Science.gov

Sample records for polymer nanocomposites synthetic

  1. Improving the drug delivery characteristics of graphene oxide based polymer nanocomposites through the "one-pot" synthetic approach of single-electron-transfer living radical polymerization

    NASA Astrophysics Data System (ADS)

    Gao, Peng; Liu, Meiying; Tian, Jianwen; Deng, Fengjie; Wang, Ke; Xu, Dazhuang; Liu, Liangji; Zhang, Xiaoyong; Wei, Yen

    2016-08-01

    Graphene oxide (GO) based polymer nanocomposites have attracted extensive research interest recently for their outstanding physicochemical properties and potential applications. However, surface modification of GO with synthetic polymers has demonstrated to be trouble for most polymerization procedures are occurred under non-aqueous solution, which will in turn lead to the restacking of GO. In this work, a facile and efficient "one-pot" strategy has been developed for surface modification of GO with synthetic polymers through single-electron-transfer living radical polymerization (SET-LRP). The GO based polymer nanocomposites were obtained via SET-LRP in aqueous solution using poly(ethylene glycol) methyl ether methacrylate (PEGMA) as the monomer and 11-bromoundecanoic acid as the initiator, which could be effectively adsorbed on GO through hydrophobic interaction. The successful preparation of GO based polymer nanocomposites was confirmed by a series of characterization techniques such as 1H nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. The resultant products exhibit high water disperisibility, excellent biocompatibility and high efficient drug loading capability, making these PEGylated GO nanocomposites promising candidates for biomedical applications.

  2. Piezoresistance in Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Rizvi, Reza

    Piezoresistivity in conductive polymer nanocomposites occurs because of the disturbance of particle networks in the polymer matrix. The piezoresistance effect becomes more prominent if the matrix material is compliant making these materials attractive for applications that require flexible force and displacement sensors such as e-textiles and biomechanical measurement devices. However, the exact mechanisms of piezoresistivity including the relationship between the matrix polymer, conductive particle, internal structure and the composite's piezoresistance need to be better understood before it can be applied for such applications. The objective of this thesis is to report on the development of conductive polymer nanocomposites for use as flexible sensors and electrodes. Electrically conductive and piezoresistive nanocomposites were fabricated by a scalable melt compounding process. Particular attention was given to elucidating the role of matrix and filler materials, plastic deformation and porosity on the electrical conduction and piezoresistance. These effects were parametrically investigated through characterizing the morphology, electrical properties, rheological properties, and piezoresistivity of the polymer nanocomposites. The electrical and rheological behavior of the nanocomposites was modeled by the percolation-power law. Furthermore, a model was developed to describe the piezoresistance behavior during plastic deformation in relation to the stress and filler concentration.

  3. The anti-calcification potential of a silsesquioxane nanocomposite polymer under in vitro conditions: potential material for synthetic leaflet heart valve.

    PubMed

    Ghanbari, Hossein; Kidane, Asmeret G; Burriesci, Gaetano; Ramesh, Bala; Darbyshire, Arnold; Seifalian, Alexander M

    2010-11-01

    Calcification currently represents a major cause of failure of biological tissue heart valves. It is a complex phenomenon influenced by a number of biochemical and mechanical factors. Recent advances in material science offer new polymers with improved properties, potentially suitable for synthetic leaflets heart valves manufacturing. In this study, the calcification-resistance efficacy and mechanical and surface properties of a new nanocomposite polymeric material (polyhedral oligomeric silsesquioxane-poly(carbonate-urea)urethane; POSS-PCU) which has been developed by our group are assessed by means of in vitro testing. In particular, thin sheets of nanocomposite, glutaraldehyde-fixed bovine pericardium (BP) and polyurethane (PU) were exposed to a calcium solution into a specially designed in vitro accelerated physiological pulsatile pressure system for a period of 31days and a total of 4×10(7) cycles. The samples were investigated for signs of calcification after exposure to calcium solution by means of X-ray, microscopic and chemical inspections. Mechanical and surface properties were also studied using stress-strain behaviour and surface morphology and hydrophobicity. Comparison shows that, in the experimental conditions, the level of calcification for the nanocomposite is considerably lower than for the fixed BP (p=0.008) and PU samples (p=0.015). Also, mechanical properties were unchanged in POSS-PCU, while there was a significant deterioration in PU samples (p<0.05). Hydrophobicity was significantly reduced in both the POSS-PCU and PU samples (p<0.0001). However, the POSS-PCU nanocomposite remained more hydrophobic than the PU sample (p<0.0001). Less platelet adhered to the POSS-PCU compared to the PU (p<0.0001). These results indicate that the use of this nanocomposite in synthetic leaflets heart valves may lead to potential advantages in terms of long-term performances and durability. Copyright © 2010. Published by Elsevier Ltd.

  4. Synthetic hydrophilic polymers

    NASA Astrophysics Data System (ADS)

    Rajasekharan Pillai, V. N.; Mutter, Manfred

    1981-11-01

    Synthetic hydrophilic polymers find promising applications in pharmacology, biotechnology and chemistry. The biocompatibility, biodegradability and pharmacological activity of these polymers depend much on their hydrophilic nature. This article summarizes the recent developments in the utilization of the different classes of these hydrophilic polymers as pharmacologically active agents, for enzyme modification and as catalysts and supports for chemical reactions.

  5. Synthetic Architecture of MgO/C Nanocomposite from Hierarchical-Structured Coordination Polymer toward Enhanced CO2 Capture.

    PubMed

    Li, Ping; Liu, Wen; Dennis, John S; Zeng, Hua Chun

    2017-03-22

    Highly efficient, durable, and earth-abundant solid sorbents are of paramount importance for practical carbon capture, storage, and utilization. Here, we report a novel and facile two-step strategy to synthesize a group of hierarchically structured porous MgO/C nanocomposites using flowerlike Mg-containing coordination polymer as a precursor. The new nanocomposites exhibit superb CO2 capture performance with sorption capacity up to 30.9 wt % (at 27 °C, 1 bar CO2), fast sorption kinetics, and long cycling life. Importantly, the achieved capacity is >14 times higher than that of commercial MgO, and favorably exceeds the highest value recorded to date for MgO-based sorbents under similar operating conditions. On the basis of the morphological and textural property analysis, together with CO2 sorption mechanism study using CO2-TPD and DRIFT techniques, the outstanding performance in CO2 uptake originates from unique features of this type of sorbent materials, which include hierarchical architecture, porous building blocks of nanosheets, high specific surface area (ca. 300 m(2)/g), evenly dispersed MgO nanocrystallites (ca. 3 nm) providing abundant active sites, and the in situ generated carbon matrix that acts as a stabilizer to prevent the growth and agglomeration of MgO crystallites. The nanocomposite system developed in this work shows good potential for future low-cost CO2 abatement and utilization.

  6. Analysis of Synthetic Polymers.

    ERIC Educational Resources Information Center

    Smith, Charles G.; And Others

    1989-01-01

    Reviews techniques for the characterization and analysis of synthetic polymers, copolymers, and blends. Includes techniques for structure determination, separation, and quantitation of additives and residual monomers; determination of molecular weight; and the study of thermal properties including degradation mechanisms. (MVL)

  7. Molecular mechanisms of failure in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Gersappe, Dilip

    2003-03-01

    With the emergence of synthetic methods that can produce nanometer sized fillers, resulting in an enormous increase of surface area, polymers reinforced with nanoscale particles should offer the possibility of vastly improved properties. However, experimental evidence suggests that the paradigms that have been used for conventional filled composites cannot account for the behavior of nanocomposites. We examine the role that spherical nanofillers play on the rheology and the strength of the nanocomposite by using Molecular Dynamics simulations. We find that the enhancement of properties in nanocomposites is a result of the equivalence of time scales for motion for the polymer and the filler. We show that the mobility of the nanofiller, rather than its surface area, is key to the performance of the nanocomposite and that this mobility is a complex function of the size of the filler, the attraction between the polymer and the filler, and the thermodynamic state of the matrix. Our results show similarities between the toughening mechanisms in polymer nanocomposites and those postulated for naturally occurring biological materials which also contain nanoscaled assemblies, such as spider silk and abalone adhesive.

  8. An introduction to polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Armstrong, Gordon

    2015-11-01

    This review presents an overview of the formulation, characterization and range of applications for polymer nanocomposites. After explaining how material properties at the nanometre scale can vary compared to those observed at longer length scales, typical methods used to formulate and characterize nanocomposites at laboratory and industrial scale will be described. The range of mechanical, electrical and thermal properties obtainable from nanocomposite materials, with examples of current commercial applications, will be outlined. Formulation and characterization of nanoparticle, nanotube and graphene composites will be discussed by reference to nanoclay-based composites, as the latter are presently of most technological relevance. Three brief case studies are presented to demonstrate how structure/property relationships may be controlled in a variety of polymer nanocomposite systems to achieve required performance in a given application. The review will conclude by discussing potential obstacles to commercial uptake of polymer nanocomposites, such as inconsistent protocols to characterize nanocomposites, cost/performance balances, raw material availability, and emerging legislation, and will conclude by discussing the outlook for future development and commercial uptake of polymer nanocomposites.

  9. Graphene/Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Macosko, Chris

    2010-03-01

    Graphite has attracted large attention as a reinforcement for polymers due to its ability to modify electrical conductivity, mechanical and gas barrier properties of host polymers and its potentially lower cost than carbon nanotubes. If graphite can be exfoliated into atomically thin graphene sheets, it is possible to achieve the highest property enhancements at the lowest loading. However, small spacing and strong van der Waals forces between graphene layers make exfoliation of graphite via conventional composite manufacturing strategies challenging. Recently, two different approaches to obtain exfoliated graphite prior to blending were reported: thermal treatment (Schniepp et al., JACS 2006) and chemical modification (Stankovich et al., J Mat Chem 2006). Both start from graphite oxide. We will describe and evaluate these exfoliation approaches and the methods used to produce graphene reinforced thermoplastics, particularly polyester, polycarbonate and polyurethane nanocomposites. Three different dispersion methods - melt blending, solution mixing and in-situ polymerization -- are compared. Characterization of dispersion quality is illustrated with TEM, rheology and in electrical conductivity, tensile modulus and gas barrier property improvement.

  10. Polymer-phyllosilicate nanocomposites and their preparation

    DOEpatents

    Chaiko, David J.

    2007-01-09

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

  11. Biobased and biodegradable polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Qiu, Kaiyan

    In this dissertation, various noncrosslinked and crosslinked biobased and biodegradable polymer nanocomposites were fabricated and characterized. The properties of these polymer nanocomposites, and their relating mechanisms and corresponding applications were studied and discussed in depth. Chapter 1 introduces the research background and objectives of the current research. Chapter 2 presents the development of a novel low cost carbon source for bacterial cellulose (BC) production and fabrication and characterization of biobased polymer nanocomposites using produced BC and soy protein based resins. The carbon source, soy flour extract (SFE), was obtained from defatted soy flour (SF) and BC yield achieved using SFE medium was high. The results of this study showed that SFE consists of five sugars and Acetobacter xylinum metabolized sugars in a specific order. Chapter 3 discusses the fabrication and characterization of biodegradable polymer nanocomposites using BC and polyvinyl alcohol (PVA). These polymer nanocomposites had excellent tensile and thermal properties. Crosslinking of PVA using glutaraldehyde (GA) not only increased the mechanical and thermal properties but the water-resistance. Chapter 4 describes the development and characterization of microfibrillated cellulose (MFC) based biodegradable polymer nanocomposites by blending MFC suspension with PVA. Chemical crosslinking of the polymer nanocomposites was carried out using glyoxal to increase the mechanical and thermal properties as well as to make the PVA partially water-insoluble. Chapter 5 reports the development and characterization of halloysite nanotube (HNT) reinforced biodegradable polymer nanocomposites utilizing HNT dispersion and PVA. Several separation techniques were used to obtain individualized HNT dispersion. The results indicated uniform dispersion of HNTs in both PVA and malonic acid (MA) crosslinked PVA resulted in excellent mechanical and thermal properties of the materials, especially

  12. Polymer Functionalized Nanoparticles in Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Jayaraman, Arthi

    2013-03-01

    Significant interest has grown around the ability to control spatial arrangement of nanoparticles in a polymer nanocomposite to engineer materials with target properties. Past work has shown that one could achieve controlled assembly of nanoparticles in the polymer matrix by functionalizing nanoparticle surfaces with homopolymers. This talk will focus on our recent work using Polymer Reference Interaction Site Model (PRISM) theory and Monte Carlo simulations and GPU-based molecular dynamics simulations to specifically understand how heterogeneity in the polymer functionalization in the form of a) copolymers with varying monomer chemistry and monomer sequence, and b) polydispersity in homopolymer grafts can tune effective interactions between functionalized nanoparticles, and the assembly of functionalized nanoparticles.

  13. Magnetoelectric polymer nanocomposite for flexible electronics

    SciTech Connect

    Alnassar, M. Alfadhel, A.; Ivanov, Yu. P.; Kosel, J.

    2015-05-07

    This paper reports the fabrication and characterization of a new type of magnetoelectric polymer nanocomposite that exhibits excellent ferromagnetism and ferroelectricity simultaneously at room temperature. The multiferroic nanocomposite consists of high aspect ratio ferromagnetic iron nanowires embedded inside a ferroelectric co-polymer poly(vinylindene fluoride-trifluoroethylene), P(VDF-TrFE). The nanocomposite has been fabricated via a simple low temperature spin coating technique. Structural, ferromagnetic, ferroelectric, and magnetoelectric properties of the developed nanocomposite have been characterized. The nanocomposite films showed isotropic magnetic properties due to the random orientation of the iron nanowires inside the film. In addition, the embedded nanowires did not hinder the ferroelectric phase development of the nanocomposite. The developed nanocomposite showed a high magnetoelectric coupling response of 156 mV/cmOe measured at 3.1 kOe DC bias field. This value is among the highest reported magnetoelectric coupling in two phase particulate polymer nanocomposites.

  14. Multiscale modeling of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Sheidaei, Azadeh

    In recent years, polymer nano-composites (PNCs) have increasingly gained more attention due to their improved mechanical, barrier, thermal, optical, electrical and biodegradable properties in comparison with the conventional micro-composites or pristine polymer. With a modest addition of nanoparticles (usually less than 5wt. %), PNCs offer a wide range of improvements in moduli, strength, heat resistance, biodegradability, as well as decrease in gas permeability and flammability. Although PNCs offer enormous opportunities to design novel material systems, development of an effective numerical modeling approach to predict their properties based on their complex multi-phase and multiscale structure is still at an early stage. Developing a computational framework to predict the mechanical properties of PNC is the focus of this dissertation. A computational framework has been developed to predict mechanical properties of polymer nano-composites. In chapter 1, a microstructure inspired material model has been developed based on statistical technique and this technique has been used to reconstruct the microstructure of Halloysite nanotube (HNT) polypropylene composite. This technique also has been used to reconstruct exfoliated Graphene nanoplatelet (xGnP) polymer composite. The model was able to successfully predict the material behavior obtained from experiment. Chapter 2 is the summary of the experimental work to support the numerical work. First, different processing techniques to make the polymer nanocomposites have been reviewed. Among them, melt extrusion followed by injection molding was used to manufacture high density polyethylene (HDPE)---xGnP nanocomposties. Scanning electron microscopy (SEM) also was performed to determine particle size and distribution and to examine fracture surfaces. Particle size was measured from these images and has been used for calculating the probability density function for GNPs in chapter 1. A series of nanoindentation tests have

  15. Nanocomposite Polymer Electrolytes

    DTIC Science & Technology

    2000-11-30

    charge on the intercalation of poly(ethylene oxide) (PEO) was investigated using a series of reduced-charge montmorillonites and smectites with...Capacities of Reduced-Charge Nanocomposites were prepared by solution or melt inter- Montmorillonites calation. PEOs with molecular weights (MWs), 7500 (Poly... Montmorillonite High-charge montmorillonite SAz-1, middle-charge mont- by Molecular Simulations. Masters Thesis, Cornell Univerisity, Ithaca, morillonites HD

  16. Colloidal QDs-polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Gordillo, H.; Suárez, I.; Rodríguez-Cantó, P.; Abargues, R.; García-Calzada, R.; Chyrvony, V.; Albert, S.; Martínez-Pastor, J.

    2012-04-01

    Nanometer-size colloidal semiconductor nanocrystals, or Quantum Dots (NQD), are very prospective active centers because their light emission is highly efficient and temperature-independent. Nanocomposites based on the incorporation of QDs inside a polymer matrix are very promising materials for application in future photonic devices because they combine the properties of QDs with the technological feasibility of polymers. In the present work some basic applications of these new materials have been studied. Firstly, the fabrication of planar and linear waveguides based on the incorporation of CdS, CdSe and CdTe in PMMA and SU-8 are demonstrated. As a result, photoluminescence (PL) of the QDs are coupled to a waveguide mode, being it able to obtain multicolor waveguiding. Secondly, nanocomposite films have been evaluated as photon energy down-shifting converters to improve the efficiency of solar cells.

  17. Polymer/Silicate Nanocomposites Developed for Improved Thermal Stability and Barrier Properties

    NASA Technical Reports Server (NTRS)

    Campbell, Sandi G.

    2001-01-01

    The nanoscale reinforcement of polymers is becoming an attractive means of improving the properties and stability of polymers. Polymer-silicate nanocomposites are a relatively new class of materials with phase dimensions typically on the order of a few nanometers. Because of their nanometer-size features, nanocomposites possess unique properties typically not shared by more conventional composites. Polymer-layered silicate nanocomposites can attain a certain degree of stiffness, strength, and barrier properties with far less ceramic content than comparable glass- or mineral-reinforced polymers. Reinforcement of existing and new polyimides by this method offers an opportunity to greatly improve existing polymer properties without altering current synthetic or processing procedures.

  18. Synthetic biodegradable functional polymers for tissue engineering: a brief review

    PubMed Central

    BaoLin, GUO; MA, Peter X.

    2015-01-01

    Scaffolds play a crucial role in tissue engineering. Biodegradable polymers with great processing flexibility are the predominant scaffolding materials. Synthetic biodegradable polymers with well-defined structure and without immunological concerns associated with naturally derived polymers are widely used in tissue engineering. The synthetic biodegradable polymers that are widely used in tissue engineering, including polyesters, polyanhydrides, polyphosphazenes, polyurethane, and poly (glycerol sebacate) are summarized in this article. New developments in conducting polymers, photoresponsive polymers, amino-acid-based polymers, enzymatically degradable polymers, and peptide-activated polymers are also discussed. In addition to chemical functionalization, the scaffold designs that mimic the nano and micro features of the extracellular matrix (ECM) are presented as well, and composite and nanocomposite scaffolds are also reviewed. PMID:25729390

  19. Synthetic biodegradable functional polymers for tissue engineering: a brief review.

    PubMed

    BaoLin, Guo; Ma, Peter X

    2014-04-01

    Scaffolds play a crucial role in tissue engineering. Biodegradable polymers with great processing flexibility are the predominant scaffolding materials. Synthetic biodegradable polymers with well-defined structure and without immunological concerns associated with naturally derived polymers are widely used in tissue engineering. The synthetic biodegradable polymers that are widely used in tissue engineering, including polyesters, polyanhydrides, polyphosphazenes, polyurethane, and poly (glycerol sebacate) are summarized in this article. New developments in conducting polymers, photoresponsive polymers, amino-acid-based polymers, enzymatically degradable polymers, and peptide-activated polymers are also discussed. In addition to chemical functionalization, the scaffold designs that mimic the nano and micro features of the extracellular matrix (ECM) are presented as well, and composite and nanocomposite scaffolds are also reviewed.

  20. Fire retardant effects of polymer nanocomposites.

    PubMed

    Hull, T Richard; Stec, Anna A; Nazare, Shonali

    2009-07-01

    Among the many and varied applications of nanotechnology, the dispersion of nanoscopic fillers to form polymer nanocomposites with improved fire behaviour illustrates the potential and diversity of nanoscience. Different polymers decompose in different ways and fire retardants act to inhibit the decomposition or flaming combustion processes. Polymer nanocomposites form barriers between the fuel and air, reducing the rate of burning, but beyond that there is little consistency in their effects. It is shown that the decomposition products of polypropylene are changed by the presence of nanoclay, although there is only a small influence on the mass loss rate. The rheological properties of molten polymer nanocomposites are radically different from those of virgin polymers, and these will profoundly affect the heat transfer through the material, resulting in a shorter time to ignition and lower peak in the heat release rate, typical of polymer nanocomposites. The dispersion of nanofillers within polymers is generally measured in the cold polymer, but since this does not reflect the condition at the time of ignition, it is proposed that temperature ramped rheological measurements are more appropriate indicators of dispersion. The influence of polymer nanocomposite formation on the yields of toxic products from fire is studied using the ISO 19700 steady state tube furnace, and it is found that under early stages of burning more carbon monoxide and organoirritants are formed, but under the more toxic under-ventilated conditions, less toxic products are formed.

  1. Inorganic metal oxide/organic polymer nanocomposites and method thereof

    DOEpatents

    Gash, Alexander E.; Satcher, Joe H.; Simpson, Randy

    2004-03-30

    A synthetic method for preparation of hybrid inorganic/organic energetic nanocomposites is disclosed herein. The method employs the use of stable metal inorganic salts and organic solvents as well as an organic polymer with good solubility in the solvent system to produce novel nanocomposite energetic materials. In addition, fuel metal powders (particularly those that are oxophillic) can be incorporated into composition. This material has been characterized by thermal methods, energy-filtered transmission electron microscopy (EFTEM), N.sub.2 adsoprtion/desorption methods, and Fourier-Transform (FT-IR) spectroscopy. According to these characterization methods the organic polymer phase fills the nanopores of the composite material, providing superb mixing of the component phases in the energetic nanocomposite.

  2. Inorganic Metal Oxide/Organic Polymer Nanocomposites And Method Thereof

    DOEpatents

    Gash, Alexander E.; Satcher, Joe H.; Simpson, Randy

    2004-11-16

    A synthetic method for preparation of hybrid inorganic/organic energetic nanocomposites is disclosed herein. The method employs the use of stable metal in organic salts and organic solvents as well as an organic polymer with good solubility in the solvent system to produce novel nanocomposite energetic materials. In addition, fuel metal powders (particularly those that are oxophilic) can be incorporated into composition. This material has been characterized by thermal methods, energy-filtered transmission electron microscopy (EFTEM), N.sub.2 adsoprtion/desorption methods, and Fourier-Transform (FT-IR) spectroscopy. According to these characterization methods the organic polymer phase fills the nanopores of the material, providing superb mixing of the component phases in the energetic nanocomposite.

  3. Nanocomposite polymer electrolyte for rechargeable magnesium batteries

    SciTech Connect

    Shao, Yuyan; Rajput, Nav Nidhi; Hu, Jian Z.; Hu, Mary Y.; Liu, Tianbiao L.; Wei, Zhehao; Gu, Meng; Deng, Xuchu; Xu, Suochang; Han, Kee Sung; Wang, Jiulin; Nie, Zimin; Li, Guosheng; Zavadil, K.; Xiao, Jie; Wang, Chong M.; Henderson, Wesley A.; Zhang, Jiguang; Wang, Yong; Mueller, Karl T.; Persson, Kristin A.; Liu, Jun

    2014-12-28

    Nanocomposite polymer electrolytes present new opportunities for rechargeable magnesium batteries. However, few polymer electrolytes have demonstrated reversible Mg deposition/dissolution and those that have still contain volatile liquids such as tetrahydrofuran (THF). In this work, we report a nanocomposite polymer electrolyte based on poly(ethylene oxide) (PEO), Mg(BH4)2 and MgO nanoparticles for rechargeable Mg batteries. Cells with this electrolyte have a high coulombic efficiency of 98% for Mg plating/stripping and a high cycling stability. Through combined experiment-modeling investigations, a correlation between improved solvation of the salt and solvent chain length, chelation and oxygen denticity is established. Following the same trend, the nanocomposite polymer electrolyte is inferred to enhance the dissociation of the salt Mg(BH4)2 and thus improve the electrochemical performance. The insights and design metrics thus obtained may be used in nanocomposite electrolytes for other multivalent systems.

  4. MULTISCALE MODELING OF POLYMER NANOCOMPOSITES

    SciTech Connect

    Maiti, A

    2007-07-16

    Polymer Nanocomposites are an important class of nanomaterials with potential applications including but not limited to structural and cushion materials, electromagnetic and heat shields, conducting plastics, sensors, and catalysts for various chemical and bio processes. Success in most such applications hinges on molecular-level control of structure and assembly, and a deep understanding of how the overall morphology of various components and the interfaces between them affect the composite properties at the macroscale. The length and time-scales associated with such assemblies are prohibitively large for a full atomistic modeling. Instead we adopt a multiscale methodology in which atomic-level interactions between different components of a composite are incorporated into a coarse-grained simulation of the mesoscale morphology, which is then represented on a numerical grid and the macroscopic properties computed using a finite-elements method.

  5. Nanocomposites Derived from Polymers and Inorganic Nanoparticles

    PubMed Central

    Jeon, In-Yup; Baek, Jong-Beom

    2010-01-01

    Polymers are considered to be good hosting matrices for composite materials because they can easily be tailored to yield a variety of bulk physical properties. Moreover, organic polymers generally have long-term stability and good processability. Inorganic nanoparticles possess outstanding optical, catalytic, electronic and magnetic properties, which are significantly different their bulk states. By combining the attractive functionalities of both components, nanocomposites derived from organic polymers and inorganic nanoparticles are expected to display synergistically improved properties. The potential applications of the resultant nanocomposites are various, e.g. automotive, aerospace, opto-electronics, etc. Here, we review recent progress in polymer-based inorganic nanoparticle composites.

  6. Description of Extrudate Swell for Polymer Nanocomposites

    PubMed Central

    Wang, Kejian

    2010-01-01

    Extrudate swell is often observed to be weakened in nanocomposites compared to the pure polymer matrix. A theory quantifying this would be significant either for optimum processing or for understanding their viscoelasticity. A unified extrudate swell correlation with material properties and capillary parameters was suggested for polymer melt and their nanocomposites when considering the reservoir entry effect. More importantly, it was the first to find that the composite swell ratio can be the matrix swell ratio multiplied by the concentration shift factor, which is similar to the dynamic moduli expression for composites. The factor is a function of the shear field (stress or shear rate), filler content, filler internal structure and the surface state as well as the matrix properties. Several sets of swell data for nanocomposites were chosen from publications to test the new theories. The proposed quantitative model displayed good fit for the five kinds of nanocomposites, which verified the rationality of the swell theory for nanocomposites.

  7. Polymer and ceramic nanocomposites for aerospace applications

    NASA Astrophysics Data System (ADS)

    Rathod, Vivek T.; Kumar, Jayanth S.; Jain, Anjana

    2017-09-01

    This paper reviews the potential of polymer and ceramic matrix composites for aerospace/space vehicle applications. Special, unique and multifunctional properties arising due to the dispersion of nanoparticles in ceramic and metal matrix are briefly discussed followed by a classification of resulting aerospace applications. The paper presents polymer matrix composites comprising majority of aerospace applications in structures, coating, tribology, structural health monitoring, electromagnetic shielding and shape memory applications. The capabilities of the ceramic matrix nanocomposites to providing the electromagnetic shielding for aircrafts and better tribological properties to suit space environments are discussed. Structural health monitoring capability of ceramic matrix nanocomposite is also discussed. The properties of resulting nanocomposite material with its disadvantages like cost and processing difficulties are discussed. The paper concludes after the discussion of the possible future perspectives and challenges in implementation and further development of polymer and ceramic nanocomposite materials.

  8. Graphite nanoreinforcements in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Fukushima, Hiroyuki

    Nanocomposites composed of polymer matrices with clay reinforcements of less than 100 nm in size, are being considered for applications such as interior and exterior accessories for automobiles, structural components for portable electronic devices, and films for food packaging. While most nanocomposite research has focused on exfoliated clay platelets, the same nanoreinforcement concept can be applied to another layered material, graphite, to produce nanoplatelets and nanocomposites. Graphite is the stiffest material found in nature (Young's Modulus = 1060 GPa), having a modulus several times that of clay, but also with excellent electrical and thermal conductivity. The key to utilizing graphite as a platelet nanoreinforcement is in the ability to exfoliate this material. Also, if the appropriate surface treatment can be found for graphite, its exfoliation and dispersion in a polymer matrix will result in a composite with not only excellent mechanical properties but electrical properties as well, opening up many new structural applications as well as non-structural ones where electromagnetic shielding and high thermal conductivity are requirements. In this research, a new process to fabricate exfoliated nano-scale graphite platelets was established (Patent pending). The size of the resulted graphite platelets was less than 1 um in diameter and 10 nm in thickness, and the surface area of the material was around 100 m2/g. The reduction of size showed positive effect on mechanical properties of composites because of the increased edge area and more functional groups attached with it. Also various surface treatment techniques were applied to the graphite nanoplatelets to improve the surface condition. As a result, acrylamide grafting treatment was found to enhance the dispersion and adhesion of graphite flakes in epoxy matrices. The resulted composites showed better mechanical properties than those with commercially available carbon fibers, vapor grown carbon fibers

  9. Polymer nanocomposites for lithium battery applications

    DOEpatents

    Sandi-Tapia, Giselle; Gregar, Kathleen Carrado

    2006-07-18

    A single ion-conducting nanocomposite of a substantially amorphous polyethylene ether and a negatively charged synthetic smectite clay useful as an electrolyte. Excess SiO2 improves conductivity and when combined with synthetic hectorite forms superior membranes for batteries. A method of making membranes is also disclosed.

  10. Permeation properties of polymer/clay nanocomposites

    NASA Astrophysics Data System (ADS)

    Kalendova, A.; Merinska, D.; Gerard, J. F.

    2012-07-01

    The important characteristics of polymer/clay nanocomposites are stability, barrier properties and in the case of polyvinyl chloride also plasticizer migration into other materials. Therefore, the permeation properties of polymer/clay nanocomposites are discussed in this paper. The attention was focused to the polyethylene (PE) and polyvinyl chloride (PVC). Natural type of montmorillonite MMTNa+ and modified types of montmorillonite from Southern Clay Products were used as the inorganic phase. As the compounding machine, one screw Buss KO-kneader was employed. The principal aim is to fully exfoliate the clay into polymer matrix and enhanced the permeation properties. Prepared samples were tested for O2 and CO2 permeability. Polymer/clay nanocomposite structure was determined on the base of X-ray diffraction and electron microscopy (TEM).

  11. Thermoset polymer-layered silicic acid nanocomposites

    NASA Astrophysics Data System (ADS)

    Wang, Zhen

    Nanocomposites are formed when phase mixing occurs on a nanometer length scale. Due to the improved phase morphology and interfacial properties, nanocomposites exhibit mechanical properties superior to conventional composites. Toyota researchers first demonstrated that organoclay could be exfoliated in a nylon-6 matrix to greatly improve the thermal and mechanical properties of the polymer, which has resulted in a practical application in the automobile industry. A great deal of research has been conducted on organic-inorganic hybrid composites in which smectite clays are used as reinforcement agents. However, little work has been devoted to derivatives of other layered inorganic solids. In the present work, the first examples of organic polymer-layered silicic acid nanocomposites have been prepared by formation of a cured epoxy polymer network in the presence of organo cation exchange forms of magadiite. The exfoliation of silicate nanolayers in the epoxy matrix was achieved by in-situ intragallery polymerization during the thermosetting process. In general, the tensile properties, solvent resistance, barrier properties and chemical stability of the polymer matrix are greatly improved by the embedded silicate nanolayers when the matrix is flexible (sub-ambient Tg). The improvement of properties are dependent on the silicate loading, the degree of nanolayer separation and interfacial properties. Interestingly, the exfoliation also affects the polymer elasticity in a favorable way. The mechanism leading to nanocomposite formation is proposed. One exfoliated epoxy-magadiite nanocomposite/composition possessed unique transparent optical properties. The exfoliation chemistry was successfully extended to the other members of the layered silicic acid family. A new approach also was developed to prepare thermoset epoxy polymer-layered silicate nanocomposites in which curing agents can be directly intercalated into the intragallery without the need for alkylammonium ions

  12. Polymer-organoclay nanocomposites by melt processing

    NASA Astrophysics Data System (ADS)

    Cui, Lili

    2009-12-01

    Polymer-layered silicate nanocomposites based on a variety of polymer matrices and several organoclays were prepared by melt processing. A detailed characterization of the thermal degradation of several commercial and experimental organoclays often used to form polymer nanocomposites was reported. The surfactant type, loading, and purification level of organoclay significantly affect their thermal stability; however, broadly speaking, the results suggest that these differences in thermal stability do not appear to have much effect on the morphology and properties of the nanocomposites formed from them. It seems that the thermal stability of organoclays is not the key factor in organoclay exfoliation in melt processed polymer nanocomposites, since the exfoliation/dispersion process may have been completed on a time scale before the degradation of surfactant progresses to a detrimental level. Polymer nanocomposites have been made from a variety of polymers; however, few matrices have demonstrated the ability to readily exfoliate the organoclay as well as nylon 6, especially for highly hydrophobic materials like polyolefins. Hence, a significant part of this research work was devoted to explore various routes to improve polyolefin-organoclay interactions, and thus, organoclay exfoliation in these systems. Amine grafted polypropylenes and a conventionally used maleic anhydride grafted polypropylene were used as compatibilizers for polypropylene based nanocomposites to improve the organoclay exfoliation. A series of ethylene vinyl acetate copolymers, the polarity of which can be adjusted by varying their vinyl acetate contents, based nanocomposites were prepared as the model system to address the relationship between the polarity of the polymers and their preferences over various organoclay structures. Attempts were made to explore the effect of degree of neutralization of acid groups in ionomers on the morphology and properties of nanocomposites, and it seems that the

  13. Reversible Thermal Stiffening in Polymer Nanocomposites.

    PubMed

    Senses, Erkan; Isherwood, Andrew; Akcora, Pinar

    2015-07-15

    Miscible polymer blends with different glass transition temperatures (Tg) are known to create confined interphases between glassy and mobile chains. Here, we show that nanoparticles adsorbed with a high-Tg polymer, poly(methyl methacrylate), and dispersed in a low-Tg matrix polymer, poly(ethylene oxide), exhibit a liquid-to-solid transition at temperatures above Tg's of both polymers. The mechanical adaptivity of nanocomposites to temperature underlies the existence of dynamically asymmetric bound layers on nanoparticles and more importantly reveals their impact on macroscopic mechanical response of composites. The unusual reversible stiffening behavior sets these materials apart from conventional polymer composites that soften upon heating. The presented stiffening mechanism in polymer nanocomposites can be used in applications for flexible electronics or mechanically induced actuators responding to environmental changes like temperature or magnetic fields.

  14. Polymer matrix nanocomposites for automotive structural components

    DOE PAGES

    Naskar, Amit K.; Keum, Jong K.; Boeman, Raymond G.

    2016-12-06

    Over the past several decades, the automotive industry has expended significant effort to develop lightweight parts from new easy-to-process polymeric nanocomposites. These materials have been particularly attractive because they can increase fuel efficiency and reduce greenhouse gas emissions. However, attempts to reinforce soft matrices by nanoscale reinforcing agents at commercially deployable scales have been only sporadically successful to date. This situation is due primarily to the lack of fundamental understanding of how multiscale interfacial interactions and the resultant structures affect the properties of polymer nanocomposites. In this paper, we critically evaluate the state of the art in the field andmore » propose a possible path that may help to overcome these barriers. Finally, only once we achieve a deeper understanding of the structure–properties relationship of polymer matrix nanocomposites will we be able to develop novel structural nanocomposites with enhanced mechanical properties for automotive applications.« less

  15. Large-Strain Transparent Magnetoactive Polymer Nanocomposites

    NASA Technical Reports Server (NTRS)

    Meador, Michael A.

    2012-01-01

    A document discusses polymer nano - composite superparamagnetic actuators that were prepared by the addition of organically modified superparamagnetic nanoparticles to the polymer matrix. The nanocomposite films exhibited large deformations under a magnetostatic field with a low loading level of 0.1 wt% in a thermoplastic polyurethane elastomer (TPU) matrix. The maximum actuation deformation of the nanocomposite films increased exponentially with increasing nanoparticle concentration. The cyclic deformation actuation of a high-loading magnetic nanocomposite film was examined in a low magnetic field, and it exhibited excellent reproducibility and controllability. Low-loading TPU nanocomposite films (0.1-2 wt%) were transparent to semitransparent in the visible wavelength range, owing to good dispersion of the magnetic nanoparticles. Magnetoactuation phenomena were also demonstrated in a high-modulus, high-temperature polyimide resin with less mechanical deformation.

  16. Polymer matrix nanocomposites for automotive structural components.

    PubMed

    Naskar, Amit K; Keum, Jong K; Boeman, Raymond G

    2016-12-06

    Over the past several decades, the automotive industry has expended significant effort to develop lightweight parts from new easy-to-process polymeric nanocomposites. These materials have been particularly attractive because they can increase fuel efficiency and reduce greenhouse gas emissions. However, attempts to reinforce soft matrices by nanoscale reinforcing agents at commercially deployable scales have been only sporadically successful to date. This situation is due primarily to the lack of fundamental understanding of how multiscale interfacial interactions and the resultant structures affect the properties of polymer nanocomposites. In this Perspective, we critically evaluate the state of the art in the field and propose a possible path that may help to overcome these barriers. Only once we achieve a deeper understanding of the structure-properties relationship of polymer matrix nanocomposites will we be able to develop novel structural nanocomposites with enhanced mechanical properties for automotive applications.

  17. Polymer matrix nanocomposites for automotive structural components

    SciTech Connect

    Naskar, Amit K.; Keum, Jong K.; Boeman, Raymond G.

    2016-12-06

    Over the past several decades, the automotive industry has expended significant effort to develop lightweight parts from new easy-to-process polymeric nanocomposites. These materials have been particularly attractive because they can increase fuel efficiency and reduce greenhouse gas emissions. However, attempts to reinforce soft matrices by nanoscale reinforcing agents at commercially deployable scales have been only sporadically successful to date. This situation is due primarily to the lack of fundamental understanding of how multiscale interfacial interactions and the resultant structures affect the properties of polymer nanocomposites. In this paper, we critically evaluate the state of the art in the field and propose a possible path that may help to overcome these barriers. Finally, only once we achieve a deeper understanding of the structure–properties relationship of polymer matrix nanocomposites will we be able to develop novel structural nanocomposites with enhanced mechanical properties for automotive applications.

  18. Polymer matrix nanocomposites for automotive structural components

    NASA Astrophysics Data System (ADS)

    Naskar, Amit K.; Keum, Jong K.; Boeman, Raymond G.

    2016-12-01

    Over the past several decades, the automotive industry has expended significant effort to develop lightweight parts from new easy-to-process polymeric nanocomposites. These materials have been particularly attractive because they can increase fuel efficiency and reduce greenhouse gas emissions. However, attempts to reinforce soft matrices by nanoscale reinforcing agents at commercially deployable scales have been only sporadically successful to date. This situation is due primarily to the lack of fundamental understanding of how multiscale interfacial interactions and the resultant structures affect the properties of polymer nanocomposites. In this Perspective, we critically evaluate the state of the art in the field and propose a possible path that may help to overcome these barriers. Only once we achieve a deeper understanding of the structure-properties relationship of polymer matrix nanocomposites will we be able to develop novel structural nanocomposites with enhanced mechanical properties for automotive applications.

  19. Macromolecular Diffusion in Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Gam, Sangah; Meth, Jeff; Zane, Steve; Winey, Karen; Clarke, Nigel; Composto, Russell

    2011-03-01

    Macromolecular diffusion in crowded systems is important in biological and engineered systems. We have studied macromolecular diffusion through a model polymer nanocomposite (PNC) containing phenyl grafted silica nanoparticles (NPs), randomly distributed in a polystyrene matrix. Over a wide range of NP loading and tracer molecular weight (M), the scaling of the diffusion coefficient with M is in excellent agreement with the entropic barrier model (EBM) previously used to describe diffusion of DNA through confined media (e.g., gels and nanopores). To investigate the effect of NP size, diffusion was measured in PNC's with silica NPs having diameters of 28 and 12 nm. The normalized diffusion coefficients (D / D0) plotted against the interparticle separation relative to probe size (i.e., ID/ 2 Rg) collapse on a master curve. Diffusion in a poly(methyl methacrylate):silica NP system was also investigated to understand how attractive interactions (i.e., enthalpy) perturb motion relative to the polystyrene and phenyl-silica NP system which is athermal. Finally, a flux-based model is proposed and compared with experimental results.

  20. Asphaltenes-based polymer nano-composites

    DOEpatents

    Bowen, III, Daniel E

    2013-12-17

    Inventive composite materials are provided. The composite is preferably a nano-composite, and comprises an asphaltene, or a mixture of asphaltenes, blended with a polymer. The polymer can be any polymer in need of altered properties, including those selected from the group consisting of epoxies, acrylics, urethanes, silicones, cyanoacrylates, vulcanized rubber, phenol-formaldehyde, melamine-formaldehyde, urea-formaldehyde, imides, esters, cyanate esters, allyl resins.

  1. Preparation and Characterization of Novel Polymer/Silicate Nanocomposites

    SciTech Connect

    Harrup, Mason Kurt; Wertsching, Alan Kevin; Jones, Michael Glen

    2002-01-01

    Nanocomposite materials with an inorganic glass and an organic polymer constitute a relatively new and unique area in material science. The term “ormocers”, “ormosils” and “ceramers” are often utilized to describe this class of nanocomposite (1, 2). By combining at the molecular level inorganic and organic polymeric material a blending of unique physical properties can be achieved. The value in these materials is apparent, from fiber optics to paints these materials may provide the requisite physical properties to achieve the next technological advance. There are several different ways of synthesizing this class of nanocomposite; therefore a means of classification is necessary. Most developed nomenclature is based on synthetic techniques; Wilkes has a relatively recent and exhaustive categorization (3). However we chose to classify these materials upon a simpler system first suggested by Novak (4). Five categories cover the majority of composites synthesized with more recent techniques being modifications or combinations from this list.

  2. Cell microencapsulation with synthetic polymers

    PubMed Central

    Olabisi, Ronke M

    2015-01-01

    The encapsulation of cells into polymeric microspheres or microcapsules has permitted the transplantation of cells into human and animal subjects without the need for immunosuppressants. Cell-based therapies use donor cells to provide sustained release of a therapeutic product, such as insulin, and have shown promise in treating a variety of diseases. Immunoisolation of these cells via microencapsulation is a hotly investigated field, and the preferred material of choice has been alginate, a natural polymer derived from seaweed due to its gelling conditions. Although many natural polymers tend to gel in conditions favorable to mammalian cell encapsulation, there remain challenges such as batch to batch variability and residual components from the original source that can lead to an immune response when implanted into a recipient. Synthetic materials have the potential to avoid these issues; however, historically they have required harsh polymerization conditions that are not favorable to mammalian cells. As research into microencapsulation grows, more investigators are exploring methods to microencapsulate cells into synthetic polymers. This review describes a variety of synthetic polymers used to microencapsulate cells. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 846–859, 2015. PMID:24771675

  3. Cell microencapsulation with synthetic polymers.

    PubMed

    Olabisi, Ronke M

    2015-02-01

    The encapsulation of cells into polymeric microspheres or microcapsules has permitted the transplantation of cells into human and animal subjects without the need for immunosuppressants. Cell-based therapies use donor cells to provide sustained release of a therapeutic product, such as insulin, and have shown promise in treating a variety of diseases. Immunoisolation of these cells via microencapsulation is a hotly investigated field, and the preferred material of choice has been alginate, a natural polymer derived from seaweed due to its gelling conditions. Although many natural polymers tend to gel in conditions favorable to mammalian cell encapsulation, there remain challenges such as batch to batch variability and residual components from the original source that can lead to an immune response when implanted into a recipient. Synthetic materials have the potential to avoid these issues; however, historically they have required harsh polymerization conditions that are not favorable to mammalian cells. As research into microencapsulation grows, more investigators are exploring methods to microencapsulate cells into synthetic polymers. This review describes a variety of synthetic polymers used to microencapsulate cells. © 2014 The Authors. Journal of Biomedical Materials Research Part A Published by Wiley Periodicals, Inc.

  4. Synthesis, structure and properties of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Zeng, Changchun

    Over the last decade, the concept of utilizing nanoparticles to enhance polymer performance has drawn a great deal of research interest. Significant property enhancement can be achieved with a small amount of addition of nanoparticles. Spherical, platelet or tube/fiber like particles have all been used in the fabrication of nanocomposites. In this study, we chose platelet like clay particles to study the particle dispersion and properties of polymer nanocomposites and polymer nanocomposite foams. Free radical polymerization of methylmethacrylate (MMA) and styrene (St) in the presence of clay nanoparticles were studied in detail. The effect of interactions between the monomer, the initiator and clay surface modification was studied. By careful surface modification of clay surface and choice of initiator, clay particles can be dispersed uniformly at the nanometer scale (exfoliation). Exfoliation was achieved for PS nanocomposites with a clay concentration as high as 20 wt%. For PMMA, although fully exfoliated nanocomposite was only observed for clay concentration of 5 wt%, substantial exfoliation was observed in the 20 wt% nanocomposite. Nanocomposites were also prepared by extrusion compounding, with or without the aid of CO2. The effect of processing conditions on the degree of clay dispersion was studied. The relationships between clay dispersion, surfactant thermal stability and the resulting thermal properties, e.g., thermal stability, dimension stability, fire resistance were investigated. Novel polymer clay nanocomposite foams were prepared using carbon dioxide as the foaming agent. The role of clay on the foaming process was thoroughly investigated. It was found that clay serves as an efficient nucleation agent. Nucleation efficiency increases as the degree of clay dispersion improves. The exfoliated clay provides the highest nucleation efficiency. Nucleation efficiency can be further improved by tuning the interaction between polymer, CO2 and the surface

  5. A novel piezoresistive polymer nanocomposite MEMS accelerometer

    NASA Astrophysics Data System (ADS)

    Seena, V.; Hari, K.; Prajakta, S.; Pratap, Rudra; Ramgopal Rao, V.

    2017-01-01

    A novel polymer MEMS (micro electro mechanical systems) accelerometer with photo-patternable polymer nanocomposite as a piezoresistor is presented in this work. Polymer MEMS Accelerometer with beam thicknesses of 3.3 µm and embedded nanocomposite piezoresistive layer having a gauge factor of 90 were fabricated. The photosensitive nanocomposite samples were prepared and characterized for analyzing the mechanical and electrical properties and thereby ensuring proper process parameters for incorporating the piezoresistive layer into the polymer MEMS accelerometer. The microfabrication process flow and unit processes followed are extremely low cost with process temperatures below 100 °C. This also opens up a new possibility for easy integration of such polymer MEMS with CMOS (complementary metal oxide semiconductor) devices and circuits. The fabricated devices were characterized using laser Doppler vibrometer (LDV) and the devices exhibited a resonant frequency of 10.8 kHz and a response sensitivity of 280 nm g-1 at resonance. The main focus of this paper is on the SU-8/CB nanocomposite piezoresistive MEMS accelerometer technology development which covers the material and the fabrication aspects of these devices. CoventorWare FEA analysis performed using the extracted material properties from the experimental characterization which are in close agreement to performance parameters of the fabricated devices is also discussed. The simulated piezoresistive polymer MEMS devices showed an acceleration sensitivity of 126 nm g-1 and 82 ppm of ΔR/R per 1 g of acceleration.

  6. Reversible Thermal-Stiffening in Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Senses, Erkan; Akcora, Pinar

    2015-03-01

    Silica nanoparticles adsorbed with a high glass-transition temperature polymer, PMMA (Tg: 130 °C) are shown to uniformly disperse in a low-Tg polymer matrix, PEO (Tg: -60 °C). These nanocomposites exhibit an unusual reversible liquid-to-solid transition at temperatures above Tg's of both polymers. Mechanical adaptivity of PEO nanocomposites to temperatures underlies the existence of dynamically asymmetric bound layers on particles, and more importantly their impact on mechanical behavior, which sets these materials apart from conventional polymer composites that soften upon heating. Moreover, the growth rate of elastic moduli at temperatures above Tg of PMMA presents an Arrhenius-type relaxation with activation energy well-matching with the α- β merging region of PMMA. These results suggest that the mobility of the surface-bound polymer is essential for reinforcement contrary to commonly accepted glassy-layer hypothesis.

  7. Synthetic polymers for solar harvesting.

    PubMed

    Ghiggino, Kenneth P; Bell, Toby D M; Hooley, Emma N

    2012-01-01

    Synthetic polymers incorporating appropriate chromophores can act as light harvesting antennae for artificial photosynthetic systems. The photophysical processes occurring in a polymer based on phenylene vinylene have been investigated at the single chain level and in bulk solution to study energy transfer processes. Most single chains of an alternating copolymer of 2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene and 1,4-phenylene vinylene (alt-co-MEH-PPV) dispersed in a transparent polymer matrix act as single chromophore emitters demonstrating that energy transfer is an efficient process in these polymers. However for individual polymer chains there are fluctuations in emission intensity ('blinking') and shifts in emission spectra, decay lifetimes and emission dipole orientation occurring on a time-scale of tens of seconds. Fluorescence blinking also occurs on a sub-millisecond time-scale and follows exponential kinetics, whereas the longer blinking is better described by a power law. These observations can be interpreted as arising from environmental relaxation processes and/or changes in the emitter and demonstrate the wide distribution of photophysical behaviours that can be observed among the individual molecules of a polymer sample. The relevance of these studies to the application of polymer materials for solar harvesting is highlighted.

  8. Catalysts from synthetic genetic polymers

    PubMed Central

    Taylor, Alexander I.; Pinheiro, Vitor B.; Smola, Matthew J.; Morgunov, Alexey S.; Peak-Chew, Sew; Cozens, Christopher; Weeks, Kevin M.; Herdewijn, Piet; Holliger, Philipp

    2014-01-01

    The emergence of catalysis in early genetic polymers like RNA is considered a key transition in the origin of life1, predating the appearance of protein enzymes. DNA also demonstrates the capacity to fold into three-dimensional structures and form catalysts in vitro2. However, to what degree these natural biopolymers comprise functionally privileged chemical scaffolds3 for folding or the evolution of catalysis is not known. The ability of synthetic genetic polymers (XNAs) with alternative backbone chemistries not found in nature to fold into defined structures and bind ligands4 raises the possibility that these too might be capable of forming catalysts (XNAzymes). Here we report the discovery of such XNAzymes, elaborated in four different chemistries (ANA (arabino nucleic acids)5, FANA (2′-fluoroarabino nucleic acids)6, HNA (hexitol nucleic acids) and CeNA (cyclohexene nucleic acids)7 directly from random XNA oligomer pools, exhibiting in trans RNA endonuclease and ligase activities. We also describe an XNA-XNA ligase metalloenzyme in the FANA framework, establishing catalysis in an entirely synthetic system and enabling the synthesis of FANA oligomers and an active RNA endonuclease FANAzyme from its constituent parts. These results extend catalysis beyond biopolymers and establish technologies for the discovery of catalysts in a wide range of polymer scaffolds not found in nature8. Evolution of catalysis independent of any natural polymer has implications for the definition of chemical boundary conditions for the emergence of life on earth and elsewhere in the universe9. PMID:25470036

  9. Catalysts from synthetic genetic polymers.

    PubMed

    Taylor, Alexander I; Pinheiro, Vitor B; Smola, Matthew J; Morgunov, Alexey S; Peak-Chew, Sew; Cozens, Christopher; Weeks, Kevin M; Herdewijn, Piet; Holliger, Philipp

    2015-02-19

    The emergence of catalysis in early genetic polymers such as RNA is considered a key transition in the origin of life, pre-dating the appearance of protein enzymes. DNA also demonstrates the capacity to fold into three-dimensional structures and form catalysts in vitro. However, to what degree these natural biopolymers comprise functionally privileged chemical scaffolds for folding or the evolution of catalysis is not known. The ability of synthetic genetic polymers (XNAs) with alternative backbone chemistries not found in nature to fold into defined structures and bind ligands raises the possibility that these too might be capable of forming catalysts (XNAzymes). Here we report the discovery of such XNAzymes, elaborated in four different chemistries (arabino nucleic acids, ANA; 2'-fluoroarabino nucleic acids, FANA; hexitol nucleic acids, HNA; and cyclohexene nucleic acids, CeNA) directly from random XNA oligomer pools, exhibiting in trans RNA endonuclease and ligase activities. We also describe an XNA-XNA ligase metalloenzyme in the FANA framework, establishing catalysis in an entirely synthetic system and enabling the synthesis of FANA oligomers and an active RNA endonuclease FANAzyme from its constituent parts. These results extend catalysis beyond biopolymers and establish technologies for the discovery of catalysts in a wide range of polymer scaffolds not found in nature. Evolution of catalysis independent of any natural polymer has implications for the definition of chemical boundary conditions for the emergence of life on Earth and elsewhere in the Universe.

  10. Polymer based nanocomposites with tailorable optical properties

    NASA Astrophysics Data System (ADS)

    Colombo, Annalisa; Simonutti, Roberto

    2014-09-01

    Transparent polymers are extensively used in everyday life, from windows to computer displays, from food packaging to lenses. A possible approach for modulating their optical properties (refractive index, transparency, color and luminescence) is to change the chemical structure of the polymer, however this option is in many cases economically prohibitive. Our approach, instead, relies in the use of standard polymers with the supplement of specific nanostructured additives able to tune the final property of the material. Among others, the cases of luminescent solar concentrators based on poly(methylmethacrylate) containing luminescent quantum dots and highly transparent polymer nanocomposites with high refractive index will be presented.

  11. Polymer and spherical nanoparticle diffusion in nanocomposites

    NASA Astrophysics Data System (ADS)

    Karatrantos, Argyrios; Composto, Russell J.; Winey, Karen I.; Clarke, Nigel

    2017-05-01

    Nanoparticle and polymer dynamics in nanocomposites containing spherical nanoparticles were investigated by means of molecular dynamics simulations. We show that the polymer diffusivity decreases with nanoparticle loading due to an increase of the interfacial area created by nanoparticles, in the polymer matrix. We show that small sized nanoparticles can diffuse much faster than that predicted from the Stokes-Einstein relation in the dilute regime. We show that the nanoparticle diffusivity decreases at higher nanoparticle loading due to nanoparticle-polymer interface. Increase of the nanoparticle radius slows the nanoparticle diffusion.

  12. Ultrastrong and stiff layered polymer nanocomposites.

    PubMed

    Podsiadlo, Paul; Kaushik, Amit K; Arruda, Ellen M; Waas, Anthony M; Shim, Bong Sup; Xu, Jiadi; Nandivada, Himabindu; Pumplin, Benjamin G; Lahann, Joerg; Ramamoorthy, Ayyalusamy; Kotov, Nicholas A

    2007-10-05

    Nanoscale building blocks are individually exceptionally strong because they are close to ideal, defect-free materials. It is, however, difficult to retain the ideal properties in macroscale composites. Bottom-up assembly of a clay/polymer nanocomposite allowed for the preparation of a homogeneous, optically transparent material with planar orientation of the alumosilicate nanosheets. The stiffness and tensile strength of these multilayer composites are one order of magnitude greater than those of analogous nanocomposites at a processing temperature that is much lower than those of ceramic or polymer materials with similar characteristics. A high level of ordering of the nanoscale building blocks, combined with dense covalent and hydrogen bonding and stiffening of the polymer chains, leads to highly effective load transfer between nanosheets and the polymer.

  13. Molecular Mechanisms of Failure in Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Gersappe, Dilip

    2002-07-01

    Molecular dynamics simulations of polymers reinforced with nanoscopic filler particles reveal the mechanisms by which nanofillers improve the toughness of the material. We find that the mobility of the nanofiller particle, rather than its surface area, controls its ability to dissipate energy. Our results show similarities between the toughening mechanisms observed in polymer nanocomposites and those postulated for biological structural materials such as spider silk and abalone adhesive.

  14. The Role of Nanofillers in Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Xu, Di

    Polymer nanocomposites have been widely used in many fields. By introducing nanoparticles as fillers, researchers are able to get reinforced materials and new materials with novel properties, such as stronger mechanics, enhanced optical properties and improved conductivity. Though experimental techniques have rapidly advanced to enable better control of materials at atomic level, there is still a lack of a fundamental understanding of the dynamics and structure-properties relations in polymer nanocomposites. In this thesis, we use computer simulations to study the molecular structure and connections between microstate to macro properties of a variety of nanocomposites. Our goal is to understand the role of nanofillers in complex nanocomposite systems and to assist nanocomposite design. Nanoplatelet fillers, such as clays, have shown superior effects on the properties of polymer gels. We used molecular dynamic simulation to study nanoplatelet-filled composite gel system, in which short-range attraction exists between the polymer and nanoplatelet fillers. We show that the polymers and nanoplatelet fillers formed organic-inorganic networks with nanoplatelets acting as crosslink junctions, and the network eventually percolates the system as fillers reached a critical concentration. Stress auto-correlation and step-strain test were applied to investigate the mechanical properties; the results show the simulated composites changed from fluid-like to solid-like. The mechanical changes were consistent with the percolation transition, and gelation mechanism was therefore believed to be similar to those pure polymer physical gels. It was observed platelets aggregated into a local intercalation structure, which significantly differs from typical spherical fillers. This unique intercalation structure was examined by radial distribution function and ordering parameters. We discussed how intercalation would affect the properties of the platelet composites by comparing them with

  15. Graphite oxide flame-retardant polymer nanocomposites.

    PubMed

    Higginbotham, Amanda L; Lomeda, Jay R; Morgan, Alexander B; Tour, James M

    2009-10-01

    Graphite oxide (GO) polymer nanocomposites were developed at 1, 5, and 10 wt % GO with polycarbonate (PC), acrylonitrile butadiene styrene, and high-impact polystyrene for the purpose of evaluating the flammability reduction and material properties of the resulting systems. The overall morphology and dispersion of GO within the polymer nanocomposites were studied by scanning electron microscopy and optical microscopy; GO was found to be well-dispersed throughout the matrix without the formation of large aggregates. Mechanical testing was performed using dynamic mechanical analysis to measure the storage modulus, which increased for all polymer systems with increased GO loading. Microscale oxygen consumption calorimetry revealed that the addition of GO reduced the total heat release and peak heat release rates in all systems, and GO-PC composites demonstrated very fast self-extinguishing times in vertical open flame tests, which are important to some regulatory fire safety applications.

  16. Biomimetic Reversible Heat-Stiffening Polymer Nanocomposites

    PubMed Central

    2017-01-01

    Inspired by the ability of the sea cucumber to (reversibly) increase the stiffness of its dermis upon exposure to a stimulus, we herein report a stimuli-responsive nanocomposite that can reversibly increase its stiffness upon exposure to warm water. Nanocomposites composed of cellulose nanocrystals (CNCs) that are grafted with a lower critical solution temperature (LCST) polymer embedded within a poly(vinyl acetate) (PVAc) matrix show a dramatic increase in modulus, for example, from 1 to 350 MPa upon exposure to warm water, the hypothesis being that grafting the polymers from the CNCs disrupts the interactions between the nanofibers and minimizes the mechanical reinforcement of the film. However, exposure to water above the LCST leads to the collapse of the polymer chains and subsequent stiffening of the nanocomposite as a result of the enhanced CNC interactions. Backing up this hypothesis are energy conserving dissipative particle dynamics (EDPD) simulations which show that the attractive interactions between CNCs are switched on upon the temperature-induced collapse of the grafted polymer chains, resulting in the formation of a percolating reinforcing network. PMID:28852703

  17. Interfaces in polymer nanocomposites - An NMR study

    NASA Astrophysics Data System (ADS)

    Böhme, Ute; Scheler, Ulrich

    2016-03-01

    Nuclear Magnetic Resonance (NMR) is applied for the investigation of polymer nanocomposites. Solid-state NMR is applied to study the modification steps to compatibilize layered double hydroxides with non-polar polymers. 1H relaxation NMR gives insight on the polymer dynamics over a wide range of correlation times. For the polymer chain dynamics the transverse relaxation time T2 is most suited. In this presentation we report on two applications of T2 measurements under external mechanical stress. In a low-field system relaxation NMR studies are performed in-situ under uniaxial stress. High-temperature experiments in a Couette cell permit the investigation of the polymer dynamics in the melt under shear flow.

  18. Nanocomposites of polymer and inorganic nanoparticles for optical and magnetic applications

    PubMed Central

    Li, Shanghua; Meng Lin, Meng; Toprak, Muhammet S.; Kim, Do Kyung; Muhammed, Mamoun

    2010-01-01

    This article provides an up-to-date review on nanocomposites composed of inorganic nanoparticles and the polymer matrix for optical and magnetic applications. Optical or magnetic characteristics can change upon the decrease of particle sizes to very small dimensions, which are, in general, of major interest in the area of nanocomposite materials. The use of inorganic nanoparticles into the polymer matrix can provide high-performance novel materials that find applications in many industrial fields. With this respect, frequently considered features are optical properties such as light absorption (UV and color), and the extent of light scattering or, in the case of metal particles, photoluminescence, dichroism, and so on, and magnetic properties such as superparamagnetism, electromagnetic wave absorption, and electromagnetic interference shielding. A general introduction, definition, and historical development of polymer–inorganic nanocomposites as well as a comprehensive review of synthetic techniques for polymer–inorganic nanocomposites will be given. Future possibilities for the development of nanocomposites for optical and magnetic applications are also introduced. It is expected that the use of new functional inorganic nano-fillers will lead to new polymer–inorganic nanocomposites with unique combinations of material properties. By careful selection of synthetic techniques and understanding/exploiting the unique physics of the polymeric nanocomposites in such materials, novel functional polymer–inorganic nanocomposites can be designed and fabricated for new interesting applications such as optoelectronic and magneto-optic applications. PMID:22110855

  19. Supramolecular Polymer Nanocomposites - Improvement of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Hinricher, Jesse; Neikirk, Colin; Priestley, Rodney

    2015-03-01

    Supramolecular polymers differ from traditional polymers in that their repeat units are connected by hydrogen bonds that can reversibly break and form under various stimuli. They can be more easily recycled than conventional materials, and their highly temperature dependent viscosities result in reduced energy consumption and processing costs. Furthermore, judicious selection of supramolecular polymer architecture and functionality allows the design of advanced materials including shape memory and self-healing materials. Supramolecular polymers have yet to see widespread use because they can't support much weight due to their inherent mechanical weakness. In order to address this issue, the mechanical strength of supramolecular polymer nanocomposites based on ureidopyrmidinone (UPy) telechelic poly(caprolactone) doped with surface activated silica nanoparticles was investigated by tensile testing and dynamic mechanical analysis. The effects of varying amounts and types of nanofiller surface functionality were investigated to glean insight into the contributions of filler-filler and filler-matrix interactions to mechanical reinforcement in supramolecular polymer nanocomposites. MRSEC NSF DMR 0819860 (PI: Prof. N. Phuan Ong) REU Site Grant: NSF DMR-1156422 (PI: Prof. Mikko Haataja)

  20. Dynamics in Polymer Melts and Nanocomposites

    NASA Astrophysics Data System (ADS)

    Schneider, Gerald

    Intense research has led to substantial progress in the field of polymer melts and nanocomposites, both regarding the fundamental understanding and the relationship to applications. From a fundamental point of view, knowing the microscopic single chain dynamics is important. It may even lead to optimized materials ranging from the classical car tire to battery or fuel cell applications. In polymer melts, different processes, such as diffusion, reptation, contour length fluctuations, etc. occur and determine the macroscopic results, e.g. obtained by rheology. In nanocomposites confinement effects and interactions of chains with surfaces play an important role. High resolution techniques, such as small-angle neutron scattering or neutron spin echo spectroscopy are suited to explore the structure and dynamics of chains. The presentation illuminates the fundamental relationship between the microscopic dynamics and the mesoscopic properties, exploiting different experimental techniques, such as dielectric spectroscopy, rheology, neutron scattering and neutron spin echo spectroscopy.

  1. Altered phase model for polymer clay nanocomposites.

    PubMed

    Sikdar, Debashis; Pradhan, Shashindra M; Katti, Dinesh R; Katti, Kalpana S; Mohanty, Bedabibhas

    2008-05-20

    This paper describes a multiscale approach used to model polymer clay nanocomposites (PCNs) based on a new altered phase concept. Constant-force steered molecular dynamics (SMD) is used to evaluate nanomechanical properties of the constituents of intercalated clay units in PCNs, which were used in the finite element model. Atomic force microscopy and nanoindentation techniques provided additional input to the finite element method (FEM) model. FEM is used to construct a representative PCN model that simulates the composite response of intercalated clay units and the surrounding polymer matrix. From our simulations we conclude that, in order to accurately predict mechanical response of PCNs, it is necessary to take into account the molecular-level interactions between constituents of PCN, which are responsible for the enhanced nanomechanical properties of PCNs. This conclusion is supported by our previous finding that there is a change in crystallinity of polymeric phase due to the influence of intercalated clay units. The extent of altered polymeric phase is obtained from observations of a zone of the altered polymeric phase surrounding intercalated clay units in the "phase image" of PCN surface, obtained using an atomic force microscope (AFM). An accurate FEM model of PCN is constructed that incorporates the zone of the altered polymer. This model is used to estimate elastic modulus of the altered polymer. The estimated elastic modulus for the altered polymer is 4 to 5 times greater than that of pure polymer. This study indicates that it is necessary to take into account molecular interactions between constituents in nanocomposites due to the presence of altered phases, and furthermore provides us with a new direction for the modeling and design of nanocomposites.

  2. Nanostructures from Synthetic Genetic Polymers.

    PubMed

    Taylor, Alexander I; Beuron, Fabienne; Peak-Chew, Sew-Yeu; Morris, Edward P; Herdewijn, Piet; Holliger, Philipp

    2016-06-16

    Nanoscale objects of increasing complexity can be constructed from DNA or RNA. However, the scope of potential applications could be enhanced by expanding beyond the moderate chemical diversity of natural nucleic acids. Here, we explore the construction of nano-objects made entirely from alternative building blocks: synthetic genetic polymers not found in nature, also called xeno nucleic acids (XNAs). Specifically, we describe assembly of 70 kDa tetrahedra elaborated in four different XNA chemistries (2'-fluro-2'-deoxy-ribofuranose nucleic acid (2'F-RNA), 2'-fluoroarabino nucleic acids (FANA), hexitol nucleic acids (HNA), and cyclohexene nucleic acids (CeNA)), as well as mixed designs, and a ∼600 kDa all-FANA octahedron, visualised by electron microscopy. Our results extend the chemical scope for programmable nanostructure assembly, with implications for the design of nano-objects and materials with an expanded range of structural and physicochemical properties, including enhanced biostability.

  3. Functionalized graphene sheets for polymer nanocomposites.

    PubMed

    Ramanathan, T; Abdala, A A; Stankovich, S; Dikin, D A; Herrera-Alonso, M; Piner, R D; Adamson, D H; Schniepp, H C; Chen, X; Ruoff, R S; Nguyen, S T; Aksay, I A; Prud'Homme, R K; Brinson, L C

    2008-06-01

    Polymer-based composites were heralded in the 1960s as a new paradigm for materials. By dispersing strong, highly stiff fibres in a polymer matrix, high-performance lightweight composites could be developed and tailored to individual applications. Today we stand at a similar threshold in the realm of polymer nanocomposites with the promise of strong, durable, multifunctional materials with low nanofiller content. However, the cost of nanoparticles, their availability and the challenges that remain to achieve good dispersion pose significant obstacles to these goals. Here, we report the creation of polymer nanocomposites with functionalized graphene sheets, which overcome these obstacles and provide superb polymer-particle interactions. An unprecedented shift in glass transition temperature of over 40 degrees C is obtained for poly(acrylonitrile) at 1 wt% functionalized graphene sheet, and with only 0.05 wt% functionalized graphene sheet in poly(methyl methacrylate) there is an improvement of nearly 30 degrees C. Modulus, ultimate strength and thermal stability follow a similar trend, with values for functionalized graphene sheet- poly(methyl methacrylate) rivaling those for single-walled carbon nanotube-poly(methyl methacrylate) composites.

  4. Mechanical Properties of Polymer Nano-composites

    NASA Astrophysics Data System (ADS)

    Srivastava, Iti

    Thermoset polymer composites are increasingly important in high-performance engineering industries due to their light-weight and high specific strength, finding cutting-edge applications such as aircraft fuselage material and automobile parts. Epoxy is the most widely employed thermoset polymer, but is brittle due to extensive cross-linking and notch sensitivity, necessitating mechanical property studies especially fracture toughness and fatigue resistance, to ameliorate the low crack resistance. Towards this end, various nano and micro fillers have been used with epoxy to form composite materials. Particularly for nano-fillers, the 1-100 nm scale dimensions lead to fascinating mechanical properties, oftentimes proving superior to the epoxy matrix. The chemical nature, topology, mechanical properties and geometry of the nano-fillers have a profound influence on nano-composite behavior and hence are studied in the context of enhancing properties and understanding reinforcement mechanisms in polymer matrix nano-composites. Using carbon nanotubes (CNTs) as polymer filler, uniquely results in both increased stiffness as well as toughness, leading to extensive research on their applications. Though CNTs-polymer nano-composites offer better mechanical properties, at high stress amplitude their fatigue resistance is lost. In this work covalent functionalization of CNTs has been found to have a profound impact on mechanical properties of the CNT-epoxy nano-composite. Amine treated CNTs were found to give rise to effective fatigue resistance throughout the whole range of stress intensity factor, in addition to significantly enhancing fracture toughness, ductility, Young's modulus and average hardness of the nano-composite by factors of 57%, 60%, 30% and 45% respectively over the matrix as a result of diminished localized cross-linking. Graphene, a one-atom-thick sheet of atoms is a carbon allotrope, which has garnered significant attention of the scientific community and is

  5. Nanoparticle Diffusion in Polymer Nanocomposites

    SciTech Connect

    Kalathi, Jagannathan; Yamamoto, Umi; Schweizer, Kenneth; Grest, Gary S.; Kumar, Sanat

    2014-01-01

    Large-scale molecular dynamics simulations show that nanoparticle (NP) diffusivity in weakly interacting mixtures of NPs and polymer melts has two very different classes of behavior depending on their size. NP relaxation times and their diffusivities are completely described by the local, Rouse dynamics of the polymer chains for NPs smaller than the polymer entanglement mesh size. The motion of larger NPs, which are comparable to the entanglement mesh size, is significantly slowed by chain entanglements, and is not describable by the Stokes-Einstein relationship. Our results are in essentially quantitative agreement with a force-level generalized Langevin equation theory for all the NP sizes and chain lengths explored, and imply that for these lightly entangled systems, activated NP hopping is not important.

