Universality of Time-Temperature Scaling Observed by Neutron Spectroscopy on Bottlebrush Polymers

Nano Lett. 2021 May 26;21(10):4494-4499. doi: 10.1021/acs.nanolett.1c01379. Epub 2021 May 14.

Abstract

The understanding of materials requires access to the dynamics over many orders of magnitude in time; however, single analytical techniques are restricted in their respective time ranges. Assuming a functional relationship between time and temperature is one viable tool to overcome these limits. Despite its frequent usage, a breakdown of this assertion at the glass-transition temperature is common. Here, we take advantage of time- and length-scale information in neutron spectroscopy to show that the separation of different processes is the minimum requirement toward a more universal picture at, and even below, the glass transition for our systems. This is illustrated by constructing the full proton mean-square displacement for three bottlebrush polymers from femto- to nanoseconds, with simultaneous information on the partial contributions from segmental relaxation, methyl group rotation, and vibrations. The information can be used for a better analysis of results from numerous techniques and samples, improving the overall understanding of materials properties.

Keywords: Bottlebrush Polymer; Polydimethylsiloxane; Quasi-Elastic Neutron Scattering; Time−Temperature Superposition.