Synthesis and Characterization of Biocompatible, Thermoresponsive ABC and ABA Triblock Copolymer Gelators
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- 作者：Chengming Li ; Niklaas J. Buurma ; Ihtshamul Haq ; Colin Turner ; Steven P. Armes ; Valeria Castelletto ; Ian W. Hamley ; and Andrew L. Lewis
- 刊名：Langmuir
- 出版年：2005
- 出版时间：November 22, 2005
- 年：2005
- 卷：21
- 期：24
- 页码：11026 - 11033
- 全文大小：255K
- 年卷期：v.21,no.24(November 22, 2005)
- ISSN：1520-5827
文摘
The synthesis of doubly thermoresponsive PPO-PMPC-PNIPAM triblock copolymer gelators by atomtransfer radical polymerization using a PPO-based macroinitiator is described. Provided that the PPOblock is sufficiently long, dynamic light scattering and differential scanning calorimetry studies confirmthe presence of two separate thermal transitions corresponding to micellization and gelation, as expected.However, these ABC-type triblock copolymers proved to be rather inefficient gelators: free-standing gelsat 37 
C required a triblock copolymer concentration of around 20 wt%. This gelator performance shouldbe compared with copolymer concentrations of 6-7 wt% required for the PNIPAM-PMPC-PNIPAMtriblock copolymers reported previously. Clearly, the separation of micellar self-assembly from gel networkformation does not lead to enhanced gelator efficiencies, at least for this particular system. Nevertheless,there are some features of interest in the present study. In particular, close inspection of the viscosity vstemperature plot obtained for a PPO43-PMPC160-PNIPAM81 triblock copolymer revealed a local minimumin viscosity. This is consistent with intramicelle collapse of the outer PNIPAM blocks prior to the developmentof the intermicelle hydrophobic interactions that are a prerequisite for macroscopic gelation.
C required a triblock copolymer concentration of around 20 wt%. This gelator performance shouldbe compared with copolymer concentrations of 6-7 wt% required for the PNIPAM-PMPC-PNIPAMtriblock copolymers reported previously. Clearly, the separation of micellar self-assembly from gel networkformation does not lead to enhanced gelator efficiencies, at least for this particular system. Nevertheless,there are some features of interest in the present study. In particular, close inspection of the viscosity vstemperature plot obtained for a PPO43-PMPC160-PNIPAM81 triblock copolymer revealed a local minimumin viscosity. This is consistent with intramicelle collapse of the outer PNIPAM blocks prior to the developmentof the intermicelle hydrophobic interactions that are a prerequisite for macroscopic gelation.