Melting and transition of isotactic polybutene-1 precipitated from solutions

Abstract

The equilibrium concept of conformation is the most important to understand chemical physics, and the non-equilibrium based conformation is the molecular basis underlying essentially all the physical properties of polymers. As a polymer chain with long relaxation time, the conformational memory of isotropic polybutene-1 (iPB-1) could not be completely erased even after it has gone into solution or melt. It is considered that the polymer chains are diluted and the interactions between the chains are reduced in solutions. In this work, the iPB-1 samples with different molecular weight were prepared from solutions by adding various volumes of precipitant or from solutions of various concentrations by adding the same volume of precipitant. The structure, melting and transition of the obtained iPB-1 samples were characterized by DSC, FTIR, WAXS, and SAXS techniques. It was found that the form III increases with the volume of precipitant or solution concentration, and the form III formed from the solution without stirring is more than that formed from the stirred solution. The melting temperature of form III is lower than that of form I′ in the same sample and the transition of solution crystallized iPB-1 is related to the melting of the prepared iPB-1 samples. The temperature for form II formation if iPB-1 prepared from the solutions dominates the form II-form I transition. The crystallization, melting and transition of the iPB-1 prepared from solutions were discussed based on the non-equilibrium chain dynamics and conformation adjustment of polymer chains and clusters, which would be helpful to understand the dynamics and transition of iPB-1.