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Polymer Matrix (polymer + matrix)

Distribution by Scientific Domains

Polymers and Materials Science	78%
Chemistry	12%
Physics and Astronomy	3%
Engineering	2%
2 Other Domains	5%

Distribution within Polymers and Materials Science

Polymer Science & Technology General	50%
General & Introductory Materials Science	28%
4 Other Subdomains	22%

Selected Abstracts

A Quantum-Mechanical QSAR Model to Predict the Refractive Index of Polymer Matrices

MOLECULAR INFORMATICS, Issue 10 2006
Andrew
Abstract Refractive index (RI) is an important optical property for polymer matrices, especially when the color or tint of the cured material is of interest. This is certainly the case for dental restorative applications. In this work, results are presented for a quantitative,structure activity relationship derived from relevant semiempirical quantum mechanical information. This model predicts the RI for a wide variety of polymer matrices using representative structures of polymers, including resin components of several currently used dental restorative materials. The AM1 semiempirical method was used for calculations due to its speed and general reliability. Several structural subunits of the polymer chains were used for the QSAR analysis, but dimer moieties produced the best results for some 60 polymers. The final QSAR model was composed of a multilinear equation that featured the highest occupied molecular orbital , the lowest unoccupied molecular orbital gap and a polarizability index as the two descriptors best able to account for the variation in the data. The final model had R2=0.963, R2cv=0.959, F=740, and s2=0.0002. Other quality indicators for the correlation and the individual descriptors were within acceptable limits. The presence of electronically related descriptors is encouraging, as these are conceptually tied to the phenomenon of RI. The difference between a theoretically predicted value for poly(propylene oxide) and its monomer was 0.04, as compared to 0.09 from experimental data. [source]

Macroscopically Aligned Ionic Self-Assembled Perylene-Surfactant Complexes within a Polymer Matrix,

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2008
Ari Laiho
Abstract Ionic self-assembled (ISA) surfactant complexes present a facile concept for self-assembly of various functional materials. However, no general scheme has been shown to allow their overall alignment beyond local polydomain-like order. Here we demonstrate that ionic complexes forming a columnar liquid-crystalline phase in bulk can be aligned within polymer blends upon shearing, taken that the matrix polymers have sufficiently high molecular weight. We use an ISA complex of N,N,-bis(ethylenetrimethylammonium)perylenediimide/bis(2-ethylhexyl) phosphate (Pery-BEHP) blended with different molecular weight polystyrenes (PS). Based on X-ray scattering studies and transmission electron microscopy the pure Pery-BEHP complex was found to form a two-dimensional oblique columnar phase where the perylene units stack within the columns. Blending the complex with PS lead to high aspect ratio Pery-BEHP aggregates with lateral dimension in the mesoscale, having internal columnar liquid-crystalline order similar to the pure Pery-BEHP complex. When the Pery-BEHP/PS blend was subjected to a shear flow field, the alignment of perylenes can be achieved but requires sufficiently high molecular weight of the polystyrene matrix. The concept also suggests a simple route for macroscopically aligned nanocomposites with conjugated columnar liquid-crystalline functional additives. [source]

Palladium Nanowire from Precursor Nanowire: Crystal-to-Crystal Transformation via In,Situ Reduction by Polymer Matrix,

ADVANCED FUNCTIONAL MATERIALS, Issue 14 2007
S. Porel
Abstract Precursor nanowires of potassium palladium(II) chloride crystallized inside a poly(vinyl alcohol) film are reduced to palladium nanowires by the polymer itself under mild thermal annealing. The chemical reaction occurring in situ inside the polymer film, including byproduct formation, is investigated through electronic absorption and X-ray photoelectron spectroscopy together with atomic force and electron microscopy. The overall process can be described as a novel case of crystal-to-crystal transformation at the nanoscopic level. Optical limiting characteristics of the nanowire-embedded polymer film are explored. The fabrication procedure developed, involving chemistry inside a polymer matrix mediated by the polymer, opens up a convenient route to the fabrication of free-standing metal nanowire-embedded thin films. [source]

A Combination of Selective Light Reflection and Fluorescence Modulation in a Cholesteric Polymer Matrix