  6. Unexpected molecular weight effect in polymer nanocomposites

    SciTech Connect

    Cheng, Shiwang; Holt, Adam P.; Wang, Huiqun; Fan, Fei; Bocharova, Vera; Martin, Halie J.; Etampawala, Thusitha N.; White, Benjamin Tyler; Saito, Tomonori; Kang, Nam -Goo; Dadmun, Mark D.; Mays, Jimmy W.; Sokolov, Alexei P.

    2016-01-22

    Here, the properties of the interfacial layer between the polymer matrix and nanoparticles largely determine the macroscopic properties of polymer nanocomposites (PNCs). Although the static thickness of the interfacial layer was found to increase with the molecular weight (MW), the influence of MW on segmental relaxation and the glass transition in this layer remains to be explored. In this Letter, we show an unexpected MW dependence of the interfacial properties in PNC with attractive polymer-nanoparticle interactions: the thickness of the interfacial layer with hindered segmental relaxation decreases as MW increases, in sharp constrast to theoretical predictions. Further analyses reveal a reduction in mass density of the interfacial layer with increasing MW, which can explain these unexpected dynamic effects. Our observations call for a significant revision of the current understandings of PNCs and suggest interesting ways to tailor their properties.

  7. Unexpected molecular weight effect in polymer nanocomposites

    DOE PAGES

    Cheng, Shiwang; Holt, Adam P.; Wang, Huiqun; ...

    2016-01-22

    Here, the properties of the interfacial layer between the polymer matrix and nanoparticles largely determine the macroscopic properties of polymer nanocomposites (PNCs). Although the static thickness of the interfacial layer was found to increase with the molecular weight (MW), the influence of MW on segmental relaxation and the glass transition in this layer remains to be explored. In this Letter, we show an unexpected MW dependence of the interfacial properties in PNC with attractive polymer-nanoparticle interactions: the thickness of the interfacial layer with hindered segmental relaxation decreases as MW increases, in sharp constrast to theoretical predictions. Further analyses reveal amore » reduction in mass density of the interfacial layer with increasing MW, which can explain these unexpected dynamic effects. Our observations call for a significant revision of the current understandings of PNCs and suggest interesting ways to tailor their properties.« less

  8. Electrospun nanocomposite fibrous polymer electrolyte for secondary lithium battery applications

    NASA Astrophysics Data System (ADS)

    Padmaraj, O.; Rao, B. Nageswara; Jena, Paramananda; Venkateswarlu, M.; Satyanarayana, N.

    2014-04-01

    Hybrid nanocomposite [poly(vinylidene fluoride -co- hexafluoropropylene) (PVdF-co-HFP)/magnesium aluminate (MgAl2O4)] fibrous polymer membranes were prepared by electrospinning method. The prepared pure and nanocomposite fibrous polymer electrolyte membranes were soaked into the liquid electrolyte 1M LiPF6 in EC: DEC (1:1,v/v). XRD and SEM are used to study the structural and morphological studies of nanocomposite electrospun fibrous polymer membranes. The nanocomposite fibrous polymer electrolyte membrane with 5 wt.% of MgAl2O4 exhibits high ionic conductivity of 2.80 × 10-3 S/cm at room temperature. The charge-discharge capacity of Li/LiCoO2 coin cells composed of the newly prepared nanocomposite [(16 wt.%) PVdF-co-HFP+(5 wt.%) MgAl2O4] fibrous polymer electrolyte membrane was also studied and compared with commercial Celgard separator.

  9. Reinforcement and degradation mechanisms in polymer/inorganic nanocomposites

    NASA Astrophysics Data System (ADS)

    Bogdanova, Irina Rifkatovna

    This project accomplished the following goals: preparation of polymer/alumina nanocomposites using a single-screw extrusion approach, a systematic investigation of interfacial interactions, the mechanisms for reinforcement, and the thermal degradation and flame retardant mechanisms in polymer nanocomposites. In this work it was found that the stereochemistry of polymer macromolecules and the shapes of nanoparticles are extremely important in determining the interfacial interactions between them. Understanding of the nature of these interactions can result in a comprehensive understanding of reinforcement mechanisms in polymer nanocomposites. It was found that aromatic polymers such as polycarbonate and polystyrene have stronger interfacial interactions with needle or whisker-shaped nanoparticles than with spherical-shaped nanoparticles, while linear aliphatic polymers such as polymethylmethacrylate showed strong interactions with spherical nanoparticles. Other factors affecting the strength of interfacial interactions such as size, surface modification and concentration of nanoparticles were also studied. The thermal stability of polymer nanocomposites was studied to unravel the thermal degradation mechanisms. It was found that the chemical nature of nanoparticles plays a significant role in the thermal decomposition of polymer nanocomposites. For instance, SEM studies of polymer nanocomposites chars revealed that alumina nanoparticles moved to the surface of nanocomposites, while silica nanoparticles stayed in the body of the material, which enhances char formation. The mechanisms for the flammability in polymer/alumina nanocomposites were found to depend on the viscosity of the melt flow of nanocomposites. FT-IR, MS, and surface free energy characterization for modified alumina surfaces were done. The compatibility of polymer molecules and nanoparticles was studied on the basis of surface free energy. It was shown that modification of the alumina surface with

  10. Stimuli-Responsive Mechanically Adaptive Polymer Nanocomposites

    PubMed Central

    Shanmuganathan, Kadhiravan; Capadona, Jeffrey R.; Rowan, Stuart J.; Weder, Christoph

    2010-01-01

    A new series of biomimetic stimuli-responsive nanocomposites, which change their mechanical properties upon exposure to physiological conditions, was prepared and investigated. The materials were produced by introducing percolating networks of cellulose nanofibers or “whiskers” derived from tunicates into poly(vinyl acetate) (PVAc), poly(butyl methacrylate) (PBMA), and blends of these polymers, with the objective of determining how the hydrophobicity and glass-transition temperature (Tg) of the polymer matrix affect the water-induced mechanically dynamic behavior. Below the Tg (~60–70 °C), the incorporation of whiskers (15.1 – 16.5% v/v) modestly increased the tensile storage moduli (E′) of the neat polymers from 0.6 to 3.8 GPa (PBMA) and from 2 to 5.2 GPa (PVAc). The reinforcement was much more dramatic above Tg, where E′ increased from 1.2 to 690 MPa (PVAc) and ~1 to 1.1 GPa (PBMA). Upon exposure to physiological conditions (immersion in artificial cerebrospinal fluid, ACSF, at 37 °C) all materials displayed a decrease of E′. The most significant contrast was seen in PVAc; for example the E′ of a 16.5% v/v PVAc/whisker nanocomposite decreased from 5.2 GPa to 12.7 MPa. Only a modest modulus decrease was measured for PBMA/whisker nanocomposite; here the E′ of a 15.1% v/v PBMA/whisker nanocomposite decreased from 3.8 to 1.2 GPa. A systematic investigation revealed that the magnitude of the mechanical contrast was related to the degree of swelling with ACSF, which was shown to increase with whisker content, temperature, and polarity of the matrix (PVAc > PBMA). The mechanical morphing of the new materials can be described in the framework of both the percolation and Halpin-Kardos models for nanocomposite reinforcement, and is the result of changing interactions among the nanoparticles and plasticization of the matrix upon swelling. PMID:20305827

  11. Nanostructures from Synthetic Genetic Polymers

    PubMed Central

    Beuron, Fabienne; Peak‐Chew, Sew‐Yeu; Morris, Edward P.; Herdewijn, Piet

    2016-01-01

    Abstract Nanoscale objects of increasing complexity can be constructed from DNA or RNA. However, the scope of potential applications could be enhanced by expanding beyond the moderate chemical diversity of natural nucleic acids. Here, we explore the construction of nano‐objects made entirely from alternative building blocks: synthetic genetic polymers not found in nature, also called xeno nucleic acids (XNAs). Specifically, we describe assembly of 70 kDa tetrahedra elaborated in four different XNA chemistries (2′‐fluro‐2′‐deoxy‐ribofuranose nucleic acid (2′F‐RNA), 2′‐fluoroarabino nucleic acids (FANA), hexitol nucleic acids (HNA), and cyclohexene nucleic acids (CeNA)), as well as mixed designs, and a ∼600 kDa all‐FANA octahedron, visualised by electron microscopy. Our results extend the chemical scope for programmable nanostructure assembly, with implications for the design of nano‐objects and materials with an expanded range of structural and physicochemical properties, including enhanced biostability. PMID:26992063

  12. Polymer-Particle Nanocomposites: Size and Dispersion Effects

    NASA Astrophysics Data System (ADS)

    Moll, Joseph

    Polymer-particle nanocomposites are used in industrial processes to enhance a broad range of material properties (e.g. mechanical, optical, electrical and gas permeability properties). This dissertation will focus on explanation and quantification of mechanical property improvements upon the addition of nanoparticles to polymeric materials. Nanoparticles, as enhancers of mechanical properties, are ubiquitous in synthetic and natural materials (e.g. automobile tires, packaging, bone), however, to date, there is no thorough understanding of the mechanism of their action. In this dissertation, silica (SiO2) nanoparticles, both bare and grafted with polystyrene (PS), are studied in polymeric matrices. Several variables of interest are considered, including particle dispersion state, particle size, length and density of grafted polymer chains, and volume fraction of SiO2. Polymer grafted nanoparticles behave akin to block copolymers, and this is critically leveraged to systematically vary nanoparticle dispersion and examine its role on the mechanical reinforcement in polymer based nanocomposites in the melt state. Rheology unequivocally shows that reinforcement is maximized by the formation of a transient, but long-lived, percolating polymer-particle network with the particles serving as the network junctions. The effects of dispersion and weight fraction of filler on nanocomposite mechanical properties are also studied in a bare particle system. Due to the interest in directional properties for many different materials, different means of inducing directional ordering of particle structures are also studied. Using a combination of electron microscopy and x-ray scattering, it is shown that shearing anisotropic NP assemblies (sheets or strings) causes them to orient, one in front of the other, into macroscopic two-dimensional structures along the flow direction. In contrast, no such flow-induced ordering occurs for well dispersed NPs or spherical NP aggregates! This work

  13. Multiscale Experiments and Models for Polymer Nanocomposites

    NASA Technical Reports Server (NTRS)

    Chasiotis, Ioannis

    2005-01-01

    This report summarizes our research activities at the University of Virginia conducted under the support of this NASA research grant from March 2004 to October 2004 and provides a summary of the research to be conducted in the remaining period of the project at the University of Illinois at Urbana-Champaign (UIUC). The original research objectives will remain the same after our transition to UIUC. In the beginning of this program we completed the analysis on the graphite polymer micro and nanocomposites that were studied at NASA Langley and UVa in the summer of 2003. A publication summarizing this work was submitted in the fall of 2004 to the journal of Experimental Mechanics and the reviewer comments are currently addressed. The research program aims at understanding the local interactions between the polymer matrix and hard reinforcement in polymer nanocomposites (PNCs). The materials selected for this study were PNCs with different fillers (14nm silica nanospheres or nanoclays) and volume fractions (0.5%, 1%, 2% and 5%).

  14. Electrically Conductive Metal Nanowire Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Luo, Xiaoxiong

    This thesis investigates electrically conductive polymer nanocomposites formulated with metal nanowires for electrostatic discharge and electromagnetic interference shielding. Copper nanowires (CuNWs) of an average length of 1.98 mum and diameter of 25 +/- 4 nm were synthesized. The oxidation reaction of the CuNWs in air can be divided into two stages at weight of 111.2% on TGA curves. The isoconversional activation energies determined by Starink method were used to fit the different master plots. Johnson-Mehl-Avrami (JMA) equation gave the best fit. The surface atoms of the CuNWs are the sites for the random nucleation and the crystallite strain in the CuNWs is the driving force for the growth of nuclei mechanism during the oxidation process. To improve the anti-oxidation properties of the CuNWs, silver was coated onto the surface of the CuNWs in Ag-amine solution. The prepared silver coated CuNWs (AgCuNWs) with silver content of 66.52 wt. %, diameter of 28--33 nm exhibited improved anti-oxidation behavior. The electrical resistivity of the AgCuNW/low density polyethylene (LDPE) nanocomposites is lower than that of the CuNW/LDPE nanocomposites with the same volume percentage of fillers. The nanocomposites formulated with CuNWs and polyethylenes (PEs) were compared to study the different interaction between the CuNWs and the different types of PE matrices. The electrical conductivity of the different PE matrices filled with the same concentrations of CuNWs correlated well with the level of the CuNW dispersion. The intermolecular force and entanglement resulting from the different macromolecular structures such as molecular weight and branching played an important role in the dispersion, electrical properties and rheological behaviour of the CuNW/PE nanocomposites. Ferromagnetic polycrystalline nickel nanowires (NiNWs) were synthesized with uniform diameter of ca. 38 nm and an average length of 2.68 mum. The NiNW linear low density polyethylene (LLDPE

  15. Viscoelastic Analysis of Thermally Stiffening Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Ehlers, Andrew; Rende, Deniz; Senses, Erkan; Akcora, Pinar; Ozisik, Rahmi

    Poly(ethylene oxide), PEO, filled with silica nanoparticles coated with poly(methyl methacrylate), PMMA, was shown to present thermally stiffening behavior above the glass transition temperature of both PEO and PMMA. In the current study, the viscoelastic beahvior of this nanocomposite system is investigated via nanoindenation experiments to complement on going rheological studies. Results were compared to neat polymers, PEO and PMMA, to understand the effect of coated nanoparticles. This material is based upon work supported by the National Science Foundation under Grant No. CMMI-1538730.

  16. Organic/Inorganic Hybrid Polymer/Clay Nanocomposites

    NASA Technical Reports Server (NTRS)

    Park, Cheol; Connell, John W.; Smith, Joseph G., Jr.

    2003-01-01

    A novel class of polymer/clay nanocomposites has been invented in an attempt to develop transparent, lightweight, durable materials for a variety of aerospace applications. As their name suggests, polymer/ clay nanocomposites comprise organic/ inorganic hybrid polymer matrices containing platelet-shaped clay particles that have sizes of the order of a few nanometers thick and several hundred nanometers long. Partly because of their high aspect ratios and high surface areas, the clay particles, if properly dispersed in the polymer matrix at a loading level of 1 to 5 weight percent, impart unique combinations of physical and chemical properties that make these nanocomposites attractive for making films and coatings for a variety of industrial applications. Relative to the unmodified polymer, the polymer/ clay nanocomposites may exhibit improvements in strength, modulus, and toughness; tear, radiation, and fire resistance; and lower thermal expansion and permeability to gases while retaining a high degree of optical transparency.

  17. Synthetic polymer-layer silicate clay composites

    SciTech Connect

    Carrado, K.A.; Elder, D.L.; Thiyagarajan, P.

    1995-07-01

    Synthetic hectorites were hydrothermally crystallized with direct incorporation of water-soluble polyvinyl alcohol (PVA), a cationic polymer poly(dimethyl diallyl ammonium chloride) (PDDA), and two cellulosic polymers: hydroxypropyl methylcellulose (HPMC) and hydroxyethyl cellulose (HEC). The molecular weight of polyvinyl alcohols had little effect on the success of hydrothermal hectorite synthesis, d-spacing, or amount of polymer incorporated; the basal spacings range from 19.5 {angstrom} to 20.8 {angstrom} and the percent of polymer incorporated ranges from 20.4 wt% to 23.0 wt%. Synthetic PDDA-hectorite displays the lowest d-spacing at 15.8 {angstrom}, and less cationic PDDA is incorporated into hectorite (7.8 wt% organic) than the other neutral polymers (17.8-23.0 wt% organic). The basal spacing for synthetic HPMC-hectorite is the largest at 25.2 {angstrom}. Small angle neutron scattering was used to further examine the PVA-clay systems.

  18. Self-assembled polymer nanocomposites and their networks

    NASA Astrophysics Data System (ADS)

    Patil, Nitin Vikas

    This dissertation describes new routes to synthesize polymer nanocomposite networks via self-assembly. Polymerizable structure directing agents (referred to as surfmers) obtained by end-group functionalization preserves the structure-directing capabilities of the surfactant for templating ordered mesoporous silica particle growth, while simultaneously generating a reactive matrix for polymer network formation through reactive end groups in the presence of intimately mixed mesoporous silicates. A combination of small angle X-ray scattering, surface area, and microscopy experiments on mesoporous silica indicated the structure directing capabilities of surfmers. Free-radical polymerization of the surfmer leads to novel crosslinked nanocomposites networks. Multiple experiments, including gel permeation chromatography, swelling, and solid state NMR experiments on polymer nanocomposites gave evidence of the polymerization of surfmer leading to formation of crosslink networks. Polymer nanocomposites with varied silica content were prepared. Effects of silica content on polymer nanocomposites were studied on rheometer. Results obtained from rheological experiments indicate that the storage (G') and loss modulus (G") increases with increase in the content of mesoporous silica. In this way, the nanocomposites networks obtained via self-assembly shows independent behavior with respect to frequency in rheological experiments. Additionally, this self-assembled route was extended to synthesize biodegradable and biocompatible polymer nanocomposites networks. The nanocomposite networks obtained with 15% of silica content showed the increase in storage modulus by two orders of magnitude in rheological experiments.

  19. Advanced materials based on polymer blends/polymer blend nanocomposites

    NASA Astrophysics Data System (ADS)

    Shikaleska, A. V.; Pavlovska, F. P.

    2012-09-01

    Processability, morphology, mechanical properties and rheological behavior of poly(vinylchloride) (PVC)/poly(ethylmethacrylate) (PEMA) blends and PVC/PEMA/montmorillonite (MMT) composites, prepared by melt processing in a brabender mixer, were studied. Samples were characterized using SEM, mechanical testing, DMTA and a parallel plate rheometer. Plastograms show that there is noticeable drop of fusion times and increase in melt viscosity torque of both, polymer blend and polymer blend nanocomposite, in comparison with those of neat PVC. SEM images show that homogenous dispersions are obtained. Tensile tests indicate that PVC/PEMA and PVC/PEMA/MMT samples have greater tensile strength and elastic modulus and lower elongation compared to PVC. When solid viscoelastic properties are considered (DMTA), slightly higher storage moduli are obtained whereas more prominent increase of storage modulus is observed when nanoclay particles are added in a PVC/PEMA matrix. From the calculated area of tandelta peak of all tested samples, nanocomposites exhibit the lowest damping behavior. Oscillatory measurements in a molten state were used for determining the frequency dependencies of storage G' and loss G" moduli. It was found that G" curves of neat PVC lie above those of G' suggesting that PVC behaves like viscoelastic liquid. Similar results, but with significantly higher values of G' and G" over the whole frequency range for PVC/PEMA blends were obtained. Steady shear measurements show that the presence of PEMA and nanoclay particles increases the shear stress and shear viscosity of neat PVC. In order to define the rheological equations of state the three material functions were determined. According to these functions all samples exhibit shear thinning behavior and the curves obey the power law equation. As rheological behaviour was found to be strongly dependent on blend's micro and macro structure and it is one of the main factors defining the end properties, attempt was

  20. Thermal Imaging Processes of Polymer Nanocomposite Coatings

    NASA Astrophysics Data System (ADS)

    Meth, Jeffrey

    2015-03-01

    Laser induced thermal imaging (LITI) is a process whereby infrared radiation impinging on a coating on a donor film transfers that coating to a receiving film to produce a pattern. This talk describes how LITI patterning can print color filters for liquid crystal displays, and details the physical processes that are responsible for transferring the nanocomposite coating in a coherent manner that does not degrade its optical properties. Unique features of this process involve heating rates of 107 K/s, and cooling rates of 104 K/s, which implies that not all of the relaxation modes of the polymer are accessed during the imaging process. On the microsecond time scale, the polymer flow is forced by devolatilization of solvents, followed by deformation akin to the constrained blister test, and then fracture caused by differential thermal expansion. The unique combination of disparate physical processes demonstrates the gamut of physics that contribute to advanced material processing in an industrial setting.

  1. Synthetic biodegradable polymers for orthopaedic applications.

    PubMed

    Behravesh, E; Yasko, A W; Engel, P S; Mikos, A G

    1999-10-01

    Synthetic biodegradable polymers offer an alternative to the use of autografts, allografts, and nondegradable materials for bone replacement. They can be synthesized with tailored mechanical and degradative properties. They also can be processed to porous scaffolds with desired pore morphologic features conducive to tissue ingrowth. Moreover, functionalized polymers can modulate cellular function and induce tissue ingrowth. This review focuses on four classes of polymers that hold promise for orthopaedic applications: poly alpha-hydroxy esters, polyphosphazenes, polyanhydrides, and polypropylene fumarate crosslinked networks.

  2. Space charge effects on the dielectric response of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Shen, Zhong-Hui; Wang, Jian-Jun; Zhang, Xin; Lin, Yuanhua; Nan, Ce-Wen; Chen, Long-Qing; Shen, Yang

    2017-08-01

    Adding high-κ ceramic nanoparticles into polymers is a general strategy to improve the performances in energy storage. Classic effective medium theories may fail to predict the effective permittivity in polymer nanocomposites wherein the space charge effects are important. In this work, a computational model is developed to understand the space charge effects on the frequency-dependent dielectric properties including the real permittivity and the loss for polymer nanocomposites with both randomly distributed and aggregated nanoparticle fillers. It is found that the real permittivity of the SrTiO3/polyethylene (12% SrTiO3 in volume fraction) nanocomposite can be increased to as high as 60 when there is nanoparticle aggregation and the ion concentration in the bulk polymer is around 1016 cm-3. This model can be employed to quantitatively predict the frequency-dependent dielectric properties for polymer nanocomposites with arbitrary microstructures.

  3. Nanomechanics of nanocomposite systems: Experimental studies in bone, seashells and synthetic nanocomposites using nanoindentation and atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Mohanty, Bedabibhas

    changes along the thickness of bone. Also investigated are nanomechanical properties in synthetic nanocomposites composed of nanoclays and polymers (nylon 6). The novel experiments conducted in this work describe quantitatively the extent of the alteration zone of polymers around nanosized clays to be about 25 nm using phase imaging in atomic force microscopy. These experiments provided valuable input for the development of multiscale models of polymer clay composite systems.

  4. Ferroelectric polymer nanocomposites for room-temperature electrocaloric refrigeration.

    PubMed

    Zhang, Guangzu; Li, Qi; Gu, Haiming; Jiang, Shenglin; Han, Kuo; Gadinski, Matthew R; Haque, Md Amanul; Zhang, Qiming; Wang, Qing

    2015-02-25

    Solution-processable ferroelectric polymer nanocomposites are developed as a new form of electrocaloric materials that can be effectively operated under both modest and high electric fields at ambient temperature. By integrating the complementary properties of the constituents, the nanocomposites exhibit state-of-the-art cooling energy densities. Greatly improved thermal conductivity also yields superior cooling power densities validated by finite volume simulations.

  5. Universal Scaling of Polymer Diffusion in Nanocomposites

    NASA Astrophysics Data System (ADS)

    Choi, Jihoon; Hore, Michael J. A.; Meth, Jeffrey S.; Clarke, Nigel; Winey, Karen I.; Composto, Russell J.

    2013-03-01

    The tracer diffusion of deuterated polystyrene (dPS) is measured in a polystyrene (PS) nanocomposite containing hard and soft silica nanoparticles (NPs). The soft NPs are grafted with a PS brush (87 kg/mol). The matrix for both NPs is PS (160 kg/mol). The diffusion coefficients for dPS (23 - 1,866 kg/mol) decrease as the hard and soft NP volume fractions increase. To accurately determine the interparticle distances (ID) relevant to each dPS (M) diffusing through the PS(160k):soft NP matrix, self consistent field theory and small angle neutron scattering studies were performed; both theory and experiment show that short dPS chains can deeply penetrate the brush, whereas longer dPS chains only penetrate the periphery and mainly remain in the matrix. The reduced diffusion coefficient (D/D0), plotted against the confinement parameter, namely ID relative to tracer size (2Rg), collapses onto a master curve independent of NP type. These experiments demonstrate that polymer diffusion in nanocomposites is captured by the confinement parameter over an extremely wide range of ID/2Rg and, hopefully, motivate new models to capture the dynamics in confined (ID/2Rg < 10) regimes.

  6. Smart Polymer/Carbon Nanotube Nanocomposites and Their Electrorheological Response

    PubMed Central

    Zhang, Ke; Choi, Hyoung Jin

    2014-01-01

    This review article summarizes the preparation of polymer/carbon nanotube (CNT) nanocomposites and their applications as electrorheological (ER) fluids. These ER fluids exhibited a controllable electro-response under an applied electric field due to the presence of well-dispersed CNTs. The background, morphology, preparations, and characteristics of these materials are discussed, specifically focusing on the various approaches in the preparation of polymer/CNT nanocomposites, morphology, and their effects on the ER characteristics. PMID:28788624

  7. Silicon oxide colloidal/polymer nanocomposite films

    SciTech Connect

    Wang Haifeng; Cao Wenwu; Zhou, Q.F.; Shung, K. Kirk; Huang, Y.H.

    2004-12-13

    The quarter-wavelength ({lambda}/4) acoustic matching layer, a vital component in medical ultrasonic transducer, can bridge the large acoustic impedance mismatch between the piezoelectric material and the human body. Composite materials are widely used as matching materials in order to cover the wide acoustic impedance range that cannot be accomplished by using a single-phase material. At high frequencies (>50 MHz), the {lambda}/4 matching layers become extremely thin so that the fabrication of homogeneous composite material matching layers becomes very challenging. A method is reported in this letter to fabricate sol-gel silicon oxide colloidal/polymer composite film on silicon substrate, in which the particle size of silicon oxide colloidal is between 10 and 40 nm. The acoustic impedance of the nanocomposite films versus aging temperature has been measured at the desired operating frequency.

  8. Silicon oxide colloidal/polymer nanocomposite films

    NASA Astrophysics Data System (ADS)

    Wang, Haifeng; Cao, Wenwu; Zhou, Q. F.; Shung, K. Kirk; Huang, Y. H.

    2004-12-01

    The quarter-wavelength (λ/4) acoustic matching layer, a vital component in medical ultrasonic transducer, can bridge the large acoustic impedance mismatch between the piezoelectric material and the human body. Composite materials are widely used as matching materials in order to cover the wide acoustic impedance range that cannot be accomplished by using a single-phase material. At high frequencies (>50MHz), the λ /4 matching layers become extremely thin so that the fabrication of homogeneous composite material matching layers becomes very challenging. A method is reported in this letter to fabricate sol-gel silicon oxide colloidal/polymer composite film on silicon substrate, in which the particle size of silicon oxide colloidal is between 10 and 40 nm. The acoustic impedance of the nanocomposite films versus aging temperature has been measured at the desired operating frequency.

  9. Polyhedral Oligomeric Silsesquioxane (POSS)-Containing Polymer Nanocomposites

    PubMed Central

    Ayandele, Ebunoluwa; Sarkar, Biswajit; Alexandridis, Paschalis

    2012-01-01

    Hybrid materials with superior structural and functional properties can be obtained by incorporating nanofillers into polymer matrices. Polyhedral oligomeric silsesquioxane (POSS) nanoparticles have attracted much attention recently due to their nanometer size, the ease of which these particles can be incorporated into polymeric materials and the unique capability to reinforce polymers. We review here the state of POSS-containing polymer nanocomposites. We discuss the influence of the incorporation of POSS into polymer matrices via chemical cross-linking or physical blending on the structure of nanocomposites, as affected by surface functional groups, and the POSS concentration. PMID:28348318

  10. Multifunctional polymer nanocomposites with uniaxially aligned liquid crystal polymer fibrils and graphene nanoplatelets

    NASA Astrophysics Data System (ADS)

    Leung, S. N.; Khan, M. O.; Naguib, H.; Dawson, F.

    2014-02-01

    Polymer nanocomposites have actively been studied to replace metals in different emerging applications because of their light weight, superior manufacturability, and low processing cost. For example, extensive research efforts have been made to develop advanced thermally conductive polymer nanocomposites, with good processability, for heat management applications. In this study, liquid crystal polymer (LCP)-based nanocomposites have shown to possess much higher effective thermal conductivity (keff) (i.e., as high as 2.58 W/m K) than neat polymers (i.e., ˜0.2-0.4 W/m K). The fibrillation of LCP in LCP-graphene nanoplatelet (GNP) nanocomposites also demonstrated more pronounced increase in keff than that of polyphenylene sulfide (PPS)-GNP nanocomposites. Furthermore, ultra-drawing of LCP-GNP nanocomposite led to additional increase in the nanocomposite's keff because of the alignments of LCP fibrils and the embedded GNP. Experimental results also revealed that, unlike keff, the electrical conductivity (σ) of nanocomposites was unaffected by the types of polymer matrix. This exhibited that the keff and σ were promoted by different mechanisms, suggesting a potential route to tailor polymer nanocomposite's keff and σ independently.

  11. Microscopic Chain Motion in Polymer Nanocomposites with Dynamically Asymmetric Interphases

    PubMed Central

    Senses, Erkan; Faraone, Antonio; Akcora, Pinar

    2016-01-01

    Dynamics of the interphase region between matrix and bound polymers on nanoparticles is important to understand the macroscopic rheological properties of nanocomposites. Here, we present neutron scattering investigations on nanocomposites with dynamically asymmetric interphases formed by a high-glass transition temperature polymer, poly(methyl methacrylate), adsorbed on nanoparticles and a low-glass transition temperature miscible matrix, poly(ethylene oxide). By taking advantage of selective isotope labeling of the chains, we studied the role of interfacial polymer on segmental and collective dynamics of the matrix chains from subnanoseconds to 100 nanoseconds. Our results show that the Rouse relaxation remains unchanged in a weakly attractive composite system while the dynamics significantly slows down in a strongly attractive composite. More importantly, the chains disentangle with a remarkable increase of the reptation tube size when the bound polymer is vitreous. The glassy and rubbery states of the bound polymer as temperature changes underpin the macroscopic stiffening of nanocomposites. PMID:27457056

  12. Microscopic Chain Motion in Polymer Nanocomposites with Dynamically Asymmetric Interphases

    NASA Astrophysics Data System (ADS)

    Senses, Erkan; Faraone, Antonio; Akcora, Pinar

    2016-07-01

    Dynamics of the interphase region between matrix and bound polymers on nanoparticles is important to understand the macroscopic rheological properties of nanocomposites. Here, we present neutron scattering investigations on nanocomposites with dynamically asymmetric interphases formed by a high-glass transition temperature polymer, poly(methyl methacrylate), adsorbed on nanoparticles and a low-glass transition temperature miscible matrix, poly(ethylene oxide). By taking advantage of selective isotope labeling of the chains, we studied the role of interfacial polymer on segmental and collective dynamics of the matrix chains from subnanoseconds to 100 nanoseconds. Our results show that the Rouse relaxation remains unchanged in a weakly attractive composite system while the dynamics significantly slows down in a strongly attractive composite. More importantly, the chains disentangle with a remarkable increase of the reptation tube size when the bound polymer is vitreous. The glassy and rubbery states of the bound polymer as temperature changes underpin the macroscopic stiffening of nanocomposites.

  13. Rapid synthesis of flexible conductive polymer nanocomposite films

    NASA Astrophysics Data System (ADS)

    Blattmann, C. O.; Sotiriou, G. A.; Pratsinis, S. E.

    2015-03-01

    Polymer nanocomposite films with nanoparticle-specific properties are sought out in novel functional materials and miniaturized devices for electronic and biomedical applications. Sensors, capacitors, actuators, displays, circuit boards, solar cells, electromagnetic shields and medical electrodes rely on flexible, electrically conductive layers or films. Scalable synthesis of such nanocomposite films, however, remains a challenge. Here, flame aerosol deposition of metallic nanosliver onto bare or polymer-coated glass substrates followed by polymer spin-coating on them leads to rapid synthesis of flexible, free-standing, electrically conductive nanocomposite films. Their electrical conductivity is determined during their preparation and depends on substrate composition and nanosilver deposition duration. Accordingly, thin (<500 nm) and flexible nanocomposite films are made having conductivity equivalent to metals (e.g. 5 × 104 S cm-1), even during repetitive bending.

  14. Synthetic organo- and polymer- clays : preparation, characterization, and materials applications.

    SciTech Connect

    Carrado, K. A.; Chemistry

    2000-01-01

    We have over the years developed and patented a general technique for the hydrothermal synthesis of clay minerals in the presence of organic, organometallic, and polymeric intercalants. This review will summarize the details for crystallization of modified hectorites along with their characterization and materials applications. Among the several potential uses of these synthetic materials, there are two important applications concerning catalysis and composites. The fate of the template dictates which of these applications is pertinent. First, if the organic molecule or polymer is used with the intention of acting as templates of pore structure, then the organic template is removed after the modified clay has been crystallized. Upon template removal, the now porous materials are examined for their use as potential catalysts and catalyst supports. We have recently proven a correlation between catalyst pore size in the mesoporous range and the size and concentration of a polymeric template that is used. Preliminary hydrodesulfurization catalytic results have been obtained using these materials. If, on the other hand, intercalants are allowed to remain as a part of the structure, then a distinctive class of organic-inorganic composites becomes possible. When polymeric intercalants are used, especially at high concentrations, the materials have relevance to nanocomposite applications. Work in this area has focused on incorporating polymers at higher than 85 wt.% of the nanocomposite.

  15. Synthesis and characterization of polymer matrix nanocomposites and their components

    NASA Astrophysics Data System (ADS)

    Burnside, Shelly Dawn

    Herein we present synthesis schemes and characterization results for polymer matrix nanocomposite reinforced with organically modified layered silicates. These host materials with ultrafine dimensions are promising candidates for polymer and have been previously shown to yield substantial property enhancements at low silicate loadings due to their extreme geometry. Siloxane nanocomposites with a variety of nanostructures were formed. Thermal stability, solvent uptake and moduli of the nanocomposites were explores. Exfoliated nanocomposites displayed enhanced properties when compared to unreinforced siloxanes, and at lower volume fraction filler than in conventional composites. Large amounts of bound polymer, polymer affected by the silicate, were found in exfoliated nanocomposites as a result of the extreme geometry of the layered silicate. This bound polymer was related to the dramatic property enhancements in the nanocomposites. The behavior of these nanocomposites is compared to behavior expected from traditional models developed for conventional composites and model elastomeric networks. A lightly brominated polymer has been intercalated into a single crystal of organically exchanged vermiculite. The intercalation was followed using x-ray diffraction by monitoring the gallery height of the vermiculite host. Rutherford Backscattering Spectroscopy, used to confirm polymer intercalation, showed a constant bromine content in the direction normal to the layers. Atomic Force Microscopy images of a cleaved polymer-intercalated crystal showed raised hemispheres on an otherwise flat background. The hemispheres consist of single chains or aggregates of 3-40 polymer chains resulting from relaxations following cleaving. Three component or Hansen solubility parameters (delta) of organically modified layered silicates, the reinforcing agent in polymer matrix nanocomposites presented herein, have been determined. Two experimental techniques, temporal turbidimetry and

  16. Modular-based multiscale modeling on viscoelasticity of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Li, Ying; Liu, Zeliang; Jia, Zheng; Liu, Wing Kam; Aldousari, Saad M.; Hedia, Hassan S.; Asiri, Saeed A.

    2016-10-01

    Polymer nanocomposites have been envisioned as advanced materials for improving the mechanical performance of neat polymers used in aerospace, petrochemical, environment and energy industries. With the filler size approaching the nanoscale, composite materials tend to demonstrate remarkable thermomechanical properties, even with addition of a small amount of fillers. These observations confront the classical composite theories and are usually attributed to the high surface-area-to-volume-ratio of the fillers, which can introduce strong nanoscale interfacial effect and relevant long-range perturbation on polymer chain dynamics. Despite decades of research aimed at understanding interfacial effect and improving the mechanical performance of composite materials, it is not currently possible to accurately predict the mechanical properties of polymer nanocomposites directly from their molecular constituents. To overcome this challenge, different theoretical, experimental and computational schemes will be used to uncover the key physical mechanisms at the relevant spatial and temporal scales for predicting and tuning constitutive behaviors in silico, thereby establishing a bottom-up virtual design principle to achieve unprecedented mechanical performance of nanocomposites. A modular-based multiscale modeling approach for viscoelasticity of polymer nanocomposites has been proposed and discussed in this study, including four modules: (A) neat polymer toolbox; (B) interphase toolbox; (C) microstructural toolbox and (D) homogenization toolbox. Integrating these modules together, macroscopic viscoelasticity of polymer nanocomposites could be directly predicted from their molecular constituents. This will maximize the computational ability to design novel polymer composites with advanced performance. More importantly, elucidating the viscoelasticity of polymer nanocomposites through fundamental studies is a critical step to generate an integrated computational material

  17. Modular-based multiscale modeling on viscoelasticity of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Li, Ying; Liu, Zeliang; Jia, Zheng; Liu, Wing Kam; Aldousari, Saad M.; Hedia, Hassan S.; Asiri, Saeed A.

    2017-02-01

    Polymer nanocomposites have been envisioned as advanced materials for improving the mechanical performance of neat polymers used in aerospace, petrochemical, environment and energy industries. With the filler size approaching the nanoscale, composite materials tend to demonstrate remarkable thermomechanical properties, even with addition of a small amount of fillers. These observations confront the classical composite theories and are usually attributed to the high surface-area-to-volume-ratio of the fillers, which can introduce strong nanoscale interfacial effect and relevant long-range perturbation on polymer chain dynamics. Despite decades of research aimed at understanding interfacial effect and improving the mechanical performance of composite materials, it is not currently possible to accurately predict the mechanical properties of polymer nanocomposites directly from their molecular constituents. To overcome this challenge, different theoretical, experimental and computational schemes will be used to uncover the key physical mechanisms at the relevant spatial and temporal scales for predicting and tuning constitutive behaviors in silico, thereby establishing a bottom-up virtual design principle to achieve unprecedented mechanical performance of nanocomposites. A modular-based multiscale modeling approach for viscoelasticity of polymer nanocomposites has been proposed and discussed in this study, including four modules: (A) neat polymer toolbox; (B) interphase toolbox; (C) microstructural toolbox and (D) homogenization toolbox. Integrating these modules together, macroscopic viscoelasticity of polymer nanocomposites could be directly predicted from their molecular constituents. This will maximize the computational ability to design novel polymer composites with advanced performance. More importantly, elucidating the viscoelasticity of polymer nanocomposites through fundamental studies is a critical step to generate an integrated computational material

  18. Graphene Synthesis & Graphene/Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Liao, Ken-Hsuan

    -layered free standing TRG. This indicates TRG is mono-layer-dispersed in the matrix polymer. How graphene/polymer nanocomposite glass transition temperatures ( Tg) vary was investigated in this study. We measured Tg in PMMA. We used isotactic PMMA (i-PMMA) and syndiotactic-rich atactic PMMA (a-PMMA) to make TRG/PMMA nanocomposites using solvent blending and in situ polymerization in order to investigate the stereo-regularity and processing effects on the Tg. A T g increase was found in i-PMMA and in situ PMMA but not in a-PMMA. The results can be explained by the thin film confinement effect of polymer. We attribute the Tg increase to both a higher interaction density and a stronger hydrogen bonding at the interfaces. We have studied the elastic modulus of graphene oxide with various oxygen content. We used in situ AFM nano-indentation to measure the influence of oxygen on the elastic modulus of graphene oxide with various carbon/oxygen (C/O) ratios. The results show that chemical reduction (lower oxygen contents) decreases the elastic modulus of graphene oxide. We speculate that chemical reduction of oxygen atoms of epoxy groups on graphene oxide surface removes the bridging effect between carbon atoms, which leads to more flexible sheets. (Abstract shortened by UMI.).

  19. Synthetic magnetoelectric coupling in a nanocomposite multiferroic

    DOE PAGES

    Jain, P.; Wang, Q.; Roldan, M.; ...

    2015-03-13

    Given the paucity of single phase multiferroic materials (with large ferromagnetic moment), composite systems seem an attractive solution to realize magnetoelectric coupling between ferromagnetic and ferroelectric order parameters. Despite having antiferromagnetic order, BiFeO3 (BFO) has nevertheless been a key material due to excellent ferroelectric properties at room temperature. We studied a superlattice composed of 8 repetitions of 6 unit cells of La0.7Sr0.3MnO3 (LSMO) grown on 5 unit cells of BFO. Significant net uncompensated magnetization in BFO, an insulating superlattice is demonstrated using polarized neutron reflectometry. Remarkably, the magnetization enables magnetic field to change the dielectric properties of the superlattice, whichmore » we cite as an example of synthetic magnetoelectric coupling. Finally, controlled creation of magnetic moment in BFO is a much needed path toward design and implementation of integrated oxide devices for next generation magnetoelectric data storage platforms.« less

  20. Synthetic magnetoelectric coupling in a nanocomposite multiferroic

    PubMed Central

    Jain, P.; Wang, Q.; Roldan, M.; Glavic, A.; Lauter, V.; Urban, C.; Bi, Z.; Ahmed, T.; Zhu, J.; Varela, M.; Jia, Q. X.; Fitzsimmons, M. R.

    2015-01-01

    Given the paucity of single phase multiferroic materials (with large ferromagnetic moment), composite systems seem an attractive solution to realize magnetoelectric coupling between ferromagnetic and ferroelectric order parameters. Despite having antiferromagnetic order, BiFeO3 (BFO) has nevertheless been a key material due to excellent ferroelectric properties at room temperature. We studied a superlattice composed of 8 repetitions of 6 unit cells of La0.7Sr0.3MnO3 (LSMO) grown on 5 unit cells of BFO. Significant net uncompensated magnetization in BFO, an insulating superlattice, is demonstrated using polarized neutron reflectometry. Remarkably, the magnetization enables magnetic field to change the dielectric properties of the superlattice, which we cite as an example of synthetic magnetoelectric coupling. Importantly, controlled creation of magnetic moment in BFO is a much needed path toward design and implementation of integrated oxide devices for next generation magnetoelectric data storage platforms. PMID:25766205

  1. Enhanced Dispersion in Polymer Nanocomposites by Optimized Hydrogen Bonding

    NASA Astrophysics Data System (ADS)

    Dadmun, Mark; Rasheed, Asif; Britt, Phillip; Geohegan, David; Ivanov, Ilia; Chae, Han Gi; Kumar, Satish

    2006-03-01

    The dispersion of the minor phase in a multi-component polymer system can readily lead to nonlinear enhancement of material properties. In any multi-component polymer system, including polymer nanocomposites, understanding and control of the dispersion of the nanofiller in the polymer matrix is critical to rationally design and create a useful new material. This presentation will discuss the work in our group to optimize the specific interactions between components of polymer nanocomposites. We will discuss results that indicate that the optimization of intermolecular interaction between components provides a controllable mechanism to improve the dispersion of nanoscale fillers in a polymer matrix and that the improved dispersion correlates directly to improved thermal, mechanical, and electrical properties.

  2. Electrospun nanocomposite fibrous polymer electrolyte for secondary lithium battery applications

    SciTech Connect

    Padmaraj, O.; Rao, B. Nageswara; Jena, Paramananda; Satyanarayana, N.; Venkateswarlu, M.

    2014-04-24

    Hybrid nanocomposite [poly(vinylidene fluoride -co- hexafluoropropylene) (PVdF-co-HFP)/magnesium aluminate (MgAl{sub 2}O{sub 4})] fibrous polymer membranes were prepared by electrospinning method. The prepared pure and nanocomposite fibrous polymer electrolyte membranes were soaked into the liquid electrolyte 1M LiPF{sub 6} in EC: DEC (1:1,v/v). XRD and SEM are used to study the structural and morphological studies of nanocomposite electrospun fibrous polymer membranes. The nanocomposite fibrous polymer electrolyte membrane with 5 wt.% of MgAl{sub 2}O{sub 4} exhibits high ionic conductivity of 2.80 × 10{sup −3} S/cm at room temperature. The charge-discharge capacity of Li/LiCoO{sub 2} coin cells composed of the newly prepared nanocomposite [(16 wt.%) PVdF-co-HFP+(5 wt.%) MgAl{sub 2}O{sub 4}] fibrous polymer electrolyte membrane was also studied and compared with commercial Celgard separator.

  3. Ceramic Nanocomposites from Tailor-Made Preceramic Polymers

    PubMed Central

    Mera, Gabriela; Gallei, Markus; Bernard, Samuel; Ionescu, Emanuel

    2015-01-01

    The present Review addresses current developments related to polymer-derived ceramic nanocomposites (PDC-NCs). Different classes of preceramic polymers are briefly introduced and their conversion into ceramic materials with adjustable phase compositions and microstructures is presented. Emphasis is set on discussing the intimate relationship between the chemistry and structural architecture of the precursor and the structural features and properties of the resulting ceramic nanocomposites. Various structural and functional properties of silicon-containing ceramic nanocomposites as well as different preparative strategies to achieve nano-scaled PDC-NC-based ordered structures are highlighted, based on selected ceramic nanocomposite systems. Furthermore, prospective applications of the PDC-NCs such as high-temperature stable materials for thermal protection systems, membranes for hot gas separation purposes, materials for heterogeneous catalysis, nano-confinement materials for hydrogen storage applications as well as anode materials for secondary ion batteries are introduced and discussed in detail. PMID:28347023

  4. Piezoresistive Strain Sensors Made from Carbon Nanotubes Based Polymer Nanocomposites

    PubMed Central

    Alamusi; Hu, Ning; Fukunaga, Hisao; Atobe, Satoshi; Liu, Yaolu; Li, Jinhua

    2011-01-01

    In recent years, nanocomposites based on various nano-scale carbon fillers, such as carbon nanotubes (CNTs), are increasingly being thought of as a realistic alternative to conventional smart materials, largely due to their superior electrical properties. Great interest has been generated in building highly sensitive strain sensors with these new nanocomposites. This article reviews the recent significant developments in the field of highly sensitive strain sensors made from CNT/polymer nanocomposites. We focus on the following two topics: electrical conductivity and piezoresistivity of CNT/polymer nanocomposites, and the relationship between them by considering the internal conductive network formed by CNTs, tunneling effect, aspect ratio and piezoresistivity of CNTs themselves, etc. Many recent experimental, theoretical and numerical studies in this field are described in detail to uncover the working mechanisms of this new type of strain sensors and to demonstrate some possible key factors for improving the sensor sensitivity. PMID:22346667

  5. STIR: Microwave Response of Carbon Nanotubes in Polymer Nanocomposite Welds

    DTIC Science & Technology

    2016-01-28

    STIR: RDRL-ROE-M: Microwave Response of Carbon Nanotubes in Polymer Nanocomposite Welds Thrust 1 of the STIR project examines the heat response of...polymer composites loaded with carbon nanotubes (CNTs) to microwave irradiation. This involves (1) a study of how CNT loading affects dielectric...27709-2211 polymer, carbon nanotube , manufacturing, diffusion, heating, microwave REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT NUMBER(S

  6. Polymer-ceramic nanocomposites for applications in the bone surgery

    NASA Astrophysics Data System (ADS)

    Stodolak, E.; Gadomska, K.; Lacz, A.; Bogun, M.

    2009-01-01

    The subject of this work was preparation and investigation of properties of a nanocomposite material based on polymer matrix modified with nanometric silica particles (SiO2). The composite matrix consisted of resorbable P(L/DL)LA polymer with certified biocompatibility. Nanometric silica was introduced into the matrix by means of ultrasonic homogenisation and/or mechanical stirring. The silica was introduced directly e.g. as nanoparticles or inside calcium alginate fibres which contained 3 wt.% of amorphous SiO2. Proper dispersion of nano-filliers was confirmed by means of thermal analysis (TG/DTA, DSC). It was observed, that the presence of inorganic nanoparticles influenced several surface parameters of the nanocomposites i.e. hydrophility (a decrease of surface energy) and topography (both in micro- and nano-scale). Additionally, the nanocomposites exhibited enhanced mechanical properties (Young's modulus, tensile strength) compared to the pure polymer. The nanocomposites were bioactive materials (SBF/3 days/37oC). Biological tests (MTT test) showed a good viability of human osteoblasts (hFOB 1.19) in contact with the nanocomposites surface. Results of preliminary biological tests carried out with the use of mother cells extracted from human bone marrow showed that the nanocomposites may provide differenation of bone cells.

  7. Mechanical properties of carbon nanotubes and their polymer nanocomposites.

    PubMed

    Miyagawa, Hiroaki; Misra, Manjusri; Mohanty, Amar K

    2005-10-01

    More than 10 years have passed since carbon nanotubes (CNT) have been found during observations by transmission electron microscopy (TEM). Since then, one of the major applications of the CNT is the reinforcements of plastics in processing composite materials, because it was found by experiments that CNT possessed splendid mechanical properties. Various experimental methods are conducted in order to understand the mechanical properties of varieties of CNT and CNT-based composite materials. The systematized data of the past research results of CNT and their nanocomposites are extremely useful to improve processing and design criteria for new nanocomposites in further studies. Before the CNT observations, vapor grown carbon fibers (VGCF) were already utilized for composite applications, although there have been only few experimental data about the mechanical properties of VGCF. The structure of VGCF is similar to that of multi-wall carbon nanotubes (MWCNT), and the major benefit of VGCF is less commercial price. Therefore, this review article overviews the experimental results regarding the various mechanical properties of CNT, VGCF, and their polymer nanocomposites. The experimental methods and results to measure the elastic modulus and strength of CNT and VGCF are first discussed in this article. Secondly, the different surface chemical modifications for CNT and VGCF are reviewed, because the surface chemical modifications play an important role for polymer nanocomposite processing and properties. Thirdly, fracture and fatigue properties of CNT/polymer nanocomposites are reviewed, since these properties are important, especially when these new nanocomposite materials are applied for structural applications.

  8. Molecularly imprinted polymers: synthetic receptors in bioanalysis.

    PubMed

    Tse Sum Bui, Bernadette; Haupt, Karsten

    2010-11-01

    Molecularly imprinted polymers (MIPs) are tailor-made synthetic materials possessing specific cavities designed for a target molecule. Since they recognise their target analyte with affinities and selectivities comparable to those of antibody-antigen, enzyme-substrate and ligand-receptor interactions, they are often referred to as synthetic receptors or plastic antibodies. In this review, we describe the great potential and recent developments of MIPs in affinity separations, with emphasis on their application to the solid-phase extraction (SPE) of analytes from complex matrices. Research efforts made in this field to obtain water-compatible polymers for their applicability in aqueous environments are described. We particularly discuss problems encountered in the use of MIPs in SPE and the attempts carried out to improve their efficiency.

  9. Clay platelet partition within polymer blend nanocomposite films by EFTEM.

    PubMed

    Linares, Elisângela M; Rippel, Márcia M; Galembeck, Fernando

    2010-12-01

    Transmission electron microscopy (TEM) is the main technique used to investigate the spatial distribution of clay platelets in polymer nanocomposites, but it has not often been successfully used in polymer blend nanocomposites because the high contrast between polymer phases impairs the observation of clay platelets. This work shows that electron spectral imaging in energy-filtered TEM (EFTEM) in the low-energy-loss spectral crossover region allows the observation of platelets on a clear background. Separate polymer domains are discerned by imaging at different energy losses, above and below the crossover energy, revealing the material morphology. Three blends (natural rubber [NR]/poly(styrene-butyl acrylate) [P(S-BA)], P(S-BA)/poly(vinyl chloride) [PVC], and NR/starch) were studied in this work, showing low contrast between the polymer phases in the 40-60 eV range. In the NR/P(S-BA) and P(S-BA)/PVC blend nanocomposites, the clay platelets accumulate in the P(S-BA) phase, while in the P(S-BA)/PVC nanocomposites, clay is also found at the interfaces. In the NR/starch blend, clay concentrates at the interface, but it also penetrates the two polymer phases. These observations reveal that nanostructured soft materials can display complex morphochemical patterns that are discerned thanks to the ability of EFTEM to produce many contrast patterns for the same sample.

  10. Solitons in synthetic and biological polymers

    SciTech Connect

    Bishop, A.R.

    1983-01-01

    Solid state and statistical physics applications of soliton mathematics continue to expand rapidly. The present report describes connections between solid state (e.g. synthetic polymer) and biophysics, with strong nonlinearity playing the unifying role. Striking parallels examined include: analytical (as in the case of self-trapping mechanisms); numerical techniques; experimental implications, applications, and techniques. Conventional solid state probes are at last being devoted to biopolymers but their complexity is demanding new extremes and techniques.

  11. Green aqueous surface modification of polypropylene for novel polymer nanocomposites.

    PubMed

    Thakur, Vijay Kumar; Vennerberg, Danny; Kessler, Michael R

    2014-06-25

    Polypropylene is one of the most widely used commercial commodity polymers; among many other applications, it is used for electronic and structural applications. Despite its commercial importance, the hydrophobic nature of polypropylene limits its successful application in some fields, in particular for the preparation of polymer nanocomposites. Here, a facile, plasma-assisted, biomimetic, environmentally friendly method was developed to enhance the interfacial interactions in polymer nanocomposites by modifying the surface of polypropylene. Plasma treated polypropylene was surface-modified with polydopamine (PDA) in an aqueous medium without employing other chemicals. The surface modification strategy used here was based on the easy self-polymerization and strong adhesion characteristics of dopamine (DA) under ambient laboratory conditions. The changes in surface characteristics of polypropylene were investigated using FTIR, TGA, and Raman spectroscopy. Subsequently, the surface modified polypropylene was used as the matrix to prepare SiO2-reinforced polymer nanocomposites. These nanocomposites demonstrated superior properties compared to nanocomposites prepared using pristine polypropylene. This simple, environmentally friendly, green method of modifying polypropylene indicated that polydopamine-functionalized polypropylene is a promising material for various high-performance applications.

  12. Gas-phase synthesis of magnetic metal/polymer nanocomposites.

    PubMed

    Starsich, Fabian H L; Hirt, Ann M; Stark, Wendelin J; Grass, Robert N

    2014-12-19

    Highly magnetic metal Co nanoparticles were produced via reducing flame spray pyrolysis, and directly coated with an epoxy polymer in flight. The polymer content in the samples varied between 14 and 56 wt% of nominal content. A homogenous dispersion of Co nanoparticles in the resulting nanocomposites was visualized by electron microscopy. The size and crystallinity of the metallic fillers was not affected by the polymer, as shown by XRD and magnetic hysteresis measurements. The good control of the polymer content in the product nanocomposite was shown by elemental analysis. Further, the successful polymerization in the gas phase was demonstrated by electron microscopy and size measurements. The presented effective, dry and scalable one-step synthesis method for highly magnetic metal nanoparticle/polymer composites presented here may drastically decrease production costs and increase industrial yields.

  13. Gas-phase synthesis of magnetic metal/polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Starsich, Fabian H. L.; Hirt, Ann M.; Stark, Wendelin J.; Grass, Robert N.

    2014-12-01

    Highly magnetic metal Co nanoparticles were produced via reducing flame spray pyrolysis, and directly coated with an epoxy polymer in flight. The polymer content in the samples varied between 14 and 56 wt% of nominal content. A homogenous dispersion of Co nanoparticles in the resulting nanocomposites was visualized by electron microscopy. The size and crystallinity of the metallic fillers was not affected by the polymer, as shown by XRD and magnetic hysteresis measurements. The good control of the polymer content in the product nanocomposite was shown by elemental analysis. Further, the successful polymerization in the gas phase was demonstrated by electron microscopy and size measurements. The presented effective, dry and scalable one-step synthesis method for highly magnetic metal nanoparticle/polymer composites presented here may drastically decrease production costs and increase industrial yields.

  14. Stimuli-Responsive Polymer-Clay Nanocomposites under Electric Fields

    PubMed Central

    Piao, Shang Hao; Kwon, Seung Hyuk; Choi, Hyoung Jin

    2016-01-01

    This short Feature Article reviews electric stimuli-responsive polymer/clay nanocomposites with respect to their fabrication, physical characteristics and electrorheological (ER) behaviors under applied electric fields when dispersed in oil. Their structural characteristics, morphological features and thermal degradation behavior were examined by X-ray diffraction pattern, scanning electron microscopy and transmission electron microscopy, and thermogravimetric analysis, respectively. Particular focus is given to the electro-responsive ER characteristics of the polymer/clay nanocomposites in terms of the yield stress and viscoelastic properties along with their applications. PMID:28787852

  15. Nanocrystal-polymer nanocomposite electrochromic device

    SciTech Connect

    Milliron, Delia; Runnerstrom, Evan; Helms, Brett; Llordes, Anna; Buonsanti, Raffaella; Garcia, Guillermo

    2015-12-08

    Described is an electrochromic nanocomposite film comprising a solid matrix of an oxide based material, the solid matrix comprising a plurality of transparent conducting oxide (TCO) nanostructures dispersed in the solid matrix and a lithium salt dispersed in the solid matrix. Also described is a near infrared nanostructured electrochromic device having a functional layer comprising the electrochromic nanocomposite film.

  16. Evaluation of novel synthetic conditioning polymers for shampoos.

    PubMed

    Jordan, S L; Zhang, X; Amos, J; Frank, D; Menon, R; Galley, R; Davis, C; Kalantar, T; Ladika, M

    2009-01-01

    Cationic polymers have traditionally been used in shampoo formulations to impart conditioning properties to hair. In this study, commercial synthetic cationic polymers were investigated using coacervate formation, objective wet comb analysis, silicone deposition and panel studies to determine structure function properties with the goal of developing novel conditioning polymers. New polymers were synthesized and, based on criteria determined in the first part of the study, found to have marginal improvement over existing synthetic cationic conditioning polymers. A novel experimental polymer developed for a different industry was also investigated for conditioning properties. This polymer showed significant enhancement of silicone deposition over current commercial polymers, including cationic guar, even at significantly reduced silicone and polymer concentrations. The experimental polymer exhibited parity or improvement over benchmark polymers in panel studies, and similar performance to other synthetic polymers in objective wet comb studies.

  17. Glassy dynamics of nanoparticles in semiflexible ring polymer nanocomposite melts

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaolin; Jiang, Yangwei; Deng, Zhenyu; Zhang, Linxi

    2017-03-01

    By employing molecular dynamics simulations, we explore the dynamics of NPs in semiflexible ring polymer nanocomposite melts. A novel glass transition is observed for NPs in semiflexible ring polymer melts as the bending energy (Kb) of ring polymers increases. For NPs in flexible ring polymer melts (Kb = 0), NPs move in the classic diffusive behavior. However, for NPs in semiflexible ring polymer melts with large bending energy, NPs diffuse very slowly and exhibit the glassy state in which the NPs are all irreversibly caged be the neighbouring semiflexible ring polymers. This glass transition occurs well above the classical glass transition temperature at which microscopic mobility is lost, and the topological interactions of semiflexible ring polymers play an important role in this non-classical glass transition. This investigation can help us understand the nature of the glass transition in polymer systems.

  18. Glassy dynamics of nanoparticles in semiflexible ring polymer nanocomposite melts

    PubMed Central

    Zhou, Xiaolin; Jiang, Yangwei; Deng, Zhenyu; Zhang, Linxi

    2017-01-01

    By employing molecular dynamics simulations, we explore the dynamics of NPs in semiflexible ring polymer nanocomposite melts. A novel glass transition is observed for NPs in semiflexible ring polymer melts as the bending energy (Kb) of ring polymers increases. For NPs in flexible ring polymer melts (Kb = 0), NPs move in the classic diffusive behavior. However, for NPs in semiflexible ring polymer melts with large bending energy, NPs diffuse very slowly and exhibit the glassy state in which the NPs are all irreversibly caged be the neighbouring semiflexible ring polymers. This glass transition occurs well above the classical glass transition temperature at which microscopic mobility is lost, and the topological interactions of semiflexible ring polymers play an important role in this non-classical glass transition. This investigation can help us understand the nature of the glass transition in polymer systems. PMID:28290546

  19. Polymer-Layered Silicate Nanocomposites for Cryotank Applications

    NASA Technical Reports Server (NTRS)

    Miller, Sandi G.; Meador, Michael A.

    2007-01-01

    Previous composite cryotank designs have relied on the use of conventional composite materials to reduce microcracking and permeability. However, revolutionary advances in nanotechnology derived materials may enable the production of ultra-lightweight cryotanks with significantly enhanced durability and damage tolerance, as well as reduced propellant permeability. Layered silicate nanocomposites are especially attractive in cryogenic storage tanks based on results that have been reported for epoxy nanocomposite systems. These materials often exhibit an order of magnitude reduction in gas permeability when compared to the base resin. In addition, polymer-silicate nanocomposites have been shown to yield improved dimensional stability, strength, and toughness. The enhancement in material performance of these systems occurs without property trade-offs which are often observed in conventionally filled polymer composites. Research efforts at NASA Glenn Research Center have led to the development of epoxy-clay nanocomposites with 70% lower hydrogen permeability than the base epoxy resin. Filament wound carbon fiber reinforced tanks made with this nanocomposite had a five-fold lower helium leak rate than the corresponding tanks made without clay. The pronounced reduction observed with the tank may be due to flow induced alignment of the clay layers during processing. Additionally, the nanocomposites showed CTE reductions of up to 30%, as well as a 100% increase in toughness.

  20. Functional nanocomposite polymer films with uniform magnetic nanoparticle dispersions

    NASA Astrophysics Data System (ADS)

    Stojak, K.; Pal, S.; Miner, M. J.; Srikanth, H.; Skidmore, S.; Wang, J.; Weller, T.

    2009-03-01

    Magnetic nanoparticles embedded in polymer matrices are good examples of functional nanostructures with excellent potential in applications such as tunable microwave devices, EMI shielding, and flexible electronics. The challenge comes with evenly dispersing the nanoparticles once they are embedded in the polymer matrix. To avoid clustering of particles in the polymer nanocomposites and achieve excellent dispersion, competition between polymer-polymer and polymer-particle interactions must be balanced. In earlier work, we demonstrated the synthesis of 2μm thick, spin-coated nanocomposite PMMA films with Fe3O4 (mean size 15nm) nanoparticles embedded that displayed superparamagnetic behavior. In this work we will report on the successful extension of this strategy to 20 μm thick films that are needed for microwave applications. In addition to Fe3O4, we have also functionalized the films with other ferrite nanoparticles. Magnetic characterization and microstructural studies of the polymer nanocomposites will be presented and discussed. Microwave response of these films using a coplanar waveguide fixture will also be reported.

  1. Enzymes go big: surface hydrolysis and functionalization of synthetic polymers.

    PubMed

    Guebitz, Georg M; Cavaco-Paulo, Artur

    2008-01-01

    Enzyme technology has progressed from the biotransformation of small substrates to biotransformation of synthetic polymers. Important breakthroughs have been the isolation and design of novel enzymes with enhanced activity on synthetic polymer substrates. These were made possible by efficient screening procedures and genetic engineering approaches based on an in-depth understanding of the mechanisms of enzymes on synthetic polymers. Enhancement of the hydrophilicity of synthetic polymers is a key requirement for many applications, ranging from electronics to functional textile production. This review focuses on enzymes that hydrolyse polyalkyleneterephthalates, polyamides or polyacrylonitriles, specifically on the polymer surface thereby replacing harsh chemical processes currently used for hydrophilisation.

  2. Bioinspired assembly of nanoplatelets for reinforced polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Huang, Wei-Han; Dou, Xuan; Jiang, Peng

    2011-04-01

    Bio-inspired assembly of platelet particles and polyelectrolytes into ordered layered nanocomposites, which mimic the brick-and-mortar nanostructure found in the nacreous layer of mollusk shells, is of great technological importance in developing light-weight reinforced materials, separation membranes, and gas-barrier coatings. Unfortunately, the widely utilized layer-by-layer self-assembly technology is tedious in creating thick multilayered coatings. Here we report a simple filtration technology that enables the scalable production of inorganic nanoplatelets-polymer nanocomposites with layered structures. Water suspended montmorillonite (MTM) nanoclay platelets are pre-mixed with polyvinyl alcohol (PVA) aqueous solution to make stable colloidal suspensions. By using a simple vacuum filtration setup, ordered layered MTM nanoclay-PVA nanocomposites with controlled thickness can be easily prepared. The resulting selfstanding films exhibit higher tensile strength and toughness than those of natural inorganic-organic nanocomposites including nacre, bone, and dentin.

  3. Graphitic polymer nanocomposites: Wear performance and wear debris analysis

    NASA Astrophysics Data System (ADS)

    Liu, Tian

    With the addition of appropriate nanofillers, nanocomposites have been shown to be an effective avenue to achieve a multitude of enhanced properties, even extending to multi-functionalities not normally considered possible for conventional polymer materials. However, the structure and properties of polymeric nanocomposites can be influenced by some environmental factors in practical use, such as wear and temperature, due to the nature of viscoelasticity of polymer matrix. The large interfacial areas exist between matrix and nanofillers are also susceptible to the wear/temperature-related changes. In this work, I was devoted to developing high wear and/or thermal performance graphitic nanofiller reinforced high density polyethylene (HDPE) composites. Two critical issues, including appropriate filler-matrix interactions and proper dispersion of the nano-reinforcement, were addressed through the effective nanofiller surface modification. Wear, thermal and mechanical properties of the resultant nanocomposites were systematically investigated. Meanwhile, the wear debris generated on the sliding surface of composite materials was analyzed morphologically and quantitatively. In particular, the research regarding the possibility of determining the effects of wear and thermal processes on the nanocomposites by detecting dielectric signals over the lifetime of polymeric materials was conducted. Correlations that exist between effects of wear or thermal processes and dielectric properties of the nanocomposites were then explored. Based on the studies of HDPE nanocomposites, high quality ultrahigh molecular weight polyethylene (UHMWPE) nanocomposite reinforced by graphitic nanofillers was finally extended in this thesis. UHMWPE is an extremely viscous polymer and thus cannot be processed conventionally, typically resulting in dispersion issues far worse than that of other composite systems. The research presented aims at solving the issue by using ultrasonication-assisted melt

  4. Sensitive electromechanical sensors using viscoelastic graphene-polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Boland, Conor S.; Khan, Umar; Ryan, Gavin; Barwich, Sebastian; Charifou, Romina; Harvey, Andrew; Backes, Claudia; Li, Zheling; Ferreira, Mauro S.; Möbius, Matthias E.; Young, Robert J.; Coleman, Jonathan N.

    2016-12-01

    Despite its widespread use in nanocomposites, the effect of embedding graphene in highly viscoelastic polymer matrices is not well understood. We added graphene to a lightly cross-linked polysilicone, often encountered as Silly Putty, changing its electromechanical properties substantially. The resulting nanocomposites display unusual electromechanical behavior, such as postdeformation temporal relaxation of electrical resistance and nonmonotonic changes in resistivity with strain. These phenomena are associated with the mobility of the nanosheets in the low-viscosity polymer matrix. By considering both the connectivity and mobility of the nanosheets, we developed a quantitative model that completely describes the electromechanical properties. These nanocomposites are sensitive electromechanical sensors with gauge factors >500 that can measure pulse, blood pressure, and even the impact associated with the footsteps of a small spider.

  5. Sensitive electromechanical sensors using viscoelastic graphene-polymer nanocomposites.

    PubMed

    Boland, Conor S; Khan, Umar; Ryan, Gavin; Barwich, Sebastian; Charifou, Romina; Harvey, Andrew; Backes, Claudia; Li, Zheling; Ferreira, Mauro S; Möbius, Matthias E; Young, Robert J; Coleman, Jonathan N

    2016-12-09

    Despite its widespread use in nanocomposites, the effect of embedding graphene in highly viscoelastic polymer matrices is not well understood. We added graphene to a lightly cross-linked polysilicone, often encountered as Silly Putty, changing its electromechanical properties substantially. The resulting nanocomposites display unusual electromechanical behavior, such as postdeformation temporal relaxation of electrical resistance and nonmonotonic changes in resistivity with strain. These phenomena are associated with the mobility of the nanosheets in the low-viscosity polymer matrix. By considering both the connectivity and mobility of the nanosheets, we developed a quantitative model that completely describes the electromechanical properties. These nanocomposites are sensitive electromechanical sensors with gauge factors >500 that can measure pulse, blood pressure, and even the impact associated with the footsteps of a small spider. Copyright © 2016, American Association for the Advancement of Science.

  6. Processing and Characterization of Shape Memory Polymer Nanocomposites (Preprint)

    DTIC Science & Technology

    2006-02-01

    Group on Polymer Nanocomposites- PNC- Tech, http://www.imi.cnrc-nrc.gc.ca/ english /Default.htm. 2. Zhu, J ., et al ., “Reinforcing Epoxy Polymer Composites...through Covalent Integration of Functionalized Nanotubes”, Advanced Functional Materials, No. 7, 2004, pp.643-648. 3. Zeng, J ., et al , “Processing...Barrera, V., “A Study on Nanofiber-Reinforced Thermoplastic Composites (II): Investigation of the mixing Rheology and Conduction Properties

  7. Correlations between mechanical, structural, and dynamical properties of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Kutvonen, Aki; Rossi, Giulia; Ala-Nissila, Tapio

    2012-04-01

    We study the structural and dynamical mechanisms of reinforcement of a polymer nanocomposite (PNC) via coarse-grained molecular dynamics simulations. In a regime of strong polymer-filler interactions, the stress at failure of the PNC is clearly correlated to structural quantities, such as the filler loading, the surface area of the polymer-filler interface, and the network structure. Additionally, we find that small fillers, of the size of the polymer monomers, are the most effective at reinforcing the matrix by surrounding the polymer chains and maximizing the number of strong polymer-filler interactions. Such a structural configuration is correlated to a dynamical feature, namely, the minimization of the relative mobility of the fillers with respect to the polymer matrix.

  8. Carbon Nanotube/Polymer Nanocomposites Flexible Stress and Strain Sensors

    NASA Technical Reports Server (NTRS)

    Kang, Jin Ho; Sauti, Godfrey; Park, Cheol; Scholl, Jonathan A.; Lowther, Sharon E.; Harrison, Joycelyn S.

    2008-01-01

    Conformable stress and strain sensors are required for monitoring the integrity of airframe structures as well as for sensing the mechanical stimuli in prosthetic arms. For this purpose, we have developed a series of piezoresistive single-wall carbon nanotube (SWCNT)/polymer nanocomposites. The electromechanical coupling of pressure with resistance changes in these nanocomposites is exceptionally greater than that of metallic piezoresistive materials. In fact, the piezoresistive stress coefficient (pi) of a SWCNT/polymer nanocomposite is approximately two orders of magnitude higher than that of a typical metallic piezoresistive. The piezoresistive stress coefficient is a function of the nanotube concentration wherein the maximum value occurs at a concentration just above the percolation threshold concentration (phi approx. 0.05 %). This response appears to originate from a change in intrinsic resistivity under compression/tension. A systematic study of the effect of the modulus of the polymer matrix on piezoresistivity allowed us to make flexible and conformable sensors for biomedical applications. The prototype haptic sensors using these nanocomposites are demonstrated. The piezocapacitive properties of SWCNT/polymer are also characterized by monitoring the capacitance change under pressure.

