Date of Degree
PhD (Doctor of Philosophy)
Chemical and Biochemical Engineering
Guymon, C. Allan
First Committee Member
Lee, Tai Yeon
Second Committee Member
Jessop, Julie L. P.
Third Committee Member
Rethwisch, David G.
Fourth Committee Member
Photopolymerization is a growing field within the realms of polymer and material science. With diverse applications, ranging from coatings and adhesives to newer technologies such as 3D printing photopolymerization continues to increase its prevalence and influence. This research examines fundamental structure property relationships between large prepolymer structures within a formulation and the resulting impact on thermo-mechanical properties in photocurable resins. Most prepolymer molecules utilize a “one pot” synthesis with little to no control over the placement of photoreactive moieties such as epoxies and (meth) acrylates. We have utilized novel prepolymer molecules synthesized using controlled radical polymerization to allow direct control over the placement of reactive groups. The ability to control the location of reactive groups in prepolymer molecules can also lead to the formation of multiple domains within the resulting photocured thermoset. This separation is achieved by concentrating the reactive groups at specific locations in the prepolymer backbone, e.g. at the end or near the center of the prepolymer molecule. The nonreactive groups may form one domain within the thermoset network while the reactive portion of the prepolymer forms a second phase with reactive diluent molecules. Additionally, various architectures allow greater control over polymer network formation and crosslink density. Through these manipulations of macromolecular architecture, we have been able to manipulate various thermo-mechanical properties. Using various architectured prepolymer, we have been able to generate materials with multiple glass transitions while also increasing the rate of reaction and total conversion as compared to randomly functionalized control formulations.
Photopolymerization is the process of joining multiple molecules together by exposing them to light. This process has been used to make coatings and adhesives cheaply and efficiently as well as enabling new technologies like 3D printing. In order to provide new materials with the necessary properties to answer the problems of tomorrow, this research examines how the structure of the initial molecules influence the final material properties. Special, chemically reactive large molecules, or prepolymers, were made with the placement of the reactive groups deliberately chosen to influence and create differences at the nanoscale within the network. By controlling how the nanoscale structures are formed, we show that is it possible to produce materials that are very stiff while also maintaining high elongation. By controlling how the special molecules are made we are able to further control the ways in which the molecules interact. Some methods allow for the final material to be responsive to continued light exposure. The continued light exposure allows for the networks to rearrange and assume a more relaxed conformation which produces a more homogenous network with improved stiffness and resistance to sudden deformations, two critical measures of industrial industrial and academic interest. Overall, this work lays the foundation for further advancements in the design of specialty molecules and design of photopolymer systems.
Controlled Radical Polymerization, Photopolymerization, Structure Property Relationships
xiii, 166 pages
Includes bibliographical references.
Copyright © 2017 Jon Paul Scholte
Scholte, Jon Paul. "Effects of prepolymer structure on photopolymer network formation and thermomechanical properties." PhD (Doctor of Philosophy) thesis, University of Iowa, 2017.