Photodegradation of chitosan decorated by titanium dioxide: The potential to serve as a responded microcapsule shell

In order to develop the UV responded material, chitosan (CS) was decorated by TiO₂, and the mechanism of UV-mediated photodegradation of CS-TiO₂ was analyzed. In this study, the changes in color, microstructure, degradation rate, thermal stability, and structure under different treatments were explored. The results showed that CS could be degraded by UV light. With the increase of irradiation time, the degradation rate of CS significantly raised, and was up to 18.41 %. L^⁎ value markedly decreased, a^⁎ value and b^⁎ value significantly increased. The photodegradation process fitted with first-order kinetics. The degradation was improved when reducing scale of TiO₂ from 10 nm to 102 nm, increasing TiO₂ addition, and increasing UV light power. UV irradiation would promote the breakage of β-1,4 glycosidic bonds and deacetylation of CS. After UV irradiation, the crystalline structure of CS was destroyed and thermal stability was reduced. Tea tree essential oil microcapsules were constructed by using CS-TiO₂ as a UV-light-sensitive shell material and could achieve a rapid UV-light-triggered release process, with a significant increase in volatile substances after UV irradiation. Thus, CS decorated by TiO₂ could function as a controlled-release shell for microcapsules, while UV light could act as a switch to modulate the release process.