sensitivity and broad dynamic range are achieved with this dual signal amplification strategy for detection of a model tumor marker, α-fetoprotein (AFP), in 10% human serum. Copyright © 2014 Elsevier Inc. All rights reserved.

Research on the effect of coverage rate on the surface quality in laser direct writing process

NASA Astrophysics Data System (ADS)

Pan, Xuetao; Tu, Dawei

2017-07-01

Direct writing technique is usually used in femtosecond laser two-photon micromachining. The size of the scanning step is an important factor affecting the surface quality and machining efficiency of micro devices. According to the mechanism of two-photon polymerization, combining the distribution function of light intensity and the free radical concentration theory, we establish the mathematical model of coverage of solidification unit, then analyze the effect of coverage on the machining quality and efficiency. Using the principle of exposure equivalence, we also obtained the analytic expressions of the relationship among the surface quality characteristic parameters of microdevices and the scanning step, and carried out the numerical simulation and experiment. The results show that the scanning step has little influence on the surface quality of the line when it is much smaller than the size of the solidification unit. However, with increasing scanning step, the smoothness of line surface is reduced rapidly, and the surface quality becomes much worse.

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.

Evaluation of the color stability of two techniques for reproducing artificial irides after microwave polymerization

PubMed Central

GOIATO, Marcelo Coelho; dos SANTOS, Daniela Micheline; MORENO, Amália; GENNARI-FILHO, Humberto; PELLIZZER, Eduardo Piza

2011-01-01

The use of ocular prostheses for ophthalmic patients aims to rebuild facial aesthetics and provide an artificial substitute to the visual organ. Natural intemperate conditions promote discoloration of artificial irides and many studies have attempted to produce irides with greater chromatic paint durability using different paint materials. Objectives The present study evaluated the color stability of artificial irides obtained with two techniques (oil painting and digital image) and submitted to microwave polymerization. Material and Methods Forty samples were fabricated simulating ocular prostheses. Each sample was constituted by one disc of acrylic resin N1 and one disc of colorless acrylic resin with the iris interposed between the discs. The irides in brown and blue color were obtained by oil painting or digital image. The color stability was determined by a reflection spectrophotometer and measurements were taken before and after microwave polymerization. Statistical analysis of the techniques for reproducing artificial irides was performed by applying the normal data distribution test followed by 2-way ANOVA and Tukey HSD test (α=.05). Results Chromatic alterations occurred in all specimens and statistically significant differences were observed between the oil-painted samples and those obtained by digital imaging. There was no statistical difference between the brown and blue colors. Independently of technique, all samples suffered color alterations after microwave polymerization. Conclusion The digital imaging technique for reproducing irides presented better color stability after microwave polymerization. PMID:21625733

Radical Polymerization of Vinyl Acetate and Methyl Methacrylate Using Organochromium Initiators Complexed with Macrocyclic Polyamines

DTIC Science & Technology

1994-06-30

conversion, the increase was faster than at later stages. and therefore the steric strain enfosced by the 5gn backone dpdson Th efficiency of initation...BPOJ),- 0.25M. Cr(OAc)2jDPO, THF. 200CC IVAclo - SMK [Cr2io - [DPOJ~i 0.25M. (UI - (Cr2+’Jo (LIgl - (Cr2൒ 0 _ In the absence of any liganda, a

An efficient and reusable “hairy” particle acid catalyst for the synthesis of 5-hydroxymethylfurfural from dehydration of fructose in water

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

Tian, Chengcheng; Bao, Chunhui; Binder, Andrew

We employed poly(4-styrenesulfonic acid) brush-grafted silica particles, synthesized by surface-initiated atom transfer radical polymerization, as a reusable acid catalyst for dehydration of fructose to 5-hydroxymethylfurfural (HMF) in water. Furthermore, the particles exhibited a high activity with the HMF yield of up to 31%, in contrast to 26% from the corresponding free homopolymer catalyst.

Improved hybrid solar cells via in situ UV-polymerization.

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

Tepavcevic, S.; Darling, S. B.; Dimitrijevic, N. M.

One approach for making inexpensive inorganic-organic hybrid photovoltaic (PV) cells is to fill highly ordered TiO{sub 2} nanotube (NT) arrays with solid organic hole conductors such as conjugated polymers. Here, a new in situ UV polymerization method for growing polythiophene (UV-PT) inside TiO{sub 2} NTs is presented and compared to the conventional approach of infiltrating NTs with pre-synthesized polymer. A nanotubular TiO{sub 2} substrate is immersed in a 2,5-diiodothiophene (DIT) monomer precursor solution and then irradiated with UV light. The selective UV photodissociation of the C-I bond produces monomer radicals with intact {pi}-ring structure that further produce longer oligothiophene/PT molecules.more » Complete photoluminescence quenching upon UV irradiation suggests coupling between radicals created from DIT and at the TiO{sub 2} surface via a charge transfer complex. Coupling with the TiO{sub 2} surface improves UV-PT crystallinity and {pi}-{pi} stacking; flat photocurrent values show that charge recombination during hole transport through the polymer is negligible. A non-ideal, backside-illuminated setup under illumination of 620-nm light yields a photocurrent density of {approx} 5 {micro}A cm{sup -2} - surprisingly much stronger than with comparable devices fabricated with polymer synthesized ex situ. Since in this backside architecture setup we illuminate the cell through the Ag top electrode, there is a possibility for Ag plasmon-enhanced solar energy conversion. By using this simple in situ UV polymerization method that couples the conjugated polymer to the TiO{sub 2} surface, the absorption of sunlight can be improved and the charge carrier mobility of the photoactive layer can be enhanced.« less

UV-initiated template copolymerization of AM and MAPTAC: Microblock structure, copolymerization mechanism, and flocculation performance.

PubMed

Li, Xiang; Zheng, Huaili; Gao, Baoyu; Sun, Yongjun; Liu, Bingzhi; Zhao, Chuanliang

2017-01-01

Flocculation as the core technology of sludge pretreatment can improve the dewatering performance of sludge that enables to reduce the cost of sludge transportation and the subsequent disposal costs. Therefore, synthesis of high-efficiency and economic flocculant is remarkably desired in this field. This study presents a cationic polyacrylamide (CPAM) flocculant with microblock structure synthesized through ultraviolet (UV)-initiated template copolymerization by using acrylamide (AM) and methacrylamido propyl trimethyl ammonium chloride (MAPTAC) as monomers, sodium polyacrylate (PAAS) as template, and 2,2'-azobis [2-(2-imidazolin-2-yl) propane] dihydrochloride (VA-044) as photoinitiator. The microblock structure of the CPAM was observed through nuclear magnetic resonance ( 1 H NMR and 13 C NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) analyses. Furthermore, thermogravimetric/differential scanning calorimetry (TG/DSC) analysis was used to evaluate its thermal decomposition property. The copolymerization mechanism was investigated through the determination of the binding constant M K and study on polymerization kinetics. Results showed that the copolymerization was conducted in accordance with the I (ZIP) template polymerization mechanism, and revealed the coexistence of bimolecular termination free-radical reaction and mono-radical termination in the polymerization process. Results of sludge dewatering tests indicated the superior flocculation performance of microblock flocculant than random distributed CPAM. The residual turbidity, filter cake moisture content, and specific resistance to filtration reached 9.37 NTU, 68.01%, and 6.24 (10 12  m kg -1 ), respectively, at 40 mg L -1 of template poly(AM-MAPTAC) and pH 6.0. Furthermore, all flocculant except commercial CPAM showed a wide scope of pH application. Copyright © 2016 Elsevier Ltd. All rights reserved.

Investigating Biochemical and Developmental Dependencies of Lignification with a Click-Compatible Monolignol Analog in Arabidopsis thaliana Stems

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

Pandey, Jyotsna L.; Kiemle, Sarah N.; Richard, Tom L.

Lignin is a key structural component of plant cell walls that provides rigidity, strength, and resistance against microbial attacks. This hydrophobic polymer also serves a crucial role in water transport. Despite its abundance and essential functions, several aspects of lignin biosynthesis and deposition remain cryptic. Lignin precursors are known to be synthesized in the cytoplasm by complex biosynthetic pathways, after which they are transported to the apoplastic space, where they are polymerized via free radical coupling reactions into polymeric lignin. However, the lignin deposition process and the factors controlling it are unclear. In this study, the biochemical and developmental dependenciesmore » of lignification were investigated using a click-compatible monolignol analog, 3-O-propargylcaffeyl alcohol (3-OPC), which can incorporate into both in vitro polymerized lignin and Arabidopsis thaliana tissues. Fluorescence labeling of 3-OPC using click chemistry followed by confocal fluorescence microscopy enabled the detection and imaging of 3-OPC incorporation patterns. These patterns were consistent with endogenous lignification observed in different developmental stages of Arabidopsis stems. However, the concentration of supplied monolignols influenced where lignification occurred at the subcellular level, with low concentrations being deposited in cell corners and middle lamellae and high concentrations also being deposited in secondary walls. Experimental inhibition of multiple lignification factors confirmed that 3-OPC incorporation proceeds via a free radical coupling mechanism involving peroxidases/laccases and reactive oxygen species (ROS). Finally, the presence of peroxide-producing enzymes determined which cell walls lignified: adding exogenous peroxide and peroxidase caused cells that do not naturally lignify in Arabidopsis stems to lignify. In conclusion, 3-OPC accurately mimics natural lignification patterns in different developmental stages of Arabidopsis stems and allows for the dissection of key biochemical and enzymatic factors controlling lignification.« less

Investigating Biochemical and Developmental Dependencies of Lignification with a Click-Compatible Monolignol Analog in Arabidopsis thaliana Stems

PubMed Central

Pandey, Jyotsna L.; Kiemle, Sarah N.; Richard, Tom L.; Zhu, Yimin; Cosgrove, Daniel J.; Anderson, Charles T.

