On the other hand, if R1, R2, R3, R4, R5 and R6 all are a phenoxy group or the hydrogen atoms on the benzene ring are partly or wholly displaced, the each group hardly undertakes ester exchange with trimethylene glycol and scarcely causes dispersion in the molecular order or because of its sublimability, the group is liable to dissipate out of the system during the polymerization to decrease the e