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 3 2005
Dasha Medvedeva
Abstract Summary: The phase behavior and optical properties of a cholesteric ternary copolymer, containing nematogenic phenylbenzoate, cholesteric, and photochromic diarylethene side groups, and its mixture with 2 wt.-% fluorescent dopant were studied. The investigation of the kinetics of a photochemical opening-cycle process of the photochromic groups in the cholesteric mixture proved the energy transfer from the fluorescent dopant to the photochromic diarylethene groups. It was shown that the fluorescence intensity of the fluorescent dopant could be controlled by the portion of the "closed" form of the diarylethene groups. During the photocyclization of the photochromic groups a "degeneration" of the selective light reflection of the cholesteric matrix is observed. Fluorescence-resonance energy transfer makes possible the process of photosensitization of the back ring-opening photoreaction of the photochromic diarylethene groups in the cholesteric polymer matrix. [source]

Determination of Size Distributions of Concentrated Polymer Particles Embedded in a Solid Polymer Matrix

PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 1 2008
Ezequiel R. Soulé
Abstract In this work we present the results obtained from the size characterization of polymer particles embedded in a solid polymer matrix using Static Light Scattering (SLS) and Scanning Electron Microscopy (SEM). The analyzed samples are the result of the solution polymerization of isobornyl methacrylate (IBoMA) in polyisobutylene (PIB) at complete conversion. Induced by polymerization, the system undergoes phase separation. As a result, spherical micron sized particles rich in PIB are formed. At the end of the polymerization, the particles become trapped in a solid polymer matrix rich in Poly-IBoMA. Size, concentration, and refractive index, make the resulting particle system scatter light under the Rayleigh-Debye-Gans (RDG) regime with interparticle interference. For Light Scattering (LS) characterization the samples are measured with a Flat Cell Static Light Scattering (FCSLS) apparatus, in which the reaction takes place. The resulting SLS spectra are analyzed using the Percus-Yevick approximation to model the interference effects. The local monodisperse approximation is used to consider polydispersity in the particle sizes. The estimated particle size distributions agree well with the measurements from SEM. In this work a concentrated particle system that naturally scatters light according to the RDG regime has been fully characterized in terms of its particle size distribution. This work, against the opinion of other authors, shows the feasibility of measuring still particles using a one dimensional array of light detectors. [source]

Formation and Distribution of Silver Nanoparticles in a Functional Plasma Polymer Matrix and Related Ag+ Release Properties

PLASMA PROCESSES AND POLYMERS, Issue 7 2010
Enrico Körner
Abstract Plasma polymer coatings with embedded Ag nanoparticles were deposited in a low pressure RF plasma reactor using an asymmetrical setup with an Ag electrode. The plasma polymer was deposited from a reactive gas/monomer mixture of CO2/C2H4 yielding a functional hydrocarbon matrix. In addition, Ar was simultaneously used to sputter Ag atoms from the Ag electrode, forming nanoparticles within the growing polymer matrix. The influence of the power input, gas ratio and coating thickness on both, the Ag content and the Ag nanoparticle morphology, as well as the distribution in the polymer matrix were investigated. It was found that both increasing the power input and the CO2 ratio result in a higher incorporation of Ag into the matrix. [source]

Development of a 1-Methylcyclopropene (1-MCP) Sachet Release System

JOURNAL OF FOOD SCIENCE, Issue 1 2006
Younsuk S. Lee
ABSTRACT The partitioning of 1-methylcyclopropene (1-MCP) between the gas/polymer matrix was determined for 2 adsorbing agents and 4 sachet materials to estimate the adsorption potential of 1-MCP at 23°C. The release study was performed using a closed system under 2 different environmental conditions, dry air (0% RH) and 90% RH. Sachets made from Tyvek®, paper, low-density polyethylene (LDPE), and polyvinyl acetate (PVA) materials were fabricated to contain silica gel and activated carbon. Activated carbon sachets did not release 1-MCP at either testing condition. Activated carbon had a very strong affinity for 1-MCP. The permeability coefficients of 1-MCP and water in polyethylene and polyvinyl acetate films were determined using a quasi-isostatic method. LDPE sachets containing silica gel had similar 1-MCP release rates at both 0% and 90% RH. PVA sachets containing silica gel had slow release of 1-MCP. The amount of 1-MCP released from PVA sachets containing silica gel at 90% RH was larger than the amount of 1-MCP released at 0% RH. Release of 1-MCP from paper and Tyvek sachets was largely dependent on the sorbate-absorbing ability of the adsorbing agents. [source]

