Kinetics and particle size control in non-stirred precipitation polymerization of N-isopropylacrylamide

A novel non-stirred precipitation polymerization for rapid small-scale synthesis of monodisperse temperature-sensitive poly(N-isopropylacrylamide) microgels is introduced. A practical framework for the final particle size control is established, and low-temperature synthesis is highlighted as an easy alternative for producing large particles in contrast to the temperature ramp method. Furthermore, in situ 3D-DLS method is used to determine the kinetic rate law of the precipitation polymerization of N-isopropylacrylamide. The power law exponents for the reaction are determined to be 0.97 ± 0.12 and 0.46 ± 0.01 for the monomer and the initiator concentration, respectively. In conjunction with other evidence, it is suggested that the reaction follows conventional radical polymerization kinetics and takes place in the continuous phase. Number concentration of particles in the batch is recognized to be the determining factor for the final particle volume of the microgels.