A New Associative Diblock Copolymer of Poly(ethylene glycol) and Dense 1,2,3-Triazole Blocks: Self-Association Behavior and Thermoresponsiveness in Water

In this work, new diblock copolymers of poly(ethylene glycol) (PEG) and dense 1,2,3-triazole blocks (EGm-b-APn and EGm-b-ABn, where m and n denote the degrees of polymerization), are synthesized by copper(I)-catalyzed azide-alkyne cycloaddition polymerization of 3-azido-1-propyne (AP) and 3-azido-1-butyne (AB), respectively, in the presence of PEG possessing a propargyl group. Their self-association behavior and thermoresponsive property in water are investigated. The characterization data indicate that EG45-b-AP6 and EG45-b-AP14 form dominantly spherical micelles, EG18-b-AP4 and EG18-b-AP10 form vesicles, and EG18-b-AB7 forms rodlike micelles. Aqueous solutions of EG18-b-AP10, EG45-b-AP14, and EG18-b-AB7 undergo lower critical solution temperature (LCST)-type phase separation. The thermoresponsive association behavior can be controlled by adjusting the ratio of block lengths and by attaching methyl substituents.