Abstract
We develop a sequential flow process for the production of monodisperse poly (methyl methacrylate) (PMMA)/polystyrene (PS) composite particles through a soap-free emulsion polymerization of methyl methacrylate (MMA) using the first water-in-oil (W/O) slug flow and a subsequent seeded emulsion polymerization of styrene (St) using the second W/O slug flow. In this process, monodisperse PMMA seed particles are first formed in the dispersed aqueous phase of the first W/O slug flow. Subsequently, removal of the oil phase from the slug flow is achieved through a porous hydrophobic tubing, resulting in a single flow of the aqueous phase containing the seed particles. The aqueous phase is then mixed with an oil phase containing St monomer to form the second W/O slug flow. Finally, monodisperse PMMA/PS composite particles are obtained by a seeded emulsion polymerization of St using the second W/O slug flow. We compared the reaction performance between the slug flow and the batch processes in terms of particle diameter, monomer conversion, particle size distribution, and the number of particles in the system. We found that internal circulation flow within the slugs can enhance mass transfer efficiency between them during polymerization, which results in monodisperse PMMA/PS composite particles with a large particle diameter and a high monomer conversion in a short reaction time, compared to those prepared using the batch process. We believe that this sequential microflow process can be a versatile strategy to continuously produce monodisperse composite particles or core-shell particles in a short reaction time.
Highlights
Polymer/polymer composite particles have been applied to various applications such as coatings (Jiang et al, 2017), reinforced elastomers (Yu et al, 2017), high-impact plastics (Guo et al, 2003), and toughened plastics (Ning et al, 2020) since the functionality of polymer particles can be controlled by the combination of polymers and the morphology of polymer particles
We have reported that a soap-free emulsion polymerization of methyl methacrylate (MMA) using a W/O slug flow facilitates the rate of polymerization by high heat transfer in microreactor and enhanced mass transfer between liquid–liquid interface through internal circulation flow, which results in polymer particles with a large diameter and a high molar mass in a short reaction time (Watanabe et al, 2019)
A nucleation process is prevented and the second monomer can be only consumed by the seed polymer particles, which results in the formation of composite particles
Summary
Polymer/polymer composite particles have been applied to various applications such as coatings (Jiang et al, 2017), reinforced elastomers (Yu et al, 2017), high-impact plastics (Guo et al, 2003), and toughened plastics (Ning et al, 2020) since the functionality of polymer particles can be controlled by the combination of polymers and the morphology of polymer particles. Polymer/polymer composite particles are prepared via multistep polymerization process using a seeded emulsion polymerization (Cho and Lee, 1985). Various morphologies including core-shell (Vatankhah et al, 2020; Watanabe et al, 2020b), Janus (Tang et al, 2010; Chen et al, 2017), hollow (Kobayashi et al, 2007, 2009; Lv et al, 2008), and raspberry-like (Perro et al, 2006; Tolue et al, 2009) structures have been prepared by controlling thermodynamic and kinetic parameters during a seeded emulsion polymerization. Seeded emulsion polymerization has attracted attention as one of the most effective ways to produce polymer composite particles as well as control the morphology of particles. It requires a long time to produce polymer/polymer composite particles with a batch process due to time-consuming multiple polymerization steps
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