Impact of Local Stiffness on Entropy Driven Microscopic Dynamics of Polythiophene

TL;DR

This study uses neutron spin echo spectroscopy to explore how local stiffness influences the microscopic dynamics of polythiophene, revealing a universal behavior of chain stiffness and a single chain glassy state.

Contribution

It demonstrates the first experimental observation of a single chain glassy state in polythiophene and extends the Zimm model to describe semiflexible polymer dynamics.

Findings

Confirmed the existence of beads with finite length in semiflexible chains.

Found universal behavior of local chain stiffness across conditions.

Indicated chain dynamics play a major role in thermochromic behavior.

Abstract

We exploited the high temporal and spatial resolution of neutron spin echo spectroscopy to investigate the large-scale dynamics of semiflexible conjugated polymer chains in solutions. We obtained the first experimental demonstration of earlier predicted single chain glassy state. We used a generalized approach of the well-established Zimm model of flexible polymers to describe the relaxation mode spectra of locally stiff polythiophene chains. The Zimm mode analysis confirms the existence of beads with a finite length that corresponds to a reduced number of segmental modes in semiflexible chains. Irrespective of the temperature and the molecular weight of the conjugated polymer, we witness a universal behavior of the local chain stiffness and invariability of the beads length. Our experimental findings indicate possibly minor role of the change in {\pi}-electron conjugation length (and therefore conjugated backbone planar to non-planar conformational transition) in the observed thermochromic behavior of polythiophene but instead point on the major role of chain dynamics in this phenomenon.