2016-01-01

Lignin is a key structural component of plant cell walls that provides rigidity, strength, and resistance against microbial attacks. This hydrophobic polymer also serves a crucial role in water transport. Despite its abundance and essential functions, several aspects of lignin biosynthesis and deposition remain cryptic. Lignin precursors are known to be synthesized in the cytoplasm by complex biosynthetic pathways, after which they are transported to the apoplastic space, where they are polymerized via free radical coupling reactions into polymeric lignin. However, the lignin deposition process and the factors controlling it are unclear. In this study, the biochemical and developmental dependencies of lignification were investigated using a click-compatible monolignol analog, 3-O-propargylcaffeyl alcohol (3-OPC), which can incorporate into both in vitro polymerized lignin and Arabidopsis thaliana tissues. Fluorescence labeling of 3-OPC using click chemistry followed by confocal fluorescence microscopy enabled the detection and imaging of 3-OPC incorporation patterns. These patterns were consistent with endogenous lignification observed in different developmental stages of Arabidopsis stems. However, the concentration of supplied monolignols influenced where lignification occurred at the subcellular level, with low concentrations being deposited in cell corners and middle lamellae and high concentrations also being deposited in secondary walls. Experimental inhibition of multiple lignification factors confirmed that 3-OPC incorporation proceeds via a free radical coupling mechanism involving peroxidases/laccases and reactive oxygen species (ROS). Finally, the presence of peroxide-producing enzymes determined which cell walls lignified: adding exogenous peroxide and peroxidase caused cells that do not naturally lignify in Arabidopsis stems to lignify. In summary, 3-OPC accurately mimics natural lignification patterns in different developmental stages of Arabidopsis stems and allows for the dissection of key biochemical and enzymatic factors controlling lignification. PMID:27630649

Investigating Biochemical and Developmental Dependencies of Lignification with a Click-Compatible Monolignol Analog in Arabidopsis thaliana Stems

DOE PAGES

Pandey, Jyotsna L.; Kiemle, Sarah N.; Richard, Tom L.; ...

2016-08-31

Lignin is a key structural component of plant cell walls that provides rigidity, strength, and resistance against microbial attacks. This hydrophobic polymer also serves a crucial role in water transport. Despite its abundance and essential functions, several aspects of lignin biosynthesis and deposition remain cryptic. Lignin precursors are known to be synthesized in the cytoplasm by complex biosynthetic pathways, after which they are transported to the apoplastic space, where they are polymerized via free radical coupling reactions into polymeric lignin. However, the lignin deposition process and the factors controlling it are unclear. In this study, the biochemical and developmental dependenciesmore » of lignification were investigated using a click-compatible monolignol analog, 3-O-propargylcaffeyl alcohol (3-OPC), which can incorporate into both in vitro polymerized lignin and Arabidopsis thaliana tissues. Fluorescence labeling of 3-OPC using click chemistry followed by confocal fluorescence microscopy enabled the detection and imaging of 3-OPC incorporation patterns. These patterns were consistent with endogenous lignification observed in different developmental stages of Arabidopsis stems. However, the concentration of supplied monolignols influenced where lignification occurred at the subcellular level, with low concentrations being deposited in cell corners and middle lamellae and high concentrations also being deposited in secondary walls. Experimental inhibition of multiple lignification factors confirmed that 3-OPC incorporation proceeds via a free radical coupling mechanism involving peroxidases/laccases and reactive oxygen species (ROS). Finally, the presence of peroxide-producing enzymes determined which cell walls lignified: adding exogenous peroxide and peroxidase caused cells that do not naturally lignify in Arabidopsis stems to lignify. In conclusion, 3-OPC accurately mimics natural lignification patterns in different developmental stages of Arabidopsis stems and allows for the dissection of key biochemical and enzymatic factors controlling lignification.« less

Preparation of novel polyamine-type chelating resin with hyperbranched structures and its adsorption performance

NASA Astrophysics Data System (ADS)

Chen, Youning; Zhao, Wei; Wang, Huan; Li, Yuhong; Li, Chenxi

2018-02-01

This paper explored the method of combining atom transfer radical polymerization (ATRP) technology and hyperbranched polymer principle to prepare the high capacity chelating resin. First, surface-initiated atom transfer radical polymerization (SI-ATRP) method was used to graft glycidyl methacrylate (GMA) on chloromethylated cross-linked styrene-divinylbenzene resin, and then the novel polyamine chelating resin with a kind of hyperbranched structure was prepared through the amination reaction between amino group of (2-aminoethyl) triamine and epoxy group in GMA. This resin had a selective effect on As(V) and Cr(VI) at a relatively low pH and can be used for the disposal of waste water containing As(V) and Cr(VI). It had a relatively strong adsorption effect on Cu(II), Pb(II), Cd(II) and Cr(III) and can be used for the disposal of heavy metal ion waste water. The finding was that, the adsorption capacity of resin on the studied heavy metal ions was higher than that of the chelating resin synthesized by traditional technology and also higher than that of the resin modified by ATRP technology and bifunctional chelator, indicating that the combination of ATRP and hyperbranched polymer concept is an effective method to prepare chelating resin with high capacity.

Chemoselective phototransformation of C-H bonds on a polymer surface through a photoinduced cerium recycling redox reaction.

PubMed

Huang, Zhenhua; Wu, Zhengfang; Yang, Peng; Yang, Wantai

2014-09-01

It is generally accepted that Ce(4+) is unable to directly oxidize unreactive alkyl C-H bonds without the assistance of adjacent polar groups. Herein, we demonstrate in our newly developed confined photochemical reaction system that this recognized issue may be challenged. As we found, when a thin layer of a CeCl(3)/HCl aqueous solution was applied to a polymeric substrate and the substrate subjected to UV irradiation, Ce(3+) was first photooxidized to form Ce(4+) in the presence of H(+), and the in situ formed Ce(4+) then performs an oxidation reaction on the C-H bonds of the polymer surface to form surface-carbon radicals for radical graft polymerization reactions and functional-group transformations, while reducing to Ce(3+) and releasing H(+) in the process. This photoinduced cerium recycling redox (PCRR) reaction behaved as a biomimetic system in an artificial recycling reaction, leading to a sustainable chemical modification strategy for directly transforming alkyl C-H bonds on polymer surfaces into small-molecule groups and polymer brushes. This method is expected to provide a green and economical tool for industrial applications of polymer-surface modification. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface initiated atom transfer radical polymerization grafting of sodium styrene sulfonate from titanium and silicon substrates.

PubMed

Foster, Rami N; Keefe, Andrew J; Jiang, Shaoyi; Castner, David G

2013-11-01

This study investigates the grafting of poly-sodium styrene sulfonate (pNaSS) from trichlorosilane/10-undecen-1-yl 2-bromo-2-methylpropionate functionalized Si and Ti substrates by atom transfer radical polymerization (ATRP). The composition, molecular structure, thickness, and topography of the grafted pNaSS films were characterized with x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), variable angle spectroscopic ellipsometry (VASE), and atomic force microscopy (AFM), respectively. XPS and ToF-SIMS results were consistent with the successful grafting of a thick and uniform pNaSS film on both substrates. VASE and AFM scratch tests showed the films were between 25 and 49 nm thick on Si, and between 13 and 35 nm thick on Ti. AFM determined root-mean-square roughness values were ∼2 nm on both Si and Ti substrates. Therefore, ATRP grafting is capable of producing relatively smooth, thick, and chemically homogeneous pNaSS films on Si and Ti substrates. These films will be used in subsequent studies to test the hypothesis that pNaSS-grafted Ti implants preferentially adsorb certain plasma proteins in an orientation and conformation that modulates the foreign body response and promotes formation of new bone.

Surface functionalized SiO2 nanoparticles with cationic polymers via the combination of mussel inspired chemistry and surface initiated atom transfer radical polymerization: Characterization and enhanced removal of organic dye.

PubMed

Huang, Qiang; Liu, Meiying; Mao, Liucheng; Xu, Dazhuang; Zeng, Guangjian; Huang, Hongye; Jiang, Ruming; Deng, Fengjie; Zhang, Xiaoyong; Wei, Yen

2017-08-01

Monodispersed SiO 2 particles functionalized with cationic polymers poly-((3-acrylamidopropyl)trimethylammonium chloride) (PAPTCl) were prepared using mussel inspired surface modification strategy and surface initiated atom transfer radical polymerization (SI-ATRP). Fourier transform infrared spectroscopy, transmission electron microscope, thermogravimetric analysis, X-ray photoelectron spectroscopy, and zeta potential were employed to characterize these SiO 2 samples. The adsorption performance of the functionalized SiO 2 (donated as SiO 2 -PDA-PAPTCl) towards anionic organic dye Congo red (CR) was investigated to evaluate their potential environmental applications. We demonstrated that the surface of SiO 2 particles can be successfully functionalized with cationic PAPTCl. The adsorption capability of as-prepared SiO 2 was found to increases from 28.70 and 106.65mg/g after surface grafted with cationic polymers. The significant enhancement in the adsorption capability of SiO 2 -PDA-PAPTCl is mainly attributed to the introduction of cationic polymers. More importantly, this strategy is expected to be promising for fabrication of many other functional polymer nanocomposites for environmental applications due to the universality of mussel inspired chemistry and well designability and good monomer adaptability of SI-ATRP. Copyright © 2017 Elsevier Inc. All rights reserved.