Porous Structures: In situ Porous Structures: A Unique Polymer Erosion Mechanism in Biodegradable Dipeptide-Based Polyphosphazene and Polyester Blends Producing Matrices for Regenerative Engineering (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
Mater.
Abstract Synthetic biodegradable polymers serve as temporary substrates that accommodate cell infiltration and tissue in-growth in regenerative medicine. To allow tissue in-growth and nutrient transport, traditional three-dimensional (3D) scaffolds must be prefabricated with an interconnected porous structure. Here we demonstrated for the first time a unique polymer erosion process through which polymer matrices evolve from a solid coherent film to an assemblage of microspheres with an interconnected 3D porous structure. This polymer system was developed on the highly versatile platform of polyphosphazene-polyester blends. Co-substituting a polyphosphazene backbone with both hydrophilic glycylglycine dipeptide and hydrophobic 4-phenylphenoxy group generated a polymer with strong hydrogen bonding capacity. Rapid hydrolysis of the polyester component permitted the formation of 3D void space filled with self-assembled polyphosphazene spheres. Characterization of such self-assembled porous structures revealed macropores (10,100 ,m) between spheres as well as micro- and nanopores on the sphere surface. A similar degradation pattern was confirmed in vivo using a rat subcutaneous implantation model. 12 weeks of implantation resulted in an interconnected porous structure with 82,87% porosity. Cell infiltration and collagen tissue in-growth between microspheres observed by histology confirmed the formation of an in situ 3D interconnected porous structure. It was determined that the in situ porous structure resulted from unique hydrogen bonding in the blend promoting a three-stage degradation mechanism. The robust tissue in-growth of this dynamic pore forming scaffold attests to the utility of this system as a new strategy in regenerative medicine for developing solid matrices that balance degradation with tissue formation. [source]

Squaraine-Doped Functional Nanoprobes: Lipophilically Protected Near-Infrared Fluorescence for Bioimaging

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
Yong-Deok Lee
Abstract Hydrophobically stabilized near-IR fluorescence from self-assembled nanoprobes composed of amphiphilic poly(maleic anhydride- alt -octadec-1-ene) (PMAO) and lipophilized squaraine dopants is reported. From comparative studies with varying lipophilicity of squaraine dyes as well as of nanoparticulate polymer matrices, it is found that dual protection by simultaneous lipophilization of the dye-polymer pair greatly improves the chemical stability of labile squaraine dyes, to produce efficient NIR fluorescence in physiological aqueous milieux. The surface properties of negatively charged PMAO nanoparticles are readily modified by coating with an amine-rich cationic glycol chitosan with biofunctionality. Efficient cellular imaging and in vivo sentinel lymph node mapping with size and surface-controlled nanoprobes demonstrate that lipophilic dual protection of NIR fluorescence and the underlying functional nanoprobe approach hold great potential for bioimaging applications. [source]

In situ Porous Structures: A Unique Polymer Erosion Mechanism in Biodegradable Dipeptide-Based Polyphosphazene and Polyester Blends Producing Matrices for Regenerative Engineering

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
Meng Deng
Abstract Synthetic biodegradable polymers serve as temporary substrates that accommodate cell infiltration and tissue in-growth in regenerative medicine. To allow tissue in-growth and nutrient transport, traditional three-dimensional (3D) scaffolds must be prefabricated with an interconnected porous structure. Here a unique polymer erosion process through which polymer matrices evolve from a solid coherent film to an assemblage of microspheres with an interconnected 3D porous structure is demonstrated for the first time. This polymer system is developed on the highly versatile platform of polyphosphazene-polyester blends. Co-substituting a polyphosphazene backbone with both hydrophilic glycylglycine dipeptide and hydrophobic 4-phenylphenoxy group generates a polymer with strong hydrogen bonding capacity. Rapid hydrolysis of the polyester component permits the formation of 3D void space filled with self-assembled polyphosphazene spheres. Characterization of such self-assembled porous structures reveals macropores (10,100 ,m) between spheres as well as micro- and nanopores on the sphere surface. A similar degradation pattern is confirmed In vivo using a rat subcutaneous implantation model. 12 weeks of implantation results in an interconnected porous structure with 82,87% porosity. Cell infiltration and collagen tissue in-growth between microspheres observed by histology confirms the formation of an in situ 3D interconnected porous structure. It is determined that the in situ porous structure results from unique hydrogen bonding in the blend promoting a three-stage degradation mechanism. The robust tissue in-growth of this dynamic pore forming scaffold attests to the utility of this system as a new strategy in regenerative medicine for developing solid matrices that balance degradation with tissue formation. [source]

