(748e) Sharp Lower Critical Solution Temperature Transition for Novel N-Isopropylacrylamide Based Polymers

Authors: 
Alf, M. E., Massachusetts Institute of Technology
Hatton, T. A., Massachusetts Institute of Technology
Gleason, K. K., Massachusetts Institute of Technology


A novel, thermally responsive N-isopropylacrylamide (NIPAAm) based polymer with a sharp lower critical solution temperature (LCST) for conformal and substrate independent surface modification is presented. Initiated chemical vapor depositon (iCVD) is a solventless, gentle, one-step process used here to deposit thin films of the lightly cross-linked polymer, poly(N-isopropylacrylamide-co-di(ethylene glycol) divinyl ether) (p(NIPAAm-co-DEGDVE)). The polymer's bulk responsive characteristics are investigated using quartz crystal microbalance with dissipation monitoring (QCM-D), showing a sharp LCST transition curve with inflection point at 28.5 ± 0.3 °C. Static contact angle measurements explore the surface responsive properties on both flat and nanostructured surfaces. The change in contact angle around the LCST increases from 30° on a flat surface to 85° on a conformally coated forest of multi-walled carbon nanotubes (MWCNTs). A range of cross-linker densities is explored as well to understand how the volumetric and surface responsive characteristics can be controlled. The protein adsorption characteristics of materials coated with this novel polymer are investigated via fluorescence imaging and QCM-D studies to understand its relevance for separation applications.