  9. Large Strain Transparent Magneto-Active Polymer Nanocomposites

    NASA Technical Reports Server (NTRS)

    Yoonessi, Mitra (Inventor); Meador, Michael A (Inventor)

    2016-01-01

    A large strain polymer nanocomposite actuator is provided that upon subjected to an external stimulus, such as a magnetic field (static or electromagnetic field), an electric field, thermal energy, light, etc., will deform to thereby enable mechanical manipulations of structural components in a remote and wireless manner.

  10. Flexible high-temperature dielectric materials from polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Li, Qi; Chen, Lei; Gadinski, Matthew R.; Zhang, Shihai; Zhang, Guangzu; Li, Haoyu; Haque, Aman; Chen, Long-Qing; Jackson, Tom; Wang, Qing

    2015-07-01

    Dielectric materials, which store energy electrostatically, are ubiquitous in advanced electronics and electric power systems. Compared to their ceramic counterparts, polymer dielectrics have higher breakdown strengths and greater reliability, are scalable, lightweight and can be shaped into intricate configurations, and are therefore an ideal choice for many power electronics, power conditioning, and pulsed power applications. However, polymer dielectrics are limited to relatively low working temperatures, and thus fail to meet the rising demand for electricity under the extreme conditions present in applications such as hybrid and electric vehicles, aerospace power electronics, and underground oil and gas exploration. Here we describe crosslinked polymer nanocomposites that contain boron nitride nanosheets, the dielectric properties of which are stable over a broad temperature and frequency range. The nanocomposites have outstanding high-voltage capacitive energy storage capabilities at record temperatures (a Weibull breakdown strength of 403 megavolts per metre and a discharged energy density of 1.8 joules per cubic centimetre at 250 degrees Celsius). Their electrical conduction is several orders of magnitude lower than that of existing polymers and their high operating temperatures are attributed to greatly improved thermal conductivity, owing to the presence of the boron nitride nanosheets, which improve heat dissipation compared to pristine polymers (which are inherently susceptible to thermal runaway). Moreover, the polymer nanocomposites are lightweight, photopatternable and mechanically flexible, and have been demonstrated to preserve excellent dielectric and capacitive performance after intensive bending cycles. These findings enable broader applications of organic materials in high-temperature electronics and energy storage devices.

  11. Flexible high-temperature dielectric materials from polymer nanocomposites.

    PubMed

    Li, Qi; Chen, Lei; Gadinski, Matthew R; Zhang, Shihai; Zhang, Guangzu; Li, Haoyu; Iagodkine, Elissei; Haque, Aman; Chen, Long-Qing; Jackson, Tom; Wang, Qing

    2015-07-30

    Dielectric materials, which store energy electrostatically, are ubiquitous in advanced electronics and electric power systems. Compared to their ceramic counterparts, polymer dielectrics have higher breakdown strengths and greater reliability, are scalable, lightweight and can be shaped into intricate configurations, and are therefore an ideal choice for many power electronics, power conditioning, and pulsed power applications. However, polymer dielectrics are limited to relatively low working temperatures, and thus fail to meet the rising demand for electricity under the extreme conditions present in applications such as hybrid and electric vehicles, aerospace power electronics, and underground oil and gas exploration. Here we describe crosslinked polymer nanocomposites that contain boron nitride nanosheets, the dielectric properties of which are stable over a broad temperature and frequency range. The nanocomposites have outstanding high-voltage capacitive energy storage capabilities at record temperatures (a Weibull breakdown strength of 403 megavolts per metre and a discharged energy density of 1.8 joules per cubic centimetre at 250 degrees Celsius). Their electrical conduction is several orders of magnitude lower than that of existing polymers and their high operating temperatures are attributed to greatly improved thermal conductivity, owing to the presence of the boron nitride nanosheets, which improve heat dissipation compared to pristine polymers (which are inherently susceptible to thermal runaway). Moreover, the polymer nanocomposites are lightweight, photopatternable and mechanically flexible, and have been demonstrated to preserve excellent dielectric and capacitive performance after intensive bending cycles. These findings enable broader applications of organic materials in high-temperature electronics and energy storage devices.

  12. Interphase and particle dispersion correlations in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Senses, Erkan

    Particle dispersion in polymer matrices is a major parameter governing the mechanical performance of polymer nanocomposites. Controlling particle dispersion and understanding aging of composites under large shear and temperature variations determine the processing conditions and lifetime of composites which are very important for diverse applications in biomedicine, highly reinforced materials and more importantly for the polymer composites with adaptive mechanical responses. This thesis investigates the role of interphase layers between particles and polymer matrices in two bulk systems where particle dispersion is altered upon deformation in repulsive composites, and good-dispersion of particles is retained after multiple oscillatory shearing and aging cycles in attractive composites. We demonstrate that chain desorption and re-adsorption processes in attractive composites under shear can effectively enhance the bulk microscopic mechanical properties, and long chains of adsorbed layers lead to a denser entangled interphase layer. We further designed experiments where particles are physically adsorbed with bimodal lengths of homopolymer chains to underpin the entanglement effect in interphases. Bimodal adsorbed chains are shown to improve the interfacial strength and used to modulate the elastic properties of composites without changing the particle loading, dispersion state or polymer conformation. Finally, the role of dynamic asymmetry (different mobilities in polymer blends) and chemical heterogeneity in the interphase layer are explored in systems of poly(methyl methacrylate) adsorbed silica nanoparticles dispersed in poly(ethylene oxide) matrix. Such nanocomposites are shown to exhibit unique thermal-stiffening behavior at temperatures above glass transitions of both polymers. These interesting findings suggest that the mobility of the surface-bound polymer is essential for reinforcement in polymer nanocomposites, contrary to existing glassy layer theories

  13. Mechanical reinforcement and segmental dynamics of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Gong, Shushan

    The addition of nanofiller into a polymer matrix will dramatically change the physical properties of polymer. The introduction of nanofiller makes the polymer more applicable in many industries, such as automobile tires, coatings, semiconductors, and packaging. The altered properties are not the simple combination of the characters from the two components. The interactions in polymer nanocomposites play an important role in determining the physical properties. This dissertation focuses on the mechanical properties of polymer nanocomposites (silica/poly-2-vinylpyridine) above their glass transition temperature Tg, as a model for automobile tires, which utilize small silica particles in crosslinked rubber far above Tg. We also investigate the impacts of the interaction between particle filler and polymer matrix on the altered mechanical properties. Dielectric relaxation spectroscopy (DRS) is used to study the glassy bound polymer layers formed around the particles. The results show evidence of the existence of immobilized polymer layers at the surface of each nanoparticle. At the same time, the thickness of the immobilized polymer layers is quantified and formed to be around 2 nm. Then we consider particles with glassy bound polymer layers are bridged together (either rubbery bridge or glassy bridge) by polymer chains and form small clusters. Clusters finally percolate to form a particle-polymer network as loading fraction increases. Rheology is used to study the network formation, and to predict the boundary of rubbery bridge and glassy bridge regimes. The distance between particles determines the type of polymer bridging. The particle spacing larger than Kuhn length makes flexible (rubbery) bridge with rheology described by a flexible Rouse model for percolation. When the spacing is shorter than the Kuhn length (~ 1nm), stiffer bridge forms instead, which is called glassy bridge. The mechanical differences between rubbery bridge and glassy bridge, and the effect of

  14. Rheology and Microstructure of Polymer Nanocomposite Melts: Variation of Polymer Segment−Surface Interaction

    SciTech Connect

    Anderson, Benjamin J.; Zukoski, Charles F.

    2010-06-01

    We have studied the effects of particle packing fraction, polymer molecular weight (MW), and polymer-segment-particle-surface affinity on the phase behavior of 44 nm silica dispersions in unentangled, low MW polyethylene oxide (PEO), polyethylene oxide dimethyl ether (PEODME), and polytetrahydrofuran (PTHF) through rheological measurement and small-angle X-ray scattering. Particles are shown to be stable in PEO nanocomposites up to high volume fractions due to an adsorbed layer of polymer segments that stabilizes particles in the melt. Comparison of the PEO nanocomposite to PEODME and PTHF nanocomposites reveals little evidence of an adsorbed layer in the spirit of the PEO nanocomposite. Measurement of the PTHF nanocomposite viscosity reveals evidence of segment slip at the particle surface by the particle intrinsic viscosity being less than Einstein's value. At higher particle volume fractions, the viscosity diverges, yielding an elastic response. The elastic response of the PEO nanocomposite has the signatures of a colloidal glass, while the PEODME and PTHF nanocomposites resemble a gel. Measurement of the particle structure factor reveals a change from overall repulsive particles in PEO to attractive particles in PTHF as the segment-surface interaction is changed.

  15. Processing, Characterization, and Modeling of Polymer/Clay Nanocomposite Foams

    NASA Astrophysics Data System (ADS)

    Jo, Choonghee; Naguib, Hani E.

    2007-04-01

    The effects of the material parameters and processing conditions on the foam morphologies, and mechanical properties of polymer/clay nanocomposite foams were studied. Microcellular closed-cell nanocomposite foams were manufactured with poly(methylmethacrylate) (PMMA) and high density polyethylene (HDPE), where the nanoclay loadings of 0.5, 1.0, and 2.0 wt% were used. The effect of clay contents and foaming conditions on the volume expansion ratio, cell size, elastic modulus, tensile strength, and elongation at break were investigated and compared between amorphous and semicrystalline polymers. An elastic modulus model for tensile behavior of foams was proposed by using the micromechanics theory. The model was expressed in terms of microstructural properties of polymer and physical properties of the foams. The tensile experimental data of the foams were compared with those predicted by the theoretical model.

  16. Solvent transport through hard-soft segmented polymer nanocomposites.

    PubMed

    Rath, Sangram K; Edatholath, Saji S; Patro, T Umasankar; Sudarshan, Kathi; Sastry, P U; Pujari, Pradeep K; Harikrishnan, G

    2016-01-28

    We conducted transport studies of a common solvent (toluene) in its condensed state, through a model hard-soft segmented polyurethane-clay nanocomposite. The solvent diffusivity is observed to be non-monotonic in a functional relationship with a filler volume fraction. In stark contrast, both classical tortuous path theory based geometric calculations and free volume measurements suggest the normally expected monotonic decrease in diffusivity with increase in clay volume fraction. Large deviations between experimentally observed diffusivity coefficients and those theoretically estimated from geometric theory are also observed. However, the equilibrium swelling of a nanocomposite as indicated by the solubility coefficient did not change. To gain an insight into the solvent interaction behavior, we conducted a pre- and post swollen segmented phase analysis of pure polymers and nanocomposites. We find that in a nanocomposite, the solvent has to interact with a filler altered hard-soft segmented morphology. In the altered phase separated morphology, the spatial distribution of thermodynamically segmented hard blocks in the continuous soft matrix becomes a strong function of filler concentration. Upon solvent interaction, this spatial distribution gets reoriented due to sorption and de-clustering. The results indicate strong non-barrier influences of nanoscale fillers dispersed in phase segmented block co-polymers, affecting solvent diffusivity through them. Based on pre- and post swollen morphological observations, we postulate a possible mechanism for the non-monotonic behaviour of solvent transport for hard-soft segmented co-polymers, in which the thermodynamic phase separation is influenced by the filler.

  17. Acid activation of bentonites and polymer-clay nanocomposites.

    SciTech Connect

    Carrado, K. A.; Komadel, P.; Center for Nanoscale Materials; Slovak Academy of Sciences

    2009-04-01

    Modified bentonites are of widespread technological importance. Common modifications include acid activation and organic treatment. Acid activation has been used for decades to prepare bleaching earths for adsorbing impurities from edible and industrial oils. Organic treatment has sparked an explosive interest in a class of materials called polymer-clay nanocomposites (PCNs). The most commonly used clay mineral in PCNs is montmorillonite, which is the main constituent of bentonite. PCN materials are used for structural reinforcement and mechanical strength, for gas permeability barriers, as flame retardants, and to minimize surface erosion (ablation). Other specialty applications include use as conducting nanocomposites and bionanocomposites.

  18. Phosphazene Silicate Nanocomposites. A Survey of Materials Properties and Synthetic Methods Using New Catalysts

    SciTech Connect

    Harrup, Mason Kurt; Wertsching, Alan Kevin; Stewart, Frederick Forrest

    2000-03-01

    In the ceramics community, manipulation of synthetic conditions such as the choice of acid, base or ionic species as catalysts, aging of precursor solutions, and choice of sintering temperatures in the formation of silicate networks are known to produce radically different glass and ceramic morphologies.1 Implementation of these approaches has been attempted for some organic polymer based hybrid nanocomposites2 but not for polyphosphazene silicate composites. The desire to create unique and novel network morphologies became the impetus for establishing new catalysis protocols. The surprising inability to reproduce the mechanical properties of a well-established benchmark composite material from the literature,3 was one principal driver that initiated this in-depth investigation into the roles that the nature and amount of catalysts play in the production and physical properties of these composites.

  19. Polymer nanocomposites based on polyamide 12 filled with nickel and copper nanoparticles

    NASA Astrophysics Data System (ADS)

    Shapoval, E. S.; Zuev, V. V.

    2014-05-01

    The method for producing nanoscale nickel particles (particle diameter 20-30 nm) protected from oxidation thin carbon shell (1-2 nm) was developed. The polymer nanocomposites based on PA 12 matrix filled with filled with 0.1 to 1 wt. % nickel nanoparticles were synthesized by in situ polymerization. The tensile properties of polymer composites (Young's modulus, ultimate strength) were increased on 15-20% compared to the neat polymer. Also this article reports the findings of an investigation of a synthetic route for a synthesis a size-controllable molecularly capped copper nanoparticles. At using copper nanoparticles as filler the mechanical properties became worse by about 5-10% as compared PA12. Thus, needs the search of optimal way to modification of PA 12 matrix with copper nanoparticles.

  20. Controlling cell-material interactions with polymer nanocomposites by use of surface modifying additives

    NASA Astrophysics Data System (ADS)

    Poole-Warren, L. A.; Farrugia, B.; Fong, N.; Hume, E.; Simmons, A.

    2008-11-01

    Polymer nanocomposites (NC) are fabricated by incorporating well dispersed nanoscale particles within a polymer matrix. This study focuses on elastomeric polyurethane (PU) based nanocomposites, containing organically modified silicates (OMS), as bioactive materials. Nanocomposites incorporating chlorhexidine diacetate as an organic modifier (OM) were demonstrated to be antibacterial with a dose dependence related to both the silicate loading and the loading of OM. When the non-antibacterial OM dodecylamine was used, both cell and platelet adhesion were decreased on the nanocomposite surface. These results suggest that OM is released from the polymer and can impact on cell behaviour at the interface. Nanocomposites have potential use as bioactive materials in a range of biomedical applications.

  1. Viscoelastic properties of polymer based layered-silicate nanocomposites

    NASA Astrophysics Data System (ADS)

    Ren, Jiaxiang

    Polymer based layered-silicate nanocomposites offer the potential for dramatically improved mechanical, thermal, and barrier properties while keeping the material density low. Understanding the linear and non-linear viscoelastic response for such materials is crucial because of the ability of such measurements to elucidate the mesoscale dispersion of layered-silicates and changes in such dispersion to applied flows as would be encountered in processing of these materials. A series of intercalated polystyrene (and derivatives of polystyrene) layered-silicate nanocomposites are studied to demonstrate the influence of mesoscale dispersion and organic---inorganic interactions on the linear and non-linear viscoelastic properties. A layered-silicate network structure is exhibited for the nanocomposites with strong polymer-silicate interaction such as montmorillonite (2C18M) and fluorohectorite (C18F) and the percolation threshold is ˜ 6 wt % for the 2C18M based hybrids. However, the nanocomposites based on hectorite (2C18H) with weak polymer-silicate interaction exhibit liquid-like terminal zone behavior. Furthermore, the enhanced terminal zone elastic modulus and viscosity of high brominated polystyrene and high molecular weight polystyrene based 2C18M nanocomposites suggest an improved delamination and dispersion of layered-silicates in the polymer matrix. The non-linear viscoelastic properties, specifically, the non-linear stress relaxation behavior and the applicability of time---strain separability, the effect of increasing strain amplitude on the oscillatory shear flow properties, and the shear rate dependence of the steady shear flow properties are examined. The silicate sheets (or collections of sheets) exhibit the ability to be oriented by the applied flow. Experimentally, the empirical Cox - Merz rule is demonstrated to be inapplicable for the hybrids. Furthermore, the K-BKZ constitutive model is used to model the steady shear properties. While being able to

  2. Chitosan-gold-Lithium nanocomposites as solid polymer electrolyte.

    PubMed

    Begum, S N Suraiya; Pandian, Ramanathaswamy; Aswal, Vinod K; Ramasamy, Radha Perumal

    2014-08-01

    Lithium micro batteries are emerging field of research. For environmental safety biodegradable films are preferred. Recently biodegradable polymers have gained wide application in the field of solid polymer electrolytes. To make biodegradable polymers films plasticizers are usually used. However, use of plasticizers has disadvantages such as inhomogenities in phases and mechanical instability that will affect the performance of Lithium micro batteries. We have in this research used gold nanoparticles that are environmentally friendly, instead of plasticizers. Gold nanoparticles were directly template upon chitosan membranes by reduction process so as to enhance the interactions of Lithium with the polymer. In this article, for the first time the characteristics of Chitosan-gold-Lithium nanocomposite films are investigated. The films were prepared using simple solution casting technique. We have used various characterization tools such as Small Angle Neutron Scattering (SANS), XRD, FTIR, Raman, FESEM, and AFM, Light scattering, Dielectric and electrical conductivity measurements. Our investigations show that incorporation of gold results in enhancement of conductivity in Lithium containing Chitosan films. Also it affects the dielectric characteristics of the films. We conclude through various characterization tools that the enhancement in the conductivity was due to the retardation of crystal growth of lithium salt in the presence of gold nanoparticles. A model is proposed regarding the formation of the new nanocomposite. The conductivity of these biodegradable films is comparable to those of the current inorganic Lithium micro batteries. This new chitosan-Au-Li nanocomposite has potential applications in the field of Lithium micro batteries.

  3. Biofunctionalized ferromagnetic CoPt3/polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Martins, M. A.; Neves, M. C.; Esteves, A. C. C.; Girginova, P. I.; Guiomar, A. J.; Amaral, V. S.; Trindade, T.

    2007-05-01

    Magnetic latexes were prepared by the encapsulation of organically capped CoPt3 nanoparticles via miniemulsion in situ radical polymerization of tert-butyl acrylate (tBA). This is the first example of a CoPt3 based polymer nanocomposite showing ferromagnetic behaviour at room temperature. Each nanocomposite particle contains a magnetic core composed of CoPt3 nanoparticles (d~7 nm, a0 = 3.848 Å) encapsulated by poly(t-butyl acrylate). The CoPt3/PtBA latexes contain polyester groups that can be readily hydrolysed, rendering the surface with carboxylic functionalities and hence allowing bioconjugation. Complementary to such surface modification experiments, we report that bovine IgG antibodies can bind to the magnetic latexes, and the potential of the nanocomposites for in vitro specific bioapplications is discussed.

  4. One-pot biosynthesis of polymer-inorganic nanocomposites

    NASA Astrophysics Data System (ADS)

    Geng, Jiaqing; Yang, Dong; Zhu, Yong; Cao, Lichao; Jiang, Zhongyi; Sun, Yan

    2011-06-01

    A biological method is demonstrated to fabricate the polymer-inorganic nanocomposites (PINCs) utilizing bacterium as an efficient and versatile biofactory. Gluconacetobacter xylinum that can produce bacterial cellulose is incubated in the culture medium containing titanium or silica precursor. The PINCs can be acquired under the elaborate control of the culturing condition of G. xylinum, in which the formation of inorganic nanoparticles about several tens of nanometers in size synchronizes the fabrication of reticulated bacterial cellulose membrane composed of dense and finely branched nanofibers about 60-120 nm in diameter. The composition and chemical states, morphology, thermal stability of the inorganic nanoparticles, and nanocomposites were extensively characterized. A tentative mechanism for the formation of PINCs is proposed. It is hoped that this study may establish a generic platform toward facile and green synthesis of nanocomposite materials.

  5. Predicting The Photoageing And Photostabilization Of Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Therias, S.; Lonkar, S.; Leroux, F.; Gardette, J. L.; Dintcheva, N. T.; La Mantia, F. P.

    2010-06-01

    The influence of organo-clays on the durability of the nanocomposite materials finds expression in the efficiency of stabilizers. With the two kinds of stabilizers tested that are conventionally a processing one with a phenolic function and a long term stabilizer which is a redox antioxidant (hindered amine light stabilizer), the main conclusion is that the presence of organo-montmorillonite decreases the efficiency of the stabilizer. However, with specific stabilization additives the prodegradant effect of nanoclays can be cancelled and it offers a new insight in the stabilization strategy of nanocomposites. The photochemical study of PP/LDH nanocomposites revealed that the divalent cations of LDH nanofiller (Mg or Zn) have an influence on the durability of the polymer and also on the photostabilization with an opposite behavibour between phenolic and redox antioxidants.

  6. Structure-property relationships in graphene/polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Iqbal, Muhammad Z.

    Graphene's unique combination of excellent electrical, thermal, and mechanical properties can provide multi-functional reinforcement for polymer nanocomposites. However, poor dispersion of graphene in non-polar polyolefins limits its applications as a universal filler. Thus, the overall goal of this thesis was to improve graphene's dispersion in graphene/polyolefin nanocomposites and develop processing-structure-property relationships. A new polymer matrix was synthesized by blending polyethylene (PE) with oxidized polyethylene (OPE). Inclusion of OPE in PE produced miscible blends, but the miscibility decreased with increasing OPE loading. Meanwhile, the Young's modulus of blends increased with increasing OPE concentration, attributed to decreased long period order in PE and increased crystallinity. In addition, the miscibility of OPE in PE substantially reduced the viscosity of blends. Using thermally reduced graphene (TRG) produced by simultaneous thermal exfoliation and reduction of graphite oxide, electrically conductive nanocomposites were manufactured by incorporating TRG in PE/OPE blends via solution blending. The rheological and electrical percolations decreased substantially to 0.3 and 0.13 vol% of TRG in PE/OPE/TRG nanocomposites compared to 1.0 and 0.3 vol% in PE/TRG nanocomposites. Improved dispersion of TRG in blends was attributed to increased TRG/polymer interactions, leading to high aspect ratio of the dispersed TRG. A universal Brownian dispersion mechanism for graphene was concluded similar to that of carbon nanotubes, following the Doi-Edwards theory. Furthermore, the improved dispersion of TRG correlated with the formation of surface fractals in PE/OPE/TRG nanocomposites, whereas the poor dispersion of TRG in PE led to the formation of only mass fractals. Moreover, graphene and carbon black (CB) were combined as a synergic filler for manufacturing electrically conductive PE nanocomposites. Smaller fractals were observed at lower CB

  7. Atomistic simulation of graphene-based polymer nanocomposites

    SciTech Connect

    Rissanou, Anastassia N.; Bačová, Petra; Harmandaris, Vagelis

    2016-05-18

    Polymer/graphene nanostructured systems are hybrid materials which have attracted great attention the last years both for scientific and technological reasons. In the present work atomistic Molecular Dynamics simulations are performed for the study of graphene-based polymer nanocomposites composed of pristine, hydrogenated and carboxylated graphene sheets dispersed in polar (PEO) and nonpolar (PE) short polymer matrices (i.e., matrices containing chains of low molecular weight). Our focus is twofold; the one is the study of the structural and dynamical properties of short polymer chains and the way that they are affected by functionalized graphene sheets while the other is the effect of the polymer matrices on the behavior of graphene sheets.

  8. Interfaces in polymer nanocomposites – An NMR study

    SciTech Connect

    Böhme, Ute; Scheler, Ulrich

    2016-03-09

    Nuclear Magnetic Resonance (NMR) is applied for the investigation of polymer nanocomposites. Solid-state NMR is applied to study the modification steps to compatibilize layered double hydroxides with non-polar polymers. {sup 1}H relaxation NMR gives insight on the polymer dynamics over a wide range of correlation times. For the polymer chain dynamics the transverse relaxation time T{sub 2} is most suited. In this presentation we report on two applications of T{sub 2} measurements under external mechanical stress. In a low-field system relaxation NMR studies are performed in-situ under uniaxial stress. High-temperature experiments in a Couette cell permit the investigation of the polymer dynamics in the melt under shear flow.

  9. How to define a nanocomposite by the example of polymer/organoclay nanostructured composites

    NASA Astrophysics Data System (ADS)

    Mikitaev, A. K.; Kozlov, G. V.

    2017-07-01

    Introducing the filler nanoparticles into a polymer matrix is shown to not necessarily favor the formation of a true nanomaterial (nanocomposite). For this, a certain nanofiller structure has to be achieved in the polymer matrix. In polymer/organoclay nanocomposites it can be attained only by forming an exfoliated organoclay structure. A transition from micro-to nanocomposite under other similar conditions is accompanied by a drastic increase (by several times) in the elastic modulus.

  10. In vivo biocompatibility of ultra-short single-walled carbon nanotube/biodegradable polymer nanocomposites for bone tissue engineering.

    PubMed

    Sitharaman, Balaji; Shi, Xinfeng; Walboomers, X Frank; Liao, Hongbing; Cuijpers, Vincent; Wilson, Lon J; Mikos, Antonios G; Jansen, John A

    2008-08-01

    Scaffolds play a pivotal role in the tissue engineering paradigm by providing temporary structural support, guiding cells to grow, assisting the transport of essential nutrients and waste products, and facilitating the formation of functional tissues and organs. Single-walled carbon nanotubes (SWNTs), especially ultra-short SWNTs (US-tubes), have proven useful for reinforcing synthetic polymeric scaffold materials. In this article, we report on the in vivo biocompatibility of US-tube reinforced porous biodegradable scaffolds in a rabbit model. US-tube nanocomposite scaffolds and control polymer scaffolds were implanted in rabbit femoral condyles and in subcutaneous pockets. The hard and soft tissue response was analyzed with micro-computed tomography (micro CT), histology, and histomorphometry at 4 and 12 weeks after implantation. The porous US-tube nanocomposite scaffolds exhibited favorable hard and soft tissue responses at both time points. At 12 weeks, a three-fold greater bone tissue ingrowth was seen in defects containing US-tube nanocomposite scaffolds compared to control polymer scaffolds. Additionally, the 12 week samples showed reduced inflammatory cell density and increased connective tissue organization. No significant quantitative difference in polymer degradation was observed among the various groups; qualitative differences between the two time points were consistent with expected degradation due to the progression of time. Although no conclusions can be drawn from the present study concerning the osteoinductivity of US-tube nanocomposite scaffolds, the results suggest that the presence of US-tubes may render nanocomposite scaffolds bioactive assisting osteogenesis.

  11. Synthesis of surface functionalized magnetic nanoparticles and their polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Miner, M. J.; Morales, M. B.; Poddar, P.; Srikanth, H.; Skidmore, S. M.; Weller, T. M.

    2008-03-01

    Magnetic nanoparticles embedded in polymer matrices are good examples of functional nanostructures with excellent potential in applications such as tunable microwave devices, EMI shielding, flexible electronics etc. Control over the dispersion of the nanoparticle phase embedded in a polymer matrix is critical and often challenging. To achieve excellent dispersion, competition between polymer-polymer and polymer-particle interactions must be balanced to avoid clustering of particles in polymer nanocomposites. In earlier work, we had demonstrated the successful synthesis of 2μm thick spin coated nanocomposite PMMA films with Fe3O4 (mean size 15nm) nanoparticle inclusions exhibiting superparamagnetic behavior. In this work, we will present our attempts to achieve thicker films more suitable for microwave applications and a study of the role of surface functionalization of ferrite nanoparticles synthesized using co-precipitation and hydrothermal routes. Cross-sectional SEM and TEM studies as well as magnetic characterization using a Physical Property Measurement System will be presented and discussed. We will also report on the microwave response of these films using a coplanar waveguide fixture. Work at USF supported by NSF through a GOALI grant from NSF-DMII.

  12. Polymer nanocomposites for high-temperature composite repair

    SciTech Connect

    Sheng, Xia

    2008-01-01

    A novel repair agent for resin-injection repair of advanced high temperature composites was developed and characterized. The repair agent was based on bisphenol E cyanate ester (BECy) and reinforced with alumina nanoparticles. To ensure good dispersion and compatibility with the BECy matrix in nanocomposites, the alumina nanoparticles were functionalized with silanes. The BECy nanocomposites, containing bare and functionalized alumina nanoparticles, were prepared and evaluated for their thermal, mechanical, rheological, and viscoelastic properties. The monomer of BECy has an extremely low viscosity at ambient temperature, which is good for processability. The cured BECy polymer is a highly cross-linked network with excellent thermal mechanical properties, with a high glass transition temperature (Tg) of 270 C and decomposition temperature above 350 C. The incorporation of alumina nanoparticles enhances the mechanical and rheological properties of the BECy nanocomposites. Additionally, the alumina nanoparticles are shown to catalyze the cure of BECy. Characterization of the nanocomposites included dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, rheological and rheokinetic evaluation, and transmission electron microscopy. The experimental results show that the BECy nanocomposite is a good candidate as repair agent for resin-injection repair applications.

  13. Influence of Surface Coating of Magnetic Nanoparticles on Mechanical Properties of Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Yarar, Ecem; Karakas, Gizem; Rende, Deniz; Ozisik, Rahmi; Malta, Seyda

    Polymer nanocomposites have emerged as promising materials due to improved properties when compared with conventional bulk polymers. Nanofillers are natural or synthetic organic/inorganic particles that are less than 100 nm in at least one dimension. Even the addition of trace amounts of nanofillers to polymers may lad to unique combinations of properties. Among variety of inorganic nanofillers, iron oxide magnetic nanoparticles are of great interest due to their unique physical and chemical properties, such as low toxicity, biocompatibility, large magnetization and conductivity, owing to their extremely small size and large specific surface area. In this study, approximately 8-10 nm magnetic nanoparticles coated with either citric acid or oleic acid are synthesized and blended with poly(methyl methacrylate) (PMMA) or poly(ethylene oxide) (PEO). The hydrophobicity/hydrophillicity of the polymer and the surface coating on the iron oxide nanoparticles are exploited to control the dispersion state of nanoparticles, and the effect of dispersion on mechanical and thermal properties of the nanocomposite are investigated via experimental methods such as dynamic mechanical analysis and differential scanning calorimetry. This material is based upon work partially supported by the National Science Foundation under Grant No. CMMI-1538730 and TUBITAK 112M666.

  14. Development of Filler Structure in Colloidal Silica-Polymer Nanocomposites

    SciTech Connect

    Meth, Jeffrey S; Zane, Stephen G; Chi, Changzai; Londono, J David; Wood, Barbara A; Cotts, Patricia; Keating, Mimi; Guise, William; Weigand, Steven

    2012-02-07

    The realization of the full potential for polymeric nanocomposites to manifest their entitled property improvements relies, for some properties, on the ability to achieve maximum particle-matrix interfacial area. Well-dispersed nanocomposites incorporating colloidal silica as the filler can be realized in both polystyrene and poly(methyl methacrylate) matrices by exploiting the charge stabilized nature of silica in nonaqueous solvents which act as Bronsted bases. We demonstrate that dispersions of colloidal silica in dimethylformamide are charge stabilized, regardless of organosilyl surface functionalization. When formulated with polymer solutions, the charge stabilized structure is maintained during drying until the charged double layer collapses. Although particles are free to diffuse and cluster after this neutralization, increased matrix viscosity retards the kinetics. We demonstrate how high molecular weight polymers assist in immobilizing the structure of the silica to produce well-dispersed composites. The glass transition temperatures of these composites do not vary, even at loadings up to 50 vol %.

  15. Relative toxicity of pyrolysis products of some synthetic polymers

    NASA Technical Reports Server (NTRS)

    Hilado, C. J.; Slattengren, C. L.; Furst, A.; Kourtides, D. A.; Parker, J. A.

    1976-01-01

    Nineteen samples of synthetic polymers were evaluated for relative toxicity in the course of characterizing materials intended for aircraft interior applications. The generic polymers included ABS, chlorinated PVC, polycarbonate, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyaryl sulfone, polyether sulfone, polybismaleimide, and polyvinyl fluoride. Test results are presented, and compared in relative rankings with similar results on cellulosic materials and other synthetic polymers. Under these test conditions, the samples of synthetic polymers were either comparable to or significantly less toxic than the samples of commercial cellulosic materials.

  16. Relative toxicity of pyrolysis products of some synthetic polymers

    NASA Technical Reports Server (NTRS)

    Hilado, C. J.; Slattengren, C. L.; Furst, A.; Kourtides, D. A.; Parker, J. A.

    1976-01-01

    Nineteen samples of synthetic polymers were evaluated for relative toxicity in the course of characterizing materials intended for aircraft interior applications. The generic polymers included ABS, chlorinated PVC, polycarbonate, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyaryl sulfone, polyether sulfone, polybismaleimide, and polyvinyl fluoride. Test results are presented, and compared in relative rankings with similar results on cellulosic materials and other synthetic polymers. Under these test conditions, the samples of synthetic polymers were either comparable to or significantly less toxic than the samples of commercial cellulosic materials.

  17. High frequency electromagnetic interference shielding magnetic polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    He, Qingliang

    Electromagnetic interference is one of the most concerned pollution and problem right now since more and more electronic devices have been extensively utilized in our daily lives. Besides the interference, long time exposure to electromagnetic radiation may also result in severe damage to human body. In order to mitigate the undesirable part of the electromagnetic wave energy and maintain the long term sustainable development of our modern civilized society, new technology development based researches have been made to solve this problem. However, one of the major challenges facing to the electromagnetic interference shielding is the relatively low shielding efficiency and the high cost as well as the complicated shielding material manufacture. From the materials science point of view, the key solutions to these challenges are strongly depended on the breakthrough of the current limit of shielding material design and manufacture (such as hierarchical material design with controllable and predictable arrangement in nanoscale particle configuration via an easy in-situ manner). From the chemical engineering point of view, the upgrading of advanced material shielding performance and the enlarged production scale for shielding materials (for example, configure the effective components in the shielding material in order to lower their usage, eliminate the "rate-limiting" step to enlarge the production scale) are of great importance. In this dissertation, the design and preparation of morphology controlled magnetic nanoparticles and their reinforced polypropylene polymer nanocomposites will be covered first. Then, the functionalities of these polymer nanocomposites will be demonstrated. Based on the innovative materials design and synergistic effect on the performance advancement, the magnetic polypropylene polymer nanocomposites with desired multifunctionalities are designed and produced targeting to the electromagnetic interference shielding application. In addition

  18. Nanocomposite Interphases for Improved Transparent Polymer Composite Materials

    DTIC Science & Technology

    2008-08-01

    Nanocomposite Interphases for Improved Transparent Polymer Composite Materials by Daniel J. O’Brien, Jason Robinette, James R. Heflin , and...Jason Robinette Weapons and Materials Research Directorate, ARL James R. Heflin and Jason Ridley Virginia Polytechnic Institue and State... Heflin ,* and Jason Ridley* 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) U.S. Army Research Laboratory ATTN: AMSRD-ARL

  19. Actuators based on intrinsic conductive polymers/carbon nanoparticles nanocomposites

    NASA Astrophysics Data System (ADS)

    Bocchini, Sergio; Accardo, Daisy; Ariano, Paolo; Lombardi, Mariangela; Biso, Maurizio; Ansaldo, Alberto; Ricci, Davide

    2013-04-01

    New polyaniline (PANi) synthesis was performed starting from non-toxic N-phenil-p-phenylenediamine (aniline dimer) using reverse addition of monomer to oxidizing agent, the synthesis allows to produce highly soluble PANi. Several types of doped PANi were prepared to be used on electromechanical active actuators. Different techniques were used to include carbon nanoparticles such as carbon nanotubes and graphene. Bimorph solid state ionic actuators were prepared with these novel nanocomposites using a variety of supporting polymers.

  20. Characterization of polymer based nanocomposites with carbon nanotubes.

    PubMed

    Ciecierska, Ewelina; Boczkowska, Anna; Kurzydłowski, Krzysztof J

    2014-04-01

    The paper concerns investigation of the processing methods influence on the electrical, thermal and mechanical properties of the polymer matrix nanocomposites with carbon nanotubes (CNTs) as a filler. The focus is put on the relation between microstructure and properties dependently on the parameters of mixing, epoxy matrix curing parameters, neat epoxy resin viscosity, carbon nanotubes modified with different functional groups, as well as carbon nanotubes weight fraction. Nanocomposites with the CNTs varied from 0.05 to 5 wt.% were obtained by dispersion methods such as: mechanical stirring, ultrasonication and combination both of them, as well as calendaring. Three epoxy resin systems were tested, varied in viscosity and curing temperature. Also CNTs nonmodified and modified with amino, carboxyl and hydroxyl groups were used. The choice of the best epoxy resin system and kind of CNTs for fabrication of conductive nanocomposites was done. The lower neat epoxy resin viscosity the better dispersion of CNTs can be achieved. The distribution of CNTs in the epoxy matrix was evaluated using high resolution scanning electron microscopy, supported by image analysis. Electrical conductivity, as well as thermal stability and thermodynamic properties of polymers filled with CNTs were determined. Activation energy of decomposition process was calculated from thermogravimetric curves by Flynn-Wall-Ozawa method. The deterioration of thermal stability was obtained, while mechanical properties increase with the CNTs weight fraction growth up to 0.1%. Calendaring was found as the best method of CNTs dispersion in the polymer matrix.

  1. Linear and nonlinear optical processing of polymer matrix nanocomposites

    NASA Astrophysics Data System (ADS)

    DeJournett, Travis J.; Han, Karen; Olasov, Lauren R.; Zeng, Fan W.; Lee, Brennan; Spicer, James B.

    2015-08-01

    This work focuses on the scalable synthesis and processing of nanostructures in polymer matrix nanocomposites (PMNCs) for applications that require photochemical functionality of these nanostructures. An in situ vapor deposition process using various metal and metal oxide precursors has been used to create a range of nanocomposites that display photochromic and photocatalytic behaviors. Under specific processing conditions, these composites consist of discrete nanoparticles distributed uniformly throughout the bulk of an optically transparent polymer matrix. Incorporating other chemical species as supplementary deposition agents in the synthesis process can modify these particles and produce complicated nanostructures with enhanced properties. In particular, work has been carried out to structure nanoparticles using laser irradiation. Starting with metallic or metal oxide nanoparticles in the polymer matrix, localized chemical vapor deposition in the near-particle environment has been carried out using laser irradiation to decompose chemical precursors leading to the formation of secondary structures surrounding the seed nanoparticles. Control of the spatial and temporal characteristics of the excitation source allows for synthesis of nanocomposites with a high degree of control over the location, composition and size of nanoparticles in the matrix and presents the opportunity to produce patterned materials with spatially varying properties.

  2. Dynamic Mechanical Characterization of Thin Film Polymer Nanocomposites

    NASA Technical Reports Server (NTRS)

    Herring, Helen M.; Gates, Thomas S. (Technical Monitor)

    2003-01-01

    Many new materials are being produced for aerospace applications with the objective of maximizing certain ideal properties without sacrificing others. Polymer composites in various forms and configurations are being developed in an effort to provide lighter weight construction and better thermal and electrical properties and still maintain adequate strength and stability. To this end, thin film polymer nanocomposites, synthesized for the purpose of influencing electrical conductivity using metal oxide particles as filler without incurring losses in mechanical properties, were examined to determine elastic modulus and degree of dispersion of particles. The effects of various metal oxides on these properties will be discussed.

  3. Functionalized synthetic biodegradable polymer scaffolds for tissue engineering.

    PubMed

    Liu, Xiaohua; Holzwarth, Jeremy M; Ma, Peter X

    2012-07-01

    Scaffolds (artificial ECMs) play a pivotal role in the process of regenerating tissues in 3D. Biodegradable synthetic polymers are the most widely used scaffolding materials. However, synthetic polymers usually lack the biological cues found in the natural extracellular matrix. Significant efforts have been made to synthesize biodegradable polymers with functional groups that are used to couple bioactive agents. Presenting bioactive agents on scaffolding surfaces is the most efficient way to elicit desired cell/material interactions. This paper reviews recent advancements in the development of functionalized biodegradable polymer scaffolds for tissue engineering, emphasizing the syntheses of functional biodegradable polymers, and surface modification of polymeric scaffolds.

  4. Three-body interactions in polymer nanocomposites.

    SciTech Connect

    Yethiraj, Arun; Frischknecht, Amalie Lucile

    2010-04-01

    We use the modified iSAFT density functional theory (DFT) to calculate interactions among nanoparticles immersed in a polymer melt. Because a polymer can simultaneously interact with more than two nanoparticles, three-body interactions are important in this system. We treat the nanoparticles as spherical surfaces, and solve for the polymer densities around the nanoparticles in three dimensions. The polymer is modeled as a freely-jointed chain of spherical sites, and all interactions are repulsive. The potential of mean force (PMF) between two nanoparticles displays a minimum at contact due to the depletion effect. The PMF calculated from the DFT agrees nearly quantitatively with that calculated from self-consistent PRISM theory. From the DFT we find that the three-body free energy is significantly different in magnitude than the effective three-body free energy derived from the two-particle PMF.

  5. Understanding mechanical properties of polymer nanocomposites with molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Sen, Suchira

    Equilibrium Molecular Dynamics (MD) simulations are used extensively to study various aspects of polymer nanocomposite (PNC) behavior in the melt state---the key focus is on understanding mechanisms of mechanical reinforcement. Mechanical reinforcement of the nanocomposite is believed to be caused by the formation of a network-like structure---a result of polymer chains bridging particles to introduce network elasticity. In contrast, in traditional composites, where the particle size range is hundreds of microns and high loadings of particle are used, the dominant mechanism is the formation of a percolated filler structure. The difference in mechanism with varying particle sizes, at similar particle loading, arises from the polymer-particle interfacial area available, which increases dramatically as the particle size decreases. Our interest in this work is to find (a) the kind of polymer-particle interactions necessary to facilitate the formation of a polymer network in a nanocomposite, and (b) the reinforcing characteristics of such a polymer network. We find that very strong polymer-particle binding is necessary to create a reinforcing network. The strength of the binding has to be enough to immobilize polymer on the particle surface for timescales comparable and larger than the terminal relaxation time of the stress of the neat melt. The second finding, which is a direct outcome of very strong binding, is that the method of preparation plays a critical role in determining the reinforcement of the final product. The starting conformations of the polymer chains determine the quality of the network. The strong binding traps the polymer on the particle surface which gets rearranged to a limited extent, within stress relaxation times. Significant aging effects are seen in system relaxation; the inherent non-equilibrium consequences of such strong binding. The effect of the polymer immobilization slows down other relaxation processes. The diffusivity of all chains is

  6. Porous networks derived from synthetic polymer-clay complexes

    SciTech Connect

    Carrado, K.A.; Thiyagarajan, P.; Elder, D.L.

    1995-05-12

    Synthetic hectorites were hydrothermally crystallized with direct incorporation of a cationic polymer poly(dimethyl diallyl ammonium chloride) (PDDA), and two neutral cellulosic polymers hydroxypropyl methylcellulose (HPMC) and hydroxyethyl cellulose (HEC). Synthetic PDDA-hectorite displays the lowest d-spacing at 15.8 {Angstrom} along with less polymer incorporation (7.8 wt % organic) than the neutral polymers (18--22 wt % organic). Thermal analysis and small angle neutron scattering were used to further examine the polymer-clay systems. Clay platelets of the largest size and best stacking order occur when cationic PDDA polymer is used. PDDA also enhances these properties over the crystallites prepared for a control mineral, where no polymer is used. HEC acts to aggregate the silica, leaving less to react to form clay. The clay platelets which result from HEC are small, not stacked to a large degree, and oriented randomly. Neutral HPMC acts more like cationic PDDA in that larger clay platelets are allowed to form. The extended microstructure of the clay network remains undisturbed after polymer is removed by calcination. When no polymer is used, the synthetic hectorite has a N{sub 2} BET surface area of 200 M{sup 2}/gm, even after calcination. This increases by 20--50% for the synthetic polymer-hectorites after the polymer is removed by calcination.

  7. Understanding Toughness in Bioinspired Cellulose Nanofibril/Polymer Nanocomposites.

    PubMed

    Benítez, Alejandro J; Lossada, Francisco; Zhu, Baolei; Rudolph, Tobias; Walther, Andreas

    2016-07-11

    Cellulose nanofibrils (CNFs) are considered next generation, renewable reinforcements for sustainable, high-performance bioinspired nanocomposites uniting high stiffness, strength and toughness. However, the challenges associated with making well-defined CNF/polymer nanopaper hybrid structures with well-controlled polymer properties have so far hampered to deduce a quantitative picture of the mechanical properties space and deformation mechanisms, and limits the ability to tune and control the mechanical properties by rational design criteria. Here, we discuss detailed insights on how the thermo-mechanical properties of tailor-made copolymers govern the tensile properties in bioinspired CNF/polymer settings, hence at high fractions of reinforcements and under nanoconfinement conditions for the polymers. To this end, we synthesize a series of fully water-soluble and nonionic copolymers, whose glass transition temperatures (Tg) are varied from -60 to 130 °C. We demonstrate that well-defined polymer-coated core/shell nanofibrils form at intermediate stages and that well-defined nanopaper structures with tunable nanostructure arise. The systematic correlation between the thermal transitions in the (co)polymers, as well as its fraction, on the mechanical properties and deformation mechanisms of the nanocomposites is underscored by tensile tests, SEM imaging of fracture surfaces and dynamic mechanical analysis. An optimum toughness is obtained for copolymers with a Tg close to the testing temperature, where the soft phase possesses the best combination of high molecular mobility and cohesive strength. New deformation modes are activated for the toughest compositions. Our study establishes quantitative structure/property relationships in CNF/(co)polymer nanopapers and opens the design space for future, rational molecular engineering using reversible supramolecular bonds or covalent cross-linking.

  8. Nanocomposites Based on Thermoplastic Polymers and Functional Nanofiller for Sensor Applications

    PubMed Central

    Coiai, Serena; Passaglia, Elisa; Pucci, Andrea; Ruggeri, Giacomo

    2015-01-01

    Thermoplastic polymers like polyolefins, polyesters, polyamide, and styrene polymers are the most representative commodity plastics thanks to their cost-efficient manufacturing processes, excellent thermomechanical properties and their good environmental compatibility, including easy recycling. In the last few decades much effort has been devoted worldwide to extend the applications of such materials by conferring on them new properties through mixing and blending with different additives. In this latter context, nanocomposites have recently offered new exciting possibilities. This review discusses the successful use of nanostructured dispersed substrates in designing new stimuli-responsive nanocomposites; in particular, it provides an updated description of the synthetic routes to prepare nanostructured systems having the typical properties of thermoplastic polymers (continuous matrix), but showing enhanced optical, conductive, and thermal features dependent on the dispersion topology. The controlled nanodispersion of functional labeled clays, noble metal nanoparticles and carbon nanotubes is here evidenced to play a key role in producing hybrid thermoplastic materials that have been used in the design of devices, such as NLO devices, chemiresistors, temperature and deformation sensors.

  9. Universal Viscosity Behavior of Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Kalathi, Jagannathan T.; Grest, Gary S.; Kumar, Sanat K.

    2012-11-01

    Nonequilibrium molecular dynamics simulations are used to show that the shear viscosity of a polymer melt can be significantly reduced when filled with small energetically neutral nanoparticles, apparently independent of the polymer’s chain length. Analogous to solvent molecules, small nanoparticles act akin to plasticizers and reduce the viscosity of a polymer melt. This effect, which persists for particles whose sizes are as large as the chain size or the entanglement mesh size, whichever is smaller, can be overcome by making the chain-nanoparticle interactions significantly attractive. Our simulations allow us to systematically organize the viscosity data of filled polymer melts, and thus provide a strong basis from which to predict the flow behavior of these commercially important class of materials.

  10. Crazing of nanocomposites with polymer-tethered nanoparticles

    SciTech Connect

    Meng, Dong; Kumar, Sanat K.; Ge, Ting; Robbins, Mark O.; Grest, Gary S.

    2016-09-07

    The crazing behavior of polymer nanocomposites formed by blending polymer grafted nanoparticles with an entangled polymer melt is studied by molecular dynamics simulations. We focus on the three key differences in the crazing behavior of a composite relative to the pure homopolymer matrix, namely, a lower yield stress, a smaller extension ratio, and a grafted chain length dependent failure stress. The yield behavior is found to be mostly controlled by the local nanoparticle-grafted polymer interfacial energy, with the grafted polymer-polymer matrix interfacial structure being of little to no relevance. Increasing the attraction between nanoparticle core and the grafted polymer inhibits void nucleation and leads to a higher yield stress. In the craze growth regime, the presence of “grafted chain” sections of ≈100 monomers alters the mechanical response of composite samples, giving rise to smaller extension ratios and higher drawing stresses than for the homopolymer matrix. As a result, the dominant failure mechanism of composite samples depends strongly on the length of the grafted chains, with disentanglement being the dominant mechanism for short chains, while bond breaking is the failure mode for chain lengths >10Ne, where Ne is the entanglement length.

  11. Crazing of nanocomposites with polymer-tethered nanoparticles

    DOE PAGES

    Meng, Dong; Kumar, Sanat K.; Ge, Ting; ...

    2016-09-07

    The crazing behavior of polymer nanocomposites formed by blending polymer grafted nanoparticles with an entangled polymer melt is studied by molecular dynamics simulations. We focus on the three key differences in the crazing behavior of a composite relative to the pure homopolymer matrix, namely, a lower yield stress, a smaller extension ratio, and a grafted chain length dependent failure stress. The yield behavior is found to be mostly controlled by the local nanoparticle-grafted polymer interfacial energy, with the grafted polymer-polymer matrix interfacial structure being of little to no relevance. Increasing the attraction between nanoparticle core and the grafted polymer inhibitsmore » void nucleation and leads to a higher yield stress. In the craze growth regime, the presence of “grafted chain” sections of ≈100 monomers alters the mechanical response of composite samples, giving rise to smaller extension ratios and higher drawing stresses than for the homopolymer matrix. As a result, the dominant failure mechanism of composite samples depends strongly on the length of the grafted chains, with disentanglement being the dominant mechanism for short chains, while bond breaking is the failure mode for chain lengths >10Ne, where Ne is the entanglement length.« less

  12. Crazing of nanocomposites with polymer-tethered nanoparticles

    NASA Astrophysics Data System (ADS)

    Meng, Dong; Kumar, Sanat K.; Ge, Ting; Robbins, Mark O.; Grest, Gary S.

    2016-09-01

    The crazing behavior of polymer nanocomposites formed by blending polymer grafted nanoparticles with an entangled polymer melt is studied by molecular dynamics simulations. We focus on the three key differences in the crazing behavior of a composite relative to the pure homopolymer matrix, namely, a lower yield stress, a smaller extension ratio, and a grafted chain length dependent failure stress. The yield behavior is found to be mostly controlled by the local nanoparticle-grafted polymer interfacial energy, with the grafted polymer-polymer matrix interfacial structure being of little to no relevance. Increasing the attraction between nanoparticle core and the grafted polymer inhibits void nucleation and leads to a higher yield stress. In the craze growth regime, the presence of "grafted chain" sections of ≈100 monomers alters the mechanical response of composite samples, giving rise to smaller extension ratios and higher drawing stresses than for the homopolymer matrix. The dominant failure mechanism of composite samples depends strongly on the length of the grafted chains, with disentanglement being the dominant mechanism for short chains, while bond breaking is the failure mode for chain lengths >10Ne, where Ne is the entanglement length.

  13. High ion conducting polymer nanocomposite electrolytes using hybrid nanofillers.

    PubMed

    Tang, Changyu; Hackenberg, Ken; Fu, Qiang; Ajayan, Pulickel M; Ardebili, Haleh

    2012-03-14

    There is a growing shift from liquid electrolytes toward solid polymer electrolytes, in energy storage devices, due to the many advantages of the latter such as enhanced safety, flexibility, and manufacturability. The main issue with polymer electrolytes is their lower ionic conductivity compared to that of liquid electrolytes. Nanoscale fillers such as silica and alumina nanoparticles are known to enhance the ionic conductivity of polymer electrolytes. Although carbon nanotubes have been used as fillers for polymers in various applications, they have not yet been used in polymer electrolytes as they are conductive and can pose the risk of electrical shorting. In this study, we show that nanotubes can be packaged within insulating clay layers to form effective 3D nanofillers. We show that such hybrid nanofillers increase the lithium ion conductivity of PEO electrolyte by almost 2 orders of magnitude. Furthermore, significant improvement in mechanical properties were observed where only 5 wt % addition of the filler led to 160% increase in the tensile strength of the polymer. This new approach of embedding conducting-insulating hybrid nanofillers could lead to the development of a new generation of polymer nanocomposite electrolytes with high ion conductivity and improved mechanical properties. © 2012 American Chemical Society

  14. Crazing of nanocomposites with polymer-tethered nanoparticles

    SciTech Connect

    Meng, Dong; Kumar, Sanat K.; Ge, Ting; Robbins, Mark O.; Grest, Gary S.

    2016-09-07

    The crazing behavior of polymer nanocomposites formed by blending polymer grafted nanoparticles with an entangled polymer melt is studied by molecular dynamics simulations. We focus on the three key differences in the crazing behavior of a composite relative to the pure homopolymer matrix, namely, a lower yield stress, a smaller extension ratio, and a grafted chain length dependent failure stress. The yield behavior is found to be mostly controlled by the local nanoparticle-grafted polymer interfacial energy, with the grafted polymer-polymer matrix interfacial structure being of little to no relevance. Increasing the attraction between nanoparticle core and the grafted polymer inhibits void nucleation and leads to a higher yield stress. In the craze growth regime, the presence of “grafted chain” sections of ≈100 monomers alters the mechanical response of composite samples, giving rise to smaller extension ratios and higher drawing stresses than for the homopolymer matrix. As a result, the dominant failure mechanism of composite samples depends strongly on the length of the grafted chains, with disentanglement being the dominant mechanism for short chains, while bond breaking is the failure mode for chain lengths >10Ne, where Ne is the entanglement length.

  15. Photoluminescence quenching of conjugated polymer nanocomposites for gamma ray detection

    NASA Astrophysics Data System (ADS)

    Zhong, Haizheng; Zhao, Yong Sheng; Li, Yongfang; Pei, Qibing

    2008-12-01

    The high atomic number of bismuth iodide and the high-sensitivity photoluminescence quenching of conjugated polymers are leveraged in their nanocomposites for the detection of high-energy photons. With the introduction of oleylamine, the composites can be processed from solutions in organic solvent into high-quality films containing as much as 50 wt% BiI3. BiI3 in the resulting ternary composites is dispersed on a nanoscale or smaller, allowing the formation of transparent composites. Oleylamine was found to form an interfacial layer between the polymer matrix and BiI3 nanodomains to block charge transfer between BiI3 and the polymer. Upon gamma ray exposure, the luminescent intensity of the ternary composites decreased linearly with the radiation dosage.

  16. Preparation and Characterization of Novel Polymer/Silicate Nanocomposites

    SciTech Connect

    Harrup, Mason Kurt; Wertsching, Alan Kevin

    2002-01-01

    Nanocomposite materials with an inorganic glass and an organic polymerconstitute a relatively new and unique area in material science. The term “ormocers”, “ormosils” and “ceramers” are often utilized to describe this class of nanocomposite (1, 2). By combining at the molecular level inorganic and organic polymeric material a blending of unique physical properties can be achieved. The value in these materials is apparent, from fiber optics to paints these materials may provide the requisite physical properties to achieve the next technological advance. There are several different ways of synthesizing this class ofnanocomposite; therefore a means of classification is necessary. Most developed nomenclature is based on synthetic techniques; Wilkes has arelatively recent and exhaustive categorization (3). However we chose to classify these materials upon a simpler system first suggested by Novak (4).

  17. Nanocomposites of carbon nanotube fibers prepared by polymer crystallization.

    PubMed

    Zhang, Shanju; Lin, Wei; Wong, Ching-Ping; Bucknall, David G; Kumar, Satish

    2010-06-01

    Nanocomposites of carbon nanotube fibers have been prepared using controlled polymer crystallization confined in nanotube aerogel fibers. The polyethylene nanocomposites have been investigated by means of polarized optical microscopy (POM), scanning electron microscopy (SEM) and wide-angle X-ray diffraction (WAXD). The individual nanotubes are periodically decorated with polyethylene nanocrystals, forming aligned hybrid shish-kebab nanostructures. After melting and recrystallization, transcrystalline lamellae connecting the adjacent aligned nanotubes develop. Microstructural analysis shows that the nanotubes can nucleate the growth of both orthorhombic and monoclinic crystals of polyethylene in the quiescent state. The tensile strength, modulus, and axial electrical conductivity of these polyethylene/CNT composite fibers are as high as 600 MPa, 60 GPa, and 5000 S/m, respectively.

  18. Synthetic strategies for the generation of molecularly imprinted organic polymers.

    PubMed

    Mayes, A G; Whitcombe, M J

    2005-12-06

    Molecular imprinting is a method of inducing molecular recognition properties in synthetic polymers in response to the presence of a template species during formation of the three-dimensional structure of the polymer. The molecularly imprinted polymers (MIPs) prepared in this way have been termed "plastic antibodies" and combine the robustness of the polymer scaffold with binding properties more readily associated with biological receptors. Smart polymers of this type may find applications in drug delivery, controlled release and monitoring of drug and metabolite concentrations. In this review the main synthetic strategies used in the preparation of imprinted organic polymers are described in terms of the chemical principles used in the templating step. These are illustrated with examples taken from the literature and are classified as covalent, semi-covalent, non-covalent, metal-mediated and non-polar. Finally strategies for the selection of monomers, optimisation and modification of the properties of imprinted polymers are reviewed.

  19. Transient Thermal Stability of Polymer Nanocomposites

    DTIC Science & Technology

    2012-08-01

    Temperatures exceed melting point and degradation temp of base polymer • Nanoclay and Nanotubes provide degradation resistance • Novel TGA-LPH...difference in heating rate 0 500 1000 1500 2000 0 4 8 12 time (ms) S u rf a c e t e m p e ra tu re ( K ) 120mm cannon Use polypropylene as a model...system to investigate degradation kinetics during transient heating Goal of this project Materials Isotactic Polypropylene + 0-50 wt % nanoclay

  20. Synergetic effects of interfacial and spatial confinement in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhao, Weiwei; Su, Yunlan; Wang, Dujin

    2017-08-01

    Dispersing three-dimensional (3D) nanoparticles as the filler into a polymeric component is known to significantly improve the physicochemical properties of the materials and makes them attractive for industrial applications. There are two main contributions to the underlying enhancement mechanism of polymer nanocomposites (PNCs). The first contribution is linked to the interfacial effect, originating from the interaction between polymer and nanoparticles. The packing density, conformation and orientation of adsorbed chains are significantly altered, which results in an interfacial region with different properties from the bulk. The second contribution is attributed to the spatial effect, introduced by confining polymer chains in a restricted space between/among nanoparticles. These two effects are often correlated. The characteristic behavior of polymer chains confined by nanoparticles has already shown to be quite complicated and hence interesting as compared with that of pure polymers. The broad range of influencing factors including the size, content and surface chemistry of nanoparticles as well as the molecular weight and chain ends of polymers were discussed in this review. The controversial issues such as the segmental dynamics at interface, interfacial architecture and the extent of its impact on the bulk phase were summarized, wishing to produce further understanding of PNCs.

  1. Rotational diffusion in polymer nanocomposites as probed by anisotropic particles

    NASA Astrophysics Data System (ADS)

    Clarke, Laura

    2014-03-01

    Metal nanoparticles strongly absorb specific wavelengths of light with no (or only a very weak) radiative relaxation by which to release this energy. As a result, the absorbed energy is efficiently converted to local heat (a photothermal effect). With an effective cross-section of up to 10 times its physical size, each particle acts as a ``super-sized'' absorber even when embedded within a transparent material environment such as a polymer, resulting in dramatic heating originating at the particles. Thus, with spatially-uniform illumination, one can metaphorically reach inside a polymer nanocomposite and apply heat to pre-selected subsets (e.g., causing them to dramatically change properties due to actuation, cross-linking, crystallization, or chemical reaction) without heating the sample surface or strongly affecting the remainder of the material. By utilizing optically-accessible additives including the particles themselves, the thermal gradient from the particle outward can be experimentally determined. In particular, rotational diffusion of anisotropic particles can be used to measure the temperature at the nanoparticle, which is the warmest point in a polymeric film or nanofiber under photothermal heating. Conversely, the same technique can be utilized to measure polymer dynamics in nanocomposites in the immediate vicinity of the particle. Funding: National Science Foundation CMMI-1069108.

  2. Impact of Carbon Nanoparticle Shape on Polymer Dynamics in Nanocomposites

    NASA Astrophysics Data System (ADS)

    Miller, Brad; Dadmun, Mark

    2012-02-01

    In forming quality nanocomposites of carbon-based nanoparticles (CNPs) in a polymer matrix, achieving and maintaining a high degree of dispersion is a crucial problem. One method to attain well-dispersed CNP nanocomposites is to incorporate non-covalent interactions between the CNP and matrix, which also impacts the dynamics of the polymer chain. In this work, T2 NMR relaxometry (T2 NMR) examines the effect on polymer chain dynamics of incorporating CNPs into polystyrene-co-acrylonitrile (SAN) random copolymer matrices. In SAN-CNP composites, the segmental-chain dynamics can be influenced by the non-covalent interactions formed with the nanoparticle (interacting), but are also influenced by the CNP steric bulk alone (non-interacting). The use of T2 NMR allows for the examination of the influence of the extent of non-covalent interactions on this segmental chain level. This segmental level view also allows for the distinction between relaxation dynamics of the interacting and non-interacting regimes. Current data indicates that increased acrylonitrile content in the copolymer results in increased non-covalent interactions and overall slowing of chain dynamics.

  3. Toxicity of pyrolysis gases from some synthetic polymers

    NASA Technical Reports Server (NTRS)

    Hilado, C. J.; Huttlinger, N. V.

    1978-01-01

    Nine samples of synthetic polymers were evaluated for toxicity of pyrolysis gases, using the toxicity screening test method developed at the University of San Francisco. The materials were polyoxymethylene, polyethylene (five samples), polypropylene, polymethyl methacrylate, and polystyrene. Of the five polyethylene samples, three contained known levels of chlorine. These test results were combined with earlier data to provide a comparison of 25 samples of synthetic polymers. Polyoxymethylene appeared to exhibit the greatest toxicity, and polystyrene the least toxicity, under these particular test conditions

  4. Synthesis and applications of electrically conducting polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Ku, Bon-Cheol

    This research focuses on the synthesis and applications of electrically conducting polymer nanocomposites through molecular self-assembly. Two different classes of polymers, polyaniline (PANI) and polyacetylenes have been synthesized by biomimetic catalysis and spontaneous polymerization method. For gas barrier materials, commercially available polymers, poly(allylamine hydrochloride) (PAH) and poly (acrylic acid) (PAA), have also been used and thermally cross-linked. The morphological, optical and electrical properties of amphiphilic polyacetylenes have been studied. Furthermore, barrier properties, permselectivity, pervaporation properties of polyacetylenes/aluminosilicate nanocomposites have been investigated. For processability and electrical properties of carbon nanotube and conducting polymers, substituted ionic polyacetylenes (SIPA) have been covalently incorporated onto single-walled carbon nanotubes (SWNT) using the "grafting-from" technique. In the first study, a nanocomposite film catalyst has been prepared by electrostatic layer-by-layer (ELBL) self-assembly of a polyelectrolyte and a biomimetic catalyst for synthesis of polyaniline. Poly(dimethyl diallylammonium chloride) (PDAC) and hematin have been used as polycation and counter anions, respectively. The absorption spectra by UV-vis-NIR spectroscopy showed that conductive form polyaniline was formed not only as a coating on the surface of the ELBL composites but was also formed in solution. Furthermore, it was found that the reaction rate was affected by pH and concentration of hematin in the multilayers. The feasibility of controlled desorption of hematin molecules from the LBL assembly was explored and demonstrated by changing the pH and hematin concentration. The polymerization rate of aniline in solution was enhanced with decreasing pH of the solutions due to increased desorption of hematin nanoparticles from the multilayers. These ELBL hematin assemblies demonstrated both a way to functionalize

  5. Mechanical characterization of low dimensional nanomaterials and polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Gao, Hongsheng

    This research was aimed to characterize the mechanical properties of low dimensional nanomaterials and polymer nanocomposites, and to study the reinforcing mechanisms of nanoscale reinforcements. The nanomaterials studied were zero-dimensional nanomaterial--cuprous oxide (Cu2O) nanocubes, one-dimensional nanomaterials--silver nanowires and silicon oxide (SiO2) nanowires, and two-dimensional nanomaterial--nanometer-thick montmorillonite clay platelets. The hardness and elastic moduli of solid Cu 2O nanocubes and silver nanowires were measured by directly indenting individual cubes/wires using a nanoindenter. The elastic modulus of amorphous SiO2 nanowires was measured by performing three-point bending on suspended wires with an atomic force microscope (AFM) tip. The elastic modulus of the nanometer-thick clay platelets was assessed by the modulus mapping technique. An array of nanoscale indents was successfully made on a nanowire. The nanowires were cut to the length as needed. The nanoindentation approach permits the direct machining of individual nanowires without complications of conventional lithography. The nanomechanical properties of single-walled carbon nanotube (SWCNT)-reinforced epoxy composites with varying nanotube concentrations were measured by nanoindentation/nanoscratch techniques. Hardness and elastic modulus were measured using a nanoindenter. Viscoelastic properties of the nanocomposites were measured using nanoindentation dynamic mechanical analysis tests. The SWCNT reinforcing mechanisms were further studied by both Halpin-Tsai and Mori-Tanaka theories, which were found applicable to SWCNT-reinforced, amorphous-polymer composites. The possible reinforcing mechanisms that work in polymer-SWCNT composites and reasons responsible for SWCNTs' low mechanical reinforcement were analyzed. Nanoclay-reinforced agarose nanocomposites with varying clay concentrations were structurally and mechanically characterized. Structural characterization was carried

  6. Synthesis of graphene-conjugated polymer nanocomposites for electronic device applications.

    PubMed

    Qi, Xiaoying; Tan, Chaoliang; Wei, Jun; Zhang, Hua

    2013-02-21

    Graphene-based polymer nanocomposites have attracted increasing interest because of their superior physicochemical properties over polymers. Semiconductor conjugated polymers (CPs) with excellent dispersibility and stability, and efficient electronic and optical properties have been recently integrated with graphene to form a new class of functional nanomaterials. In this minireview, we will summarize the recent advances in the development of graphene-CP nanocomposites for electronic device applications.

  7. Phase Stability and Dynamics of nanoparticles in Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Mangal, Rahul; Srivastava, Samanvaya; Archer, Lynden

    In polymer nanocomposites, polymer grafted nanoparticles, where the tethered polymer chains are chemically identical to the host chains, have been reported to irreversibly aggregate if the length of host chains (P) become 5 or more times larger than the length tethered chains (N) due to the autophobic dewetting of the polymer brush. Utilizing Small Angle X-ray scattering as a tool, here we show that by choosing appropriate chemistry one can utilize the enthalpic attractions between the tethered chains and host chains to facilitate uniform nanoparticle dispersion in very large Mw hosts (P/N ~140). A generic phase diagram has also been proposed. Xray Photon Correlation Spectroscopy (XPCS) is employed as a sensitive probe of nanoparticle relaxation dynamics to investigate particle dynamics in these model PNCs. Remarkably, we find that for nanoparticle size D , slightly larger than the tube diameter of the host polymer (a) , particles undergo a transition from normal diffusion to hyperdiffusive relaxation dynamics,. In contrast, for unentangled hosts, diffusive particle relaxation are observed. Our experimental observations are rationalized by finding that nanoparticle motion in entangled melts only disturb sub-chain entangled segments of size comparable to the particle diameter.

  8. Responsive metal/polymer nanocomposites via photothermal effect

    NASA Astrophysics Data System (ADS)

    Seyhan, Merve; Rende, Deniz; Huang, Liping; Malta, Seyda; Ozisik, Rahmi; Baysal, Nihat

    2013-03-01

    The design of fire-safe materials by using flame retardants within polymers requires a fundamental understanding of the physics and dynamics of the heat transport process with in the multiphase systems. We have developed a Lattice-Boltzmann model to simulate the 3-D heat transfer in a two-component system comprised of a polymer matrix and flame retardant nanocomposite fillers. By varying the volume fraction of the fillers, we compared the heat propagation phenomena before and after the percolation of the nano-fillers in the system. We also vary the size, shape, thermal conductivity and heat capacity of the nanofiller to study their effects on the heat dissipation and the time to ignition.

  9. Photothermal Heating via Gold Nanorods within Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Bochinski, Jason; Maity, Somsubhra; Wu, Wei-Chen; Tracy, Joseph; Clarke, Laura

    2015-03-01

    Metal nanoparticles under continuous-wave (cw) optical excitation resonant with their localized surface plasmon exhibit a photothermal effect, efficiently converting the incident light into heat originating from the particle. Gold nanorods (GNRs) dispersed within a transparent material are utilized as such remotely-controlled, nano-sized heaters, with heating properties which can be manipulated and monitored by using control of the polarization direction of the excitation and probe light fields. Steady-state average temperatures within a polymer matrix embedded with GNRs undergoing cw photothermal heating are determined in the immediate vicinity of the GNR by observing the rate of driven physical rotation of the nanorods, and simultaneously across the entire sample by using an independent fluorescence method. Comparing these two observations as the concentration of dispersed GNRs is varied reveals the interplay between local and global heating in these polymer nanocomposite materials. Support from US National Science Foundation (CMMI-0800237, CMMI-106910).

