Polymerization Induced Phase Separation in Composite Latex Particles during Seeded Emulsion Polymerization

Abstract

Multiphase structured latex particles have been studied and produced for decades; however, the mechanism governing the polymerization induced phase separation process in such particles remains incomplete. These particles are typically produced by starting with a first, single phase polymer particle dispersion, and then a second polymer, nearly always thermodynamically phase incompatible with the first, is polymerized within those seed particles. The Gibbs free energy change upon demixing is the driving force inducing polymer−polymer phase separation during polymerization (PIPS). However, the ultimate extent of phase separation is dictated by resistances to mutual polymer chain diffusion within the latex particles. Here, we have elucidated and quantified the contributions of thermodynamic driving force and kinetic diffusive limitations to polymer−polymer phase separation within composite nanoparticles. We present a means to evaluate both the influence of chemistry and process conditions on a master plot profile predictive of a wide range of systems.

Surface Morphology Signature of Critical Separated Length and Glass Transition Temperature during Seeded Dispersion Polymerization

“…However, after the completion of polymerization, the extent of diffusion can be determined by the glass transition temperature measurements of the CS particles obtained from DSC. 17 The DSC results (Figurs 3f−j) suggest a significant phase separation for PAN, PMMA, and PS shells by their distinctive DSC derivative peaks, while there is a substantial degree of mixing for the PMA and the PnBA shells with PMMA core due to the closed T g peaks. It should be noted that we used the derivative of the reversing heat capacity curve to assess the details of the glass transitions presented in this form as peaks with a shape and area that relate to the uniformity of the system and to avoid confusion in interpreting the DSC data.…”

“…The molecular weight of the PMMA seed is considered to be 100 000 Da (see the Supporting Information), and the average δ of the polymer and the monomer is regarded as the δ for the radical chains. However, after the completion of polymerization, the extent of diffusion can be determined by the glass transition temperature measurements of the CS particles obtained from DSC . The DSC results (Figurs f–j) suggest a significant phase separation for PAN, PMMA, and PS shells by their distinctive DSC derivative peaks, while there is a substantial degree of mixing for the PMA and the PnBA shells with PMMA core due to the closed T g peaks.…”

“…Subsequently, separated radical chains aggregate on the core's surface to form a shell. 15,17 Herein, the resulting surface morphology is determined by the arrangement of macromolecules during the aggregation and diffusion of polymer chains on the surface 18 and in the bulk of seed particles. 17 The aggregation and diffusion processes in seed polymerization on core particles are influenced by the reaction media, the feeding order, the stabilizer type, and the cross-linking agent.…”

“…15,17 Herein, the resulting surface morphology is determined by the arrangement of macromolecules during the aggregation and diffusion of polymer chains on the surface 18 and in the bulk of seed particles. 17 The aggregation and diffusion processes in seed polymerization on core particles are influenced by the reaction media, the feeding order, the stabilizer type, and the cross-linking agent. 19−22 The reaction media influences the nucleation time and the participation length of polymer chains via the solubility and extent of polymer chains in it.…”

“…In this method, radical chains propagate up to a critical length, at which point they become insoluble in the reaction media, and phase separation occurs. Subsequently, separated radical chains aggregate on the core’s surface to form a shell. , Herein, the resulting surface morphology is determined by the arrangement of macromolecules during the aggregation and diffusion of polymer chains on the surface and in the bulk of seed particles …”