Photoresponsive and UCST-Type thermoresponsive block Copolymer-Based composite micelles for Dual-Stimuli-Triggered selective and programmable release

The coordinated release of multiple substances presents a significant technical challenge, primarily due to their distinct release kinetics and potential intermolecular interactions. To address this, we developed a composite nanoreactor and strategically selected two hydrophobic fluorescent dyes, Coumarin 102 and Nile Red, as model payloads. Firstly, a photoresponsive block copolymer, P(DMA 50 - b -SPMA 60 ) ( P1 ), containing carbamate spiropyran methacrylate units, and a thermoresponsive block copolymer with an Upper Critical Solution Temperature (UCST), P(DMA 50 - b -SBMA 48 ) ( P2 ), were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. These copolymers self-assembled into micelles, which encapsulated Coumarin 102 and Nile Red within the hydrophobic cores of P1 and P2 , respectively. The individual stimulus-responsive release profiles were monitored via fluorescence spectroscopy. Composite nanoreactors were then prepared by physical blending the two loaded micelle types. The stability of the composite system was verified by fluorescence spectroscopy, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). Upon exposure to specific stimuli (light or temperature), selective release of the respective hydrophobic molecules was achieved: UV irradiation triggered a 80% release of Coumarin 102 from M3 micelles, while heating above the UCST induced a 75% release of Nile Red from M4 micelles. The composite micelles thus integrate multiple orthogonal stimulation responses with precise selective release control, offering a promising platform for advanced controlled-release applications in nanotechnology and biotechnology.