A peroxidase mimic with atom transfer radical polymerization activity constructed through the grafting of heme onto metal-organic frameworks.

PubMed

Jiang, Wei; Pan, Yue; Yang, Jiebing; Liu, Yong; Yang, Yan; Tang, Jun; Li, Quanshun

2018-07-01

Atom transfer radical polymerization (ATRP) has been considered to be an efficient strategy for constructing functional macromolecules owing to its simple operation and versatile monomers, and thus it is of great significance to develop ideal catalysts with higher activity and perfect reusability. We constructed a peroxidase mimic through the grafting of heme onto metal-organic frameworks UiO-66-NH 2 (ZrMOF), namely Heme-ZrMOF. After the systematic characterization of structure, the composite Heme-ZrMOF was demonstrated to possess high peroxidase activity using 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) and 3,3',5,5'-tetramethylbenzidine as substrates. The enzyme mimic was then used as catalysts in the ATRP reactions of different monomers, in which favorable monomer conversion (44.6-98.0%) and product molecular weight (8600-25,600 g/mol) could be obtained. Compared to free heme, Heme-ZrMOF could efficiently achieve the easy separation of heme from the catalytic system and facilitate the ATRP reaction in an aqueous environment to avoid the utilization of organic solvents. In conclusion, the enzyme mimic Heme-ZrMOF could be potentially used as an effective catalyst for preparing well-defined polymers with biomedical applications. Copyright © 2018 Elsevier Inc. All rights reserved.

Surface initiated atom transfer radical polymerization grafting of sodium styrene sulfonate from titanium and silicon substrates

PubMed Central

Foster, Rami N.; Keefe, Andrew J.; Jiang, Shaoyi; Castner, David G.

2013-01-01

This study investigates the grafting of poly-sodium styrene sulfonate (pNaSS) from trichlorosilane/10-undecen-1-yl 2-bromo-2-methylpropionate functionalized Si and Ti substrates by atom transfer radical polymerization (ATRP). The composition, molecular structure, thickness, and topography of the grafted pNaSS films were characterized with x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), variable angle spectroscopic ellipsometry (VASE), and atomic force microscopy (AFM), respectively. XPS and ToF-SIMS results were consistent with the successful grafting of a thick and uniform pNaSS film on both substrates. VASE and AFM scratch tests showed the films were between 25 and 49 nm thick on Si, and between 13 and 35 nm thick on Ti. AFM determined root-mean-square roughness values were ∼2 nm on both Si and Ti substrates. Therefore, ATRP grafting is capable of producing relatively smooth, thick, and chemically homogeneous pNaSS films on Si and Ti substrates. These films will be used in subsequent studies to test the hypothesis that pNaSS-grafted Ti implants preferentially adsorb certain plasma proteins in an orientation and conformation that modulates the foreign body response and promotes formation of new bone. PMID:24482558

Preparation of novel polyamine-type chelating resin with hyperbranched structures and its adsorption performance

PubMed Central

Zhao, Wei; Wang, Huan; Li, Yuhong; Li, Chenxi

2018-01-01

This paper explored the method of combining atom transfer radical polymerization (ATRP) technology and hyperbranched polymer principle to prepare the high capacity chelating resin. First, surface-initiated atom transfer radical polymerization (SI-ATRP) method was used to graft glycidyl methacrylate (GMA) on chloromethylated cross-linked styrene-divinylbenzene resin, and then the novel polyamine chelating resin with a kind of hyperbranched structure was prepared through the amination reaction between amino group of (2-aminoethyl) triamine and epoxy group in GMA. This resin had a selective effect on As(V) and Cr(VI) at a relatively low pH and can be used for the disposal of waste water containing As(V) and Cr(VI). It had a relatively strong adsorption effect on Cu(II), Pb(II), Cd(II) and Cr(III) and can be used for the disposal of heavy metal ion waste water. The finding was that, the adsorption capacity of resin on the studied heavy metal ions was higher than that of the chelating resin synthesized by traditional technology and also higher than that of the resin modified by ATRP technology and bifunctional chelator, indicating that the combination of ATRP and hyperbranched polymer concept is an effective method to prepare chelating resin with high capacity. PMID:29515875

Synthesis of molecularly imprinted polymers by atom transfer radical polymerization for the solid-phase extraction of phthalate esters in edible oil.

PubMed

Chen, Ningning; He, Juan; Wu, Chaojun; Li, Yuanyuan; Suo, An; Wei, Hongliang; He, Lijun; Zhang, Shusheng

2017-03-01

Novel molecularly imprinted polymers of phthalate esters were prepared by atom transfer radical polymerization using methyl methacrylate as functional monomer, cyclohexanone as solvent, cuprous chloride as catalyst, 1-chlorine-1-ethyl benzene as initiator and 2,2-bipyridyl as cross-linker in the mixture of methanol and water (1:1, v/v). The effect of reaction conditions such as monomer ratio and template on the adsorption properties was investigated. The optimum condition was obtained by an orthogonal experiment. The obtained polymers were characterized using scanning electron microscopy. The binding property was studied with both static and dynamic methods. Results showed that the polymers exhibited excellent recognition capacity and outstanding selectivity for ten phthalate esters. Factors affecting the extraction efficiency of the molecularly imprinted solid-phase extraction were systematically investigated. An analytical method based on the molecularly imprinted coupled with gas chromatography and flame ionization detection was successfully developed for the simultaneous determination of ten phthalate esters from edible oil. The method detection limits were 0.10-0.25 μg/mL, and the recoveries of spiked samples were 82.5-101.4% with relative standard deviations of 1.24-5.37% (n = 6). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A versatile platform for precise synthesis of asymmetric molecular brush in one shot.

PubMed

Xu, Binbin; Feng, Chun; Huang, Xiaoyu

2017-08-24

Asymmetric molecular brushes emerge as a unique class of nanostructured polymers, while their versatile synthesis keeps a challenge for chemists. Here we show the synthesis of well-defined asymmetric molecular double-brushes comprising two different side chains linked to the same repeat unit along the backbone by one-pot concurrent atom transfer radical polymerization (ATRP) and Cu-catalyzed azide/alkyne cycloaddition (CuAAC) reaction. The double-brushes are based on a poly(Br-acrylate-alkyne) homopolymer possessing an alkynyl for CuAAC reaction and a 2-bromopropionate initiating group for ATRP in each repeat unit. The versatility of this one-shot approach is demonstrated by CuAAC reaction of alkynyl/poly(ethylene oxide)-N 3 and ATRP of various monomers. We also show the quantitative conversion of pentafluorophenyl ester groups to amide groups in side chains, allowing for the further fabrication of diverse building blocks. This work provides a versatile platform for facile synthesis of Janus-type double-brushes with structural and functional control, in a minimum number of reactions.Producing well-defined polymer compositions and structures facilitates their use in many different applications. Here the authors show the synthesis of well-defined asymmetric double-brushes by a one-pot concurrent atom transfer radical polymerization and Cu-catalyzed Click reaction.

Investigation of Termination in Free Radical Polymerization by Use of >Diffusion-Limited Interactions in Polymer Solutions

NASA Astrophysics Data System (ADS)

Wisnudel, Marc; Torkelson, John

1997-03-01

Termination between radicals has been simulated by use of phosphorescence quenching interactions, showing that segmental diffusion plays a strong role in the origin of autoacceleration or the gel effect. Quenching rate constants (k_q) were measured between benzil-labeled polymer as a function of anthracene-labeled polymer in polystyrene or polymethylmethacrylate solutions. Values of kq were obtained for interactions involving end- or center-labeled chains as a function of polymer MW and concentration. A large effect of label location was observed as interactions between center-labeled chains resulted in values of kq that were more MW-dependent and smaller in magnitude than those for interactions between end-labeled chains. For interactions between end-labeled chains at concentrations between 0 and 600 g/L, data show only very weak dependencies of kq on MW and concentration dependencies similar to that of segmental mobility. In addition, comparisons of kq data for interactions in PMMA-toluene solutions with termination rate constant (k_t) data for MMA polymerizations, showing weaker concentration dependencies for both kq and kt than translational diffusion coefficients in similar solutions, also indicate that segmental diffusion is important in termination.

Use of a cocktail of spin traps for fingerprinting large range of free radicals in biological systems

PubMed Central

Marchand, Valérie; Charlier, Nicolas; Verrax, Julien; Buc-Calderon, Pedro; Levêque, Philippe; Gallez, Bernard

2017-01-01

It is well established that the formation of radical species centered on various atoms is involved in the mechanism leading to the development of several diseases or to the appearance of deleterious effects of toxic molecules. The detection of free radical is possible using Electron Paramagnetic Resonance (EPR) spectroscopy and the spin trapping technique. The classical EPR spin-trapping technique can be considered as a “hypothesis-driven” approach because it requires an a priori assumption regarding the nature of the free radical in order to select the most appropriate spin-trap. We here describe a “data-driven” approach using EPR and a cocktail of spin-traps. The rationale for using this cocktail was that it would cover a wide range of biologically relevant free radicals and have a large range of hydrophilicity and lipophilicity in order to trap free radicals produced in different cellular compartments. As a proof-of-concept, we validated the ability of the system to measure a large variety of free radicals (O-, N-, C-, or S- centered) in well characterized conditions, and we illustrated the ability of the technique to unambiguously detect free radical production in cells exposed to chemicals known to be radical-mediated toxic agents. PMID:28253308

Use of a cocktail of spin traps for fingerprinting large range of free radicals in biological systems.

