The influences of polyethylene glycol molecular weight on thermal stability, nonisothermal crystallization behavior, and morphology of poly(trimethylene terephthalate)/poly(ethylene oxide terephthalate) copolymers

A series of poly(trimethylene terephthalate)/poly(ethylene oxide terephthalate) copolymers with approximately 25 wt% PEG content were synthesized and investigated. The results showed that the thermal stability of copolymers increased with increasing Mn, PEG from 1000 to 4000 g/mol. However, the thermal stability of the copolymer with Mn, PEG = 300 g/mol was better than the copolymer with Mn, PEG = 600 g/mol. The nonisothermal crystallization kinetics of the copolymers was analyzed using Ozawa and Mo models, and only the Mo method was satisfactory in describing this system. Polarized optical microscopy revealed that all copolymers could form ring banded spherulites and the temperature window for their formation was basically identical for all copolymers. In addition, the spherulitic growth rate curves of copolymers exhibited a bell shape, and both the maximum growth rate and the crystallization temperature corresponding to the maximum growth rate increased with the increase in Mn, PEG.