Synthesis and characterization of nitrobenzyl carbonate (NBC)-based photodegradable amphiphilic polymers with temperature/pH/light-response

Photodegradable polymers containing nitrobenzyl esters groups and their derivatives (e.g., nitrobenzyl carbonate, NBC) have attracted considerable attention due to their precise UV-triggered degradation. Herein, we designed a novel NBC-containing monomer of 7-methyl-1-(2-nitrophenyl)-3-oxo-2,4,10-trioxa-7-azadodecan-12-yl methacrylate (NBC–N-EOMA) by integrating ethoxy/amino groups with NBC via precise spatial arrangement, and synthesized its homopolymer of P(NBC-N-EOMA) through reversible addition-fragmentation chain transfer (RAFT) polymerization. P(NBC-N-EOMA) exhibited triple responsiveness to temperature, pH, and light: it has a lower critical solution temperature (LCST) in pH = 5 buffer and a critical pH in aqueous solution, both regulable by the length of ethoxy chain, polymerization degree and concentration. UV/vis spectroscopy showed that after UV irradiation, the intensity of characteristic peak (265 nm) of NBC units decreased with irradiation time. 1 H NMR further revealed the reduced peak area of the methylene group in NBC, directly confirming UV-induced photodegradation, which also altered the LCST and critical pH of P(NBC-N-EOMA). Additionally, photodegradation-induced color change enabled photolithographic patterning of P(NBC-N-EOMA) on paper. Amphiphilic P(NBC-N-EOMA) self-assembled into spherical micelles with size tunable via acid or UV, and enabled controlled release of Nile Red (NR) under multi-stimuli. It also functioned as a hydrophobic block in amphiphilic diblock copolymers, retaining validated triple responsiveness and self-assembly. This work features simplified synthesis (high conversion, controllable molecular weight), high and tunable responsiveness of the homopolymer (no inter-block interference), and expandability via diverse hydrophilic blocks. Such polymers hold promise in photodegradable materials, photolithographic patterning, and biomedicine.