PubMed

Marchand, Valérie; Charlier, Nicolas; Verrax, Julien; Buc-Calderon, Pedro; Levêque, Philippe; Gallez, Bernard

2017-01-01

It is well established that the formation of radical species centered on various atoms is involved in the mechanism leading to the development of several diseases or to the appearance of deleterious effects of toxic molecules. The detection of free radical is possible using Electron Paramagnetic Resonance (EPR) spectroscopy and the spin trapping technique. The classical EPR spin-trapping technique can be considered as a "hypothesis-driven" approach because it requires an a priori assumption regarding the nature of the free radical in order to select the most appropriate spin-trap. We here describe a "data-driven" approach using EPR and a cocktail of spin-traps. The rationale for using this cocktail was that it would cover a wide range of biologically relevant free radicals and have a large range of hydrophilicity and lipophilicity in order to trap free radicals produced in different cellular compartments. As a proof-of-concept, we validated the ability of the system to measure a large variety of free radicals (O-, N-, C-, or S- centered) in well characterized conditions, and we illustrated the ability of the technique to unambiguously detect free radical production in cells exposed to chemicals known to be radical-mediated toxic agents.

The initiating radical yields and the efficiency of polymerization for various dental photoinitiators excited by different light curing units.

PubMed

Neumann, Miguel G; Schmitt, Carla C; Ferreira, Giovana C; Corrêa, Ivo C

2006-06-01

To evaluate the efficiency of the photopolymerization of dental resins it is necessary to know to what extent the light emitted by the light curing units is absorbed by the photoinitiators. On the other hand, the efficiency of the absorbed photons to produce species that launch the polymerization process is also of paramount importance. Therefore, the previously determined PAE (photon absorption efficiency) is used in conjunction with the polymerization quantum yields for the photoinitiators, in order to be able to compare the total process on an equivalent basis. This parameter can be used to identify the best performance for the photochemical process with specific photoinitiators. The efficiency of LED (Ultrablue IS) and QTH (Optilux 401) lamps were tested comparing their performances with the photoinitiators camphorquinone (CQ); phenylpropanedione (PPD); monoacylphosphine oxide (Lucirin TPO); and bisacylphosphine oxide (Irgacure 819). The extent of photopolymerization per absorbed photon was determined from the polymerization quantum yields obtained by using the photoinitiators to polymerize methyl methacrylate, and afterwards combined with the previously determined PAEs. Although CQ presents a rather low polymerization quantum yield, its photopolymerization efficiency is practically the highest when irradiated with the Ultrablue LED. On the other hand, Lucirin is much more efficient than the other photoinitiators when irradiated with a QTH lamp, due to its high quantum yield and the overlap between its absorption spectrum and the output of the visible lamp light. Difference in photopolymerization efficiencies arise when combinations of photoinitiators are used, and when LED sources are used in preference to QTH. Mechanistic understanding is essential to optimal initiator formulation.

Tris(trimethylsilyl)silane as a co-initiator for dental adhesive: Photo-polymerization kinetics and dynamic mechanical property

PubMed Central

Song, Linyong; Ye, Qiang; Ge, Xueping; Misra, Anil; Spencer, Paulette

2017-01-01

Objectives The purpose of this study was to evaluate the polymerization behavior of a model dentin adhesive with tris(trimethylsilyl)silane (TTMSS) as a co-initiator, and to investigate the polymerization kinetics and mechanical properties of copolymers in dry and wet conditions. Methods A co-monomer mixture based on HEMA/BisGMA (45/55, w/w) was used as a model dentin adhesive. The photoinitiator system included camphorquinone (CQ) as the photosensitizer and the co-initiator was ethyl-4-(dimethylamino) benzoate (EDMAB) or TTMSS. Iodonium salt, diphenyliodonium hexafluorophosphate (DPIHP) serving as a catalyst, was selectively added into the adhesive formulations. The control and the experimental formulations were characterized with regard to the degree of conversion (DC) and dynamic mechanical properties under dry and wet conditions. Results In two-component photoinitiator system (CQ/TTMSS), with an increase of TTMSS concentration, the polymerization rate and DC of C═C double bond increased, and showed a dependence on the irradiation time and curing light intensity. The copolymers that contained the three-component photoinitiator system (CQ/TTMSS/DPIHP) showed similar dynamic mechanical properties, under both dry and wet conditions, to the EDMAB-containing system. Significance The DC of formulations using TTMSS as co-initiator showed a strong dependence on irradiation time. With the addition of TTMSS, the maximum polymerization rate can be adjusted and the network structure became more homogenous. The results indicated that the TTMSS could be used as a substitute for amine-type co-initiator in visible-light induced free radical polymerization of methacrylate-based dentin adhesives. PMID:26616688

Imaging free radicals in organelles, cells, tissue, and in vivo with immuno-spin trapping.

PubMed

Mason, Ronald Paul

2016-08-01

The accurate and sensitive detection of biological free radicals in a reliable manner is required to define the mechanistic roles of such species in biochemistry, medicine and toxicology. Most of the techniques currently available are either not appropriate to detect free radicals in cells and tissues due to sensitivity limitations (electron spin resonance, ESR) or subject to artifacts that make the validity of the results questionable (fluorescent probe-based analysis). The development of the immuno-spin trapping technique overcomes all these difficulties. This technique is based on the reaction of amino acid- and DNA base-derived radicals with the spin trap 5, 5-dimethyl-1-pyrroline N-oxide (DMPO) to form protein- and DNA-DMPO nitroxide radical adducts, respectively. These adducts have limited stability and decay to produce the very stable macromolecule-DMPO-nitrone product. This stable product can be detected by mass spectrometry, NMR or immunochemistry by the use of anti-DMPO nitrone antibodies. The formation of macromolecule-DMPO-nitrone adducts is based on the selective reaction of free radical addition to the spin trap and is thus not subject to artifacts frequently encountered with other methods for free radical detection. The selectivity of spin trapping for free radicals in biological systems has been proven by ESR. Immuno-spin trapping is proving to be a potent, sensitive (a million times higher sensitivity than ESR), and easy (not quantum mechanical) method to detect low levels of macromolecule-derived radicals produced in vitro and in vivo. Anti-DMPO antibodies have been used to determine the distribution of free radicals in cells and tissues and even in living animals. In summary, the invention of the immuno-spin trapping technique has had a major impact on the ability to accurately and sensitively detect biological free radicals and, subsequently, on our understanding of the role of free radicals in biochemistry, medicine and toxicology. Published by Elsevier B.V.

Reactivity of vinyl ethers and vinyl ribosides in UV-initiated free radical copolymerization with acceptor monomers.

PubMed

Pichavant, Loic; Guillermain, Céline; Coqueret, Xavier

2010-09-13

The reactivity of various vinyl ethers and vinyloxy derivatives of ribose in the presence of diethyl fumarate or diethyl maleate was investigated for evaluating the potential of donor-acceptor-type copolymerization applied to unsaturated monomers derived from renewable feedstock. The photochemically induced polymerization of model monomer blends in the bulk state was monitored by infrared spectroscopy. The method allowed us to examine the influence of monomer pair structure on the kinetic profiles. The simultaneous consumption of both monomers was observed, supporting an alternating copolymerization mechanism. A lower reactivity of the blends containing maleates compared with fumarates was confirmed. The obtained kinetic data revealed a general correlation between the initial polymerization rate and the Hansen parameter δ(H) associated with the H-bonding aptitude of the donor monomer.

Silica nanoparticles carrying boron-containing polymer brushes

NASA Astrophysics Data System (ADS)

Brozek, Eric M.; Mollard, Alexis H.; Zharov, Ilya

2014-05-01

A new class of surface-modified silica nanoparticles has been developed for potential applications in boron neutron capture therapy. Sub-50 nm silica particles were synthesized using a modified Stöber method and used in surface-initiated atom transfer radical polymerization of two biocompatible polymers, poly(2-(hydroxyethyl)methacrylate) and poly(2-(methacryloyloxy)ethyl succinate). The carboxylic acid and hydroxyl functionalities of the polymeric side chains were functionalized with carboranyl clusters in high yields. The resulting particles were characterized using DLS, TEM, solution 1H NMR, solid state 11B NMR and thermogravimetric analysis. The particles contain between 13 and 18 % of boron atoms by weight, which would provide a high amount of 10B nuclides for BNCT, while the polymer chains are suitable for further modification with cell targeting ligands.

Pinenes: Abundant and Renewable Building Blocks for a Variety of Sustainable Polymers.

PubMed

Winnacker, Malte

2018-05-14

Pinenes - a group of monoterpenes containing a double bond - are very suitable renewable building blocks for a variety of sustainable polymers and materials. Their abundance from mainly non-edible parts of plants as well as the feasibility to isolate them render these compounds unique amongst the variety of biomass that is utilizable for novel materials. Accordingly, their use for the synthesis of biobased polymers has been investigated intensively, and strong progress has been made with this especially within the past 2-3 years. Direct cationic or radical polymerization via the double bonds as well as polymerization upon their further functionalization can afford a variety of sustainable polymers suitable for many applications, which is summarized in this article. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Biocatalytic synthesis of maltodextrin-based acrylates from starch and α-cyclodextrin.

