Thermally Induced Polymeric Assemblies from the PAAc-Based Copolymer Containing Both PNIPAAm and mPEG Grafts in Water

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• 作者：Wen-Hsuan Chiang^† ; ; Yuan-Hung Hsu^† ; ; Chorng-Shyan Chern^‡ ; ; Hsin-Cheng Chiu*^† ;
• 刊名：Journal of Physical Chemistry B
• 出版年：2009
• 出版时间：April 2, 2009
• 年：2009
• 卷：113
• 期：13
• 页码：4187-4196
• 全文大小：254K
• 年卷期：v.113,no.13(April 2, 2009)
• ISSN：1520-5207

文摘

Graft copolymer comprising acrylic acid (AAc) units as the backbone and poly(N-isopropylacrylamide) (PNIPAAm) and monomethoxy poly(ethylene glycol) (mPEG) as the grafts undergoes phase transition and supramolecular assembly into colloidal particles in water upon the thermally induced hydrophobic association. The structural characteristics of the polymeric assemblies made from the graft copolymer in water are strongly dependent on the copolymer concentration and the way that the copolymer solution is subjected to heating from 25 °C to the phase transition region (occurring in the range 3035 °C). The resultant assemblies are characterized by forming hydrophobic PNIPAAm regions with the multicore architecture and intercore connections. Interesting enough, these colloidal systems obtained from the copolymer solutions at different concentrations (10.0 and 1.0 mg/mL) and heating methods (fast and slow heating) exhibit very different structural responses when subjected to further temperature increase (from 3035 to 60 °C). The mutual interactions among the components (PAAc backbone and PNIPAAm and mPEG grafts) of the copolymer were shown to play a crucial role in the evolution of the ultimate assembly structure. A molecular packing model was proposed to illustrate the mechanisms of the thermally induced structural transformation processes for the amphiphilic graft copolymer in water.