Effect of sulfonated 3-pentadecyl phenyl acrylate as surfmer in the emulsion polymerization of styrene: synthesis and polymer properties

In this work, the evaluation of a newly developed anionic polymerizable surfactant (surfmer), viz., sulfonated 3-pentadecyl phenyl acrylate, in the emulsion polymerization of styrene and its effect on the polymer properties is reported. The results were compared with the commercially available non-reactive anionic surfactant sodium lauryl sulfate. The surfmer has a low critical micellar concentration value of 40.11 mg/L (8.7 × 10⁻⁵ mol/L) in comparison to 2,400 mg/L (8.28 × 10⁻³ mol/L) for sodium dodecyl sulfate. Nanosized polystyrene dispersions with varying concentration of this surfmer were prepared and characterized for conversion, particle size, and size distribution at a fixed monomer/water ratio of 0.1. The particle radii decreased from 560 nm for the surfactant-free dispersions to 45 nm for the dispersion with 2.3 mol% surfmer. Increasing surfmer content above this concentration did not further affect the particle size but increased the width of the particle size distribution. Transmission electron microscopy results along with particle size data show that with increasing surfmer content the particle size distribution broadens, and film formation is facilitated. The microstructure analysis of the copolymers using infrared and ¹H-NMR spectroscopy confirms that the surfmer is chemically attached to the polymer chains. The effect of the ionic sulfonate groups and the alkyl chains of the surfmer moieties on the polymer properties have been studied through measurement of dilute solution viscosity and thermal and viscoelastic properties. These results indicate that the behavior of surfmer-containing polymers resembles that of plasticized ionomers.