Design and synthesis of flexible and functional polybenzoxazine thin films
Polybenzoxazines offer the unique ability to incorporate a variety of properties and functionality into a single polymer network through simple synthetic techniques. However, within benzoxazine materials exist certain drawbacks of which brittleness is the primary issue when exploring thin film applications. This brittleness leads to poor mechanical stability and would reduce the lifetime of any device sought after. It is, however, through the simplistic nature of the benzoxazine monomer synthesis that the mechanical stability could be addressed chemically, avoiding the complications of using rubber toughening agents or plasticizers. The monomer synthesis offers tailorability of both the phenol and amine to incorporate almost any functionality into a polybenzoxazine through either commercial or synthetic sources. In this dissertation, the modification of benzoxazine monomers using various starting materials in an effort to improve the physical properties and incorporate unique functionality into benzoxazine networks is described. In the first study, flexible benzoxazine networks were designed by first incorporating long aliphatic linkers between a diphenol to which a bisbenzoxazine monomer can be synthesized via the Mannich condensation reaction. The intent of this project is to incorporate flexibility directly into the monomer, and thus the network, creating a less brittle material without the need for additives. The second project focuses on simplifying the tailorability of these materials by utilizing copolymers of compatible bisbenzoxazine monomers. Ultimately, copolymers of compatible monomers allow improved versatility for tailoring network properties (i.e., thermomechanical) without extensive monomer synthesis. The third and final project highlights the chemical versatility of polybenzoxazines by designing flexible networks containing quaternizable amines. Following the polymerization, modification of the network through simple alkylation chemistry affords a polyelectrolyte network capable of conducting ions. The projects mentioned above center around the versatility in both the monomer and polymer synthesis and show the potential for utilization in a variety of areas.