Gel Formation and Molecular Characteristics of Poly(<i>N</i>‐isopropylacrylamide) Prepared by Free‐Radical Redox Polymerization in Aqueous Solution

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Published
2010-04-23
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  • http://onlinelibrary.wiley.com/termsAndConditions#vor
DOI
  • 10.1002/macp.200900565
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Wiley

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<jats:title>Abstract</jats:title><jats:p>The molecular characteristics of poly(<jats:italic>N</jats:italic>‐isopropylacrylamide) (PNIPA), prepared by free‐radical polymerization using an aqueous redox initiator and reaction conditions comparable to those used in the synthesis of nanocomposite gels, were investigated by altering the monomer concentration ([NIPA]) and the polymerization temperature (<jats:italic>T</jats:italic><jats:sub>p</jats:sub>) across the transition temperature (LCST). When <jats:italic>T</jats:italic><jats:sub>p</jats:sub><LCST, there is a critical [NIPA] (=<jats:italic>n</jats:italic>*) above which PNIPA partially forms gels in the absence of a chemical crosslinker, and the gel fraction increases with increasing [NIPA] and decreasing <jats:italic>T</jats:italic><jats:sub>p</jats:sub>. In the range of <jats:italic>n</jats:italic><<jats:italic>n</jats:italic>*, the molecular weight of soluble PNIPA correlated well with [NIPA]. When <jats:italic>T</jats:italic><jats:sub>p</jats:sub>>LCST, gels were not formed regardless of [NIPA]. The structure and mechanism of formation of self‐crosslinked PNIPA gels are discussed.</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>

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