Physical Properties Of Polymers Research Articles

Characterization of biocompatible fungi-derived polymers that induce IL-8 production

Sixteen strains of fungi from 15 different genera were isolated from natural habitats in Thailand to study their biopolymers. Polymer production, chemical composition, and physical and biological properties related to their potential as wound dressing materials were investigated. All polymers were shown to be composed of polysaccharides except those produced from Fusarium coccophilum BCC2415 which was a protein–polysaccharide complex. Molecular weights of the polymers ranged from 2.8×10 3–1.2×10 7 Da. Apart from the polymers from Fusarium coccophilum BCC2415 and Cordyceps dipterigena BCC2073 that were only water soluble, those from other fungi were soluble in both water and DMSO. Different biological assays including cytotoxicity tests were conducted to investigate their biocompatibility. To evaluate the potential of these polymers as wound dressing material, the level of interleukin (IL)-8 produced by normal human dermal fibroblasts (NHF) cells exposed to the polymers were determined. Our results indicated that polymers produced by Akanthomyces pistillariiformis BCC2694, Cordyceps dipterigena BCC2073, Paecilomyces tenuipes BCC2656, and Phytocordyceps sp. BCC2744 were biocompatible and inducers of high levels of IL-8.

Physical Properties of Polymers

Physical Properties of Polymers

Recent advances in microbial polyhydroxyalkanoates

Polyhydroxyalkanoates (PHAs) are polyesters of hydroxyalkanoates (HAs) synthesised by numerous bacteria as an intracellular carbon and energy storage compound. These are accumulated in the cytoplasm of cells. A number of bacteria including Alcaligenes, Pseudomonas, recombinant Escherichia coli and methylotrophs have been used for the production of PHAs and high productivities have been achieved. Production of PHA by transgenic plants has been demonstrated on a laboratory-scale and large-scale production will be feasible in the near future. By controlling the monomer composition of PHA, it has been indicated that the physical properties of polymers can be regulated to a great extent. Even though PHAs have been recognised as a good candidate for biodegradable polymers, their high production cost limits their industrial application. It is hoped that with improvement in fermentation and downstream processing techniques, development of new recombinant strains and large-scale production by transgenic plants will reduce the cost of production of PHAs thereby making them competitive with conventional plastics.

自己組織化マップを用いたニューラルネットワークによる高分子物性予測(OS4b 逆問題解析手法の開発と最新応用)

自己組織化マップを用いたニューラルネットワークによる高分子物性予測(OS4b 逆問題解析手法の開発と最新応用)

Effects of Severe Plastic Deformation on the Structure and Physical Properties of Polymers

Effects of Severe Plastic Deformation on the Structure and Physical Properties of Polymers

223 制振のからくり : 第 2 報制振材料の機能 : 材料と力学の掛橋

Damping mechanism of polymer material is introduced in this paper easily to understand for mechanical engineers. First, dynamical characteristics common to polymer materials are related. Second, mechanism of joint combination is presented which causes these characteristics. Third, physical properties of polymer in glass region and in rubber region are introduced. Forth, the reason why polymer reveals exceedingly high damping effectives is explained. Fifth, notice points for successive application of damping material to machines for decrease of their vibration are given.

Theoretical and Predictive Modelling of Physical Properties of Polymers

The application of Boltzmann statistics to a complete distribution of molecular conformation energies of simplified homo- and copolymer models gives meaningful information about temperatures at which phase transitions take place in the bulk. We have calculated in the conformation statistical distribution (CSD) approximation Helmholtz free energy variation versus temperature δF = δU-TδS. where U and S are, respectively, the internal molecular energy and the Gibbs statistical entropy of the considered polymeric model. The deepest minima correspond to glass-transition temperature (T g ) and melting temperature (T m ) of modelled polymers, while the remaining peaks are relied to some other transitions, the existence of which is also experimentally proven. The adopted method is able to give T g and T m as a function of the molecular weight of polymers. Some indications can also be achieved about the instability of polymers. The same procedure has been applied to copolymers and blends and has given acceptable results for T g and T m as functions of the material microstructure and composition. Other thermal and mechanical properties, such as moduli, mobilities, chemical resistance to oxidation, physical tendency to miscibility, have been directly or indirectly estmated.

