Recalculation of the monomer reactivity and experimental differences in emulsion and microemulsion copolymerizations of partially water‐soluble monomers

Abstract

On the basis of the copolymerization data for the emulsion and microemulsion polymerizations of ethyl acrylate and methyl methacrylate, the monomer concentrations at the copolymerization loci were calculated, with the assumption that the sum of their concentrations at the polymerization loci was equal to unity. The equivalency of the locus and feed concentrations, as for styrene, was invalid because of the partial water solubility of both the monomers. Consequently, the locus concentration rather than the initial feed concentration was used to recalculate the monomer reactivity at the actual site of polymerization, and this was called the true reactivity ratio. The apparent reactivity ratios for emulsion and bulk polymerizations were different, whereas those for microemulsion and bulk polymerizations were similar. This difference was attributed to the mode of polymerization in the emulsions and microemulsions, leading to different copolymer compositions for similar initial feed concentrations. This was verified experimentally from the thermal properties and particle size distribution measurements.

Revisiting emulsion polymerization to produce stable, translucent, nanolatex of partially water‐soluble monomers, ethylacrylate–methylmethacrylate

“…The monomer ratio [EA]/[MMA], is represented as L . Reactivities of EA and MMA used for calculation in emulsion medium are reported to be 0.25 and 1.44 respectively by us earlier 18…”

“…Appearance of two T g 's can be attributed to the formation of a diblock copolymer due to large difference in the monomer reactivities18 ( r MMA = 1.44, r EA = 0.25). However, such a possibility can be denied as the polymer characterization is done below 10% conversion and copolymer synthesized in microemulsion showed single T g 18 Hence the appearance of two T g s confirms the formation of two types of copolymer chains with different composition arising from micellar and homogeneous nucleation. The polymer generated via micellar polymerization is expected to have a greater fraction of the less water soluble monomer, MMA and corresponds to the higher T g .…”