PubMed

Kloosterman, Wouter M J; Spoelstra-van Dijk, Gerda; Loos, Katja

2014-09-01

Novel 2-(β-maltooligooxy)-ethyl (meth)acrylate monomers are successfully synthesized by CGTase from Bacillus macerans catalyzed coupling of 2-(β-glucosyloxy)-ethyl acrylate and methacrylate with α-cyclodextrin or starch. HPLC-UV analysis shows that the CGTase catalyzed reaction yields 2-(β-maltooligooxy)-ethyl acrylates with 1 to 15 glucopyranosyl units. (1) H NMR spectroscopy reveals that the β-linkage in the acceptor molecule is preserved during the CGTase catalyzed coupling reaction, whereas the newly introduced glucose units are attached by α-(1,4)-glycosidic linkages. The synthesized 2-(β-maltooligooxy)-ethyl acrylate monomers are successfully polymerized by aqueous free radical polymerization to yield the comb-shaped glycopolymer poly(2-(β-maltooligooxy)-ethyl acrylate). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High temperature chemically resistant polymer concrete

DOEpatents

Sugama, T.; Kukacka, L.E.

High temperature chemically resistant, non-aqueous polymer concrete composites consist of about 12 to 20% by weight of a water-insoluble polymer binder. The binder is polymerized in situ from a liquid vinyl-type monomer or mixture of vinyl containing monomers such as triallylcyanurate, styrene, acrylonitrile, acrylamide, methacrylamide, methyl-methacrylate, trimethylolpropane trimethacrylate and divinyl benzene. About 5 to 40% by weight of a reactive inorganic filler selected from the group consisting of tricalcium silicate and dicalcium silicate and mixtures containing less than 2% free lime, and about 48 to 83% by weight of silica sand/ and a free radical initiator such as di-tert-butyl peroxide, azobisisobutyronitrile, benzoyl peroxide, lauryl peroxide, other orgaic peroxides and combinations to initiate polymerization of the monomer in the presence of the inorganic filers are used.

Room temperature synthesis and binding studies of solution-processable histamine-imprinted microspheres.

PubMed

Romano, Edwin F; Holdsworth, Clovia I; Quirino, Joselito P; So, Regina C

2018-01-01

Accurate quantification of histamine levels in food and in biological samples is important for monitoring the quality of food products and for the detection of pathophysiological conditions. In this study, solution processable histamine-imprinted microspheres were synthesized at 30°C via dilute free radical phototochemical polymerization technique using ethylene glycol dimethacrylate (EGDMA) as the crosslinker and methacrylic acid (MAA) as the monomer. The processability of the resulting polymer is dictated by the monomer feed concentration (eg, 4 wt% 80:20 EGDMA:MAA formulation) and solvent (acetonitrile). Whereas, the particle size is influenced by the monomer feed concentration, the presence of template molecule, and independent of the crosslinker content. Evaluation of the binding performance of the photochemically imprinted polymers (PCP) with different crosslinker content (80 and 90 wt%) indicated that the selective binding capacity was notably higher in PCP-80 (N= 16.0 μmol/g) compared to PCP-90 (N= 10.1 μmol/g) when analyzed via frontal analysis capillary electrophoresis (FACE) using Freundlich isotherm. In addition, PCP-80 microspheres are more selective toward histamine than conventional thermal polymers (CTP-80) prepared at 60°C in the presence of structural analogs such as histidine, imidazole, and tryptamine under cross-rebinding and competitive conditions. These results demonstrated that histamine-selective imprinted polymers can be obtained readily using room temperature photochemical polymerization where these materials can be subsequently used as recognition element for optical-based histamine sensing. Copyright © 2017 John Wiley & Sons, Ltd.

Sub-5 nm Domains in Ordered Poly(cyclohexylethylene)-block-poly(methyl methacrylate) Block Polymers for Lithography.

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

Kennemur, Justin; Yao, Li; Bates, Frank Stephen

2014-01-01

A series of poly(cyclohexylethylene)-block-poly- (methyl methacrylate) (PCHE PMMA) diblock copolymers with varying molar mass (4.9 kg/mol Mn 30.6 kg/mol) and narrow molar mass distribution were synthesized through a combination of anionic and atom transfer radical polymerization (ATRP) techniques. Heterogeneous catalytic hydrogenation of -(hydroxy)polystyrene (PS-OH) yielded -(hydroxy)poly(cyclohexylethylene) (PCHEOH) with little loss of hydroxyl functionality. PCHE-OH was reacted with -bromoisobutyryl bromide (BiBB) to produce an ATRP macroinitiator used for the polymerization of methyl methacrylate. PCHE PMMA is a glassy, thermally stable material with a large effective segment segment interaction parameter, eff = (144.4 6.2)/T (0.162 0.013), determined by meanfield analysis of order-to-disordermore » transition temperatures (TODT) measured by dynamic mechanical analysis and differential scanning calorimetry. Ordered lamellar domain pitches (9 D 33 nm) were identified by small-angle X-ray scattering from neat BCPs containing 43 52 vol % PCHE ( f PCHE). Atomic force microscopy was used to show 7.5 nm lamellar features (D = 14.8 nm) which are some of the smallest observed to date. The lowest molar mass sample (Mn = 4.9 kg/mol, f PCHE = 0.46) is characterized by TODT = 173 3 C and sub-5 nm nanodomains, which together with the sacrificial properties of PMMA and the high overall thermal stability place this material at the forefront of high- systems for advanced nanopatterning applications.« less

Nanoscale functionalization and characterization of surfaces with hydrogel patterns and biomolecules

NASA Astrophysics Data System (ADS)

Dinakar, Hariharasudhan Chirra

The advent of numerous tools, ease of techniques, and concepts related to nanotechnology, in combination with functionalization via simple chemistry has made gold important for various biomedical applications. In this dissertation, the development and characterization of planar gold surfaces with responsive hydrogel patterns for rapid point of care sensing and the functionalization of gold nanoparticles for drug delivery are highlighted. Biomedical micro- and nanoscale devices that are spatially functionalized with intelligent hydrogels are typically fabricated using conventional UV-lithography. Herein, precise 3-D hydrogel patterns made up of temperature responsive crosslinked poly(N-isopropylacrylamide) over gold were synthesized. The XY control of the hydrogel was achieved using microcontact printing, while thickness control was achieved using atom transfer radical polymerization (ATRP). Atomic force microscopy analysis showed that to the ATRP reaction time governed the pattern growth. The temperature dependent swelling ratio was tailored by tuning the mesh size of the hydrogel. While nanopatterns exhibited a broad lower critical solution temperature (LCST) transition, surface roughness showed a sharp LCST transition. Quartz crystal microbalance with dissipation showed rapid response behavior of the thin films, which makes them applicable as functional components in biomedical devices. The easy synthesis, relative biocompatibility, inertness, and easy functionalization of gold nanoparticles (GNPs) have made them useful for various biomedical applications. Although ATRP can be successfully carried out over GNPs, the yield of stable solution based GNPs for biomedical applications prove to be low. As an alternative approach, a novel method of ISOlating, FUnctionalizing, and REleasing nanoparticles (ISOFURE) was proposed. Biodegradable poly(beta-amino ester) hydrogels were used to synthesize ISOFURE-GNP composites. ATRP was performed inside the composite, and the final hydrogel coated GNPs were released via matrix degradation. Response analysis confirmed that the ISOFURE method led to the increased stability and yield of the hydrogel coated ISOFURE-GNPs. The ISOFURE protocol was also utilized in functionalizing GNPs with enzyme catalase in the absence of a stabilizing reagent. Biotin-streptavidin affinity was used as the bioconjugation method. Activity analysis of the conjugated enzyme showed that the ISOFURE-GNPs showed enhanced biomolecular loading relative to solution based stabilizing reagent passivated GNPs. KEYWORDS: Hydrogel, Gold nanoparticle, ISOFURE, Atom transfer radical polymerization, Microcontact printing

[Preparation of L-phenylalanine chiral ligand-exchange chromatographic stationary phase by atom transfer radical polymerization and resolution of racemates].

PubMed

Sun, Yang; Xu, Fei; Gong, Bolin

2011-09-01

A novel stationary phase was synthesized for chiral ligand-exchange chromatography via atom transfer radical polymerization (ATRP). Glycidyl methacrylate (GMA) was grafted onto the surface of the silica by ATRP using bromoisobutyryl bromide as an initiator, and the organic metal compound formed in the CuCl/2,2'-bipyridine(Bpy) system as a catalyst at room temperature. The chiral stationary phase was then synthesized by grafting L-phenylalanine on the surface of the silica. The stationary phase was characterized by means of elementary analysis and evaluated in detail to determine its separability. The amount of L-phenylalanine on the surface of silica was calculated to be 4.32 mg/m2. The results showed that the good enantioseparations of some DL-amino acids were obtained using ligand-exchange chromatography on the synthesized chiral stationary phase (50 degrees C) with 0.05 mol/L KH2PO4 and 0.1 mmol/L Cu(Ac)2 solution (pH 4.5) as the mobile phase at a flow rate of 1.0 mL/min and a wavelength of 223 nm. The influences of the mobile phase pH, concentration of Cu (II), and temperature of column on the resolution of DL-amino acids by ligand-exchange chromatography were investigated. The results showed that these conditions could affect the resolution of racemates. Compared with the column prepared by radical method using L-phenylalanine directly bonded onto the surface of the silica, the synthesized stationary phase showed a better separation ability, and the DL-aspartic acids and DL-asparagines could be separated at baseline.

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

The Influence of Zeolites on Radical Formation During Lignin Pyrolysis.

