Photo-responsive polyethyleneimine microcapsules cross-linked by ortho-nitrobenzyl derivatives

Intelligent capsules are widely used as carriers for loading small molecules and particles for their capacity to respond to environmental stimuli. In this study, photo-responsive polyethyleneimine (PEI) microcapsules were fabricated using 4-bromomethyl-3-nitrobenzoic acid (BNBA) bearing a photodegradable ortho -nitrobenzyl group as a cross-linker. PEI-doped CaCO 3 particles were used as the sacrificial templates, in which the PEI molecules were cross-linked by BNBA molecules under the activation of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) and N,N-diisopropylethylamine (DIEA). After the removal of CaCO 3 particles by hydrochloric acid , the PEI–BNBA capsules were obtained. Since the C–N bond that formed via reaction of benzyl bromide and amine is photo-cleavable, the capsules could be decomposed under UV irradiation at 365   nm. The loaded macromolecules could be released upon UV irradiation, exhibiting the microcapsules’ potential applications in the field of controlled release.