Molecular Characteristics of Poly(N-isopropylacrylamide) Separated from Nanocomposite Gels by Removal of Clay from the Polymer/Clay Network

The extraordinary mechanical and swelling/deswelling properties of nanocomposite (NC) gels are attributed to their unique organic (polymer)/inorganic (clay) network structure. In this study, poly(N-isopropylacrylamide) (PNIPA) was successfully separated from an NC gel network by decomposing the clay (hectorite) using hydrofluoric acid (HF). A very low HF concentration (0.2 wt.-%) was adequate for the decomposition of the clay without causing any damage to PNIPA. The separated PNIPA had a high (M) over bar (w) (=5.5 x 10(6) g . mol(-1)). Also, (M) over bar (w) was almost constant regardless of the clay concentration (C(clay) = 1-25 x 10(-2) mol . l(-1)), even though the properties of the NC gel varied widely over this C(clay) range. Comparisons of NC gels, PNIPA, and SiO(2)-NC gels indicated that the clay platelets specifically play an important role in NC gels.