Acta Chimica Sinica ›› 2013, Vol. 71 ›› Issue (01): 114-120.DOI: 10.6023/A12100805 Previous Articles     Next Articles



康宏亮a, 刘瑞刚a, 黄勇a,b   

  1. a 中国科学院化学研究所 高分子物理与化学国家重点实验室 北京分子科学中心 北京 100190;
    b 中国科学院理化技术研究所 工程塑料国家工程研究中心 北京 100190
  • 投稿日期:2012-10-22 发布日期:2012-12-18
  • 通讯作者: 刘瑞刚, 黄勇;
  • 基金资助:
    项目受国家自然科学基金(Nos. 20974114, 21174156)和中国科学院知识创新工程(No. KJCX2-YW-H19)资助.

Synthesis of Ethyl Cellulose Grafted Poly(N-isopropylacrylamide) Copolymer and Its Micellization

Kang Honglianga, Liu Ruiganga, Huang Yonga,b   

  1. a State Key Laboratory of Polymer Physics and Chemistry, Beijing National Laboratory of Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190;
    b National Engineering Research Center of Engineering Plastics, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190
  • Received:2012-10-22 Published:2012-12-18
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Nos. 20974114, 21174156) and the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KJCX2-YW-H19).

Thermo-responsive graft copolymers, ethyl cellulose grafting poly(N-isopropylacrylamide) (EC-g-PNIPAm), were synthesized by single-electron transfer living radical polymerization (SET-LRP) in THF/methanol mixed solvent. Ethyl cellulose macro-initiators (EC-Br) for SET-LRP were synthesized by the esterification between the hydroxyl groups on EC backbones and 2-bromoisobutyryl bromides. The degree of substitution of the EC-Br macro-initiator was tailored by varying the feeding mole ratio of 2-bromoisobutyryl bromide to the hydroxyl group on ethyl cellulose. Three EC-Br macro-initiators with different Br substitutions were used as the macro-initiators and it was found that the converting degree of the initiator sites was efficient and the graft density of graft copolymer was controllable. The SET-LRP of NIPAm was efficient that the monomer conversion was above 60% within 25 h. The linear plot of ln([M]0/[M]t) versus the conversion indicated that the reaction was living and controllable. The graft copolymers were characterized by means of gel permeation chromatography (GPC), 1H NMR and FTIR spectroscopy. GPC peak of the graft copolymer became narrower and shifted to the low elution time with the increase of reactive time. The molecular weight of the side-chain linearly increased with the reaction time. EC-g-PNIPAm copolymers were typical amphiphilic graft copolymers, having the hydrophobic EC backbone and the hydrophilic PNIPAm side chains. They could be self-assembled and form stable micelles in a selective solvent, water. The micelles were in spherical shape with typical diameter around 100 nm. Rod-like and flower shaped particles were also observed, which was probably due to the fusion of the spherical shaped micelles. The structure of the spherical shaped micelles was that the EC backbone collapsed to form the core of the micelles and the hydrophilic PNIPAm chains stayed in the outside of the micelles to stabilize the micelles. Due to the thermoresponsive branch chains of PNIPAm, the micelles could shrink with rising temperature due to the collapses of the PNIPAm side chains.

Key words: ethyl cellulose, poly(N-isopropylacrylamide), single-electron transfer living radical polymerization (SET-LRP), graft polymerization, thermoresponsive