Abstract
This paper describes the reversible phase transition behavior of a thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) shell at the surface of a hydrophilic core. Reversible addition-fragmentation transfer (RAFT) polymerization of N-isopropylacrylamide was conducted using a hydrophilic hyperbranched poly(glycidol) (HPG)-based macroRAFT agent. At lower temperatures (<30 °C), the resultant multiarm star block copolymer (HPG–PNIPAM) exists as unimolecular micelles, with hydrophilic HPG as the core and a densely grafted PNIPAM brush as the shell. In laser light scattering (LLS) studies, the concentration used for HPG–PNIPAM is 5 × 10−6 g ml−1, to avoid any possible aggregation between dendritic unimolecular micelles above the lower critical solution temperature (∼32 °C) of PNIPAM. What we observe for the phase transition of HPG–PNIPAM involves only unimolecular process. A combination of dynamic and static LLS studies of HPG–PNIPAM in aqueous solution reveals a reversible phase transition on heating and cooling.
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The financial support of the National Natural Scientific Foundation of China (20704001), the Anhui Provincial Natural Science Foundation (070414191) and the Project of Scientific Research for Young University Teachers of Anhui Province (2007jq1059) is gratefully acknowledged.
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Luo, S., Hu, X., Zhang, Y. et al. Synthesis of thermoresponsive unimolecular polymeric micelles with a hydrophilic hyperbranched poly(glycidol) core. Polym J 43, 41–50 (2011). https://doi.org/10.1038/pj.2010.93
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DOI: https://doi.org/10.1038/pj.2010.93
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