Temperature-responsive self-assembly of charged and uncharged hydroxyethylcellulose-<Emphasis Type="Italic">graft</Emphasis>-poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) copolymer in aqueous solution |
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Authors: | Hang T T Phan Kaizheng Zhu Anna-Lena Kjøniksen Bo Nyström |
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Institution: | (1) Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo, Norway;(2) Department of Pharmaceutics, School of Pharmacy, University of Oslo, P.O. Box 1068, Blindern, N-0316 Oslo, Norway; |
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Abstract: | Temperature-induced interchain association and contraction of species in aqueous solutions of charged (MHEC(−)-g-PNIPAAM) and uncharged (MHEC-g-PNIPAAM) modified hydroxyethylcellulose-graft-poly(N-isopropylacrylamide) copolymer have been studied with the aid of turbidimetry and dynamic light scattering (DLS). It was
shown that by attaching PNIPAAM chains to the backbone of a hydrophilic cellulose derivative, a strongly temperature-responsive
copolymer could be prepared. The results show an intriguing interplay between interchain association and contraction of the
multichain species. The transition zone for compression is narrow, and the compaction effect is promoted by a low polymer
concentration and charges on the polymer moieties. The findings from DLS revealed two populations of species, namely molecularly
dispersed molecules or small clusters and interchain complexes, which exhibit temperature-induced collapse. The magnitude
of the cluster contraction can be modulated by changing the polymer concentration and charge density of the copolymer. |
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