Seeded emulsion polymerization of styrene: influence of acrylic acid on the particle growth process

Abstract

ABSTRACT:The seeded batch emulsion copolymerization of styrene and acrylic acid was studied. The polymerization rate was investigated with pH as the main parameter. Some attempts were made to evaluate the average number of growing chains per particle during Stage II of the emulsion polymerization process. The final latex products were characterized by means of conductometric aqueous titration and potentiometric titration in an organic solvent mixture. The distribution of the acid groups over the aqueous phase, the particle surface, and the interior of the particles together with the kinetic results provided insight into important features governing the incorporation of acrylic acid. The results indicate that pH is the dominating parameter for the incorporation process. An optimal incorporation on the surface of the particles is observed for a low value of pH. In that case, all the acid groups are protonated.

BSA Adsorption on Differently Charged Polystyrene Nanoparticles using Isothermal Titration Calorimetry and the Influence on Cellular Uptake

“…At low pH values the AA is rather hydrophobic and at pH values above 5.5 AA is deprotonated and more hydrophilic (pK a of AA corresponds to 4.25). [28] Bearing in mind that the quantity of carboxylic groups on the particle's surface is very high, the ionic interactions might influence the coverage of the surface with BSA. As it was mentioned above, at pH ¼ 3, the adsorbed amount of BSA is higher than at pH ¼ 6 due to the stronger interaction between the anionic particle's surface and positive charges of BSA molecules.…”

Effect of itaconic acid on the wet scrub resistance of highly pigmented paints for architectural coatings

“…In this study, two methods were used for determining the carboxylic group's distribution: conductometry to evaluate the number of carboxylic groups on the surface of the latex particles, and titration with NaOH in methanol solution to determine the number of carboxylic groups inside and on the surface of the latex particles. 1,8,14,15 The concentration of carboxylic groups in the serum (water phase) was determined by centrifugation and conductometric titration by means of a mass balance, i.e., deduced from the initial amount of carboxylic monomer introduced and the determined amounts of carboxylic groups inside and at the surface of the latex particles. The number of carboxylic groups on the particle surface was determined by titration of a cleaned latex solution against a 0.05 N NaOH.…”

Effect of Carboxylic Acid Monomer Type on Particle Nucleation and Growth in Emulsifier-free Emulsion Copolymerization of Styrene-Carboxylic Acid Monomer

“…Hence, the participation of propagation in aqueous phase and its effect on R p could be neglected. 3,5,6 So R p is calculated from eq 3.…”

“…polymerization rate per particle or equivalently average number of propagating radicals per particle is also affected by the presences of carboxylic acid monomers. 3,[5][6][7][8] Shoaf and Poehlein 7,8 developed a model that describes the kinetics of particle growth in seeded emulsion copolymerization of styrene with acrylic and methacrylic acids. These authors confirmed the influence of events taking place in the aqueous phase on the basic mechanisms operating in the particle growth stage.…”

“…Most of the reported studies in the literature for emulsion polymerization systems involving carboxylic acid monomers have focused on the overall kinetic scheme in order to predict reaction rates, copolymer composition, particle concentrations and particle size. Recently, Slawinski et al 5,6 evaluated the average number of propagating radicals per particle during interval II of the emulsion polymerization process for seeded batch emulsion copolymerization of styrene and acrylic acid. The results indicate that pH generally has a minor influence on the polymerization rate and average number of propagating radicals per particle in the seeded systems.…”