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

We demonstrate 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, where A is a weak polyelectrolyte block, and B is a temperature-responsive block. Multilayers of a micelle-forming A-B-A triblock copolymer were constructed using LbL deposition with a polyanion. The polyanion type and self-assembly pH were critical parameters for constructing functional films of block copolymer micelles (BCMs). When a polycarboxylic acid was used in self-assembly, films assembled at pH $\ge $ 6 showed fully reversible, 3 to 5-fold changes in film thickness in response to temperature cycling between 6 and 20 $^{\circ}$C, enabled by swelling/collapse of the BCM central block.