Date of Award

Fall 2023

Project Type

Dissertation

Program or Major

Chemistry

Degree Name

Doctor of Philosophy

First Advisor

John Tsavalas

Second Advisor

Gonghu Li

Third Advisor

Marc Boudreau

Abstract

Waterborne technology highlights the advantage of using water as the dispersed media to replace the need for organic solvents. Emulsion polymerization is one of the most important techniques to produce functional polymer colloids of industrial importance. Besides the choice of monomers in the reaction, composite particle morphology significantly influences the mechanical properties of the materials in the applications of architectural coatings, adhesives, printing inks, and impact resistant plastics. Generally, emulsion polymerization produces spherical particles in the presence of water due to surface tension forces. In seeded emulsion polymerization, composite particles containing two incompatible phases can lead to various anomalous structures in either an equilibrium state (thermodynamic control) or a non-equilibrium state (kinetic control). Both oligomer diffusion and polymer diffusion after termination dictate the process of morphological transition. Non-equilibrium states usually describe the structure restricted by polymer diffusion without achieving the lowest energy configuration. The diffusion coefficient during the reaction is not constant but dynamically changes in response to the varying reaction conditions. Morphology control in a non-equilibrium state remains an essential subject of study, as it has yet to be fully understood. This thesis primarily focuses on the mechanistic perspective of non-equilibrium morphology by investigating polymer diffusion and oligomer radial penetration in local conditions. The aim is to establish guidelines and methods in morphology prediction. In seeded emulsion polymerization, glassy preseeds (Tg,seed ≫ Trxn) limit the diffusion of incoming oligomers resulting in the formation of second-stage polymers in the outer region of the composite particles due to high internal viscosity. Although non-spherical particles (lobed particles) in the system of poly(methyl methacrylate)/poly(hexyl methacrylate-co-styrene)(P(MMA)/P(HMA-coSTY)) was previously reported, the detailed mechanism and their morphological features have not been fully explored. Several possible morphological features are revealed, and relevant parameters are determined. The size of the particles and the weight ratio of the 1st and 2nd stage polymer significantly impact the structure. Through the post-annealing process, it is feasible to achieve anon-equilibrium morphology with a controlled number of lobes on the surface of the particle. On the other hand, a dynamic simulation approach was established to predict radical diffusion behaviors when radical penetration is allowed. The simulated results, including thermal properties (Tg) and morphological features, agree with the experimental observations reported in the literature. Lastly, the applications of functional polymer colloids were investigated in seeded emulsion polymerization. The 3D porous scaffold was produced through the assembly of multilobed particles. The findings indicate that the non-spherical nature of particles effectively promotes porosity compared to spherical particles. Furthermore, catechol-functionalized adhesives were successfully synthesized with a carefully selected monomer pair under a starved condition. A high conversion latex is obtained without any side reaction with the presence of oxidizing agents in the radical polymerization.

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