Polymer micelles stabilization on demand through reversible photo-cross-linking

An all-optical strategy, reversible photo-cross-linking, for the stabilization on demand of polymer micelles was analyzed. The chemical structures of the amphilic diblock copolymers were synthesized using atom transfer radical polymerization (ATRP), which contain pendent coumarin moieties for the reversible photodimerization and cleavage. The micelles of sample p1 could be obtained by adding water in its DMSO solution, while micelles of p2 could be formed upon addition of water in its THF solution. The absorption of coumarin moieties at around 320 nm decreased with time, when the micellar solution was exposed to UV light, indicating the occurrence of dimerization in the micelles. The result show that through the use of reversibly photocontrolled dimerization of coumarin moieties incorporated in a diblock copolymer, micelles can be cross-linked by light illumination at two different wavelengths.