Reduction in surface resistivity of polymers by plasma source ion implantation

The surface resistivity of several polymers such as poly(styrene/butadiene copolymer), modified poly(phenyleneoxide), poly(ethylene terephthalate), and polyimide was improved by the argon gas plasma source ion implantation (Ar-PSII) technique equipped with a mesh-type conducting grid. With the grid, the surface resistivities of the modified polymers decreased up to 11 orders of magnitudes at a high ion dose, and remained nearly at the same values after 3 months. The PSII treated polymer sample with the grid provided more uniformly modified surface and lower surface resistivity than that treated without the grid. The extent of the decrease in surface resistivity depended on the polymer structures and physical properties. However, the surface resistivity was independent of the sample thickness, the grid size, and the grid height. Surface analyses using scanning electron microscopy, time-of-flight secondary ion mass spectrometry, and Raman spectroscopy provided the useful information on modified surfaces.

A Statistical Approach to the Effect of Sol-Gel Process Variables on the Physical Properties of Polymer [PLLA]-Silica Hybrid Materials for Use as Biomaterials

AbstractHybrid poly(L-lactic acid)-silica materials for potential use in orthopaedic applications have been prepared by a sol-gel method using an experimental design approach to investigate the effect of synthesis variables separately and together on the physical form of the organic polymer. The five factors investigated were the molar ratios of tetraethyl orthosilicate (TEOS)/Poly(Llactic acid) (PLLA), Toluene/PLLA, EtOH/TEOS, Water/TEOS and HCl (catalyst)/TEOS. All other synthesis conditions were kept constant. X-Ray powder diffraction (Statton's graphical method) and differential scanning calorimetry were used to assess the extent of polymer crystallinity in the hybrid materials. In accordance with other studies, increasing the molar ratio of TEOS/PLLA lead to increasing incorporation of the organic polymer into the silica network. Increase of the toluene/PLLA molar ratio lead to an increase in the crystallinity of the polymer phase. As our studies investigated the effect of synthesis variables simultaneously it was possible to identify, for the first time, that interactions between specific reactants are important in the development of the two structural components of this hybrid system. The most important of these was the TEOS/PLLA*H2O/TEOS interaction that may indicate that silica species from hydrolysed TEOS interact with the PLLA phase possibly via hydrogen bonding and leads to the lowering of the crystalline order of the polymer The results from this study give useful information on the ability of the organic polymer and the silica phase to form interpenetrating networks, an important requirement for the generation of a potential hybrid polyester-silica biomaterial for orthopaedic applications.

Synthesis and properties of copolyimides containing naphthalene group

Several series of copolyimides were synthesized from various ratios of two diamines with aromatic tetracarboxylic dianhydrides through thermal imidization process to determine the effect of naphthalene ring on the physical properties of polymers. The copolyimides were characterized using inherent viscosity, differential scanning calorimetry (DSC), TGA, DMA, TMA and dielectric analyzer. DSC showed only a T g and exhibited that the copolyimides had a low entropy, amorphous state and formed random polymers. They retained high modulus even at high temperatures by DMA, and had measured coefficients of thermal expansion in the range of 15–57 ppm by TMA. The glass transition temperatures ( T g) of all polymers were found to be 287–321 °C by DSC. Their decomposition temperatures at 10% weight loss in nitrogen atmospheres were above 556 °C. These polymer films had dielectric constants ranging from 2.9 to 3.4 with moisture absorptions of less than 2.65%.

