Facile preparation of environmentally friendly and low-cost thermally responsive microspheres through suspension-emulsion polymerization

Thermally responsive microspheres (TRMs) have received increasing attention due to their unique temperature-dependent expansion performance. In this work, the preparation of a non-toxic, environmentally friendly, and low-cost TRM was investigated using non-nitrile monomers in suspension-emulsion polymerization. Various TRMs were prepared with different dispersant and emulsifier concentrations, various core materials and polymerization times to study the thermal expansion behavior, thermal response and the mechanism of microsphere polymerization, respectively. The optimized conditions, involving nano-SiO₂ as a dispersant, sodium dodecyl sulfate as an emulsifier, azobisisobutyronitrile as an initiator, as well as styrene, methyl acrylate, methacrylic acid, and methyl methacrylate at a certain mass ratio with a 16-hour reaction time at 65 °C, enabled the production of TRMs with stable spherical structures, high expansion ratios, and smooth, defect-free surfaces. This work provides a facile and environmentally friendly strategy for preparing TRM, which has the potential to be used in industrial applications.