Preparation of water-soluble hyperbranched polymers with tunable thermosensitivity using chain-growth CuAAC copolymerization

Abstract

Thermoresponsive hyperbranched polymers with a dangling oligo(ethylene oxide) (EO_x, x as the averaged number of EO units) chain on every monomer unit were constructed using the chain-growth copper-catalyzed azide–alkyne cycloaddition (CuAAC) copolymerization of two AB₂-F monomers with EO₃ and EO_7.5 as F groups. The one-pot polymerization produced hyperbranched polymers with a linearly increased molecular weight versus conversion and narrow molecular weight distribution (M_w/M_n ∼ 1.1). The composition of hyperbranched copolymers was governed by the monomer feed ratio and directly determined the cloud temperature of the polymers in water. The cloud temperature could be further tuned via periphery modification of the hyperbranched polymers using alkynyl-terminated oligomeric EO₃ chains, in the range of 17 to 60 °C within our investigation.