A Versatile, Molecular Engineering Approach to Simultaneously Enhanced, Multifunctional Carbon-Nanotube, Polymer Composites,

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2006
J. Chen
Abstract Single-walled carbon nanotubes (SWNTs) are recognized as the ultimate carbon fibers for high-performance, multifunctional composites. The remarkable multifunctional properties of pristine SWNTs have proven, however, difficult to harness simultaneously in polymer composites, a problem that arises largely because of the smooth surface of the carbon nanotubes (i.e., sidewalls), which is incompatible with most solvents and polymers, and leads to a poor dispersion of SWNTs in polymer matrices, and weak SWNT,polymer adhesion. Although covalently functionalized carbon nanotubes are excellent reinforcements for mechanically strong composites, they are usually less attractive fillers for multifunctional composites, because the covalent functionalization of nanotube sidewalls can considerably alter, or even destroy, the nanotubes' desirable intrinsic properties. We report for the first time that the molecular engineering of the interface between non-covalently functionalized SWNTs and the surrounding polymer matrix is crucial for achieving the dramatic and simultaneous enhancement in mechanical and electrical properties of SWNT,polymer composites. We demonstrate that the molecularly designed interface of SWNT,matrix polymer leads to multifunctional SWNT,polymer composite films stronger than pure aluminum, but with only half the density of aluminum, while concurrently providing electroconductivity and room-temperature solution processability. [source]

Scaffold Design and Manufacturing: From Concept to Clinic

ADVANCED MATERIALS, Issue 32-33 2009
Scott J. Hollister
Abstract Since Robert Langer and colleagues pioneered the concept of reconstructing tissue using cells transplanted on synthetic polymer matrices in the early 1990s, research in the field of tissue engineering and regenerative medicine has exploded. This is especially true in the development of new materials and structures that serve as scaffolds for tissue reconstruction. The basic tenet of the last two decades holds scaffolds as degradable materials providing temporary function while enhancing tissue regeneration through the delivery of biologics. Although a number of new scaffolding materials and structures have been developed in research laboratories, the application of such materials practice even has been extremely limited. This paper argues that better integration of all these factors is needed to bring scaffolds from "concept to clinic". It reviews current work in all these areas and suggests where future work and funding is needed. [source]

Multicolor Polymer Nanocomposites: In Situ Synthesis and Fabrication of 3D Microstructures,

ADVANCED MATERIALS, Issue 5 2008
Z.-B. Sun
The multiphoton polymerization of CdS,polymer nanocomposites is used to fabricate 3D luminescent structures such as the multicolor "microbull" shown in the figure. The CdS nanoparticles are synthesized in situ within the polymer matrices with their size controlled by the amount of added crosslinker. [source]

Evaluation of the potential of polymeric carriers based on chitosan- grafted -polyacrylonitrile in the formulation of drug delivery systems

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010
A. A. Sarhan
Abstract Graft copolymerization of chitosan with acrylonitrile (AN) was carried out by free radical polymerization using KMnO4 and oxalic acid as a combined redox initiator system. Graft copolymerization was confirmed by Fourier transform infrared spectra (FTIR), proton nuclear magnetic resonance spectra (1H-NMR), thermal gravimetric analysis (TGA) measurements, and wide angle X-ray diffraction (WAXD). In addition, further modification of the cyano groups of the grafted copolymers was performed by partial hydrolysis into carboxylic function groups with various extents. The extent of hydrolysis was monitored using FTIR spectroscopy. The potential of the hydrolyzed and unhydrolyzed grafted copolymers as polymeric carriers for drug delivery systems was extensively studied by preparation of tablets incorporated with methyl orange (MO) as a drug model. In vitro drug release was carried out in simulated gastric and intestinal conditions. The effects of grafting percentage (GP) and the extent of hydrolysis on the release kinetics were evaluated. Release continued up to 24 h for both hydrolyzed and unhydrolysed chitosan- g -PAN copolymers. The nature of drug transport through the polymer matrices was studied by comparing with power law or Kormeyer-Peppas equation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Dispersion of graphite nanosheets in polymer resins via masterbatch technique

