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      Polymer terminal group effects on properties of thermoresponsive polymeric micelles with controlled outer-shell chain lengths.

      1 ,
      Biomacromolecules
      American Chemical Society (ACS)

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          Abstract

          Well-defined amphiphilic diblock copolymers comprising thermoresponsive polymer segments of poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (PID) and hydrophobic polymer segments, poly(benzyl methacrylate) (PBzMA), were synthesized by controlled living radical polymerization. Terminal derivatization of PID segments to either hydroxyl or phenyl groups was achieved through reactions of coupling agents with thiol groups exposed by cleavage of terminal dithiobenzoate groups. Diblock copolymers formed core-shell type polymeric micelles with thermoresponsive outer shells. Hydrodynamic micellar diameters ranged from 12 to 31 nm, controlled by varying PID chain lengths. Differences in PID terminal groups did not affect the critical micelle concentration or micellar diameters. However, these groups demonstrated a significant influence on the micellar thermoresponses. Hydroxylated PID/PBzMA micelles exhibited a phase transition of approximately 40 degrees C, independent of PID molecular weights. Even though molecular weights and compositions of PID chains were equivalent except for terminal groups, micelles having the outermost surface phenyl groups exhibited drastically lower phase transition temperature shifts, especially for micelles with low molecular weight PID chains.

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          Author and article information

          Journal
          Biomacromolecules
          Biomacromolecules
          American Chemical Society (ACS)
          1525-7797
          1525-7797
          July 12 2005
          : 6
          : 4
          Affiliations
          [1 ] Institute of Advanced Biomedical Engineering and Science, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan.
          Article
          10.1021/bm050232w
          16004478
          56b41a0d-6790-4997-968f-aa1e6a8079b4

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