The use of light scattering for precise characterization of polymers for DNA sequencing by capillary electrophoresis

The ability of a polymer matrix to separate DNA by capillary electrophoresis (CE) is strongly dependent upon polymer physical properties. In particular, recent results have shown that DNA sequencing performance is very sensitive to both the average molar mass and the average coil radius of the separation matrix polymers, which are affected by both polymer structure and polymer-solvent affinity. Large polymers with high average molar mass provide the best DNA sequencing separations for CE, but are also the most challenging to characterize with accuracy. The methods most commonly used for the characterization of water-soluble polymers with application in microchannel electrophoresis have been gel permeation chromatography (GPC) and intrinsic viscosity measurements, but the limitations and potential inaccuracies of these approaches, particularly for large or novel polymers and copolymers, press the need for a more universally accurate method of polymer molar mass profiling for advanced DNA separation matrices. Here, we show that multi-angle laser light scattering (MALLS) measurements, carried out either alone or in tandem with prior on-line sample fractionation by GPC, can provide accurate molar mass and coil radius information for polymer samples that are useful for DNA sequencing by CE. Wider employment of MALLS for characterization of novel polymers designed as DNA separation matrices for microchannel electrophoresis should enable more rapid optimization of matrix properties and formulation, and assist in the development of novel classes of polymer matrices.

Piezo‐ and pyroelectric photothermal characterization of polymers as a function of temperature

AbstractIn this article, piezo‐ and pyroelectric signals are used for the photothermal characterization of the thermomechanical properties of polymers as a function of temperature. The potentialities of the proposed technique are explored using poly(ethylene terephthalate) as the test sample. The influence of the sample thermal aging on the polymer physical properties is also discussed. The sensitivity of the proposed photothermal technique is tested by comparing its results with complementary dielectric response measurements and X‐ray diffraction. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2669–2678, 2001

The Entropic Mechanism of Water Solvation of Polymers

Computational analysis of isotherms of equilibrium water absorption by polymers indicates the isotherms follow the theory of volume-centered filling of micropores regardless of the hydrophilicity of polymers. Structure of a microporous adsorbent, absent in the initial state, is formed through reorganization of chains of the molecular-chain sponge during adsorption. Thus, a part of chain units is combined in micropores isolating water molecules as clusters, and another part is redistributed around the clusters as a fringe that stabilizes the system by increasing the configuration entropy. The problem of the physical state of sorbed water in polymers is important from positions of the mechanisms of its diffusion in polymeric membranes, its effect on physical properties of polymers, participation in dyeing and fading of fabrics, superseding of stabilizers and plasticizers, and also in guided delivering of drugs in the organism from polymeric units of medical use.

Synthesis and characterization of accordion main-chain azo-dye polymers for second-order optical non-linearity

New type accordion polymers with azo-dye chromophores as the major segments (up to 70% by weight) of the main chain for second optical non-linearity (NLO) are designed and synthesized by the Knoevenagel polycondensation between bis(carboxaldehyde) containing azobenzene and bis(cyanoacetate) comonomers. Several important properties for NLO application, such as solubility and thermal stability, are investigated, and the effects of linkage groups on the physical properties of polymers are also discussed in some detail. Poled films of one of these polymers show a relatively high resonant d33 value of 33 pm V−1 by second harmonic generation (SHG) measurement, and their order parameter, which is determined to be 0.20 by UV–vis measurement, keep almost constant for 240 h at ambient temperature. © 2000 Society of Chemical Industry

Aromatic/cycloaliphatic polyimides and polyamide-imide from trans-1,4-cyclohexane diisocyanate: synthesis and properties

Mixed aromatic/alicyclic polyimides were prepared by polycondensation reactions of trans-1,4-cyclohexane diisocyanate (CHDI) with pyromellitic dianhydride (PMDA), benzophenonetetracarboxylic dianhydrid (BTDA), and hexafluoroisopropylidene diphthalic anhydride (6FDA). Also, polycondensation of CHDI with trimellitic anhydride led to synthesis of polyamide-imide. In order to obtain the optimized condition for polymerization reactions, model compound studying was considered. Model compound and polymers were characterized by common methods. Physical properties of polymers, including thermal behavior, thermal stability, solution viscosity, and solubility behavior, were also studied. Mild polymerization condition was the main advantage of using diisocyanate instead of diamine in synthesis of these thermally stable polymers. Furthermore, synthesis of poly(amic acid) and polyimide via nonaromatic diamine can introduce synthetic problems, but by applying nonaromatic diisocyanate a facile method for preparation of aromatic/cycloaliphatic polyimides was obtained. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1102–1107, 2000

