Response Of Bi-Level And Random Copolymer Brushes Based On Poly(N-Isopropylacrylamide) And Poly(Methacrylic Acid)

Because conformations and interactions are intimately linked, the rich phase behavior exhibited by multicomponent polymer-modified interfaces, and in particular multicomponent polymer brushes, offers new opportunities for manipulating interfacial properties. Despite the widespread use of a variety of grafting to and grafting from approaches for making polymer brushes, there are few reports of synthesis and responsive behavior of stratified block copolymer brushes. In this presentation we describe our efforts to create bi-level and random copolymer brushes consisting of poly(N-isopropylacrylamide) and poly(methacrylic acid) using surface initiated, photoiniferter-mediated photopolymerization. Pre-addition of a source of deactivating radicals combined with judicious choice of photopolymerization conditions enables the formation of bi-level brushes. In situ, multi-angle ellipsometry measurements show that the blocks of the bi-level brushes actuate independently to changes in pH and temperature, but respond in concert to changes in ionic strength. Efforts to examine the nanoscale structure of these systems as a function of pH and temperature using neutron reflectometry will also be highlighted.