Mass Transfer in Miniemulsion Polymerisation

Abstract

Summary: The use of very hydrophobic monomers in heterogeneous polymerisations is restricted because of insufficient mass transfer as a result of limited aqueous phase diffusion. Experimental evidence for a mass transfer mechanism in miniemulsion polymerisation that is based on the direct interaction between droplets as well as between droplets and particles ('collisions') rather than monomer diffusion is presented. Mass transfer that results in the formation of a copolymer in the miniemulsion polymerisation of a mixture of lauryl methacrylate and 4-tertbutyl styrene, is almost non-existing when physical contact between individual droplets is prevented by a membrane. However, monomer transport by diffusion is observed in reference experiments with more hydrophilic monomers.

Solution and aqueous miniemulsion polymerization of vinyl chloride mediated by a fluorinated xanthate

“…Furthermore, mass transfer of VC would also contribute to the concentration fluctuation of RAFT agent. Jansen et al have reported that the mass transfer of relative hydrophilic monomer occurs through the collisions between droplets (or latex particles) and the diffusion to aqueous phase in miniemulsion polymerization . Because VC is slightly soluble in water (20 g/1000 g in SDS solution), the mass transfer of VC induced by collisions between droplets (or latex particles) and the diffusion to water phase would take place in polymerization, leading to the different concentrations of RAFT agent in droplets (or latex particles) (Scheme ).…”

“…Jansen et al have reported that the mass transfer of relative hydrophilic monomer occurs through the collisions between droplets (or latex particles) and the diffusion to aqueous phase in miniemulsion polymerization. 42 Because VC is slightly soluble in water (20 g/1000 g in SDS solution), 43 the mass transfer of VC induced by collisions between droplets (or latex particles) and the diffusion to water phase would take place in polymerization, leading to the different concentrations of RAFT agent in droplets (or latex particles) (Scheme 1). To further confirm the effects of concentration fluctuation of RAFT agent in droplets (or latex particles) on the molecular weight distribution of PVC in miniemulsion polymerization, RAFT suspension polymerization of VC with the same recipe was also carried out for comparison.…”

On the Reaction Characteristics of Miniemulsion Polymerization with Aqueous Phase Initiation – Experiments and Modeling

“…In the latter case, an increase in particle number was observed, which was attributed to droplet budding, i.e., the splitting of nucleated particles throughout polymerization. Mixtures of separately prepared miniemulsion droplets, each consisting of only one monomer, showed a copolymer after polymerization rather than two separate homopolymers . Ugelstad et al derived a theoretical relationship between the particle diameter and the volumetric growth rate for seeded emulsion systems, thereby showing that concentration differences between differently sized particles can occur during polymerization, possibly resulting in monomer redistribution.…”

Monomer Transport in Emulsion Polymerization III Terpolymerization and Starved‐Feed Polymerization

“…Jansen et al. [ 11 ] studied the miniemulsion polymerization of highly water‐insoluble monomers and postulated that what monomer transport is occurring (because not all droplets become particles as in the idealized concept of a miniemulsion) occurs via droplet–droplet and droplet–particle collisions.…”