Temperature-Induced, Reversible Swelling Transitions in Multilayers of a Cationic Triblock Copolymer and a Polyacid

Abstract

In this article, we seek to enable large-scale, fully reversible, thermally induced volumetric changes in layer-by-layer (LbL) electrostatically self-assembled thin films through the incorporation of A-B-A triblock copolymers. Poly(N,N-dimethylaminoethyl methacrylate)-b-poly(propylene oxide)-b-poly(N,N-dimethylaminoethyl methacrylate) (abbreviated “PD-PPO-PD”) was used as a dual pH and temperature-responsive component in the electrostatic self-assembly of multilayer thin films. In solutions of this triblock copolymer with poly(N,N-dimethylaminoethyl methacrylate) (PD) weak polyelectrolyte end blocks, the dehydration temperature of the central poly(propylene oxide) (PPO) block was strongly dependent on solution pH, as shown by microdifferential scanning calorimetry (micro-DSC) and dye solubilization techniques. Multilayer films were then assembled with poly(acrylic acid) (PAA) or poly(4-styrene sulfonate) (PSS) as anionic binding partners at various pH values, where the triblock copolymer was incorporated ...