Synthesis and characterization of model carboxylated latexes for studies of film formation from latex blends

Poly(n-butyl methacylate-co-n-butyl acylate) [P(BMA/BA)] soft latexes (carb oxylated and noncarboxylated) were synthesized using a semicontinuous emuls ion polymerization process that was designed on the basis of a theoretical calculation to determine the suitable surfactant [i.e., sodium dodecyl sulf ate (SDS)], monomer, and water feed rates to maintain a constant particle n umber throughout the polymerization (guaranteeing monodispersity in the par ticle size), to obtain a homogeneous copolymer composition, and to independ ently control the particle size and carboxyl group concentration. The exper imental results support the theoretical calculation. The surface coverage o f the carboxyl groups present on the soft latex particles ranges from 7.6 t o 21.9% for a series of latexes with particle sizes around 120 nm. Tn anoth er series of latexes, the particle size was varied over a range from 120 to 450 nm. Monodisperse carboxylated polystyrene hard latexes were synthesize d by shot growth (batch) and semicontinuous processes. The shot growth meth od is somewhat inflexible in providing more choices in surfactant, particle size, and surface carboxyl coverage. A semicontinuous process designed usi ng a similar method used for the synthesis of P(BMA/BA) latexes successfull y eliminated the drawbacks of the shot growth process. In this way, the cha nges in the surface carboxyl coverage (varies from 0 to 77.2% ) was indepen dent of the particle size, which was precisely controlled by the amount of styrene fed under suitable styrene and SDS feed rates. (C) 2000 John Wiley & Sons, Inc.