Stereoregulation of thermoresponsive polymer brushes by surface-initiated living radical polymerization and the effect of tacticity on surface wettability

In this study, stereocontrolled poly(N-isopropylacrylamide) (PIPAAm) brushes were grafted from surfaces by atom transfer radical polymerization (ATRP) in the presence of a Lewis acid, and the effect of PIPAAm brush tacticity on the thermoresponsive wettabiliy was investigated. PIPAAm grafted by ATRP in the presence of Y(OTf)₃ showed high isotacticity, while the control brush polymerized in the absence of Y(OTf)₃ was clearly atactic. The isotacticity and molecular weight of PIPAAm brushes were controlled by polymerization conditions. The wettability of isotactic PIPAAm-grafted surfaces decreased slightly below 10°C, although the phase transition temperature of atactic surface was 30°C, and the bulk isotactic polymer was water-insoluble between 5 and 45°C.