  10. Impact of in situ polymer coating on particle dispersion into solid laser-generated nanocomposites.

    PubMed

    Wagener, Philipp; Brandes, Gudrun; Schwenke, Andreas; Barcikowski, Stephan

    2011-03-21

    The crucial step in the production of solid nanocomposites is the uniform embedding of nanoparticles into the polymer matrix, since the colloidal properties or specific physical properties are very sensitive to particle dispersion within the nanocomposite. Therefore, we studied a laser-based generation method of a nanocomposite which enables us to control the agglomeration of nanoparticles and to increase the single particle dispersion within polyurethane. For this purpose, we ablated targets of silver and copper inside a polymer-doped solution of tetrahydrofuran by a picosecond laser (using a pulse energy of 125 μJ at 33.3 kHz repetition rate) and hardened the resulting colloids into solid polymers. Electron microscopy of these nanocomposites revealed that primary particle size, agglomerate size and particle dispersion strongly depend on concentration of the polyurethane added before laser ablation. 0.3 wt% polyurethane is the optimal polymer concentration to produce nanocomposites with improved particle dispersion and adequate productivity. Lower polyurethane concentration results in agglomeration whereas higher concentration reduces the production rate significantly. The following evaporation step did not change the distribution of the nanocomposite inside the polyurethane matrix. Hence, the in situ coating of nanoparticles with polyurethane during laser ablation enables simple integration into the structural analogue polymer matrix without additives. Furthermore, it was possible to injection mold these in situ-stabilized nanocomposites without affecting particle dispersion. This clarifies that sufficient in situ stabilization during laser ablation in polymer solution is able to prevent agglomeration even in a hot polymer melt.

  11. High dielectric constant polymer nanocomposites for embedded capacitor applications

    NASA Astrophysics Data System (ADS)

    Lu, Jiongxin

    Driven by ever growing demands of miniaturization, increased functionality, high performance and low cost for microelectronic products and packaging, embedded passives will be one of the key emerging techniques for realizing the system integration which offer various advantages over traditional discrete components. Novel materials for embedded capacitor applications are in great demand, for which a high dielectric constant ( k), low dielectric loss and process compatibility with printed circuit boards are the most important prerequisites. To date, no available material satisfies all these prerequisites and research is needed to develop materials for embedded capacitor applications. Conductive filler/polymer composites are likely candidate material because they show a dramatic increase in their dielectric constant close to the percolation threshold. One of the major hurdles for this type of high-k composites is the high dielectric loss inherent in these systems. In this research, material and process innovations were explored to design and develop conductive filler/polymer nanocomposites based on nanoparticles with controlled parameters to fulfill the balance between sufficiently high-k and low dielectric loss, which satisfied the requirements for embedded capacitor applications. This work involved the synthesis of the metal nanoparticles with different parameters including size, size distribution, aggregation and surface properties, and an investigation on how these varied parameters impact the dielectric properties of the high-k nanocomposites incorporated with these metal nanoparticles. The dielectric behaviors of the nanocomposites were studied systematically over a range of frequencies to determine the dependence of dielectric constant, dielectric loss tangent and dielectric strength on these parameters.

  12. Synthetic Polymers from Readily Available Monosaccharides

    NASA Astrophysics Data System (ADS)

    Galbis, J. A.; García-Martín, M. G.

    The low degradability of petroleum-based polymers and the massive use of these materials constitute a serious problem because of the environmental pollution that they can cause. Thus, sustained efforts have been extensively devoted to produce new polymers based on natural renewing resources and with higher degradability. Of the different natural sources, carbohydrates stand out as highly convenient raw materials because they are inexpensive, readily available, and provide great stereochemical diversity. New polymers, analogous to the more accredited technical polymers, but based on chiral monomers, have been synthesized from natural and available sugars. This chapter describes the potential of sugar-based monomers as precursors to a wide variety of macromolecular materials.

  13. Polymer Based Nanocomposites for Solar Energy Conversion

    SciTech Connect

    Shaheen, S.; Olson, D.; White, M.; Mitchell, W.; Miedaner, A.; Curtis, C.; Rumbles, G.; Gregg, B.; Ginley, D.

    2005-01-01

    Organic semiconductor-based photovoltaic devices offer the promise of low cost photovoltaic technology that can be manufactured via large-scale, roll-to-roll printing techniques. Existing organic photovoltaic devices are currently limited to solar power conversion efficiencies of 3?5%. This is because of poor overlap between the absorption spectrum of the organic chromophores and the solar spectrum, non-ideal band alignment between the donor and acceptor species, and low charge carrier mobilities. To address these issues, we are investigating the development of dendrimeric organic semiconductors that are readily synthesized with high purity. They also benefit from optoelectronic properties, such as band gap and band positions, which can be easily tuned by substituting different chemical groups into the molecule. Additionally, we are developing nanostructured oxide/conjugated polymer composite photovoltaics. These composites take advantage of the high electron mobilities attainable in oxide semiconductors and can be fabricated using low-temperature solution-based growth techniques. Here, we discuss the synthesis and preliminary device results of these novel materials and composites.

  14. Characterization of Local Mechanical Properties of Polymer Thin Films and Polymer Nanocomposites via AFM indentations

    NASA Astrophysics Data System (ADS)

    Cheng, Xu

    AFM indentation has become a tool with great potential in the characterization of nano-mechanical properties of materials. Thanks to the nanometer sized probes, AFM indentation is capable of capturing the changes of multiple properties within the range of tens of nanometers, such task would otherwise be difficult by using other experiment instruments. Despite the great potentials of AFM indentation, it operates based on a simple mechanism: driving the delicate AFM probe to indent the sample surface, and recording the force-displacement response. With limited information provided by AFM indentation, efforts are still required for any practice to successfully extract the desired nano-scale properties from specific materials. In this thesis, we focus on the mechanical properties of interphase between polymer and inorganic materials. It is known that in nanocomposites, a region of polymer exist around nanoparticles with altered molecular structures and improved properties, which is named as interphase polymer. The system with polymer thin films and inorganic material substrates is widely used to simulate the interphase effect in nanocomposites. In this thesis, we developed an efficient and reliable method to process film/substrate samples and characterize the changes of local mechanical properties inside the interphase region with ultra-high resolution AFM mechanical mapping technique. Applying this newly developed method, the interphase of several film/substrate pairs were examined and compared. The local mechanical properties on the other side of the polymer thin film, the free surface side, was also investigated using AFM indentation equipped with surface modified probes. In order to extract the full spectrum of local elastic modulus inside the surface region in the range of only tens of nanometers, the different contact mechanics models were studied and compared, and a Finite Element model was also established. Though the film/substrate system has been wide used as

  15. Polymer-Silica Nanocomposites: A Versatile Platform for Multifunctional Materials

    NASA Astrophysics Data System (ADS)

    Chiu, Chi-Kai

    Solution sol-gel synthesis is a versatile approach to create polymer-silica nanocomposite materials. The solution-to-solid transformation results in a solid consisting of interconnected nanoporous structure in 3D space, making it the ideal material for filtration, encapsulation, optics, electronics, drug release, and biomaterials, etc. Although the pore between nano and meso size may be tunable using different reaction conditions, the intrinsic properties such as limited diffusion within pore structure, complicated interfacial interactions at the pore surfaces, shrinkage and stress-induced cracking and brittleness have limited the applications of this material. To overcome these problems, diffusion, pore size, shrinkage and stress-induced defects need further investigation. Thus, the presented thesis will address these important questions such as whether these limitations can be utilized as the novel method to create new materials and lead to new applications. First, the behaviors of polymers such as poly(ethylene glycol) inside the silica pores are examined by studying the nucleation and growth of AgCl at the surface of the porous matrix. The pore structure and the pressure induced by the shrinkage affect have been found to induce the growth of AgCl nanocrystals. When the same process is carried out at 160 °C, silver metallization is possible. Due to the shrinkage-induced stresses, the polymer tends to move into open crack spaces and exterior surfaces, forming interconnected silver structure. This interconnected silver structure is very unique because its density is not related to the size scale of nanopore structures. These findings suggest that it is possible to utilize defect surface of silica material as the template to create interconnected silver structure. When the scale is small, polymer may no longer be needed if the diffusion length of Ag is more than the size of silica particles. To validate our assumption, monoliths of sol-gel sample containing AgNO3

  16. Structural Characterization of Polymer-Clay Nanocomposites Prepared by Co-Precipitation Using EPR Techniques

    PubMed Central

    Kielmann, Udo; Jeschke, Gunnar; García-Rubio, Inés

    2014-01-01

    Polymer-clay nanocomposites (PCNCs) containing either a rubber or an acrylate polymer were prepared by drying or co-precipitating polymer latex and nanolayered clay (synthetic and natural) suspensions. The interface between the polymer and the clay nanoparticles was studied by electron paramagnetic resonance (EPR) techniques by selectively addressing spin probes either to the surfactant layer (labeled stearic acid) or the clay surface (labeled catamine). Continuous-wave (CW) EPR studies of the surfactant dynamics allow to define a transition temperature T* which was tentatively assigned to the order-disorder transition of the surfactant layer. CW EPR studies of PCNC showed that completely exfoliated nanoparticles coexist with agglomerates. HYSCORE spectroscopy in PCNCs showed couplings within the probe −assigned with DFT computations− and couplings with nuclei of the environment, 1H and 23Na for the surfactant layer probe, and 29Si, 7Li, 19F and 23Na for the clay surface probe. Analysis of these couplings indicates that the integrity of the surfactant layer is conserved and that there are sizeable ionic regions containing sodium ions directly beyond the surfactant layer. Simulations of the very weak couplings demonstrated that the HYSCORE spectra are sensitive to the composition of the clay and whether or not clay platelets stack. PMID:28788520

  17. Enantiomeric differentiation by synthetic helical polymers.

    PubMed

    Yashima, Eiji; Iida, Hiroki; Okamoto, Yoshio

    2013-01-01

    Recent advances in the synthesis of helical polymers and their applications as chiral materials, in particular chiral stationary phases (CSPs), for high-performance liquid chromatography (HPLC) are reviewed with an emphasis on the key role of the helical conformations with one-handedness for the prominent chiral recognition of enantiomers. The historical background of artificial optically active helical polymers is also briefly described.

  18. High-aspect ratio magnetic nanocomposite polymer cilium

    NASA Astrophysics Data System (ADS)

    Rahbar, M.; Tseng, H. Y.; Gray, B. L.

    2014-03-01

    This paper presents a new fabrication technique to achieve ultra high-aspect ratio artificial cilia micro-patterned from flexible highly magnetic rare earth nanoparticle-doped polymers. We have developed a simple, inexpensive and scalable fabrication method to create cilia structures that can be actuated by miniature electromagnets, that are suitable to be used for lab-on-a chip (LOC) and micro-total-analysis-system (μ-TAS) applications such as mixers and flow-control elements. The magnetic cilia are fabricated and magnetically polarized directly in microfluidic channels or reaction chambers, allowing for easy integration with complex microfluidic systems. These cilia structures can be combined on a single chip with other microfluidic components employing the same permanently magnetic nano-composite polymer (MNCP), such as valves or pumps. Rare earth permanent magnetic powder, (Nd0.7Ce0.3)10.5Fe83.9B5.6, is used to dope polydimethylsiloxane (PDMS), resulting in a highly flexible M-NCP of much higher magnetization and remanence [1] than ferromagnetic polymers typically employed in magnetic microfluidics. Sacrificial poly(ethylene-glycol) (PEG) is used to mold the highly magnetic polymer into ultra high-aspect ratio artificial cilia. Cilia structures with aspect ratio exceeding 8:0.13 can be easily fabricated using this technique and are actuated using miniature electromagnets to achieve a high range of motion/vibration.

  19. Coarse graining of star-polymer - colloid nanocomposites

    NASA Astrophysics Data System (ADS)

    Marzi, Daniela; Likos, Christos N.; Capone, Barbara

    2012-07-01

    We consider mixtures of self-avoiding multiarm star polymers with hard colloids that are smaller than the star polymer size. By employing computer simulations, and by extending previous theoretical approaches, developed for the opposite limit of small star polymers [A. Jusufi et al., J. Phys.: Condens. Matter 13, 6177 (2001), 10.1088/0953-8984/13/28/303], we coarse-grain the mixture by deriving an effective cross-interaction between the unlike species. The excellent agreement between theory and simulation for all size ratios examined demonstrates that the theoretical approaches developed for the colloidal limit can be successfully modified to maintain their validity also for the present case of the protein limit, in contrast to the situation for mixtures of colloids and linear polymers. We further analyze, on the basis of the derived interactions, the non-additivity parameter of the mixture as a function of size ratio and star functionality and delineate the regions in which we expect mixing as opposed to demixing behavior. Our results are relevant for the study of star-colloid nanocomposites and pave the way for further investigations of the structure and thermodynamics of the same.

  20. An interface controlled dynamic stiffening in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Senses, Erkan; Akcora, Pinar

    2013-03-01

    Tunable interfaces between inorganic and organic phases determine the mechanical behavior of responsive and adaptive composites. We present that bonding/debonding of chains on nanoparticles can be modulated with extensive periodic strains. Mechanical response of an attractive model polymer composite, poly(methyl methacrylate) filled with silica nanoparticles of sizes 13 nm and 56 nm, is monitored in series of deformation-resting experiments allowing us to tune the interfacial strength of polymer. We show that this deformation process exhibit unusual stiffening of composites as the matrix polymer is bound to the surface stronger on removal of strain. Mechanical response during the recovery together with SANS and FTIR analysis of the composites at different states of deformation reveal that this behavior arises from enhancement in the entanglement of chains at interfaces. We studied the effects of strain amplitude, confinement parameter (ID/2Rg) and resting time and found that the stiffening is manifest only after large strains. This behavior offers an `on demand' reinforcement properties to polymer nanocomposites, implying that the composites with attractive interfaces can self-stiffen as needed.

  1. Anisotropic Polymer Conformations in Aligned SWCNT/PS Nanocomposites

    NASA Astrophysics Data System (ADS)

    Tung, Wei-Shao; Composto, Russell; Clarke, Nigel; Winey, Karen

    2015-03-01

    In our previous study of isotropic SWCNT/polystyrene (PS) nanocomposites, we found that the polymer radius of gyration (Rg) increases and the SWCNT mesh size decreases with increasing SWCNT concentration. Here, we investigate the effect of aligning SWCNTs on Rg and the SWNCT mesh. SWCNT alignment was accomplished by melt fiber spinning or extrusion, and small angle neutron scattering was used to probe the structure. As expected, SWCNT alignment produces anisotropic meshes. Below 2 wt% SWCNT, no significant change in Rg is observed and Rg parallel and perpendicular to the direction of SWCNT alignment are comparable. More interestingly, at higher wt% SWCNT the polymer conformations are anisotropic with a larger Rg perpendicular to the SWCNT than along the SWCNT. For example, with 6 wt% SWCNT, the Rg perpendicular to the SWCNT is ~ 15% larger than parallel to the SWNCT. This anisotropy in the polymer conformation becomes more prominent at higher SWCNT concentrations, perhaps because at higher SWCNT concentrations the distribution of mesh shifts to smaller meshes (<2Rg) so that a single polymer chain interacts with multiple SWCNTs. Implications of this finding will be discussed. National Science Foundation DMR-12-10379.

  2. Molecular interactions alter clay and polymer structure in polymer clay nanocomposites.

    PubMed

    Sikdar, Debashis; Katti, Kalpana S; Katti, Dinesh R

    2008-04-01

    In this work, using photoacoustic Fourier transform infrared spectroscopy (FTIR) we have studied the structural distortion of clay crystal structure in organically modified montmorillonite (OMMT) and polymer clay nanocomposites (PCN). To study the effect of organic modifiers on the distortion of crystal structure of clay, we have synthesized OMMTs and PCNs containing same polymer and clay but with three different organic modifiers (12-aminolauric acid, n-dodecylamine, and 1,12-diaminododecane), and conducted the FTIR study on these PCNs. Our previous molecular dynamics (MD) study on these PCNs reveals that significant nonbonded interactions (van der Waals, electrostatic interactions) exist between the different constituents (polymer, organic modifier, and clay) of nanocomposites. Previous work based on X-ray diffraction (XRD) and differential scanning calorimetry (DSC) on the same set of PCNs shows that crystallinity of polymer in PCNs have changed significantly in comparison to those in pristine polymer; and, the nonbonded interactions between different constituents of PCN are responsible for the change in crystal structure of polymer in PCN. In this work to evaluate the structural distortion of crystal structure of clay in OMMTs and PCNs, the positions of bands corresponding to different modes of vibration of Si-O bonds are determined from the deconvolution of broad Si-O bands in OMMTs and PCNs obtained from FTIR spectra. Intensity and area under the Si-O bands are indicative of orientation of clay crystal structures in OMMTs and PCNs. Significant changes in the Si-O bands are observed from each vibration mode in OMMTs and PCNs containing three different organic modifiers indicating that organic modifiers influence the structural orientation of silica tetrahedra in OMMTs and PCNs. Deconvolution of Si-O bands in OMMTs indicate a band at approximately 1200 cm(-1) that is orientation-dependent Si-O band. The specific changes in intensity and area under this band for

  3. Copper-polymer nanocomposites: An excellent and cost-effective biocide for use on antibacterial surfaces.

    PubMed

    Tamayo, Laura; Azócar, Manuel; Kogan, Marcelo; Riveros, Ana; Páez, Maritza

    2016-12-01

    The development of polymer nanocomposites with antimicrobial properties has been a key factor for controlling or inhibiting the growth of microorganisms and preventing foodborne diseases and nosocomial infections. Commercially available antibacterial products based on silver-polymer are the most widely used despite the fact that copper is considerably less expensive. The incorporation of copper nanoparticles as antibacterial agents in polymeric matrices to generate copper-polymer nanocomposites have presented excellent results in inhibiting the growth of a broad spectrum of microorganisms. The potential applications in food packaging, medical devices, textiles and pharmaceuticals and water treatment have generated an increasing number of investigations on preparing copper based nanocomposites and alternative polymeric matrices, as potential hosts of nano-modifiers. This review presents a comprehensive compilation of previous published work on the subject, mainly related to the antimicrobial activity of copper polymer nanocomposites. Within all the phenomenology associated to antibacterial effects we highlight the possible mechanisms of action. We discuss the differences in the susceptibility of Gram negative and positive bacteria to the antibacterial activity of nanocomposites, and influencing factors. As well, the main applications of copper polymer-metal nanocomposites are described, considering their physical and chemical characteristics. Finally, some commercially available copper-polymer nanocomposites are described. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Rheological behavior of poly(lactic acid)/synthetic mica nanocomposites.

    PubMed

    Souza, D H S; Andrade, C T; Dias, M L

    2013-04-01

    Poly(lactic acid) nanocomposites were prepared with three synthetic fluoromicas in a twin-screw extruder. Sodium and two organomodified synthetic fluoromicas at different compositions were used. The effect of mica type and composition on the rheological behavior of the nanocomposites was evaluated. The sodium fluoromica did not have a significant effect on the poly(lactic acid) rheological properties, while addition of the organophilic micas to poly(lactic acid) has a strong effect on the rheology, showing a pronounced shear thinning behavior. The dynamic rheological studies revealed that the nanocomposites with organomica have a higher viscosity and more pronounced elastic properties than neat poly(lactic acid). Both storage and loss moduli increased with mica content.

  5. Synthesis and characterization of metal-polymer nanocomposites with radiation-protective properties

    NASA Astrophysics Data System (ADS)

    Bychkov, A. N.; Dzhardimalieva, G. I.; Fetisov, G. P.; Valskiy, V. V.; Golubeva, N. D.; Pomogailo, A. D.

    2016-12-01

    Metal-polymer nanocomposites, which can weaken the activity of a beta radiation source in undesirable directions at the minimum protection size, are developed. These nanocomposites are fabricated by dispersing metal-containing nanoparticles in thermoplastic matrices. Metal nanoparticles are synthesized by the polymerassisted thermolysis of metal-containing precursors. The composition and structure of the nanocomposites are characterized by elemental and X-ray diffraction analyses and transmission electron microscopy.

  6. High-density polymer microarrays: identifying synthetic polymers that control human embryonic stem cell growth.

    PubMed

    Hansen, Anne; Mjoseng, Heidi K; Zhang, Rong; Kalloudis, Michail; Koutsos, Vasileios; de Sousa, Paul A; Bradley, Mark

    2014-06-01

    The fabrication of high-density polymer microarray is described, allowing the simultaneous and efficient evaluation of more than 7000 different polymers in a single-cellular-based screen. These high-density polymer arrays are applied in the search for synthetic substrates for hESCs culture. Up-scaling of the identified hit polymers enables long-term cellular cultivation and promoted successful stem-cell maintenance.

  7. Toxicity of pyrolysis gases from synthetic polymers

    NASA Technical Reports Server (NTRS)

    Hilado, C. J.; Soriano, J. A.; Kosola, K. L.; Kourtides, D. A.; Parker, J. A.

    1977-01-01

    The screening test method was used to investigate toxicity in polyethylene, polystyrene, polymethyl methacrylate, polyaryl sulfone, polyether sulfone, polyphenyl sulfone, and polyphenylene sulfide. Changing from a rising temperature program to a fixed temperature program resulted on shorter times to animal responses. This effect was attributed in part to more rapid generation of toxicants. The toxicants from the sulfur containing polymers appeared to act more rapidly than the toxicants from the other polymers. It was not known whether this effect was due primarily to difference in concentration or in the nature of the toxicants. The carbon monoxide concentration found did not account for the results observed with the sulfur containing polymers. Polyphenyl sulfone appeared to exhibit the least toxicity among the sulfur containing polymers evaluated under these test conditions.

  8. Nanocomposites

    DTIC Science & Technology

    2013-09-10

    Research Triangle Park, NC 27709-2211 15. SUBJECT TERMS nanocomposite, polymer, rheology , tensile modulus Michael E. Mackay, PhD University of Delaware...published in peer-reviewed journals (N/A for none) Enter List of papers submitted or published that acknowledge ARO support from the start of the project to...the date of this printing. List the papers, including journal references, in the following categories: Received Paper TOTAL: (b) Papers published

  9. Investigation of the structure and thermal behaviour of polymer liquid crystal / single wall carbon nanotubes nanocomposite

    NASA Astrophysics Data System (ADS)

    Exner, G.; Marinov, Y.; Perez, E.

    2017-01-01

    In the present work, nanocomposite of thermotropic polymer liquid crystal poly(heptane-1,7-dyil biphenyl-4,4’-dicarboxilate) and single wall carbon nanotubes was investigated. Nanocomposite films were casted from solution blended polymer liquid crystal and nanotubes. The structure and thermal behaviour of the nanocomposite were investigated by means of X-ray scattering and differential scanning calorimetry. The results show that there are two phase transitions on cooling and a single one on subsequent heating for both the neat polymer liquid crystal and nanocomposite. Hence, the smectic order of the polymer liquid crystal as well as its monotropic behaviour are preserved in the nanocomposite. The isotropic melt - smectic transition temperature in the nanocomposite is several degrees higher and the enthalpy of this process is much lower, suggesting heterogeneous nucleation of this phase on the surface of the nanotubes. The temperature of crystal structure formation during further cooling decreases in the nanocomposite showing a stabilization effect of the nanotubes on the smectic phase. Judging from the smaller enthalpy of the smectic-crystal phase transition and the new crystalline peak in the X-ray scattering patterns of the nanocomposite one could suggest a new crystalline form formation and this crystalline phase coexistence with smectic phases at lower temperatures.

  10. Measurement of Nanoparticles Release during Drilling of Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Gendre, L.; Marchante Rodriguez, V.; Abhyankar, H.; Blackburn, K.; Brighton, J. L.

    2015-05-01

    Nanomaterials are one of the promising technologies of this century. The Project on Emerging Nanotechnologies [1] reports more than 1600 consumer products based on nanotechnology that are currently on the market and advantages link to the reinforcement of polymeric materials using nano-fillers are not to demonstrate anymore. However, the concerns about safety and its consumer perception can slow down the acceptance of nanocomposites. Indeed, during its life-cycle, a nanotechnology-based product can release nano-sized particles exposing workers, consumers and environment and the risk involved in the use and disposal of such particles is not well known. The current legislation concerning chemicals and environment protection doesn't explicitly cover nanomaterials and changes undergone by nanoparticles during the products’ life cycle. Also, the possible physio-chemical changes that the nanoparticles may undergo during its life cycle are unknown. Industries need a standard method to evaluate nanoparticles release during products’ life cycle in order to improve the knowledge in nanomaterials risk assessment and the legislation, and to inform customers about the safety of nanomaterials and nanoproducts. This work aims to propose a replicable method in order to assess the release of nanoparticles during the machining of nanocomposites in a controlled environment. For this purpose, a new experimental set-up was implemented and issues observed in previous methods (background noise due to uncontrolled ambient environment and the process itself, unrepeatable machining parameters) were solved. A characterisation and validation of the chamber used is presented in this paper. Also, preliminary testing on drilling of polymer-based nanocomposites (Polyamide-6/Glass Fibre reinforced with nano-SiO2) manufactured by extrusion and injection moulding were achieved.

  11. [New polymer-drug systems based on natural and synthetic polymers].

    PubMed

    Racoviţă, Stefania; Vasiliu, Silvia; Foia, Liliana

    2010-01-01

    The great versatility of polymers makes them very useful in the biomedical and pharmaceutical fields. The combination of natural and synthetic polymers leads to new materials with tailored functional properties. The aim of this work consists in the preparation of new drug delivery system based on chitosan (natural polymer) and polybetaines (synthetic polymers), by a simple process, well known in the literature as complex coacervation methods. Also, the adsorption and release studies of two antibiotics as well as the preservation of their bactericidal capacities were performed.

  12. Investigation on the Electrical Properties of Polymer metal Nanocomposites for Physiological Sensing Applications

    NASA Astrophysics Data System (ADS)

    Vijayakumari, G.; Selvakumar, N.; Jeyasubramanian, K.; Mala, R.

    Copper nanoparticles were prepared by Polyol Method and the prepared metal nanoparticles were characterized by various techniques like AFM, SEM, FTIR Spectrum and XRD. The prepared metal nanoparticles are used to improve the electrical conductivity of dielectric polymers like PMMA. Polymer Metal Nanocomposite was prepared by in-situ oxidative polymerization of Methylmethacrylate monomer in the presence of different concentration of prepared metal nanoparticles. The formation of the polymer metal nanocomposites was characterized by UV-Vis Spectroscopy, SEM and AFM. The electrical conductivity was investigated using Four-Point Probe Techniques and the conductivity value of the PMMA/Cu nanocomposite was in the range of mS/cm. The conductivity of the dielectric polymer was found to be increased with the increasing metal concentration. The prepared nanocomposite can be used to convert the insulating foam into conductive one which can be used to fabricate wearable sensors for physiological (Breath Rate, Limb Movement, etc.,) monitoring.

  13. Dynamics at the Polymer/Nanoparticle Interface in Poly(2-vinylpyridine)/Silica Nanocomposites.

    SciTech Connect

    Holt, Adam P; Griffin, Phillip; Bocharova, Vera; Agapov, Alexander L; Imel, Adam E; Dadmun, Mark D; Sangoro, Joshua R; Sokolov, Alexei P

    2014-01-01

    The static and dynamic properties of poly(2-vinylpyridine)/silica nanocomposites are investigated by temperature modulated differential scanning calorimetry, broadband dielectric spectroscopy (BDS), small-angle X-ray scattering (SAXS), and transmission electron microscopy. Both BDS and SAXS detect the existence of an interfacial polymer layer on the surface of nanoparticles. The results show that whereas the calorimetric glass transition temperature varies only weakly with nanoparticle loading, the segmental mobility of the polymer interfacial layer is slower than the bulk polymer by 2 orders of magnitude. Detailed analysis of BDS and SAXS data reveal that the interfacial layer has a thickness of 4 6 nm irrespective of the nanoparticle concentration. These results demonstrate that in contrast to some recent articles on polymer nanocomposites, the interfacial polymer layer is by no means a dead layer . However, its existence might provide some explanation for controversies surrounding the dynamics of polymer nanocomposites.

  14. Simulation of bipolar charge transport in nanocomposite polymer films

    NASA Astrophysics Data System (ADS)

    Lean, Meng H.; Chu, Wei-Ping L.

    2015-03-01

    This paper describes 3D particle-in-cell simulation of bipolar charge injection and transport through nanocomposite film comprised of ferroelectric ceramic nanofillers in an amorphous polymer matrix. The classical electrical double layer (EDL) model for a monopolar core is extended (eEDL) to represent the nanofiller by replacing it with a dipolar core. Charge injection at the electrodes assumes metal-polymer Schottky emission at low to moderate fields and Fowler-Nordheim tunneling at high fields. Injected particles migrate via field-dependent Poole-Frenkel mobility and recombine with Monte Carlo selection. The simulation algorithm uses a boundary integral equation method for solution of the Poisson equation coupled with a second-order predictor-corrector scheme for robust time integration of the equations of motion. The stability criterion of the explicit algorithm conforms to the Courant-Friedrichs-Levy limit assuring robust and rapid convergence. The model is capable of simulating a wide dynamic range spanning leakage current to pre-breakdown. Simulation results for BaTiO3 nanofiller in amorphous polymer matrix indicate that charge transport behavior depend on nanoparticle polarization with anti-parallel orientation showing the highest leakage conduction and therefore lowest level of charge trapping in the interaction zone. Charge recombination is also highest, at the cost of reduced leakage conduction charge. The eEDL model predicts the meandering pathways of charge particle trajectories.

  15. Thermal Diffusivity Mapping of Graphene Based Polymer Nanocomposites.

    PubMed

    Gresil, Matthieu; Wang, Zixin; Poutrel, Quentin-Arthur; Soutis, Constantinos

    2017-07-17

    Nanoparticle dispersion is widely recognised as a challenge in polymer nanocomposites fabrication. The dispersion quality can affect the physical and thermomechanical properties of the material system. Qualitative transmission electronic microscopy, often cumbersome, remains as the 'gold standard' for dispersion characterisation. However, quantifying dispersion at macroscopic level remains a difficult task. This paper presents a quantitative dispersion characterisation method using non-contact infrared thermography mapping that measures the thermal diffusivity (α) of the graphene nanocomposite and relates α to a dispersion index. The main advantage of the proposed method is its ability to evaluate dispersion over a large area at reduced effort and cost, in addition to measuring the thermal properties of the system. The actual resolution of this thermal mapping reaches 200 µm per pixel giving an accurate picture of graphene nanoplatelets (GNP) dispersion. The post-dispersion treatment shows an improvement in directional thermal conductivity of the composite of up to 400% increase at 5 wt% of GNP. The Maxwell-Garnet effective medium approximation is proposed to estimate thermal conductivity that compare favourably to measured data. The development of a broadly applicable dispersion quantification method will provide a better understanding of reinforcement mechanisms and effect on performance of large scale composite structures.

  16. Predictive Model of Graphene Based Polymer Nanocomposites: Electrical Performance

    NASA Astrophysics Data System (ADS)

    Manta, Asimina; Gresil, Matthieu; Soutis, Constantinos

    2016-11-01

    In this computational work, a new simulation tool on the graphene/polymer nanocomposites electrical response is developed based on the finite element method (FEM). This approach is built on the multi-scale multi-physics format, consisting of a unit cell and a representative volume element (RVE). The FE methodology is proven to be a reliable and flexible tool on the simulation of the electrical response without inducing the complexity of raw programming codes, while it is able to model any geometry, thus the response of any component. This characteristic is supported by its ability in preliminary stage to predict accurately the percolation threshold of experimental material structures and its sensitivity on the effect of different manufacturing methodologies. Especially, the percolation threshold of two material structures of the same constituents (PVDF/Graphene) prepared with different methods was predicted highlighting the effect of the material preparation on the filler distribution, percolation probability and percolation threshold. The assumption of the random filler distribution was proven to be efficient on modelling material structures obtained by solution methods, while the through-the -thickness normal particle distribution was more appropriate for nanocomposites constructed by film hot-pressing. Moreover, the parametrical analysis examine the effect of each parameter on the variables of the percolation law. These graphs could be used as a preliminary design tool for more effective material system manufacturing.

  17. Predictive Model of Graphene Based Polymer Nanocomposites: Electrical Performance

    NASA Astrophysics Data System (ADS)

    Manta, Asimina; Gresil, Matthieu; Soutis, Constantinos

    2017-04-01

    In this computational work, a new simulation tool on the graphene/polymer nanocomposites electrical response is developed based on the finite element method (FEM). This approach is built on the multi-scale multi-physics format, consisting of a unit cell and a representative volume element (RVE). The FE methodology is proven to be a reliable and flexible tool on the simulation of the electrical response without inducing the complexity of raw programming codes, while it is able to model any geometry, thus the response of any component. This characteristic is supported by its ability in preliminary stage to predict accurately the percolation threshold of experimental material structures and its sensitivity on the effect of different manufacturing methodologies. Especially, the percolation threshold of two material structures of the same constituents (PVDF/Graphene) prepared with different methods was predicted highlighting the effect of the material preparation on the filler distribution, percolation probability and percolation threshold. The assumption of the random filler distribution was proven to be efficient on modelling material structures obtained by solution methods, while the through-the -thickness normal particle distribution was more appropriate for nanocomposites constructed by film hot-pressing. Moreover, the parametrical analysis examine the effect of each parameter on the variables of the percolation law. These graphs could be used as a preliminary design tool for more effective material system manufacturing.

  18. Anisotropic piezoresistivity characteristics of aligned carbon nanotube-polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Sengezer, Engin C.; Seidel, Gary D.; Bodnar, Robert J.

    2017-09-01

    Dielectrophoresis under the application of AC electric fields is one of the primary fabrication techniques for obtaining aligned carbon nanotube (CNT)-polymer nanocomposites, and is used here to generate long range alignment of CNTs at the structural level. The degree of alignment of CNTs within this long range architecture is observed via polarized Raman spectroscopy so that its influence on the electrical conductivity and piezoresistive response in both the alignment and transverse to alignment directions can be assessed. Nanocomposite samples consisting of randomly oriented, well dispersed single-wall carbon nanotubes (SWCNTs) and of long range electric field aligned SWCNTs in a photopolymerizable monomer blend (urethane dimethacrylate and 1,6-hexanediol dimethacrylate) are quantitatively and qualitatively evaluated. Piezoresistive sensitivities in form of gauge factors were measured for randomly oriented, well dispersed specimens with 0.03, 0.1 and 0.5 wt% SWCNTs and compared with gauge factors in both the axial and transverse to SWCNT alignment directions for electric field aligned 0.03 wt% specimens under both quasi-static monotonic and cyclic tensile loading. Gauge factors in the axial direction were observed to be on the order of 2, while gauge factors in the transverse direction demonstrated a 5 fold increase with values on the order of 10 for aligned specimens. Based on Raman analysis, it is believed the higher sensitivity of the transverse direction is related to architectural evolution of misaligned bridging structures which connect alignment structures under load due to Poisson’s contraction.

  19. Controlled polymer synthesis--from biomimicry towards synthetic biology.

    PubMed

    Pasparakis, George; Krasnogor, Natalio; Cronin, Leroy; Davis, Benjamin G; Alexander, Cameron

    2010-01-01

    The controlled assembly of synthetic polymer structures is now possible with an unprecedented range of functional groups and molecular architectures. In this critical review we consider how the ability to create artificial materials over lengthscales ranging from a few nm to several microns is generating systems that not only begin to mimic those in nature but also may lead to exciting applications in synthetic biology (139 references).

  20. Controlling the electrical conductive network formation of polymer nanocomposites via polymer functionalization.

    PubMed

    Gao, Yangyang; Wu, Youping; Liu, Jun; Zhang, Liqun

    2016-12-06

    By adopting coarse-grained molecular dynamics simulations, the effect of polymer functionalization on the relationship between the microstructure and the electric percolation probability of nanorod filled polymer nanocomposites has been investigated. At a low chain functionalization degree, the nanorods in the polymer matrix form isolated aggregates with a local order structure. At a moderate chain functionalization degree, the local order structure of the nanorod aggregate is gradually broken up. Meanwhile, excessive functionalization chain beads can connect the isolated aggregates together, which leads to the maximum size of nanorod aggregation. At a high chain functionalization degree, it forms a single nanorod structure in the matrix. As a result, the highest percolation probability of the materials appears at the moderate chain functionalization degree, which is attributed to the formation of the tightly connected nanorod network by analyzing the main cluster. In addition, this optimum chain functionalization degree exists at two chain functionalization modes (random and diblock). Lastly, under the tensile field, even though the contact distance between nanorods nearly remains unchanged, the topological structure of the percolation network is broken down. While under the shear field, the contact distance between nanorods increases and the topological structure of the percolation network is broken down, which leads to a decrease in the percolation probability. In total, the topological structure of the percolation network dominates the percolation probability, which is not a necessary connection with the contact distance between nanorods. In summary, this work presents further understanding of the electric conductive properties of nanorod-filled nanocomposites with functionalized polymers.

  1. Polymer microcapsules with a fiber-reinforced nanocomposite shell.

    PubMed

    Sagis, Leonard M C; Ruiter, Riëlle de; Miranda, Francisco J Rossier; Ruiter, Jolet de; Schroën, Karin; Aelst, Adriaan C van; Kieft, Henk; Boom, Remko; Linden, Erik van der

    2008-03-04

    Polymer microcapsules can be used as controlled release systems in drugs or in foods. Using layer-by-layer adsorption of common food proteins and polysaccharides, we produced a new type of microcapsule with tunable strength and permeability. The shell consists of alternating layers of pectin and whey protein fibrils, yielding a fiber-reinforced nanocomposite shell. The strength can be tightly controlled by varying the number of layers or the density and length of the fibrils in the protein layers. The mechanical stability of these microcapsules appears to be superior to that of currently available multilayer capsules. The method involves only standard unit operations and has the potential for scaling up to industrial production volumes.

  2. Linear viscoelasticity of polymer-graphite nanoplatelets (GNPs) nanocomposites

    NASA Astrophysics Data System (ADS)

    de Luna, Martina Salzano; Acierno, Domenico; Russo, Pietro; Filippone, Giovanni

    2012-07-01

    We prepare well dispersed nanocomposites based on Graphite Nanoplatelets (GNPs) and polystyrene (PS) through a combination of solution and melt mixing techniques. The samples are subjected to morphological, electrical, and rheological investigations. Electron microscopy analyses show that GNPs are well dispersed, and the presence of few nanometers thick GNPs is noticed. The electrical conductivity of the polymer dramatically increases at a critical content of particles of Φ˜4 wt.%, indicating that electrical percolation has occurred. The existence of a percolating network induces a marked elastic connotation in the melt state. We show that the elasticity of GNP networks in samples at different composition can be scaled on a single master curve. This allows for the accurate estimation of the rheological percolation threshold. In addition, using the master curve we can infer the elasticity of GNP networks which are too tenuous to be appreciated via conventional rheological measurements.

  3. Small Particle Driven Chain Disentanglements in Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Senses, Erkan; Ansar, Siyam M.; Kitchens, Christopher L.; Mao, Yimin; Narayanan, Suresh; Natarajan, Bharath; Faraone, Antonio

    2017-04-01

    Using neutron spin-echo spectroscopy, x-ray photon correlation spectroscopy, and bulk rheology, we studied the effect of particle size on the single-chain dynamics, particle mobility, and bulk viscosity in athermal polyethylene oxide-gold nanoparticle composites. The results reveal a ≈25 % increase in the reptation tube diameter with the addition of nanoparticles smaller than the entanglement mesh size (≈5 nm ), at a volume fraction of 20%. The tube diameter remains unchanged in the composite with larger (20 nm) nanoparticles at the same loading. In both cases, the Rouse dynamics is insensitive to particle size. These results provide a direct experimental observation of particle-size-driven disentanglements that can cause non-Einstein-like viscosity trends often observed in polymer nanocomposites.

  4. Multiscale Modeling of Thermal Conductivity of Polymer/Carbon Nanocomposites

    NASA Technical Reports Server (NTRS)

    Clancy, Thomas C.; Frankland, Sarah-Jane V.; Hinkley, Jeffrey A.; Gates, Thomas S.

    2010-01-01

    Molecular dynamics simulation was used to estimate the interfacial thermal (Kapitza) resistance between nanoparticles and amorphous and crystalline polymer matrices. Bulk thermal conductivities of the nanocomposites were then estimated using an established effective medium approach. To study functionalization, oligomeric ethylene-vinyl alcohol copolymers were chemically bonded to a single wall carbon nanotube. The results, in a poly(ethylene-vinyl acetate) matrix, are similar to those obtained previously for grafted linear hydrocarbon chains. To study the effect of noncovalent functionalization, two types of polyethylene matrices. -- aligned (extended-chain crystalline) vs. amorphous (random coils) were modeled. Both matrices produced the same interfacial thermal resistance values. Finally, functionalization of edges and faces of plate-like graphite nanoparticles was found to be only modestly effective in reducing the interfacial thermal resistance and improving the composite thermal conductivity

  5. Magnetically Tunable Polymer Nanocomposites for RF and Microwave Device Applications

    NASA Astrophysics Data System (ADS)

    Stojak, K.; Pal, S.; Srikanth, H.; Morales, C.; Dewdney, J.; Wang, J.; Weller, T.

    2011-03-01

    There has been much interest in polymer nanocomposites (PNC) recently due to potential applications for EMI shielding, tunable electromagnetic devices and flexible electronics. We report synthesis, structural, magnetic and RF characterization on PNCs ranging from 20-80 wt-% loadings of Fe 3 O4 and CoFe 2 O4 nanoparticles (~ 8 nm) in a thermosetting resin from the Rogers Corporation. Nanoparticles were synthesized by thermal decomposition and characterized by XRD and TEM. Magnetic properties were studied using a Quantum Design PPMS. PNCs displayed characteristic features of superparamagnetism at room temperature and blocking at low temperature. Microwave transmission/reflection studies were done using a microstrip resonator. Strong tunability in the microwave absorption was observed. We extend our study to include nanoparticle-filled multi-walled carbon nanotubes synthesized by CVD. These high-aspect ratio magnetic nanostructures, with tunable anisotropy, are of particular interest in enhancing magnetic and microwave responses in existing PNCs.

  6. Modeling Percolation in Polymer Nanocomposites by Stochastic Microstructuring

    PubMed Central

    Soto, Matias; Esteva, Milton; Martínez-Romero, Oscar; Baez, Jesús; Elías-Zúñiga, Alex

    2015-01-01

    A methodology was developed for the prediction of the electrical properties of carbon nanotube-polymer nanocomposites via Monte Carlo computational simulations. A two-dimensional microstructure that takes into account waviness, fiber length and diameter distributions is used as a representative volume element. Fiber interactions in the microstructure are identified and then modeled as an equivalent electrical circuit, assuming one-third metallic and two-thirds semiconductor nanotubes. Tunneling paths in the microstructure are also modeled as electrical resistors, and crossing fibers are accounted for by assuming a contact resistance associated with them. The equivalent resistor network is then converted into a set of linear equations using nodal voltage analysis, which is then solved by means of the Gauss–Jordan elimination method. Nodal voltages are obtained for the microstructure, from which the percolation probability, equivalent resistance and conductivity are calculated. Percolation probability curves and electrical conductivity values are compared to those found in the literature. PMID:28793594

  7. Modeling Percolation in Polymer Nanocomposites by Stochastic Microstructuring.

    PubMed

    Soto, Matias; Esteva, Milton; Martínez-Romero, Oscar; Baez, Jesús; Elías-Zúñiga, Alex

    2015-09-30

    A methodology was developed for the prediction of the electrical properties of carbon nanotube-polymer nanocomposites via Monte Carlo computational simulations. A two-dimensional microstructure that takes into account waviness, fiber length and diameter distributions is used as a representative volume element. Fiber interactions in the microstructure are identified and then modeled as an equivalent electrical circuit, assuming one-third metallic and two-thirds semiconductor nanotubes. Tunneling paths in the microstructure are also modeled as electrical resistors, and crossing fibers are accounted for by assuming a contact resistance associated with them. The equivalent resistor network is then converted into a set of linear equations using nodal voltage analysis, which is then solved by means of the Gauss-Jordan elimination method. Nodal voltages are obtained for the microstructure, from which the percolation probability, equivalent resistance and conductivity are calculated. Percolation probability curves and electrical conductivity values are compared to those found in the literature.

  8. Controlled synthesis of transition metal/conducting polymer nanocomposites.

    PubMed

    Liu, Zhen; Liu, Yang; Zhang, Lin; Poyraz, Selcuk; Lu, Ning; Kim, Moon; Smith, James; Wang, Xiaolong; Yu, Yajiao; Zhang, Xinyu

    2012-08-24

    A novel displacement reaction has been observed to occur between conducting polymers (CP) and metal salts which can be used to fabricate nanostructured CP-metal composites in a one-pot manner. Vanadium pentoxide (V(2)O(5)) nanofiber is used during the synthesis as the reactive seeds to induce the nanofibril CP-metal network formation. The CP-metal nanocomposites exhibit excellent sensory properties for hydrogen peroxide (H(2)O(2)) detection, where both high sensitivity and a low detection limit can be obtained. The sensory performance of the CP-metal composite can be further enhanced by a facile microwave treatment. It is believed that the CP-metal nanofibril network can be converted to a carbon-metal network by a microwave-induced carbonization process and result in the sensory enhancement.

  9. Controlled synthesis of transition metal/conducting polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Liu, Zhen; Liu, Yang; Zhang, Lin; Poyraz, Selcuk; Lu, Ning; Kim, Moon; Smith, James; Wang, Xiaolong; Yu, Yajiao; Zhang, Xinyu

    2012-08-01

    A novel displacement reaction has been observed to occur between conducting polymers (CP) and metal salts which can be used to fabricate nanostructured CP-metal composites in a one-pot manner. Vanadium pentoxide (V 2O5) nanofiber is used during the synthesis as the reactive seeds to induce the nanofibril CP-metal network formation. The CP-metal nanocomposites exhibit excellent sensory properties for hydrogen peroxide (H2O2) detection, where both high sensitivity and a low detection limit can be obtained. The sensory performance of the CP-metal composite can be further enhanced by a facile microwave treatment. It is believed that the CP-metal nanofibril network can be converted to a carbon-metal network by a microwave-induced carbonization process and result in the sensory enhancement.

  10. Dielectric breakdown in silica-amorphous polymer nanocomposite films: the role of the polymer matrix.

    PubMed

    Grabowski, Christopher A; Fillery, Scott P; Westing, Nicholas M; Chi, Changzai; Meth, Jeffrey S; Durstock, Michael F; Vaia, Richard A

    2013-06-26

    The ultimate energy storage performance of an electrostatic capacitor is determined by the dielectric characteristics of the material separating its conductive electrodes. Polymers are commonly employed due to their processability and high breakdown strength; however, demands for higher energy storage have encouraged investigations of ceramic-polymer composites. Maintaining dielectric strength, and thus minimizing flaw size and heterogeneities, has focused development toward nanocomposite (NC) films; but results lack consistency, potentially due to variations in polymer purity, nanoparticle surface treatments, nanoparticle size, and film morphology. To experimentally establish the dominant factors in broad structure-performance relationships, we compare the dielectric properties for four high-purity amorphous polymer films (polymethyl methacrylate, polystyrene, polyimide, and poly-4-vinylpyridine) incorporating uniformly dispersed silica colloids (up to 45% v/v). Factors known to contribute to premature breakdown-field exclusion and agglomeration-have been mitigated in this experiment to focus on what impact the polymer and polymer-nanoparticle interactions have on breakdown. Our findings indicate that adding colloidal silica to higher breakdown strength amorphous polymers (polymethyl methacrylate and polyimide) causes a reduction in dielectric strength as compared to the neat polymer. Alternatively, low breakdown strength amorphous polymers (poly-4-vinylpyridine and especially polystyrene) with comparable silica dispersion show similar or even improved breakdown strength for 7.5-15% v/v silica. At ∼15% v/v or greater silica content, all the polymer NC films exhibit breakdown at similar electric fields, implying that at these loadings failure becomes independent of polymer matrix and is dominated by silica.

  11. Multifunctional polymer-metal nanocomposites via direct chemical reduction by conjugated polymers.

    PubMed

    Xu, Ping; Han, Xijiang; Zhang, Bin; Du, Yunchen; Wang, Hsing-Lin

    2014-03-07

    Noble metal nanoparticles (MNPs) have attracted continuous attention due to their promising applications in chemistry, physics, bioscience, medicine and materials science. As an alternative to conventional solution chemistry routes, MNPs can be directly synthesized through a conjugated polymer (CP) mediated technique utilizing the redox chemistry of CPs to chemically reduce the metal ions and modulate the size, morphology, and structure of the MNPs. The as-prepared multifunctional CP-MNP nanocomposites have shown application potentials as highly sensitive surface enhanced Raman spectroscopy (SERS) substrates, effective heterogeneous catalysts for organic synthesis and electrochemistry, and key components for electronic and sensing devices. In this tutorial review, we begin with a brief introduction to the chemical nature and redox properties of CPs that enable the spontaneous reduction of noble metal ions to form MNPs. We then focus on recent progress in control over the size, morphology and structure of MNPs during the conjugated polymer mediated syntheses of CP-MNP nanocomposites. Finally, we highlight the multifunctional CP-MNP nanocomposites toward their applications in sensing, catalysis, and electronic devices.

  12. Preparation and Characterization of Nanocomposite Polymer Membranes Containing Functionalized SnO2 Additives

    PubMed Central

    Scipioni, Roberto; Gazzoli, Delia; Teocoli, Francesca; Palumbo, Oriele; Paolone, Annalisa; Ibris, Neluta; Brutti, Sergio; Navarra, Maria Assunta

    2014-01-01

    In the research of new nanocomposite proton-conducting membranes, SnO2 ceramic powders with surface functionalization have been synthesized and adopted as additives in Nafion-based polymer systems. Different synthetic routes have been explored to obtain suitable, nanometer-sized sulphated tin oxide particles. Structural and morphological characteristics, as well as surface and bulk properties of the obtained oxide powders, have been determined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) and Raman spectroscopies, N2 adsorption, and thermal gravimetric analysis (TGA). In addition, dynamic mechanical analysis (DMA), atomic force microscopy (AFM), thermal investigations, water uptake (WU) measurements, and ionic exchange capacity (IEC) tests have been used as characterization tools for the nanocomposite membranes. The nature of the tin oxide precursor, as well as the synthesis procedure, were found to play an important role in determining the morphology and the particle size distribution of the ceramic powder, this affecting the effective functionalization of the oxides. The incorporation of such particles, having sulphate groups on their surface, altered some peculiar properties of the resulting composite membrane, such as water content, thermo-mechanical, and morphological characteristics. PMID:24957125

  13. Solid state, transparent, cadmium sulfide-polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Kothurkar, Nikhil K.

    This dissertation deals with the preparation and characterization of solid state, transparent CdS-polymer nanocomposites for potential applications in optical limiting, lenses and photovoltaics. The focus of this research was controlling CdS aggregation to obtain 1 mm thick, films with a transmittance >85%. CdS-polysulfone nanocomposites gave transparent sols using thiol-capping agents however solid films obtained, were translucent to opaque. CdS-epoxy nanocomposites gave 1 mm thick films with >85% transmittance. Oligomeric polyoxypropylene diamine stabilizers were used to shield the inter particle forces and increase the viscosity of the medium to give air stable sols. Films were obtained by curing the CdS sols with an epoxy resin system. The band edge of the nanocomposites showed a shoulder corresponding to the absorption from the CdS particles. A majority of small amorphous and non-stoichiometric (richer in Cd) particles <5 nm were observed in TEM micrographs. Relatively fewer CdS aggregates in the range of tens to hundreds of nanometers were also detected. Aggregates were generally more numerous in films as compared to sols. The two-photon absorption coefficient of the CdS particles in the films showed a 30-fold reduction compared to bulk CdS. This was attributed to the lack of crystallinity of particles. The films were stable up to 300°C. CdS aggregation in the CdS-epoxy system depends on a number of factors including temperature, stabilizer concentration, stabilizer molar mass and US concentration. Effective aggregation control yields transparent films. Factors affecting the band edge and transparency of the films were detected and regression models were fitted to the data. Temperature, stabilizer concentration and CdS concentration had significant effects on the band edge and transparency. Interactions between temperature-stabilizer concentration and temperature-CdS concentration had significant effects on the band edge. Band edge tunability with

  14. A Two-Scale FE2 Approach for Simulation of Forming Processes for Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Figiel, Łukasz

    2011-05-01

    A two-scale FE2 computational approach for forming simulations of polymer nanocomposites is presented in this work. The approach connects seamlessly the macroscopic length scale at which the forming process occurs with the length scale, where the nanocomposite morphology is defined. The entire approach is implemented in a commercial Finite Element (FE) software ABAQUS. Plane strain simulations show that the FE2 procedure enables to track the nanocomposite morphology during forming. Hence, the procedure can help to optimize process conditions such as temperature or strain rate, to enhance the nanocomposite morphology and end-use properties.

  15. Development of degradable renewable polymers and stimuli-responsive nanocomposites

    NASA Astrophysics Data System (ADS)

    Eyiler, Ersan

    The overall goal of this research was to explore new living radical polymerization methods and the blending of renewable polymers. Towards this latter goal, polylactic acid (PLA) was blended with a new renewable polymer, poly(trimethylene-malonate) (PTM), with the aim of improving mechanical properties, imparting faster degradation, and examining the relationship between degradation and mechanical properties. Blend films of PLA and PTM with various ratios (5, 10, and 20 wt %) were cast from chloroform. Partially miscible blends exhibited Young's modulus and elongation-to-break values that significantly extend PLA's usefulness. Atomic force microscopy (AFM) data showed that incorporation of 10 wt% PTM into PLA matrix exhibited a Young's modulus of 4.61 GPa, which is significantly higher than that of neat PLA (1.69 GPa). The second part of the bioplastics study involved a one-week hydrolytic degradation study of PTM and another new bioplastic, poly(trimethylene itaconate) (PTI) using DI water (pH 5.4) at room temperature, and the effects of degradation on crystallinity and mechanical properties of these films were examined by differential scanning calorimetry (DSC) and AFM. PTI showed an increase in crystallinity with degradation, which was attributed to predominately degradation of free amorphous regions. Depending on the crystallinity, the elastic modulus increased at first, and decreased slightly. Both bulk and surface-tethered stimuli-responsive polymers were studied on amine functionalized magnetite (Fe3O4) nanoparticles. Stimuli-responsive polymers studied, including poly(N-isopropylacrylamide) (PNIPAM), poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), and poly(itaconic acid) (PIA), were grafted via surface-initiated aqueous atom transfer radical polymerization (SI-ATRP). Both Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS) spectroscopies showed the progression of the grafting. The change in particle size as a

  16. Study on dosimetry characteristics of polymer-CNT nanocomposites: Effect of polymer matrix

    NASA Astrophysics Data System (ADS)

    Malekie, Shahryar; Ziaie, Farhood; Esmaeli, Abdolreza

    2016-04-01

    In this research work, the current density of polymer-carbon nanotube nanocomposite in different weight percentages of nanotubes, over the radiation absorbed dose under a fixed DC voltage for different polymer matrices such as high density polyethylene, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, and polystyrene was investigated via finite element method. The predicted electrical percolation threshold values in different composites were validated by experimental results published by other scientists. The absorbed dose value was considered as multiplying of heat capacity and temperature rise of the composite, regarding the calorimetric approach. Results show that the polymer type having different characteristics of relative permittivity and heat capacity could affect the sensitivity and working dose range of the composite as a dosimeter.

  17. Natural and Synthetic Polymers as Inhibitors of Drug Efflux Pumps

    PubMed Central

    2007-01-01

    Inhibition of efflux pumps is an emerging approach in cancer therapy and drug delivery. Since it has been discovered that polymeric pharmaceutical excipients such as Tweens® or Pluronics® can inhibit efflux pumps, various other polymers have been investigated regarding their potential efflux pump inhibitory activity. Among them are polysaccharides, polyethylene glycols and derivatives, amphiphilic block copolymers, dendrimers and thiolated polymers. In the current review article, natural and synthetic polymers that are capable of inhibiting efflux pumps as well as their application in cancer therapy and drug delivery are discussed. PMID:17896100

  18. Interfacial effects on dielectric properties of polymer-particle nanocomposites

    NASA Astrophysics Data System (ADS)

    Siddabattuni, Sasidhar Veeranjaneyulu

    Dielectric materials that are capable of efficiently storing large amounts of electrical energy are desirable for many electronic and power devices. Since the electrical energy density in a dielectric material is limited to epsilonVb2/2, where is the dielectric permittivity of the material and Vb is the breakdown strength, increased permittivity and breakdown strength are required for large energy storage density. Interfacial effects can influence the dielectric properties, especially dielectric breakdown resistance in polymer-particle nanocomposites. Several functional organophosphates were used to modify the surface of titania and barium titanate nanofiller particles in order to achieve covalent interface when interacted with polymer and to study the influence the electronic nature of filler surfaces on dielectric properties, in particular the breakdown resistance. Surface modified powders were analyzed by thermogravimetric analysis (TGA) and by X-ray photoelectron spectroscopy (XPS). The dielectric composite films obtained by incorporating surface modified powders in epoxy thermosetting polymer were analyzed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), impedance spectroscopy, and dielectric breakdown strength measurements. At 30 vol-% filler concentration, a calculated energy density of ˜8 J/cm3 was observed for titania based composites and ˜8.3 J/cm3 for barium titanate based composites involving electron scavenging interface with minimal dielectric losses compared to pure polymer. Covalent interface composites yielded energy density of ˜7.5 J/cm3 for barium titanate based composites at 30 vol.-%. The data indicate that improved dispersion, breakdown strengths and energy densities resulted when electron-poor functional groups were located at the particle surfaces even compared to covalent interface.

  19. Synthesis and Properties of Polymer Nanocomposites with Tunable Electromagnetic Response

    NASA Astrophysics Data System (ADS)

    Stojak, Kristen L.

    Multifunctional polymer nanocomposites (PNCs) are attractive for the design of tunable RF and microwave components such as flexible electronics, attenuators, and antennas due to cost-effectiveness and durability of polymeric matrices. In this work, three separate PNCs were synthesized. Magnetite (Fe 3O4) and cobalt ferrite (CFO) nanoparticles, synthesized by thermal decomposition, were used as PNC fillers. Polymers used in this work were a commercial polymer provided by the Rogers Corporation (RP) and polyvinylidene fluoride (PVDF). PNCs in this thesis consist of Fe3O 4 in RP, CFO in RP, and Fe3O4 in PVDF. Characterization techniques for determining morphology of the nanoparticles, and their resulting PNCs, include x-ray diffraction, transmission electron microscopy and magnetometry. All magnetometry measurements were taken using a Quantum Design Physical Property Measurement System with a superconducting magnet. Temperature and external magnetic field magnetization measurements revealed that all samples exhibit superparamagnetic behavior at room temperature. Blocking temperature, coercivity and reduced remnant magnetization do not vary with concentration. Tunable saturation magnetization, based on nanoparticle loading, was observed across all PNCs, regardless of polymer or nanoparticle choice, indicating that this is an inherent property in all similar PNC materials. Tunability studies of the magneto-dielectric PNCs were carried out by adding the PNC to cavity and microstrip linear resonator devices, and passing frequencies of 1-6 GHz through them in the presence of transverse external magnetic fields of up to 4.5 kOe, provided by an electromagnet. Microwave characteristics were extracted from scattering parameters of the PNCs. In all cases, losses were reduced, quality factor was increased, and tunability of the resonance frequency was demonstrated. Strong magnetic field dependence was observed across all samples measured in this study.

  20. Using theory and simulation to link molecular features of nanoscale fillers to morphology in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Jayaraman, Arthi; Martin, Tyler

    2014-03-01

    Polymer nanocomposites are a class of materials that consist of a polymer matrix embedded with nanoscale fillers or additives that enhance the inherent properties of the matrix polymer. To engineer polymer nanocomposites for specific applications with target macroscopic properties (e.g. photovoltaics, photonics, automobile parts) it is important to have design rules that relate molecular features to equilibrium morphology of the composite. In the first part of the talk I will present our recent theory and simulation work on composites containing polymer grafted nanoparticles, showing how polydispersity in graft and matrix polymers (physical heterogeneity) can be used to stabilize dispersion of the nanoparticles within a polymer matrix. In the second part of the talk I will present our recent work linking block-copolymer functionalization to the nanoparticle location in a polymer matrix consisting of homopolymer blends.

  1. Synthetic Polymers as Gasoline Thickening Agents

    DTIC Science & Technology

    1944-10-02

    gels Involved the use of asphalts , gums, factices, carbon black, and miscellaneous organic solids. When gels were obtained they were weak and had a...polymer In the F-614 gel gave a very veak, friable gel. Attempts to cross-link Vlstanex In solution vlth di- Isocyanates or vlth sulfur In the... asphalt mixture used as the fluid base of their magnesium pastes was investigated. Only Vlstanex would dissolve in this material. The use of toluene

  2. Osteoblast function on synthetic biodegradable polymers.

    PubMed

    Ishaug, S L; Yaszemski, M J; Bizios, R; Mikos, A G

    1994-12-01

    Rat osteoblasts were cultured on films of biodegradable poly(L-lactic acid) (PLLA), 75:25 poly(DL-lactic-co-glycolic acid) (PLGA), 50:50 PLGA, and poly(glycolic acid) (PGA) for up to 14 days. Osteoblasts attached equally well to all the polymer substrates after 8 h in culture. By day 4 in culture, osteoblasts had exceeded confluency numbers, and their proliferation leveled off by day 7. An increase in alkaline phosphatase (ALP) activity from 1.92 (+/- 0.47) x 10(-7) for day 7 to 5.75 (+/- 0.12) x 10(-7) mumol/cell per min for day 14 was reported for osteoblasts cultured on 75:25 PLGA, which was comparable to that observed for tissue culture polystyrene (TCPS) controls. The ALP activities expressed by osteoblasts cultured on PLLA, 50:50 PLGA, and PGA films did not significantly increase over time. Collagen synthesis for osteoblasts cultured on all polymer substrates was similar to that of TCPS and did not vary with time. The morphology of cultured osteoblasts was not affected by the continuous degradation of the polymer substrates. These results demonstrate that poly(alpha-hydroxy esters) can provide a suitable substrate for osteoblast culture and hold promise in bone regeneration by osteoblast transplantation.

  3. Photoluminescent zinc oxide polymer nanocomposites fabricated using picosecond laser ablation in an organic solvent

    NASA Astrophysics Data System (ADS)

    Wagener, Philipp; Faramarzi, Shamsolzaman; Schwenke, Andreas; Rosenfeld, Rupert; Barcikowski, Stephan

    2011-06-01

    Nanocomposites made of ZnO nanoparticles dispersed in thermoplastic polyurethane were synthesized using picosecond laser ablation of zinc in a polymer-doped solution of tetrahydrofuran. The pre-added polymer stabilizes the ZnO nanoparticles in situ during laser ablation by forming a polymer shell around the nanoparticles. This close-contact polymer shell has a layer thickness up to 30 nm. Analysis of ZnO polyurethane nanocomposites using optical spectroscopy, high resolution transmission electron microscopy and X-ray diffraction revealed that oxidized and crystalline ZnO nanoparticles were produced. Those nanocomposites showed a green photoluminescence emission centred at 538 nm after excitation at 350 nm, which should be attributed to oxygen defects generated during the laser formation mechanism of the monocrystalline nanoparticles. Further, the influence of pulse energy and polymer concentration on the production rate, laser fluence and energy-specific mass productivity was investigated.

  4. Insight into the Broad Field of Polymer Nanocomposites: From Carbon Nanotubes to Clay Nanoplatelets, via Metal Nanoparticles

    PubMed Central

    Stefanescu, Eduard A.; Daranga, Codrin; Stefanescu, Cristina

    2009-01-01

    Highly ordered polymer nanocomposites are complex materials that display a rich morphological behavior owing to variations in composition, structure, and properties on a nanometer length scale. Metal-polymer nanocomposite materials are becoming more popular for applications requiring low cost, high metal surface areas. Catalytic systems seem to be the most prevalent application for a wide range of metals used in polymer nanocomposites, particularly for metals like Pt, Ni, Co, and Au, with known catalytic activities. On the other hand, among the most frequently utilized techniques to prepare polymer/CNT and/or polymer/clay nanocomposites are approaches like melt mixing, solution casting, electrospinning and solid-state shear pulverization. Additionally, some of the current and potential applications of polymer/CNT and/or polymer/clay nanocomposites include photovoltaic devices, optical switches, electromagnetic interference (EMI) shielding, aerospace and automotive materials, packaging, adhesives and coatings. This extensive review covers a broad range of articles, typically from high impact-factor journals, on most of the polymer-nanocomposites known to date: polymer/carbon nanotubes, polymer/metal nanospheres, and polymer/clay nanoplatelets composites. The various types of nanocomposites are described form the preparation stages to performance and applications. Comparisons of the various types of nanocomposites are conducted and conclusions are formulated.

  5. Application of mean-field model of polymer melt intercalation in organo-silicates for nanocomposites.

    PubMed

    Meneghetti, Paulo; Qutubuddin, Syed

    2005-08-15

    The mean-field, lattice-based model of polymer melt intercalation in organically-modified layered silicates (OLS) originally developed by Vaia and Giannelis was applied for different polymers such as poly(methyl methacrylate) (PMMA), polypropylene (PP), and poly(ethylene oxide) (PEO). The nature of each polymer controls significantly the intercalation of the system. The internal energy change caused by the interaction of polymer, surfactant and clay is the strongest factor in determining the equilibrium structure of the nanocomposite system.

  6. Synthetic polymer nanoparticle-polysaccharide interactions: a systematic study.

    PubMed

    Zeng, Zhiyang; Patel, Jiten; Lee, Shih-Hui; McCallum, Monica; Tyagi, Anuradha; Yan, Mingdi; Shea, Kenneth J

    2012-02-08

    The interaction between synthetic polymer nanoparticles (NPs) and biomacromolecules (e.g., proteins, lipids, and polysaccharides) can profoundly influence the NPs fate and function. Polysaccharides (e.g., heparin/heparin sulfate) are a key component of cell surfaces and the extracelluar matrix and play critical roles in many biological processes. We report a systematic investigation of the interaction between synthetic polymer nanoparticles and polysaccharides by ITC, SPR, and an anticoagulant assay to provide guidelines to engineer nanoparticles for biomedical applications. The interaction between acrylamide nanoparticles (~30 nm) and heparin is mainly enthalpy driven with submicromolar affinity. Hydrogen bonding, ionic interactions, and dehydration of polar groups are identified to be key contributions to the affinity. It has been found that high charge density and cross-linking of the NP can contribute to high affinity. The affinity and binding capacity of heparin can be significantly diminished by an increase in salt concentration while only slightly decreased with an increase of temperature. A striking difference in binding thermodynamics has been observed when the main component of a polymer nanoparticle is changed from acrylamide (enthalpy driven) to N-isopropylacryalmide (entropy driven). This change in thermodynamics leads to different responses of these two types of polymer NPs to salt concentration and temperature. Select synthetic polymer nanoparticles have also been shown to inhibit protein-heparin interactions and thus offer the potential for therapeutic applications.

  7. Perspective: NanoMine: A material genome approach for polymer nanocomposites analysis and design

    NASA Astrophysics Data System (ADS)

    Zhao, He; Li, Xiaolin; Zhang, Yichi; Schadler, Linda S.; Chen, Wei; Brinson, L. Catherine

    2016-05-01

    Polymer nanocomposites are a designer class of materials where nanoscale particles, functional chemistry, and polymer resin combine to provide materials with unprecedented combinations of physical properties. In this paper, we introduce NanoMine, a data-driven web-based platform for analysis and design of polymer nanocomposite systems under the material genome concept. This open data resource strives to curate experimental and computational data on nanocomposite processing, structure, and properties, as well as to provide analysis and modeling tools that leverage curated data for material property prediction and design. With a continuously expanding dataset and toolkit, NanoMine encourages community feedback and input to construct a sustainable infrastructure that benefits nanocomposite material research and development.

  8. Do attractive interactions slow down diffusion in polymer nanocomposites?

    NASA Astrophysics Data System (ADS)

    Lin, Chia-Chun; Gam, Sangah; Meth, Jeffrey S.; Clarke, Nigel; Winey, Karen I.; Composto, Russell J.

    2013-03-01

    Diffusion of deuterated poly(methyl methacrylate) (dPMMA) is slowed down in PMMA matrix filled with spherical silica nanoparticles (NPs) ranging from 13 to 50 nm in diameter. NPs are well dispersed in the matrix up to 40 vol%. The normalized diffusion coefficients (D/D0) decrease as the volume fractions increases, and this decrease is stronger as NPs size decreases. When plotted against the confinement parameter, ID/2Rg, where ID is interparticle distance and 2Rg is probe size, D/D0 collapse onto a master curve. In the strongly confined region where ID < 2Rg, D/D0 decrease dramatically up to 80 %, whereas in the weakly confined region where ID > 2Rg, D/D0 decrease moderately. Even when ID is eight times larger than 2Rg, a 15 % reduction in the diffusion is observed. The master curve of this study, an attractive system, compared with a weakly interacting system previously studied, indicating attractive interactions do not significantly alter center of mass polymer diffusion in polymer nanocomposites.

  9. AFM studies of semicrystalline polymer/inorganic nanocomposites

    NASA Astrophysics Data System (ADS)

    Strawhecker, Kenneth E.

    2002-01-01

    vapor transmission properties superior to that of the neat polymer and its conventionally filled composites. For example, for a 5wt.% MMT exfoliated composite, the softening temperature increases by 25°C, the Young's modulus triples with a decrease of only 20% in toughness, whereas there is also a 60% reduction in the water permeability. Furthermore, due to the nanoscale dispersion of filler, the nanocomposites retain their optical clarity. Finally, to better connect changes in morphology with property enhancements, AFM methods were devised which allow direct imaging of morphology as well as local properties.

  10. Recent Advances in Research on the Synthetic Fiber Based Silica Aerogel Nanocomposites

    PubMed Central

    Ślosarczyk, Agnieszka

    2017-01-01

    The presented paper contains a brief review on the synthesis and characterization of silica aerogels and its nanocomposites with nanofibers and fibers based on a literature study over the past twenty years and my own research. Particular attention is focused on carbon fiber-based silica aerogel nanocomposites. Silica aerogel is brittle in nature, therefore, it is necessary to improve this drawback, e.g., by polymer modification or fiber additives. Nevertheless, there are very few articles in the literature devoted to the synthesis of silica aerogel/fiber nanocomposites, especially those focusing on carbon fibers and nanofibers. Carbon fibers are very interesting materials, namely due to their special properties: high conductivity, high mechanical properties in relation to very low bulk densities, high thermal stability, and chemical resistance in the silica aerogel matrix, which can help enhance silica aerogel applications in the future. PMID:28336876

  11. Polymer-mediated tunneling transport between carbon nanotubes in nanocomposites.

    PubMed

    Derosa, Pedro A; Michalak, Tyler

    2014-05-01

    Electron transport in nanocomposites has attracted a good deal of attention for some time now; furthermore, the ability to control its characteristics is a necessary step in the design of multifunctional materials. When conductive nanostructures (for example carbon nanotubes) are inserted in a non-conductive matrix, electron transport below the percolation threshold is dominated by tunneling and thus the conductive characteristics of the composite depends heavily on the characteristics of the tunneling currents between nanoinserts. A parameter-free approach to study tunneling transport between carbon nanotubes across a polymer matrix is presented. The calculation is done with a combination of Density Functional Theory and Green functions (an approach heavily used in molecular electronics) which is shown here to be effective in this non-resonant transport condition. The results show that the method can effectively capture the effect of a dielectric layer in tunneling transport. The current is found to exponentially decrease with the size of the gap for both vacuum and polymer, and that the polymer layer lowers the tunneling barrier enhancing tunneling conduction. For a polyacrylonitrile matrix, a four-fold decrease in the tunneling constant, compared to tunneling in vacuum, is observed, a result that is consistent with available information. The method is very versatile as any DFT functional (or any other quantum mechanics method) can be used and thus the most accurate method for each particular system can be chosen. Furthermore as more methods become available, the calculations can be revised and improved. This approach can be used to design functional materials for fine-tunning the tunneling transport, for instance, the effect of modifying the nanoinsert-matrix interface (for example, by adding functional groups to carbon nanotubes) can be captured and the comparative performance of each interface predicted by simulation.

