Synthesis of Micrometer-Sized Poly(methyl acrylate) by Temperature-Step Microsuspension Polymerization with Iodoform...

Previously, we have reported the successful preparation of micrometer-sized poly(methyl methacrylate) particles without submicrometer-sized byproduct particles by microsuspension iodine-transfer polymerization (ms ITP), in which the radical exit depression (RED) effect was expected, with the benzoyl peroxide initiator at 8 wt % relative to the monomer. However, it was difficult to apply it simply under a similar condition for methyl acrylate (MA), which is more hydrophilic than methyl methacrylate (MMA), because the polymerization rate in the water phase (R_p^w) arising from the oligomer radicals exiting from the monomer droplets is high, resulting in a lot of submicrometer-sized byproduct particles. In this study, the problem was overcome by utilizing a two-step temperature process in the microsuspension polymerization with iodoform (ms I) of MA, which supports the proposed mechanism in the ms ITP of MMA in the previous paper. Although the control of the molecular weight (M_n) and the molecular weight distribution (M_n/M_w) was restricted, the preparation of micrometer-sized particles without byproduct particles was realized and a high conversion was reached within a practical time that meets the demands of the industry by utilizing the ms I. The optimal conditions for MA were 70 °C for 2 h, followed by 80 °C for 4 h with a high content of initiator (8 wt % relative to a monomer).