Effect of amount of emulsifier added in the second stage on morphology of composite latex particles

) we have explained the development of composite particle morphologies produced by seeded emulsion polymerization in terms of the ability of second stage polymer radicals to diffuse into, or "penetrate," the seed particles. This has been quantified (Stubbs et al., ibid) by calculating so-called "fractional penetration" values for the second-stage radicals. In this article the effect of the second-stage initiator type, specifically nonionic vs ionic initiators, on particle morphology is investigated. The question to be answered is whether charged (ionic) end groups (from the initiator) on second stage polymer chains "anchor" to the particle surface, making it more likely to form core-shell morphologies. This is investigated by using a poly(methyl acrylate-co-methyl methacrylate)[P(MA-co-MMA)] seed latex and polymerizing styrene in the second stage in a semibatch manner using various feed rates of styrene. At each feed rate one reaction was conducted using potassium persulfate as the initiator, which produces charged end groups, and another using VA-086 initiator, which produces uncharged end groups. The morphologies of the resulting particles were then observed by transmission electron microscopy. It is shown that under some conditions ionic initiators do make it more likely to obtain core-shell morphologies, but that this effect is not dominant under most conditions. The resulting morphologies agree quite well with the predictions of the fractional penetration calculations.

Section: Fractional Penetration Calculationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nonequilibrium particle morphology development in seeded emulsion polymerization. III. Effect of initiator end groups

Stubbs

Sundberg

2003

Morphologies and dynamic mechanical properties of core‐shell emulsifier‐free latexes and their copolymers for P(BA/MMA)/P(MMA/BA) and P(BA/MMA)/PSt systems in the presence of AHPS

Guo¹,

Tang²,

Hao³

et al. 2002

Different poly(methyl methacrylate/n-butyl acrylate)/poly(n-butyl acrylate/methyl methacrylate) [P(BA/ MMA)/P(MMA/BA)] and poly(n-butyl acrylate/methyl methacrylate)/polystyrene [P(BA/MMA)/PSt] core-shell structured latexes were prepared by emulsifier-free emulsion polymerization in the presence of hydrophilic monomer 3-allyloxy-2-hydroxyl-propanesulfonic salt (AHPS). The particle morphologies of the final latexes and dynamic mechanical properties of the copolymers from final latexes were investigated in detail. With the addition of AHPS, a latex of stable and high-solid content (60 wt %) was prepared. The diameters of the latex particles are ϳ0.26 m for the P(BA/MMA)/ P(MMA/BA) system and 0.22-0.24 m for the P(BA/MMA)/ PSt system. All copolymers from the final latexes are twophase structure polymers, shown as two glass transition temperatures (T g s) on dynamic mechanical analysis spectra. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: [3078][3079][3080][3081][3082][3083][3084] 2002

Synthesis of SBR/PMMA core/shell latices: The role of initiator and surfactant on particle morphology and instability performance

Moghbeli

Mohammadi

Bagheri

2007

Poly(butadiene-stat-styrene)/poly(methylmetacrylate), SBR/PMMA, structural latices were synthesized by using equal moles of different kinds of surfactants: anionic, nonionic, and anionic/nonionic mixture in a two-stage emulsion polymerization. The results indicate that the application of anionic surfactants for the first stage, accompanying sodium persulfate initiator, KPS, for both stages led to core/shell and raspberry morphologies depended upon the hydrophilic lipophilic balance (HLB) of the surfactant. On the other hand, a core/shell structure was observed for structural latices which were synthesized via application of nonionic or anionic/nonionic mixed surfactants along with azobisisobutyronitrile, AIBN, and KPS as first and second-stage initiators, respectively. The surface polarity and wettability of the seed particles and finally the tendency of the systems to gain the minimum surface free energy change are the basis for the observed morphologies. On the other hand, the stability of core/shell particles was investigated via incremental addition of an electrolyte, ammonium acetate, at temperature close to the glass transition of PMMA shell, 858C. The particle size measurement on destabilized samples showed that the core/shell latex only stabilized by anionic surfactant was considerabely microagglomerated with increasing the electrolyte content.