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 CaCO3 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 CaCO3 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 365nm. The loaded macromolecules could be released upon UV irradiation, exhibiting the microcapsules' potential applications in the field of controlled release.