CLICK CYCLIZATION OF LINEAR TRIBLOCK COPOLYMERS AT BLOCK JUNCTIONS UNDER HIGH CONCENTRATION DUE TO END-BLOCK SHIELDING  

作　　者：Jing Tao Bang-kun Jin Li-ying Li Chen He 何卫东 

机构地区：[1]CAS Key Laboratory of Soft Matter Chemistry,Department of Polymer Science and Engineering,University of Science and Technology of China

出　　处：《Chinese Journal of Polymer Science》2013年第7期959-959,960,965,共3页高分子科学（英文版）

基　　金：financially supported by the National Natural Scientific Foundation of China (Nos. 20934005 and 21274136)

摘　　要：Linear triblock copolymers of poly（N-isopropylacrylamide） （PNIPAM） and poly（ethylene glycol） （PEG） with two azide groups at both block junctions （PNIPAM-N3-PEG-N3-PNIPAM） are click reacted with dipropargyl oxalylate under high polymer concentration （250 g/L）. Benefiting from rapid feature of alkyne-azide click reaction and spatial shielding of PNIPAM end blocks, PEG center block of PNIPAM-N3-PEG-N3-PNIPAM remains separated although PNIPAM end blocks keep in contact under this high concentration. Therefore, PNIPAM-N3-PEG-N3-PNIPAM undergoes self-cyclization at block junctions to form tadpole-shaped architecture while N3-PEG-N3 without PNIPAM end blocks inter-connects linearly. The influence of block lengths of PEG and PNIPAM on the unusual cyclization under high polymer concentration is studied.Linear triblock copolymers of poly（N-isopropylacrylamide） （PNIPAM） and poly（ethylene glycol） （PEG） with two azide groups at both block junctions （PNIPAM-N3-PEG-N3-PNIPAM） are click reacted with dipropargyl oxalylate under high polymer concentration （250 g/L）. Benefiting from rapid feature of alkyne-azide click reaction and spatial shielding of PNIPAM end blocks, PEG center block of PNIPAM-N3-PEG-N3-PNIPAM remains separated although PNIPAM end blocks keep in contact under this high concentration. Therefore, PNIPAM-N3-PEG-N3-PNIPAM undergoes self-cyclization at block junctions to form tadpole-shaped architecture while N3-PEG-N3 without PNIPAM end blocks inter-connects linearly. The influence of block lengths of PEG and PNIPAM on the unusual cyclization under high polymer concentration is studied.

关 键 词：Self-cyclization Click chemistry Triblock copolymer High concentrated solution Spatial shielding. 

分 类 号：O631.3[理学—高分子化学]