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007
Guohua Chen
Abstract The dispersion of graphite nanosheets (GNs) in polymer matrices via the masterbatch technique was investigated. Modifying resin was added to GNs to prepare blend which is designated as the masterbatch. Such masterbatches, containing 70,80 wt % of GN filler, were blended with target polymers via melt extrusion process to prepare polymer/GN nanocomposites. The extruded nanocomposites showed characteristic conducting percolation behaviors with the percolation thresholds mainly dependent on the miscibility of the modifying resin with polymer matrix. The percolation thresholds of AS (Acrylonitrile-Styrene compolymer)/GN and high-density polyethylene (HDPE)/GN nanocomposites prepared by this technique were about 9 and 14 wt % of GN, respectively. Scanning electron microscopy and other characterizations showed that the GNs were well dispersed in AS and HDPE resins. The extrusion process and compatibility of the modifying resin with target polymer proved to be important factors for the homogeneity of the nanodispersion. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3470,3475, 2007 [source]

Hydrothermal and mechanical stresses degrade fiber,matrix interfacial bond strength in dental fiber-reinforced composites

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2006
Serge Bouillaguet
Abstract Fiber-reinforced composites (FRCs) show great promise as long-term restorative materials in dentistry and medicine. Recent evidence indicates that these materials degrade in vivo, but the mechanisms are unclear. The objective of this study was to investigate mechanisms of deterioration of glass fiber,polymer matrix bond strengths in dental fiber-reinforced composites during hydrothermal and mechanical aging. Conventional three-point bending tests on dental FRCs were used to assess flexural strengths and moduli. Micro push-out tests were used to measure glass fiber,polymer matrix bond strengths, and nanoindentation tests were used to determine the modulus of elasticity of fiber and polymer matrix phases separately. Bar-shaped specimens of FRCs (EverStick, StickTech, and Vectris Pontic, Ivoclar-Vivadent) were either stored at room temperature, in water (37 and 100°C) or subjected to ageing (106 cycles, load: 49 N), then tested by three-point bending. Thin slices were prepared for micro push-out and nanoindentation tests. The ultimate flexural strengths of both FRCs were significantly reduced after aging (p < 0.05). Both water storage and mechanical loading reduced the interfacial bond strengths of glass fibers to polymer matrices. Nanoindentation tests revealed a slight reduction in the elastic modulus of the EverStick and Vectris Pontic polymer matrix after water storage. Mechanical properties of FRC materials degrade primarily by a loss of interfacial bond strength between the glass and resin phases. This degradation is detectable by micro push-out and nanoindentation methods. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source]

Removal of fluoride using some lanthanum(III)-loaded adsorbents with different functional groups and polymer matrices

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2003
Luo Fang
Abstract Although fluoride is beneficial for human beings in small quantities, it causes dental fluorosis when consumed in larger quantities over a period of time. In recent years, considerable work has been conducted for the purpose of developing new and low cost absorbents for adsorptive removal of fluoride, especially chelating resins loaded with metal ions. In the present study, several types of adsorbents with different functional groups loaded with lanthanum(III) were prepared to be used for fluoride removal from water. The optimum conditions for loading lanthanum(III) on the adsorbents and the effects of pH and initial fluoride concentration as well as shaking time and solid,liquid ratio on the removal of fluoride have been investigated. Based on these fundamental data, the removal of fluoride from actual hot spring water was also tested as a practical application by comparing the efficiency of different adsorbents for the removal of fluoride from hot spring water. The following conclusions were obtained. (1) The different chemical composition and chemical structure of the polymer matrix play the most important role in fluoride adsorption, (2) strongly acidic adsorbents are more effective on fluoride removal at neutral pH than weakly acidic adsorbents, (3) the order of fluoride removal in the neutral pH range of 4.5,8.0 by the different La(III)-loaded adsorbents employed in the present work is as follows: 200CT resin > POJRgel > IR124resin > SOJR gel , CPAgel , WK11 resin. The column experiments showed that the 200CT resin loaded with lanthanum(III) at pH 6.0 can be successfully employed for the removal of fluoride ions from actual hot spring water. Copyright © 2003 Society of Chemical Industry [source]

Compaction of pharmaceutical tablets with different polymer matrices studied by FTIR imaging and X-ray microtomography

