화학공학소재연구정보센터
Journal of Applied Polymer Science, Vol.108, No.6, 4096-4107, 2008
Seeding as a means of controlling particle size in dispersion polymerization
Two distinctively different seeded dispersion polymerization processes employing micron and sub-micron size seed particles, respectively, have been used to gain a better mechanistic understanding of the dispersion polymerization process. Using monodisperse micron-size PMMA particles as seed, it was found that when low monomer/polymer ratios (M/P < 2.50) were used in methyl methacrylate (MMA) seeded dispersion polymerizations, particle growth dominates and the number of particles remains unchanged (i.e., narrow distributions are preserved). However, when higher M/P ratios (>2.50) were applied, bimodal or trimodal particle size distributions were produced, which is considered to result from the competition between particle growth and secondary nucleation. When small amounts of submicron seeds were used with the initial intention of gaining a better understanding of the nucleation process, it was surprisingly found that the final number of micron size particles was nearly the same as the initial number of submicron seed particles over a relatively wide range of reaction conditions, including seed, initiator, stabilizer, and monomer concentrations, and the medium composition. These results indicate that within certain limits seeded dispersion polymerization can be a more robust means of controlling particle size than ab initio dispersion polymerization in terms of reproducibly producing a target particle size. (C) 2008 Wiley Periodicals, Inc.