Modulating Structural Stability And Acid Sensitivity Of Photosensitive Polymer Micelles Via UV Irradiation

Photo-responsive polymers were widely used for shape memory materials, intelligentsensor, drug controlled-release and other fields. It is important in academic andapplication to explore the state dependence of photo-chemical reaction. Based on thedetailed literature research, this thesis describes the structurally stable and acid-sensitivemicelles whose stability and acid sensitivity can be widely tuned simply via a batch UVirradiation. To this end, the well-defined poly（5-ethyl-5-methacryloyloxymethyl-2-styryl-[1,3]dioxane）-block-poly[poly（ethylene glycol） monomethyl ether methacrylate]（PEMSD-b-PPEGMA） copolymers with identical chain lengths of PEMSD blocks at DP=52but different chain lengths of PPEGMA blocks were synthesized via RAFTpolymerization under mild visible light radiation at30oC. The results demonstrated thatirradiating the homogeneous acetone solution solely induced Z-isomerization, withoutdetectable dimerization of cinnamyl groups. This Z-isomerization did not affect theformation of regular and spherical core-shell micelles of PEMSD₅₂-b-PPEGMA₄₀inacetonitrile. However, irradiating the bulky PEMSD chains of100%E-cinnamylPEMSD₅₂-b-PPEGMA₄₀in nanoscale-confined micellar cores solely induced thedimerization without detectable Z-isomerization. Z-isomerization remarkably improvedthe acid stability of the bulky PEMSD chains in micellar cores. Irradiating theZ-isomerized micelles for3min led to the structural stabilization but without changingthe acid sensitivity; while irradiating for30min remarkably improved the acid stabilityof the micelles. It can be concluded, the acid-sensitivity of micelles can be widely tunedby the dimerization of bulky Z-isomerized PEMSD chains in micellar cores. This thesisprovides a new avenue toward photo-controlled water soluable polymer. It shows greatapplication potential in drug controlled-release.