Polysulfone-graft-poly(tert-butyl acrylate): Synthesis, Nanophase Separation, Poly(tert-butyl acrylate) Hydrolysis, and pH-Dependent Iridescence

Polysulfone- graft -poly( tert -butyl acrylate) or PSf- g -P t BA samples were prepared by reacting lithiated Udel polysulfone (PSf) in THF at −78 °C with bromine-end-functionalized poly( tert -butyl acrylate) or P t BA-Br. In bulk, the P t BA branches segregated from the PSf backbone to form nanometer-sized domains. The P t BA domain shape changed from wormlike to cylindrical and to lamellar as its volume fraction increased from 19.2% to 44%. While the wormlike and cylindrical morphologies lacked long-range order, the alternating P t BA and PSf lamellae were packed regularly. The P t BA domains in such graft copolymer films could be hydrolyzed to yield poly(acrylic acid) or PAA chains without affecting film integrity. After P t BA hydrolysis, a sample with a P t BA volume fraction of 38% showed iridescence or a 1-D photonic stop band at ∼450 nm in basic water. The iridescence could be turned off and on by cycling pH between 2 and 10, for example.