Synthesis and characterization of T_g for pyrene end-labelled polystyrene having no ester linkages

A series of pyrene end-labelled polystyrene (PS) samples having molecular weights ranging from 2000 to 40 000 have been synthesized anionically. Complete characterization data are provided. The end-labelling reaction is performed by coupling the living polystyryl anion with 1-bromobutylpyrene, with coupling efficiencies ranging from 72 to 90%. The resulting pyrene end-labelled PS has no ester linkage in the backbone, a common structure resulting from alternative end-labelling reactions proceeding via terminal hydroxyl units. This leads to a potential enhancement in thermal and hydrolytic stability; in fact, the samples have the same thermal stability as unlabelled PS. The glass transition temperatures (Tg) of our samples vary linearly with M ̄-1n, consistent with the Fox-Flory equation. However, the Tg values of the labelled PS samples are higher than the unlabelled ones with the difference widening as M ̄n decreases. This difference is explained by a decrease of chain end mobility and hence of free volume caused by bulky end groups. © 1988.