Thermal Properties of Maleated Polyethylene/Layered Silicate Nanocomposites

Nanocomposites are a new class of composites in which the reinforcing phase dimensions are on the order of nanometer scale. In particular, the layered silicates are considered to be good candidates for the preparation of polymer-inorganic nanocomposites. The mechanical and thermal properties of polymer can be altered by adding a few vol% of the nano-particles. The effect of the nano-sized particles on thermophysical properties such as melting and crystallization, coefficient of thermal expansion, and thermal conductivity was studied. After preparing the PEMA/layered silicate nanocomposites, the thermophysical properties were investigated by the differential scanning calorimetry and 3 methods. The content of layered silicate was varied from 0.5 to 5 vol%.     

Characterization of fatigue resistance in photochromic composite materials for 3D rewritable optical memory applications

Fatigue resistance of the photochromic diarylethene molecules 1,2-bis[2-methylbenzo[b]thyophen-3-yl]-3,3,4,4,5,5-hexafluoro-1-cyclopentene embedded in three different acrylic polymers is studied upon multiple coloration–decoloration cycles. The resistance to photofatigue is found to be different in the three polymeric materials when one-photon excitation was used for the reversible photoconversion experiment. In particular, the photochromic molecules lose their photoisomerization ability faster if they are embedded in poly(methyl methacrylate) (PMMA) with respect to poly(ethyl methacrylate-co-methyl acrylate) (PEMMA) and poly(ethyl methacrylate) (PEMA). We propose several explanations based on the physico-chemical properties of the matrix and of the photochromic molecules. In the case of two-photon excitation, which is necessary for 3D optical writing, the fatigue resistance is found to be poorer than in the one-photon case. The accelerated photodegradation can be assigned to the non-linear nature of interaction between the polymeric composite material and light.     

Synthesis, Characterization and Reactivity Ratios of Phenylethyl Acrylate/Methacrylate Copolymers

2-Phenylethyl acrylate (PEA) and 2-Phenylethyl methacrylate (PEMA) were synthesized by reacting 2-Phenyl ethanol with acryloyl and methacryloyl chloride respectively. Homopolymers and copolymers were prepared by free radical polymerization technique using benzoylperoxide as initiator. Copolymers of PEA and PEMA with methyl acrylate (MA) and N-vinyl pyrollidone (NVP) of different compositions were prepared. The monomers and polymers were characterized by IR and NMR techniques. Thermal stability of the polymers were determined by TG analysis. The composition of the copolymer was determined using ¹H-NMR analysis. The reactivity ratios of the monomers were determined by the application of Finemann–Ross and Kelen–Tudos methods. The prepared copolymers were tested on leather for their pressure sensitive adhesive property.     

Studies on the effect of anions of various lithium salts in PEMA gel polymer electrolytes

This research synthesized graft copolymers of chitosan‐g‐poly(N‐isopropyl acrylamide) (CS‐g‐PNIPAAm) by UV‐initiated free‐radical polymerization of NIPAAm monomer to CS selectively at the C‐6 position of pyranose ring. First, amino groups in CS were protected by reaction with phthalic anhydride (PA) to form PACS. The degree of phthaloylation was carefully controlled to ensure that most amino groups were protected, and only a very small amount of hydroxyl groups were reacted. In the second step, the vinyl functional group was introduced to the PACS by reaction with a vinyl compound containing an isocyanate group (3‐isopropenyl‐αα′‐dimethylbenzyl isocyanate), through the urethane linkage with hydroxyl groups at the C‐6 position. The phthaloyl groups were then removed by hydrazine to recover the amino groups in CS. Finally, PNIPAAm was grafted to the vinyl CS at the C‐6 position by UV‐initiated free‐radical polymerization. The synthesized CS‐g‐PNIPAAm copolymers were confirmed to have a structure of an AB‐crosslinked graft copolymer. Respectively, these copolymer hydrogels exhibited pH‐ and thermal‐responsive swelling properties in an aqueous solution due to their CS and PNIPAAm components. The test of cell viability with L929 fibroblast revealed that the CS‐g‐PNIPAAm copolymers having a grafting ratio lower than 1.7 had cellular compatibility as good as pure CS. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Nano ZrO2 reinforced cellulose incorporated polyethylmethacrylate/polyvinyl alcohol composite films as semiconducting packaging materials

