Twist glass transition in regioregulated poly(3-alkylthiophenes)s

TL;DR

This study investigates the twist-glass transition in regioregulated poly(3-alkylthiophenes), revealing a glass transition related to thiophene ring twisting in crystalline phases through various spectroscopic and calorimetric methods.

Contribution

It introduces the concept of a twist-glass transition in poly(3-alkylthiophenes), linking molecular dynamics to a glass transition analogous to plastic crystal behavior.

Findings

Identified a twist-glass transition around 340 K in P3BT.

Linked the transition to enthalpy relaxation and molecular twisting.

Used FTIR, NMR, and DSC to characterize the transition.

Abstract

The molecular structure and dynamics of regioregulated poly(3-butylthiophene) (P3BT), poly(3-hexylthiophene)(P3HT), and poly(3-dodecylthiophene) (P3DDT) were investigated using Fourier transform infrared absorption (FTIR), solid state $^{13}$C nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC) measurements. In the DSC measurements, the endothermic peak was obtained around 340 K in P3BT, and assigned to enthalpy relaxation that originated from the glass transition of the thiophene ring twist in crystalline phase from results of FTIR, $^{13}$C cross-polarization and magic-angle spinning (CPMAS) NMR, $^{13}$C spin-lattice relaxation time measurements, and centerband-only detection of exchange (CODEX) measurements. We defined this transition as {\it twist-glass transition}, which is analogous to the plastic crystal - glassy crystal transition.