Kinetics of (CO)polymerizations at the surface of inorganic submicron particles in emulsion‐like systems

Hydrophilic TiO2 particles were modified with two different titanates and thus made hydrophobic. “Emulsion” polymerizations were carried out in aqueous dispersions of these particles, stabilized with an anionic surfactant. Polymerization kinetics were determined using a densitometer. The effect of several parameters, like surface modification, surfactant and initiator concentration, and stirring speed on polymerizations were studied. Depending on reaction conditions two competitive polymerizations can take place: one in which polymer is formed at the particle surface and one in which free polymer particles are formed. The TiO2 was modified with a titanate containing a methacrylic acid ester, which was used as a comonomer. Thus a chemical bond between TiO2 particles and polymer was obtained. These polymer encapsulated inorganic particles may offer interesting perspectives in those cases, where a good coupling between particles and matrix is important, for instance in latex paints and in polymer composites.