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2008
Patrick Wray
Abstract Water soluble polymers are often used in tablet compaction for their desirable compaction and dissolution properties. ATR-FTIR spectroscopic imaging has been used to analyze in situ the spatial distribution of different components in tablets with different compositions. Caffeine tablets made of three different polymer matrices, microcrystalline cellulose, hydroxypropyl methylcellulose (HPMC) and lactose, were investigated. It was found that the distribution of caffeine is strongly affected by the composition of polymer matrix used in the tablet. X-ray tomography was used to analyze the caffeine distribution as a complementary technique. The results obtained were compared to the ATR-FTIR spectroscopic images. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4269,4277, 2008 [source]

Novel biopolymers as implant matrix for the delivery of ciprofloxacin: Biocompatibility, degradation, and in vitro antibiotic release

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2007
Suniket V. Fulzele
Abstract The purpose of this study was to investigate the in vitro,in vivo degradation and tissue compatibility of three novel biopolymers viz. polymerized rosin (PR), glycerol ester of polymerized rosin (GPR) and pentaerythritol ester of polymerized rosin (PPR) and study their potential as implant matrix for the delivery of ciprofloxacin hydrochloride. Free films of polymers were used for in vitro degradation in PBS (pH 7.4) and in vivo in rat subcutaneous model. Sample weight loss, molecular weight decline, and morphological changes were analyzed after periodic intervals (30, 60, and 90 days) to monitor the degradation profile. Biocompatibility was evaluated by examination of the inflammatory tissue response to the implanted films on postoperative days 7, 14, 21, and 28. Furthermore, direct compression of dry blends of various polymer matrices with 20%, 30%, and 40% w/w drug loading was performed to investigate their potential for implant systems. The implants were characterized in terms of porosity and ciprofloxacin release. Biopolymer films showed slow rate of degradation, in vivo rate being faster on comparative basis. Heterogeneous bulk degradation was evident with the esterified products showing faster rates than PR. Morphologically all the films were stiff and intact with no significant difference in their appearance. The percent weight remaining in vivo was 90.70,±,6.2, 85.59,±,5.8, and 75.56,±,4.8 for PR, GPR, and PPR films respectively. Initial rapid drop in Mw was demonstrated with nearly 20.0% and 30.0% decline within 30 days followed by a steady decline to nearly 40.0% and 50.0% within 90 days following in vitro and in vivo degradation respectively. Biocompatibility demonstrated by acute and subacute tissue reactions showed minimal inflammatory reactions with prominent fibrous encapsulation and absence of necrosis demonstrating good tissue compatibility to the extent evaluated. All implants showed erosion and increase in porosity that affected the drug release. Increase in drug loading significantly altered the ciprofloxacin release in extended dissolution studies. PPR produced drug release >90% over a period of 90 days promising its utility in implant systems. The results demonstrated the utility of novel film forming biopolymers as implant matrix for controlled/sustained drug delivery with excellent biocompatibility characteristics. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96:132,144, 2007 [source]

Ionic liquids in the synthesis and modification of polymers

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2005
Przemys, aw Kubisa
Abstract Ionic liquids are organic salts that are liquid at ambient temperatures, preferably at room temperature. They are nonvolatile, thermally and chemically stable, highly polar liquids that dissolve many organic, inorganic, and metallo-organic compounds. Many combinations of organic cations with different counterions are already known, and the properties of ionic liquids may be adjusted by the proper selection of the cation and counterion. In the last decade, there has been increasing interest in using ionic liquids as solvents for chemical reactions. The interest is stimulated not only by their nonvolatility (green solvents) but also by their special properties, which often affect the course of a reaction. In recent years, ionic liquids have also attracted the attention of polymer chemists. Although the research on using ionic liquids in polymer systems is still in its infancy, several interesting possibilities have already emerged. Ionic liquids are used as solvents for polymerization processes, and in several systems they indeed show some advantages. In radical polymerization, the kp/kt ratio (where kp is the rate constant of propagation and kt is the rate constant of termination) is higher than in organic media, and thus better control of the process can be achieved. Ionic liquids, as electrolytes, have also attracted the attention of researchers in the fields of electrochemical polymerization and the synthesis of conducting polymers. Finally, the blending of ionic liquids with polymers may lead to the development of new materials (ionic liquids may act as plasticizers, electrolytes dispersed in polymer matrices, or even porogens). In this article, the new developments in these fields are briefly discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4675,4683, 2005 [source]

