New Avenues to Hybrid Polymer/Inorganic Nanoparticle Materials Using Surface-Initiated Ring-Opening Metathesis Polymerization and Reaction-Induced Phase Transitions

Open Access
- Author:
- LaNasa, Jacob
- Graduate Program:
- Materials Science and Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 03, 2021
- Committee Members:
- Robert Hickey, Chair & Dissertation Advisor
Enrique Gomez, Major Field Member
Elizabeth Elacqua, Outside Unit & Field Member
Lauren Zarzar, Major Field Member
John Mauro, Program Head/Chair - Keywords:
- Hybrid materials
polymer
nanoparticle
synthesis - Abstract:
- Hybrid materials made from polymer and inorganic nanoparticles offer functionality that assists in creating advanced materials by either reinforcing existing polymer properties, or by introducing inorganic material properties. As a result, these hybrids can be tailored for use in a number of exciting areas including biomedical tissue engineering, energy storage, and high temperature applications where specific properties are desired. The material processing and resulting dispersion state of the inorganic nanoparticles within the polymer phase are critical and non-trivial considerations that influence the expression of enhanced properties, and need to be carefully addressed for desirable performance. An effective strategy for controlling dispersion in hybrid materials is to modify the nanoparticle surface with ligands or polymer chains. However, many established surface-initiated polymerization techniques yield a subset of graft chemistries that do not favorably interact with polyolefins used widely across consumer and industrial materials. To expand the versatility of polymer-grafted nanoparticles, a surface-initiated ring-open- ing metathesis polymerization (SI-ROMP) technique was developed to graft unsaturated backbones from particle surfaces. Strategies to quantify and mitigate unfavorable chain transfer during polymerization were utilized, as chain transfer is a key obstacle to SI- ROMP implementation. In addition, the unsaturated polymer backbones obtained with SI-ROMP were hydrogenated to drive crystallization from the particle surface or functionalized with macromolecules to access non-linear bottlebrush graft architectures. The versatility of these new capabilities enhance polymer-grafted nanoparticle functionality, structural conformation, and thermal response and can be used to influence properties in new and advanced materials. In addition, a new processing method termed a reaction-induced phase transition (RIPT) was developed to stabilize polymer-functionalized nanoparticles in polymer matrices and dictate dispersion state. Surface-functionalized nanoparticles can be easily dispersed within a polymer matrix though an in situ polymerization where nanoparticles are initially well-solubilized in a monomer solution prior to polymerization. The in situ polymerization arrests particle mobility as the matrix increases in chain length. During this process, particles are stabilized or driven to phase separate based on thermodynamic interactions between the matrix and the functional surface ligand. This method incorporates scalable polymerization processes to develop well-dispersed hybrid polymer/inorganic nanoparticle materials at a bulk scale. The development of these methods create new avenues to improved particle dispersion needed for advance material design.