Synthesis of Multiblock Copolymers by Coupling Reaction Based on Self-Assembly and Click Chemistry

Diends-azido-terminated and diends-alkynyl-terminated poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers (N-3-PEO-b-PPO-b-PEO-N-3 and HC equivalent to C-PEO-b-PPO-b-PEO-C equivalent to CH) were respectively prepared and used together as the precursors for multiblock copolymer synthesis through coupling reaction by combination of self-assembly and click chemistry. The self-assembly of equimolar resultant triblock copolymers in water, a selective solvent for PEO, results in a core-shell structure with the insoluble and collapsed PPO blocks as the core and the soluble and swollen PEO blocks as the shell. The self-assembly concentrates and exposes the azido and alkynyl end groups on the periphery. The multiple click coupling reactions between the self-assembled diends-functionalized triblock copolymers were performed, leading to the highly efficient formation of -(-PEO-b-PPO-b-PEO-)(n)- multiblock copolymer chains. In comparison, the click coupling reaction was also presented in N,N-dimethylformamide (DMF) solution without self-assembly. It was found that the efficiency of the coupling reaction was very low, and no long multiblock copolymer chains were produced.