PubMed

Bährle, Christian; Custodis, Victoria; Jeschke, Gunnar; van Bokhoven, Jeroen A; Vogel, Frédéric

2016-09-08

Lignin from lignocellulosic biomass is a promising source of energy, fuels, and chemicals. The conversion of the polymeric lignin to fuels and chemicals can be achieved by catalytic and noncatalytic pyrolysis. The influence of nonporous silica and zeolite catalysts, such as silicalite, HZSM5, and HUSY, on the radical and volatile product formation during lignin pyrolysis was studied by in situ high-temperature electron paramagnetic resonance spectroscopy (HTEPR) as well as GC-MS. Higher radical concentrations were observed in the samples containing zeolite compared to the sample containing only lignin, which suggests that there is a stabilizing effect by the inorganic surfaces on the formed radical fragments. This effect was observed for nonporous silica as well as for HUSY, HZSM5, and silicalite zeolite catalysts. However, the effect is far larger for the zeolites owing to their higher specific surface area. The zeolites also showed an effect on the volatile product yield and the product distribution within the volatile phase. Although silicalite showed no effect on the product selectivity, the acidic zeolites such as HZSM5 or HUSY increased the formation of deoxygenated products such as benzene, toluene, xylene (BTX), and naphthalene. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Selective in vitro anticancer effect of superparamagnetic iron oxide nanoparticles loaded in hyaluronan polymeric micelles.

PubMed

Smejkalová, Daniela; Nešporová, Kristina; Huerta-Angeles, Gloria; Syrovátka, Jakub; Jirák, Daniel; Gálisová, Andrea; Velebný, Vladimír

2014-11-10

Due to its native origin, excellent biocompatibility and biodegradability, hyaluronan (HA) represents an attractive polymer for superparamagnetic iron oxide nanoparticles (SPION) coating. Herein, we report HA polymeric micelles encapsulating oleic acid coated SPIONs, having a hydrodynamic size of about 100 nm and SPION loading capacity of 1-2 wt %. The HA-SPION polymeric micelles were found to be selectively cytotoxic toward a number of human cancer cell lines, mainly those of colon adenocarcinoma (HT-29). The selective inhibition of cell growth was even observed when the SPION loaded HA polymeric micelles were incubated with a mixture of control and cancer cells. The selective in vitro inhibition could not be connected with an enhanced CD44 uptake or radical oxygen species formation and was rather connected with a different way of SPION intracellular release. While aggregated iron particles were visualized in control cells, nonaggregated solubilized iron oxide particles were detected in cancer cells. In vivo SPION accumulation in intramuscular tumor following an intravenous micelle administration was confirmed by magnetic resonance (MR) imaging and histological analysis. Having a suitable hydrodynamic size, high magnetic relaxivity, and being cancer specific and able to accumulate in vivo in tumors, SPION-loaded HA micelles represent a promising platform for theranostic applications.

3D-Hydrogel Based Polymeric Nanoreactors for Silver Nano-Antimicrobial Composites Generation.

PubMed

Soto-Quintero, Albanelly; Romo-Uribe, Ángel; Bermúdez-Morales, Víctor H; Quijada-Garrido, Isabel; Guarrotxena, Nekane

2017-08-01

This study underscores the development of Ag hydrogel nanocomposites, as smart substrates for antibacterial uses, via innovative in situ reactive and reduction pathways. To this end, two different synthetic strategies were used. Firstly thiol-acrylate (PSA) based hydrogels were attained via thiol-ene and radical polymerization of polyethylene glycol (PEG) and polycaprolactone (PCL). As a second approach, polyurethane (PU) based hydrogels were achieved by condensation polymerization from diisocyanates and PCL and PEG diols. In fact, these syntheses rendered active three-dimensional (3D) hydrogel matrices which were used as nanoreactors for in situ reduction of AgNO₃ to silver nanoparticles. A redox chemistry of stannous catalyst in PU hydrogel yielded spherical AgNPs formation, even at 4 °C in the absence of external reductant; and an appropriate thiol-functionalized polymeric network promoted spherical AgNPs well dispersed through PSA hydrogel network, after heating up the swollen hydrogel at 103 °C in the presence of citrate-reductant. Optical and swelling behaviors of both series of hydrogel nanocomposites were investigated as key factors involved in their antimicrobial efficacy over time. Lastly, in vitro antibacterial activity of Ag loaded hydrogels exposed to Pseudomona aeruginosa and Escherichia coli strains indicated a noticeable sustained inhibitory effect, especially for Ag-PU hydrogel nanocomposites with bacterial inhibition growth capabilities up to 120 h cultivation.

Radical production form the interaction of closed-shell molecules. 4. 1,4-diradicals and the isotope effects on the spontaneous polymerization of pentafluorostyrene

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

Pryor, W.A.; Iino, M.; Newkome, G.R.

1977-08-31

Kinetic isotope effects are reported for the spontaneous ''thermal'' (i.e., self-initiated) polymerization of 2,3,4,5,6-pentafluorostyrene-..beta..,..beta..-d/sub 2/. The isotope effect at 130/sup 0/C is about 0.9/sub 7/. This is similar to the value reported for styrene. It is argued that the spontaneous polymerization of PFS involves initiation by diradicals, and data on the scavengers galvinoxyl and 1,3-bis(diphenylene)-2-phenylallyl (BDPA) are presented to prove this. In contrast with the data for styrene, both these scavengers disappear in PFS at 100/sup 0/C in reactions that have virtually the same rate constant and are first order in scavenger. Transfer data on toluene and diphenylmethane with PFSmore » agree with our earlier data and show that added transfer agents produce a dramatic increase in the rate of polymerization of PFS. We infer from this that the most important mechanism by which diradicals are converted to monoradicals is by chain transfer to materials, either endogenous or added, that have benzylic hydrogens. The endogenous compounds that have benzylic hydrogens include all cyclic oligomers (such as diarylcyclobutanes) and polymer.« less

In-column bonded phase polymerization for improved packing uniformity

PubMed Central

Huckabee, Alexis G.; Yerneni, Charu; Jacobson, Rachel E.; Alzate, Edwin J.; Chen, Tse-Hong; Wirth, Mary J.

2017-01-01

It is difficult to pack chromatographic particles having polymeric-bonded phases because solvents used for making a stable slurry cause the polymer layer to swell. Growth of the polymer inside the column (in situ) after packing was investigated and compared with conventional, ex situ polymer growth. The method of activators generated by electron transfer, along with atom-transfer radical polymerization, enabled polymerization under ambient conditions. Nonporous, 0.62 µm silica particles with silane initiators were used. Polyacrylamide films with a hydrated thickness of 23 nm in 75:25 water/isopropanol grew in 55 min for both in situ and ex situ preparations, and the same carbon coverage was observed. Higher chromatographic resolution and better column-to-column reproducibility were observed for in situ polymer growth, as evaluated by hydrophilic interaction liquid chromatography for the model glycoprotein, ribonuclease B. In situ polymer growth was also found to give lower eddy diffusion, as shown by a narrower peak width for injected acetonitrile in 50:50 acetonitrile/water. When columns were packed more loosely, bed collapse occurred quickly for ex situ, but not for in situ, polymer growth. The higher resolution and stability for in situ polymer growth is explained by packing with hard, rather than soft, contacts between particles. PMID:28387037

Detection of peroxyl radicals from polluted air by free radical reaction combined with liquid chromatography signal amplification technique.

PubMed

Wang, Guoying; Jia, Shiming; Niu, Xiuli; Liu, Yanrong; Tian, Haoqi; Chen, Xuefu; Shi, Gaofeng

2018-01-22

Free radicals play an important role in the oxidizing power of polluted air, the development of aging-related diseases, the formation of ozone, and the production of secondary particulate matter. The high variability of peroxyl radical concentration has prevented the detection of possible trends or distributions in the concentration of free radicals. We present a new method, free radical reaction combined with liquid chromatography photodiode array detection, for identifying and quantifying peroxyl radicals in polluted air. Functionalized graphene was used for loading peroxyl radicals and reactive molecules in air sampling system, which can facilitate reaction kinetics (charge transfers) between peroxyl radicals and reaction molecules. Separation was performed with and without a preliminary exposure of the polluted air sample to reactive molecule(s) system. The integral chromatographic peak areas before and after air sampling are used to quantify the atmospheric peroxyl radicals in polluted air. The utility of the new technique was tested with measurements carried out in the field. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

X-band Electron Paramagnetic Resonance Investigation of Stable Organic Radicals Present under Cold Stratification in 'Fuji' Apple Seeds.

PubMed

Nakagawa, Kouichi; Matsumoto, Kazuhiro; Chaiserm, Nattakan; Priprem, Aroonsri

2017-01-01

We investigated stable organic radicals formed in response to cold stratification in 'Fuji' apple seeds using X-band (9 GHz) electron paramagnetic resonance (EPR) technique. This technique primarily detected two paramagnetic species in each seed. These two different radical species were assigned as a stable organic radical and Mn 2+ species based on the g values and hyperfine components. Signal from the stable radicals was noted at a g value of about 2.00 and was strong and relatively stable. Significant radical intensity changes were observed in apple seeds on refrigeration along with water supplementation. The strongest radical intensity and a very weak Mn 2+ signal were also observed for the seeds kept in moisture-containing sand in a refrigerator. Noninvasive EPR of the radicals present in each seed revealed that the stable radicals were located primarily in the seed coat. These results indicate that the significant radical intensity changes in apple seeds under refrigeration for at least 90 days followed by water supplementation for one week, can be related to cold stratification of the seeds.

