Tuning Transition Properties of Stimuli-Responsive Brushes by Polydispersity

Abstract

A new design for sensors and switches based on polymer brushes including a small fraction of end-grafted adsorption-active minority chains has been proposed recently. The switching transition is controlled by temperature or solvent composition changes and is linked to a sharp change from a flattened adsorbed conformation to a stretched conformation. Two characteristics are most important for the switch performance: the sharpness of the transition affecting the switch sensitivity, and the response time. Herein, Monte Carlo simulations are used to study the effects of brush polydispersity on the main properties of the switching transition. The chain length distribution is taken to be of Schulz–Zimm type, and different values of the polydispersity index are considered. Contrary to intuitive expectations, polydispersity enhances the performance of the switch, in particular by reducing the activation barrier controlling the response time. Polydispersity also dramatically increases the robustness of the switch with respect to modifications of the adsorption-active switch chains. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim