Molecular Characteristics of Poly(<i>N</i>‐isopropylacrylamide) Separated from Nanocomposite Gels by Removal of Clay from the Polymer/Clay Network

<jats:title>Abstract</jats:title><jats:p>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(<jats:italic>N</jats:italic>‐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 <jats:styled-content>$\overline M _{\rm w}$<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/tex2gif-ueqn-1.gif" xlink:title="equation image"/></jats:styled-content> (=5.5 × 10<jats:sup>6</jats:sup> g · mol<jats:sup>−1</jats:sup>). Also, <jats:styled-content>$\overline M _{\rm w}$<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="graphic/tex2gif-ueqn-2.gif" xlink:title="equation image"/></jats:styled-content> was almost constant regardless of the clay concentration (<jats:italic>C</jats:italic><jats:sub>clay</jats:sub> = 1–25 × 10<jats:sup>−2</jats:sup> mol · l<jats:sup>−1</jats:sup>), even though the properties of the NC gel varied widely over this <jats:italic>C</jats:italic><jats:sub>clay</jats:sub> range. Comparisons of NC gels, PNIPA, and SiO<jats:sub>2</jats:sub>‐NC gels indicated that the clay platelets specifically play an important role in NC gels.</jats:p><jats:p><jats:boxed-text content-type="graphic" position="anchor"><jats:graphic xmlns:xlink="http://www.w3.org/1999/xlink" mimetype="image/jpeg" position="anchor" specific-use="enlarged-web-image" xlink:href="graphic/mgra001.jpg"><jats:alt-text>magnified image</jats:alt-text></jats:graphic></jats:boxed-text> </jats:p>