Fast and facile one-step synthesis of monodisperse thermo-responsive core-shell microspheres and applications

Highly monodisperse PMMA microspheres covered with a thermo-responsive shell were synthesized in a single step by means of photoinitiated RAFT dispersion polymerization at room temperature. Thermoresponsive macro-RAFT agents (P(mPEGA-co-MEA)-TTCs) with different lower critical solution temperatures (LCST) were used as stabilizers in the process. Particle yields of over 95% were achieved within 45 min of UV irradiation, showing a fast process. The microspheres obtained were well-dispersed in water at a temperature below the LCST, and precipitated from the aqueous dispersion at a temperature above the LCST, exhibiting reversible thermo-responsive properties. The particle size can be precisely controlled by adding a monomer to the reaction in batches, and the microspheres maintained their high uniformities during the reaction. The thermo-responsive PMMA microspheres can be effectively conjugated to proteins via the carboxyl groups on the macro-RAFT chains. A thermo-responsive PMMA/ZIF-8 core-shell structure was also synthesized by using P(mPEGA-co-MEA)-b-PAA stabilized PMMA microspheres as the template, and exhibited good adsorption properties for methylene blue.