  12. Transparent infrared-emitting CeF3:Yb-Er polymer nanocomposites for optical applications.

    PubMed

    Tan, Mei Chee; Patil, Swanand D; Riman, Richard E

    2010-07-01

    Bright infrared-emitting nanocomposites of unmodified CeF(3):Yb-Er with polymethyl-methacrylate (PMMA) and polystyrene (PS), which offer a vast range of potential applications, which include optical amplifiers, waveguides, laser materials, and implantable medical devices, were developed. For the optical application of these nanocomposites, it is critical to obtain highly transparent composites to minimize absorption and scattering losses. Preparation of transparent composites typically requires powder processing approaches that include sophisticated particle size control, deagglomeration, and dispersion stabilization methods leading to an increase in process complexity and processing steps. This work seeks to prepare transparent composites with high solids loading (>5 vol%) by matching the refractive index of the inorganic particle with low cost polymers like PMMA and PS, so as to circumvent the use of any complex processing techniques or particle surface modification. PS nanocomposites were found to exhibit better transparency than the PMMA nanocomposites, especially at high solids loading (>/=10 vol%). It was found that the optical transparency of PMMA nanocomposites was more significantly affected by the increase in solids loading and inorganic particle size because of the larger refractive index mismatch of the PMMA nanocomposites compared to that of PS nanocomposites. Rayleigh scattering theory was used to provide a theoretical estimate of the scattering losses in these ceramic-polymer nanocomposites.

  13. Multifunctional Nanotube Polymer Nanocomposites for Aerospace Applications: Adhesion between SWCNT and Polymer Matrix

    NASA Technical Reports Server (NTRS)

    Park, Cheol; Wise, Kristopher E.; Kang, Jin Ho; Kim, Jae-Woo; Sauti, Godfrey; Lowther, Sharon E.; Lillehei, Peter T.; Smith, Michael W.; Siochi, Emilie J.; Harrison, Joycelyn S.; Jordan, Kevin

    2008-01-01

    Multifunctional structural materials can enable a novel design space for advanced aerospace structures. A promising route to multifunctionality is the use of nanotubes possessing the desired combination of properties to enhance the characteristics of structural polymers. Recent nanotube-polymer nanocomposite studies have revealed that these materials have the potential to provide structural integrity as well as sensing and/or actuation capabilities. Judicious selection or modification of the polymer matrix to promote donor acceptor and/or dispersion interactions can improve adhesion at the interface between the nanotubes and the polymer matrix significantly. The effect of nanotube incorporation on the modulus and toughness of the polymer matrix will be presented. Very small loadings of single wall nanotubes in a polyimide matrix yield an effective sensor material that responds to strain, stress, pressure, and temperature. These materials also exhibit significant actuation in response to applied electric fields. The objective of this work is to demonstrate that physical properties of multifunctional material systems can be tailored for specific applications by controlling nanotube treatment (different types of nanotubes), concentration, and degree of alignment.

  14. Polymer/boron nitride nanocomposite materials for superior thermal transport performance.

    PubMed

    Song, Wei-Li; Wang, Ping; Cao, Li; Anderson, Ankoma; Meziani, Mohammed J; Farr, Andrew J; Sun, Ya-Ping

    2012-06-25

    Boron nitride nanosheets were dispersed in polymers to give composite films with excellent thermal transport performances approaching the record values found in polymer/graphene nanocomposites. Similarly high performance at lower BN loadings was achieved by aligning the nanosheets in poly(vinyl alcohol) matrix by simple mechanical stretching (see picture).

  15. [Progress in researches on synthetic antimicrobial macromolecular polymers].

    PubMed

    Wei, Gang; Yang, Lihua; Chu, Liangyin

    2010-08-01

    Broad-spectrum antimicrobial peptides provide a new way to address the urgent growing problem of bacterial resistance. However, the limited natural resources and the high cost of extraction and purification of natural antimicrobial peptides can not meet the requirements of clinical application. In order to solve this problem, researchers have utilized two basic common structural features (amphiphilic and cationic) for designing and preparing synthetic antimicrobial macromolecular polymers. During the last decade, several kinds of amphiphilic polymers, including arylamide oligomers, phenylene ethynylenes, polymethacrylates, polynorbornenes as well as nylon-3 polymers have been synthesized. In this paper, the structures, antibacterial activities and selectivities of these polymers are reviewed, and the effects of molecular size, polarity and ratio of hydrophobic groups, positive charge density on antibacterial activity and selectivity are also summarized.

  16. Slow dynamics of nanocomposite polymer aerogels as revealed by X-ray photocorrelation spectroscopy (XPCS).

    PubMed

    Hernández, Rebeca; Nogales, Aurora; Sprung, Michael; Mijangos, Carmen; Ezquerra, Tiberio A

    2014-01-14

    We report on a novel slow dynamics of polymer xerogels, aerogels, and nanocomposite aerogels with iron oxide nanoparticles, as revealed by X-ray photon correlation spectroscopy. The polymer aerogel and its nanocomposite aerogels, which are porous in nature, exhibit hyper-diffusive dynamics at room temperature. In contrast, non-porous polymer xerogels exhibit an absence of this peculiar dynamics. This slow dynamical process has been assigned to a relaxation of the characteristic porous structure of these materials and not to the presence of nanoparticles.

  17. Slow dynamics of nanocomposite polymer aerogels as revealed by X-ray photocorrelation spectroscopy (XPCS)

    SciTech Connect

    Hernández, Rebeca E-mail: aurora.nogales@csic.es; Mijangos, Carmen; Nogales, Aurora E-mail: aurora.nogales@csic.es; Ezquerra, Tiberio A.; Sprung, Michael

    2014-01-14

    We report on a novel slow dynamics of polymer xerogels, aerogels, and nanocomposite aerogels with iron oxide nanoparticles, as revealed by X-ray photon correlation spectroscopy. The polymer aerogel and its nanocomposite aerogels, which are porous in nature, exhibit hyper-diffusive dynamics at room temperature. In contrast, non-porous polymer xerogels exhibit an absence of this peculiar dynamics. This slow dynamical process has been assigned to a relaxation of the characteristic porous structure of these materials and not to the presence of nanoparticles.

  18. Magnetism and nuclear magnetic resonance of smectite clays and their polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Levin, E. M.; Rawal, A.; Hou, S. S.; Budko, S. L.; Schmidt-Rohr, K.

    2004-03-01

    In an effort to understand the magnetic properties of polymer-clay nanocomposites and improve their nuclear magnetic resonance (NMR) spectroscopy, we have measured the "bulk" magnetization and magnetic susceptibility of three smectite clays (2:1 layered silicates), namely natural montmorillonite (MMT), synthetic mica-montmorillonite (SMMT), and natural hectorite (HCT), and correlated these data with the ^1H and ^29Si NMR signal intensities. As observed before, HCT provides much better NMR spectra than does MMT, even though its low-field magnetic susceptibility is larger than that of MMT. The reason is that the magnetization of HCT at ambient temperature is dominated by a contribution from ferromagnetic-like impurities, while MMT exhibits Langevin paramagnetism. Based on this insight, we have improved the HCT purification procedure, introducing magnetic separation and also avoiding centrifugation which enriches the sample with carbonates. This has increased the NMR signal intensity of HCT 4-fold. The resulting improvement in the quality of ^1H-^29Si NMR spectra of HCT dispersed in a polymer matrix is demonstrated.

  19. Microscopic theory for dynamics in entangled polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Yamamoto, Umi

    New microscopic theories for describing dynamics in polymer nanocomposites are developed and applied. The problem is addressed from two distinct perspectives and using two different theoretical approaches. The first half of this dissertation studies the long-time and intermediate-time dynamics of nanoparticles in entangled and unentangled polymer melts for dilute particle concentrations. Using a combination of mode-coupling, Brownian motion, and polymer physics ideas, the nanoparticle long-time diffusion coefficients is formulated in terms of multiple length-scales, packing microstructures, and spatially-resolved polymer density fluctuation dynamics. The key motional mechanism is described via the parallel relaxation of the force exerted on the particle controlled by collective polymer constraint-release and the particle self-motion. A sharp but smooth crossover from the hydrodynamic to the non-hydrodynamic regime is predicted based on the Stokes-Einstein violation ratio as a function of all the system variables. Quantitative predictions are made for the recovery of the Stokes-Einstein law, and the diffusivity in the crossover regime agrees surprisingly well with large-scale molecular dynamics simulations for all particle sizes and chain lengths studied. The approach is also extended to address intermediate-time anomalous transport of a single nanoparticle and two-particle relative diffusion. The second half of this dissertation focuses on developing a novel dynamical theory for a liquid of infinitely-thin rods in the presence of hard spherical obstacles, aiming at a technical and conceptual extension of the existing paradigm for entangled polymer dynamics. As a fundamental theoretical development, the two-component generalization of a first-principles dynamic meanfield approach is presented. The theory enforces inter-needle topological uncrossability and needlesphere impenetrability in a unified manner, leading to a generalized theory of entanglements that

  20. Effect of Nanoparticle Dispersion on Polymer Matrix and their Fiber Nanocomposites

    NASA Astrophysics Data System (ADS)

    Uddin, Mohammed F.; Sun, Chin-Teh

    Dispersion of nanoparticles and its effect on mechanical properties were investigated by fabricating nanocomposites via conventional sonication, sol-gel, and modified sonication method. Silica nanoparticles dispersed in epoxy and MEK produced via sol-gel method were procured as Nanopox F 400 and MEK-ST-MS, respectively, to produce silica/epoxy nanocomposite whereas the conventional son-ication method was followed to produce alumina/epoxy and carbon nanofibers (CNF)/epoxy nanocomposites. The conventional sonication method was modified by combining it with sol-gel method to improve the dispersion quality as well as to increase the particle loading. The as-prepared nanocomposites were morphologically and mechanically characterized to investigate the effect of dispersion of nanoparticles on polymer matrix nanocomposites. The nanocomposites fabricated via sol-gel method revealed the most improved and consistent properties among all nanocomposites which showed almost proportional properties improvement with particle loading in contrast to conventional nanocomposites. Subsequently, the modified matrix (silica/epoxy) was used to make fiber reinforced nanocomposites via the VARTM process. The effect of improved matrix properties was reflected in the properties of fiber composites which showed significant improvements in compressive strength, tensile strength and modulus, fracture toughness and impact resistance.

  1. MALDI of synthetic polymers with labile end-groups.

    PubMed

    Charles, Laurence

    2014-01-01

    Mass spectrometry is increasingly used in the field of synthetic polymers as a fast and accurate technique for end-group analysis. More particularly, matrix-assisted laser desorption/ionization (MALDI) has gained much popularity because it allows quite simple mass spectra to be obtained, displaying a single distribution for each polymeric species present in the sample, in contrast to electrospray ionization (ESI) which readily promotes multiple charging for most polymers. A soft ionization process, ensuring the integrity of the species upon transfer into gas phase ions, is however mandatory for polymer end-group analysis since information about the chain terminations mainly rely on the m/z values measured for polymer adducts. As compared to ESI, MALDI is sometimes suspected to be a quite "hard" ionization technique, leading to spontaneous dissociation of ionized species either in the source or during their flight time. This issue is of particular concern for polymers carrying so-called fragile end-groups arising from their mode of synthesis. In particular, controlled radical polymerization (CRP) processes, one of the most important advances in the field of polymer science during the last 20 years, allow the production of polymers with well-defined molecular distribution and low polydispersities, but they are all based on the low dissociation energy of the chemical bond between the last monomer and the terminating group. As a result, if macromolecules are activated while being ionized, this end-group is prone to fragmentation and ions measured in the mass spectra do no longer reflect the original chain composition. However, different results are reported in the literature about the ability of MALDI to generate intact ions from CRP synthetic polymers. This article reviews MALDI MS data reported for synthetic polymers produced by atom transfer radical polymerization (ATRP), reversible addition-fragmentation transfer polymerization (RAFT), and nitroxide

  2. Natural and synthetic polymers in fabric and home care applications

    NASA Astrophysics Data System (ADS)

    Paderes, Monissa; Ahirwal, Deepak; Fernández Prieto, Susana

    2017-07-01

    Polymers can be tailored to provide different benefits in Fabric & Home Care formulations depending on the monomers and modifications used, such as avoiding dye transfer inhibition in the wash, modifying the surface of tiles or increasing the viscosity and providing suspension properties to consumer products. Specifically, the rheology modification properties of synthetic and natural polymers are discussed in this chapter. The choice of a polymeric rheology modifier will depend on the formulation ingredients (charges, functional groups), the type and the amount of surfactants, the pH and the desired rheology modification. Natural polymeric rheology modifiers have been traditionally used in the food industry, being xanthan gum one of the most well-known ones. On the contrary, synthetic rheology modifiers are preferably used in paints & coats, textile printing and cleaning products.

  3. Synthetic polymers and their potential as genetic materials.

    PubMed

    Pinheiro, Vitor B; Loakes, David; Holliger, Philipp

    2013-02-01

    DNA and RNA are the only known natural genetic materials. Systematic modification of each of their chemical building blocks (nucleobase, sugar, and phosphate) has enabled the study of the key properties that make those nucleic acids genetic materials. All three moieties contribute to replication and, significantly, all three moieties can be replaced by synthetic analogs without loss of function. Synthetic nucleic acid polymers capable of storing and propagating information not only expand the central dogma, but also highlight that DNA and RNA are not unique chemical solutions for genetic information storage. By considering replication as a question of information transfer, we propose that any polymer that can be replicated could serve as a genetic material. Copyright © 2013 WILEY Periodicals, Inc.

  4. The Use of Clay-Polymer Nanocomposites in Wastewater Pretreatment

    PubMed Central

    Rytwo, Giora

    2012-01-01

    Some agricultural effluents are unsuitable for discharge into standard sewage-treatment plants: their pretreatment is necessary to avoid clogging of the filtering devices by colloidal matter. The colloidal stability of the effluents is mainly due to mutual repulsive forces that keep charged particles in suspension. Pretreatment processes are based on two separate stages: (a) neutralization of the charges (“coagulation”) and (b) bridging between several small particles to form larger aggregates that sink, leaving clarified effluent (“flocculation”). The consequent destabilization of the colloidal suspension lowers total suspended solids (TSSs), turbidity, and other environmental quality parameters, making the treatments that follow more efficient. Clay-based materials have been widely used for effluent pretreatment and pollutant removal. This study presents the use of nanocomposites, comprised of an anchoring particle and a polymer, as “coagoflocculants” for the efficient and rapid reduction of TSS and turbidity in wastewater with a high organic load. The use of such particles combines the advantages of coagulant and flocculant by neutralizing the charge of the suspended particles while bridging between them and anchoring them to a denser particle (the clay mineral), enhancing their precipitation. Very rapid and efficient pretreatment is achieved in one single treatment step. PMID:22454607

  5. Electric Transport Phenomena of Nanocomposite Organic Polymer Thin Films

    NASA Astrophysics Data System (ADS)

    Jira, Nicholas C.; Sabirianov, Ildar; Ilie, Carolina C.

    We discuss herein the nanocomposite organic thin film diodes for the use of plasmonic solar cells. This experimental work follows the theoretical calculations done for plasmonic solar cells using the MNPBEM toolbox for MatLab. These calculations include dispersion curves and amount of light scattering cross sections for different metallic nanoparticles. This study gives us clear ideas on what to expect from different metals, allowing us to make the best choice on what to use to obtain the best results. One specific technique for light trapping in thin films solar cells utilizes metal nanoparticles on the surface of the semiconductor. The characteristics of the metal, semiconductor interface allows for light to be guided in between them causing it to be scattered, allowing for more chances of absorption. The samples were fabricated using organic thin films made from polymers and metallic nanoparticles, more specifically Poly(1-vinylpyrrolidone-co-2-dimethylaminoethyl methacrylate) copolymer and silver or gold nanoparticles. The two fabrication methods applied include spin coating and Langmuir-Blodgett technique. The transport properties are obtained by analyzing the I-V curves. We will also discuss the resistance, resistivity, conductance, density of charge carriers. SUNY Oswego SCAC Grant.

  6. Experimental and Numerical Characterization of Polymer Nanocomposites for Solid Rocket Motor Internal Insulation

    DTIC Science & Technology

    2006-09-30

    a modeling framework for simulating the insulative behavior of thermoplastic Polyurethane elastomer nanocomposites (TPUNs) for solid rocket motors...Nanophase, Thermoplastic Elastomer, EPDM Rubber, Surface Modified MMT Clay, Carbon Nanofibers 16. SECURITY CLASSIFICATION OF: a. REPORT u b. ABSTRACT U...Third Year Program Tasks 7 4. Description of Polymer Nanocomposites 7 4.1 Thermoplastic Elastomer 7 4.2 Montmorilonite Nanoclays 7 4.3 Carbon

  7. In-situ fabrication of polymer/metal nanocomposite films using a mid-infrared laser

    NASA Astrophysics Data System (ADS)

    Nakajima, Takashi

    2017-09-01

    We demonstrate a very rapid in-situ fabrication of polymer/metal nanocomposite films. Using a CO2 laser at 10.6 μm, Ag-PVA (polyvinyl alcohol) nanocomposite films are successfully fabricated on a glass substrate within 10 seconds, which is the most rapid method among any known fabrication methods. The fabricated films are characterized using the optical absorption, atomic force microscopy, and x-ray diffraction measurements.

  8. Extrusion of polysaccharide nanocrystal reinforced polymer nanocomposites through compatibilization with poly(ethylene oxide).

    PubMed

    Pereda, Mariana; El Kissi, Nadia; Dufresne, Alain

    2014-06-25

    Polysaccharide nanocrystals with a rodlike shape but with different dimensions and specific surface area were prepared from cotton and capim dourado cellulose, and with a plateletlike morphology from waxy maize starch granules. The rheological behavior of aqueous solutions of poly(ethylene oxide) (PEO) with different molecular weights when adding these nanoparticles was investigated evidencing specific interactions between PEO chains and nanocrystals. Because PEO also bears hydrophobic moieties, it was employed as a compatibilizing agent for the melt processing of polymer nanocomposites. The freeze-dried mixtures were used to prepare nanocomposite materials with a low density polyethylene matrix by extrusion. The thermal and mechanical behavior of ensuing nanocomposites was studied.

  9. Multi-scale effects on deformation mechanisms of polymer nanocomposites: Experimental characterisation and numerical study

    NASA Astrophysics Data System (ADS)

    Dong, Yu

    In order to make much stiffer, light weight and high performance material products, polymer nanocomposites play an emerging role in the material innovation. Unlike other thermoplastics, polymer nanocomposites are fabricated by introducing a small amount of solid nano-scale fillers (normally less than 5 wt%) such as nanoclay, carbon nanotubes or nanofibres into a plastic resin to dramatically enhance its stiffness, strength and thermal properties. The difference between nanocomposites and conventional fibre composites is that the added fillers are extremely small, only one-millionth of a millimetre thick, and provide a much larger interface area per unit volume for greatly improving the interfacial bonding effect between nanofillers and the polymer matrix. More importantly, polypropylene (PP)/clay nanocomposites have quite a high potential to form such innovative materials and replace the conventional plastics in many automotive and packaging applications. Nevertheless, the growth of PP/clay nanocomposites faces an obstacle of hydrophobic polymer's low interactions with hydrophilic clay. Maleic anhydride (MA) grafted PP (MAPP), commonly used as a compatibiliser, has been proven to facilitate a good clay dispersion within the PP matrix through its functionalised MA groups. But despite the great attention from the manufacturers and researchers in recent years, commercial PP/clay nanocomposites with reliable material properties are still limited in availability. The major problem stems from the complex influences of the material selection and processing methods. The present work developed a comprehensive approach from the material formulation and processing, experimental characterisation to the numerical modelling of PP/clay nanocomposites based on the finite element analysis (FEA) of micro/nanostructures. Initially, effects of the material selection including the clay type and content, MAPP content and PP matrix viscosity were investigated for the mechanical property

  10. Behavior of grafted polymers on nanofillers and their influence on polymer nanocomposite properties

    NASA Astrophysics Data System (ADS)

    Dukes, Douglas Michael

    Polymer nanocomposites continue to receive wide-spread acclaim for their potential to improve composite materials beyond conventional macroscale fillers. The improvement lies both in the altered properties of the particle itself and in the interaction region surrounding the filler. As the surface area of the filler increases, a greater volume fraction of this interphase region is present in the composite. However, simply minimizing the particle size to maximize surface area introduces additional problems; the larger specific surface area promotes aggregation to reduce the surface energy. Since the composite's properties are largely tied to the morphology, aggregation prevents control over the dispersion state of the filler, and thus the properties. Therefore, disaggregation and morphology control are vital to achieving designable nanocomposites. To accomplish both tasks, this thesis focuses on the behavior of grafted polymer coatings on nanoparticles and their in uence on the macroscopic properties. Grafted chains play an integral role in both morphology control and reinforcement. To investigate the behavior of polymer brushes on nanoparticles, polystyrene was grafted on 15 nm silica particles at varying graft densities and molecular weights. Dynamic light scattering studies in dilute solution were performed to obtain the brush height as a function of both graft density and molecular weight. Three distinct regimes of behavior exist, the "mushroom", the semi-dilute polymer brush (SDPB), and the concentrated polymer brush (CPB) regimes. In the CPB regime, which is an extraordinary configuration of highly-stretched chains on densely grafted surfaces, the brush height h was found to scale as h ∝ N4/5, where N is the degree of polymerization. This result is contrary to the observed scaling of the CPB in flat interface systems, where h ∝ N1. To explore the behavior of grafted chains in the melt, molecular dynamics simulations were performed on grafted nanoparticles

  11. Do Membranes Dream of Electric Tubes? Advanced Membranes Using Carbon Nanotube - Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    de Lannoy, Charles-Francois Pedro Claude Karolek Ghislain

    Membrane technologies represent an energy efficient, effective solution for treating municipal and commercial waters/wastewaters. Membranes are predominantly polymer-based and despite steady advances in polymeric materials, they continue to suffer from operational problems including biofouling and breakages. This work addresses these two disparate problems by developing novel CNT-polymer nanocomposite materials that contain variously functionalized carbon nanotubes (fCNTs) in low quantities (<0.5wt%). Several strategies have been employed to achieve highly functional CNT-polymer nanocomposite membranes including blend mixing, ionic charge association, and covalent cross-linking with monomer and oligomer constituents. These CNT-polymer nanocomposite membranes were compared to traditional polymer membranes across various properties including increased Young's Modulus, changes in surface hydrophilicity, fine control over molecular weight cut-off and flux, and surface electrical conductivity. Membranes with high surface electrical conductivity were further tested for their anti-biofouling properties. Finally, CNT stability and polymer compatibility were evaluated throughout membrane manufacture, use, and cleaning. The incorporation of CNTs mixed in bulk phase and linked through ionic associations in polymer matrices showed significant (50%) increases in Young's modulus for certain CNT functionalizations and derivatization percent. Membranes formed with high surface electrical conductivity demonstrated almost complete resistance to biofouling (> 95%) in long-term bacterially challenged experiments. CNTs and polymer mixtures that lacked covalent or ionic bonds were susceptible to significant (up to 10%) loss of CNTs during membrane non-solvent gelation and aggressive chemical cleaning treatment. Functionalized carbon nanotubes endow polymer membranes with their unique strength and electrically conductive properties. These added properties were demonstrated to greatly

  12. Nanoscale Mechanical Characterization of Graphene/Polymer Nanocomposites using Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Cai, Minzhen

    Graphene materials, exhibiting outstanding mechanical properties, are excellent candidates as reinforcement in high-performance polymer nanocomposites. In this dissertation, advanced atomic force microscopy (AFM) techniques are applied to study the nanomechanics of graphene/polymer nanocomposites, specifically the graphene/polymer interfacial strength and the stress transfer at the interface. Two novel methods to directly characterize the interfacial strength between individual graphene sheets and polymers using AFM are presented and applied to a series of polymers and graphene sheets. The interfacial strength of graphene/polymer varies greatly for different combinations. The strongest interaction is found between graphene oxide (GO) and polyvinyl alcohol (PVA), a strongly polar, water-based polymer. On the other hand, polystyrene, a non polar polymer, has the weakest interaction with GO. The interfacial bond strength is attributed to hydrogen bonding and physical adsorption. Further, the stress transfer in GO/PVA nanocomposites is studied quantitatively by monitoring the strain in individual GO sheet inside the polymer via AFM and Raman spectroscopy. For the first time, the strains of individual GO sheets in nanocomposites are imaged and quantified as a function of the applied external strains. The matrix strain is directly transferred to GO sheets for strains up to 8%. At higher strain levels, the onset of the nanocomposite failure and a stick-slip behavior is observed. This study reveals that GO is superior to pure graphene as reinforcement in nanocomposites. These results also imply the potential to make a new generation of nanocomposites with exceptional high strength and toughness. In the second part of this dissertation, AFM is used to study the structure of silk proteins and the morphology of spider silks. For the first time, shear-induced self-assembly of native silk fibroin is observed. The morphology of the Brown Recluse spider silk is investigated and a

  13. Development of Biomedical Polymer-Silicate Nanocomposites: A Materials Science Perspective

    PubMed Central

    Wu, Chia-Jung; Gaharwar, Akhilesh K.; Schexnailder, Patrick J.; Schmidt, Gudrun

    2010-01-01

    Biomedical polymer-silicate nanocomposites have potential to become critically important to the development of biomedical applications, ranging from diagnostic and therapeutic devices, tissue regeneration and drug delivery matrixes to various bio-technologies that are inspired by biology but have only indirect biomedical relation. The fundamental understanding of polymer-nanoparticle interactions is absolutely necessary to control structure-property relationships of materials that need to work within the chemical, physical and biological constraints required by an application. This review summarizes the most recent published strategies to design and develop polymer-silicate nanocomposites (including clay based silicate nanoparticles and bioactive glass nanoparticles) for a variety of biomedical applications. Emerging trends in bio-technological and biomedical nanocomposites are highlighted and potential new fields of applications are examined.

  14. Adsorption and desorption studies of lysozyme by Fe3O4-polymer nanocomposite via fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Koc, Kenan; Alveroglu, Esra

    2015-06-01

    The work have been undertaken in this study is to synthesis and characterize Fe3O4-polymer nanocomposites which are having different morphological properties. Also, investigation of the adsorption and desorption behaviour of lysozyme onto Fe3O4-polymer nanocomposites have been studied. Fe3O4 nanoparticles, synthesized by in situ in polyacrylamide hydrogels, show super-paramagnetic behaviour and saturation magnetization of composite material have been tuned by changing the hydrogel conformation. Adsorption and desorption studies of lysozyme were followed by using pure water at room temperature via fluorescence measurements. Fluorescence measurements showed that, the composite materials adsorbed lysozyme molecules less than 20 s and higher monomer concentration of composite materials cause faster adsorption. Besides, structure of lysozyme molecules were not changed during the adsorption and desorption. As a result Fe3O4-polymer nanocomposites could be used for drug delivery, protein separation and PAAm gels could be used for synthesis of magnetic composites with varying magnetic properties.

  15. Elucidation of structure-to-property relationships of piezoresistive polymer-carbon nanotube nanocomposites

    NASA Astrophysics Data System (ADS)

    Fang, Weiqing; Leung, Siu N.

    2015-07-01

    Polymeric nanocomposites (PNC) filled with carbon nanotubes (CNTs) possess superior multifunctionality, including electrical, thermal, and mechanical properties, making them an emerging family of advanced and multifunctional materials. In recent years, flexible polymer/CNT nanocomposites are increasingly being considered as promising alternatives to conventional smart materials. Their piezoresistive behaviours have led to many potential applications in strain sensing. Despite extensive experimental and theoretical research, the underlying mechanisms for polymer/CNT nanocomposites' piezoresistive behaviours have yet been elucidated. This paper reports comprehensive investigations on the mechanisms and the structure-to-property relationships of these piezoresistive nanocomposites. Quantitative analyses revealed that piezoresistivity of polymer/CNT nanocomposites is predominantly governed by the three mechanisms related to the strain-induced morphological evolution of the CNT network embedded in the polymer matrix. Furthermore, both CNT content and CNT alignment are key structural parameters that affect the contribution of different mechanisms on PNCs' piezoresistivity and the sensitivity of flexible PNCs as strain sensors. For PNC filled with high content of randomly dispersed CNTs, the piezoresistivity was predominantly caused by the breakage of a complex conductive network into two or more simpler conductive paths. For PNC filled with low content of highly aligned CNTs, the piezoresistivity was mainly contributed by the complete disruption of originally interconnected CNTs in electrically conductive pathways.

  16. Relationships between phase morphology and deformation mechanisms in polymer nanocomposite nanofibres prepared by an electrospinning process.

    PubMed

    Kim, G M; Lach, R; Michler, G H; Pötschke, P; Albrecht, K

    2006-02-28

    Relationships between phase morphology and mechanical deformation processes in various electrospun polymer nanocomposite nanofibres (PNCNFs) containing different types of one-, two- and three-dimensional nanofiller have been investigated by transmission electron microscopy using in situ tensile techniques. From the study of the phase structure of electrospun PNCNFs, two morphological standard types are classified for the analysis of deformation mechanisms: the binary system (polymer matrix and nanofillers), and the ternary system (polymer matrix, nanofillers and nanopores on the fibres surface). According to these categories, deformation processes have been characterized, and different schematic models for these processes are proposed. The finding of importance in the present work is a brittle-to-ductile transition in polymer nanocomposite fibres during in situ tensile deformation processes. This unique feature in the deformation behaviour of electrospun PNCNFs provides an optimal balance of stiffness, strength and toughness for use as reinforcing elements in a polymer based composite of a new kind.

  17. Electrochemical characterization of electrospun nanocomposite polymer blend electrolyte fibrous membrane for lithium battery.

    PubMed

    Padmaraj, O; Rao, B Nageswara; Venkateswarlu, M; Satyanarayana, N

    2015-04-23

    Novel hybrid (organic/inorganic) electrospun nanocomposite polymer blend electrolyte fibrous membranes with the composition poly(vinylidene difluoride-co-hexafluoropropylene) [P(VdF-co-HFP)]/poly(methyl methacrylate) [P(MMA)]/magnesium aluminate (MgAl2O4)/LiPF6 were prepared by the electrospinning technique. All of the prepared electrospun P(VdF-co-HFP), PMMA blend [90% P(VdF-co-HFP)/10% PMMA], and nanocomposite polymer blend [90% P(VdF-co-HFP)/10% PMMA/x wt % MgAl2O4 (x = 2, 4, 6, and 8)] fibrous membranes were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy. The fibrous nanocomposite separator-cum-polymer blend electrolyte membranes were obtained by soaking the nanocomposite polymer blend membranes in an electrolyte solution containing 1 M LiPF6 in ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1, v/v). The newly developed fibrous nanocomposite polymer blend electrolyte [90% P(VdF-co-HFP)/10% PMMA/6 wt % MgAl2O4/LiPF6] membrane showed a low crystallinity, low average fiber diameter, high thermal stability, high electrolyte uptake, high conductivity (2.60 × 10(-3) S cm(-1)) at room temperature, and good potential stability above 4.5 V. The best properties of the fibrous nanocomposite polymer blend electrolyte (NCPBE) membrane with a 6 wt % MgAl2O4 filler content was used for the fabrication of a Li/NCPBE/LiCoO2 CR 2032 coin cell. The electrochemical performance of the fabricated CR 2032 cell was evaluated at a current density of 0.1 C-rate. The fabricated CR 2032 cell lithium battery using the newly developed NCPBE membrane delivered an initial discharge capacity of 166 mAh g(-1) and a stable cycle performance.

  18. Chemically Specific Multiscale Modeling of Clay–Polymer Nanocomposites Reveals Intercalation Dynamics, Tactoid Self-Assembly and Emergent Materials Properties

    PubMed Central

    Suter, James L; Groen, Derek; Coveney*, Peter V

    2015-01-01

    A quantitative description is presented of the dynamical process of polymer intercalation into clay tactoids and the ensuing aggregation of polymer-entangled tactoids into larger structures, obtaining various characteristics of these nanocomposites, including clay-layer spacings, out-of-plane clay-sheet bending energies, X-ray diffractograms, and materials properties. This model of clay–polymer interactions is based on a three-level approach, which uses quantum mechanical and atomistic descriptions to derive a coarse-grained yet chemically specific representation that can resolve processes on hitherto inaccessible length and time scales. The approach is applied to study collections of clay mineral tactoids interacting with two synthetic polymers, poly(ethylene glycol) and poly(vinyl alcohol). The controlled behavior of layered materials in a polymer matrix is centrally important for many engineering and manufacturing applications. This approach opens up a route to computing the properties of complex soft materials based on knowledge of their chemical composition, molecular structure, and processing conditions. PMID:25488829

  19. Chemically specific multiscale modeling of clay-polymer nanocomposites reveals intercalation dynamics, tactoid self-assembly and emergent materials properties.

    PubMed

    Suter, James L; Groen, Derek; Coveney, Peter V

    2015-02-01

    A quantitative description is presented of the dynamical process of polymer intercalation into clay tactoids and the ensuing aggregation of polymer-entangled tactoids into larger structures, obtaining various characteristics of these nanocomposites, including clay-layer spacings, out-of-plane clay-sheet bending energies, X-ray diffractograms, and materials properties. This model of clay-polymer interactions is based on a three-level approach, which uses quantum mechanical and atomistic descriptions to derive a coarse-grained yet chemically specific representation that can resolve processes on hitherto inaccessible length and time scales. The approach is applied to study collections of clay mineral tactoids interacting with two synthetic polymers, poly(ethylene glycol) and poly(vinyl alcohol). The controlled behavior of layered materials in a polymer matrix is centrally important for many engineering and manufacturing applications. This approach opens up a route to computing the properties of complex soft materials based on knowledge of their chemical composition, molecular structure, and processing conditions. © 2014 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. On the vibrational characteristics of single-walled boron nitride nanotubes/polymer nanocomposites: A finite element simulation

    NASA Astrophysics Data System (ADS)

    Rouhi, S.; Ansari, R.; Nikkar, A.

    2017-08-01

    The finite element method is used here to investigate the vibrational behavior of single-walled boron nitride nanotube/polymer nanocomposites. The polymer matrix is modeled as a continuous media. Besides, nanotubes are modeled as a space-frame structure. It is shown that increasing the length of nanotubes at a constant volume fraction leads to decreasing of the nanocomposite frequency. By investigating the effect of volume percentage on the frequencies of the boron nitride nanotube-reinforced polymer nanocomposites, it is observed that for short nanotubes, the nanocomposites with larger nanotube volume fractions have larger frequencies. Also, through studying the first 10 frequencies of nanocomposites reinforced by armchair and zigzag nanotubes, it is shown that the effect of chirality on the vibrational behavior of nanocomposite is insignificant.

  1. A biodegradable polymer nanocomposite: Mechanical and barrier properties

    NASA Astrophysics Data System (ADS)

    Lilichenko, N.; Maksimov, R. D.; Zicans, J.; Merijs Meri, R.; Plume, E.

    2008-01-01

    The preparation of an environmentally friendly nanocomposite based on plasticized potato starch and unmodified montmorillonite clay is described. Data on the influence of montmorillonite concentration on the mechanical properties of the materials obtained are reported. The effective elastic constants of the nanocomposites are calculated. The calculation results are compared with experimental data. The influence of montmorillonite content on the moisture permeability is also investigated.

  2. Energy storage in ferroelectric polymer nanocomposites filled with core-shell structured polymer@BaTiO3 nanoparticles: understanding the role of polymer shells in the interfacial regions.

    PubMed

    Zhu, Ming; Huang, Xingyi; Yang, Ke; Zhai, Xing; Zhang, Jun; He, Jinliang; Jiang, Pingkai

    2014-11-26

    The interfacial region plays a critical role in determining the electrical properties and energy storage density of dielectric polymer nanocomposites. However, we still know a little about the effects of electrical properties of the interfacial regions on the electrical properties and energy storage of dielectric polymer nanocomposites. In this work, three types of core-shell structured polymer@BaTiO3 nanoparticles with polymer shells having different electrical properties were used as fillers to prepare ferroelectric polymer nanocomposites. All the polymer@BaTiO3 nanoparticles were prepared by surface-initiated reversible-addition-fragmentation chain transfer (RAFT) polymerization, and the polymer shells were controlled to have the same thickness. The morphology, crystal structure, frequency-dependent dielectric properties, breakdown strength, leakage currents, energy storage capability, and energy storage efficiency of the polymer nanocomposites were investigated. On the other hand, the pure polymers having the same molecular structure as the shells of polymer@BaTiO3 nanoparticles were also prepared by RAFT polymerization, and their electrical properties were provided. Our results show that, to achieve nanocomposites with high discharged energy density, the core-shell nanoparticle filler should simultaneously have high dielectric constant and low electrical conductivity. On the other hand, the breakdown strength of the polymer@BaTiO3-based nanocomposites is highly affected by the electrical properties of the polymer shells. It is believed that the electrical conductivity of the polymer shells should be as low as possible to achieve nanocomposites with high breakdown strength.

  3. 21 CFR 874.3620 - Ear, nose, and throat synthetic polymer material.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ear, nose, and throat synthetic polymer material. 874.3620 Section 874.3620 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN..., and throat synthetic polymer material. (a) Identification. Ear, nose, and throat synthetic...

  4. 21 CFR 874.3620 - Ear, nose, and throat synthetic polymer material.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ear, nose, and throat synthetic polymer material. 874.3620 Section 874.3620 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN..., and throat synthetic polymer material. (a) Identification. Ear, nose, and throat synthetic...

  5. 21 CFR 874.3620 - Ear, nose, and throat synthetic polymer material.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ear, nose, and throat synthetic polymer material. 874.3620 Section 874.3620 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN..., and throat synthetic polymer material. (a) Identification. Ear, nose, and throat synthetic...

  6. 21 CFR 874.3620 - Ear, nose, and throat synthetic polymer material.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Ear, nose, and throat synthetic polymer material. 874.3620 Section 874.3620 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN..., and throat synthetic polymer material. (a) Identification. Ear, nose, and throat synthetic...

  7. 21 CFR 874.3620 - Ear, nose, and throat synthetic polymer material.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Ear, nose, and throat synthetic polymer material. 874.3620 Section 874.3620 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN..., and throat synthetic polymer material. (a) Identification. Ear, nose, and throat synthetic...

  8. Natural and synthetic polymers for wounds and burns dressing.

    PubMed

    Mogoşanu, George Dan; Grumezescu, Alexandru Mihai

    2014-03-25

    In the last years, health care professionals faced with an increasing number of patients suffering from wounds and burns difficult to treat and heal. During the wound healing process, the dressing protects the injury and contributes to the recovery of dermal and epidermal tissues. Because their biocompatibility, biodegradability and similarity to macromolecules recognized by the human body, some natural polymers such as polysaccharides (alginates, chitin, chitosan, heparin, chondroitin), proteoglycans and proteins (collagen, gelatin, fibrin, keratin, silk fibroin, eggshell membrane) are extensively used in wounds and burns management. Obtained by electrospinning technique, some synthetic polymers like biomimetic extracellular matrix micro/nanoscale fibers based on polyglycolic acid, polylactic acid, polyacrylic acid, poly-ɛ-caprolactone, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, exhibit in vivo and in vitro wound healing properties and enhance re-epithelialization. They provide an optimal microenvironment for cell proliferation, migration and differentiation, due to their biocompatibility, biodegradability, peculiar structure and good mechanical properties. Thus, synthetic polymers are used also in regenerative medicine for cartilage, bone, vascular, nerve and ligament repair and restoration. Biocompatible with fibroblasts and keratinocytes, tissue engineered skin is indicated for regeneration and remodeling of human epidermis and wound healing improving the treatment of severe skin defects or partial-thickness burn injuries.

  9. Hybrid lamellar nanocomposites from synthetic organosilane hectorite clay gels.

    SciTech Connect

    Carrado, K. A.; Xu, L.; Muntean, J. V.; Chemistry

    2001-01-01

    A one-step, direct method is described for the creation of synthetic smectite clays grafted with organics on the interlayer surfaces using an organotrialkoxysilane as the silica source. The silane employed most successfully is phenyltriethoxysilane (PTES). Aqueous slurries of LiF, magnesium hydroxide, and the silane are refluxed for 2-5 days, and desirable molar compositions are determined. X-ray powder diffraction, thermal analysis, IR, TEM, N{sub 2} sorption isotherms, and solid-state {sup 13}C and {sup 29}Si NMR techniques are used to characterize the products. The loading of organics on the PTES-hectorites is determined at 20-25% and is comprised of phenyl groups as Si-C linkages. Evidence of this linkage includes an IR peak at 1430 cm{sup -1} and {sup 29}Si NMR assignments at -79 and -66 ppm for RSi(OMg)(OSi){sub 2} and RSi(OMg)(OSi)(OH) species, respectively. The use of tetraethoxysilane (TEOS) resulted in a pure hectorite and comprises the first report of the successful use of a tetraalkoxysilane silicon source for crystallizing hectorite from an aqueous solution.

  10. Colossal Room-Temperature Electrocaloric Effect in Ferroelectric Polymer Nanocomposites Using Nanostructured Barium Strontium Titanates.

    PubMed

    Zhang, Guangzu; Zhang, Xiaoshan; Yang, Tiannan; Li, Qi; Chen, Long-Qing; Jiang, Shenglin; Wang, Qing

    2015-07-28

    The electrocaloric effect (ECE) refers to conversion of thermal to electrical energy of polarizable materials and could form the basis for the next-generation refrigeration and power technologies that are highly efficient and environmentally friendly. Ferroelectric materials such as ceramic and polymer films exhibit large ECEs, but each of these monolithic materials has its own limitations for practical cooling applications. In this work, nanosized barium strontium titanates with systematically varied morphologies have been prepared to form polymer nanocomposites with the ferroelectric polymer matrix. The solution-processed polymer nanocomposites exhibit an extraordinary room-temperature ECE via the synergistic combination of the high breakdown strength of a ferroelectric polymer matrix and the large change of polarization with temperature of ceramic nanofillers. It is found that a sizable ECE can be generated under both modest and high electric fields, and further enhanced greatly by tailoring the morphology of the ferroelectric nanofillers such as increasing the aspect ratio of the nanoinclusions. The effect of the geometry of the nanofillers on the dielectric permittivity, polarization, breakdown strength, ECE and crystallinity of the ferroelectric polymer has been systematically investigated. Simulations based on the phase-field model have been carried out to substantiate the experimental results. With the remarkable cooling energy density and refrigerant capacity, the polymer nanocomposites are promising for solid-state cooling applications.

  11. Preparation of raspberry-like polymer/silica nanocomposite microspheres via emulsifier-free polymerization in water/acetone media.

    PubMed

    Yuhong, Zhang; Qichao, Zou; Xingwang, Shu; Qingqiong, Tang; Min, Chen; Limin, Wu

    2009-08-15

    Raspberry-like polymer/silica nanocomposite microspheres were prepared by emulsifier-free copolymerization of styrene (St) with butyl acrylate (BA) in the presence of 20 nm silica nanoparticles in water/acetone media. A cationic monomer, 2-(methacryloyl)ethyltrimethylammonium chloride (MTC), was used as comonomer and nanosilica particles were adsorbed onto the growing latex core via the electrostatic interaction between negatively charged silica particles and positively charged polymer particles. The average particle sizes and the final silica contents of the nanocomposite microspheres ranged from 200 to 500 nm and 20 to 40 wt%, respectively, depending on the reaction conditions. The solid content of the obtained dispersions could be adjusted between 10 and 25 wt%. The influence of some synthetic parameters, for instance, the ratio of acetone/water, initial silica amount, the mass ratio of the St/BA, MTC, and the APS concentration on the polymerization stability, the average particle size, silica content, and morphology of the composite microspheres, were studied here in detail. It was found that the addition of acetone to the continuous phase resulted in smaller particle sizes and for the lower dielectric medium electrostatic repulsion becomes larger; hence coagulative nucleation is reduced compared to that in aqueous media.

  12. An extended micromechanics method for probing interphase properties in polymer nanocomposites [An extended micromechanics method for overlapping geometries with application to polymer nanocomposites

    SciTech Connect

    Liu, Zeliang; Moore, John A.; Liu, Wing Kam

    2016-05-03

    Inclusions comprised on filler particles and interphase regions commonly form complex morphologies in polymer nanocomposites. Addressing these morphologies as systems of overlapping simple shapes allows for the study of dilute particles, clustered particles, and interacting interphases all in one general modeling framework. To account for the material properties in these overlapping geometries, weighted-mean and additive overlapping conditions are introduced and the corresponding inclusion-wise integral equations are formulated. An extended micromechanics method based on these overlapping conditions for linear elastic and viscoelastic heterogeneous material is then developed. An important feature of the proposed approach is that the effect of both the geometric overlapping (clustered particles) and physical overlapping (interacting interphases) on the effective properties can be distinguished. Lastly, we apply the extended micromechanics method to a viscoelastic polymer nanocomposite with interphase regions, and estimate the properties and thickness of the interphase region based on experimental data for carbon-black filled styrene butadiene rubbers.

  13. An extended micromechanics method for probing interphase properties in polymer nanocomposites [An extended micromechanics method for overlapping geometries with application to polymer nanocomposites

    SciTech Connect

    Liu, Zeliang; Moore, John A.; Liu, Wing Kam

    2016-05-03

    Inclusions comprised on filler particles and interphase regions commonly form complex morphologies in polymer nanocomposites. Addressing these morphologies as systems of overlapping simple shapes allows for the study of dilute particles, clustered particles, and interacting interphases all in one general modeling framework. To account for the material properties in these overlapping geometries, weighted-mean and additive overlapping conditions are introduced and the corresponding inclusion-wise integral equations are formulated. An extended micromechanics method based on these overlapping conditions for linear elastic and viscoelastic heterogeneous material is then developed. An important feature of the proposed approach is that the effect of both the geometric overlapping (clustered particles) and physical overlapping (interacting interphases) on the effective properties can be distinguished. Lastly, we apply the extended micromechanics method to a viscoelastic polymer nanocomposite with interphase regions, and estimate the properties and thickness of the interphase region based on experimental data for carbon-black filled styrene butadiene rubbers.

  14. Polymer nanocomposites with graphene-based hierarchical fillers as materials for multifunctional water treatment membranes.

    PubMed

    Crock, Christopher A; Rogensues, Adam R; Shan, Wenqian; Tarabara, Volodymyr V

    2013-08-01

    Phase inversion of polymer casting mixtures filled with hierarchical functional nanostructures is proposed as a synthetic route for the design of multifunctional membranes. The study tested the hypothesis that by regulating the relative content of components representing different levels in the nanofiller hierarchy, the structure and additional functions of such membranes could be controlled separately. Exfoliated graphite nanoplatelets (xGnPs) decorated by Au nanoparticles (Au NPs), used as a model hierarchical nanofiller, were added to the casting mixture of polysulfone, N-Methyl-2-pyrrolidone and polyethylene glycol prior to forming the membrane by phase inversion. The resulting porous asymmetric nanocomposites were shown to be permselective and catalytically active ultrafiltration membranes that were more resistant to compaction, more permeable than xGnP-free membranes and at least as selective. By designing membrane compositions with different relative amounts of Au-decorated xGnPs and Au-free xGnPs, the structure (controlled by the loading of xGnPs) and catalytic activity (controlled by the loading of Au NPs) could be controlled largely independently. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Direct Creation of Highly Conductive Laser-Induced Graphene Nanocomposites from Polymer Blends.

    PubMed

    Yazdi, Alireza Zehtab; Navas, Ivonne Otero; Abouelmagd, Ahmed; Sundararaj, Uttandaraman

    2017-09-01

    The current state-of-the-art mixing strategies of nanoparticles with insulating polymeric components have only partially utilized the unique electrical conductivity of graphene in nanocomposite systems. Herein, this paper reports a nonmixing method of direct creation of polymer/graphene nanocomposites from polymer blends via laser irradiation. Polycarbonate-laser-induced graphene (PC-LIG) nanocomposite is produced from a PC/polyetherimide (PC/PEI) blend after exposure to commercially available laser scribing with a power of ≈6 W and a speed of ≈2 cm s(-1) . Extremely high electrical conductivities are obtained for the PC-LIG nanocomposites, ranging from 26 to 400 S m(-1) , depending on the vol% of the starting PEI phase in the blend. To the authors' knowledge, these conductivity values are at least one order of magnitude higher than the values that are previously reported for conductive polymer/graphene nanocomposites prepared via mixing strategies. The comprehensive microscopy and spectroscopy characterizations reveal a complete graphitization of the PEI phase with columnar microstructure embedded in the PC phase. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Enhancing the electrical conductivity of a hybrid POSS-PCL/graphene nanocomposite polymer.

    PubMed

    Nezakati, Toktam; Tan, Aaron; Seifalian, Alexander M

    2014-12-01

    An electrically conductive polymer using polyhedral oligomeric silsesquioxane (POSS) nanocage incorporated into a modified poly [caprolactone based urea-urethane] (PCL)/graphene hybrid nanocomposite is described. Multilayer graphene flakes (8nm) were homogeneously dispersed into POSS-PCL at 0.1, 2, 5, and 10wt.% concentrations. This dispersion process of the graphene flakes was achieved by the use of stable dimethylacetamide (DMAc), via solution intercalation with POSS-PCL nanocomposites. The impedance spectroscopy of 5.0wt.% and higher concentration of graphene in POSS-PCL represented major improvement in conductivity over pristine POSS-PCL. The percolation threshold occurred at 5.0wt.% graphene concentration, converting the insulator POSS-PCL into a conductive POSS-PCL/graphene hybrid nanocomposite. The structures of the obtained hybrid materials were characterized with atomic force microscopy (AFM), Fourier transform infra-red (FT-IR), and Raman spectroscopy. The conductivity of the resultant nanocomposite polymer was investigated with electrochemical impedance spectroscopy (EIS). Herein, for the first time, we demonstrate a facile method of synthesizing, and describe the electrical properties of a conductive POSS-PCL/graphene nanocomposite polymer.

  17. Polymer/Silicate Nanocomposites Used to Manufacture Gas Storage Tanks With Reduced Permeability

    NASA Technical Reports Server (NTRS)

    Campbell, Sandi G.; Johnston, Chris

    2004-01-01

    Over the past decade, there has been considerable research in the area of polymer-layered silicate nanocomposites. This research has shown that the dispersion of small amounts of an organically modified layered silicate improves the polymer strength, modulus, thermal stability, and barrier properties. There have been several reports on the dispersion of layered silicates in an epoxy matrix. Potential enhancements to the barrier properties of epoxy/silicate nanocomposites make this material attractive for low permeability tankage. Polymer matrix composites (PMCs) have several advantages for cryogenic storage tanks. They are lightweight, strong, and stiff; therefore, a smaller fraction of a vehicle's potential payload capacity is used for propellant storage. Unfortunately, the resins typically used to make PMC tanks have higher gas permeability than metals. This can lead to hydrogen loss through the body of the tank instead of just at welds and fittings. One approach to eliminate this problem is to build composite tanks with thin metal liners. However, although these tanks provide good permeability performance, they suffer from a substantial mismatch in the coefficient of thermal expansion, which can lead to failure of the bond between the liner and the body of the tank. Both problems could be addressed with polymersilicate nanocomposites, which exhibit reduced hydrogen permeability, making them potential candidates for linerless PMC tanks. Through collaboration with Northrop Grumman and Michigan State University, nanocomposite test tanks were manufactured for the NASA Glenn Research Center, and the helium permeability was measured. An organically modified silicate was prepared at Michigan State University and dispersed in an epoxy matrix (EPON 826/JeffamineD230). The epoxy/silicate nanocomposites contained either 0 or 5 wt% of the organically modified silicate. The tanks were made by filament winding carbon fibers with the nanocomposite resin. Helium permeability

  18. Nanocomposite Edible Films from Mango Puree Reinforced with Cellulose Nanofibers

    USDA-ARS?s Scientific Manuscript database

    Cellulose nanoreinforcements have been used to improve mechanical and barrier properties of biopolymers, whose performance is usually poor when compared to those of synthetic polymers. Nanocomposite edible films have been developed by adding cellulose nanofibers (CNF) in different concentrations (u...

  19. Mechanical-optical-electro modulation by stretching a polymer-metal nanocomposite.

    PubMed

    Minnai, Chloé; Di Vece, Marcel; Milani, Paolo

    2017-09-01

    We report the simultaneous investigation of both the plasmonic resonance and electrical conductance evolution in stretchable metal-polymer nanocomposite films. The films are produced by the implantation of neutral gold nanoparticles in a polydimethylsiloxane substrate by aerodynamic acceleration in a supersonic expansion. A redshift of the gold nanoparticle plasmon peak is found upon stretching as well as a strong correlation between the plasmonic peak wavelength and the nanocomposite electrical resistance. Optical simulations attribute the optical response to the compression of the polymer perpendicular to the stretching direction, which brings the gold particles closer to each other, increasing the plasmonic coupling. Mechanical stretching can induce a simultaneous modulation of the optical and electrical properties of the nanocomposite.

  20. Mechanical-optical-electro modulation by stretching a polymer-metal nanocomposite

    NASA Astrophysics Data System (ADS)

    Minnai, Chloé; Di Vece, Marcel; Milani, Paolo

    2017-09-01

    We report the simultaneous investigation of both the plasmonic resonance and electrical conductance evolution in stretchable metal-polymer nanocomposite films. The films are produced by the implantation of neutral gold nanoparticles in a polydimethylsiloxane substrate by aerodynamic acceleration in a supersonic expansion. A redshift of the gold nanoparticle plasmon peak is found upon stretching as well as a strong correlation between the plasmonic peak wavelength and the nanocomposite electrical resistance. Optical simulations attribute the optical response to the compression of the polymer perpendicular to the stretching direction, which brings the gold particles closer to each other, increasing the plasmonic coupling. Mechanical stretching can induce a simultaneous modulation of the optical and electrical properties of the nanocomposite.

  1. Synthesis of malachite@clay nanocomposite for rapid scavenging of cationic and anionic dyes from synthetic wastewater.

    PubMed

    Srivastava, Varsha; Sillanpää, Mika

    2017-01-01

    Synthesis of malachite@clay nanocomposite was successfully carried out for the removal of cationic (Methylene Blue, MB) and anionic dyes (Congo Red, CR) from synthetic wastewater. Nanocomposite was characterized by TEM, SEM, FT-IR, EDS analysis and zeta potential. TEM analysis indicated that the particle diameter of nanocomposite was in the range of 14 to 23nm. Various important parameters viz. contact time, concentration of dyes, nanocomposite dosage, temperature and solution pH were optimized to achieve maximum adsorption capacity. In the case of MB, removal decreased from 99.82% to 93.67% while for CR, removal decreased from 88.55% to 75.69% on increasing dye concentration from 100 to 450mg/L. pH study confirmed the higher removal of CR in acidic range while MB removal was higher in alkaline range. Kinetic study revealed the applicability of pseudo-second-order model for the adsorption of both dyes. Negative values of ΔG(0) for both systems suggested the feasibility of dye removal and support for spontaneous adsorption of CR and MB on nanocomposite. Nanocomposite showed 277.77 and 238.09mg/g Langmuir adsorption capacity for MB and CR respectively. Desorption of dyes from the dye loaded nanocomposite was easily carried out with acetone. The results indicate that the prepared malachite@clay nanocomposite is an efficient adsorbent with high adsorption capacity for the aforementioned dyes.

  2. Synthesis and characterization of Ag-polymer nanocomposites.

    PubMed

    Mishra, Y K; Mohapatra, S; Chakravadhanula, V S K; Lalla, N P; Zaporojtchenko, V; Avasthi, D K; Faupel, F

    2010-04-01

    We report the synthesis of Ag nanoparticles in polyethylene terephthalate (PET) matrix using atom beam co-sputtering. Metal filling factor was evaluated by Rutherford backscattering spectrometry. Microstructural evolutions of the nanocomposites films were investigated by transmission electron microscopy, which confirmed the formation of irregular shaped Ag nanoparticles. The X-ray photoelectron spectroscopy measurements of the sputter deposited PET film and co-sputtered deposited Ag-PET as well as PET bulk foil (from Goodfellows) were performed to study chemical composition of the nanocomposite films. The optical properties of these nanocomposites were studied by light absorption/transmission, which revealed a narrow transmission of UV light approximately 320 nm and a broad surface plasmon resonance absorption extending up to infrared region (approximately 2400 nm). Swift heavy ion irradiation of Ag-PET nanocomposite resulted in narrowing the full width at half maximum of transmission band.

  3. Conjugated polymer/graphene oxide nanocomposite as thermistor

    NASA Astrophysics Data System (ADS)

    Joshi, Girish M.; Deshmukh, Kalim

    2015-06-01

    We demonstrated the synthesis and measurement of temperature dependent electrical resistivity of graphene oxide (GO) reinforced poly (3, 4 - ethylenedioxythiophene) - tetramethacrylate (PEDOTTMA)/Polymethylmethacrylate (PMMA) based nanocomposites. Negative temperature coefficient (NTC) was observed for 0.5, 1 % GO loading and the positive temperature coefficient (PTC) was observed for 1.5 and 2 % Go loading in the temperature (40 to 120 °C). The GO inducted nanocomposite perform as an excellent thermistor and suitable for electronic and sensor domain.

  4. Conjugated polymer/graphene oxide nanocomposite as thermistor

    SciTech Connect

    Joshi, Girish M. Deshmukh, Kalim

    2015-06-24

    We demonstrated the synthesis and measurement of temperature dependent electrical resistivity of graphene oxide (GO) reinforced poly (3, 4 - ethylenedioxythiophene) - tetramethacrylate (PEDOTTMA)/Polymethylmethacrylate (PMMA) based nanocomposites. Negative temperature coefficient (NTC) was observed for 0.5, 1 % GO loading and the positive temperature coefficient (PTC) was observed for 1.5 and 2 % Go loading in the temperature (40 to 120 °C). The GO inducted nanocomposite perform as an excellent thermistor and suitable for electronic and sensor domain.

  5. Recent progress on preparation and properties of nanocomposites from recycled polymers: A review

    SciTech Connect

    Zare, Yasser

    2013-03-15

    Highlights: ► The article determines the current status of nanotechnology in polymer recycling. ► The addition of nanofillers to waste polymers, composites and blends is discussed. ► The future challenges in polymer recycling using nanoparticles are explained. - Abstract: Currently, the growing consumption of polymer products creates the large quantities of waste materials resulting in public concern in the environment and people life. Nanotechnology is assumed the important technology in the current century. Recently, many researchers have tried to develop this new science for polymer recycling. In this article, the application of different nanofillers in the recycled polymers such as PET, PP, HDPE, PVC, etc. and the attributed composites and blends is studied. The morphological, mechanical, rheological and thermal properties of prepared nanocomposites as well as the future challenges are extensively discussed. The present article determines the current status of nanotechnology in the polymer recycling which guide the future studies in this attractive field.

  6. Effect of Textured Surfactant Brushes on Polymer-Layered Silicate Nanocomposite Morphology

    DTIC Science & Technology

    2004-02-01

    average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data...needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of...Lan, T.; Pinnavaia, T. J. Interfacial Effects on the Reinforcement Properties of Polymer- Organoclay Nanocomposites. Chemistry of Materials 1996, 8

  7. Controlled synthesis of bulk polymer nanocomposites with tunable second order nonlinear optical properties.

    PubMed

    Gu, Jianmin; Yan, Yongli; Zhao, Yong Sheng; Yao, Jiannian

    2012-05-02

    The transparent bulk polymer nanocomposites blended with rare earth nanoparticles are prepared through the radical polymerization of trimethylolpropane trimethylacrylate (TMPTMA). These materials produce continuously tunable second harmonic (SH) radiation under illumination of a wide spectral range of fundamental waves (750-850 nm). The SHG efficiency can be controlled well by altering the Tb(3+) doping content in the nanoparticles.

  8. Development of bimetal oxide doped multifunctional polymer nanocomposite for water treatment

    NASA Astrophysics Data System (ADS)

    Saxena, Swati; Saxena, Umesh

    2016-08-01

    Bimetal oxide doped polymer nanocomposite was developed using Alumina and Iron (III) Oxide as nanoparticles with Nylon 6, 6 and Poly (sodium-4-styrenesulphonate) as polymer matrix for removal of pollutants from water. The blend sample of polymers was prepared by well established solution blending technique and their nanocomposite samples were prepared through dispersion technique during the solution casting of blend sample. The fabricated composites were characterized adopting FTIR, XRD, FESEM and EDX techniques. XRD and FESEM were used for morphological characterization of nano phase, while FTIR and EDX analysis were adopted for characterization of chemical moieties in composites. In the study of pollutant removal capacities of prepared composites, 6 % nanocomposite provided the best results. It exhibited the maximum removal of all parameters. The removal of total alkalinity was 66.67 %, total hardness 42.85 %, calcium 66.67 %, magnesium 25 %, chloride 58.66 %, nitrate 34.78 %, fluoride 63.85 %, TDS 41.27 % and EC was up to the level of 41.37 % by this composite. The study is a step towards developing multifunctional, cost-effective polymer nanocomposites for water remediation applications.

  9. Development of a silver/polymer nanocomposite interconnection layer for organic tandem solar cells

    NASA Astrophysics Data System (ADS)

    Torabi, Naeimeh; Behjat, Abbas; Shahpari, Mahboobeh; Edalati, Shadi

    2015-01-01

    Interconnecting layers (ICL) play an important role in regulating the performance of tandem devices. We report the design of a solution-processed ICL that consists of a silver/polymer nanocomposite deposited on the top of a TiO2 layer. This nanocomposite contains modified poly (3,4-ethylenedioxythiophene) polystyrene sulfonic acid (PEDOT:PSS), and silver nanoparticles (Ag NPs) synthesized by the chemical reduction of silver nitrate in the presence of PEDOT:PSS. Formation of Ag NPs was confirmed by monitoring the plasmon absorption peak characteristics in the UV-visible spectrum of the synthesized nanocomposite. Transmission electron microscopy analysis indicated the presence of spherical silver NPs in a polymer matrix with a mean size of around 20 nm. The sheet resistance of PEDOT:PSS was found to be 2474±35 Ω/sq. It was changed to 445±28 Ω/sq after solvent modification and decreased to 53.31±3.59 Ω/sq after synthesizing silver NPs in the polymer medium. Meanwhile, the transparency of the nanocomposite film deposited on TiO2 was 89.6%, which is considered appropriate for an interconnecting electrode. We demonstrated that by incorporating a silver/polymer nanocomposite as a hole-transporting layer in contact with TiO2 as an electron-transporting layer, the ohmic behavior of ICL is enhanced with respect to pristine PEDOT:PSS. P3HT:PCBM-based tandem solar cells based on this solution-processed intermediate electrode represent significantly increased open-circuit voltage (Voc), reaching close to the sum of the single cells. By incorporating the nanocomposite in the tandem structure, a Voc of 1.1 V was obtained. This value was almost the sum of the Voc of two single cells, which was 1.18 V.

  10. Polymer/Silicate Nanocomposites Developed for Improved Strength and Thermal Stability

    NASA Technical Reports Server (NTRS)

    Campbell, Sandi G.

    2003-01-01

    Over the past decade, polymer-silicate nanocomposites have been attracting considerable attention as a method of enhancing polymer properties. The nanometer dimensions of the dispersed silicate reinforcement can greatly improve the mechanical, thermal, and gas barrier properties of a polymer matrix. In a study at the NASA Glenn Research Center, the dispersion of small amounts (less than 5 wt%) of an organically modified layered silicate (OLS) into the polymer matrix of a carbon-fiber-reinforced composite has improved the thermal stability of the composite. The enhanced barrier properties of the polymer-clay hybrid are believed to slow the diffusion of oxygen into the bulk polymer, thereby slowing oxidative degradation of the polymer. Electron-backscattering images show cracking of a nanocomposite matrix composite in comparison to a neat resin matrix composite. The images show that dispersion of an OLS into the matrix resin reduces polymer oxidation during aging and reduces the amount of cracking in the matrix significantly. Improvements in composite flexural strength, flexural modulus, and interlaminar shear strength were also obtained with the addition of OLS. An increase of up to 15 percent in these mechanical properties was observed in composites tested at room temperature and 288 C. The best properties were seen with low silicate levels, 1 to 3 wt%, because of the better dispersion of the silicate in the polymer matrix.

  11. Controlling Non-Covalent Interactions to Modulate the Dispersion of Fullerenes in Polymer Nanocomposites

    SciTech Connect

    Sumpter, Bobby G

    2011-01-01

    Polymer nanocomposites (PNCs) are materials based on a class of filled plastics that contain relatively small amounts of nanoparticles, which can impart improved structural, mechanical, and thermal properties relative to the neat polymer. However, the homogeneous dispersion of the nanoparticles into a polymer matrix is critical and an impeding factor for the controlled enhancement of PNC properties. In this work, we provide new insight into the importance of polymer chain connectivity and nanoparticle shape and curvature on the formation of noncovalent electron donor-acceptor (EDA) interactions between polymers and nanoparticles. This is accomplished by experimentally monitoring the dispersion of nanoparticles in copolymers containing varying amounts of functional moieties that can form noncovalent interactions with carbon nanoparticles with corroboration through density functional calculations. The results show that the presence of a minority of interacting functional groups within a polymer chain leads to an optimum interaction between the polymer and fullerene. Density functional theory calculations that identify the binding energy and geometry of the interaction between the functional monomers and fullerenes correspond very well with the experimental results. Moreover, comparison of these results to similar studies with single-walled carbon nanotubes (SWNT) indicate a distinct difference in the ability of EDA interactions to improve the dispersion of fullerenes relative to their impact on SWNT. Thus, the polymer chain connectivity, the polymer chain conformation, and size and shape of the nanoparticle modulate the formation of intermolecular interactions and directly impact the dispersion of the resultant nanocomposite.

  12. Dielectric properties of polymer-particle nanocomposites influenced by electronic nature of filler surfaces.

    PubMed

    Siddabattuni, Sasidhar; Schuman, Thomas P; Dogan, Fatih

    2013-03-01

    The interface between the polymer and the particle has a critical role in altering the properties of a composite dielectric. Polymer-ceramic nanocomposites are promising dielectric materials for many electronic and power devices, combining the high dielectric constant of ceramic particles with the high dielectric breakdown strength of a polymer. Self-assembled monolayers of electron rich or electron poor organophosphate coupling groups were applied to affect the filler-polymer interface and investigate the role of this interface on composite behavior. The interface has potential to influence dielectric properties, in particular the leakage and breakdown resistance. The composite films synthesized from the modified filler particles dispersed into an epoxy polymer matrix were analyzed by dielectric spectroscopy, breakdown strength, and leakage current measurements. The data indicate that significant reduction in leakage currents and dielectric losses and improvement in dielectric breakdown strengths resulted when electropositive phenyl, electron-withdrawing functional groups were located at the polymer-particle interface. At a 30 vol % particle concentration, dielectric composite films yielded a maximum energy density of ~8 J·cm(-3) for TiO2-epoxy nanocomposites and ~9.5 J·cm(-3) for BaTiO3-epoxy nanocomposites.

  13. Ferroelectric polymer-based nanocomposites: Towards multiferroic materials

    NASA Astrophysics Data System (ADS)

    Andrew, Jennifer S.

    This dissertation describes new routes towards magnetic-ferroelectric materials, leading to new materials for multiferroic applications. Multiferroic materials exhibit both ferromagnetic and ferroelectric properties, which tend to be mutually exclusive in single-phase materials. Therefore, composite materials are the obvious approach to realizing a material with both a high electric permittivity and high magnetic permeability. In composite systems the magnetoelectric effect arises from a mechanical coupling between a magnetostrictive and a piezoelectric phase. In order to enhance this coupling the interfacial area between the two phases should be maximized. This can be accomplished with nanoparticles, which have a large surface to volume ratio. This work begins with the synthesis of ferrimagnetic (MFe2O 4, M=Ni, Ni0.5Zn0.5, Co) and ferroelectric (BaTiO 3) nanoparticles. Aqueous coprecipitation routes produced superparamagnetic ferrite nanoparticles with an average diameter of 8-10 nanometers. Nanometer sized particles of barium titanate were also produced, but they were cubic and therefore do not exhibit ferroelectric behavior. We then developed routes to form nanoparticle-nanoparticle composites by controlling their stability in solution and therefore their final assembly into magnetic-dielectric nanocomposites. We also developed novel magnetic-ferroelectric composites by filling a ferroelectric polymer with magnetic and dielectric nanoparticles. Polyvinylidene difluoride (PVDF) fibers as well as fibers with continuously dispersed ferrite (Ni0.5Zn0.5Fe2O4) nanoparticles were prepared by electrospinning from dimethyl formamide (DMF) solutions. The effects of the electrospinning processing conditions and nanoparticle loading on the fiber morphology, crystallinity, and the crystalline structure of PVDF were examined. Magnetic and dielectric measurements were also performed. Electrospinning provides a simple technique to form PVDF in the ferroelectric beta

  14. Polyolefin nanocomposites

    DOEpatents

    Chaiko, David J.

    2007-01-02

    The present invention relates to methods for the preparation of clay/polymer nanocomposites. The methods include combining an organophilic clay and a polymer to form a nanocomposite, wherein the organophilic clay and the polymer each have a peak recrystallization temperature, and wherein the organophilic clay peak recrystallization temperature sufficiently matches the polymer peak recrystallization temperature such that the nanocomposite formed has less permeability to a gas than the polymer. Such nanocomposites exhibit 2, 5, 10, or even 100 fold or greater reductions in permeability to, e.g., oxygen, carbon dioxide, or both compared to the polymer. The invention also provides a method of preparing a nanocomposite that includes combining an amorphous organophilic clay and an amorphous polymer, each having a glass transition temperature, wherein the organophilic clay glass transition temperature sufficiently matches the polymer glass transition temperature such that the nanocomposite formed has less permeability to a gas than the polymer.

