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Low-molecular-weight Poly (low-molecular-weight + poly)
Selected AbstractsLow-Molecular-Weight Poly(, -methyl ,,L -malate) of Microbial Origin: Synthesis and CrystallizationMACROMOLECULAR BIOSCIENCE, Issue 2 2005Carlos E. Fernández Abstract Summary: Low-molecular-weight poly(, -methyl ,,L -malate) made of approximately 25,30 units was prepared from microbial poly(,,L -malic acid) by treatment with diazomethane. The thermal characterization of the polymalate methyl ester was carried out and its crystalline structure was preliminary examined. Its ability to crystallize both from solution and from the melt was comparatively evaluated. Poly(, -methyl ,,L -malate) spherulitic film cast from CHCl3. [source] Synthesis and physical properties of low-molecular-weight redistributed poly(2,6-dimethyl-1,4-phenylene oxide) for epoxy resinJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Hann-Jang Hwang Abstract Low-molecular-weight poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was prepared by the redistribution of regular PPO with 4,4,-isopropylidenediphenol (bisphenol A) with benzoyl peroxide as an initiator in toluene. The redistributed PPO was characterized by proton nuclear magnetic resonance, mass spectra, and Fourier transform infrared spectroscopy. The redistributed PPO oligomers with terminal phenolic hydroxyl groups and low molecular weights (weight-average molecular weight = 800,4000) were used in the modification of a diglycidyl ether of bisphenol A/4,4,-diaminodiphenylmethane network system. The curing behaviors were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The effect of molecular weight and the amount of redistributed PPO oligomers incorporated into the network on the physical properties of the resulting systems were investigated. The thermal properties of the cured redistributed PPO/epoxy resins were studied by dynamic mechanical analysis, thermal mechanical analysis, thermogravimetric analysis, and dielectric analysis. These cured redistributed PPO/epoxy resins exhibited lower dielectric constants, dissipation factors, coefficients of thermal expansion, and moisture absorptions than those of the control diglycidyl ether of bisphenol A based epoxy. The effects of the composition on the glass-transition temperature and thermal stability are discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Low-Molecular-Weight Poly(, -methyl ,,L -malate) of Microbial Origin: Synthesis and CrystallizationMACROMOLECULAR BIOSCIENCE, Issue 2 2005Carlos E. Fernández Abstract Summary: Low-molecular-weight poly(, -methyl ,,L -malate) made of approximately 25,30 units was prepared from microbial poly(,,L -malic acid) by treatment with diazomethane. The thermal characterization of the polymalate methyl ester was carried out and its crystalline structure was preliminary examined. Its ability to crystallize both from solution and from the melt was comparatively evaluated. Poly(, -methyl ,,L -malate) spherulitic film cast from CHCl3. [source] The Formation of Ordered Nanoholes in Binary, Chemically Similar, Symmetric Diblock Copolymer Blend Films,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 12 2004Yu Xuan Abstract Summary: Binary symmetric diblock copolymer blends, that is, low-molecular-weight poly(styrene- block -methyl methacrylate) (PS- b -PMMA) and high-molecular-weight poly(styrene- block -methacrylate) (PS- b -PMA), self-assemble on silicon substrates to form structures with highly ordered nanoholes in thin films. As a result of the chemically similar structure of the PMA and the PMMA block, the PMMA chain penetrates through the large PMA block that absorbs preferentially on the polar silicon substrate. This results in the formation of nanoholes in the PS continuous matrix. An atomic force microscopy image of the thin film obtained from the blend of low-molecular-weight PS- b -PMMA and high-molecular-weight PS- b -PMA. The regular array of nanoholes in the films surface is clearly visible. [source] | ||||||||||