Poly(ethylene terephathalate)/1,2-propanediolisobutyl polyhedral oligomeric silsesquioxane (POSS) composites were prepared by in situ polymerization with 1.5-5.0 wt% loading of POSS. The dispersion of POSS in PET matrix was investigated by scanning electron microscope(SEM) the interaction between POSS and PET chains was studied by nuclear magnetic resonance(NMR) andX-ray photoelectron spectroscopy(XPS), and the thermal behavior of PET/POSS composites was investigated by DSC and TG as well as the melt rheological testing of PET/POSS. SEM observation suggests that POSS particles disperse evenly innanosize(80-100nm)in PET matrix, and this fine dispersion of POSS was further supported by XPS analysis, there is a covalent linkage presenting between POSS and PET chains. The crystallization temperature of the composites moved to high temperature as the POSS particles behave as the nucleating agent. The shear modulus(G’) increased apparently with the addition of POSS.

Poly(ethylene terephthalate-co-4,4’-bibenzoate)s (PETBBs) with 0-25mol% bibenzoate unit were prepared from terephthalic acid (PTA), 4,4'- bibenzoic acid (BBA) and ethylene glycol (EG). The chemical composition and number-average sequence length of the resultant PETBBs were investigated by 13C-NMR. It was improved that the chemical composition of PETBBs is identical with the feed ratio, and the number-average sequence length of PET segment (LPET) becomes reduced with increasing BBA unit. The molecular weights of PETBBs reaches the high level for practical use. DSC analysis explains that the glass transition temperature (Tg) increases almost linearly and the crystallization becomes difficulty with increasing content of BBA unit. X-ray diffraction also illustrates that both crystallinity and crystal size reduced as more BBA unit is incorporated. Moreover, the relationship between the number-average sequence length and the melting temperature was investigated. The linear correlation between the number-average sequence length (LPET) and the melting temperature was observed.