Hybrid metal,polymer composites from functional block copolymers

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2005
Robert B. Grubbs
Abstract The combination of metals and polymers in hybrid materials is a research area of great current interest. A number of methods for controlling the positioning of metallic species within polymer matrices on the nanometer scale have been developed. This highlight focuses on the use of functional block copolymers for the localization of metal species, especially nanoparticles, on the nanometer scale through block copolymer phase segregation. Research from the author's group on the use of alkyne-functional block copolymers for the preparation of cobalt-containing materials is discussed in this context. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4323,4336, 2005 [source]

Chiroptical Properties of Terthiophene Chromophores Dispersed in Oriented and Unoriented Polyethylene Films

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2004
Andrea Pucci
Abstract Summary: Two new chiral terthiophene chromophores II and III were prepared with 99% enantiomeric excess. Chiroptical properties of these dyes dispersed in ultra high molecular weight polyethylene (UHMWPE) films were determined and compared with the same properties in solution. In the solid state, the optical activity strongly depends on the interaction mechanisms within small crystalline aggregates of chromophores. The film morphology and chromophore dispersion were also investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The good correlation between chromophore aggregation and chiroptical activity of the binary films promotes circular dichroism (CD) as an effective technique for monitoring the phase dispersion behaviour of dichroic dyes into polymer matrices. By mechanical stretching of the film a linearly dichroic orientation of the chromophores is obtained which results in a high degree of linear dichroism. The influence of the uniaxial orientation of terthiophene molecules along the drawing direction of UHMWPE on the chiroptical properties of the films, and the possible application of the oriented devices as linear polarizers are discussed. Absorption and CD spectra of unoriented UHMWPEII film at different rotation angles ,. [source]

Raman and Infrared Imaging of Dynamic Polymer Systems

MACROMOLECULAR MATERIALS & ENGINEERING, Issue 7 2007
Jack L. Koenig
Abstract This work reviews principles of Raman and infrared imaging, as well as applications of the art to understand physiochemical phenomena in polymer systems. Image sequences may be assessed in terms of spatial or spectral changes that occur over time, either within a specific region or across the field of view. As such, the methods have enabled the analysis of diffusion and dissolution processes at polymer interfaces, drug release from polymer matrices, and structural transitions among others. Despite analytical limitations imposed by resolution (spectral or spatial) and sample preparation, Raman and infrared imaging are powerful tools for relating performance attributes to molecular-level characteristics. [source]

A Quantum-Mechanical QSAR Model to Predict the Refractive Index of Polymer Matrices

Scaling behavior of plasmon coupling in Au and ReO3 nanoparticles incorporated in polymer matrices

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7 2010
Urmimala Maitra
Abstract Polymer nanocomposites containing different concentrations of Au nanoparticles have been investigated by small angle X-ray scattering and electronic absorption spectroscopy. The variation in the surface plasmon resonance (SPR) band of Au nanoparticles with concentration is described by a scaling law. The variation in the plasmon band of ReO3 nanoparticles embedded in polymers also follows a similar scaling law. Distance dependence of plasmon coupling in polymer composites of metal nanoparticles. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Comparison between laser-induced nucleation of ZnS and CdS nanocrystals directly into polymer matrices

POLYMER COMPOSITES, Issue 6 2010
Athanassia Athanassiou
The nucleation of two kinds of crystalline nanoparticles, zinc sulfide (ZnS), and cadmium sulfide (CdS), is achieved directly into specific sites of polymer matrices after their irradiation with UV laser pulses. The starting samples consist of polymers doped with precursors of Zn or Cd thiolate that are proved to decompose after the absorption of UV light, resulting into the nanoparticles formation. The growth of the crystalline nanostructures is followed throughout the irradiation of the samples with successive incident pulses, by different methods, such as transmission electron microscopy, atomic force microscopy, confocal microscopy, and X-ray diffraction. Special attention is paid to the difference of the formation pathways of the two kinds of nanoparticles studied, because the Cd thiolate precursor exhibits much higher absorption efficiency than the Zn thiolate one, at the applied UV wavelength. Indeed, CdS nanoparticles become evident after the very first incident UV pulses, whereas the formation of ZnS nanocrystals requires rather prolonged irradiation, always through a macroscopically nondestructive procedure for the polymer matrix. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source]

Effect of clay with different cation exchange capacity on the morphology and properties of poly(methyl methacrylate)/clay nanocomposites

