Synthesis of Micrometer‐Size Poly(Methyl Methacrylate) Particles by Utilizing Microsuspension Iodine Transfer Polymerization (ms ITP): Kinetic Approach

Abstract

In a previous work, microsuspension ITP (ms ITP) of methyl methacrylate (MMA) using iodoform (CHI3) as a chain transfer agent and benzoyl peroxide (BPO) as an initiator could be successfully carried out at 80 °C for the synthesis of micrometer‐size poly(MMA) (PMMA) particles without the byproduct of submicrometer‐size particles. Whereas, in microsuspension conventional radical polymerization (ms CRP) at the same conditions except for non‐use of CHI3, about half amount of PMMA was formed as submicrometer‐size byproduct particles by accompanying emulsion polymerization. In this article, kinetic simulations of ITP and CRP in bulk systems, which, respectively, correspond to those within MMA droplets in ms ITP and ms CRP, are performed using PREDICI software from CiTGmbH to understand the successful reason of the ms ITP of MMA. The simulation results of the ITP indicate that the concentrations of MMA oligomer radicals having BPO initiator fragment and vinyl group as end‐group, which seem to exit from MMA droplets and accompany emulsion polymerization in the aqueous medium in the ms CRP, remarkably decreased in the presence of CHI3. This strongly supports the idea “RED effect” proposed in the previous article to explain the success of the ms ITP of MMA.

Synthesis of Micrometer-Sized Poly(methyl acrylate) by Temperature-Step Microsuspension Polymerization with Iodoform Based on the “Radical Exit Depression” Effect§

“…It was reported that high R p w plays an important role in homogenous nucleation. 36 More specifically, from the view of the solubility of oligomers, the maximum monomer units of an oligomer radical (P max ) at 80 °C, which can still exit from monomer droplets is 4 for the PMMA oligomer, while that of the PMA oligomer is 26, which were calculated using eq 7 in the Supporting Information. This higher water solubility of the PMA oligomer caused the difficulty in the formation of microsuspension of MA.…”

“…Simulations for ITP and CRP of MA were conducted with PREDICI software from CiT GmbH (Rasfede, Germany) using the kinetic parameters shown in Table S1, in the same way as reported in the previous article. , The kinetic model was built based on the assumption of the fate of free radicals (Scheme S1) and was explained in detail in the simulation section in the Supporting Information. The simulation was composed of individual reaction steps: initiation, propagation, termination, and chain-transfer reactions and their kinetic coefficients.…”

Synthesis of micrometer-sized poly(vinyl acetate) particles through microsuspension iodine transfer polymerization: effect of iodine species in a water medium

“…† Simulation of the ITP of VAc was conducted using the PREDICI software from CiT GmbH (Rasfede, Germany) with the kinetic scheme and parameters shown in Tables S2 and S3, † as previously reported. 29,32 The kinetic model is explained in the simulation section of the ESI. † The simulation comprised the following individual reaction steps: initiation, propagation, termination, and chain transfer reactions, including their kinetic coefficients.…”

“…Meanwhile, only a few reports have described the use of ITP to prepare PVAc, 8,25,26 mainly focusing on homogenous systems, with only one example reported by Lacroix-Desmazes et al using a miniemulsion system. 8 When employing a hydrophilic monomer in a suspension or microsuspension system, the initiator or oligomeric radicals generated in the monomer droplets can easily exit from the droplets to the aqueous medium, resulting in the formation of submic-rometer-sized byproduct particles through emulsion polymerization, [27][28][29][30] which hinders the control of the molecular weight and molecular weight distribution in RDRP. Therefore, the synthesis of micrometer-sized particles through microsuspension polymerization of VAc (solubility in water: 2.3 g per 100 mL at 20 °C) without obtaining submicrometersized particles as a byproduct is challenging.…”

Iodine-influenced morphological evolution of micrometer-sized poly(methyl methacrylate)-block-poly(vinyl acetate) particles upon hydrolysis

“…The latter aim is usually regarded as the difficulty of hydrophilic monomers in a conventional suspension or microsuspension system, which is accompanied by submicrometer-sized particles since the homogenous nucleation in the aqueous phase is difficult to be restrained. [13][14][15][16] The success of the ms ITP of hydrophilic monomers relies on the radical exit depression effect, according to which the escaping monomer and oligomer radicals can be captured by the highly hydrophobic diiodomethyl group and iodine group from CHI 3 in the monomer droplet. 17,18 The ms ITP of methyl methacrylate (MMA) (solubility in water: 1.5 g per 100 mL, at 20 °C) 19 resulted in micrometer-sized particles.…”