From Cauliflowers to Microspheres: Particle Growth Mechanism in Self-Stabilized Precipitation Polymerization

Self-stabilized precipitation (2SP) polymerization enables the facile synthesis of uniform polymer spheres with sizes ranging from 100 nm to 3 μm, without the need for stabilizers or cross-linkers, even at high monomer concentrations of up to 30%. While previous studies have extensively explored the influence of reaction conditions on the size and uniformity of microsphere products, their impact on particle morphology has received less attention. In this work, we demonstrate that particle growth in 2SP polymerization primarily occurs via the adsorption of polymers from the solution onto the particle surface, leading to an increase in particle circularity and a smoother surface. The surface roughness of the particles is controlled by the aggregation of primary particles and the subsequent polymer adsorption process during the growth stage. Smooth microspheres are obtained under conditions of moderate monomer concentration, high initiator concentration, and elevated temperature. Our findings highlight the significance of the particle growth process in determining particle morphology in addition to the well-established role of polymer-solvent interactions during precipitation polymerization.