A simple in situ polymerization process is used to synthesize nanocomposite films with incorporation of cellulose and nano ZrO₂ (PEMA/PVA-C@ZrO₂). The change in structural, morphological, and functional properties are noticed due to combine effect of cellulose and zirconia which is studied by FTIR, XRD, XPS, FESEM, HRTEM, DLS, and AFM. The distribution of particle in the film is determined from dynamic light scattering (DLS). It is found that, dielectric permittivity is increased with percolation at 3 wt% of the nano ZrO₂. Further, the dielectric permittivity (ε') value is found to be 110 at 1 Hz with a low dielectric loss (Tan δ = 1.74) and an optimum dielectric permittivity is 172 at 1 Hz for 4 wt% loading of nano ZrO₂. Mechanical and thermal characteristics of the as-synthesized films are improved due to interfacial adhesion between zirconia and polymeric matrix. The chemical resistance, biodegradable characteristics, and refractive index of the nanocomposite films are also measured. It is noticed that, the barrier properties are increased by 20-folds due to the synergistic combination of nano ZrO₂ and cellulose with polymeric matrix. The enhancement in barrier properties with improved dielectric permittivity can enable the as-synthesized films for semiconducting packaging applications.     

Ceramic and polymeric solid electrolytes for lithium-ion batteries

Lithium-ion batteries are important for energy storage in a wide variety of applications including consumer electronics, transportation and large-scale energy production. The performance of lithium-ion batteries depends on the materials used. One critical component is the electrolyte, which is the focus of this paper. In particular, inorganic ceramic and organic polymer solid-electrolyte materials are reviewed. Solid electrolytes provide advantages in terms of simplicity of design and operational safety, but typically have conductivities that are lower than those of organic liquid electrolytes. This paper provides a comparison of the conductivities of solid-electrolyte materials being used or developed for use in lithium-ion batteries.     

Telechelic polymers by living and controlled/living polymerization methods

Telechelic polymers, defined as macromolecules that contain two reactive end groups, are used as cross-linkers, chain extenders, and important building blocks for various macromolecular structures, including block and graft copolymers, star, hyperbranched or dendritic polymers. This review article describes the general techniques for the preparation of telechelic polymers by living and controlled/living polymerization methods; namely atom transfer radical polymerization, nitroxide mediated radical polymerization, reversible addition-fragmentation chain transfer polymerization, iniferters, iodine transfer polymerization, cobalt mediated radical polymerization, organotellurium-, organostibine-, organobismuthine-mediated living radical polymerization, living anionic polymerization, living cationic polymerization, and ring opening metathesis polymerization. The efficient click reactions for the synthesis of telechelic polymers are also presented.     

Structural and Mechanical Studies of In-Situ Generated Poly(vinlylidene fluoride) Particle Comprising Poly(ethylmethacrylate) and Poly(methylmethacrylate) Ternary Films

The poly(vinlylidene fluoride) (PVDF) was incorporated within the compound matrix of poly(ethylmethacrylate) (PEMA)/poly(methylmethacrylate) (PMMA) using solution cast technique. The importance of PVDF in the miscibility of PEMA/PMMA matrix was investigated using FT-IR, DSC, SEM and AFM technique. Crystalline particle size of PVDF in PEMA/PMMA matrix was analyzed using XRD characterization. Single-phase compatibility with maximum crystallinity along with the maximum value of hardness was observed when PVDF/PMMA/PEMA were blended in equal weight ratio. The PVDF particle act as reinforcing material within the compound matrix of PEMA/PMMA, and hence, improves the properties of prepared ternary blends.     

Miscibility enhancement on the immiscible poly (vinyl pyrrolidone) and poly (ethyl methacrylate) with poly (vinyl phenol)

The miscibility behavior of ternary blends of poly (vinyl phenol) (PVPh)/poly (vinyl pyrrolidone) (PVP)/poly (ethyl methacrylate) (PEMA) was investigated mainly with calorimetry. PVPh is miscible with both PVP and PEMA on the basis of the single T_g observed over the entire composition range. FTIR was used to study the hydrogen bonding interaction between the hydroxyl group of PVPh and the carbonyl group of PVP and PEMA at various compositions. Furthermore, the addition of PVPh is able to enhance the miscibility of the immiscible PVP/PEMA and eventually transforms it into a miscible blend, especially when the ratio between PVP/PEMA is 3:1, probably because of favorable physical interaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1205–1213, 2006     

金属穿甲杆或射流受被动电磁装甲电磁力作用物理模型

电磁装甲技术是一项新概念战斗车辆防护技术。首次明确提出了应用电磁力理论原理分析电磁装甲的问题,利用电磁学的理论推导出系统在加电工作状态下射弹受力方程,建立了被动电磁装甲( PEMA)的物理模型,并对其进行计算机仿真。