Controlling the Particle Size in Surfactant-Free Latexes from ω-Propenyl Oligomers Obtained through Catalytic Chain Transfer Polymerization AITranslate

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DOI：https://doi.org/10.1021/acsapm.1c00366

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The surfactant-free emulsion polymerization of styrene, butyl methacrylate, and methyl methacrylate was conducted under starved-feed conditions in the presence of ω-propenyl poly(methacrylic acid) (pMAA) oligomers, obtained through catalytic chain transfer polymerization, as a stabilizer. A range of monomer to oligomer molar ratios were used, which resulted in stable latexes without any sign of coagulation for more than two years at ambient temperature. Moreover, the effect of substituting pMAA for a nonionic stabilizer (poly(glycerol monomethacrylate)) or a low molar mass ionic surfactant (sodium dodecyl sulfate) on the final properties of the latex was evaluated. Kinetic studies gave insight into the process through which the stabilization occurs, indicating that in the initial stages, monomeric radicals react with the oligomer to form amphiphilic copolymers. Subsequently, micelles formed from these copolymers swell with the additional monomer, which then polymerizes through a free-radical mechanism. Thermogravimetric analysis showed that the polymers have thermal stability up to 420 °C, while differential scanning calorimetry revealed copolymer compatibility only at low monomer to oligomer molar ratios. Finally, static and dynamic light scattering techniques and scanning electron microscopy were used for the determination of the particle size and particle size distributions and the development of a linear regression model to summarize the particle size characterization, according to which an increase in monomer to oligomer ratios by a factor of x is associated with a proportional increase in the particle volume.