Comblike polymers with octadecyl side chain and carboxyl functional sites:Scope for efficient use in miniemulsion polymerization

The scope for the efficient use of comblike polymers to synthesize polystyr ene latexes with a narrow distribution of particles in a size range of 100- 250 nm has been demonstrated. The polymers comprising of octadecyl side cha ins with a statistical distribution of carboxylic groups and in the molecul ar weight range of ca. 4 x 10(4) have been synthesized by free radical poly merization reaction. The characterization of polystyrene latexes synthesize d using these comblike polymers with different acid compositions, 0.11 and 0.31 mole fraction of both acrylic and methacrylic acid in the feed, with r espect to the particle size, the surface coverage of the latex surface with carboxylic groups, and the surface tension of the latex throws interesting information on the probable; mechanism underlying this typical miniemulsio n polymerization system. The high efficiency of the polymer in miniemulsion polymerization suggests that the polymer undergoes a typical reorganizatio n process with octadecyl groups covering the styrene oil phase and the reta ining carboxylate groups being located at the interface. The stability of t he miniemulsion droplets prior to polymerization against aging is in suppor t of the suppression of Ostwald ripening and coalescence processes and prov es that the polymer acts both as a surfactant and-although located at the i nterface-as an osmotic agent. Preservation of the original particle size an d distribution throughout polymerization underlines the predominance of dro plet nucleation.