Synthesis and characterization of dual-stimuli-responsive micelles based on poly(N-isopropylacrylamide) and polycarbonate with photocleavable moieties

Dual-sensitive block copolymers, PNiPAAm-b-PNBTMC, were synthesized via the ring-opening polymerization of 3-methyl-3-nitrobenzyl-trimethylene carbonate (NBTMC) bearing numerous 2-nitro-benzoxycarbonyl photolabile groups with a PNiPAAm macroinitiator in the presence of an organocatalyst, 1,5,7-triazobicyclo-[4.4.0]dec-5-ene (TBD). When the polymer solutions were exposed to ultraviolet (UV) irradiation, we observed significant changes in the structure and morphology of the particles. Fluorescence spectroscopy studies revealed that the copolymers underwent micellization or dissociation transitions in water in response to temperature changes and UV irradiation. No significant toxicity of these nanoparticles was found at concentrations up to 300 μg mL− 1.