Synthesis, micellization and gelation of temperature-responsive star-shaped block copolymers

Authors

  • Peng Zou,

    1. State Key Laboratory of Mould Technology, College of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, PR China
    Search for more papers by this author
    • Peng Zou and Lei Nie contributed to the work equally and should be regarded as co-first authors.
  • Lei Nie,

    1. State Key Laboratory of Mould Technology, College of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, PR China
    Search for more papers by this author
    • Peng Zou and Lei Nie contributed to the work equally and should be regarded as co-first authors.
  • Shuibin Feng,

    1. State Key Laboratory of Mould Technology, College of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, PR China
    Search for more papers by this author
  • Jinping Suo

    Corresponding author
    • State Key Laboratory of Mould Technology, College of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan, PR China
    Search for more papers by this author

Correspondence to: Jinping Suo, State Key Laboratory of Mould Technology, College of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074, PR China.

E-mail: jinpingsuo@mail.hust.edu.cn

Abstract

A series of amphiphilic temperature-responsive star-shaped poly(D,L-lactic-co-glycolic acid)-b-methoxy poly(ethylene glycol) (PLGA-mPEG) block copolymers with different arm numbers were synthesized via the arm-first method. Gel permeation chromatography data confirmed that star-shaped PLGA-mPEG copolymers had narrow polydispersity index, indicating the successful formation of star-shaped block copolymers. Indirectly, the 1H NMR spectra in two kinds of solvents and dye solubilization method had confirmed the formation of core-shell micelles. Further, core-shell micelles with sizes of about 30–50 nm were directly observed by transmission electron microscopy. Subsequently, the micellar sizes and distributions as a function of concentrations and temperature were measured. At various copolymer concentrations, individual micelles with size of 20–40 nm and grouped micelles with size of 600–700 nm were found. Micellar mechanism of star-shaped block copolymers in aqueous solution was simultaneously discussed. In addition, sol–gel transition of star-shaped block copolymers in water was also investigated via the inverting test method. The critical gel temperature (CGT) and critical gel concentration (CGC) values of two-arm, three-arm and four-arm copolymer solutions were markedly higher than ones of one-arm copolymer. Moreover, the same CGC values of copolymer solution with different molecular weight and the same arm composition were ~15 wt %, and CGT values increased from ~38 to ~47°C with increasing arm numbers. Finally, the temperature-dependent micellar packing gelation mechanism of star-shaped block copolymer was schematically illustrated. Copyright © 2013 John Wiley & Sons, Ltd.

Ancillary