Electrolytes on governing particle coagulation and size distribution in the emulsion polymerization of butyl acrylate

Poly (butyl acrylate) (PBA) latices with controllable particle size (90–350 nm) were synthesized via one-step batch emulsion polymerization in the presence of different species of electrolyte. The evolution of particle size and number as a function of monomer conversion were tracked in order to investigate the effect of electrolyte species on the particle stability. For electrolyte with different anions, the particle size of final latices decreased with increasing pH of the aqueous phase and the sequence was Na₂CO₃ < NaHCO₃ < Na₂C₂O₄ < NaCl, latices with Na₂SO₄ showed some particular performance and possessed of a particle size up to 347.4 nm; for electrolyte with different valences of counter ion, while achieving the similar particle size (Ca. 120 nm), an obvious variance in ionic strength was found (0.03, 0.016 and 0.0035 mol kg⁻¹ for Na⁺, Mg²⁺ and Al³⁺). It indicate that electrolyte affects the particle stability by adjusting the pH of the aqueous phase and ionic strength, further controls the particle coagulation. As a result, latices with designated final particle size and distribution can be obtained by choosing the appropriate type and concentration of electrolyte.