Preparation of Thermoresponsive Microgels from Acrylamide and Diacetone Acrylamide with Adjustable Responsive Temperature and Size via Precipitation Polymerization

Thermoresponsive microgels are a kind of soft and wet material exhibiting various potential applications such as smart windows. As a concept of proof, poly(N-isopropylacrylamide) based thermoresponsive microgel shows excellent promise in thermochoromic smart windows. While relatively expensive monomers lead to an unacceptable cost when they are used as building materials. In this work, efforts are made to exploration of an alternative for poly(N-isopropylacrylamide) reducing the cost of thermoresponsive microgels. For this purpose, industrial chemicals acrylamide (AM) and diacetone acrylamide (DAAM) are employed to synthesize microgels through free radical precipitation polymerization. Although both homopolymers of acrylamide and diacetone acrylamide are not thermoresponsive. Their copolymers exhibit typical lower solution temperature solution (LCST) behaviors, which confirm the feasibility of the envisaged. Further, the influence of synthetic conditions including monomer ratio, concentration of surfactant, and polymerization temperature, on the size and responsive temperature of microgels is investigated. Ultimately, cost-effective thermoresponsive microgels are prepared with adjustable diameters from 1.6 to 4.5 µm and responsive temperature from 19.3 to ≈70.0 °C.