Microstructural Observation and Property Characterization of Stimuli-Responsive Polymer Grafted onto Solid Surface Using AFM and QCM-D

Abstract

A review. It is well known that poly(N-isopropylacrylamide) (PNIPAM) exhibits thermally responsive properties in water. At a lower crit. soln. temp. (LCST) of around 32°C, PNIPAM chains show phase transition from coil to globule state. Therefore, solids on which the PNIPAM is grafted are expected to be applicable to a wide variety of industrial fields using expanding-shrinking property depending on temp. In this study, the structural changes of the PNIPAM chains grafted onto solid plates were investigated in aq. solns. with an at. force microscope (AFM) and a quartz crystal microbalance with dissipation (QCM-D). By AFM imaging, the transition of the grafted PNIPAM chains from brush to mushroom state was visualized. QCM-D signals showed significant change at around LCST, indicating that PNIPAM underwent a collapse by the dehydration of the chains. A complementary investigation indicated that a similar transition could be obsd. in solns. of high concn. electrolytes. It was also found that the grafting d. of the PNIPAM chains had a crit. role for the conformational behavior of the PNIPAM. [on SciFinder(R)]