Thermodynamic and ordering kinetics in asymmetric PS-b-PMMA block copolymer thin films

TL;DR

This study investigates the ordering kinetics of asymmetric PS-b-PMMA block copolymer thin films near the order-disorder transition, revealing a curvature-driven grain coarsening process and thermodynamic influences on kinetics.

Contribution

It provides new experimental insights into the thermally activated ordering kinetics and the interplay between thermodynamics and kinetics in asymmetric PS-b-PMMA thin films.

Findings

Grain coarsening follows a 1/2 growth exponent, indicating curvature-driven ordering.

Activation enthalpy and Meyer-Neldel temperature are characterized for the copolymer.

Multiple phenomena occur during thermally activated ordering at different molecular levels.

Abstract

The ordering kinetics of standing cylinder-forming polystyrene-block-poly (methyl methacrylate) block copolymers (molecular weight: 39 kg/mol) close to the order-disorder transition is experimentally investigated following the temporal evolution of the correlation length at different annealing temperatures. The grow exponent of the grain coarsening process is determined to be 1/2, signature of a curvature driven ordering mechanism. The measured activation enthalpy and the resulting Meyer-Neldel temperature for this specific copolymer along with the data already known for PS-b-PMMA block copolymers in strong segregation limit, allows investigating the interplay between the ordering kinetics and the thermodynamic driving force during the grain coarsening. These findings unveil various phenomena concomitantly occurring during the thermally activated ordering kinetics at segmental, single chain, and collective level.