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The thermal degradation behaviors of biodegradable poly(3-hydroxybutyrate) (PHB) and PHB/poly(ethylene glycol) phosphonates (PEOPAs)-modified layered double hydroxide (PMLDH) nanocomposites have been investigated using thermogravimetric analysis. Effects of PMLDH contents on the isothermal degradation kinetics of PHB were explored. These experimental results show that the degradation kinetics of PHB/PMLDH nanocomposites is the chain-scission process of cyclic β-elimination reaction with the following autocatalytic reactions, which is very similar to that of pure PHB matrix. Further calculated data based on the autocatalytic model can fit very well with the experimental data. The Ea value of PHB/PMLDH nanocomposites is increased as the content of PMLDH increases. This can be attributed to the incorporation of more PMLDH loading to PHB induced a decrease in the degradation rate and an increase in the residual weight for PHB/PMLDH nanocomposites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1207–1213, 2008

X-ray diffraction method and differential scanning calorimetry analysis have been used to investigate the nonisothermal crystallization of poly(3-hydroxybutyrate) (PHB)/poly(ethylene glycol) phosphonates (PEOPAs)-modified layered double hydroxide (PMLDH) nanocomposites. Effects of cooling rates and PMLDH contents on the nonisothermal crystallization behavior of PHB were explored. These results show that the addition of 2 wt % PMLDH into PHB caused heterogeneous nucleation increasing the crystallization rate and reducing the activation energy. By adding PMLDH into the PHB probably hinder the transport ability of the molecule chains and result in a decreasing crystallity of PHB, thus increasing the activation energy. The correlation among melting behavior, apparent crystallite size, and paracrystalline distortion of PHB/PMLDH nanocomposites has been also discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 995–1002, 2007

The biodegradable polymers, poly(3-hydroxybutyrate) (PHB), have attracted more attention due to its renewable resources, thermoplastic and outstanding physical and mechanical properties close to those of isotactic polypropylene [1]. A new promising class of inorganic layered material, layered double hydroxides (LDH), has been considered as emerging host-guest materials [2]. PHB/LDH nanocomposites were prepared by mixing PHB and PEOPA-modified LDH (PMLDH) in chloroform solution [3]. Both X-ray diffraction data and TEM micrographs of PHB/PMLDH nanocomposites indicate that the PEOPA-modified LDHs are randomly dispersed and exfoliated into the PHB matrix. In this study, the effect of PMLDH on the isothermal crystallization behavior of PHB was investigated using a differential scanning calorimeter and polarized optical microscopy. Mechanical properties of the fabricated nanocomposites measured by dynamic mechanical analysis (DMA) show significant improvements in the storage modulus when compared to that of neat PHB.

For neutral poly(3-alkylthiophene)s (P3ATs), the electric modulus formalism of dielectric relaxation measurement together with the use of nonexponential decay function can be applied to describe the behavior of conductivity relaxation and carrier transport. The charge mobilities of neutral P3ATs calculated from conductivity relaxation with the use of the defect-diffusion model are in agreement with the data from field-effect transistor measurement. The temperature dependence of charge mobility exhibits a local maximum right after the end of glass transition region, which can be attributed to the transition of soft conformons in the disordered phase to localized conformons. The charge mobilities and activation energies of mobilities for P3ATs are dependent on conjugation length and volume fraction of conducting units. © 1994 John Wiley & Sons, Inc.