SYNTHESIS AND AGGREGATION BEHAVIOR OF AN AMPHIPHILIC BLOCK COPOLYMER WITH STRONG PUSH-PULL AZO CHROMOPHORES ON SIDE CHAINS

An amphiphilic block copolymer functionalized with strong push-pull azobenzene moieties, PEG-b-P6CNAzo, was synthesized through a scheme that combined ATRP and post-polymerization azo-coupling reaction. First, the precursor diblock copolymer, PEG-b-P6MA containing aniline groups was prepared by a PEGBr initiated ATRP of monomer 6-(N-methylanilino) hexyl methacrylate. Then PEG-b-P6CNAzo was obtained through azo-coupling reaction between PEG-b-P6MA and diazonium salt of 4-aminobenzonitrile. The azo block copolymer was carefully characterized by GPC, H-1-NMR and UV-Vis. The polymerization degree of PEG-b-P6MA was 122-b-13, which was obtained through H-1-NMR analysis. Due to the high yield of azo-coupling reaction, the polymerization degree of PEG-b-MCNAzo was also 122-b-13, the same as PEG-b-P6MA. GPC results revealed that both PEG-b-P6MA and PEG-b-P6CNAzo had narrow molecular weight distributions. By adding water under a rate of 0.5 mL/h to its THF solution with the concentration of 0.2 g/L, PEG-b-P6CNAzo formed rod-like micelles with diameter of ca. 11 nm obtained by TEM observation.