Interaction chromatography for characterization and large-scale fractionation of chemically heterogeneous copolymers

NASA Astrophysics Data System (ADS)

Han, Junwon

The remarkable development of polymer synthesis techniques to make complex polymers with controlled chain architectures has inevitably demanded the advancement of polymer characterization tools to analyze the molecular dispersity in polymeric materials beyond size exclusion chromatography (SEC). In particular, man-made synthetic copolymers that consist of more than one monomer type are disperse mixtures of polymer chains that have distributions in terms of both chemical heterogeneity and chain length (molar mass). While the molecular weight distribution has been quite reliably estimated by the SEC, it is still challenging to properly characterize the chemical composition distribution in the copolymers. Here, I have developed and applied adsorption-based interaction chromatography (IC) techniques as a promising tool to characterize and fractionate polystyrene-based block, random and branched copolymers in terms of their chemical heterogeneity. The first part of this thesis is focused on the adsorption-desorption based purification of PS-b-PMMA diblock copolymers using nanoporous silica. The liquid chromatography analysis and large scale purification are discussed for the PS-b-PMMA block copolymers that have been synthesized by sequential anionic polymerization. SEC and IC are compared to critically analyze the contents of PS homopolymers in the as-synthesized block copolymers. In addition, I have developed an IC technique to provide faster and more reliable information on the chemical heterogeneity in the as-synthesized block copolymers. Finally, a large scale (multi-gram) separation technique is developed to obtain "homopolymer-free" block copolymers via a simple chromatographic filtration technique. By taking advantage of the large specific surface area of nanoporous silica (≈300m 2/g), large scale purification of neat PS-b-PMMA has successfully been achieved by controlling adsorption and desorption of the block copolymers on the silica gel surface using a gravity column. The second part of this thesis is focused on the liquid chromatography analysis and fractionation of RAFT-polymerized PS-b -PMMA diblock copolymers and AFM studies. In this study, PS- b-PMMA block copolymers were synthesized by a RAFT free radical polymerization process---the PMMA block with a phenyldithiobenzoate end group was synthesized first. The contents of unreacted PS and PMMA homopolymers in as-synthesized PS-b-PMMA block copolymers were quantitatively analyzed by solvent gradient interaction chromatography (SGIC) technique employing bare silica and C18-bonded silica columns, respectively. In addition, by 2-dimensional large-scale IC fractionation method, atomic force microscopy (AFM) study of these fractionated samples revealed various morphologies with respect to the chemical composition of each fraction. The third part of this thesis is to analyze random copolymers with tunable monomer sequence distributions using interaction chromatography. Here, IC was used for characterizing the composition and monomer sequence distribution in statistical copolymers of poly(styrene-co-4-bromostyrene) (PBrxS). The PBrS copolymers were synthesized by the bromination of monodisperse polystyrenes; the degree of bromination (x) and the sequence distribution were adjusted by varying the bromination time and the solvent quality, respectively. Both normal-phase (bare silica) and reversed-phase (C18-bonded silica) columns were used at different combinations of solvents and non-solvents to monitor the content of the 4-bromostyrene units in the copolymer and their average monomer sequence distribution. The fourth part of this thesis is to analyze and fractionate highly branched polymers such as dendronized polymers and star-shaped homo and copolymers. I have developed an interaction chromatography technique to separate polymers with nonlinear chain architecture. Specifically, the IC technique has been used to separate dendronized polymers and PS-based highly branched copolymers and to ultimately obtain well-defined dendronized or branched copolymers with a low polydispersity. The effects of excess arm-polymers on (1) the micellar self-assembly of dendronized polymers and (2) the regularity of the pore morphology in the low-k applications by the sol-gel process have been studied.

Development of polymeric nanopaclitaxel and comparison with free paclitaxel for effects on cell proliferation of MCF-7 and B16F0 carcinoma cells.

PubMed

Yadav, Deepak; Anwar, Mohammad Faiyaz; Garg, Veena; Kardam, Hemant; Beg, Mohd Nadeem; Suri, Suruchi; Gaur, Sikha; Asif, Mohd

2014-01-01

Paclitaxel is hydrophobic in nature and is recognized as a highly toxic anticancer drug, showing adverse effects in normal body sites. In this study, we developed a polymeric nano drug carrier for safe delivery of the paclitaxel to the cancer that releases the drug in a sustained manner and reduces side effects. N-isopropylacrylamide/ vinyl pyrrolidone (NIPAAm/VP) nanoparticles were synthesized by radical polymerization. Physico- chemical characterization of the polymeric nanoparticles was conducted using dynamic light scattering, transmission electron microscopy, scanning electron microscopy and nuclear magnetic resonance, which confirmed polymerization of formulated nanoparticles. Drug release was assessed using a spectrophotometer and cell viability assays were carried out on the MCF-7 breast cancer and B16F0 skin cancer cell lines. NIPAAm/ VP nanoparticles demonstrated a size distribution in the 65-108 nm range and surface charge measured -15.4 mV. SEM showed the nanoparticles to be spherical in shape with a slow drug release of ~70% in PBS at 38° over 96 h. Drug loaded nanoparticles were associated with increased viability of MCF-7 and B16F0 cells in comparison to free paclitaxel. Nano loaded paclitaxel shows high therapeutic efficiency by sustained release action for the longer period of time, i increasing its efficacy and biocompatibility for human cancer therapy. Therefore, paclitaxel loaded (NIPAAm/VP) nanoparticles may provide opportunities to expand delivery of the drug for clinical selection.

Highly Efficient and Facile Photocatalytic Recycling System Suitable for ICAR ATRP of Hydrophilic Monomers.

PubMed

Jiang, Xiaowu; Zhang, Lifen; Cheng, Zhenping; Zhu, Xiulin

2016-08-01

Photoinduced initiators for continuous activator regeneration atom transfer radical polymerization (ATRP) of hydrophilic monomers in heptane/ethanol latent-biphasic system for copper catalyst separation and recycling have been realized for the first time at room temperature with different wavelengths of visible light LED (green, blue, purple, and white LED) as external stimulus, using 2-bromophenylacetate as the ATRP initiator and camphorquinone/triethylamine as the photoinitiator. In this system, hybrid catalyst complex (HCc) is synthesized as a novel nonpolar catalyst, which is preferentially dissolved in heptane. The hydrophilic polymers obtained catalyzed by HCc in heptane/ethanol mixture solvent show typical "living" features, for example, the values of Mn,GPC increase linearly with monomer conversion up to quantitative level (>96%) and the molecular weight distributions were kept narrow (Mw /Mn < 1.20) throughout the polymerization process. It should be noted that the excellent controllability of this novel polymerization system can be achieved even after 5 catalyst recycling experiments under LED irradiation. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polymeric ionic liquid bucky gels as sorbent coatings for solid-phase microextraction.

PubMed

Zhang, Cheng; Anderson, Jared L

2014-05-30

Novel cross-linked polymeric ionic liquid (PIL) bucky gels were formed by free-radical polymerization of polymerizable ionic liquids gelled with multi-walled carbon nanotubes (MWCNT) and used as sorbent coatings for solid-phase microextraction (SPME). The combination of PIL with MWCNTs significantly enhanced the π-π interaction between the sorbent coatings and the aromatic analytes. Compared to the neat PIL-based sorbent coating, the PIL bucky gel sorbent coatings demonstrated higher extraction efficiency for the extraction of polycyclic aromatic hydrocarbons (PAHs). A partitioning extraction mechanism was observed for the PIL/MWCNT-based sorbent coatings indicating that the addition of MWCNTs did not seem to affect the extraction mechanism of the sorbent coating. The analyte-to-coating partition coefficients (logKfs) were estimated and the limits of detection (LOD) for selected PIL bucky gel sorbent coating were determined to be in the range of 1-2.5 ng L(-1). Recovery studies were also performed for PAHs in river and tap water to validate the applicability of the developed method. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis of HNTs@PEDOT composites via in situ chemical oxidative polymerization and their application in electrode materials

NASA Astrophysics Data System (ADS)

Wang, Fang; Zhang, Xianhong; Ma, Yuhong; Yang, Wantai

2018-01-01

The hybrid composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and halloysite nanotubes (HNTs) was synthesized by a two-step process. First, poly(sodium styrene sulfonate) (PSSNa) was grafted onto HNTs via surface initiated atom transfer radical polymerization. Then with the HNTs-g-PSS as a template and the grafted PSS chains as the counterion dopant, PEDOT was precipitated onto the template via in situ oxidization polymerization of EDOT to form HNTs@PEDOT hybrid composites. The conductivity of HNTs@PEDOT can reach up to 9.35 S/cm with the content of 40% HNTs-g-PSS, which increased almost 78 times than that of pure PEDOT (about 0.12 S/cm) prepared at the similar condition. Further treated with p-toluenesulfonic acid (TsOH) as external dopant, the conductivity of HNTs@PEDOT increased to 24.3 S/cm. The electrochemical properties of the composites were investigated with cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy with three-electrode cell configuration. The results showed that the capacitance of HNTs@PEDOT composite increased 55% than that of pure PEDOT.

Strategies to overcome polymerization shrinkage--materials and techniques. A review.

