Form II to form I transition in solution-crystallized isotactic polybutene-1

Abstract

Different polymer chains in a solution or melt have different conformations with corresponding entropy at each moment, which would be confined after crystallization. Equilibrium concept-based conformation or conformational entropy depends on chain dynamics, which is related to the effect of energy on conformational changes in polymer chains. Herein, an isotactic polybutene-1 (iPB-1) crystal was crystallized from solution by adding a precipitant at various temperatures. The solution-crystallized iPB-1 crystal was heated to 100 °C to obtain form II at different heat rates and the transition of form II was characterized. It was found that the form II to form I transition was not only related to the precipitation temperature but also to the heating rate of the solution-crystallized iPB-1. Thus, both precipitation temperature and heating rate determine the formation temperature of form II, i.e., form II that crystallized at lower temperature would transform faster. The results indicate that the conformation or conformational entropy of the amorphous region in iPB-1 is important to understand crystal transition.