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Biodegradable poly(tert-butyl acrylate)-poly[(R)-3-hydroxybutyrate]-poly (tert-butyl acrylate) triblock copolymers based on bacterial poly[(R)-3-hydroxybutyrate] (PHB) were synthesized by atom transfer radical polymerization. The chain architectures of the triblock copolymers were confirmed by 1 H NMR and 13 C NMR spectra. Gel permeation chromatography analysis was used to estimate the molecular weight characteristics and lengths of the PHB and poly(tert-butyl acrylate) blocks of the copolymers. The thermal properties of the copolymers were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA showed that the triblock copolymers underwent stepwise thermal degradation and had better thermal stability than their respective homopolymers, whereas DSC analyses showed that a microphase-separation structure was formed only in the triblock copolymers with the longer PHB block. As a similar result, from wide-angle X-ray diffraction experimentation, the crystalline phase of PHB could not be seen evidently in the triblock copolymers with the shorter PHB block. The enzymatic hydrolysis of the copolymer films was carried at 37 8C and pH 7.4 in a potassium phosphate buffer with an extracellular PHB depolymerase from Penicillum sp. The biodegradability of the triblock copolymers increased with an increase in the PHB block content. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4857-4869, 2005

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ABSTRACT:The thermal properties of carbon nanofibers (CNF)/epoxy composites, composed of tetraglycidyl-4,4Ј-diaminodiphenylmethane (TGDDM) resin and 4,4Ј-diaminodiphenylsulfone (DDS) as a curing agent, were investigated with differential scanning calorimetry (DSC), thermogravimetric analysis, and dynamic mechanical thermal analysis. DSC results showed that the presence of CNF had no pronounced influence on the heat of the cure reaction. However, the incorporation of CNF slightly improved the thermal stability of the epoxy. Furthermore, the storage modulus of the TGDDM/ DDS epoxy was significantly enhanced, whereas the glasstransition temperature was not significantly affected, upon the incorporation of CNFs. The storage modulus of 5 wt % CNF/ epoxy composites at 25°C was increased by 35% in comparison with that of the pure epoxy.