Glass transition of oligostyrene with different end groups

Abstract

Oligostyrenes having butyl groups at both ends, a butyl group at one and a proton at the other, and protons at both ends were prepared. The oligomers obtained were separated into fractions from monomer to octamer by the combined use of vacuum distillation and gel permeation chromatography (GPC). The purity of each fraction was characterized by GPC. The monomer and dimer having butyl groups at both ends were found to crystallize; melting and premelt crystallization were detected by differential scanning calorimeter (DSC). All the oligomer fractions and the monomer became glassy when quenched from the molten state. The glass transition temperatures (Tg’;s) of the oligomers having the same number of main chain segments were similar in spite of the difference in molecular weight (Mn). Thus, the values of the constants in the equation of Tg - A-B/Mn (where A and B are constants) varied depending on the type of sample in the range of molecular weight up to 600. This fact indicates that the molecular motion of the end groups cancels out the effect of increasing molecular weight. © 1982 The Society of Polymer Science, Japan. All rights rerserved.