Abstract
The development of photo-responsive capsules to tune and control the sustained-release of encapsulated actives is a fascinating and challenging route to improve the performances and effectiveness of a wide range of delivery applications. In this work, we report the preparation of visible light-responsive capsules obtained via oil-in-water interfacial polycondensation between modified diacyl-chloride azobenzene moiety and diamine flexible spacer in the presence of cross-linkers with different structures and functionalities. The effect on the release profile of the encapsulated perfume oil was investigated using three flexible spacers with different lengths (1,8-diaminooctane; 1,6-diaminohexane and 1,4-diaminobutane) and two types of cross-linkers (1,3,5-benzenetricarbonyl trichloride and melamine). We analyzed how the properties of microcapsules can be tailored changing the design of the shell structure. Fine tuning of the perfume release profiles was obtained. The changes in capsules size and morphology due to visible light irradiation were monitored via light scattering, optical microscopy and atomic force microscopy. Perfume release was 50% faster in the systems prepared with melamine as the cross-linker. Modelling studies were carried out to support the discussion of the experimental results.
Highlights
Microcapsules (MC) are vastly investigated core-shell systems able to protect, deliver and stabilize many substances, entrapping them in a core part of a well-defined shell
We demonstrated that the properties of the microcapsule walls and the release of encapsulated perfume oil could be triggered by exposure to visible light
99.5% of perfume was encapsulated in the capsules prepared with the melamine as the cross-linker, independently of the type of diamine used for MC wall formation
Summary
Microcapsules (MC) are vastly investigated core-shell systems able to protect, deliver and stabilize many substances, entrapping them in a core part of a well-defined shell. The process is reversible and thermal Z-E isomerization could occur spontaneously in the dark owing to the thermodynamic stability of the E isomer [32] These molecular changes represent a powerful strategy for modulating microcapsule shell structural and functional properties in a controlled way. We demonstrated that the properties of the microcapsule walls and the release of encapsulated perfume oil could be triggered by exposure to visible light. The effect of three flexible spacers with different lengths (1,8-diaminooctane; 1,6-diaminohexane and 1,4-diaminobutane) and two types of cross-linkers (1,3,5-benzenetricarbonyl trichloride and melamine) on the release profile of the encapsulated perfume oil was investigated
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