The correlation of chemical structure, crystalline morphology, and space charge distribution under a dc electrical field was investigated with three kinds of poly(propylene) (PP) with a different chemical structure, that is, homogeneous PP and block copolymer and random copolymer of PP. The space charge distribution of the samples was prominently affected by their chemical sequence structure and crystalline microstructure. Among samples of different PPs, all isothermally crystallized at 140℃, the sample of random coPP represents the most well proportional space charge distribution and the smallest number of space charges. The effect of thermal history on the space charge distribution was also investigated by the samples of block coPP. The sample thermally treated at 50℃ clearly represents a better proportional distribution than that at higher temperature of 140 and 100℃. Subsequent experiments indicate that the better proportional distribution attributes to imperfect and fine sperulites with the fine distribution of the "amorphous" region. The imperfect and fine sperulites originate from the random incorporation of ethylene segments or units into PP chains or fromthe low annealing temperature, and play an important role in the formation of shallowtraps and transportation of space charges.

Anewmethod to synthesize polyimide (PI)/silica nanohybrids has been presented. It uses silicic acid oligomer as the silica precursor, which was obtained by extracting with tetrahydrofuran (THF) from PH-adjusted water glass. The films of PI/silica nanohybrids remained transparent even at high silica content due to the formation of nanometer-scaled SiO2 particles at the addition of γ-aminopropyltriethoxysilane (APTES). In comparison with pure PI, PI/silica hybrids showed improved thermal stability and mechanical properties, and lower linear coefficients of thermal expansion (CTEs). The glass transition temperatures of the hybrids were increased with increasing content of silica or APTES as a result of the increasing limitation to the movements of the PI backbone.

Nanocomposites from poly(methyl methacrylate) (PMMA), silica (SiO2) and zirconia (ZrO2) were prepared using a novel nonhydrolytic sol-gel process. Silicic acid and zirconium oxychloride (ZrOCl2 8H2O) were used as the precursors of SiO2 and ZrO2, respectively. FT-IR and SEM results showed that nanometre-scaled SiO2/ZrO2 particles were uniformly distributed in and covalently bonded to the PMMA host matrix without macroscopic organiceinorganic phase separation, which was also confirmed by solvent extraction experiments. It was found that the transmittance of the nanocomposite films in the visible region remained above 95% even at 20wt% inorganic content and increased proportionally with decreasing inorganic content. The thermal stability and the thermal decomposition kinetics of the composites were studied. The results indicated that the activation energy (Ea) of the thermal decomposition of PMMA main chains in the composites was increased due to the addition of inorganic moieties. This kind of composite material may have the potential for applications in optical devices.