Preparation and properties of polyimides and polyamide-imides from diisocyanates

Polyimides of different structures were synthesized by reaction of 1,4-phenylene diisocyanate (PPDI) and 1,5-naphthalene diisocyanate (NDI) with pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA). Polyamide-imides were also prepared by reaction of PPDI and NDI with trimellitic anhydride. The optimized condition for polymerization reactions were obtained via the study of model compounds. All polymers and model compounds were characterized by conventional methods. Physical properties of polymers, including thermal behavior, thermal stability, solution viscosity, and solubility behavior, were also studied. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2245–2250, 1999

Transformation of industrial food wastes into polyhydroxyalkanoates

Due to the synthetic and biologically inert nature of petroleum-derived plastics, the disposal of these solid wastes has been a focus of concern for waste management. Thus, the demand for biodegradable plastics has become a highly visible issue. Broader usage of biodegradable plastics in packaging and disposable products as a solution to environmental problems would heavily depend on further reduction in costs and the discovery of novel biodegradable plastics with improved properties. As the first step in pursuit of eventual usage of industrial food wastewater as nutrients for microorganisms to synthesize environmental-friendly bioplastics, the usage of soya wastes and malt wastes from a beer brewery plant were investigated as the carbon sources for the production of bioplastics. Bench experiments showed that microorganisms from the municipal activated sludges used the nutrients from malt and soya wastes to biosynthesise PHAs. The results of experiments indicated that with the proper selection of the type of food wastes as the carbon source, bioplastics with specific PHAs copolymers could be produced with distinct polymer physical properties.

A simulation study on the effects of particle size on the consolidation of polymer powder impregnated tapes

Abstract The powder prepreg technique offers a low-cost, high-speed method of manufacture of composites. Consolidation of the prepreg tows is a key step in the manufacture of a final `useful' part. The efficiency of the consolidation for any polymer powder prepreg tape produced from powder prepreg processes would conceivably depend on the material properties of the polymer, particle size, temperature, consolidation pressure and volume fraction of the tape. A mathematical process model that identifies and describes a set of parameters to predict the consolidation conditions of a given polymer powder prepreg tape has been developed. A simulation study that identifies the different parameters and compares the advantages and limitations of polymer physical properties and particle size has been performed. An integrated Flow Resistance (FR) index has been developed to mathematically describe the consolidation process. The results show that small powder particle sizes are beneficial to the process.

Transformation of industrial food wastes into polyhydroxyalkanoates

Due to the synthetic and biologically inert nature of petroleum-derived plastics, the disposal of these solid wastes has been a focus of concern for waste management. Thus, the demand for biodegradable plastics has become a highly visible issue. Broader usage of biodegradable plastics in packaging and disposable products as a solution to environmental problems would heavily depend on further reduction in costs and the discovery of novel biodegradable plastics with improved properties. As the first step in pursuit of eventual usage of industrial food wastewater as nutrients for microorganisms to synthesize environmental-friendly bioplastics, the usage of soya wastes and malt wastes from a beer brewery plant were investigated as the carbon sources for the production of bioplastics. Bench experiments showed that microorganisms from the municipal activated sludges used the nutrients from malt and soya wastes to biosynthesise PHAs. The results of experiments indicated that with the proper selection of the type of food wastes as the carbon source, bioplastics with specific PHAs copolymers could be produced with distinct polymer physical properties.

The Effect of Conformational Rigidity on Several Physical Properties of Polymers

The phenomenological dependences of several physical properties such as the softening temperature, friction coefficient, elasticity modulus, fire-resistance parameters and quantum luminescence yield on the conformational rigidity of a polymeric chain are revealed for polyheteroarylenes. The contribution of the conformational rigidity of a polymer chain to the physical properties of this class of polymers is shown to be significant. It should be taken into account in estimation of the above-mentioned properties together with the contribution of intermolecular interactions.