Tunable Thermoresponsiveness of Copolymers with Various Amine Groups in the Side Chains

摘要

Thermoresponsive copolymers were successfully synthesized by a combination of atom transfer radical polymerization (ATRP) and Cu(I)-catalyzed 1,3-dipolar cycloaddition of azide and alkynes (click chemistry). ATRP was employed to synthesize poly(2-hydroxyethyl methacrylate) (PHEMA), followed by the introduction of alkyne groups using pentynoic acid, leading to HEMA-alkyne. Different ratios of both 2-azidoethylamine or 2-azido-N,N-diethylethylamine and 2-azido-N,N-dimemylethylamine were employed to introduce the amine groups to the HEMA-alkyne backbone via click chemistry. Molecular weight, molecular weight distribution, and click reaction efficiency were determined by gel permeation chromatography (GPC) and ~1H NMR spectroscopy. The average molecular weight (M?) of the resulting polymers ranged from 5.9 × 10~4 to 1.0 × 10~5 depending on the molecular architecture. The transmission spectra of the 0.5 wt% aqueous solutions regarding the resulting polymers at 650 nm were measured as a function of temperature. Results showed that the lower critical solution temperature (LCST) could be easily controlled by the different compositions of the amine groups.