Acta Chimica Sinica ›› 2012, Vol. 70 ›› Issue (16): 1690-1696.DOI: 10.6023/A12040167 Previous Articles     Next Articles

Full Papers


张文建, 范溦, 李敏, 洪春雁, 潘才元   

  1. 中国科学院软物质化学重点实验室 中国科学技术大学 高分子科学与工程系 合肥 230026
  • 投稿日期:2012-05-05 发布日期:2012-06-19
  • 通讯作者: 洪春雁
  • 基金资助:
    项目受国家自然科学基金(Nos. 20974103, 21074121, 21090354)资助.

Multi-responsive Hyperbranched Star Copolymer: Synthesis, Self-assembly and Controlled Release

Zhang Wenjian, Fan Wei, Li Min, Hong Chunyan, Pan Caiyuan   

  1. CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026
  • Received:2012-05-05 Published:2012-06-19
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Nos. 20974103, 21074121 and 21090354).

Multi-responsive (temperature, pH and redox) hyperbranched star polymers, poly(2-(2-methoxyethoxy)ethyl methacrylate)-star-poly(dimethylaminoethyl methacrylate) (H-PMEO2MA-star-PDMAEMA) have been successfully synthesized by self-condensing vinyl polymerization of disulfide-based inimer and MEO2MA first, and subsequently atom transfer radical polymerization of DMAEMA with H-PMEO2MA as macroinitiator. The Mn and Mw/Mn of the H-PMEO2MA were 8300 g/mol and 2.61, respectively. H-PMEO2MA-star-PDMAEMAs with different molecular weights were obtained by adjusting the polymerization time. The molecular weight of the hyperbranched star copolymer increased but the polydispersity index (PDI) decreased with increasing polymerization time. Since the PDI of the PDMAEMA formed by ATRP is low, with the molecular weight increase of the PDMAEMA, the relative amount of H-PMEO2MA in the hyperbranched star copolymers becomes less; as a result, the influence of the core H-PMEO2MA’s PDI on the hyperbranched star copolymers decreases. UV/Vis TU-1901 spectrophotometer was used to investigate the lower critical solution temperature (LCST) of the resultant polymer. The LCST of H-PMEO2MA is relatively low (2—10 ℃). The effects of the compositions and pH of the solution on LCST of the hyperbranched star copolymers were studied. The LCST increased with the chain length increase of PDMAEMA. The pH of the solution has a significant impact on the LCST of the hyperbranched star copolymers. With decrease of the pH value, the protonation degree of PDMAEMA increased, the repulsion between the chain segments enhanced, making the aggregation of the H-PMEO2MA-star-PDMAEMA molecules become difficult, and as a result, the water-solubility of the hyperbranched star copolymers enhanced. In addition, when temperature of the aqueous solution raised from 2 ℃ to room temperature, the spherical micelles with H-PMEO2MA as core and PDMAEMA as shell were formed. During the formation of spherical micelles in the aqueous solution of H-PMEO2MA-star-PDMAEMA and Nile Red, the Nile Red was successfully encapsulated in the micelles. The controlled release of this system, in which Nile Red was used as model drug, was investigated, the results showed that this system is pH and redox-responsive, and may have potential application in drug delivery.

Key words: self-condensing vinyl polymerization (SCVP), atom transfer radical polymerization (ATRP), hyperbranched star copolymer, multi-responsive, controlled release