Synthesis of degradable molecular brushes via a combination of ring‐opening polymerization and click chemistry

Abstract

ABSTRACTAcid‐degradable molecular brushes with polycarbonate backbone and densely grafted side chains (∼1.9 SCs per backbone repeating unit) were synthesized for the first time using the grafting‐onto method. Extremely efficient copper‐catalyzed azide‐alkyne cycloaddition click reactions between the polycarbonate backbone containing two pendant azido groups per backbone unit and alkynyl‐terminated poly (methyl acrylate) (ay‐PMA72, average degree of polymerization DP = 72) SCs were demonstrated to finish in 10 min with a quantitative conversion of the azido groups. Similar grafting efficiencies were also achieved when using alkynyl‐terminated polystyrene (ay‐PS), poly(ethylene oxide) (ay‐PEO), and poly (t‐butyl acrylate)‐b‐polystyrene (ay‐PtBA‐b‐PS) to successfully prepare molecular brushes with high grafting density (>1.8 SCs per backbone repeating unit). Under acidic condition, the polycarbonate backbones were completely degradable and the final degraded product of the molecular brushes was a linear polymer chain with molecular weight two times of the SCs. When a mixture of hydrophobic ay‐PS and hydrophilic ay‐PEO chains was used, amphiphilic heterobrushes PC‐g‐(PS‐co‐PEO) were synthesized, which could self‐assemble into micelles or vesicles in selective solvents, depending on the ratio of the two SCs in the brush. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 239–248