  15. Interaction of Nano-Sized Materials With Polymer Chains in Polymer-Nanocomposite Thin Films-An AFM Perspective

    NASA Astrophysics Data System (ADS)

    Verma, Gaurav; Kaushik, Anupama; Ghosh, Anup K.

    2011-12-01

    Nanocomposite thin films were prepared with polyurethane as a matrix and organically modified clay as a filler. The interfacial interaction between the exfoliated clay nanoplatelets and the polymeric chains has been investigated by using Atomic Force Microscopy (AFM). The nanoclay platelets show a preferential association with the hard domains of polyurethane matrix on the surface of the thin films. The pendant hydroxyl group on the nanoplatelets attract the isocyanate of the polyisocyanate and a urethane group is formed. This leads to the `clouding' and `entwining' of the nanoplatelets by the hard segmental chains. This is the first visual evidence of nanomaterial filler and polymer matrix interaction and it could open up a spectrum of novel property achievements in nanocomposite thin films. Also the understanding of this interaction can lead to more controlled architecture of nanocomposites.

  16. Recent Progress on Ferroelectric Polymer-Based Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects.

    PubMed

    Prateek; Thakur, Vijay Kumar; Gupta, Raju Kumar

    2016-04-13

    Dielectric polymer nanocomposites are rapidly emerging as novel materials for a number of advanced engineering applications. In this Review, we present a comprehensive review of the use of ferroelectric polymers, especially PVDF and PVDF-based copolymers/blends as potential components in dielectric nanocomposite materials for high energy density capacitor applications. Various parameters like dielectric constant, dielectric loss, breakdown strength, energy density, and flexibility of the polymer nanocomposites have been thoroughly investigated. Fillers with different shapes have been found to cause significant variation in the physical and electrical properties. Generally, one-dimensional and two-dimensional nanofillers with large aspect ratios provide enhanced flexibility versus zero-dimensional fillers. Surface modification of nanomaterials as well as polymers adds flavor to the dielectric properties of the resulting nanocomposites. Nowadays, three-phase nanocomposites with either combination of fillers or polymer matrix help in further improving the dielectric properties as compared to two-phase nanocomposites. Recent research has been focused on altering the dielectric properties of different materials while also maintaining their superior flexibility. Flexible polymer nanocomposites are the best candidates for application in various fields. However, certain challenges still present, which can be solved only by extensive research in this field.

  17. Clay exfoliation in polymer nanocomposites: Specific chemical reactions and exchange of specialty modifications on clay surface

    NASA Astrophysics Data System (ADS)

    Mittal, Vikas

    2010-06-01

    Due the synergistic improvement in properties, which are better than the individual constituents, polymer nanocomposites have been the subject of intensive research. Surface modification of the filler is necessary to enhance its compatibility with the polymer phase and, hence, achieve nanoscale delamination in the polymer matrix. However, conventional alkyl ammonium surface modifications are only suitable for polar polymers and do not lead to exfoliated nanocomposites with non-polar polymers, such as polyolefins. In the absence of any positive interaction between the filler and polyolefin matrices, it is only the higher basal plane spacing of the filler which can lead to its delamination during shearing with the polymer. However, it is not easy to achieve very high basal plane spacing using conventional surface modifications. It requires specific methods or specialty surface modifications, which can lead to a higher amount of organic matter in the clay interlayers and, thus, higher basal plane spacing or reduced forces of attraction. These include synthesis of long chain length surface modifications, chemical reactions with the reactive surface modifications on the filler surface or polymerization reactions on the filler surface to graft polymer chains, etc. In addition, physical adsorption of the polymer chains or other organic molecules on the surface of pre-modified clay can also lead to its uniform organophilization, which again reduces the forces of attraction between the clay platelets.

  18. Light-emitting nanocomposites and novel amorphous polymers for optical applications

    NASA Astrophysics Data System (ADS)

    Gipson, Kyle Garrod

    Polymeric optical materials generally are comprised of amorphous polymers that are transparent in at visible wavelengths but exhibit strong absorption bands in the near-infrared making them less useful for many optical applications. Attenuation, which is the absorption per unit length, largely results from the high vibrational energy associated with carbon-hydrogen bonds contained in the polymer backbone. Attenuation can be mitigated by optical amplification utilizing light emitting additives. Investigated in this dissertation are synthesis techniques for the fabrication of light-emitting polymer nanocomposites and their resultant thermal and rheological characteristics for potential use as polymer optical fibers or films. Inorganic nanocrystals doped with optically active rare-earth ions (Tb 3+:LaF3) treated with organic ligands were synthesized in water and methanol in order to produce polymethyl methacrylate (PMMA) light-emitting nanocomposites. Two different aromatic ligands (acetylsalicylic acid, ASA and 2-picolinic acid, PA) were employed to functionalize the surface of Tb 3+:LaF3 nanocrystals. We have used infrared spectroscopy, thermal analysis, elemental analysis, dynamic light scattering, rheological measurements and optical spectroscopy to investigate the nanoparticle structure and composition response of ligand-capped nanocrystals under various synthesis parameters. A theoretical interpretation of particle-to-particle interactions also was conducted which supported our study of the potential of agglomeration within the nanoparticle suspensions. Novel amorphous polymers (e.g. perfluorocyclobutyl aryl ethers, PFCB), which do not exhibit strong C-H vibrations, have been reported to possess excellent optical properties. Little is known of the intrinsic properties of PFCBs (e.g. biphenylvinyl ether, BPVE and hexafluoroisopropylidene vinyl ether, 6F) as well as the behavior of the polymer melt during extrusion. We preformed empirical and experimental thermal

  19. Transparent, conductive, and superhydrophobic nanocomposite coatings on polymer substrate.

    PubMed

    Yao, Wenhui; Bae, Kwang-Jin; Jung, Myung Yung; Cho, Young-Rae

    2017-11-15

    Transparent, conductive, and superhydrophobic nanocomposite coatings were fabricated on the polyethylene terephthalate substrate by a spray method. Different concentrations of multi-walled carbon nanotubes (MWCNTs) entwined with SiO2 nanoparticles, which originated from the hydrolysis and condensation of tetraethyl orthosilicate, were sprayed to form MWCNTs/SiO2 nanocomposite coatings. The coatings were characterized by scanning electron microscopy, contact angle measurements, and other analytical techniques. The surface morphology, hydrophobicity, transparency, and conductivity of the nanocomposite coating were found to be strongly dependent on the MWCNT concentration. With increasing MWCNT concentration, the hydrophobicity increased first and then decreased, and the optical transmittance and sheet resistance decreased. The enhanced hydrophobicity was associated with the surface microstructure and chemical composition of the coating. The decreased hydrophobicity resulted mainly from the decrease in the trapped air between the water droplet and the nanocomposite coating. Owing to the hierarchically porous 3-dimensional microstructure and opportune fluorinated MWCNT content, the nanocomposite coating with 0.2wt% MWCNTs exhibited the best hydrophobicity with a contact angle of 156.7°, good transparency with 95.7% transmittance and relatively high conductivity with a sheet resistance of 3.2×10(4)Ωsq(-1). Copyright © 2017 Elsevier Inc. All rights reserved.

  20. The Mediterranean Plastic Soup: synthetic polymers in Mediterranean surface waters

    NASA Astrophysics Data System (ADS)

    Suaria, Giuseppe; Avio, Carlo G.; Mineo, Annabella; Lattin, Gwendolyn L.; Magaldi, Marcello G.; Belmonte, Genuario; Moore, Charles J.; Regoli, Francesco; Aliani, Stefano

    2016-11-01

    The Mediterranean Sea has been recently proposed as one of the most impacted regions of the world with regards to microplastics, however the polymeric composition of these floating particles is still largely unknown. Here we present the results of a large-scale survey of neustonic micro- and meso-plastics floating in Mediterranean waters, providing the first extensive characterization of their chemical identity as well as detailed information on their abundance and geographical distribution. All particles >700 μm collected in our samples were identified through FT-IR analysis (n = 4050 particles), shedding for the first time light on the polymeric diversity of this emerging pollutant. Sixteen different classes of synthetic materials were identified. Low-density polymers such as polyethylene and polypropylene were the most abundant compounds, followed by polyamides, plastic-based paints, polyvinyl chloride, polystyrene and polyvinyl alcohol. Less frequent polymers included polyethylene terephthalate, polyisoprene, poly(vinyl stearate), ethylene-vinyl acetate, polyepoxide, paraffin wax and polycaprolactone, a biodegradable polyester reported for the first time floating in off-shore waters. Geographical differences in sample composition were also observed, demonstrating sub-basin scale heterogeneity in plastics distribution and likely reflecting a complex interplay between pollution sources, sinks and residence times of different polymers at sea.

  1. The Mediterranean Plastic Soup: synthetic polymers in Mediterranean surface waters

    PubMed Central

    Suaria, Giuseppe; Avio, Carlo G.; Mineo, Annabella; Lattin, Gwendolyn L.; Magaldi, Marcello G.; Belmonte, Genuario; Moore, Charles J.; Regoli, Francesco; Aliani, Stefano

    2016-01-01

    The Mediterranean Sea has been recently proposed as one of the most impacted regions of the world with regards to microplastics, however the polymeric composition of these floating particles is still largely unknown. Here we present the results of a large-scale survey of neustonic micro- and meso-plastics floating in Mediterranean waters, providing the first extensive characterization of their chemical identity as well as detailed information on their abundance and geographical distribution. All particles >700 μm collected in our samples were identified through FT-IR analysis (n = 4050 particles), shedding for the first time light on the polymeric diversity of this emerging pollutant. Sixteen different classes of synthetic materials were identified. Low-density polymers such as polyethylene and polypropylene were the most abundant compounds, followed by polyamides, plastic-based paints, polyvinyl chloride, polystyrene and polyvinyl alcohol. Less frequent polymers included polyethylene terephthalate, polyisoprene, poly(vinyl stearate), ethylene-vinyl acetate, polyepoxide, paraffin wax and polycaprolactone, a biodegradable polyester reported for the first time floating in off-shore waters. Geographical differences in sample composition were also observed, demonstrating sub-basin scale heterogeneity in plastics distribution and likely reflecting a complex interplay between pollution sources, sinks and residence times of different polymers at sea. PMID:27876837

  2. The Mediterranean Plastic Soup: synthetic polymers in Mediterranean surface waters.

    PubMed

    Suaria, Giuseppe; Avio, Carlo G; Mineo, Annabella; Lattin, Gwendolyn L; Magaldi, Marcello G; Belmonte, Genuario; Moore, Charles J; Regoli, Francesco; Aliani, Stefano

    2016-11-23

    The Mediterranean Sea has been recently proposed as one of the most impacted regions of the world with regards to microplastics, however the polymeric composition of these floating particles is still largely unknown. Here we present the results of a large-scale survey of neustonic micro- and meso-plastics floating in Mediterranean waters, providing the first extensive characterization of their chemical identity as well as detailed information on their abundance and geographical distribution. All particles >700 μm collected in our samples were identified through FT-IR analysis (n = 4050 particles), shedding for the first time light on the polymeric diversity of this emerging pollutant. Sixteen different classes of synthetic materials were identified. Low-density polymers such as polyethylene and polypropylene were the most abundant compounds, followed by polyamides, plastic-based paints, polyvinyl chloride, polystyrene and polyvinyl alcohol. Less frequent polymers included polyethylene terephthalate, polyisoprene, poly(vinyl stearate), ethylene-vinyl acetate, polyepoxide, paraffin wax and polycaprolactone, a biodegradable polyester reported for the first time floating in off-shore waters. Geographical differences in sample composition were also observed, demonstrating sub-basin scale heterogeneity in plastics distribution and likely reflecting a complex interplay between pollution sources, sinks and residence times of different polymers at sea.

  3. Application of parylene for surface (polymer) enhanced laser desorption/ionization of synthetic polymers.

    PubMed

    Miksa, Beata J; Sochacki, Marek; Sroka-Bartnicka, Anna; Uznański, Paweł; Nosal, Andrzej; Potrzebowski, Marek J

    2013-04-15

    Synthetic polymers of molecular masses up to a few kDa can be analyzed without the use of any matrix by direct laser desorption/ionization mass spectrometry (LDI-MS). In this technique, the surface of the sample plate plays a crucial role, and many attempts have been made to understand the influence of the surface on the ease of desorption. Since this technique requires no tedious sample pretreatment, it is a promising method for the rapid characterization of various synthetic polymers. Parylene (poly(p-xylylenes), PPX) was tested as a surface support for studying the molecular masses of biocompatible polymers: poly(ethylene glycol) (PEG), poly(L-lactide) (PLLA), and poly(methyl methacrylate) (PMMA). The average molecular masses of the polymers were: PEG (600.0 Da and 3.5 kDa), PMMA (2.0 kDa), and PLLA (2.8 kDa). LDI mass spectra of polymers deposited on parylene were enhanced by a factor of two over those obtained directly from the gold target plate. Modification of the surface of the target plate by the addition of a PPX layer extended the functionality of LDI-TOF MS, especially for the analysis of low-mass compounds. The LDI analysis using the PPX-coated target plate provided details of polymers including: end-group, composition, monomer unit, and molecular mass distribution. The average molecular weights of four tested polymers on the gold target plate and the PPX support were unchanged, indicating that sample degradation was not occurring despite the high energy of the laser beam. The LDI investigations showed that the PPX support boosted ion yields by a factor of two compared with the gold target plate. Copyright © 2013 John Wiley & Sons, Ltd.

  4. Three-Dimensional Nanoporous Cellulose Gels as a Flexible Reinforcement Matrix for Polymer Nanocomposites.

    PubMed

    Shi, Zhuqun; Huang, Junchao; Liu, Chuanjun; Ding, Beibei; Kuga, Shigenori; Cai, Jie; Zhang, Lina

    2015-10-21

    With the world's focus on utilization of sustainable natural resources, the conversion of wood and plant fibers into cellulose nanowhiskers/nanofibers is essential for application of cellulose in polymer nanocomposites. Here, we present a novel fabrication method of polymer nanocomposites by in-situ polymerization of monomers in three-dimensionally nanoporous cellulose gels (NCG) prepared from aqueous alkali hydroxide/urea solution. The NCG have interconnected nanofibrillar cellulose network structure, resulting in high mechanical strength and size stability. Polymerization of the monomer gave P(MMA/BMA)/NCG, P(MMA/BA)/NCG nanocomposites with a volume fraction of NCG ranging from 15% to 78%. SEM, TEM, and XRD analyses show that the NCG are finely distributed and preserved well in the nanocomposites after polymerization. DMA analysis demonstrates a significant improvement in tensile storage modulus E' above the glass transition temperature; for instance, at 95 °C, E' is increased by over 4 orders of magnitude from 0.03 MPa of the P(MMA/BMA) up to 350 MPa of nanocomposites containing 15% v/v NCG. This reinforcement effect can be explained by the percolation model. The nanocomposites also show remarkable improvement in solvent resistance (swelling ratio of 1.3-2.2 in chloroform, acetone, and toluene), thermal stability (do not melt or decompose up to 300 °C), and low coefficients of thermal expansion (in-plane CTE of 15 ppm·K(-1)). These nanocomposites will have great promising applications in flexible display, packing, biomedical implants, and many others.

  5. Impact of nanoparticle size and shape on selective surface segregation in polymer nanocomposites

    SciTech Connect

    Mutz, M; Holley, Daniel W; Baskaran, Durairaj; Mays, Jimmy; Dadmun, Mark D

    2012-01-01

    A study of the impact of the size and shape of a nanoparticle on the evolution of structure and surface segregation in polymer nanocomposite thin films is presented. This is realized by monitoring the evolution of structure with thermal annealing and equilibrium depth profile of a deuterated polystyrene/ protonated polystyrene bilayer in the presence and absence of various nanoparticles. For the three shapes examined, sheet-like graphene, cylindrical carbon nanotubes, and spherical soft nanoparticles, the presence of the nanoparticles slowed the inter-diffusion of the polymers in the thin film. The larger nanoparticles slowed the polymer motion the most, while the smaller spherical nanoparticles also significantly inhibited polymer chain diffusion. At equilibrium, the soft spherical nanoparticles, which are highly branched, segregate to the air surface, resulting in a decrease in the excess deuterated PS at the surface. The graphene sheets and single walled carbon nanotubes, on the other hand, enhanced the dPS segregation to the air surface. The graphene sheets were found to segregate to the silicon surface, due to their higher surface energy. Interpretation of these results indicates that entropic factors drive the structural development in the nanocomposite thin films containing the spherical nanoparticles, while a balance of the surface energies of the various components (i.e. enthalpy) controls the thin film structure formation in the polymer-carbon nanoparticle nanocomposites.

  6. Development of a stimuli-responsive polymer nanocomposite toward biologically optimized, MEMS-based neural probes

    NASA Astrophysics Data System (ADS)

    Hess, A. E.; Capadona, J. R.; Shanmuganathan, K.; Hsu, L.; Rowan, S. J.; Weder, C.; Tyler, D. J.; Zorman, C. A.

    2011-05-01

    This paper reports the development of micromachining processes and mechanical evaluation of a stimuli-responsive, mechanically dynamic polymer nanocomposite for biomedical microsystems. This nanocomposite consists of a cellulose nanofiber network encased in a polyvinyl acetate matrix. Micromachined tensile testing structures fabricated from the nanocomposite displayed a reversible and switchable stiffness comparable to bulk samples, with a Young's modulus of 3420 MPa when dry, reducing to ~20 MPa when wet, and a stiff-to-flexible transition time of ~300 s. This mechanically dynamic behavior is particularly attractive for the development of adaptive intracortical probes that are sufficiently stiff to insert into the brain without buckling, but become highly compliant upon insertion. Along these lines, a micromachined neural probe incorporating parylene insulating/moisture barrier layers and Ti/Au electrodes was fabricated from the nanocomposite using a fabrication process designed specifically for this chemical- and temperature-sensitive material. It was found that the parylene layers only slightly increased the stiffness of the probe in the wet state in spite of its much higher Young's modulus. Furthermore, the Ti/Au electrodes exhibited impedance comparable to Au electrodes on conventional substrates. Swelling of the nanocomposite was highly anisotropic favoring the thickness dimension by a factor of 8 to 12, leading to excellent adhesion between the nanocomposite and parylene layers and no discernable deformation of the probes when deployed in deionized water.

  7. Thermal and Mechanical Behavior of Hybrid Polymer Nanocomposite Reinforced with Graphene Nanoplatelets

    PubMed Central

    Le, Minh-Tai; Huang, Shyh-Chour

    2015-01-01

    In the present investigation, we successfully fabricate a hybrid polymer nanocomposite containing epoxy/polyester blend resin and graphene nanoplatelets (GNPs) by a novel technique. A high intensity ultrasonicator is used to obtain a homogeneous mixture of epoxy/polyester resin and graphene nanoplatelets. This mixture is then mixed with a hardener using a high-speed mechanical stirrer. The trapped air and reaction volatiles are removed from the mixture using high vacuum. The hot press casting method is used to make the nanocomposite specimens. Tensile tests, dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) are performed on neat, 0.2 wt %, 0.5 wt %, 1 wt %, 1.5 wt % and 2 wt % GNP-reinforced epoxy/polyester blend resin to investigate the reinforcement effect on the thermal and mechanical properties of the nanocomposites. The results of this research indicate that the tensile strength of the novel nanocomposite material increases to 86.8% with the addition of a ratio of graphene nanoplatelets as low as 0.2 wt %. DMA results indicate that the 1 wt % GNP-reinforced epoxy/polyester nanocomposite possesses the highest storage modulus and glass transition temperature (Tg), as compared to neat epoxy/polyester or the other nanocomposite specimens. In addition, TGA results verify thethermal stability of the experimental specimens, regardless of the weight percentage of GNPs. PMID:28793521

  8. The effect of chain rigidity on the interfacial layer thickness and dynamics of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Cheng, Shiwang; Carrillo, Jan-Michael Y.; Carroll, Bobby; Sumpter, Bobby G.; Sokolov, Alexei P.

    There are growing experimental evidences showing the existence of an interfacial layer that has a finite thickness with slowing down dynamics in polymer nanocomposites (PNCs). Moreover, it is believed that the interfacial layer plays a significant role on various macroscopic properties of PNCs. A thicker interfacial layer is found to have more pronounced effect on the macroscopic properties such as the mechanical enhancement. However, it is not clear what molecular parameter controls the interfacial layer thickness. Inspired by our recent computer simulations that showed the chain rigidity correlated well with the interfacial layer thickness, we performed systematic experimental studies on different polymer nanocomposites by varying the chain stiffness. Combining small-angle X-ray scattering, broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry, we find a good correlation between the polymer Kuhn length and the thickness of the interfacial layer, confirming the earlier computer simulations results. Our findings provide a direct guidance for the design of new PNCs with desired properties.

  9. Nanoparticle amount, and not size, determines chain alignment and nonlinear hardening in polymer nanocomposites.

    PubMed

    Varol, H Samet; Meng, Fanlong; Hosseinkhani, Babak; Malm, Christian; Bonn, Daniel; Bonn, Mischa; Zaccone, Alessio; Parekh, Sapun H

    2017-04-04

    Polymer nanocomposites-materials in which a polymer matrix is blended with nanoparticles (or fillers)-strengthen under sufficiently large strains. Such strain hardening is critical to their function, especially for materials that bear large cyclic loads such as car tires or bearing sealants. Although the reinforcement (i.e., the increase in the linear elasticity) by the addition of filler particles is phenomenologically understood, considerably less is known about strain hardening (the nonlinear elasticity). Here, we elucidate the molecular origin of strain hardening using uniaxial tensile loading, microspectroscopy of polymer chain alignment, and theory. The strain-hardening behavior and chain alignment are found to depend on the volume fraction, but not on the size of nanofillers. This contrasts with reinforcement, which depends on both volume fraction and size of nanofillers, potentially allowing linear and nonlinear elasticity of nanocomposites to be tuned independently.

  10. Micropatterning of nanocomposite polymer scaffolds using sacrificial phosphate glass fibers for tendon tissue engineering applications.

    PubMed

    Alshomer, Feras; Chaves, Camilo; Serra, Tiziano; Ahmed, Ifty; Kalaskar, Deepak M

    2017-01-20

    This study presents a simple and reproducible method of micropatterning the novel nanocomposite polymer (POSS-PCU) using a sacrificial phosphate glass fiber template for tendon tissue engineering applications. The diameters of the patterned scaffolds produced were dependent on the diameter of the glass fibers (15 μm) used. Scaffolds were tested for their physical properties and reproducibility using various microscopy techniques. For the first time, we show that POSS-PCU supports growth of human tenocytes cells. Furthermore, we show that cellular alignment, their biological function and expression of various tendon related proteins such as scleraxis, collagen I and III, tenascin-C are significantly elevated on the micropatterned polymer surfaces compared to flat samples. This study demonstrated a simple, reproducible method of micropatterning POSS-PCU nanocomposite polymer for novel tendon repair applications, which when provided with physical cues could help mimic the microenvironment of tenocytes cells.

  11. Synthesis, characterization and optical properties of polymer-based ZnS nanocomposites.

    PubMed

    Tiwari, A; Khan, S A; Kher, R S; Dhoble, S J; Chandel, A L S

    2016-03-01

    Nanostructured polymer-semiconductor hybrid materials such as ZnS-poly(vinyl alcohol) (ZnS-PVA), ZnS-starch and ZnS-hydroxypropylmethyl cellulose (Zns-HPMC) are synthesized by a facile aqueous route. The obtained nanocomposites are characterized using various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV/vis spectroscopy and photoluminescence (PL). XRD studies confirm the zinc blende phase of the nanocomposites and indicate the high purity of the samples. SEM studies indicate small nanoparticles clinging to the surface of a bigger particle. The Energy Dispersive Analysis by X-rays (EDAX) spectrum reveals that the elemental composition of the nanocomposites consists primarily of Zn:S. FTIR studies indicate that the polymer matrix is closely associated with ZnS nanoparticles. The large number of hydroxyl groups in the polymer matrix facilitates the complexation of metal ions. The absorption spectra of the specimens show a blue shift in the absorption edge. The spectrum reveals an absorption edge at 320, 310 and 325 nm, respectively. PL of nanocomposites shows broad peaks in the violet-blue region (420-450 nm). The emission intensity changes with the nature of capping agent. The PL intensity of ZnS-HPMC nanocomposites is found to be highest among the studied nanocomposites. The results clearly indicate that hydroxyl-functionalized HPMC is much more effective at nucleating and stabilizing colloidal ZnS nanoparticles in aqueous suspensions compared with PVA and starch.

  12. Metal-polymer nanocomposites for stretchable optics and plasmonics

    NASA Astrophysics Data System (ADS)

    Potenza, Marco A. C.; Minnai, Chloé; Milani, Paolo

    2016-12-01

    Stretchable and conformable optical devices open very exciting perspectives for the fabrication of systems incorporating diffracting and optical power in a single element and of tunable plasmonic filters and absorbers. The use of nanocomposites obtained by inserting metallic nanoparticles produced in the gas phase into polymeric matrices allows to effectively fabricate cheap and simple stretchable optical elements able to withstand thousands of deformations and stretching cycles without any degradation of their optical properties. The nanocomposite-based reflective optical devices show excellent performances and stability compared to similar devices fabricated with standard techniques. The nanocomposite-based devices can be therefore applied to arbitrary curved non-optical grade surfaces in order to achieve optical power and to minimize aberrations like astigmatism. Examples discussed here include stretchable reflecting gratings, plasmonic filters tunable by mechanical stretching and light absorbers.

  13. Formulation of Fe3O4/acrylate co-polymer nanocomposites as potential drug carriers.

    PubMed

    Phanapavudhikul, Ponpan; Shen, Shoucang; Ng, Wai Kiong; Tan, Reginald B H

    2008-01-01

    Magnetic nanocomposite particles were synthesized by encapsulating nanosized magnetite with an acrylate-based cationic co-polymer made of MMA, BA, and QMA and modifying with MeOPEGMA using the water replacement method. The composition of the co-polymer formulation was optimized based on zeta-potential measurements and freeze-thaw stability. Electrostatic interaction between negatively charged model drug aspirin and positively charged co-polymer plays the most important role in drug loading and in vitro release studies. Drug release exhibited a biphasic profile with an initial burst release followed by a prolonged slow release, which could be potentially useful for target and controlled drug delivery.

  14. Nanocomposite polymer electrolyte based on Poly(ethylene oxide) and solid super acid for lithium polymer battery

    NASA Astrophysics Data System (ADS)

    Xi, Jingyu; Tang, Xiaozhen

    2004-07-01

    This Letter reports a novel PEO-based nanocomposite polymer electrolyte by using solid super acid SO 42-/ZrO 2 as filler. XRD, DSC, and FT-IR results prove the strong Lewis acid-base interactions between SO 42-/ZrO 2 and PEO chains. The addition of SO 42-/ZrO 2 can enhance the ionic conductivity and the lithium ion transference number of the electrolyte. The highest room temperature ionic conductivity of 2.1 × 10 -5 S cm -1 is obtained for the sample PEO 12-LiClO 4-7%SO 42-/ZrO 2. The excellent performances such as good compatibility with lithium electrode, and broad electrochemical stability window suggest that PEO-LiClO 4-SO 42-/ZrO 2 nanocomposite electrolyte can be used as electrolyte materials for lithium polymer batteries.

  15. Prediction of elastic properties for polymer-particle nanocomposites exhibiting an interphase.

    PubMed

    Deng, Fei; Van Vliet, Krystyn J

    2011-04-22

    Particle-polymer nanocomposites often exhibit mechanical properties described poorly by micromechanical models that include only the particle and matrix phases. Existence of an interfacial region between the particle and matrix, or interphase, has been posited and indirectly demonstrated to account for this effect. Here, we present a straightforward analytical approach to estimate effective elastic properties of composites comprising particles encapsulated by an interphase of finite thickness and distinct elastic properties. This explicit solution can treat nanocomposites that comprise either physically isolated nanoparticles or agglomerates of such nanoparticles; the same framework can also treat physically isolated nanoparticle aggregates or agglomerates of such aggregates. We find that the predicted elastic moduli agree with experiments for three types of particle-polymer nanocomposites, and that the predicted interphase thickness and stiffness of carbon black-rubber nanocomposites are consistent with measured values. Finally, we discuss the relative influence of the particle-polymer interphase thickness and stiffness to identify maximum possible changes in the macroscale elastic properties of such materials.

  16. Ferritin nanocontainers that self-direct in synthetic polymer systems

    NASA Astrophysics Data System (ADS)

    Sengonul, Merih C.

    Currently, there are many approaches to introduce functionality into synthetic polymers. Among these, for example, are copolymerization, grafting, and blending methods. However, modifications made by such methods also change the thermodynamics and rheological properties of the polymer system of interest, and each new modification often requires a costly reoptimization of polymer processing. Such a reoptimalization would not be necessary if new functionality could be introduced via a container whose external surface is chemically and physically tuned to interact with the parent polymer. The contents of the container could then be changed without changing other important properties of the parent polymer. In this context this thesis project explores an innovative nanocontainer platform which can be introduced into phase-separating homopolymer blends. Ferritin is a naturally existing nanocontainer that can be used synthetically to package and selectively transport functional moieties to a particular phase that is either in the bulk or on the surface of a homopolymer blend system. The principal focus of this work centers on modifying the surface of wild ferritin to: (1) render modified ferritin soluble in a non-aqueous solvent; and (2) impart it with self-directing properties when exposed to a homopolymer blend surface or incorporated into the bulk of a homopolymer blend. Wild ferritin is water soluble, and this research project successfully modified wild ferritin by grafting either amine-functional poly(ethylene glycol) (PEG) or short-chain alkanes to carbodiimide activated carboxylate groups on ferritin's surface. Such modified ferritin is soluble in dichloromethane (DCM). Modification was confirmed by ion-exchange chromatography, zeta-potential measurements, and electrospray mass spectroscopy. FT-IR was used to quantify the extent of PEGylation of the reaction products through area ratios of the -C-O-C asymmetric stretching vibration of the grafted PEG chains to the

  17. Polymer nanocomposites with enhanced thermal and mechanical properties

    NASA Astrophysics Data System (ADS)

    Si, Mayu

    Flame-retardant Elvacite acrylic resin/Cloisite 6A nanocomposites were prepared via direct melt intercalation. Transmission electron microscopy (TEM) micrographs showed that the high degree of exfoliation occurred, which resulted in a large improvement in thermal stability and UV absorption properties without sacrificing optical clarity. Cone calorimetry tests clearly showed that the heat release rate was far lower and more gradual in the nanocomposites than in pure resins. Additionally, Fourier transform infrared (FTIR) spectroscopy results indicated that the introduction of clay did not change the chemical structure of acrylic resins.

  18. Polymer Nanocomposites Made with Unmodified Graphite or Carbon Nanotubes: Role of Dispersion in Optimizing Mechanical and Thermal Properties and Electrical Conductivity

    NASA Astrophysics Data System (ADS)

    Masuda, Junichi; Wakabayashi, Katsuyuki; Brunner, Philip; Pierre, Cynthia; Torkelson, John

    2009-03-01

    Polymer nanocomposites made with carbon-based nanofiller have the potential to achieve unprecedented, multifunctional property enhancements in comparison with other nanocomposite systems. Here, we describe research in which we prepare nanocomposites with polymers that are not amenable to solution-based processing, such as polypropylene and poly(ethylene terephthalate). Solid-state shear pulverization is used singly or in conjunction with melt processing to obtain well-dispersed polymer/graphite and polymer/carbon nanotube nanocomposites. We report record improvements in properties of unoriented films of polypropylene nanocomposites, including Young's modulus, crystallization rate, and thermal degradation temperature. We also characterize electrical conductivity of such nanocomposites and note that the dispersion characteristics necessary to achieve maximum mechanical and thermal properties differ from those needed to maximize electrical conductivity. The potential of and challenges with using unmodified graphite as a filler in polymer nanocomposites will be discussed.

  19. Luminescent nanocomposites of conducting polymers and in-situ grown CdS quantum dots

    SciTech Connect

    Borriello, C.; Masala, S.; Nenna, G.; Minarini, C.; Di Luccio, T.; Bizzarro, V.; Re, M.; Pesce, E.

    2010-06-02

    Luminescent PVK:CdS and P3HT:CdS nanocomposites with enhanced electrooptical properties have been synthesized. The nucleation and growth of CdS nanoparticles have been obtained by the thermolysis of a single Cd and S precursor dispersed in the polymers. The size distribution and morphology of the nanoparticles have been studied by TEM analyses. Monodispersive and very small nanoparticles of diameter below 3 nm in PVK and 2 nm in P3HT, have been obtained. The application of such nanocomposites as emitting layers in OLED devices is discussed.

  20. Optimal nanomaterial concentration: harnessing percolation theory to enhance polymer nanocomposite performance

    NASA Astrophysics Data System (ADS)

    Nadiv, Roey; Shtein, Michael; Shachar, Gal; Varenik, Maxim; Regev, Oren

    2017-07-01

    A major challenge in nanocomposite research is to predict the optimal nanomaterial concentration (ONC) yielding a maximal reinforcement in a given property. We present a simple approach to identify the ONC based on our finding that it is typically located in close proximity to an abrupt increase in polymer matrix viscosity, termed the rheological percolation threshold, and thus may be used as an indicator of the ONC. This premise was validated by rheological and fractography studies of composites loaded by nanomaterials including graphene nanoribbons or carbon or tungsten disulfide nanotubes. The correlation between in situ viscosity, the rheological percolation threshold concentration and the nanocomposite fractography demonstrates the utility of the method.

  1. Acoustic properties of alumina colloidal/polymer nano-composite film on silicon.

    PubMed

    Zhang, Rui; Cao, Wenwu; Zhou, Qifa; Cha, Jung Hyui; Shung, K Kirk; Huang, Yuhong

    2007-03-01

    Alumina colloidal/polymer composite films on silicon substrates have been successfully fabricated using the sol-gel method, in which the crystallite sizes of alumina are between 20 and 50 nm. The density and ultrasonic phase velocities in these films with different alumina ratios from 14% to 32% were measured at the desired operating frequency. We have proved that the density, acoustic phase velocities, and hence the acoustic impedance of the nano-composite films increase with the alumina content, which gives us another option of tailoring the acoustic impedance of the nano-composite film for making the matching layer of high-frequency medical ultrasonic transducers.

  2. Phase transition of conducting polymer/clay nanocomposite suspensions under an electric field

    NASA Astrophysics Data System (ADS)

    Fang, Fei Fei; Choi, Hyoung Jin; Choi, Woon Seop

    2010-06-01

    Nanocomposites of conducting polyaniline and poly(o-ethoxyaniline) with clay were synthesized via emulsion polymerization and solvent intercalation, respectively, and then applied for electrorheological (ER) materials under an applied electric field. The morphology and intercalated nanostructures were analyzed via TEM images and XRD spectra. The ER performances of synthesized conducting polymer/clay nanocomposites-based ER fluids dispersed in silicone oil were investigated, exhibiting both electric field-dependent shear stress and yield stress. A suggested Cho-Choi-Jhon model was further employed to describe the shear stress curves.

  3. Novel kojic acid-polymer-based magnetic nanocomposites for medical applications

    PubMed Central

    Hussein-Al-Ali, Samer Hasan; Zowalaty, Mohamed Ezzat El; Hussein, Mohd Zobir; Ismail, Maznah; Dorniani, Dena; Webster, Thomas J

    2014-01-01

    Iron oxide magnetic nanoparticles (MNPs) were synthesized by the coprecipitation of iron salts in sodium hydroxide followed by coating separately with chitosan (CS) and polyethylene glycol (PEG) to form CS-MNPs and PEG-MNPs nanoparticles, respectively. They were then loaded with kojic acid (KA), a pharmacologically bioactive natural compound, to form KA-CS-MNPs and KA-PEG-MNPs nanocomposites, respectively. The MNPs and their nanocomposites were characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, vibrating sample magnetometry, and scanning electron microscopy. The powder X-ray diffraction data suggest that all formulations consisted of highly crystalline, pure magnetite Fe3O4. The Fourier transform infrared spectroscopy and thermogravimetric analysis confirmed the presence of both polymers and KA in the nanocomposites. Magnetization curves showed that both nanocomposites (KA-CS-MNPs and KA-PEG-MNPs) were superparamagnetic with saturation magnetizations of 8.1 emu/g and 26.4 emu/g, respectively. The KA drug loading was estimated using ultraviolet–visible spectroscopy, which gave a loading of 12.2% and 8.3% for the KA-CS-MNPs and KA-PEG-MNPs nanocomposites, respectively. The release profile of the KA from the nanocomposites followed a pseudo second-order kinetic model. The agar diffusion test was performed to evaluate the antimicrobial activity for both KA-CS-MNPs and KA-PEG-MNPs nanocomposites against a number of microorganisms using two Gram-positive (methicillin-resistant Staphylococcus aureus and Bacillus subtilis) and one Gram-negative (Salmonella enterica) species, and showed some antibacterial activity, which could be enhanced in future studies by optimizing drug loading. This study provided evidence for the promise for the further investigation of the possible beneficial biological activities of KA and both KA-CS-MNPs and KA-PEG-MNPs nanocomposites in nanopharmaceutical applications. PMID

  4. Polymer-metal nanocomposite thin films: In situ fabrication and applications

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, T. P.

    2012-06-01

    Polymer - metal nanocomposites are versatile materials which combine the unique characteristics of the components as well as manifest mutualistic effects. In situ generation of the nanoparticles inside a solid polymer film is a convenient and attractive route to the fabrication of metal nanoparticle - embedded polymer thin films. This presentation will provide an overview of the methodology involved in a simple protocol that we have developed for the fabrication of noble metal nanostructures inside polymer thin films, using aqueous medium for the synthesis and deploying the polymer itself as the reducing as well as stabilizing agent. The in situ growth of metal nanoparticles inside polymer films provides a unique opportunity to generate novel nanomaterials as well as to monitor the growth process in real time. A variety of techniques that have been exploited to characterize the precursor to product transformation inside the polymer film will be reviewed. The control provided by the in situ fabrication route on the size, shape and distribution of the nanostructures, and application of the nanocomposite thin films in a wide range of areas including nonlinear optics, catalysis, sensing and biology, illustrate the versatility of these materials.

  5. Polymer-Based Nanocomposites: An Internship Program for Deaf and Hard of Hearing Students

    NASA Astrophysics Data System (ADS)

    Cebe, Peggy; Cherdack, Daniel; Seyhan Ince-Gunduz, B.; Guertin, Robert; Haas, Terry; Valluzzi, Regina

    2007-03-01

    We report on our summer internship program in Polymer-Based Nanocomposites, for deaf and hard of hearing undergraduates who engage in classroom and laboratory research work in polymer physics. The unique attributes of this program are its emphasis on: 1. Teamwork; 2. Performance of a start-to-finish research project; 3. Physics of materials approach; and 4. Diversity. Students of all disability levels have participated in this program, including students who neither hear nor voice. The classroom and laboratory components address the materials chemistry and physics of polymer-based nanocomposites, crystallization and melting of polymers, the interaction of X-rays and light with polymers, mechanical properties of polymers, and the connection between thermal processing, structure, and ultimate properties of polymers. A set of Best Practices is developed for accommodating deaf and hard of hearing students into the laboratory setting. The goal is to bring deaf and hard of hearing students into the larger scientific community as professionals, by providing positive scientific experiences at a formative time in their educational lives.

  6. An Internship Program for Deaf and Hard of Hearing Students in Polymer-Based Nanocomposites

    SciTech Connect

    Cebe,P.; Cherdack, D.; Guertin, R.; Haas, T.; S. Ince, B.; Valluzzi, R.

    2006-01-01

    We report on our summer internship program in Polymer-Based Nanocomposites, for deaf and hard of hearing undergraduates who engage in classroom and laboratory research work in polymer physics. The unique attributes of this program are its emphasis on: 1. Teamwork; 2. Performance of a start-to-finish research project; 3. Physics of materials approach; and 4. Diversity. Students of all disability levels have participated in this program, including students who neither hear nor voice. The classroom and laboratory components address the materials chemistry and physics of polymer-based nanocomposites, crystallization and melting of polymers, the interaction of X-rays and light with polymers, mechanical properties of polymers, and the connection between thermal processing, structure, and ultimate properties of polymers. A set of Best Practices is developed for accommodating deaf and hard of hearing students into the laboratory setting. The goal is to bring deaf and hard of hearing students into the larger scientific community as professionals, by providing positive scientific experiences at a formative time in their educational lives.

  7. Synthetic Oral Mucin Mimic from Polymer Micelle Networks

    PubMed Central

    2015-01-01

    Mucin networks are formed in the oral cavity by complexation of glycoproteins with other salivary proteins, yielding a hydrated lubricating barrier. The function of these networks is linked to their structural, chemical, and mechanical properties. Yet, as these properties are interdependent, it is difficult to tease out their relative importance. Here, we demonstrate the ability to recreate the fibrous like network through a series of complementary rinses of polymeric worm-like micelles, resulting in a 3-dimensional (3D) porous network that can be deposited layer-by-layer onto any surface. In this work, stability, structure, and microbial capture capabilities were evaluated as a function of network properties. It was found that network structure alone was sufficient for bacterial capture, even with networks composed of the adhesion-resistant polymer, poly(ethylene glycol). The synthetic networks provide an excellent, yet simple, means of independently characterizing mucin network properties (e.g., surface chemistry, stiffness, and pore size). PMID:24992241

  8. Towards XNA nanotechnology: new materials from synthetic genetic polymers

    PubMed Central

    Pinheiro, Vitor B.; Holliger, Philipp

    2014-01-01

    Nucleic acids display remarkable properties beyond information storage and propagation. The well-understood base pairing rules have enabled nucleic acids to be assembled into nanostructures of ever increasing complexity. Although nanostructures can be constructed using other building blocks, including peptides and lipids, it is the capacity to evolve that sets nucleic acids apart from all other nanoscale building materials. Nonetheless, the poor chemical and biological stability of DNA and RNA constrain their applications. Recent advances in nucleic acid chemistry and polymerase engineering enable the synthesis, replication, and evolution of a range of synthetic genetic polymers (XNAs) with improved chemical and biological stability. We discuss the impact of this technology on the generation of XNA ligands, enzymes, and nanostructures with tailor-made chemistry. PMID:24745974

  9. Supramolecular organization of heteroxylan-dehydrogenation polymers (synthetic lignin) nanoparticles.

    PubMed

    Barakat, Abdellatif; Gaillard, Cédric; Lairez, Didier; Saulnier, Luc; Chabbert, Brigitte; Cathala, Bernard

    2008-02-01

    The supramolecular organization of particles composed of heteroxylans (HX) and synthetic lignin (dehydrogenation polymer, DHPs) was studied by light scattering (LS), atomic force microscopy (AFM), and fluorescent probes. Results from static and quasi-elastic light scattering indicate a dense core surrounded by a soft corona. Such organization is also supported by AFM images of the particles that display Gaussian height profiles when a low tapping force is applied, whereas the shape of the profile obtained at a higher mechanical solicitation is irregular and sharp due to deformation of the particles resulting from the tip indentation. This suggests a difference in mechanical behavior between the inner and outer parts of the particles. The formation of local chemical heterogeneities was demonstrated by use of two fluorescent polarity probes (pyrene and methyl-amino-pyrene) to be induced by the core-corona organization.

  10. Retinal pigment epithelium engineering using synthetic biodegradable polymers.

    PubMed

    Lu, L; Yaszemski, M J; Mikos, A G

    2001-12-01

    Retinal pigment epithelium (RPE) plays a key role in the maintenance of the normal functions of the retina, especially photoreceptors. Alteration in RPE structure and function is implicated in a variety of ocular disorders. Tissue engineering strategies using synthetic biodegradable polymers as temporary substrates for RPE cell culture and subsequent transplantation may provide a promising new therapy. In this review article, the manufacture of thin biodegradable poly(DL-lactic-co-glycolic acid) (PLGA) films and their degradation behavior in vitro are discussed. RPE cell proliferation and differentiation on these PLGA films are reviewed. The fabrication of model substrates with desired chemical micropatterns in the micrometer scale is discussed and the effects of surface patterning on RPE morphology and function are assessed. Finally. the preparation of biodegradable micropatterns with adhesive PLGA and non-adhesive poly(ethylene glycol)/PLA domains to modulate RPE cell adhesion is presented.

  11. Towards XNA nanotechnology: new materials from synthetic genetic polymers.

    PubMed

    Pinheiro, Vitor B; Holliger, Philipp

    2014-06-01

    Nucleic acids display remarkable properties beyond information storage and propagation. The well-understood base pairing rules have enabled nucleic acids to be assembled into nanostructures of ever increasing complexity. Although nanostructures can be constructed using other building blocks, including peptides and lipids, it is the capacity to evolve that sets nucleic acids apart from all other nanoscale building materials. Nonetheless, the poor chemical and biological stability of DNA and RNA constrain their applications. Recent advances in nucleic acid chemistry and polymerase engineering enable the synthesis, replication, and evolution of a range of synthetic genetic polymers (XNAs) with improved chemical and biological stability. We discuss the impact of this technology on the generation of XNA ligands, enzymes, and nanostructures with tailor-made chemistry. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  12. A molecular model for epsilon-caprolactam-based intercalated polymer clay nanocomposite: Integrating modeling and experiments.

    PubMed

    Sikdar, Debashis; Katti, Dinesh R; Katti, Kalpana S

    2006-08-29

    In studying the morphology, molecular interactions, and physical properties of organically modified montmorillonite (OMMT) and polymer clay nanocomposites (PCNs) through molecular dynamics (MD), the construction of the molecular model of OMMT and PCN is important. Better understanding of interaction between various constituents of PCN will improve the design of polymer clay nanocomposite systems. MD is an excellent tool to study interactions, which require accurate modeling of PCN under consideration. Previously, the PCN models were constructed by different researchers on the basis of specific criteria such as minimum energy configuration, density of the polymer clay nanocomposite, and so forth. However, in this article we describe the development of models combining experimental and conventional molecular modeling to develop models, which are more representative of true intercalated PCN systems. The models were used for studying the morphological interactions and physical properties. These studies gave useful information regarding orientation of organic modifiers, area of coverage of organic modifiers over the interlayer clay surface, interaction of organic modifiers with clay in OMMT, interaction among different constituents of PCN, conformational and density change, and actual proportion of mixing of polymer with clay in PCN. We have X-ray diffraction and photoacoustic Fourier transform infrared spectroscopy to verify the model.

  13. Synthesis of bulk-size transparent gadolinium oxide-polymer nanocomposites for gamma ray spectroscopy.

    PubMed

    Cai, Wen; Chen, Qi; Cherepy, Nerine; Dooraghi, Alex; Kishpaugh, David; Chatziioannou, Arion; Payne, Stephen; Xiang, Weidong; Pei, Qibing

    2013-03-14

    Heavy element loaded polymer composites have long been proposed to detect high energy X- and γ-rays upon scintillation. The previously reported bulk composite scintillators have achieved limited success because of the diminished light output resulting from fluorescence quenching and opacity. We demonstrate the synthesis of a transparent nanocomposite comprising gadolinium oxide nanocrystals uniformly dispersed in bulk-size samples at a high loading content. The strategy to avoid luminescence quenching and opacity in the nanocomposite was successfully deployed, which led to the radioluminescence light yield of up to 27 000/MeV, about twice as much as standard commercial plastic scintillators. Nanocomposites monoliths (14 mm diameter by 3 mm thickness) with 31 wt% loading of nanocrystals generated a photoelectric peak for Cs-137 gamma (662 keV) with 11.4% energy resolution.

  14. Polymer-ZnO nanocomposites foils and thin films for UV protection

    SciTech Connect

    Shanshool, Haider Mohammed; Yahaya, Muhammad; Abdullah, Ibtisam Yahya; Yunus, Wan Mahmood Mat

    2014-09-03

    The damage of UV radiation on human eye and skin is extensively studied. In the present work, the nanocomposites foils and thin films have been prepared by using casting method and spin coating, respectively. Nanocomposites were prepared by mixing ZnO nanoparticles with Polymethyl methacrylate (PMMA) and Polyvinylidene fluoride (PVDF) as polymer matrix. Different contents of ZnO nanoparticles were used as filler in the nanocomposites. UV-Vis spectra showed very low transmittance in UV region that decreases with increase content of ZnO. PVDF/ZnO samples showed the lowest transmittance. The rough surface of PVDF was observed from SEM image. While a homogeneous dispersion of ZnO nanoparticles in PMMA were indicated by FESEM images.

  15. Hydrolyzed hexagonal boron nitride/polymer nanocomposites for transparent gas barrier film.

    PubMed

    Kim, Tan Young; Song, Eun Ho; Kang, Byung Hyun; Kim, Se Jung; Lee, Yun-Hi; Ju, Byeong-Kwon

    2017-03-24

    A flexible thin gas barrier film formed by layer-by-layer (LBL) assembly has been studied. We propose for the first time that hexagonal boron nitride (h-BN) can be used in LBL assembly. When dispersed in water through sonication-assisted hydrolysis, h-BN develops hydroxyl groups that electrostatically couple with the cationic polymer polydiallyldimethylammonium chloride (PDDA). This process produces hydroxyl-functional h-BN/PDDA nanocomposites. The nanocomposites exhibit well exfoliated and highly ordered h-BN nanosheets, which results in an extremely high visual clarity, with an average transmittance of 99% in the visible spectrum. Moreover, well aligned nanocomposites extend gas diffusion path that reduce water vapor transmission rate to 1.3 × 10(-2) g m(-2) d(-1). The simple and fast LBL process demonstrated here can be applied in many gas barrier applications.

  16. Hydrolyzed hexagonal boron nitride/polymer nanocomposites for transparent gas barrier film

    NASA Astrophysics Data System (ADS)

    Kim, Tan Young; Song, Eun Ho; Kang, Byung Hyun; Kim, Se Jung; Lee, Yun-Hi; Ju, Byeong-Kwon

    2017-03-01

    A flexible thin gas barrier film formed by layer-by-layer (LBL) assembly has been studied. We propose for the first time that hexagonal boron nitride (h-BN) can be used in LBL assembly. When dispersed in water through sonication-assisted hydrolysis, h-BN develops hydroxyl groups that electrostatically couple with the cationic polymer polydiallyldimethylammonium chloride (PDDA). This process produces hydroxyl-functional h-BN/PDDA nanocomposites. The nanocomposites exhibit well exfoliated and highly ordered h-BN nanosheets, which results in an extremely high visual clarity, with an average transmittance of 99% in the visible spectrum. Moreover, well aligned nanocomposites extend gas diffusion path that reduce water vapor transmission rate to 1.3 × 10‑2 g m‑2 d‑1. The simple and fast LBL process demonstrated here can be applied in many gas barrier applications.

  17. Highly transparent Bi2MoO6- and Bi2WO6-polymer nanocomposites.

    PubMed

    Wollmann, P; Grothe, J; Ziegler, C; Kaskel, S

    2011-04-01

    A combined method of precipitation, phase transfer into organic solvent, solvothermal treatment and subsequent in situ polymerization was used to integrate nanocrystalline Bi2MoO6- and Bi2WO6-particles into a polymer matrix of poly-laurylacrylate. The presented method offers a new and gentle way to produce highly transparent bulk nanocomposites containing evenly distributed Bi2MoO6- and Bi2WO6-nanoparticles. Characterization results of DLS-, XRD-, REM- and TEM-measurements are presented as well as solid state UV/VIS-measurements of the particles. The transparent nanocomposites were characterized using UV/VIS-spectroscopy and ellipsometry. All composites show a good transmission in the range from 800-400 nm. The particle content of the nanocomposites was measured with TG-measurements.

  18. Synthesis of bulk-size transparent gadolinium oxide–polymer nanocomposites for gamma ray spectroscopy

    PubMed Central

    Cai, Wen; Chen, Qi; Cherepy, Nerine; Dooraghi, Alex; Kishpaugh, David; Chatziioannou, Arion; Payne, Stephen; Xiang, Weidong

    2015-01-01

    Heavy element loaded polymer composites have long been proposed to detect high energy X- and γ-rays upon scintillation. The previously reported bulk composite scintillators have achieved limited success because of the diminished light output resulting from fluorescence quenching and opacity. We demonstrate the synthesis of a transparent nanocomposite comprising gadolinium oxide nanocrystals uniformly dispersed in bulk-size samples at a high loading content. The strategy to avoid luminescence quenching and opacity in the nanocomposite was successfully deployed, which led to the radioluminescence light yield of up to 27 000/MeV, about twice as much as standard commercial plastic scintillators. Nanocomposites monoliths (14 mm diameter by 3 mm thickness) with 31 wt% loading of nanocrystals generated a photoelectric peak for Cs-137 gamma (662 keV) with 11.4% energy resolution. PMID:26478816

  19. Optical recording in functional polymer nanocomposites by multi-beam interference holography

    NASA Astrophysics Data System (ADS)

    Zhuk, Dmitrij; Burunkova, Julia; Kalabin, Viacheslav; Csarnovics, Istvan; Kokenyesi, Sandor

    2017-05-01

    Our investigations relate to the development of new polymer nanocomposite materials and technologies for fabrication of photonic elements like gratings, integrated elements, photonic crystals. The goal of the present work was the development and application of the multi-beam interference method for one step, direct formation of 1-, 2- or even 3D photonic structures in functional acrylate nanocomposites, which contain SiO2 and Au nanoparticles and which are sensitized to blue and green laser illumination. The presence of gold nanoparticles and possibility to excite plasmonic effects can essentially influence the polymerization processes and the spatial redistribution of nanoparticles in the nanocomposite during the recording. This way surface and volume phase reliefs can be recorded. It is essential, that no additional treatments of the material after the recording are necessary and the elements possess high transparency, are stable after some relaxation time. New functionalities can be provided to the recorded structures if luminescent materials are added to such materials.

  20. Reading polymers: sequencing of natural and synthetic macromolecules.

    PubMed

    Mutlu, Hatice; Lutz, Jean-François

    2014-11-24

    The sequencing of biopolymers such as proteins and DNA is among the most significant scientific achievements of the 20th century. Indeed, modern chemical methods for sequence analysis allow reading and understanding the codes of life. Thus, sequencing methods currently play a major role in applications as diverse as genomics, gene therapy, biotechnology, and data storage. However, in terms of fundamental science, sequencing is not really a question of molecular biology but rather a more general topic in macromolecular chemistry. Broadly speaking, it can be defined as the analysis of comonomer sequences in copolymers. However, relatively different approaches have been used in the past to study monomer sequences in biological and manmade polymers. Yet, these "cultural" differences are slowly fading away with the recent development of synthetic sequence-controlled polymers. In this context, the aim of this Minireview is to present an overview of the tools that are currently available for sequence analysis in macromolecular science. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Shear, Bulk, and Young's Moduli of Clay/Polymer Nanocomposites Containing the Stacks of Intercalated Layers as Pseudoparticles

    NASA Astrophysics Data System (ADS)

    Zare, Yasser

    2016-10-01

    The pseudoparticles include the stacks of intercalated layers in the case of incomplete clay exfoliation in clay/polymer nanocomposites. In this article, the effects of pseudoparticle properties on the shear, bulk, and Young's moduli of nanocomposites are studied using the Norris model. The properties of pseudoparticles are determined in some samples by the experimental data of Young's modulus and the roles of pseudoparticles in the shear, bulk, and Young's moduli of nanocomposites are discussed. The calculations show a good agreement with the experimental data when the pseudoparticles are taken into account in the samples. A low number of clay layers in the pseudoparticles present high moduli in nanocomposites. Moreover, the Poisson ratio and Young's modulus of polymer matrix play different roles in the shear, bulk, and Young's moduli of nanocomposites.

  2. Focus: Structure and dynamics of the interfacial layer in polymer nanocomposites with attractive interactions

    NASA Astrophysics Data System (ADS)

    Cheng, Shiwang; Carroll, Bobby; Bocharova, Vera; Carrillo, Jan-Michael; Sumpter, Bobby G.; Sokolov, Alexei P.

    2017-05-01

    In recent years it has become clear that the interfacial layer formed around nanoparticles in polymer nanocomposites (PNCs) is critical for controlling their macroscopic properties. The interfacial layer occupies a significant volume fraction of the polymer matrix in PNCs and creates strong intrinsic heterogeneity in their structure and dynamics. Here, we focus on analysis of the structure and dynamics of the interfacial region in model PNCs with well-dispersed, spherical nanoparticles with attractive interactions. First, we discuss several experimental techniques that provide structural and dynamic information on the interfacial region in PNCs. Then, we discuss the role of various microscopic parameters in controlling structure and dynamics of the interfacial layer. The analysis presented emphasizes the importance of the polymer-nanoparticle interactions for the slowing down dynamics in the interfacial region, while the thickness of the interfacial layer appears to be dependent on chain rigidity, and has been shown to increase with cooling upon approaching the glass transition. Aside from chain rigidity and polymer-nanoparticle interactions, the interfacial layer properties are also affected by the molecular weight of the polymer and the size of the nanoparticles. In the final part of this focus article, we emphasize the important challenges in the field of polymer nanocomposites and a potential analogy with the behavior observed in thin films.

  3. Conducting polymer nanocomposites loaded with nanotubes and fibers for electrical and thermal applications

    NASA Astrophysics Data System (ADS)

    Chiguma, Jasper

    The design, fabrication and measurement of electrical and thermal properties of polymers loaded with nanotubes and fibers are the foci of the work presented in this dissertation. The resulting products of blending polymers with nanomaterials are called nanocomposites and are already finding applications in many areas of human endeavour. Among some of the most recent envisioned applications of nanocomposites is in electronic devices as thermal interface materials (TIMs). This potential application as TIMs, has been made more real by the realization that carbon nanotubes, could potentially transfer their high electrical, thermal and mechanical properties to polymers in the nanocomposites. In Chapter 1, the events leading to the discovery of carbon nanotubes are reviewed followed by an elaborate discussion of their structure and properties. The discussion of the structure and properties of carbon nanotubes help in understanding the envisaged applications. Chapter 2 focuses on the fabrication of insulating polymer nanocomposites, their electrical and mechanical properties. Poly (methyl methacrylate) (PMMA) and a polyimide formed by reacting pyromellitic dianhydride (PMDA) and 4, 4'-oxydianiline (ODA) (PMDA-ODA) nanocomposites with carbon nanotubes were prepared by in-situ polymerization. Poly (1-methyl-4-pentene) (TPX), Polycarbonate (PC), Poly (vinyl chloride) (PVC), Poly (acrylonitrile-butadiene-styrene) (ABS), the alloys ABS-PC, ABS-PVC, and ABS-PC-PVC nanocomposites were prepared from the respective polymers and carbon nanotubes and their mechanical and electrical properties measured. Chapter 3 covers the nanocomposites that were prepared by the in-situ polymerization of the conducting polymers Polyaniline (PANi), Polypyrrole (PPy) and Poly (3, 4-ethylenedioxythiophene) (PEDOT) by in-situ polymerization. These are evaluated for electrical conductivity. The use of surfactants in facilitating carbon nanotube dispersion is discussed and applied in the preparation of

  4. Nanocomposites of polymers with layered inorganic nanofillers: Antimicrobial activity, thermo-mechanical properties, morphology, and dispersion

    NASA Astrophysics Data System (ADS)

    Songtipya, Ponusa

    In the first part of the thesis, polyethylene/layered silicate nanocomposites that exhibit an antimicrobial activity were synthesized and studied. Their antimicrobial activity was designed to originate from non-leaching, novel cationic modifiers---amine-based surfactants---used as the organic-modification of the fillers. Specifically, PE/organically-modified montmorillonite ( mmt) nanocomposites were prepared via melt-processing, and simultaneous dispersion and antimicrobial activity was designed by proper choice of the fillers' organic modification. The antimicrobial activity was measured against three micotoxinogen fungal strains (Penicillium roqueforti and claviforme, and Fusarium graminearum ). Various mmt-based organofillers, which only differ in the type or amount of their organic modification, were used to exemplify how these surfactants can be designed to render antifungal activity to the fillers themselves and the respective nanocomposites. A comparative discussion of the growth of fungi on unfilled PE and nanocomposite PE films is used to demonstrate how the antimicrobial efficacy is dictated by the surfactant chemistry and, further, how the nanocomposites' inhibitory activity compares to that of the organo-fillers and the surfactants. An attempt to improve the thermomechanical reinforcement of PE/mmt nanocomposites while maintaining their antimicrobial activity, was also carried out by combining two different organically modified montmorillonites. However, a uniform microscopic dispersion could not be achieved through this approach. In the second part of this thesis, a number of fundamental studies relating to structure-property relations in nanocomposites were carried out, towards unveiling strategies that can concurrently optimize selected properties of polymers by the addition of nanofillers. Specifically, the dispersion-crystallinity-reinforcement relations in HDPE/mmt nanocomposites was investigated. The influence of a functional HDPE compatibilizer

  5. Electrically tunable micro-lens with a strain-enhanced polymer nanocomposite actuator (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Costache, Florenta A.; Pawlik, Boscij; Rieck, Andreas

    2017-02-01

    A fluid-filled micro-lens concept with an electrically driven polymer actuator was developed in view of optimization of its variation in focal length. The high strain electrostrictive terpolymer P(VDF-TrFE-CFE) was first used in the actuator design for this purpose. Our study showed that the electric field-induced strain in polymer thin films could be even further enhanced by mixing high-k BaTiO3 nanoparticles in the terpolymer. A newly developed nanocomposite P(VDF-TrFE-CFE) / BaTiO3 ring-shaped actuator was implemented into the 3 mm aperture, liquid-filled micro-lens concept. The micro-lens was fabricated in a wafer-level process flow, which included micromachining of fluidic chambers on silicon wafers, thin film nanocomposite actuator processing, assembly through wafer bonding and chip filling with liquids. Particular characteristics of the nanocomposite were taken into account such as the homogeneous nanoparticle dispersion into the thin film with impact on thin film dielectric breakdown, electrode adherence as well as nanocomposite film etching. Variable focal length micro-lenses conceps with a single fluidic chamber but also with two fluidic chambers (a design, which can potentially improve the lens membrane stability) were fabricated and characterized. We could demonstrate a wide focal length variation of tens of diopters first for a single chamber plano-convex micro-lens obtained by adjusting the voltage applied on the integrated actuator.

  6. From carbon nanotubes and silicate layers to graphene platelets for polymer nanocomposites.

    PubMed

    Zaman, Izzuddin; Kuan, Hsu-Chiang; Dai, Jingfei; Kawashima, Nobuyuki; Michelmore, Andrew; Sovi, Alex; Dong, Songyi; Luong, Lee; Ma, Jun

    2012-08-07

    In spite of extensive studies conducted on carbon nanotubes and silicate layers for their polymer-based nanocomposites, the rise of graphene now provides a more promising candidate due to its exceptionally high mechanical performance and electrical and thermal conductivities. The present study developed a facile approach to fabricate epoxy-graphene nanocomposites by thermally expanding a commercial product followed by ultrasonication and solution-compounding with epoxy, and investigated their morphologies, mechanical properties, electrical conductivity and thermal mechanical behaviour. Graphene platelets (GnPs) of 3.57 ± 0.50 nm in thickness were created after the expanded product was dispersed in tetrahydrofuran using 60 min ultrasonication. Since epoxy resins cured by various hardeners are widely used in industries, we chose two common hardeners: polyoxypropylene (J230) and 4,4'-diaminodiphenylsulfone (DDS). DDS-cured nanocomposites showed a better dispersion and exfoliation of GnPs, a higher improvement (573%) in fracture energy release rate and a lower percolation threshold (0.612 vol%) for electrical conductivity, because DDS contains benzene groups which create π-π interactions with GnPs promoting a higher degree of dispersion and exfoliation of GnPs during curing. This research pointed out a potential trend where GnPs would replace carbon nanotubes and silicate layers for many applications of polymer nanocomposites.

  7. Multiscale model to investigate the effect of graphene on the fracture characteristics of graphene/polymer nanocomposites.

    PubMed

    Parashar, Avinash; Mertiny, Pierre

    2012-10-26

    In this theoretical research work, the fracture characteristics of graphene-modified polymer nanocomposites were studied. A three-dimensional representative volume element-based multiscale model was developed in a finite element environment. Graphene sheets were modeled in an atomistic state, whereas the polymer matrix was modeled as a continuum. Van der Waals interactions between the matrix and graphene sheets were simulated employing truss elements. Fracture characteristics of graphene/polymer nanocomposites were investigated in conjunction with the virtual crack closure technique. The results demonstrate that fracture characteristics in terms of the strain energy release rate were affected for a crack lying in a polymer reinforced with graphene. A shielding effect from the crack driving forces is considered to be the reason for enhanced fracture resistance in graphene-modified polymer nanocomposites.

  8. Multiscale model to investigate the effect of graphene on the fracture characteristics of graphene/polymer nanocomposites

    PubMed Central

    2012-01-01

    In this theoretical research work, the fracture characteristics of graphene-modified polymer nanocomposites were studied. A three-dimensional representative volume element-based multiscale model was developed in a finite element environment. Graphene sheets were modeled in an atomistic state, whereas the polymer matrix was modeled as a continuum. Van der Waals interactions between the matrix and graphene sheets were simulated employing truss elements. Fracture characteristics of graphene/polymer nanocomposites were investigated in conjunction with the virtual crack closure technique. The results demonstrate that fracture characteristics in terms of the strain energy release rate were affected for a crack lying in a polymer reinforced with graphene. A shielding effect from the crack driving forces is considered to be the reason for enhanced fracture resistance in graphene-modified polymer nanocomposites. PMID:23101943

  9. Laser formation of Bragg gratings in polymer nanocomposite materials

    SciTech Connect

    Nazarov, M M; Khaydukov, K V; Sokolov, V I; Khaydukov, E V

    2016-01-31

    The method investigated in this work is based on the laser-induced, spatially inhomogeneous polymerisation of nanocomposite materials and allows control over the motion and structuring of nanoparticles. The mechanisms of nanoparticle concentration redistribution in the process of radical photopolymerisation are studied. It is shown that under the condition of spatially inhomogeneous illumination of a nanocomposite material, nanoparticles are diffused from the illuminated areas into the dark fields. Diffraction gratings with a thickness of 8 μm and a refractive index modulation of 1 × 10{sup -2} are written in an OCM-2 monomer impregnated by silicon nanoparticles. The gratings may be used in the development of narrowband filters, in holographic information recording and as dispersion elements in integrated optical devices. (interaction of laser radiation with matter. laser plasma)

  10. Polymer nanocomposites with controllable distribution and arrangement of inorganic nanocomponents

    NASA Astrophysics Data System (ADS)

    Dou, Yuandong; Lin, Kaili; Chang, Jiang

    2011-04-01

    A novel approach to prepare nanocomposites encapsulating one or multiple kinds of nanoelements with diverse spatial distribution patterns and orientational organization manners was reported. Nanowires were uniaxially aligned over macroscopic dimensions within bulk composites, which recreated the basic structural hierarchy of bone and displayed comparable excellent mechanical properties.A novel approach to prepare nanocomposites encapsulating one or multiple kinds of nanoelements with diverse spatial distribution patterns and orientational organization manners was reported. Nanowires were uniaxially aligned over macroscopic dimensions within bulk composites, which recreated the basic structural hierarchy of bone and displayed comparable excellent mechanical properties. Electronic supplementary information (ESI) available: Experimental details, additional figures and compressive mechanical properties of the bulk composite materials. See DOI: 10.1039/c1nr10028a

  11. Surface modification of a POSS-nanocomposite material to enhance cellular integration of a synthetic bioscaffold.

    PubMed

    Crowley, Claire; Klanrit, Poramate; Butler, Colin R; Varanou, Aikaterini; Platé, Manuela; Hynds, Robert E; Chambers, Rachel C; Seifalian, Alexander M; Birchall, Martin A; Janes, Sam M

    2016-03-01

    Polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) is a versatile nanocomposite biomaterial with growing applications as a bioscaffold for tissue engineering. Integration of synthetic implants with host tissue can be problematic but could be improved by topographical modifications. We describe optimization of POSS-PCU by dispersion of porogens (sodium bicarbonate (NaHCO3), sodium chloride (NaCl) and sucrose) onto the material surface, with the principle aim of increasing surface porosity, thus providing additional opportunities for improved cellular and vascular ingrowth. We assess the effect of the porogens on the material's mechanical strength, surface chemistry, wettability and cytocompatibilty. Surface porosity was characterized by scanning electron microscopy (SEM). There was no alteration in surface chemistry and wettability and only modest changes in mechanical properties were detected. The size of porogens correlated well with the porosity of the construct produced and larger porogens improved interconnectivity of spaces within constructs. Using primary human bronchial epithelial cells (HBECs) we demonstrate moderate in vitro cytocompatibility for all surface modifications; however, larger pores resulted in cellular aggregation. These cells were able to differentiate on POSS-PCU scaffolds. Implantation of the scaffold in vivo demonstrated that larger pore sizes favor cellular integration and vascular ingrowth. These experiments demonstrate that surface modification with large porogens can improve POSS-PCU nanocomposite scaffold integration and suggest the need to strike a balance between the non-porous surfaces required for epithelial coverage and the porous structure required for integration and vascularization of synthetic scaffolds in future construct design. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  12. Surface modification of a POSS-nanocomposite material to enhance cellular integration of a synthetic bioscaffold

    PubMed Central

    Crowley, Claire; Klanrit, Poramate; Butler, Colin R.; Varanou, Aikaterini; Platé, Manuela; Hynds, Robert E.; Chambers, Rachel C.; Seifalian, Alexander M.; Birchall, Martin A.; Janes, Sam M.

    2016-01-01

    Polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) is a versatile nanocomposite biomaterial with growing applications as a bioscaffold for tissue engineering. Integration of synthetic implants with host tissue can be problematic but could be improved by topographical modifications. We describe optimization of POSS-PCU by dispersion of porogens (sodium bicarbonate (NaHCO3), sodium chloride (NaCl) and sucrose) onto the material surface, with the principle aim of increasing surface porosity, thus providing additional opportunities for improved cellular and vascular ingrowth. We assess the effect of the porogens on the material's mechanical strength, surface chemistry, wettability and cytocompatibilty. Surface porosity was characterized by scanning electron microscopy (SEM). There was no alteration in surface chemistry and wettability and only modest changes in mechanical properties were detected. The size of porogens correlated well with the porosity of the construct produced and larger porogens improved interconnectivity of spaces within constructs. Using primary human bronchial epithelial cells (HBECs) we demonstrate moderate in vitro cytocompatibility for all surface modifications; however, larger pores resulted in cellular aggregation. These cells were able to differentiate on POSS-PCU scaffolds. Implantation of the scaffold in vivo demonstrated that larger pore sizes favor cellular integration and vascular ingrowth. These experiments demonstrate that surface modification with large porogens can improve POSS-PCU nanocomposite scaffold integration and suggest the need to strike a balance between the non-porous surfaces required for epithelial coverage and the porous structure required for integration and vascularization of synthetic scaffolds in future construct design. PMID:26790147

  13. Nanocomposite polymer structures for optical sensors of hydrogen sulfide

    NASA Astrophysics Data System (ADS)

    Sergeev, A. A.; Mironenko, A. Yu.; Nazirov, A. E.; Leonov, A. A.; Voznesenskii, S. S.