POLYMER COMPOSITES, Issue 11 2009
Tsung-Yen Tsai
PMMA/clay nanocomposites were successfully prepared by in situ free-radical polymerization with the organic modified MMT-clay using methyl methacrylate monomer and benzoyl peroxide initiator. Two clays with different cation exchange capacity have been used to prepare and compare the several properties. The clays have been modified using Amphoterge K2 by ion exchange reaction to increase the compatibility between the clay and polymer matrices. The modified clays have been characterized by wide-angle X-ray diffraction pattern, Fourier transform infrared spectroscopy, and thermogravimetric analysis (TGA). The powdered X-ray diffraction and transmission electron microscopy techniques were employed to study the morphology of the PMMA/clay nanocomposites which indicate that the modified clays are dispersed in PMMA matrix to form both exfoliated and intercalated PMMA/modified clay nanocomposites. The thermomechanical properties were examined by TGA, differential scanning calorimetry, and dynamic mechanical analysis. Gas permeability analyzer shows the excellent gas barrier property of the nanocomposites, which is in good agreement with the morphology. The optical property was measured by UV,vis spectroscopy which shows that these materials have good optical clarity and UV resistance. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source]

Electrical and mechanical properties of multi-walled carbon nanotubes reinforced PMMA and PS composites

POLYMER COMPOSITES, Issue 7 2008
R.B. Mathur
The use of multi-walled carbon nanotubes (MWCNT) as reinforcing material for thermoplastic polymer matrices, polymethyl methacrylate (PMMA), and polystyrene (PS) has been studied. MWCNT were synthesized by chemical vapor deposition (CVD) technique using ferrocene-toluene mixture. As-prepared nanotubes were ultrasonically dispersed in toluene and subsequently dispersed in PMMA and PS. Thin polymer composite films were fabricated by solvent casting. The effect of nanotube content on the electrical and mechanical properties of the nanocomposites was investigated. An improvement in electrical conductivity from insulating to conducting with increasing MWCNT content was observed. The carbon nanotube network showed a classical percolating network behavior with a low percolation threshold. Electromagnetic interference (EMI) shielding effectiveness value of about 18 dB was obtained in the frequency range 8.0,12 GHz (X-band), for a 10 vol% CNT loading. An improved composite fabrication process using casting followed by compression molding and use of functionalized MWCNT resulted in increased composites strength. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source]

Characterization and design of interphases in glass fiber reinforced polyproplyene

POLYMER COMPOSITES, Issue 3 2000
E. Mäder
Bond strength between reinforcing fibers and polymer matrices can be controlled in two ways: 1) by intensification of molecular interaction at the interface and 2) by creation of a strong transition layer (interphase) between the components. In this paper, we consider the possibilities of controlling interfacial strength by means of target-oriented variation of structure, thickness and strength of the interphase artificially created between the glass fiber and the polypropylene matrix. The bond strength was measured using a continuously monitored microbond test, including recording the crack length as a function of the load applied. The measured interfacial strengths correlated to the macromechanical properties of glass fiber reinforced polypropylene. The interphase design provided simultaneous increase in the tensile strength and the impact toughness of the composites. [source]

Preparation and characterization of polyurethane,gold nanocomposites prepared using encapsulated gold nanoparticles

POLYMER INTERNATIONAL, Issue 7 2010
Chao-Ching Chang
Abstract Gold nanoparticles (GNPs) have been widely studied due to their unique properties. Although many research groups have developed the synthesis of GNPs using various polymers as stabilizing or reducing agents, the effects of GNPs on the structures and properties of polymer matrices have been less reported. We propose a new design for the preparation of polyurethane,gold (PU,Au) nanocomposites. 11-Mercapto-1-undecanol-coated GNPs acted as the chain extenders and reacted with isocyanates to form covalent bonds between PU and GNPs. PU,Au nanocomposites were successfully synthesized, and the effects of multifunctional GNPs on the structures, morphology and properties of poly(ester urethane) were investigated. Scanning electron microscopy images suggested the GNPs can be dispersed uniformly in the PU matrix. Maltese-cross of spherical crystals was observed in the PU,Au nanocomposites, and the size of the crystals decreased with an increase in gold content. As the gold content increased, the thermal decomposition temperature and the temperature of the maximum decomposition rate increased. The glass transition temperature, crystal melting temperature and melting enthalpy of the soft segment also increased progressively. The results showed that multifunctional GNPs concentrated hard segments and resulted in an increase of heterogeneous nucleation, phase separation and elasticity. Copyright © 2010 Society of Chemical Industry [source]