Structural optimization of highly branched thermally responsive polymers as a means of controlling transition temperature

Abstract

Highly branched “smart” polymers have emerged as a unique class of polymers with wide-ranging applications. Poly(N-isopropylacrylamide) (pNIPAAm) is at the forefront of stimuli-responsive polymers; however, few transition temperature-modification methods of linear pNIPAAm have been explored in highly branched systems. In this study, the three primary techniques of transition temperature modification of linear pNIPAAm are investigated for their efficacy on highly branched polymers. Of these techniques, cosolvent-mediated tacticity control demonstrates an effect opposite of that which is expected. Temperature transition control via end-group modification shows a marked decrease in efficacy in highly branched systems, despite highly branched systems having more end groups per polymer. Copolymerization with hydrophilic comonomers exhibits varying changes in efficacy compared to linear analogs, lending insights into the specific effects on the structured water surrounding the copolymer. While copolymerization proved to be most versatile in changing the transition temperature, all of the techniques showed interesting secondary effects. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013