Polymer microstructure directs the solvent-selective swelling response of polymer brushes

We compared the solvent-responsivity of block and statistical copolymer brushes of varied solvophobic-to-solvophilic ratios by measuring brush swelling in two sol- vents of varying polarity. We first copolymerized 2-(dimethylamino)ethyl methacrylate (DMA) and 2-(diisopropylamino)ethyl methacrylate (DiPA) and tuned DMA:DiPA ratios in block and statistical copolymer brushes. Then, we selectively quaternized DMA to enlarge solvophilicity differences between DMA and DiPA; water but not isopropanol is a good solvent for qDMA whereas DiPA exhibits the opposite solvation preference. In water, increasing DiPA incorporation depressed brush swelling for both block and 1 statistical copolymer brushes. However, in isopropanol, swelling responses diverged; block copolymer brushes swelled between 9 and 37% less than compositionally equiv- alent statistical copolymer brushes. Additionally, we investigated the feasibility of de- ploying our polymer brushes in cell-interfacing applications by evaluating cytocom- patibility. We established that the spatial distribution—and not just the relative abundance of solvophobic and solvophilic repeat units—governs polymer brushes’ solvent responsivity.