PubMed

Malhotra, Neeraj; Kundabala, M; Shashirashmi, Acharya

2010-03-01

Stress generation at tissue/resin composite interfaces is one of the important reasons for failure of resin-based composite (RBC) restorations owing to the inherent property of polymerization shrinkage. Unrelieved stresses can weaken the bond between the tooth structure and the restoration, eventually producing a gap at the restoration margins. This can lead to postoperative sensitivity, secondary caries, fracture of the restorations, marginal deterioration and discoloration. As polymerization shrinkage cannot be eliminated completely, various techniques and protocols have been suggested in the manipulation of, and restorative procedures for, RBCs to minimize the shrinkage and associated stresses. Introduction of various newer monomer systems (siloranes) may also overcome this problem of shrinkage stress. This review emphasizes the various material science advances and techniques advocated that are currently available or under trial/testing phase to deal with polymerization shrinkage in a clinical environment. Minimizing the shrinkage stresses in RBC restorations may lead to improvement in the success rate and survival of restorations. Thus, it is important for dental practitioners to be aware of various techniques and materials available to reduce these shrinkage stresses and be updated with the current knowledge available to deal with this issue.

Photopolymerization Of Levitated Droplets

NASA Technical Reports Server (NTRS)

Rembaum, Alan; Rhim, Won-Kyu; Hyson, Michael T.; Chang, Manchium

1989-01-01

Experimental containerless process combines two established techniques to make variety of polymeric microspheres. In single step, electrostatically-levitated monomer droplets polymerized by ultraviolet light. Faster than multiple-step emulsion polymerization process used to make microspheres. Droplets suspended in cylindrical quadrupole electrostatic levitator. Alternating electrostatic field produces dynamic potential along axis. Process enables tailoring of microspheres for medical, scientific, and industrial applications.

Design and experimental validation of an adaptive phononic crystal using highly dissipative polymeric material interface

NASA Astrophysics Data System (ADS)

Billon, K.; Ouisse, M.; Sadoulet-Reboul, E.; Collet, M.; Chevallier, G.; Khelif, A.

2017-04-01

In this paper, some numerical tools for dispersion analysis of periodic structures are presented, with a focus on the ability of the methods to deal with dissipative behaviour of the systems. An adaptive phononic crystal based on the combination of metallic parts and highly dissipative polymeric interface is designed. The system consists in an infinite periodic bidirectional waveguide. The periodic cylindrical pillars include a layer of shape memory polymer and Aluminum. The mechanical properties of the polymer depend on both temperature and frequency and can radically change from glassy to rubbery state, with various combination of high/low stiffness and high/low dissipation. A fractional derivative Zener model is used for the description of the frequency-dependent behaviour of the polymer. A 3D finite element model of the cell is developed for the design of the metamaterial. The "Shifted-Cell Operator" technique consists in a reformulation of the PDE problem by "shifting" in terms of wave number the space derivatives appearing in the mechanical behaviour operator inside the cell, while imposing continuity boundary conditions on the borders of the domain. Damping effects can easily be introduced in the system and a quadratic eigenvalue problem yields to the dispersion properties of the periodic structure. In order to validate the design and the adaptive character of the metamaterial, results issued from a full 3D model of a finite structure embedding an interface composed by a distributed set of the unit cells are presented. Various driving temperature are used to change the behaviour of the system. After this step, a comparison between the results obtained using the tunable structure simulation and the experimental results is presented. Two states are obtained by changing the temperature of the polymeric interface: at 25°C, the bandgap is visible around a selected frequency. Above the glass transition, the phononic crystal tends to behave as an homogeneous plate.

Acid generation mechanism in anion-bound chemically amplified resists used for extreme ultraviolet lithography

NASA Astrophysics Data System (ADS)

Komuro, Yoshitaka; Yamamoto, Hiroki; Kobayashi, Kazuo; Ohomori, Katsumi; Kozawa, Takahiro

2015-03-01

Extreme ultraviolet (EUV) lithography is the most promising candidate for the high-volume production of semiconductor devices with half-pitches of sub 10nm. An anion-bound polymer(ABP), in which at the anion part of onium salts is polymerized, has attracted much attention from the viewpoint of the control of acid diffusion. In this study, the acid generation mechanism in ABP films was investigated using γ and EUV radiolysis. On the basis of experimental results, the acid generation mechanism in anion-bound chemically amplified resists was proposed. The protons of acids are considered to be mainly generated through the reaction of phenyl radicals with diphenylsulfide radical cations that are produced through the hole transfer to the decomposition products of onium salts.

Acid generation mechanism in anion-bound chemically amplified resists used for extreme ultraviolet lithography

NASA Astrophysics Data System (ADS)

Komuro, Yoshitaka; Yamamoto, Hiroki; Kobayashi, Kazuo; Utsumi, Yoshiyuki; Ohomori, Katsumi; Kozawa, Takahiro

2014-11-01

Extreme ultraviolet (EUV) lithography is the most promising candidate for the high-volume production of semiconductor devices with half-pitches of sub-10 nm. An anion-bound polymer (ABP), in which the anion part of onium salts is polymerized, has attracted much attention from the viewpoint of the control of acid diffusion. In this study, the acid generation mechanism in ABP films was investigated using electron (pulse), γ, and EUV radiolyses. On the basis of experimental results, the acid generation mechanism in anion-bound chemically amplified resists was proposed. The major path for proton generation in the absence of effective proton sources is considered to be the reaction of phenyl radicals with diphenylsulfide radical cations that are produced through hole transfer to the decomposition products of onium salts.

Radiation-induced synthesis of poly(acrylic acid) nanogels

NASA Astrophysics Data System (ADS)

Matusiak, Malgorzata; Kadlubowski, Slawomir; Ulanski, Piotr

2018-01-01

Nanogel is a two-component system of a diameter in the range of tens of nanometers, consisting of an intramolecularly crosslinked polymer chain and solvent, typically water, filling the space between segments of the macromolecule. Microgels are bigger than nanogels and their size range is between 100 nm to 100 μm. One of the methods used for synthesizing nanogels is linking the segments of a single macromolecule with the use of ionizing radiation, by intramolecular recombination of radiation-generated polymer radicals. The main advantage of this technique is absence of monomers, catalysts, surfactants or crosslinking agents. This method is an interesting alternative way of synthesizing polymeric carriers for biomedical applications. The aim of the study was radiation synthesis and characterization of poly(acrylic acid) - PAA - nanogels and microgels. The physico-chemical properties were described by determination of weight-average molecular weight and dimensions (radius of gyration, hydrodynamic radius) of the nanogels and microgels. Influence of polymer concentration and dose on these parameters was analyzed. Adjusting the PAA concentration and absorbed dose, one can control the molecular weight and dimensions of nanogels. The solutions of PAA were irradiated with two sources of ionizing radiation: γ-source and electron accelerator. The former method yields mainly microgels due to prevailing intermolecular crosslinking, while the latter promotes intramolecular recombination of PAA-derived radicals and in consequence formation of nanogels. In the future radiation-synthesized PAA nanogels, after functionalization, will be tested as carriers for delivering radionuclides to the tumor cells.

Chemical determination of free radical-induced damage to DNA.

PubMed

Dizdaroglu, M

1991-01-01

Free radical-induced damage to DNA in vivo can result in deleterious biological consequences such as the initiation and promotion of cancer. Chemical characterization and quantitation of such DNA damage is essential for an understanding of its biological consequences and cellular repair. Methodologies incorporating the technique of gas chromatography/mass spectrometry (GC/MS) have been developed in recent years for measurement of free radical-induced DNA damage. The use of GC/MS with selected-ion monitoring (SIM) facilitates unequivocal identification and quantitation of a large number of products of all four DNA bases produced in DNA by reactions with hydroxyl radical, hydrated electron, and H atom. Hydroxyl radical-induced DNA-protein cross-links in mammalian chromatin, and products of the sugar moiety in DNA are also unequivocally identified and quantitated. The sensitivity and selectivity of the GC/MS-SIM technique enables the measurement of DNA base products even in isolated mammalian chromatin without the necessity of first isolating DNA, and despite the presence of histones. Recent results reviewed in this article demonstrate the usefulness of the GC/MS technique for chemical determination of free radical-induced DNA damage in DNA as well as in mammalian chromatin under a vast variety of conditions of free radical production.

Electrochemical models for the radical annihilation reactions in organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Armstrong, Neal R.; Anderson, Jeffrey D.; Lee, Paul A.; McDonald, Erin; Wightman, R. M.; Hall, Hank K.; Hopkins, Tracy; Padias, Anne; Thayumanavan, Sankaran; Barlow, Stephen; Marder, Seth R.

1998-12-01

Bilayer organic light emitting diodes (OLEDs), based upon vacuum deposited molecules, or single layer OLEDs, based upon spin-cast polymeric materials, doped with these same molecules, produce light from emissive states of the lumophores which are created through annihilation reactions of radical species, which can be modeled through solution electrochemistry. Difference seen in solution reduction and oxidation potentials of molecular components of OLEDs are a lower limit estimate to the differences in energy of these same radical species in the condensed phase environmental. The light emitted from an aluminum quinolate (Alq3)/triarylamine (TPD)-based OLED, or an Alq3/PVK single layers OLED, can be reproduce from solution cross reactions of Alq3/TPD+. The efficiency of this process increases as the oxidation potential of the TPD increases, due to added substituents. Radical cations and anions of solubilized version of quinacridone dopants (DIQA) which have been used to enhance efficiencies in these OLEDs, are shown to be electrochemically more stable than Alq3 and Alq3, and DIQA radical annihilation reactions produce the same emissive state as in the quinacridone-doped OLEDs. Electrochemical studies demonstrate the ways in which other dopants might enhance the efficiency and shift the color output of OLEDs, across the entire visible and near-IR spectrum. Chemical degradation pathways of these same molecular components, which they may undergo during OLED operation, are also revealed by these electrochemical studies.