    2017-08-01

    Composite coatings based on gold and silver nanoparticles reduced in situ in the film of chitosan polysaccharide are studied. In the presence of hydrogen sulfide, the maximum of plasmon resonance of the nanoparticles that is proportional to the analyte concentration decreases. The detection limits for hydrogen sulfide are 0.1 and 5 ppm for the chitosan/silver and chitosan/gold nanocomposites, respectively.

  14. Recent Progress Toward the Templated Synthesis and Directed Evolution of Sequence-Defined Synthetic Polymers

    PubMed Central

    Brudno, Yevgeny; Liu, David R.

    2009-01-01

    Biological polymers such as nucleic acids and proteins are ubiquitous in living systems, but their ability to address problems beyond those found in nature is constrained by factors such as chemical or biological instability, limited building-block functionality, bioavailability, and immunogenicity. In principle, sequence-defined synthetic polymers based on nonbiological monomers and backbones might overcome these constraints; however, identifying the sequence of a synthetic polymer that possesses a specific desired functional property remains a major challenge. Molecular evolution can rapidly generate functional polymers but requires a means of translating amplifiable templates such as nucleic acids into the polymer being evolved. This review covers recent advances in the enzymatic and nonenzymatic templated polymerization of nonnatural polymers and their potential applications in the directed evolution of sequence-defined synthetic polymers. PMID:19318208

  15. Recent progress toward the templated synthesis and directed evolution of sequence-defined synthetic polymers.

    PubMed

    Brudno, Yevgeny; Liu, David R

    2009-03-27

    Biological polymers such as nucleic acids and proteins are ubiquitous in living systems, but their ability to address problems beyond those found in nature is constrained by factors such as chemical or biological instability, limited building-block functionality, bioavailability, and immunogenicity. In principle, sequence-defined synthetic polymers based on nonbiological monomers and backbones might overcome these constraints; however, identifying the sequence of a synthetic polymer that possesses a specific desired functional property remains a major challenge. Molecular evolution can rapidly generate functional polymers but requires a means of translating amplifiable templates such as nucleic acids into the polymer being evolved. This review covers recent advances in the enzymatic and nonenzymatic templated polymerization of nonnatural polymers and their potential applications in the directed evolution of sequence-defined synthetic polymers.

  16. Revealing the toughening mechanism of graphene-polymer nanocomposite through molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Shen, Jianxiang; Zheng, Zijian; Wu, Youping; Zhang, Liqun

    2015-07-01

    By employing united atom molecular dynamics simulation, we have investigated the effects of polymer-graphene interaction {\\varepsilon }np, volume fraction of graphene φ , thermodynamics of polymer matrix (rubbery versus glassy), interfacial interaction in the case of the same dispersion state, shape of nanoparticles (NPs) such as {{{C}}}60, CNT and graphene at the same loading on the toughening efficiency of polymer nanocomposites. By beginning with the pure polymer, we observe that a plateau stress occurs at long chain length because entangled polymer chains in fibrils cannot become broken. We find that the work needed to dissipate during the failure increases with the increase of {\\varepsilon }np and φ , and the yield point in the stress-strain behavior occurs at a smaller strain for an attractive NPs filled system compared to the pure case, attributed to the more mechanically heterogeneous environment. The thermodynamics of the polymer matrix (below and above Tg) seems to have a significant effect on the toughening efficiency of graphene sheets. In the case of the same dispersion state, stronger interfacial interaction always induces long and highly orientated polymer fibrils along the deformation direction, with graphene sheets being encapsulated in these fiber-like bundles. By characterizing the interaction energy between polymer-polymer and polymer-graphene as a function of the strain, we find that the separation of polymer chains from the graphene sheets cease immediately after the yield point, followed by the continuous propagation of the cavities by excluding surrounded polymer chains and graphene sheets together. We also find that at the same attractive interfacial interaction and same loading, the toughening efficiency exhibits the following order: graphene > CNT > {{{C}}}60. Generally, the toughening mechanism of graphene sheets results from the formation of long and highly orientated polymer fibrils to prevent the occurrence of the rupture, which

  17. Identification of Synthetic Polymers and Copolymers by Analytical Pyrolysis-Gas Chromatography/Mass Spectrometry

    ERIC Educational Resources Information Center

    Kusch, Peter

    2014-01-01

    An experiment for the identification of synthetic polymers and copolymers by analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was developed and performed in the polymer analysis courses for third-year undergraduate students of chemistry with material sciences, and for first-year postgraduate students of polymer sciences. In…

  18. Identification of Synthetic Polymers and Copolymers by Analytical Pyrolysis-Gas Chromatography/Mass Spectrometry

    ERIC Educational Resources Information Center

    Kusch, Peter

    2014-01-01

    An experiment for the identification of synthetic polymers and copolymers by analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was developed and performed in the polymer analysis courses for third-year undergraduate students of chemistry with material sciences, and for first-year postgraduate students of polymer sciences. In…

  19. Reactive template synthesis of polypyrrole nanotubes for fabricating metal/conducting polymer nanocomposites.

    PubMed

    Zhang, Jun; Liu, Xianghong; Zhang, Lixue; Cao, Bingqiang; Wu, Shihua

    2013-03-25

    Unique nanocomposites of polypyrrole/Au and polypyrrole/Pt hybrid nanotubes are synthesized employing polypyrrole (PPy) nanotubes as an advanced support by solution reduction. The conducting polymer PPy nanotubes are fabricated by using pre-prepared MnO2 nanowires as the reactive templates. MnO2 nanowires induce the 1D polymerization of pyrrole monomers and the simultaneous dissolution of the templates affords the hollow tube-like structure. The loading content of metal nanoparticles in the nanocomposites could be adjusted by simply changing the amount of metal precursors. This work provides an efficient approach to fabricate an important kind of metal/conducting polymer hybrid nanotubes that are potentially useful for electrocatalyst and sensor materials. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Big Effect of Small Nanoparticles: A Shift in Paradigm for Polymer Nanocomposites

    DOE PAGES

    Cheng, Shiwang; Xie, Shi-Jie; Carrillo, Jan-Michael Y.; ...

    2017-01-04

    Polymer nanocomposites (PNCs) are important materials that are widely used in many current technologies and potentially have broader applications in the future due to their excellent property of tunability, light weight and low cost. But, expanding the limits in property enhancement remains a fundamental scientific challenge. We demonstrate that well-dispersed, small (diameter ~1.8 nm) nanoparticles with attractive interactions lead to unexpectedly large and qualitatively new changes in PNC structural dynamics in comparison to conventional composites based on particles of diameter ~10-50 nm. At the same time, the zero-shear viscosity at high temperatures remains comparable to that of the neat polymer,more » thereby retaining good processibility and resolving a major challenge in PNC applications. These results suggest that the nanoparticle mobility and relatively short lifetimes of nanoparticlepolymer associations open qualitatively new horizons in tunability of macroscopic properties in nanocomposites with high potential for the development of new functional materials.« less

  1. Highly Conductive Water-Based Polymer/Graphene Nanocomposites for Printed Electronics.

    PubMed

    Koutsioukis, Apostolos; Georgakilas, Vasilios; Belessi, Vassiliki; Zboril, Radek

    2017-06-16

    The preparation and characterization of highly conductive carbon inks is described based on nanocomposites that combine a polystyrene-acrylic resin or water-soluble polymers with a hydrophilic graphene/carbon nanotube hybrid. The water-based carbon inks showed high electrical conductivity and could be effectively used in advanced technologies such as gravure printing for printed electronics. Moreover, the conductivity was shown to be increased with a power law of the nanohybrid volume fraction, with an exponent close to that predicted from the percolation theory, indicating a limited impact of the polymer tunneling barrier on the electrical conductivity of such nanocomposites. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Real time polymer nanocomposites-based physical nanosensors: theory and modeling.

    PubMed

    Bellucci, Stefano; Shunin, Yuri; Gopeyenko, Victor; Lobanova-Shunina, Tamara; Burlutskaya, Nataly; Zhukovskii, Yuri

    2017-09-01

    Functionalized carbon nanotubes and graphene nanoribbons nanostructures, serving as the basis for the creation of physical pressure and temperature nanosensors, are considered as tools for ecological monitoring and medical applications. Fragments of nanocarbon inclusions with different morphologies, presenting a disordered system, are regarded as models for nanocomposite materials based on carbon nanoсluster suspension in dielectric polymer environments (e.g., epoxy resins). We have formulated the approach of conductivity calculations for carbon-based polymer nanocomposites using the effective media cluster approach, disordered systems theory and conductivity mechanisms analysis, and obtained the calibration dependences. Providing a proper description of electric responses in nanosensoring systems, we demonstrate the implementation of advanced simulation models suitable for real time control nanosystems. We also consider the prospects and prototypes of the proposed physical nanosensor models providing the comparisons with experimental calibration dependences.

  3. Water-stable crosslinked sulfonated polyimide-silica nanocomposite containing interpenetrating polymer network

    NASA Astrophysics Data System (ADS)

    Lee, Chang Hyun; Hwang, Shin Young; Sohn, Joon Yong; Park, Ho Bum; Kim, Ju Young; Lee, Young Moo

    Sulfonated polyimide (SPI) interpenetrating polymer network (IPN) (IXSPI)-silica (SiO 2) nanocomposite membranes were fabricated as proton conducting solid electrolytes for fuel cells. Urethane acrylate non-ionomers (UANs) were used as dispersants to homogeneously distribute nanosized SiO 2 and, simultaneously, as crosslinkers to induce IPN structure formation. IXSPI-SiO 2 nanocomposite membranes showed high proton conductivity and hydrolytic stability, and low methanol permeability as compared with those of pristine SPI. Interestingly, the casting solvent for membrane fabrication influenced membrane performances, especially proton conductivity. In particular, dimethyl sulfoxide exhibited a strong interaction with sulfonic acid groups in the polymer matrix, which hindered them from spontaneously releasing protons and reduced the proton conductivity and electrochemical performances of the resulting membranes. Crosslinkers with long polyethylene oxide chains also contributed to improved proton conductivity and increased single cell performances.

  4. Real time polymer nanocomposites-based physical nanosensors: theory and modeling

    NASA Astrophysics Data System (ADS)

    Bellucci, Stefano; Shunin, Yuri; Gopeyenko, Victor; Lobanova-Shunina, Tamara; Burlutskaya, Nataly; Zhukovskii, Yuri

    2017-09-01

    Functionalized carbon nanotubes and graphene nanoribbons nanostructures, serving as the basis for the creation of physical pressure and temperature nanosensors, are considered as tools for ecological monitoring and medical applications. Fragments of nanocarbon inclusions with different morphologies, presenting a disordered system, are regarded as models for nanocomposite materials based on carbon nanoсluster suspension in dielectric polymer environments (e.g., epoxy resins). We have formulated the approach of conductivity calculations for carbon-based polymer nanocomposites using the effective media cluster approach, disordered systems theory and conductivity mechanisms analysis, and obtained the calibration dependences. Providing a proper description of electric responses in nanosensoring systems, we demonstrate the implementation of advanced simulation models suitable for real time control nanosystems. We also consider the prospects and prototypes of the proposed physical nanosensor models providing the comparisons with experimental calibration dependences.

  5. Barrier and long term creep properties of polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Ranade, Ajit

    The barrier properties and long term strength retention of polymers are of significant importance in a number of applications. Enhanced lifetime food packaging, substrates for OLED based flexible displays and long duration scientific balloons are among them. Higher material requirements in these applications drive the need for an accurate measurement system. Therefore, a new system was engineered with enhanced sensitivity and accuracy. Permeability of polymers is affected by permeant solubility and diffusion. One effort to decrease diffusion rates is via increasing the transport path length. We explore this through dispersion of layered silicates into polymers. Layered silicates with effective aspect ratio of 1000:1 have shown promise in improving the barrier and mechanical properties of polymers. The surface of these inorganic silicates was modified with surfactants to improve the interaction with organic polymers. The micro and nanoscale dispersion of the layered silicates was probed using optical and transmission microscopy as well as x-ray diffraction. Thermal transitions were analyzed using differential scanning calorimetry. Mechanical and permeability measurements were correlated to the dispersion and increased density. The essential structure-property relationships were established by comparing semicrystalline and amorphous polymers. Semicrystalline polymers selected were nylon-6 and polyethylene terephthalate. The amorphous polymer was polyethylene terphthalate-glycol. Densification due to the layered silicate in both semicrystalline and amorphous polymers was associated with significant impact on barrier and long term creep behavior. The inferences were confirmed by investigating a semi-crystalline polymer---polyethylene---above and below the glass transition. The results show that the layered silicate influences the amorphous segments in polymers and barrier properties are affected by synergistic influences of densification and uniform dispersion of the

  6. Transmission Electron Microscopy of Single Wall Carbon Nanotube/Polymer Nanocomposites: A First-Principles Study

    NASA Technical Reports Server (NTRS)

    Sola, Francisco; Xia, Zhenhai; Lebrion-Colon, Marisabel; Meador, Michael A.

    2012-01-01

    The physics of HRTEM image formation and electron diffraction of SWCNT in a polymer matrix were investigated theoretically on the basis of the multislice method, and the optics of a FEG Super TWIN Philips CM 200 TEM operated at 80 kV. The effect of nanocomposite thickness on both image contrast and typical electron diffraction reflections of nanofillers were explored. The implications of the results on the experimental applicability to study dispersion, chirality and diameter of nanofillers are discussed.

  7. Supramolecular Engineering of Hierarchically Self-Assembled, Bioinspired, Cholesteric Nanocomposites Formed by Cellulose Nanocrystals and Polymers.

    PubMed

    Zhu, Baolei; Merindol, Remi; Benitez, Alejandro J; Wang, Baochun; Walther, Andreas

    2016-05-04

    Natural composites are hierarchically structured by combination of ordered colloidal and molecular length scales. They inspire future, biomimetic, and lightweight nanocomposites, in which extraordinary mechanical properties are in reach by understanding and mastering hierarchical structure formation as tools to engineer multiscale deformation mechanisms. Here we describe a hierarchically self-assembled, cholesteric nanocomposite with well-defined colloid-based helical structure and supramolecular hydrogen bonds engineered on the molecular level in the polymer matrix. We use reversible addition-fragmentation transfer polymerization to synthesize well-defined hydrophilic, nonionic polymers with a varying functionalization density of 4-fold hydrogen-bonding ureidopyrimidinone (UPy) motifs. We show that these copolymers can be coassembled with cellulose nanocrystals (CNC), a sustainable, stiff, rod-like reinforcement, to give ordered cholesteric phases with characteristic photonic stop bands. The dimensions of the helical pitch are controlled by the ratio of polymer/CNC, confirming a smooth integration into the colloidal structure. With respect to the effect of the supramolecular motifs, we demonstrate that those regulate the swelling when exposing the biomimetic hybrids to water, and they allow engineering the photonic response. Moreover, the amount of hydrogen bonds and the polymer fraction are decisive in defining the mechanical properties. An Ashby plot comparing previous ordered CNC-based nanocomposites with our new hierarchical ones reveals that molecular engineering allows us to span an unprecedented mechanical property range from highest inelastic deformation (strain up to ∼13%) to highest stiffness (E ∼ 15 GPa) and combinations of both. We envisage that further rational design of the molecular interactions will provide efficient tools for enhancing the multifunctional property profiles of such bioinspired nanocomposites.

  8. Supercritical carbon dioxide-processed resorbable polymer nanocomposites for bone graft substitute applications

    NASA Astrophysics Data System (ADS)

    Baker, Kevin C.

    Numerous clinical situations necessitate the use of bone graft materials to enhance bone formation. While autologous and allogenic materials are considered the gold standards in the setting of fracture healing and spine fusion, their disadvantages, which include donor site morbidity and finite supply have stimulated research and development of novel bone graft substitute materials. Among the most promising candidate materials are resorbable polymers, composed of lactic and/or glycolic acid. While the characteristics of these materials, such as predictable degradation kinetics and biocompatibility, make them an excellent choice for bone graft substitute applications, they lack mechanical strength when synthesized with the requisite porous morphology. As such, porous resorbable polymers are often reinforced with filler materials. In the presented work, we describe the use of supercritical carbon dioxide (scCO2) processing to create porous resorbable polymeric constructs reinforced by nanostructured, organically modified Montmorillonite clay (nanoclay). scCO2 processing simultaneously disperses the nanoclay throughout the polymeric matrix, while imparting a porous morphology to the construct conducive to facilitating cellular infiltration and neoangiogenesis, which are necessary components of bone growth. With the addition of as little as 2.5wt% of nanoclay, the compressive strength of the constructs nearly doubles putting them on par with human cortico-cancellous bone. Rheological measurements indicate that the dominant mode of reinforcement of the nanocomposite constructs is the restriction of polymer chain mobility. This restriction is a function of the positive interaction between polymer chains and the nanoclay. In vivo inflammation studies indicate biocompatibility of the constructs. Ectopic osteogenesis assays have determined that the scCO2-processed nanocomposites are capable of supporting growth-factor induced bone formation. scCO 2-processed resorbable

  9. Nanoparticle/Polymer Nanocomposite Bond Coat or Coating

    NASA Technical Reports Server (NTRS)

    Miller, Sandi G.

    2011-01-01

    This innovation addresses the problem of coatings (meant to reduce gas permeation) applied to polymer matrix composites spalling off in service due to incompatibility with the polymer matrix. A bond coat/coating has been created that uses chemically functionalized nanoparticles (either clay or graphene) to create a barrier film that bonds well to the matrix resin, and provides an outstanding barrier to gas permeation. There is interest in applying clay nanoparticles as a coating/bond coat to a polymer matrix composite. Often, nanoclays are chemically functionalized with an organic compound intended to facilitate dispersion of the clay in a matrix. That organic modifier generally degrades at the processing temperature of many high-temperature polymers, rendering the clay useless as a nano-additive to high-temperature polymers. However, this innovation includes the use of organic compounds compatible with hightemperature polymer matrix, and is suitable for nanoclay functionalization, the preparation of that clay into a coating/bondcoat for high-temperature polymers, the use of the clay as a coating for composites that do not have a hightemperature requirement, and a comparable approach to the preparation of graphene coatings/bond coats for polymer matrix composites.

  10. Novel processing to produce polymer/ceramic nanocomposites by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Liang, Xinhua

    Polymeric materials can be greatly influenced by nanoscale inclusions of inorganic materials. The main goal of this thesis is to fabricate novel polymer/ceramic composite materials for two different applications using atomic layer deposition (ALD) or molecular layer deposition (MLD) methods. One is to produce well-dispersed polymer/ceramic nanocomposites with improved barrier properties for packaging applications. The other is to produce porous polymer/ceramic composites with improved bioactivity for tissue engineering applications. ALD has been successfully utilized for the conformal and uniform deposition of ultra-thin alumina and titania films on primary micron-sized polymer particles. The mechanism to initiate alumina and titania ALD on polymer particles without chemical functional groups was confirmed. A nucleation period was needed for both alumina and titania ALD on high density polyethylene (HDPE) particles and no nucleation period was needed for alumina ALD on polymethyl methacrylate particles. Titania ALD films deposited at low temperatures had an amorphous structure and showed much weaker photoactivity than common pigment-grade anatase TiO2 particles. Highly uniform and conformal ultra-thin aluminum alkoxide (alucone) polymer films were deposited on primary silica and titania nanoparticles using MLD in a fluidized bed reactor. The deposition chemistry and properties of alucone MLD films were investigated. The photoactivity of pigment-grade TiO2 particles was quenched after 20 cycles of an alucone MLD film, but the films shrank and decomposed in the presence of water, which decreased the passivation effect of the photoactivity of TiO2 particles. Well-dispersed polymer/ceramic nanocomposites were obtained by extruding alumina ALD coated HDPE particles. The diffusion coefficient of the fabricated nanocomposite membranes can be reduced by half with the inclusion of 7.3 vol.% alumina flakes. However, a corresponding increase in permeability was also observed

  11. The role of nanoparticle rigidity on the diffusion of linear polystyrene in a polymer nanocomposite

    SciTech Connect

    Miller, Brad; Imel, Adam E.; Holley, Wade; Baskaran, Durairaj; Mays, Jimmy W.; Dadmun, Mark D.

    2015-11-12

    The impact of the inclusion of a nanoparticle in a polymer matrix on the dynamics of the polymer chains is an area of recent interest. In this article, we describe the role of nanoparticle rigidity or softness on the impact of the presence of that nanoparticle on the diffusive behavior of linear polymer chains. The neutron reflectivity results clearly show that the inclusion of 10 nm soft nanoparticles in a polymer matrix (Rg ~ 20 nm) increases the diffusion coefficient of the linear polymer chain. Surprisingly, thermal analysis shows that these nanocomposites exhibit an increase in their glass transition temperature, which is incommensurate with an increase in free volume. Therefore, it appears that this effect is more complex than a simple plasticizing effect. Results from small-angle neutron scattering of the nanoparticles in solution show a structure that consists of a gel like core with a corona of free chain ends and loops. Furthermore, the increase in linear polymer diffusion may be related to an increase in constraint release mechanisms in the reptation of the polymer chain, in a similar manner to that which has been reported for the diffusion of linear polymer chains in the presence of star polymers.

  12. The role of nanoparticle rigidity on the diffusion of linear polystyrene in a polymer nanocomposite

    DOE PAGES

    Miller, Brad; Imel, Adam E.; Holley, Wade; ...

    2015-11-12

    The impact of the inclusion of a nanoparticle in a polymer matrix on the dynamics of the polymer chains is an area of recent interest. In this article, we describe the role of nanoparticle rigidity or softness on the impact of the presence of that nanoparticle on the diffusive behavior of linear polymer chains. The neutron reflectivity results clearly show that the inclusion of 10 nm soft nanoparticles in a polymer matrix (Rg ~ 20 nm) increases the diffusion coefficient of the linear polymer chain. Surprisingly, thermal analysis shows that these nanocomposites exhibit an increase in their glass transition temperature,more » which is incommensurate with an increase in free volume. Therefore, it appears that this effect is more complex than a simple plasticizing effect. Results from small-angle neutron scattering of the nanoparticles in solution show a structure that consists of a gel like core with a corona of free chain ends and loops. Furthermore, the increase in linear polymer diffusion may be related to an increase in constraint release mechanisms in the reptation of the polymer chain, in a similar manner to that which has been reported for the diffusion of linear polymer chains in the presence of star polymers.« less

  13. Relationships between structure and rheology in polymer nanocomposites probed via X-ray scattering

    NASA Astrophysics Data System (ADS)

    Pujari, Saswati

    Polymer nanocomposites have received intense attention due to their potential for significantly enhanced polymer properties like mechanical strength, thermal stability, electrical conductivity, etc. Melt state processing of these materials exposes the nanofillers to complex flow fields, which can induce changes in nanocomposite microstructure, including particle dispersion and the orientation of anisotropic nanoparticles in the polymer matrix. Since nanocomposite properties are strongly correlated with both these structural features, it is essential to develop methods to characterize such microstructural changes. This thesis reports extensive measurements of mechanical rheology and particle orientation during flow of nanocomposites based on multi-walled carbon nanotubes, clays, and graphene nanosheets. Changes in orientation of anisotropic nanoparticles are manifested in x-ray scattering images collected during shear. In-situ studies of orientation are enabled by custom designed x-ray adapted shear cells and high energy synchrotron radiation at the Advanced Photon Source in Argonne National Laboratory where these experiments were conducted. Studies of flow induced orientation in model nanotube dispersions revealed increasing sample anisotropy with increasing shear rate across concentrations and aspect ratios. In dilute dispersions the orientation dynamics was dominated by flow induced aggregation/disaggregation of MWNTs, with anisotropy primarily attributed to individually dispersed nanotubes. In concentrated suspensions, sample anisotropy resulted from flow induced elastic deformation within entangled MWNT clusters. Release of elastic energy upon flow cessation resulted in an unexpected relaxation of induced anisotropy. These studies were followed with study of more complex, but, industrially relevant nanocomposites made with polypropylene as the dispersing matrix. The high viscosity of polypropylene makes dispersion of nanoparticles difficult, and hence a careful

  14. Isolation of Aramid Nanofibers for High Strength and Toughness Polymer Nanocomposites.

    PubMed

    Lin, Jiajun; Bang, Sun Hwi; Malakooti, Mohammad H; Sodano, Henry A

    2017-03-29

    The development of nanoscale reinforcements that can be used to improve the mechanical properties of a polymer remains a challenge due to the long-standing difficulties with exfoliation and dispersion of existing materials. The dissimilar chemical nature of common nanofillers (e.g., carbon nanotubes, graphene) and polymeric matrix materials is the main reason for imperfect filler dispersion and, consequently, low mechanical performance of their composites relative to theoretical predictions. Here, aramid nanofibers that are intrinsically dispersible in many polymers are prepared from commercial aramid fibers (Kevlar) and isolated through a simple, scalable, and low-cost controlled dissolution method. Integration of the aramid nanofibers in an epoxy resin results in nanocomposites with simultaneously improved elastic modulus, strength, and fracture toughness. The improvement of these two mutually exclusive properties of nanocomposites is comparable to the enhancement of widely reported carbon nanotube reinforced nanocomposites but with a cost-effective and more feasible method to achieve uniform and stable dispersion. The results indicate the potential for aramid nanofibers as a new class of reinforcements for polymers.

  15. Release of engineered nanomaterials from polymer nanocomposites: the effect of matrix degradation.

    PubMed

    Duncan, Timothy V

    2015-01-14

    Polymer nanocomposites-polymer-based materials that incorporate filler elements possessing at least one dimension in the nanometer range-are increasingly being developed for commercial applications ranging from building infrastructure to food packaging to biomedical devices and implants. Despite a wide range of intended applications, it is also important to understand the potential for exposure to these nanofillers, which could be released during routine use or abuse of these materials so that it can be determined whether they pose a risk to human health or the environment. This article is the second of a pair that review what is known about the release of engineered nanomaterials (ENMs) from polymer nanocomposites. Two roughly separate ENM release paradigms are considered in this series: the release of ENMs via passive diffusion, desorption, and dissolution into external liquid media and the release of ENMs assisted by matrix degradation. The present article is focused primarily on the second paradigm and includes a thorough, critical review of the associated body of peer-reviewed literature on ENM release by matrix degradation mechanisms, including photodegradation, thermal decomposition, mechanical wear, and hydrolysis. These release mechanisms may be especially relevant to nanocomposites that are likely to be subjected to weathering, including construction and infrastructural materials, sporting equipment, and materials that might potentially end up in landfills. This review pays particular attention to studies that shed light on specific release mechanisms and synergistic mechanistic relationships. The review concludes with a short section on knowledge gaps and future research needs.

  16. Magnetically anisotropic additive for scalable manufacturing of polymer nanocomposite: iron-coated carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yamamoto, Namiko; Manohara, Harish; Platzman, Ellen

    2016-02-01

    Novel nanoparticles additives for polymer nanocomposites were prepared by coating carbon nanotubes (CNTs) with ferromagnetic iron (Fe) layers, so that their micro-structures can be bulk-controlled by external magnetic field application. Application of magnetic fields is a promising, scalable method to deliver bulk amount of nanocomposites while maintaining organized nanoparticle assembly throughout the uncured polymer matrix. In this work, Fe layers (˜18 nm thick) were deposited on CNTs (˜38 nm diameter and ˜50 μm length) to form thin films with high aspect ratio, resulting in a dominance of shape anisotropy and thus high coercivity of ˜50-100 Oe. The Fe-coated CNTs were suspended in water and applied with a weak magnetic field of ˜75 G, and yet preliminary magnetic assembly was confirmed. Our results demonstrate that the fabricated Fe-coated CNTs are magnetically anisotropic and effectively respond to magnetic fields that are ˜103 times smaller than other existing work (˜105 G). We anticipate this work will pave the way for effective property enhancement and bulk application of CNT-polymer nanocomposites, through controlled micro-structure and scalable manufacturing.

  17. Effect of Nanoscale Fillers on the Local Mechanical Behavior of Polymer Nanocomposites

    DTIC Science & Technology

    2009-12-01

    carbon nanotubes pulled from a polymer matrix", Composites Science and Technology 64(15), pp. 2283-2289, 2004. 35. J. Gou, B. Minaie, B. Wang, Z. Liang...Science 31, pp. 225-236, 2004. 36. Y. Ganesan, J. Lou, "The mechanical characterization of carbon - nanotube -reinforced- polymer-matrix nanocomposites: An unfolding story of interface", JOM 61(1), pp. 32-37, 2009. 28 ...particles, and (b) the mechanical and interracial properties of individual vapor grown carbon nanofibers (VGCNFs) embedded in EPON epoxy.

  18. Temperature Dependence of Rheology and Polymer Diffusion in Silica/Polystyrene Nanocomposites

    NASA Astrophysics Data System (ADS)

    Tung, Wei-Shao; Clarke, Nigel; Composto, Russell; Meth, Jeffrey; Winey, Karen

    2015-03-01

    Time-temperature superposition using the WLF equation is well-established for both the zero shear viscosity and the polymer diffusion coefficient in homopolymer melts. This talk will present the temperature-dependence of polymer dynamics in polymer nanocomposites comprised of polystyrene and phenyl-capped silica nanoparticles (0 - 50 vol%). The WLF equation fits the temperature dependence of the tracer polymer diffusion coefficient and the fitting parameter (B/fo) decreases smoothly with nanoparticle concentration suggesting an increase in the thermal expansion coefficient for the free volume. The WLF equation also fits the temperature dependence of the zero shear viscosity from oscillatory shear experiments, although the fitting parameter (B/fo) increases substantially with nanoparticle concentration. This discrepancy between the diffusion and rheology will be discussed with respect to the reptation model, which predicts that the temperature dependence of polymer diffusion depends predominately on the temperature dependence of local viscosity, and the elastic response in nanocomposites. National Science Foundation DMR-12-10379.

  19. Release of engineered nanomaterials from polymer nanocomposites: diffusion, dissolution, and desorption.

    PubMed

    Duncan, Timothy V; Pillai, Karthik

    2015-01-14

    Polymer nanocomposites-polymer-based materials that incorporate filler elements possessing at least one dimension in the nanometer range-are increasingly being developed for commercial applications ranging from building infrastructure to food packaging to biomedical devices and implants. Despite a wide range of intended applications, it is also important to understand the potential for exposure to these nanofillers, which could be released during routine use or abuse of these materials, so it can be determined whether they pose a risk to human health or the environment. This article is the first in a series of two that review the state of the science regarding the release of engineered nanomaterials (ENMs) from polymer nanocomposites. Two ENM release paradigms are considered in this series: the release of ENMs via passive diffusion, desorption, and dissolution into external liquid media and release of ENMs assisted by matrix degradation. The present article focuses primarily on the first paradigm and includes (1) an overview of basic interactions between polymers and liquid environments and a brief summary of diffusion physics as they apply to polymeric materials; (2) a summary of both experimental and theoretical methods to assess contaminant release (including ENMs) from polymers by diffusion, dissolution, and desorption; and (3) a thorough, critical review of the associated body of peer-reviewed literature on ENM release by these mechanisms. A short outlook section on knowledge gaps and future research needs is also provided.

  20. An extended micromechanics method for probing interphase properties in polymer nanocomposites [An extended micromechanics method for overlapping geometries with application to polymer nanocomposites

    DOE PAGES

    Liu, Zeliang; Moore, John A.; Liu, Wing Kam

    2016-05-03

    Inclusions comprised on filler particles and interphase regions commonly form complex morphologies in polymer nanocomposites. Addressing these morphologies as systems of overlapping simple shapes allows for the study of dilute particles, clustered particles, and interacting interphases all in one general modeling framework. To account for the material properties in these overlapping geometries, weighted-mean and additive overlapping conditions are introduced and the corresponding inclusion-wise integral equations are formulated. An extended micromechanics method based on these overlapping conditions for linear elastic and viscoelastic heterogeneous material is then developed. An important feature of the proposed approach is that the effect of both themore » geometric overlapping (clustered particles) and physical overlapping (interacting interphases) on the effective properties can be distinguished. Lastly, we apply the extended micromechanics method to a viscoelastic polymer nanocomposite with interphase regions, and estimate the properties and thickness of the interphase region based on experimental data for carbon-black filled styrene butadiene rubbers.« less

  1. Recent progress on preparation and properties of nanocomposites from recycled polymers: a review.

    PubMed

    Zare, Yasser

    2013-03-01

    Currently, the growing consumption of polymer products creates the large quantities of waste materials resulting in public concern in the environment and people life. Nanotechnology is assumed the important technology in the current century. Recently, many researchers have tried to develop this new science for polymer recycling. In this article, the application of different nanofillers in the recycled polymers such as PET, PP, HDPE, PVC, etc. and the attributed composites and blends is studied. The morphological, mechanical, rheological and thermal properties of prepared nanocomposites as well as the future challenges are extensively discussed. The present article determines the current status of nanotechnology in the polymer recycling which guide the future studies in this attractive field. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Size-Dependent Particle Dynamics in Entangled Polymer Nanocomposites

    SciTech Connect

    Mangal, Rahul; Srivastava, Samanvaya; Narayanan, Suresh; Archer, Lynden A.

    2015-12-22

    Polymer-grafted nanoparticles with diameter d homogeneously dispersed in entangled polymer melts with varying random coil radius R0, but fixed entanglement mesh size ae, are used to study particle motions in entangled polymers. We focus on materials in the transition region between the continuum regime (d > R0), where the classical Stokes-Einstein (S-E) equation is known to describe polymer drag on particles, and the non-continuum regime (d < ae), in which several recent studies report faster diffusion of particles than expected from continuum S-E analysis, based on the bulk polymer viscosity. Specifically, we consider dynamics of particles with sizes d ≥ ae in entangled polymers with varying molecular weight Mw in order to investigate how the transition from non-continuum to continuum dynamics occur. We take advantage of favorable enthalpic interactions between SiO2 nanoparticles tethered with PEO molecules and entangled PMMA host polymers to create model nanoparticle-polymer composites, in which spherical nanoparticles are uniformly dispersed in entangled polymers. Investigation of the particle dynamics via X-ray photon correlation spectroscopy measurements reveal a transition from fast to slow particle motion as the PMMA molecular weight is increased beyond the entanglement threshold, with a much weaker Mw dependence for Mw>Me than expected from S-E analysis based on bulk viscosity of entangled PMMA melts. We rationalize these observations using a simple force balance analysis around particles and find that nanoparticle motion in entangled melts can be described using a variant of the S-E analysis in which motion of particles is assumed to only disturb sub-chain entangled host segments with sizes comparable to the particle diameter.

  3. Mechanochemical Strengthening of a Synthetic Polymer in Response to Typically Destructive Shear Forces

    DTIC Science & Technology

    2013-08-04

    and in bulk materials , and the resulting covalent polymer networks possess moduli that are orders-of- magnitude greater than those of the unactivated...polymers. These molecular-level responses and their impact on polymer properties have implications for the design of materials that, like...biological materials , actively remodel locally as a function of their physical environment. Mechanochemical strengthening of a synthetic polymer in response to

  4. PVC-PBMA nanocomposite polymer electrolytes for lithium battery applications

    NASA Astrophysics Data System (ADS)

    Arunkumar, R.; Rani, M. Usha; Babu, Ravishanker

    2017-05-01

    Polyvinyl chloride (PVC)-Poly (butyl methacrylate) (PBMA) composite polymer electrolytes with incorporation of different ratio of ZrO2 doped was prepared by solution casting technique. The ionic conductivity, dielectric behavior, ionic transference number and surface morphology of the composite polymer electrolytes were characterized by using ac impedance, dielectric, DC polarization method and SEM studies respectively. The best room temperature ionic conductivity (0.520mScm-1 at 303 K), high dielectric constant (27340 ± 10 at 50 Hz) and high pore size obtained for 10 wt% of ZrO2 doped composite polymer electrolytes. DC polarization method confirms the occurrences of conduction in composite PVC-PBMA blend polymer electrolytes predominantly due to ions.

  5. Dielectric dispersion and relaxations in (PVA-PEO)-ZnO polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Choudhary, Shobhna

    2017-10-01

    The organic-inorganic nanocomposite materials consisted of poly(vinyl alcohol) (PVA) and poly(ethylene oxide) (PEO) blend matrix (50/50 wt%) dispersed with zinc oxide (ZnO) nanoparticles have been prepared by the aqueous solution-cast method. The dielectric dispersion and relaxation processes in these polymer nanocomposite (PNC) films (i.e., (PVA-PEO)-x wt% ZnO; x = 0, 1, 3 or 5) have been investigated over the frequency range from 20 Hz to 1 MHz by employing the dielectric relaxation spectroscopy (DRS). Influence of ZnO contents on the complex dielectric permittivity, electrical conductivity, electric modulus and impedance properties of these PNC materials has been explored. The dielectric permittivity and the relaxation time values corresponding to polymers cooperative chain segmental motion significantly change with the variation of ZnO contents in the PVA-PEO blend matrix at ambient temperature. The temperature dependent relaxation times and dc conductivity values of (PVA-PEO)-3 wt% ZnO film have been investigated which obey the Arrhenius behaviour. The dielectric permittivity of the film as a function of temperature exhibits linear behaviour at radio frequencies and non-linear variation at lower audio frequencies. X-ray diffraction measurements confirm a huge decrease in crystalline phase of the polymer blend matrix on the addition of 1 wt% ZnO nanoparticles. These PNC materials have low values of dielectric permittivity and electrical conductivity which confirm their suitability as novel flexible-type polymer nanodielectric for the insulation in microelectronic devices, whereas the fast chain segmental dynamics and high amorphous phase reveal these materials as a potential candidate for the preparation of nanocomposite solid polymer electrolytes.

  6. Uniaxial deformation of nanorod filled polymer nanocomposites: a coarse-grained molecular dynamics simulation.

    PubMed

    Gao, Yangyang; Liu, Jun; Shen, Jianxiang; Zhang, Liqun; Guo, Zhanhu; Cao, Dapeng

    2014-08-14

    A coarse-grained molecular dynamics simulation was used to investigate the stress-strain behavior of nanorod-filled polymer composites. The effects of the interfacial interaction, aspect ratio of fillers, filler functionalization, chemical couplings between the polymer and the filler and the filler loading on the mechanical reinforcement were explored. The results indicate that there exists an optimal nanorod volume fraction for elastomer reinforcement. The strong polymer-nanorod interaction enhances the reinforcement of polymer nanocomposites. Meanwhile, it is found that nanorods with longer length and smaller diameter, and the chemical functionalization of nanorods can help realize the efficient interfacial stress transfer. And excessive chemical couplings between polymers and nanorods are harmful to mechanical properties. An upturn in the modulus at large deformation is observed in the Mooney-Rivlin plot, attributed to the limited chain extensibility. Particularly, the medium polymer-nanorod interfacial strength and low nanorod volume loading will lead to better dispersion of nanorods. It is suggested that the reinforcement mechanism comes from the nanorod alignment and bond orientation, as well as from the limited extensibility of chain bridges at large deformation. In addition, an optimal nanorod volume fraction can also be explained by the strong polymer-nanorod network. Compared to glassy systems, the mechanism for the significantly enhanced reinforcement of rubbery systems is also demonstrated. In short, our simulation study of nanorod-induced mechanical reinforcement will provide a basic understanding of polymer reinforcement.

  7. Screen printable flexible conductive nanocomposite polymer with applications to wearable sensors

    NASA Astrophysics Data System (ADS)

    Chung, D.; Khosla, A.; Gray, B. L.

    2014-04-01

    We have developed a conductive nanocomposite polymer that possesses both good conductivity and flexibility, and screen printed it onto fabric to realize wearable flexible electrodes and electronic routing. The conductive polymer consists of dispersed silver nanoparticles (90~210nm) in a screen printable plastisol polymer. The conductive polymer is conductive for weight-percentages above approximately 61 wt-% of Ag nanoparticles, and has a resistivity of 2.12×10-6 ohm·m at 70 wt-% of Ag nanoparticles. To test the screen printed conductive polymer's flexibility and its effect on conductivity, we measured the resistivity of the Ag-doped composite polymer at different bending angles (-90˚ ~ 90˚) with a 10° step angle at different wt-% of silver particles, and compared the results. We also tested washability of the screen printed conductive polymer as applied to fabric for long-term use in wearable sensors systems. We also used the screen printed Ag composite polymer to realize an example wearable system. Flexible wearable dry electrocardiogram (ECG) electrodes were developed and ECG signal was measured via the electrodes. The sensing ECG electrodes (3mm diameter circle) were chloridized to form Ag/AgCl electrodes. We measured an ECG signal using a simple right-leg driven ECG circuit and observed normal ECG signals even without application of electrolyte gel.

  8. Dispersion strategies and role of interfacial phenomena in dielectric polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Khodaparast, Payam

    Owing to unique characteristics of nanoparticles such as high surface to volume ratio, it is postulated that nanoparticle-modified polymers exhibit properties beyond those predicted by effective media theories. In the case of dielectric nanoparticles in a polymer, it is expected that dielectric properties of the nanocomposite are dominated by the expansive interface rather than anticipated by the inherent properties of individual components. An in-depth review of dielectric polymer nanocomposites shows conflicting trends where addition of nano-sized particles resulted in increase or decrease in dielectric properties. This contradictory behavior could mainly stem from 1- the state of dispersion of nanoparticles and 2-The unique nature of interface based on the particle-polymer system. The hypothesis of the proposed research is that the role of the interfacial region is not only influenced by its expansive nature but is also governed by their interaction at nanoscale regime. In order to achieve a high internal surface area, the first important challenge to address is controlling the state of dispersion and disaggregation of nanoparticles. Therefore the first goal of this research is studying the effectiveness of different processing methods in achieving uniform nanoscale dispersion in dielectric polymer nanocomposites. Silane functionalization of titania nanoparticles is investigated as one possible solution of better dispersion of titania in PVDF polymer where two coupling agents namely, aminopropyltriethoxy silane called as APS, and Nonafluorohexyltriethoxysilane called as FHES, are studied. FHES is shown to be more effective in reducing the average aggregate size of titania nanoparticles in PVDF matrix to below 100nm, whereas the average aggregate size in untreated and APS-functionalized TiO2/PVDF nanocomposite was approximately one to two orders of magnitude higher than that. Dielectric permittivity of FHES-functionalized TiO2/PVDF nanocomposite, showed

  9. HPLC analysis of synthetic polymers on short monolithic columns.

    PubMed

    Maksimova, Elena; Vlakh, Evgenia; Sinitsyna, Ekaterina; Tennikova, Tatiana

    2013-12-01

    Ultrashort monolithic columns (disks) were thoroughly studied as efficient stationary phases for precipitation-dissolution chromatography of synthetic polymers. Gradient elution mode was applied in all chromatographic runs. The mixtures of different flexible chain homopolymers, such as polystyrenes, poly(methyl methacrylates), and poly(tert-butylmethacrylates) were separated according to their molecular weights on both commercial poly(styrene-co-divinylbenzene) disks (12 id × 3 mm and 5 × 5 mm) and lab-made monolithic columns (4.6 id × 50 mm) filled with supports of different hydrophobicity. The experimental conditions were optimized to reach fast and highly efficient separation. It was observed that, similar to the separation of monoliths of other classes of (macro)molecules (proteins, DNA, oligonucleotides), the length of column did not affect the peak resolution. A comparison of the retention properties of the poly(styrene-co-divinylbenzene) disk-shaped monoliths with those based on poly(lauryl methacrylate-co-ethylene dimethacrylate), poly(butyl methacrylate-co-ethylene dimethacrylate), and poly(glycidyl methacrylate-co-ethylene dimethacrylate) supports demonstrated the obvious effect of surface chemistry on the resolution factor. Additionally, the results of the discussed chromatographic mode on the fast determination of the molecular weights of homopolymers used in this study were compared to those established by SEC on columns packed with sorbent beads of a similar nature to the monoliths. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Synthetic polymers and methods of making and using the same

    SciTech Connect

    Daily, Michael D.; Grate, Jay W.; Mo, Kai-For

    2016-06-14

    Monomer embodiments that can be used to make polymers, such as homopolymers, heteropolymers, and that can be used in particular embodiments to make sequence-defined polymers are described. Also described are methods of making polymers using such monomer embodiments. Methods of using the polymers also are described.

  11. Synthetic polymers and methods of making and using the same

    DOEpatents

    Grate, Jay W.; Mo, Kai-For; Daily, Michael D.

    2017-02-07

    Monomer embodiments that can be used to make polymers, such as homopolymers, heteropolymers, and that can be used in particular embodiments to make sequence-defined polymers are described. Also described are methods of making polymers using such monomer embodiments. Methods of using the polymers also are described.

  12. Poly(vinylidene fluoride) polymer based nanocomposites with enhanced energy density by filling with polyacrylate elastomers and BaTiO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Yu, Ke; Bai, Yuanyuan; Zhou, Yongcun; Niu, Yujuan; Wang, Hong

    2014-02-01

    Polyacrylate elastomers were introduced into poly(vinylidene fluoride) polymer-based nanocomposites filled with BaTiO3 nanoparticles and the three-phase nanocomposite films were prepared. The energy discharged of the nanocomposite with 3 vol. % polyacrylate elastomers is 8.8 J/cm3, approximately 11% higher compared to that of the nanocomposite without adding polyacrylate elastomers. Large elastic deformation of the polyacrylate elastomers increases Maxwell-Wagner-Sillars interfacial polarization and space charge polarization of the nanocomposites with the electric field increasing, which results in increased maximum polarization and energy discharged of the nanocomposites.

  13. Effect of heating rate on toxicity of pyrolysis gases from some synthetic polymers

    NASA Technical Reports Server (NTRS)

    Hilado, C. J.; Soriano, J. A.; Kosola, K. L.

    1977-01-01

    The effect of heating rate on the toxicity of the pyrolysis gases from some synthetic polymers was investigate, using a screening test method. The synthetic polymers were polyethylene, polystyrene, polymethyl methacrylate, polycarbonate, ABS, polyaryl sulfone, polyether sulfone, and polyphenylene sulfide. The toxicants from the sulfur-containing polymers appeared to act more rapidly than the toxicants from the other polymers. It is not known whether this effect is due primarily to differences in concentration or in the nature of the toxicants. The carbon monoxide concentrations found do not account for the observed results.

  14. Effect of heating rate on toxicity of pyrolysis gases from some synthetic polymers

    NASA Technical Reports Server (NTRS)

    Hilado, C. J.; Soriano, J. A.; Kosola, K. L.

    1977-01-01

    The effect of heating rate on the toxicity of the pyrolysis gases from some synthetic polymers was investigate, using a screening test method. The synthetic polymers were polyethylene, polystyrene, polymethyl methacrylate, polycarbonate, ABS, polyaryl sulfone, polyether sulfone, and polyphenylene sulfide. The toxicants from the sulfur-containing polymers appeared to act more rapidly than the toxicants from the other polymers. It is not known whether this effect is due primarily to differences in concentration or in the nature of the toxicants. The carbon monoxide concentrations found do not account for the observed results.

  15. Core-satellite Ag@BaTiO3 nanoassemblies for fabrication of polymer nanocomposites with high discharged energy density, high breakdown strength and low dielectric loss.

    PubMed

    Xie, Liyuan; Huang, Xingyi; Li, Bao-Wen; Zhi, Chunyi; Tanaka, Toshikatsu; Jiang, Pingkai

    2013-10-28

    Dielectric polymer nanocomposites with high dielectric constant have wide applications in high energy density electronic devices. The introduction of high dielectric constant ceramic nanoparticles into a polymer represents an important route to fabricate nanocomposites with high dielectric constant. However, the nanocomposites prepared by this method generally suffer from relatively low breakdown strength and high dielectric loss, which limit the further increase of energy density and energy efficiency of the nanocomposites. In this contribution, by using core-satellite structured ultra-small silver (Ag) decorated barium titanate (BT) nanoassemblies, we successfully fabricated high dielectric constant polymer nanocomposites with enhanced breakdown strength and lower dielectric loss in comparison with conventional polymer-ceramic particulate nanocomposites. The discharged energy density and energy efficiency are derived from the dielectric displacement-electric field loops of the polymer nanocomposites. It is found that, by using the core-satellite structured Ag@BT nanoassemblies as fillers, the polymer nanocomposites can not only have higher discharged energy density but also have high energy efficiency. The mechanism behind the improved electrical properties was attributed to the Coulomb blockade effect and the quantum confinement effect of the introduced ultra-small Ag nanoparticles. This study could serve as an inspiration to enhance the energy storage densities of dielectric polymer nanocomposites.

  16. Synthesis of vinyl polymer-silica colloidal nanocomposites prepared using commercial alcoholic silica sols.

    PubMed

    Percy, M J; Amalvy, J I; Randall, D P; Armes, S P; Greaves, S J; Watts, J F

    2004-03-16

    The surfactant-free synthesis of vinyl polymer-silica nanocomposite particles has been achieved in aqueous alcoholic media at ambient temperature in the absence of auxiliary comonomers. Styrene, methyl methacrylate, methyl acrylate, n-butyl acrylate, and 2-hydroxypropyl methacrylate were homopolymerized in turn in the presence of three commercially available ultrafine alcoholic silica sols. Stable colloidal dispersions with reasonably narrow size distributions were obtained, with silica contents of up to 58% by mass indicated by thermogravimetric analysis. Particle size distributions were assessed using both dynamic light scattering and disk centrifuge photosedimentometry. The former technique indicated that the particle size increased for the first 1-2 h at 25 degrees C and thereafter remained constant. Particle morphologies were studied using electron microscopy. Most of the colloidal nanocomposites comprised approximately spherical particles with relatively narrow size distributions, but in some cases more polydisperse or nonspherical particles were obtained. Selected acrylate-based nanocomposites were examined in terms of their film formation behavior. Scanning electron microscopy studies indicated relatively smooth films were obtained on drying at 20 degrees C, with complete loss of the original particle morphology. The optical clarity of solution-cast 10 microm nanocomposite films was assessed using visible absorption spectrophotometry, with 93-98% transmission being obtained from 400 to 800 nm; the effect of long-term immersion of such films in aqueous solutions was also examined. X-ray photoelectron spectroscopy studies indicated that the surface compositions of these nanocomposite particles are invariably silica-rich, which is consistent with their long-term colloidal stability and also with aqueous electrophoresis measurements. FT-IR studies suggested that in the case of the poly(methyl methacrylate)-silica nanocomposite particles, the carbonyl ester

  17. High-Z Nanoparticle/Polymer Nanocomposites for Gamma-Ray Scintillation Detectors

    NASA Astrophysics Data System (ADS)

    Liu, Chao

    An affordable and reliable solution for spectroscopic gamma-ray detection has long been sought after due to the needs from research, defense, and medical applications. Scintillators resolve gamma energy by proportionally converting a single high-energy photon into a number of photomultiplier-tube-detectable low-energy photons, which is considered a more affordable solution for general purposes compared to the delicate semiconductor detectors. An ideal scintillator should simultaneously exhibit the following characteristics: 1) high atomic number (Z) for high gamma stopping power and photoelectron production; 2) high light yield since the energy resolution is inversely proportional to the square root of light yield; 3) short emission decay lifetime; and 4) low cost and scalable production. However, commercial scintillators made from either inorganic single crystals or plastics fail to satisfy all requirements due to their intrinsic material properties and fabrication limitations. The concept of adding high-Z constituents into plastic scintillators to harness high Z, low cost, and fast emission in the resulting nanocomposite scintillators is not new in and of itself. Attempts have been made by adding organometallics, quantum dots, and scintillation nanocrystals into the plastic matrix. High-Z organometallics have long been used to improve the Z of plastic scintillators; however, their strong spin-orbit coupling effect entails careful triplet energy matching using expensive triplet emitters to avoid severe quenching of the light yield. On the other hand, reported quantum dot- and nanocrystal-polymer nanocomposites suffer from moderate Z and high optical loss due to aggregation and self-absorption at loadings higher than 10 wt%, limiting their potential for practical application. This dissertation strives to improve the performance of nanoparticle-based nanocomposite scintillators. One focus is to synthesize transparent nanocomposites with higher loadings of high

  18. Polymer based nanocomposites with nanofibers and exfoliated clay

    NASA Technical Reports Server (NTRS)

    Meador, Michael A.; Reneker, Darrell H.

    2005-01-01

    Polymer solutions, containing clay sheets, were electrospun into nanofibers and microfibers that contained clay sheets inside. Controllable removal of polymer by plasma etching from the surface of fibers revealed the arrangement of clay. The shape, flexibility, size distribution and arrangement of clay sheets were observed by transmission and scanning electron microscopy. The clay sheets were partially aligned in big fibers with normal direction of clay sheets perpendicular to fiber axis. Crumpling of clay sheets inside fibers was observed when the fiber diameter was comparable to the lateral size of clay sheets. Single sheets of clay were observed both by catching clay sheets dispersed in water with electrospun nanofiber mats and by the deliberate removal of most of the polymer in the fibers. Thin, flexible gas barrier films, that are reasonably strong, were assembled from clay sheets and polymer nanofibers. Structure of composite films was characterized with scanning electron microscopy. Continuous film of clay sheets were physically attached to the surface of fiber mats. Spincoating film of polymer and clay sheets was reinforced by electrospun fiber scaffold. Certain alignment of clay sheets was observed in the vicinity of fibers.

  19. Molecular dynamics simulations of polymer transport in nanocomposites

    NASA Astrophysics Data System (ADS)

    Desai, Tapan; Keblinski, Pawel; Kumar, Sanat K.

    2005-04-01

    Molecular dynamics simulations on the Kremer-Grest bead-spring model of polymer melts are used to study the effect of spherical nanoparticles on chain diffusion. We find that chain diffusivity is enhanced relative to its bulk value when polymer-particle interactions are repulsive and is reduced when polymer-particle interactions are strongly attractive. In both cases chain diffusivity assumes its bulk value when the chain center of mass is about one radius of gyration Rg away from the particle surface. This behavior echoes the behavior of polymer melts confined between two flat surfaces, except in the limit of severe confinement where the surface influence on polymer mobility is more pronounced for flat surfaces. A particularly interesting fact is that, even though chain motion is strongly speeded up in the presence of repulsive boundaries, this effect can be reversed by pinning one isolated monomer onto the surface. This result strongly stresses the importance of properly specifying boundary conditions when the near surface dynamics of chains are studied.

  20. Differential scanning calorimetry investigation on vinyl ester resin curing process for polymer nanocomposite fabrication.

    PubMed

    Guo, Zhanhu; Ng, Ho Wai; Yee, Gary L; Hahn, H Thomas

    2009-05-01

    Two different ceramic (cerium oxide and titanium oxide) nanoparticles were introduced into vinyl ester resin for nanocomposite fabrication. The curing process of the vinyl ester resin was investigated by a differential scanning calorimetery (DSC). The incorporation of nanoparticles in the resin affects the curing process due to the physicochemical interaction between the nanoparticles and the polymer matrix. The particle loading has a significant effect on the initial and peak curing temperatures, reaction heat and curing extent. The fully cured vinyl ester resin nanocomposites reinforced with cerium oxide nanoparticles were fabricated after a 24-hour room temperature curing and a one-hour postcuring at 85 degrees C. Particle functionalization favors the composite fabrication with a higher curing extent after room-temperature curing as compared to the as-received nanoparticle filled vinyl ester resin nanocomposites. The nanofiller materials were observed to significantly affect the curing process. In comparison to cerium oxide nanoparticles, titanium oxide nanoparticles prohibit the curing process with a much higher initiating curing temperatures. The fully cured nanocomposites reinforced with titanium oxide nanoparticles were fabricated by one-hour postcuring at 85 degrees C.

  1. Transparent Ultra-High-Loading Quantum Dot/Polymer Nanocomposite Monolith for Gamma Scintillation.

    PubMed

    Liu, Chao; Li, Zhou; Hajagos, Tibor Jacob; Kishpaugh, David; Chen, Dustin Yuan; Pei, Qibing

    2017-06-27

    Spectroscopic gamma-photon detection has widespread applications for research, defense, and medical purposes. However, current commercial detectors are either prohibitively expensive for wide deployment or incapable of producing the characteristic gamma photopeak. Here we report the synthesis of transparent, ultra-high-loading (up to 60 wt %) CdxZn1-xS/ZnS core/shell quantum dot/polymer nanocomposite monoliths for gamma scintillation by in situ copolymerization of the partially methacrylate-functionalized quantum dots in a monomer solution. The efficient Förster resonance energy transfer of the high-atomic-number quantum dots to lower-band-gap organic dyes enables the extraction of quantum-dot-borne excitons for photon production, resolving the problem of severe light yield deterioration found in previous nanoparticle-loaded scintillators. As a result, the nanocomposite scintillator exhibited simultaneous improvements in both light yield (visible photons produced per MeV of gamma-photon energy) and gamma attenuation. With these enhancements, a 662 keV Cs-137 gamma photopeak with 9.8% resolution has been detected using a 60 wt % quantum-dot nanocomposite scintillator, demonstrating the potential of such a nanocomposite system in the development of high-performance low-cost spectroscopic gamma detectors.

  2. Linear and Nonlinear Rheology Combined with Dielectric Spectroscopy of Hybrid Polymer Nanocomposites for Semiconductive Applications.

    PubMed

    Kádár, Roland; Abbasi, Mahdi; Figuli, Roxana; Rigdahl, Mikael; Wilhelm, Manfred

    2017-01-24

    The linear and nonlinear oscillatory shear, extensional and combined rheology-dielectric spectroscopy of hybrid polymer nanocomposites for semiconductive applications were investigated in this study. The main focus was the influence of processing conditions on percolated poly(ethylene-butyl acrylate) (EBA) nanocomposite hybrids containing graphite nanoplatelets (GnP) and carbon black (CB). The rheological response of the samples was interpreted in terms of dispersion properties, filler distortion from processing, filler percolation, as well as the filler orientation and distribution dynamics inside the matrix. Evidence of the influence of dispersion properties was found in linear viscoelastic dynamic frequency sweeps, while the percolation of the nanocomposites was detected in nonlinearities developed in dynamic strain sweeps. Using extensional rheology, hybrid samples with better dispersion properties lead to a more pronounced strain hardening behavior, while samples with a higher volume percentage of fillers caused a drastic reduction in strain hardening. The rheo-dielectric time-dependent response showed that in the case of nanocomposites containing only GnP, the orientation dynamics leads to non-conductive samples. However, in the case of hybrids, the orientation of the GnP could be offset by the dispersing of the CB to bridge the nanoplatelets. The results were interpreted in the framework of a dual PE-BA model, where the fillers would be concentrated mainly in the BA regions. Furthermore, better dispersed hybrids obtained using mixing screws at the expense of filler distortion via extrusion processing history were emphasized through the rheo-dielectric tests.

  3. Highly Stretchable and Highly Resilient Polymer-Clay Nanocomposite Hydrogels with Low Hysteresis.

    PubMed

    Su, Xing; Mahalingam, Suntharavathanan; Edirisinghe, Mohan; Chen, Biqiong

    2017-07-12

    Highly stretchable and highly resilient polymer-clay nanocomposite hydrogels were synthesized by in situ polymerization of acrylamide in the presence of pristine montmorillonite (MMT) or chitosan-treated MMT nanoplatelets at an elevated temperature. Both nanocomposite hydrogels can be stretched to a strain of no less than 1290%. The treatment of clay with chitosan improves the tensile strength, elongation at break, and energy at break of the nanocomposite hydrogel by 237%, 102%, and 389%, respectively, due to the strong chitosan-MMT electrostatic interaction and the grafting of polyacrylamide onto chitosan chains. Both hydrogels display excellent resilience with low hysteresis; with a maximum tensile strain of 50%, ultralow hysteresis is found, while, with a maximum strain of 500%, both hydrogels fully recover their original state in just 1 min. The superb resilience of the nanocomposite hydrogels is attributed to the strong interactions within the hydrogels brought by chain branching, multiple hydrogen bonding, covalent bonding, and/or electrostatic force. The hydrogels can be fabricated into different shapes and forms, including microfibers spun using pressurized gyration, which may find a variety of potential applications in particular in healthcare.

  4. Linear and Nonlinear Rheology Combined with Dielectric Spectroscopy of Hybrid Polymer Nanocomposites for Semiconductive Applications

    PubMed Central

    Kádár, Roland; Abbasi, Mahdi; Figuli, Roxana; Rigdahl, Mikael; Wilhelm, Manfred

    2017-01-01

    The linear and nonlinear oscillatory shear, extensional and combined rheology-dielectric spectroscopy of hybrid polymer nanocomposites for semiconductive applications were investigated in this study. The main focus was the influence of processing conditions on percolated poly(ethylene-butyl acrylate) (EBA) nanocomposite hybrids containing graphite nanoplatelets (GnP) and carbon black (CB). The rheological response of the samples was interpreted in terms of dispersion properties, filler distortion from processing, filler percolation, as well as the filler orientation and distribution dynamics inside the matrix. Evidence of the influence of dispersion properties was found in linear viscoelastic dynamic frequency sweeps, while the percolation of the nanocomposites was detected in nonlinearities developed in dynamic strain sweeps. Using extensional rheology, hybrid samples with better dispersion properties lead to a more pronounced strain hardening behavior, while samples with a higher volume percentage of fillers caused a drastic reduction in strain hardening. The rheo-dielectric time-dependent response showed that in the case of nanocomposites containing only GnP, the orientation dynamics leads to non-conductive samples. However, in the case of hybrids, the orientation of the GnP could be offset by the dispersing of the CB to bridge the nanoplatelets. The results were interpreted in the framework of a dual PE-BA model, where the fillers would be concentrated mainly in the BA regions. Furthermore, better dispersed hybrids obtained using mixing screws at the expense of filler distortion via extrusion processing history were emphasized through the rheo-dielectric tests. PMID:28336857

  5. UV surface modification of a new nanocomposite polymer to improve cytocompatibility.

    PubMed

    Olbrich, Michael; Punshon, Geoffrey; Frischauf, Irene; Salacinski, Henryk J; Rebollar, Esther; Romanin, Christoph; Seifalian, Alexander M; Heitz, Johannes

    2007-01-01

    A novel modified nanocomposite was studied for the adhesion and proliferation of the human umbilical vein endothelial cell (HUVEC) line EA.hy926. The nanocomposite under investigation was poly(carbonate-urea)urethane with silsesquioxane nano-cages, here in the form of a mixture of two polyhedral oligomeric silsesquioxanes. The nanocomposite surfaces were exposed to ultraviolet (UV) light of a Xe(*)(2)-excimer lamp at a wavelength of 172 nm in an ammonia atmosphere. The effects of the irradiation were characterized by atomic force and scanning electron microscopy (AFM, SEM), X-ray photo-electron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) using an attenuated total reflection (ATR) device and measurements of advancing water contact angle (CA). The irradiation resulted in the introduction of new hydrophilic N- and O-containing groups into the surface, which was initially amphiphilic, while surface morphology remained mainly unchanged. Slight chemical changes were also observed for the silsesquioxane nano-cages at the surface. Onto the untreated and irradiated samples HUVECs were seeded and grown for various durations in culture. Standard tissue-culture polystyrene (PS) was employed as a positive control to check the efficiency of the cell-culture methods. Viability and proliferation of the cells were then assessed using a non-radioactive assay. Compared to the untreated nanocomposite polymer, irradiation times of at least 5 min resulted in a significantly increased cell proliferation between 3 and 8 days after seeding with the HUVEC line EA.hy926.

  6. Tuning Glass Transition in Polymer Nanocomposites with Functionalized Cellulose Nanocrystals through Nanoconfinement.

    PubMed

    Qin, Xin; Xia, Wenjie; Sinko, Robert; Keten, Sinan

    2015-10-14

    Cellulose nanocrystals (CNCs) exhibit impressive interfacial and mechanical properties that make them promising candidates to be used as fillers within nanocomposites. While glass-transition temperature (Tg) is a common metric for describing thermomechanical properties, its prediction is extremely difficult as it depends on filler surface chemistry, volume fraction, and size. Here, taking CNC-reinforced poly(methyl-methacrylate) (PMMA) nanocomposites as a relevant model system, we present a multiscale analysis that combines atomistic molecular dynamics (MD) surface energy calculations with coarse-grained (CG) simulations of relaxation dynamics near filler-polymer interfaces to predict composite properties. We discover that increasing the volume fraction of CNCs results in nanoconfinement effects that lead to an appreciation of the composite Tg provided that strong interfacial interactions are achieved, as in the case of TEMPO-mediated surface modifications that promote hydrogen bonding. The upper and lower bounds of shifts in Tg are predicted by fully accounting for nanoconfinement and interfacial properties, providing new insight into tuning these aspects in nanocomposite design. Our multiscale, materials-by-design framework is validated by recent experiments and breaks new ground in predicting, without any empirical parameters, key structure-property relationships for nanocomposites.

  7. Polymer nanocomposite nanomechanical cantilever sensors: material characterization, device development and application in explosive vapour detection

    NASA Astrophysics Data System (ADS)

    Seena, V.; Fernandes, Avil; Pant, Prita; Mukherji, Soumyo; Ramgopal Rao, V.

    2011-07-01

    This paper reports an optimized and highly sensitive piezoresistive SU-8 nanocomposite microcantilever sensor and its application for detection of explosives in vapour phase. The optimization has been in improving its electrical, mechanical and transduction characteristics. We have achieved a better dispersion of carbon black (CB) in the SU-8/CB nanocomposite piezoresistor and arrived at an optimal range of 8-9 vol% CB concentration by performing a systematic mechanical and electrical characterization of polymer nanocomposites. Mechanical characterization of SU-8/CB nanocomposite thin films was performed using the nanoindentation technique with an appropriate substrate effect analysis. Piezoresistive microcantilevers having an optimum carbon black concentration were fabricated using a design aimed at surface stress measurements with reduced fabrication process complexity. The optimal range of 8-9 vol% CB concentration has resulted in an improved sensitivity, low device variability and low noise level. The resonant frequency and spring constant of the microcantilever were found to be 22 kHz and 0.4 N m - 1 respectively. The devices exhibited a surface stress sensitivity of 7.6 ppm (mN m - 1) - 1 and the noise characterization results support their suitability for biochemical sensing applications. This paper also reports the ability of the sensor in detecting TNT vapour concentration down to less than six parts per billion with a sensitivity of 1 mV/ppb.

  8. Polymer nanocomposite nanomechanical cantilever sensors: material characterization, device development and application in explosive vapour detection.

    PubMed

    Seena, V; Fernandes, Avil; Pant, Prita; Mukherji, Soumyo; Rao, V Ramgopal

    2011-07-22

    This paper reports an optimized and highly sensitive piezoresistive SU-8 nanocomposite microcantilever sensor and its application for detection of explosives in vapour phase. The optimization has been in improving its electrical, mechanical and transduction characteristics. We have achieved a better dispersion of carbon black (CB) in the SU-8/CB nanocomposite piezoresistor and arrived at an optimal range of 8-9 vol% CB concentration by performing a systematic mechanical and electrical characterization of polymer nanocomposites. Mechanical characterization of SU-8/CB nanocomposite thin films was performed using the nanoindentation technique with an appropriate substrate effect analysis. Piezoresistive microcantilevers having an optimum carbon black concentration were fabricated using a design aimed at surface stress measurements with reduced fabrication process complexity. The optimal range of 8-9 vol% CB concentration has resulted in an improved sensitivity, low device variability and low noise level. The resonant frequency and spring constant of the microcantilever were found to be 22 kHz and 0.4 N m(-1) respectively. The devices exhibited a surface stress sensitivity of 7.6 ppm (mN m(-1))(-1) and the noise characterization results support their suitability for biochemical sensing applications. This paper also reports the ability of the sensor in detecting TNT vapour concentration down to less than six parts per billion with a sensitivity of 1 mV/ppb.

  9. Development of biodegradable metaloxide/polymer nanocomposite films based on poly-ε-caprolactone and terephthalic acid.

    PubMed

    Varaprasad, Kokkarachedu; Pariguana, Manuel; Raghavendra, Gownolla Malegowd; Jayaramudu, Tippabattini; Sadiku, Emmanuel Rotimi

    2017-01-01

    The present investigation describes the development of metal-oxide polymer nanocomposite films from biodegradable poly-ε-caprolactone, disposed poly(ethylene terephthalate) oil bottles monomer and zinc oxide-copper oxide nanoparticles. The terephthalic acid and zinc oxide-copper oxide nanoparticles were synthesized by using a temperature-dependent precipitation technique and double precipitation method, respectively. The terephthalic acid synthesized was confirmed by FTIR analysis and furthermore, it was characterized by thermal analysis. The as-prepared CuO-ZnO nanoparticles structure was confirmed by XRD analysis and its morphology was analyzed by SEM/EDS and TEM. Furthermore, the metal-oxide polymer nanocomposite films have excellent mechanical properties, with tensile strength and modulus better than pure films. The metal-oxide polymer nanocomposite films that were successfully developed show a relatively brighter colour when compared to CuO film. These new metal-oxide polymer nanocomposite films can replace many non-degradable plastics. The new metal-oxide polymer nanocomposite films developed are envisaged to be suitable for use in industrial and domestic packaging applications.

  10. Carbon-nanotube-polymer nanocomposites for field-emission cathodes.

    PubMed

    Connolly, Thomas; Smith, Richard C; Hernandez, Yenny; Gun'ko, Yurii; Coleman, Jonathan N; Carey, J David

    2009-04-01

    The electron field-emission (FE) characteristics of functionalized single-walled carbon-nanotube (CNT)-polymer composites produced by solution processing are reported. It is shown that excellent electron emission can be obtained by using as little as 0.7% volume fraction of nanotubes in the composite. Furthermore by tailoring the nanotube concentration and type of polymer, improvements in the charge transfer through the composite can be obtained. The synthesis of well-dispersed randomly oriented nanotube-polymer composites by solution processing allows the development of CNT-based large area cathodes produced using a scalable technology. The relative insensitivity of the cathode's FE characteristics to the electrical conductivity of the composite is also discussed.

  11. Synthesis of Silver Polymer Nanocomposites and Their Antibacterial Activity

    NASA Astrophysics Data System (ADS)

    Gavade, Chaitali; Shah, Sunil; Singh, N. L.

