Development of structure and morphology during crystallization and solid state polymerization of polyester oligomers

Low molecular weight oligomers of poly- (ethylene terephthalate) (PET) and poly(ethylene naphthalate) (PEN) were synthesized and the crystallization behavior were examined. The crystallized oligomers underwent solid state polymerization (SSP) when subjected to temperatures close to melting temperature under nitrogen. The crystallites did not exhibit reorganization during SSP but the structure and morphology changed due to SSP. It was found that the catalyst used for the synthesis of the oligomers had an influence on both the crystallization and the SSP of the oligomer. Titanium isopropoxide (Ti(OiPr)4) reduces the crystallization rate of the oligomers but enhances the SSP rate, whereas, antimony trioxide (Sb2O3) increases the crystallization rate but reduces the SSP rate