    2011-07-01

    PVA (Polyvinyl Alcohol) silver nanocomposites of different sizes were prepared by chemical reduction method. Silver nitrate was taken as the metal precursor and amine hydrazine as a reducing agent. The formation of the silver nanoparticles was noticed using UV- visible absorption spectroscopy. The UV-visible spectroscopy revealed the formation of silver nanoparticles by exhibiting the surface plasmon resonance. The bactericidal activity due to silver release from the surface was determined by the modification of conventional diffusion method. Salmonella typhimurium, Serratia sps and Shigella sps were used as test bacteria which are gram-negative type bacteria. Effect of the different sizes of silver nano particles on antibacterial efficiency was discussed. Zones of inhibition were measured after 24 hours of incubation at 37 °C which gave 20 mm radius for high concentration of silver nanoparticles.

  12. Investigation of the adhesion properties of direct 3D printing of polymers and nanocomposites on textiles: Effect of FDM printing process parameters

    NASA Astrophysics Data System (ADS)

    Hashemi Sanatgar, Razieh; Campagne, Christine; Nierstrasz, Vincent

    2017-05-01

    In this paper, 3D printing as a novel printing process was considered for deposition of polymers on synthetic fabrics to introduce more flexible, resource-efficient and cost effective textile functionalization processes than conventional printing process like screen and inkjet printing. The aim is to develop an integrated or tailored production process for smart and functional textiles which avoid unnecessary use of water, energy, chemicals and minimize the waste to improve ecological footprint and productivity. Adhesion of polymer and nanocomposite layers which were 3D printed directly onto the textile fabrics using fused deposition modeling (FDM) technique was investigated. Different variables which may affect the adhesion properties including 3D printing process parameters, fabric type and filler type incorporated in polymer were considered. A rectangular shape according to the peeling standard was designed as 3D computer-aided design (CAD) to find out the effect of the different variables. The polymers were printed in different series of experimental design: nylon on polyamide 66 (PA66) fabrics, polylactic acid (PLA) on PA66 fabric, PLA on PLA fabric, and finally nanosize carbon black/PLA (CB/PLA) and multi-wall carbon nanotubes/PLA (CNT/PLA) nanocomposites on PLA fabrics. The adhesion forces were quantified using the innovative sample preparing method combining with the peeling standard method. Results showed that different variables of 3D printing process like extruder temperature, platform temperature and printing speed can have significant effect on adhesion force of polymers to fabrics while direct 3D printing. A model was proposed specifically for deposition of a commercial 3D printer Nylon filament on PA66 fabrics. In the following, among the printed polymers, PLA and its composites had high adhesion force to PLA fabrics.

  13. A simple two-step method to fabricate highly transparent ITO/polymer nanocomposite films

    NASA Astrophysics Data System (ADS)

    Liu, Haitao; Zeng, Xiaofei; Kong, Xiangrong; Bian, Shuguang; Chen, Jianfeng

    2012-09-01

    Transparent functional indium tin oxide (ITO)/polymer nanocomposite films were fabricated via a simple approach with two steps. Firstly, the functional monodisperse ITO nanoparticles were synthesized via a facile nonaqueous solvothermal method using bifunctional chemical agent (N-methyl-pyrrolidone, NMP) as the reaction solvent and surface modifier. Secondly, the ITO/acrylics polyurethane (PUA) nanocomposite films were fabricated by a simple sol-solution mixing method without any further surface modification step as often employed traditionally. Flower-like ITO nanoclusters with about 45 nm in diameter were mono-dispersed in ethyl acetate and each nanocluster was assembled by nearly spherical nanoparticles with primary size of 7-9 nm in diameter. The ITO nanoclusters exhibited an excellent dispersibility in polymer matrix of PUA, remaining their original size without any further agglomeration. When the loading content of ITO nanoclusters reached to 5 wt%, the transparent functional nanocomposite film featured a high transparency more than 85% in the visible light region (at 550 nm), meanwhile cutting off near-infrared radiation about 50% at 1500 nm and blocking UV ray about 45% at 350 nm. It could be potential for transparent functional coating materials applications.

  14. RIR-MAPLE deposition of conjugated polymers and hybrid nanocomposites for application to optoelectronic devices

    SciTech Connect

    Stiff-Roberts, Adrienne D.; Pate, Ryan; McCormick, Ryan; Lantz, Kevin R.

    2012-07-30

    Resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) is a variation of pulsed laser deposition that is useful for organic-based thin films because it reduces material degradation by selective absorption of infrared radiation in the host matrix. A unique emulsion-based RIR-MAPLE approach has been developed that reduces substrate exposure to solvents and provides controlled and repeatable organic thin film deposition. In order to establish emulsion-based RIR-MAPLE as a preferred deposition technique for conjugated polymer or hybrid nanocomposite optoelectronic devices, studies have been conducted to demonstrate the value added by the approach in comparison to traditional solution-based deposition techniques, and this work will be reviewed. The control of hybrid nanocomposite thin film deposition, and the photoconductivity in such materials deposited using emulsion-based RIR-MAPLE, will also be reviewed. The overall result of these studies is the demonstration of emulsion-based RIR-MAPLE as a viable option for the fabrication of conjugated polymer and hybrid nanocomposite optoelectronic devices that could yield improved device performance.

  15. Application of polymer nanocomposites in the nanomedicine landscape: envisaging strategies to combat implant associated infections.

    PubMed

    Dwivedi, Poushpi; Narvi, Shahid S; Tewari, Ravi P

    2013-12-16

    This review article presents an overview of the potential biomedical application of polymer nanocomposites arising from different chemistries, compositions, and constructions. The interaction between the chosen matrix and the filler is of critical importance. The existing polymer used in the biomedical arena includes aliphatic polyesters such as polylactide (PLA), poly(ε-caprolactone) (PCL), poly(p-dioxanone) (PPDO), poly(butylenes succinate) (PBS), poly(hydroxyalkanoate)s, and natural biopolymers such as starch, cellulose, chitin, chitosan, lignin, and proteins. The nanosized fillers utilized to fabricate the nanocomposites are inorganic, organic, and metal particles such as clays, magnetites, hydroxyapatite, nanotubes chitin whiskers, lignin, cellulose, Au, Ag, Cu, etc. These nanomaterials are taking root in a variety of diverse healthcare applications in the sector of nanomedicine including the domain of medical implants and devices. Despite sterilization and aseptic procedures the use of these biomedical devices and prosthesis to improve the patient's 'quality of life' is facing a major impediment because of bacterial colonization causing nosocomial infection, together with the multi-drug-resistant 'super-bugs' posing a serious threat to its utility. This paper discusses the current efforts and key research challenges in the development of self-sterilizing nanocomposite biomaterials for potential application in this area.

  16. Temperature-responsive polymer-gold nanocomposites as intelligent therapeutic systems.

    PubMed

    Owens, Donald E; Eby, Jackson K; Jian, Yicun; Peppas, Nicholas A

    2007-12-01

    The objective of this study was to synthesize and characterize a thermally responsive polymer-metal nanocomposite system comprised of a solid gold nanoparticle core and thermally responsive interpenetrating polymer network (IPN) shell, which was surface functionalized or PEGylated with a covalently bound linear poly(ethylene glycol) chain layer. Gold nanoparticles (50 nm diameter) were prepared using standard gold chloride and citrate reduction method. These particles were then encapsulated inside of a polyacrylamide (PAAm)/poly(acrylic acid) (PAA) IPN shell via an in situ inverse emulsion polymerization. The surface of the nanocomposite system was then PEGylated via covalent grafting of a linear methoxy-PEG-N-hydroxysuccinimide (M.W. 3400) to the primary amine groups of the PAAm network. Scanning and transmission electron microscopy were used to confirm the successful synthesis and encapsulation of gold nanoparticles within the IPN shell. Dynamic light scattering was used to examine the temperature swelling response of the IPN particles. Zeta-potential analysis was used to confirm the successful PEGylation of the final nanocomposite system.

  17. Structural and Dielectric Properties of Ionic Liquid Doped Metal Organic Framework based Polymer Electrolyte Nanocomposites

    NASA Astrophysics Data System (ADS)

    Dutta, Rituraj; Kumar, Ashok

    2016-10-01

    Metal Organic Frameworks (MOFs) are mesoporous materials that can be treated as potential hosts for trapping guest molecules in their pores. Ion conduction and phase behavior dynamics of Ionic Liquids (ILs) can be controlled by tunable interactions of MOFs with the ILs. MOFs incorporated with ionic liquid can be dispersed in the polymers to synthesize polymer electrolyte nanocomposites with high ionic conductivity, electrochemical and thermal stability for applications in energy storage and conversion devices such as rechargeable Li-ion batteries. In the present work we have synthesized Cu-based MOF [Cu3(l,3,5-benzene tricarboxylate)2(H2O)] incorporated with the ionic liquid 1-Butyl-3-methylimidazolium bromide at different weight ratios of MOF and IL. The synthesized MOF-IL composites are dispersed in Poly (ethylene oxide) (PEO). Frequency dependent behavior of permittivity and dielectric loss of the nanocomposites depict the non-Debye dielectric relaxation mechanism. The room temperature Nyquist plots reveal decreasing bulk resistance upto 189 Ω with optimum ionic conductivity of 1.3×10-3S cm-1at maximum doping concentration of IL in the nanocomposite system.

  18. Multi-functional particle assemblies in polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Jiao, Yang

    Self-assembly into ordered and equilibrium configurations underlie the microphase separation of block copolymers, protein folding and anisotropic aggregation of functionalized nanoparticles. In this project, we explored the assembly of polymer-grafted magnetic nanoparticles in solution and bulk states to combine various properties, such as ionic conductivity, mechanical reinforcement and responsiveness to external flows, within the same sample. The multi-functionality of iron oxide nanoparticles in polymer media is achieved using bottom-up approaches. Starting from the particle core synthesis, many layers of functionalities are added on magnetite (Fe3O4) nanoparticles by i) grafting polystyrene chains at different densities, lengths and elasticity; by ii) functionalizing particles with ionomers; and by iii) attaching charged diblock copolymers onto particles. In these three complex systems, particle nanostructures are investigated to explain the role of interactions between particle-particle, polymer-particle and polymer-polymer. We found that polystyrene-grafted Fe3O4 nanoparticles can form strings, spherical clusters and dispersed structures in polymer matrices by tuning the polymer graft density and grafted chain length. This structural transition has been explained through chain interactions and short-range dipolar interactions. We showed that chain conformation (radius of gyration) interestingly is not influenced within different dispersion states. Small-angle x-ray and neutron scattering results reveal that matrix chains do not govern the formation of strings, but have a significant impact on the size and internal structure of aggregated particles. Our findings showed that spherical aggregates of nanoparticles with low polymer graft densities are similar to interpenetrating networks in which free matrix chains bridge the fractals of particles and control the cluster density. Further, the mechanical properties of these different composite structures under

  19. Structural characterization of synthetic polymers using thermal-assisted atmospheric pressure glow discharge mass spectrometry.

    PubMed

    Zhang, Ning; Zhou, Yueming; Zhen, Cheng; Li, Yafeng; Xiong, Caiqiao; Wang, Jiyun; Li, Huayi; Nie, Zongxiu

    2012-11-07

    With the development of material science and the practical needs of the polymer industry, rapid characterization of synthetic polymers using mass spectrometry is of sustainable interest. Herein a new method for characterizing synthetic polymers using thermal-assisted atmospheric pressure glow discharge mass spectrometry (TA-APGD-MS) is established. After illustration of the mechanism of ion formation, typical polymer samples such as polystyrene (PS), polyoxymethylene (POM) and poly (butanediol succinate) (PBS) were directly characterized at the molecular level using TA-APGD-MS. The thermal degradation products of synthetic polymers including monomer units and/or other fragments were rapidly detected by tandem mass spectrometry, providing rich information about the chemical composition for the structural characterization of homo- and co-polymers. The result suggests that TA-APGD-MS allows direct and rapid analysis of both synthetic homo-polymers and co-polymers under ambient conditions without any sample pretreatment. This method features high throughput, high sensitivity and rich information, showing promising applications in polymer science.

  20. Giant Energy Density and Improved Discharge Efficiency of Solution-Processed Polymer Nanocomposites for Dielectric Energy Storage.

    PubMed

    Zhang, Xin; Shen, Yang; Xu, Ben; Zhang, Qinghua; Gu, Lin; Jiang, Jianyong; Ma, Jing; Lin, Yuanhua; Nan, Ce-Wen

    2016-03-09

    Large-aspect-ratio composite nanofibers with interior hierarchical interfaces are employed to break the adverse coupling of electric displacement and breakdown strength in flexible poly(vinylidene fluoride-hexafluoropropylene) nanocomposite films, a small loading of 3 vol% BaTiO3@TiO2 nanofibers gives rise to the highestenergy density (≈31.2 J cm(-3)) ever achieved in polymer nanocomposites dielectrics.

  1. Design and evaluation of a gastroretentive drug delivery system for metformin HCl using synthetic and semi-synthetic polymers.

    PubMed

    Meka, Venkata Srikanth; Gorajana, Adinaravyana; Dharmanlingam, Senthil Rajan; Kolapalli, Venkata Ramana Murthy

    2013-12-01

    The aim of the present research was to prepare and evaluate a gastroretentive drug delivery system for metformin HCl, using synthetic and semi-synthetic polymers. The floating approach was applied for preparing gastroretentive tablets (GRT) and these tablets were manufactured by the direct compression method. The drug delivery system comprises of synthetic and semi-synthetic polymers such as polyethylene oxide and Carboxymethyl ethyl cellulose (CMEC) as release-retarding polymers. GRT were evaluated for physico-chemical properties like weight variation, hardness, assay friability, in vitro floating behaviour, swelling studies, in vitro dissolution studies and rate order kinetics. Based upon the drug release and floating properties, two formulations (MP04 & MC03) were selected as optimized formulations. The optimized formulations MP04 and MC03 followed zero order rate kinetics, with non-Fickian diffusion and first order rate kinetics with erosion mechanism, respectively. The optimized formulation was characterised with FTIR studies and it was observed that there was no interaction between the drug and polymers.

  2. Glass transition and relaxation processes of nanocomposite polymer electrolytes.

    PubMed

    Money, Benson K; Hariharan, K; Swenson, Jan

    2012-07-05

    This study focus on the effect of δ-Al(2)O(3) nanofillers on the dc-conductivity, glass transition, and dielectric relaxations in the polymer electrolyte (PEO)(4):LiClO(4). The results show that there are three dielectric relaxation processes, α, β, and γ, in the systems, although the structural α-relaxation is hidden in the strong conductivity contribution and could therefore not be directly observed. However, by comparing an enhanced dc-conductivity, by approximately 2 orders of magnitude with 4 wt % δ-Al(2)O(3) added, with a decrease in calorimetric glass transition temperature, we are able to conclude that the dc-conductivity is directly coupled to the hidden α-relaxation, even in the presence of nanofillers (at least in the case of δ-Al(2)O(3) nanofillers at concentrations up to 4 wt %). This filler induced speeding up of the segmental polymer dynamics, i.e., the α-relaxation, can be explained by the nonattractive nature of the polymer-filler interactions, which enhance the "free volume" and mobility of polymer segments in the vicinity of filler surfaces.

  3. Rouse Mode Analysis of Chain Relaxation in Polymer Nanocomposites

    PubMed Central

    Kalathi, Jagannathan T.; Rubinstein, Michael; Grest, Gary S.

    2016-01-01

    Large-scale Molecular Dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. We examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, as in the case of a polymer-solvent system. However, for NPs larger than half the entanglement mesh size, effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Thus, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect. PMID:25939276

  4. Unraveling the Mechanism of Nanoscale Mechanical Reinforcement in Glassy Polymer Nanocomposites

    SciTech Connect

    Cheng, Shiwang; Bocharova, Vera; Belianinov, Alex; Xiong, Shaomin; Kisliuk, Alexander; Somnath, Suhas; Holt, Adam P.; Ovchinnikova, Olga S.; Jesse, Stephen; Martin, Halie J.; Etampawala, Thusitha N.; Dadmun, Mark D.; Sokolov, Alexei P.

    2016-05-20

    The mechanical reinforcement of polymer nanocomposites (PNCs) above the glass transition temperature, Tg, has been extensively researched. However, not much is known about the origin of this effect below Tg. In this paper, we unravel the mechanism of PNC reinforcement within the glassy state by directly probing nanoscale mechanical properties with atomic force microscopy and macroscopic properties with Brillouin light scattering. Our results unambiguously show that the "glassy" Young's modulus in the interfacial polymer layer of PNCs is two-times higher than in the bulk polymer, which results in significant reinforcement below Tg. We ascribe this phenomenon to a high stretching of the chains within the interfacial layer. Since the interfacial chain packing is essentially temperature independent, these findings provide a new insight into the mechanical reinforcement of PNCs also above Tg.

  5. How the flow affects the phase behaviour and microstructure of polymer nanocomposites

    SciTech Connect

    Stephanou, Pavlos S.

    2015-02-14

    We address the issue of flow effects on the phase behaviour of polymer nanocomposite melts by making use of a recently reported Hamiltonian set of evolution equations developed on principles of non-equilibrium thermodynamics. To this end, we calculate the spinodal curve, by computing values for the nanoparticle radius as a function of the polymer radius-of-gyration for which the second derivative of the generalized free energy of the system becomes zero. Under equilibrium conditions, we recover the phase diagram predicted by Mackay et al. [Science 311, 1740 (2006)]. Under non-equilibrium conditions, we account for the extra terms in the free energy due to changes in the conformations of polymer chains by the shear flow. Overall, our model predicts that flow enhances miscibility, since the corresponding miscibility window opens up for non-zero shear rate values.

  6. Unraveling the Mechanism of Nanoscale Mechanical Reinforcement in Glassy Polymer Nanocomposites

    SciTech Connect

    Cheng, Shiwang; Bocharova, Vera; Belianinov, Alex; Xiong, Shaomin; Kisliuk, Alexander; Somnath, Suhas; Holt, Adam P.; Ovchinnikova, Olga S.; Jesse, Stephen; Martin, Halie J.; Etampawala, Thusitha N.; Dadmun, Mark D.; Sokolov, Alexei P.

    2016-05-20

    The mechanical reinforcement of polymer nanocomposites (PNCs) above the glass transition temperature, Tg, has been extensively researched. However, not much is known about the origin of this effect below Tg. In this paper, we unravel the mechanism of PNC reinforcement within the glassy state by directly probing nanoscale mechanical properties with atomic force microscopy and macroscopic properties with Brillouin light scattering. Our results unambiguously show that the "glassy" Young's modulus in the interfacial polymer layer of PNCs is two-times higher than in the bulk polymer, which results in significant reinforcement below Tg. We ascribe this phenomenon to a high stretching of the chains within the interfacial layer. Since the interfacial chain packing is essentially temperature independent, these findings provide a new insight into the mechanical reinforcement of PNCs also above Tg.

  7. Unraveling the Mechanism of Nanoscale Mechanical Reinforcement in Glassy Polymer Nanocomposites

    DOE PAGES

    Cheng, Shiwang; Bocharova, Vera; Belianinov, Alex; ...

    2016-05-20

    The mechanical reinforcement of polymer nanocomposites (PNCs) above the glass transition temperature, Tg, has been extensively researched. However, not much is known about the origin of this effect below Tg. In this paper, we unravel the mechanism of PNC reinforcement within the glassy state by directly probing nanoscale mechanical properties with atomic force microscopy and macroscopic properties with Brillouin light scattering. Our results unambiguously show that the "glassy" Young's modulus in the interfacial polymer layer of PNCs is two-times higher than in the bulk polymer, which results in significant reinforcement below Tg. We ascribe this phenomenon to a high stretchingmore » of the chains within the interfacial layer. Since the interfacial chain packing is essentially temperature independent, these findings provide a new insight into the mechanical reinforcement of PNCs also above Tg.« less

  8. Microscopic mechanism of reinforcement and conductivity in polymer nanocomposite materials

    NASA Astrophysics Data System (ADS)

    Chang, Tae-Eun

    Modification of polymers by adding various nano-particles is an important method to obtain effective enhancement of materials properties. Within this class of materials, carbon nanotubes (CNT) are among the most studied materials for polymer reinforcement due to their extraordinary mechanical properties, superior thermal and electronic properties, and high aspect ratio. However, to unlock the potential of CNTs for applications, CNTs must be well dispersed in a polymer matrix and the microscopic mechanism of polymer reinforcement by CNTs must be understood. In this study, single-wall carbon nanotube (SWNT) composites with polypropylene (PP)-SWNT and polystyrene (PS)-SWNT were prepared and analyzed. Microscopic study of the mechanism of reinforcement and conductivity by SWNT included Raman spectroscopy, wide-angle X-ray diffraction (WAXD) and dielectric measurement. For PP-SWNT composites, tensile tests show a three times increase in the Young's modulus with addition of only 1 wt% SWNT, and much diminished increase of modulus with further increase in SWNT concentration. For PS-SWNT composites, well-dispersed SWNT/PS composite has been produced, using initial annealing of SWNT and optimum sonication conditions. The studies on the tangential mode in the Raman spectra and TEM indicated well-dispersed SWNTs in a PS matrix. We show that conductivity appears in composites already at very low concentrations, hinting at the formation of a 'percolative' network even below 0.5% of SWNT. The Raman studies for both composites show good transfer of the applied stress from the polymer matrices to SWNTs. However, no significant improvement of mechanical property is observed for PS-SWNT composites. The reason for only a slight increase of mechanical property remains unknown.

  9. Synthesis and characterization of asymmetric polymer/inorganic nanocomposites with pH/temperature sensitivity

    NASA Astrophysics Data System (ADS)

    Zhang, Xinjie; Gao, Chunmei; Liu, Mingzhu; Huang, Yinjuan; Yu, Xiyong; Ding, Enyong

    2013-01-01

    An easy, comprehensive and inexpensive method is demonstrated to produce asymmetric polymer/inorganic nanocomposites in a large quantity. With the aid of Pickering emulsion, unmodified particles aggregate on the surface of emulsion droplets and are fixed in place when the wax solidifies. The exposed surfaces of immobilized SiO2 particles are modified chemically by 2-(dimethylamino) ethylmethacrylate (DMAEMA). With the removal of wax, the exposed side of particles can be further modified chemically by N-isopropylacrylamide (NIPAAm). Based on these procedures, dual responsive asymmetric nanocomposite particles are achieved with both pH and temperature sensitivities. Due to their dual-stimuli and asymmetric structure, these particles have potential applications in molecule targeting, drug delivery and as building blocks for the assembly of complex nanostructure.

  10. From carbon nanotubes and silicate layers to graphene platelets for polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Zaman, Izzuddin; Kuan, Hsu-Chiang; Dai, Jingfei; Kawashima, Nobuyuki; Michelmore, Andrew; Sovi, Alex; Dong, Songyi; Luong, Lee; Ma, Jun

    2012-07-01

    In spite of extensive studies conducted on carbon nanotubes and silicate layers for their polymer-based nanocomposites, the rise of graphene now provides a more promising candidate due to its exceptionally high mechanical performance and electrical and thermal conductivities. The present study developed a facile approach to fabricate epoxy-graphene nanocomposites by thermally expanding a commercial product followed by ultrasonication and solution-compounding with epoxy, and investigated their morphologies, mechanical properties, electrical conductivity and thermal mechanical behaviour. Graphene platelets (GnPs) of 3.57 +/- 0.50 nm in thickness were created after the expanded product was dispersed in tetrahydrofuran using 60 min ultrasonication. Since epoxy resins cured by various hardeners are widely used in industries, we chose two common hardeners: polyoxypropylene (J230) and 4,4'-diaminodiphenylsulfone (DDS). DDS-cured nanocomposites showed a better dispersion and exfoliation of GnPs, a higher improvement (573%) in fracture energy release rate and a lower percolation threshold (0.612 vol%) for electrical conductivity, because DDS contains benzene groups which create π-π interactions with GnPs promoting a higher degree of dispersion and exfoliation of GnPs during curing. This research pointed out a potential trend where GnPs would replace carbon nanotubes and silicate layers for many applications of polymer nanocomposites.In spite of extensive studies conducted on carbon nanotubes and silicate layers for their polymer-based nanocomposites, the rise of graphene now provides a more promising candidate due to its exceptionally high mechanical performance and electrical and thermal conductivities. The present study developed a facile approach to fabricate epoxy-graphene nanocomposites by thermally expanding a commercial product followed by ultrasonication and solution-compounding with epoxy, and investigated their morphologies, mechanical properties, electrical

  11. Light-emitting nanocomposite CdS-polymer electrospun fibres via in situ nanoparticle generation

    NASA Astrophysics Data System (ADS)

    di Benedetto, Francesca; Camposeo, Andrea; Persano, Luana; Laera, Anna Maria; Piscopiello, Emanuela; Cingolani, Roberto; Tapfer, Leander; Pisignano, Dario

    2011-10-01

    We report on the simple, in situ generation of CdS nanocrystals inside electrospun polymer fibres by thermal decomposition of a cadmium thiolate precursor, leading to nanocomposite light-emitting fibres. The modifications induced in the precursor by the thermal decomposition are investigated by a morphological, structural and spectroscopic analysis of the resulting nanocomposite fibres. This approach allows us to overcome nanofabrication difficulties related to disfavoured micro- or nanofluidic molecular flow as given by the direct incorporation of particles in the electrospinning solution. This method therefore enables the synthesis of luminescent, CdS-based composite fibres with emission peaked in the visible range, suitable as building blocks for nanophotonic devices based on light-emitting nanomaterials.

  12. Electrical and electrochemical studies of poly(vinylidene fluoride)-clay nanocomposite gel polymer electrolytes for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Deka, M.; Kumar, A.

    A study is conducted on the electrical and electrochemical properties of nanocomposite polymer electrolytes based on intercalation of poly(vinylidene fluoride) (PVdF) polymer into the galleries of organically modified montmorillonite (MMT) clay. A solution intercalation technique is employed for nanocomposite formation with varying clay loading from 0 to 4 wt.%. X-ray diffraction results show the β phase formation of PVdF on intercalation. Transmission electron microscopy reveals the formation of partially exfoliated nanocomposites. The nanocomposites are soaked with 1 M LiClO 4 in a 1:1 (v/v) solution of propylene carbonate (PC) and diethyl carbonate (DEC) to obtain the required gel electrolytes. The structural conformation of the nanocomposite electrolytes is examined by Fourier transform infrared spectroscopy analysis. Examination with a.c. impedance spectroscopy reveals that the ionic conductivity of the nanocomposite gel polymer electrolytes increases with increase in clay loading and attains a maximum value of 2.3 × 10 -3 S cm -1 for a 4 wt.% clay loading at room temperature. The same composition exhibits enhancement in the electrochemical and interfacial properties as compared with that of a clay-free electrolyte system.

  13. Tailoring the physical properties of homopolymers and polymer nanocomposites via solid-state processing

    NASA Astrophysics Data System (ADS)

    Pierre, Cynthia

    Numerous approaches can be used to modify polymer properties. In this thesis, it is demonstrated that an innovative, continuous, industrially scalable process called solid-state shear pulverization (SSSP) can be used to enhance polymer properties with and without the addition of nanofillers. The SSSP process employs a modified twin-screw extruder in which the barrel is cooled rather than heated, resulting in the polymer being processed at a temperature below its glass transition temperature, if the polymer is amorphous, or its melt transition temperature, if the polymer is semi-crystalline. The material processed via SSSP experiences high levels of shear and compressive stresses, resulting in many repeated fragmentation and fusion steps during pulverization, which can lead to mechanochemistry. This research provides the first in-depth study on the effect of SSSP processing on the molecular structure as well as physical properties of homopolymers. Rheological characterization has demonstrated an increase in the melt viscosity of pulverized poly(ethylene terephthalate) (PET), which can be ascribed to the in situ formation of lightly branched PET. Further evidence of branched PET is provided via a dramatic increase in the rate of crystallization of the pulverized samples. These results suggest that SSSP processing can enhance the reuse and recyclability of PET. While SSSP processing has dramatic effects on the structure of polyesters and consequently their properties, a mild effect is observed for polyolefins. This thesis also demonstrates via a combination of methods that the well-exfoliated state can be achieved via SSSP processing of various polymer nanocomposites, using as-received, unmodified fillers. For example, extensive comparisons are made concerning the thermal stability in air or nitrogen atmosphere of polypropylene (PP)/clay, PP/graphite, and PP/carbon nanotube (CNT) nanocomposites made by SSSP. These comparisons suggest that the mechanism by which CNTs

  14. Blends and Nanocomposite Biomaterials for Articular Cartilage Tissue Engineering

    PubMed Central

    Doulabi, Azadehsadat Hashemi; Mequanint, Kibret; Mohammadi, Hadi

    2014-01-01

    This review provides a comprehensive assessment on polymer blends and nanocomposite systems for articular cartilage tissue engineering applications. Classification of various types of blends including natural/natural, synthetic/synthetic systems, their combination and nanocomposite biomaterials are studied. Additionally, an inclusive study on their characteristics, cell responses ability to mimic tissue and regenerate damaged articular cartilage with respect to have functionality and composition needed for native tissue, are also provided. PMID:28788131

  15. Antifouling Activity of Synthetic Alkylpyridinium Polymers Using the Barnacle Model

    PubMed Central

    Piazza, Veronica; Dragić, Ivanka; Sepčić, Kristina; Faimali, Marco; Garaventa, Francesca; Turk, Tom; Berne, Sabina

    2014-01-01

    Polymeric alkylpyridinium salts (poly-APS) isolated from the Mediterranean marine sponge, Haliclona (Rhizoniera) sarai, effectively inhibit barnacle larva settlement and natural marine biofilm formation through a non-toxic and reversible mechanism. Potential use of poly-APS-like compounds as antifouling agents led to the chemical synthesis of monomeric and oligomeric 3-alkylpyridinium analogues. However, these are less efficient in settlement assays and have greater toxicity than the natural polymers. Recently, a new chemical synthesis method enabled the production of poly-APS analogues with antibacterial, antifungal and anti-acetylcholinesterase activities. The present study examines the antifouling properties and toxicity of six of these synthetic poly-APS using the barnacle (Amphibalanus amphitrite) as a model (cyprids and II stage nauplii larvae) in settlement, acute and sub-acute toxicity assays. Two compounds, APS8 and APS12-3, show antifouling effects very similar to natural poly-APS, with an anti-settlement effective concentration that inhibits 50% of the cyprid population settlement (EC50) after 24 h of 0.32 mg/L and 0.89 mg/L, respectively. The toxicity of APS8 is negligible, while APS12-3 is three-fold more toxic (24-h LC50: nauplii, 11.60 mg/L; cyprids, 61.13 mg/L) than natural poly-APS. This toxicity of APS12-3 towards nauplii is, however, 60-fold and 1200-fold lower than that of the common co-biocides, Zn- and Cu-pyrithione, respectively. Additionally, exposure to APS12-3 for 24 and 48 h inhibits the naupliar swimming ability with respective IC50 of 4.83 and 1.86 mg/L. PMID:24699112

  16. Antifouling activity of synthetic alkylpyridinium polymers using the barnacle model.

    PubMed

    Piazza, Veronica; Dragić, Ivanka; Sepčić, Kristina; Faimali, Marco; Garaventa, Francesca; Turk, Tom; Berne, Sabina

    2014-04-02

    Polymeric alkylpyridinium salts (poly-APS) isolated from the Mediterranean marine sponge, Haliclona (Rhizoniera) sarai, effectively inhibit barnacle larva settlement and natural marine biofilm formation through a non-toxic and reversible mechanism. Potential use of poly-APS-like compounds as antifouling agents led to the chemical synthesis of monomeric and oligomeric 3-alkylpyridinium analogues. However, these are less efficient in settlement assays and have greater toxicity than the natural polymers. Recently, a new chemical synthesis method enabled the production of poly-APS analogues with antibacterial, antifungal and anti-acetylcholinesterase activities. The present study examines the antifouling properties and toxicity of six of these synthetic poly-APS using the barnacle (Amphibalanus amphitrite) as a model (cyprids and II stage nauplii larvae) in settlement, acute and sub-acute toxicity assays. Two compounds, APS8 and APS12-3, show antifouling effects very similar to natural poly-APS, with an anti-settlement effective concentration that inhibits 50% of the cyprid population settlement (EC₅₀) after 24 h of 0.32 mg/L and 0.89 mg/L, respectively. The toxicity of APS8 is negligible, while APS12-3 is three-fold more toxic (24-h LC₅₀: nauplii, 11.60 mg/L; cyprids, 61.13 mg/L) than natural poly-APS. This toxicity of APS12-3 towards nauplii is, however, 60-fold and 1200-fold lower than that of the common co-biocides, Zn- and Cu-pyrithione, respectively. Additionally, exposure to APS12-3 for 24 and 48 h inhibits the naupliar swimming ability with respective IC₅₀ of 4.83 and 1.86 mg/L.

  17. [Progress and prospect of synthetic biodegradable polymers for bone repair and reconstruction].

    PubMed

    Zhao, Zenghui; Jiang, Dianming

    2010-03-01

    To review the latest researches of synthetic biodegradable polymers for bone repair and reconstruction, to predict the progress of bone substitute materials and bone tissue engineering scaffolds in future. The literature concerning synthetic biodegradable polymers as bone substitute materials or bone tissue engineering scaffolds was collected and discussed. Aliphatic polyester, polyanhydride, polyurethane and poly (amino acids) were the most extensively studied synthetic biodegradable polymers as bone substitutes and the scaffolds. Each polymer was of good biological safety and biocompatibility, and the degradation products were nontoxic to human body. The mechanical properties and degradation rate of the polymers could be adjusted by the type or number of the monomers and different synthetic methods. Therefore, the polymers with suitable mechanical strength and degradation rate could be produced according to the different requirements for bone grafting. Preliminary studies in vivo showed their favorable capacity for bone repair. The synthetic biodegradable polymers, especially the copolymers, composite materials and those carrying bone growth factors are expected to be the most promising and ideal biomaterials for bone repair and reconstruction.

  18. Microscopic measurement of the degree of mixing for nanoparticles in polymer nanocomposites by TEM images.

    PubMed

    Kim, Dongsik; Lee, Jun S; Barry, Carol M F; Mead, Joey L

    2007-06-01

    For polymer nanocomposites, the small size of the fillers makes it difficult to analyze the degree of mixing quantitatively and often requires direct assessment via transmission electron microscopy (TEM). To date, qualitative comparisons and indirect measurements of the degree of mixing by measurement of certain properties are the most common methods. Better methods to quantitatively characterize the degree of mixing in nanocomposites would aid in studies investigating the effect of process conditions on the mixing behavior. Alumina/PET nanocomposites of identical composition, but with different degrees of mixing were prepared using a batch mixer. For evaluation of the degree of mixing with respect to both dispersion and distribution, three different techniques were applied and compared. TEM particle density was useful for dispersion, but did not adequately characterize distribution, while the Morisita's index gave poor results due to a wide range of effective particle sizes. Both methods ranked the samples differently compared to direct visual observation. In contrast, the skewness calculated by the quadrat method produced results consistent with visual rankings, and was found to be most effective in comparing and quantifying the degree of mixing. Although the quadrat method requires proper selection of quadrat size for a particular particle concentration, the skewness from the quadrat method was found to be most suitable as a standard index for the degree of mixing in nanocomposites. The usefulness of the quadrat method was verified using a second set of nanocomposites prepared by a twin screw extruder showing the potential for application of this technique for process development and quality control in commercial nanomanufacturing processes. Copyright (c) 2007 Wiley-Liss, Inc.

  19. Thermoelectric behavior of segregated-network polymer nanocomposites.

    PubMed

    Yu, Choongho; Kim, Yeon Seek; Kim, Dasaroyong; Grunlan, Jaime C

    2008-12-01

    Segregated-network carbon nanotube (CNT)-polymer composites were prepared, and their thermoelectric properties were measured as a function of CNT concentration at room temperature. This study shows that electrical conductivity can be dramatically increased by creating a network of CNTs in the composite, while the thermal conductivity and thermopower remain relatively insensitive to the filler concentration. This behavior results from thermally disconnected, but electrically connected, junctions in the nanotube network, which makes it feasible to tune the properties in favor of a higher thermoelectric figure of merit. With a CNT concentration of 20 wt %, these composites exhibit an electrical conductivity of 4800 S/m, thermal conductivity of 0.34 W/m x K and a thermoelectric figure of merit (ZT) greater than 0.006 at room temperature. This study suggests that polymeric thermoelectrics are possible and provides the basis for further development of lightweight, low-cost, and nontoxic polymer composites for thermoelectric applications in the future.

  20. Rouse mode analysis of chain relaxation in polymer nanocomposites

    DOE PAGES

    Kalathi, Jagannathan T.; Kumar, Sanat K.; Rubinstein, Michael; ...

    2015-04-20

    Large-scale molecular dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. In this paper, we examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in themore » polymer melt, as in the case of a polymer–solvent system. However, for NPs larger than half the entanglement mesh size, the effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Furthermore, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Finally, our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect.« less

  1. Rouse mode analysis of chain relaxation in polymer nanocomposites

    DOE PAGES

    Kalathi, Jagannathan T.; Kumar, Sanat K.; Rubinstein, Michael; ...

    2015-04-20

    Large-scale molecular dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. We examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, asmore » in the case of a polymer–solvent system. However, for NPs larger than half the entanglement mesh size, the effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Furthermore, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect.« less

  2. Rouse mode analysis of chain relaxation in polymer nanocomposites

    SciTech Connect

    Kalathi, Jagannathan T.; Kumar, Sanat K.; Rubinstein, Michael; Grest, Gary S.

    2015-04-20

    Large-scale molecular dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. We examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, as in the case of a polymer–solvent system. However, for NPs larger than half the entanglement mesh size, the effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Furthermore, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect.

  3. Rouse mode analysis of chain relaxation in polymer nanocomposites

    SciTech Connect

    Kalathi, Jagannathan T.; Kumar, Sanat K.; Rubinstein, Michael; Grest, Gary S.

    2015-04-20

    Large-scale molecular dynamics simulations are used to study the internal relaxations of chains in nanoparticle (NP)/polymer composites. In this paper, we examine the Rouse modes of the chains, a quantity that is closest in spirit to the self-intermediate scattering function, typically determined in an (incoherent) inelastic neutron scattering experiment. Our simulations show that for weakly interacting mixtures of NPs and polymers, the effective monomeric relaxation rates are faster than in a neat melt when the NPs are smaller than the entanglement mesh size. In this case, the NPs serve to reduce both the monomeric friction and the entanglements in the polymer melt, as in the case of a polymer–solvent system. However, for NPs larger than half the entanglement mesh size, the effective monomer relaxation is essentially unaffected for low NP concentrations. Even in this case, we observe a strong reduction in chain entanglements for larger NP loadings. Furthermore, the role of NPs is to always reduce the number of entanglements, with this effect only becoming pronounced for small NPs or for high concentrations of large NPs. Finally, our studies of the relaxation of single chains resonate with recent neutron spin echo (NSE) experiments, which deduce a similar entanglement dilution effect.

  4. Polymer/glass nanocomposite fiber as an insulating material

    NASA Astrophysics Data System (ADS)

    Taygun, M. Erol; Akkaya, I.; Gönen, S. Ö.; Küçükbayrak, S.

    2017-02-01

    Production of the insulation materials with using nanofibers is the unique idea. With this idea, insulating facilities are enhanced with compressing air between the layers of nanofibers. Basically, glass wool is used as an insulation material. On the other hand, nanofiber glasses can be preferred for insulation purposes to be able to obtain insulation materials better then glass wool. From this point of view in this study, glass nanofibers were formed with sol-gel method by utilizing electrospinning technique. In the experimental part, first of all, sol-gel and polyvinylpyrolidone (PVP)/ethanol solutions were prepared. Then the relation of rheological properties with electrospinnability of PVP/sol-gel solutions was investigated by using a rheometer. Results showed that viscosity increased with the concentration of PVP. Meanwhile, the morphology of electrospun PVP/glass nanofibers was investigated by scanning electron microscope. It was also observed that the homogeneous nanofiber structure was obtained when the viscosity of the solution was 0.006 Pa.s. According to SEM results, it was concluded that nanocomposite fiber having a nanostructured morphology may be a good candidate for thermal insulation applications in the industry.

  5. A study of the toxicology of pyrolysis gases from synthetic polymers

    NASA Technical Reports Server (NTRS)

    Young, W.; Hilado, C. J.; Kourtides, D. A.; Parker, J. A.

    1976-01-01

    An apparatus and procedure for evaluating the toxicity of pyrolysis gases from synthetic polymers are described. In each test, four Swiss albino mice are exposed in a 5-liter chamber to the gases from materials pyrolyzed at 700 C. The apparatus is simple in design, easy to clean, inexpensive and gives reproducible results. Data on several fluorine-containing and polyamide polymers are presented.

  6. A study of the toxicology of pyrolysis gases from synthetic polymers

    NASA Technical Reports Server (NTRS)

    Young, W.; Hilado, C. J.; Kourtides, D. A.; Parker, J. A.

    1976-01-01

    An apparatus and procedure for evaluating the toxicity of pyrolysis gases from synthetic polymers are described. In each test, four Swiss albino mice are exposed in a 5-liter chamber to the gases from materials pyrolyzed at 700 C. The apparatus is simple in design, easy to clean, inexpensive and gives reproducible results. Data on several fluorine-containing and polyamide polymers are presented.

  7. 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

  8. Conductivity enhancement in SiO2 doped PVA:PVDF nanocomposite polymer electrolyte by gamma ray irradiation

    NASA Astrophysics Data System (ADS)

    Hema, M.; Tamilselvi, P.; Pandaram, P.

    2017-07-01

    Nanocomposite polymer electrolyte has been irradiated with 15 Gy Gamma rays. Exposure of gamma radiation caused scissoring and crosslinking of polymer chains thereby increasing amorphous phase of the polymer matrix because of which the ionic conductivity has been enhanced. Ionic conductivity of irradiated nanocomposite polymer electrolyte is enhanced to 9.4 × 10-4 Scm-1 at 303 K compared to un-irradiated system (σ ∼ 1.7 × 10-4 Scm-1). Temperature dependence of ionic conductivity of both un-irradiated and irradiated systems obeys VTF relation. Frequency and temperature dependence of dielectric and modulus of both systems have been analyzed. The ionic transference number of polymer electrolyte has been calculated by Wagner's polarization technique and it confirms that conducting species are predominantly due to ions in both systems.

  9. Structure, scattering patterns and phase behavior of polymer nanocomposites with nonspherical fillers

    SciTech Connect

    Hall, Lisa M; Schweizer, Kenneth S

    2010-01-01

    Polymer nanocomposites made with carbon nanotubes, clay platelets, laponite disks and other novel nonspherical fillers have been the focus of many recent experiments. However, the effects of nanoparticle shape on statistical structure, polymer-mediated effective interactions, scattering patterns, and phase diagrams are not well understood. We extend and apply the polymer reference interaction site model liquid state theory to study the equilibrium properties of pseudo one-, two- and threedimensional particles (rod, disk, cube) of modest steric anisotropy and fixed space-filling volume in a dense adsorbing homopolymer melt up to relatively high volume fractions. The second virial coefficient, nanoparticle potential-of-mean force, osmotic compressibilities, and isotropic spinodal demixing boundaries have been determined. The entropic depletion attraction between nanoparticles is dominant for weakly adsorbing polymer, while strongly adsorbing chains induce a bridging attraction. Intermediate interfacial cohesion results in the formation of a steric stabilizing adsorbed polymer layer around each nanoparticle, which can partially damp inter-filler collective order on various length scales and increase order on an averaged length scale. The details of depletion, stabilization, or bridging behavior are shape-dependent and often, but not always, trends are monotonic with increasing filler dimensionality. Distinctive nanoparticle shape-dependent low angle features are predicted for the collective polymer structure factor associated with competing macrophase fluctuations and microphase-like ordering. The influence of nonzero mixture compressibility on the scattering profiles is established.

  10. Conjugated polymer/nanocrystal nanocomposites for renewable energy applications in photovoltaics and photocatalysis.

    PubMed

    Su, Yu-Wei; Lin, Wei-Hao; Hsu, Yung-Jung; Wei, Kung-Hwa

    2014-11-01

    Conjugated polymer/nanocrystal composites have attracted much attention for use in renewable energy applications because of their versatile and synergistic optical and electronic properties. Upon absorbing photons, charge separation occurs in the nanocrystals, generating electrons and holes for photocurrent flow or reduction/oxidation (redox) reactions under proper conditions. Incorporating these nanocrystals into conjugated polymers can complement the visible light absorption range of the polymers for photovoltaics applications or allow the polymers to sensitize or immobilize the nanocrystals for photocatalysis. Here, the current developments of conjugated polymer/nanocrystal nanocomposites for bulk heterojunction-type photovoltaics incorporating Cd- and Pb-based nanocrystals or quantum dots are reviewed. The effects of manipulating the organic ligands and the concentration of the nanocrystal precursor, critical factors that affect the shape and aggregation of the nanocrystals, are also discussed. In the conclusion, the mechanisms through which conjugated polymers can sensitize semiconductor nanocrystals (TiO2 , ZnO) to ensure efficient charge separation, as well as how they can support immobilized nanocrystals for use in photocatalysis, are addressed.

  11. Anomalous Drag Reduction and Hydrodynamic Interactions of Nanoparticles in Polymer Nanocomposite Thin Films

    NASA Astrophysics Data System (ADS)

    Basu, Jaydeep; Begam, Nafisa; Chandran, Sivasurender; Sprung, Michael

    2015-03-01

    One of the central dogma of fluid physics is the no-slip boundary condition whose validity has come under intense scrutiny, especially in the fields of micro and nanofluidics. Although various studies show the violation of the no-slip condition its effect on flow of colloidal particles in viscous media has been rarely explored. Here we report unusually large reduction of effective drag experienced by polymer grafted nanoparticles moving through a highly viscous film of polymer, well above its glass transition temperature. The extent of drag reduction increases with decreasing temperature and polymer film thickness. We also observe apparent divergence of the wave vector dependent hydrodynamic interaction function of these nanoparticles with an anomalous power law exponent of ~ 2 at the lowest temperatures and film thickness. Such strong hydrodynamic interactions are not expected in polymer melts where these interactions are known to be screened to molecular dimensions. We provide evidence for the presence of large hydrodynamic slip at the nanoparticle-polymer interface and demonstrate its tunability with temperature and confinement. Our study suggests novel physics emerging in dynamics nanoparticles due to confinement and interface wettability in thin films of polymer nanocomposites.

  12. Destruction and recovery of a nanorod conductive network in polymer nanocomposites via molecular dynamics simulation.

    PubMed

    Gao, Yangyang; Cao, Dapeng; Wu, Youping; Liu, Jun; Zhang, Liqun

    2016-03-28

    By adopting coarse-grained molecular dynamics simulation, we investigate the effects of end-functionalization and shear flow on the destruction and recovery of a nanorod conductive network in a functionalized polymer matrix. We find that the end-functionalization of polymeric chains can enhance the electrical conductivity of nanorod filled polymer nanocomposites, indicated by the decrease of the percolation threshold. However, there exists an optimal end-functionalization extent to reach the maximum electrical conductivity. In the case of steady shear flow, both homogeneous conductive probability and directional conductive probability perpendicular to the shear direction decrease with the shear rate, while the directional conductive probability parallel to the shear direction increases. Importantly, we develop a semi-empirical equation to describe the change of the homogeneous conductive probability as a function of the shear rate. Meanwhile, we obtain an empirical formula describing the relationship between the anisotropy of the conductive probability and the orientation of the nanorods. In addition, the conductivity stability increases with increasing nanorod volume fraction. During the recovery process of the nanorod conductive network, it can be fitted well by the model combining classical percolation theory and a time-dependent nanorod aggregation kinetic equation. The fitted recovery rate is similar for different nanorod volume fractions. In summary, this work provides some rational rules for fabricating polymer nanocomposites with excellent performance of electrical conductivity.

  13. Physical Methods for the Preparation of Hybrid Nanocomposite Polymer Latex Particles

    NASA Astrophysics Data System (ADS)

    Teixeira, Roberto F. A.; Bon, Stefan A. F.

    In this chapter, we will highlight conceptual physical approaches towards the fabrication of nanocomposite polymer latexes in which each individual latex particle contains one or more "hard" nanoparticles, such as clays, silicates, titanates, or other metal(oxides). By "physical approaches" we mean that the "hard" nanoparticles are added as pre-existing entities, and are not synthesized in situ as part of the nanocomposite polymer latex fabrication process. We will narrow our discussion to focus on physical methods that rely on the assembly of nanoparticles onto the latex particles after the latex particles have been formed, or its reciprocal analogue, the adhesion of polymer onto an inorganic nanoparticle. First, will discuss the phenomenon of heterocoagulation and its various driving forces, such as electrostatic interactions, the hydrophobic effect, and secondary molecular interactions. We will then address methods that involve assembly of nanoparticles onto or around the more liquid precursors (i.e., swollen/growing latex particles or monomer droplets). We will focus on the phenomenon of Pickering stabilization. We will then discuss features of particle interaction with soft interfaces, and see how the adhesion of particles onto emulsion droplets can be applied in suspension, miniemulsion, and emulsion polymerization. Finally, we will very briefly mention some interesting methods that make use of interface-driven templating for making well-defined assembled clusters and supracolloidal structures.

  14. Nanocomposite polymer carbon-black coating for triggering pyro-electrohydrodynamic inkjet printing

    NASA Astrophysics Data System (ADS)

    Coppola, S.; Mecozzi, L.; Vespini, V.; Battista, L.; Grilli, S.; Nenna, G.; Loffredo, F.; Villani, F.; Minarini, C.; Ferraro, P.

    2015-06-01

    The pyro-electrohydrodynamic (EHD) manipulation of liquids has been discovered and demonstrated recently as a high resolution printing technique avoiding the use of nozzles and external electrodes. The activation of the pyro-electric effect is usually achieved on ferroelectric crystals by an external heating source or by an infrared laser. Here, we show an original modality for triggering the pyro-EHD process through a light-absorbing polymer nanocomposite thin layer deposited on the ferroelectric substrate, thus overcoming some limitations of the previous configuration. Significant simplification and compactness of the set-up is achieved thanks to the nanocomposite coating, since a commercial low-cost white-light halogen lamp can be adopted to trigger the pyro-jetting process from a liquid reservoir. Remarkably, high resolution is achieved in dispensing very high viscous liquids. Practical demonstrations in polymer optical microlenses direct printing using polydimethylsiloxane and poly(methyl methacrylate) are finally reported to validate the approach in handling high-viscous polymers for practical applications.

  15. Largely enhanced thermal and mechanical properties of polymer nanocomposites via incorporating C60@graphene nanocarbon hybrid

    NASA Astrophysics Data System (ADS)

    Song, Ping'an; Liu, Lina; Huang, Guobo; Yu, Youming; Guo, Qipeng

    2013-12-01

    Although considerable progress has been achieved to create advanced polymer nanocomposites using nanocarbons including fullerene (C60) and graphene, it remains a major challenge to effectively disperse them in a polymer matrix and to fully exert their extraordinary properties. Here we report a novel approach to fabricate the C60@graphene nanocarbon hybrid (C60: ˜47.9 wt%, graphene: ˜35.1%) via three-step reactions. The presence of C60 on a graphene sheet surface can effectively prevent the aggregation of the latter which in turn helps the dispersion of the former in a polymer matrix during melt-processing. C60@graphene is found to be uniformly dispersed in a polypropylene (PP) matrix. Compared with pristine C60 or graphene, C60@graphene further improves the thermal stability and mechanical properties of PP. The incorporation of 2.0 wt% C60@graphene (relative to PP) can remarkably increase the initial degradation temperature by around 59 ° C and simultaneously enhance the tensile strength and Young’s modulus by 67% and 76%, respectively, all of which are higher than those of corresponding PP/C60 (graphene) nanocomposites. These significant performance improvements are mainly due to the free-radical-trapping effect of C60, and the thermal barrier and reinforcing effects of graphene nanosheets as well as the effective stress load transfer. This work provides a new methodology to design multifunctional nanohybrids for creating advanced materials.

  16. Nanoindentation of Functionally Graded Polymer Nanocomposites: Assessment of the Strengthening Parameters through Experiments and Modeling

    NASA Astrophysics Data System (ADS)

    Nardi, Tommaso; Hammerquist, Chad; Nairn, John; Karimi, Ayat; Manson, Jan-Anders; Leterrier, Yves

    2015-08-01

    NNanoindentation tests were carried out on the surface of polymer nanocomposites exhibiting either graded or homogeneous distributions of Fe3O4@silica core-shell nanoparticles in a photocurable polymeric matrix. The results reveal a complex interplay between graded morphology, indentation depth and calculated modulus and hardness values, which was elucidated through numerical simulations. First, it was experimentally shown how for small (1 µm) indentations, large increases in modulus (up to +40%) and hardness (up to +93%) were obtained for graded composites with respect to their homogeneous counterparts, whereas at a larger indentation depth (20 µm) the modulus and hardness of the graded and homogeneous composites did not substantially differ from each other and from those of the pure polymer. Then, through a Material Point Method approach, experimental nanoindentation tests were successfully simulated, confirming the importance of the indentation depth and of the associated plastic zone as key factors for a more accurate design of graded polymer nanocomposites whose mechanical properties are able to fulfill the requirements encountered during operational life.

  17. Radiation detection with CdTe quantum dots in sol-gel glass and polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Manickaraj, Kavin; Wagner, Brent K.; Kang, Zhitao

    2013-05-01

    Optically based radiation detectors in various fields of science still suffer from low resolution, sensitivity and efficiency that restrict their overall performance. Quantum dots (QD) are well-suited for such detectors due to their unique optical properties. CdTe QDs show fast luminescence decay times, high conversion efficiencies, and have band gaps strongly dependent on the particle radius. Since QD particle sizes are well below the wavelengths of their emissions, they remain optically transparent when incorporated in both polymer and sol-gel based silica glass due to negligible optical scattering. In addition, as these composite materials can greatly improve the mechanical robustness of alpha-particle detectors, conventionally known to have delicate components, CdTe QDs show high promise for radiation sensing applications. These properties are especially advantageous for alpha-particle and potentially neutron detection. In this work, CdTe QD-based glass or polymer matrix nanocomposites were synthesized for use as alpha-particle detection scintillators.. The fast photo-response and decay times provide excellent time resolution. The radiation responses of such nanocomposites in polymer or glass matrices were investigated.

  18. Role of bound polymer mobility on multiscale dynamics of PEO in attractive nanocomposites

    NASA Astrophysics Data System (ADS)

    Senses, Erkan; Faraone, Antonio; Akcora, Pinar

    We study intermediate and large scale chain dynamics in nanocomposites where particle-bound polymer (PMMA) and matrix (PEO) chains are chemically different, miscible, and have very large Tg difference (ΔTg ~ 200 K). These nanocomposites with dynamically asymmetric `polymer blend interphases' were shown to exhibit an unusual reversible thermal-stiffening accompanied by vitreous-to-rubbery transition of PMMA.* Using quasi-elastic neutron scattering, this work examines the impact of mobility of the bound-polymer on segmental and collective dynamics of the matrix chains at sub-ns to 100 ns range. While bare silica particles appear to slow down the segmental relaxation, in the composites with PMMA coated particles the Rouse dynamics of PEO is identical to its bulk behavior, possibly due to the negligible enthalpic interaction inherent to this blend system. On larger scale, we observed ~25% increase in the apparent tube diameter of PEO when PMMA is glassy. Remarkably, the tube size recovers its bulk value as PMMA softens at elevated temperatures. The resulting disentanglement-entanglement transition of PEO under hard and soft confinement well relates to the macroscopic softening-stiffening transition of these composites as evidenced from the bulk rheology. (*ACS Appl. Mater. Interfaces ,2015, 7 (27), pp 14682-14689)

  19. Characterization of Nanoclay Orientation in Polymer Nanocomposite Film by Small-angle X-ray Scattering

    SciTech Connect

    P Nawani; C Burger; L Rong; B Chu; B Hsiao; A Tsou; W Weng

    2011-12-31

    The orientation distribution of layer-shaped nanoclays (e.g. organoclays and pristine clays) dispersed in a polymer matrix is an important parameter to control the properties of polymer nanocomposites. In this study, we demonstrate that the use of multi-directional 2-D small-angleX-rayscattering (SAXS) can quantitatively describe the orientation distribution of organoclays (e.g. Cloisite C20A) in melt-pressed nanocompositefilms, containing ethylene-vinyl acetate (EVA) copolymers as polymer matrices. Different weight fractions of organoclays were used to alter the orientation profile of nanocompositefilms, in which the dispersion and morphology of organoclays were also characterized by complementary 2-D and 3-D transmission electron microscopy (TEM). All nanocomposites exhibited mixed intercalation/exfoliation clay morphology, where the intercalated structure possessed partial orientation parallel to the in-plane direction of the film. The higher content of the clay loading showed a higher clay orientation. A simple analytical scheme for SAXS data analysis to determine the orientation parameter (P{sub 2}) was demonstrated, the results of which are in agreement with the gas permeation properties of the nanocompositefilms.

  20. Synthesis of ferromagnetic nanoparticles, formic acid oxidation catalyst nanocomposites, and late-transition metal-boride intermetallics by unique synthetic methods and single-source precursors

    NASA Astrophysics Data System (ADS)

    Wellons, Matthew S.

    The design, synthesis, and characterization of magnetic alloy nanoparticles, supported formic acid oxidation catalysts, and superhard intermetallic composites are presented. Ferromagnetic equatomic alloy nanoparticles of FePt, FePd, and CoPt were synthesized utilizing single-source heteronuclear organometallic precursors supported on an inert water-soluble matrix. Direct conversion of the precursor-support composite to supported ferromagnetic nanoparticles occurs under elevated temperatures and reducing conditions with metal-ion reduction and minimal nanoparticle coalescence. Nanoparticles were easily extracted from the support by addition of water and characterized in structure and magnetic properties. Palladium and platinum based nanoparticles were synthesized with microwave-based and chemical metal-ion reduction strategies, respectively, and tested for catalytic performance in a direct formic acid fuel cell (DFAFC). A study of palladium carbide nanocomposites with various carbonaceous supports was conducted and demonstrated strong activity comparable to commercially available palladium black, but poor catalytic longevity. Platinum-lead alloy nanocomposites synthesized with chemical reduction and supported on Vulcan carbon demonstrated strong activity, excellent catalytic longevity, and were subsequently incorporated into a prototype DFAFC. A new method for the synthesis of superhard ceramics on polymer substrates called Confined Plasma Chemical Deposition (CPCD) was developed. The CPCD method utilizes a tuned Free Electron Laser to selectively decompose the single-source precursor, Re(CO)4(B3H8), in a plasma-like state resulting in the superhard intermetallic ReB2 deposited on polymer substrates. Extension of this method to the synthesis of other hard of superhard ceramics; WB4, RuB2, and B4C was demonstrated. These three areas of research show new synthetic methods and novel materials of technological importance, resulting in a substantial advance in their

  1. Polysaccharide-based nanocomposites and their applications

    PubMed Central

    Zheng, Yingying; Monty, Jonathan; Linhardt, Robert J.

    2014-01-01

    Polysaccharide nanocomposites have become increasingly important materials over the past decade. Polysaccharides offer a green alternative to synthetic polymers in the preparation of soft nanomaterials. They have also been used in composites with hard nanomaterials, such as metal nanoparticles and carbon-based nanomaterials. This mini review describes methods for polysaccharide nanocomposite preparation and reviews the various types and diverse applications for these novel materials. PMID:25498200

  2. Feasibility of Plasma Treated Clay in Clay/Polymer Nanocomposites Powders for use Laser Sintering (LS)

    NASA Astrophysics Data System (ADS)

    Almansoori, Alaa; Seabright, Ryan; Majewski, C.; Rodenburg, C.

    2017-05-01

    The addition of small quantities of nano-clay to nylon is known to improve mechanical properties of the resulting nano-composite. However, achieving a uniform dispersion and distribution of the clay within the base polymer can prove difficult. A demonstration of the fabrication and characterization of plasma-treated organoclay/Nylon12 nanocomposite was carried out with the aim of achieving better dispersion of clay platelets on the Nylon12 particle surface. Air-plasma etching was used to enhance the compatibility between clays and polymers to ensure a uniform clay dispersion in composite powders. Downward heat sintering (DHS) in a hot press is used to process neat and composite powders into tensile and XRD specimens. Morphological studies using Low Voltage Scanning Electron Microscopy (LV-SEM) were undertaken to characterize the fracture surfaces and clay dispersion in powders and final composite specimens. Thermogravimetric analysis (TGA) testing performed that the etched clay (EC) is more stable than the nonetched clay (NEC), even at higher temperatures. The influence of the clay ratio and the clay plasma treatment process on the mechanical properties of the nanocomposites was studied by tensile testing. The composite fabricated from (3% EC/N12) powder showed ~19 % improvement in elastic modulus while the composite made from (3% NEC/N12) powder was improved by only 14%). Most notably however is that the variation between tests is strongly reduced when etch clay is used in the composite. We attribute this to a more uniform distribution and better dispersion of the plasma treated clay within polymer powders and ultimately the composite.

  3. Neutron diffraction on polymer nanocomposites - A tool for structural and orientation studies

    NASA Astrophysics Data System (ADS)

    Sapalidis, A. A.; Katsaros, F. K.; Steriotis, Th A.; Kanellopoulos, N. K.; Dante, S.; Hauss, T.

    2012-02-01

    A series of Polyvinyl alcohol (Mowiol 5-88) - Bentonite nanocomposite films with predefined clay loading (up to 0-20%), were prepared via solvent casting technique. The developed films, due to the favourable polymer-particle interactions, revealed excellent dispersion of the clay particles in the polymer matrix and improved properties. Furthermore, the properties of PVA/clay nanocomposites as well as their structural changes as a function of the relative humidity were thoroughly investigated using neutron membrane diffraction experiments. The samples prior their measurement were equilibrated at different relative humidity levels (%RH) using either H2O or D2O. The application of contrast variation technique enabled us to investigate the contribution of both the polymer and the clay particles to the diffraction spectra. Thus, the use of H2O enlightened the low Q region, providing information about the structure of the inorganic phase and specifically the stacking of the clay platelets. The diffraction patterns in this region obtained from perpendicular and in-plane sample positions revealed that there is a specific orientation of bentonite plates, parallel to the film surface. This conclusion is in agreement with the results obtained from XRD and gas permeability technique, in which the well organized and dispersed impermeable inorganic layers, increase the resistance in flow through the nanocomposites film, acting as gas barriers. On the other hand, diffraction experiments on pre-equilibrated with D2O samples revealed the structural changes in polymeric matrix, due to hydration. The obtained peak revealed the presence of a new crystalline phase, presumably induced by the presence of the silicates, which is in agreement with DSC data reported in previous studies.

  4. Synthesis of metal-polymer nanocomposites for fuel applications

    NASA Astrophysics Data System (ADS)

    Pontes Lima, Ricardo Jose

    . However, the versatility of the mechanical milling technique suggests that a vast range of organic compounds could be applied to the capping of particles. Thus, developing a new method to obtain metal nanosized particles coated with chemical substances that can further improve the properties of particles is a great challenge. The first contribution of this work is to investigate the reactive milling process of metal powders, such as boron and aluminum, to better understand the experimental methodology as a means to obtain energetic-capped metal particles. To this end, a comparative experimental study was performed to evaluate two variations of the mechanical milling. In a typical procedure, metal powders and the reagents are poured into the mill vial at the start of milling. The organic reactions occur simultaneously in the milling process. In the alternative procedure, the powders are milled prior the addition of the organic reagent, thus a stepwise process is done. For both methods, an organic functionalized compound was grafted onto the particles, followed by their incorporation into an energetic polymer matrix to create a metal-polymer composite. The results highlight the differences in shape in size of particles, identifying some drawbacks for both applications, as well as analyzing the effects on combustion properties of the organic-capped powders and the binder composites. The analysis of the first results of the reactive milling showed that this way might lead to by-products and self-polymerization of organic coatings. That is the main drawback for the simultaneous milling process, preventing a better performance of as-milled powders. Considering this problem, it was necessary to modify the milling procedure to further improve the capping of metal particle. Thus, the second part of experiments applies an energetic polymer direct grafted onto particles as a means to further improvements in the energetic properties of powders. Glycidyl azide polymer (GAP) was chosen

  5. Two-dimensional Clay and Graphene Nanosheets for Polymer Nanocomposites and Energy Storage Applications

    NASA Astrophysics Data System (ADS)

    Qian, Yuqiang

    Clay and graphene nanosheets are attractive to materials scientists due to their unique structural and physical properties and potentially low cost. This thesis focuses on the surface modification and structure design of clay and graphene nanosheets, targeting special requirements in polymer nanocomposites and energy storage applications. The high aspect ratio and stiffness of clay and graphene nanosheets make them promising candidates to reinforce polymers. However, it is challenging to achieve a good dispersion of the nanosheets in a polymer matrix. It is demonstrated in this study that organic modifications of clay and graphene nanosheets lead to better filler dispersion in polymer matrices. A prepolymer route was developed to achieve clay exfoliation in a polyurethane-vermiculite system. However, the phase-separated structure of the polyurethane matrix was disrupted. Intragallery catalysis was adopted to promote the clay exfoliation during polymerization. With both catalytic and reactive groups on the clay modifier, the polyurethane-vermiculite nanocomposites showed a significant increase in modulus and improved barrier performance, compared to neat polyurethane. The toughening effect of graphene on thermosetting epoxies and unsaturated polyesters (UPs) was also investigated. Various types of graphene with different structures and surface functionalities were incorporated into the thermosetting resin by in situ polymerization. The toughening effect was observed for epoxy nanocomposites at loading levels of less than 0.1 wt%, and a peak of fracture toughness was observed at 0.02 or 0.04 wt% of graphene loadings for all epoxy-graphene systems. A microcrack-crazing mechanism was proposed to explain the fracture behavior of epoxy-graphene systems based on fractography observations. Similar peak behavior of fracture toughness was not observed in UP system. UP nanocomposites with modified graphene oxide showed better mechanical performance than those with unmodified

  6. High-performance dual-action polymer-TiO2 nanocomposite films via melting processing.

    PubMed

    Kubacka, Anna; Serrano, Cristina; Ferrer, Manuel; Lünsdorf, Heinrich; Bielecki, Piotr; Cerrada, María Luisa; Fernández-García, Marta; Fernández-García, Marcos

    2007-08-01

    The incorporation of TiO2 nanoparticles into (ethylene-vinyl alcohol)-based food packaging copolymers affords an opportunity to synthesize polymer-based nanocomposite materials with novel and powerful biocidal and photodegradability properties, resulting in the production of an advanced, environmentally friendly system prepared using a cost-effective synthesis method via a simple melt compounding without the need of a coupling agent incorporation. The presented materials display an unprecedented performance in the killing of both Gram positive and negative bacteria without the necessity of being release to the media and an easy degradation under sunlight which favorably competes with biodegradation procedures.

  7. Carbon Nanotube/Space Durable Polymer Nanocomposite Films for Electrostatic Charge Dissipation

    NASA Technical Reports Server (NTRS)

    Smith, J. G., Jr.; Watson, K. A.; Thompson, C. M.; Connell, J. W.

    2002-01-01

    Low solar absorptivity, space environmentally stable polymeric materials possessing sufficient electrical conductivity for electrostatic charge dissipation (ESD) are of interest for potential applications on spacecraft as thin film membranes on antennas, solar sails, large lightweight space optics, and second surface mirrors. One method of imparting electrical conductivity while maintaining low solar absorptivity is through the use of single wall carbon nanotubes (SWNTs). However, SWNTs are difficult to disperse. Several preparative methods were employed to disperse SWNTs into the polymer matrix. Several examples possessed electrical conductivity sufficient for ESD. The chemistry, physical, and mechanical properties of the nanocomposite films will be presented.

  8. Thermal conduction in aligned carbon nanotube-polymer nanocomposites with high packing density.

    PubMed

    Marconnet, Amy M; Yamamoto, Namiko; Panzer, Matthew A; Wardle, Brian L; Goodson, Kenneth E

    2011-06-28

    Nanostructured composites containing aligned carbon nanotubes (CNTs) are very promising as interface materials for electronic systems and thermoelectric power generators. We report the first data for the thermal conductivity of densified, aligned multiwall CNT nanocomposite films for a range of CNT volume fractions. A 1 vol % CNT composite more than doubles the thermal conductivity of the base polymer. Denser arrays (17 vol % CNTs) enhance the thermal conductivity by as much as a factor of 18 and there is a nonlinear trend with CNT volume fraction. This article discusses the impact of CNT density on thermal conduction considering boundary resistances, increased defect concentrations, and the possibility of suppressed phonon modes in the CNTs.

  9. Characterization of magnetization-induced second harmonic generation in iron oxide polymer nanocomposites.

    PubMed

    Vandendriessche, Stefaan; Valev, Ventsislav K; Verbiest, Thierry

    2012-01-10

    We have measured the magnetization-induced second harmonic generation (MSHG) of a nanocomposite consisting of iron oxide nanoparticles in a polymer film. The existing theoretical framework is extended to include DC magnetic fields in order to characterize the MSHG signal and analyze the measurements. Additionally, magnetic hysteresis loops are measured for four principal polarizer-analyzer configurations, revealing the P(IN)-P(OUT) and S(IN)-P(OUT) polarizer-analyzer configurations to be sensitive to the transverse magnetic field. These results demonstrate the use of MSHG and the applied formalism as a tool to study magnetic nanoparticles and their magnetic properties.

  10. Development of novel catalytically active polymer-metal-nanocomposites based on activated foams and textile fibers

    PubMed Central

    2013-01-01

    In this paper, we report the intermatrix synthesis of Ag nanoparticles in different polymeric matrices such as polyurethane foams and polyacrylonitrile or polyamide fibers. To apply this technique, the polymer must bear functional groups able to bind and retain the nanoparticle ion precursors while ions should diffuse through the matrix. Taking into account the nature of some of the chosen matrices, it was essential to try to activate the support material to obtain an acceptable value of ion exchange capacity. To evaluate the catalytic activity of the developed nanocomposites, a model catalytic reaction was carried out in batch experiments: the reduction of p-nitrophenol by sodium borohydride. PMID:23680063

  11. Functionalization of Natural Graphite for Use as Reinforcement in Polymer Nanocomposites.

    PubMed

    Araujo, Rafael; Marques, Maria F V; Jonas, Renato; Grafova, Iryna; Grafov, Andriy

    2015-08-01

    Graphite is a naturally abundant material that has been used as reinforcing filler to produce polymeric nanocomposites for various applications including automotive, aerospace and electric-electronic. The objective of this study was to develop methodologies of graphite nanosheets preparation and for incorporation into polymer matrices. By means of different chemical and physical treatments, natural graphite was modified and subsequently characterized by X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetry (TGA) and the particle size determination. The results obtained clearly show that after the treatments employed, polar chemical groups were inserted on the natural graphite surface. Nanosized