Design, Synthesis, and Evaluation of Next Generation Technologies in Stimulus-Responsive Materials and Organic Electronics
- Author(s): Unruh, Jr, David Allen
- Advisor(s): Frechet, Jean M. J.
- et al.
Future advancements in technology are fundamentally limited by materials research and development. New materials are most often found by exploring new chemistries, but the nature of these chemistries can vary widely. This dissertation is a compilation of some of the chemical insights that can lead to the development of new stimulus-responsive materials and organic electronics.
For example, a tool that can consistently display specific, precise types of reactivity can have dramatic effects on the ability to make never-before seen materials. Chapter 1 discusses a multifunctional mixed monolayer resist for scanning probe nanolithography that can respond to two different electrochemical stimuli to produce two chemically different products, each with nanoscale resolution. The synthesis of a novel reductively active monolayer precursor, the preparation of this mixed monolayer surface, and its use in a proof-of-principle bottom-up assembly of complementary semiconductor components are described.
A combination of older chemistries can result in the development of new materials as well. In Chapter 2, the synthesis of a thermally-triggered single component epoxy monomer is described. A small library of these monomers is prepared, and structure-property relationships are established between monomer molecular structure and cure temperature, enthalpy of cure, and glass transition temperature. In addition, effects of cure on the production of voids in the fully cured thermosetting polymer are investigated.
New materials can also be made by altering the way other materials pack together, as commonly found in supramolecular chemistry. Chapter 3 discusses the pre-organization of small molecules into nanoscale crystalline domains as a means to establishing long range order in organic electronics. A small molecule previously used in bulk heterojunciton organic photovoltaics is shown to make high aspect ratio nanowires through solution-phase nanocrystal synthesis, and the degree of crystallinity and device performance in organic field effect transistors are compared to the same molecule cast as a thin film. In addition, different derivatives of the same molecule are evaluated for their ability to pack differently in the solid state.
Finally, new materials can be inspired by the limitations of existing materials and the challenges of an emerging technology. Chapter 4 introduces a new thienooxypyrroline acceptor building block for donor-acceptor materials in organic photovoltaics and organic field effect transistors. The synthetic sequence to access this chromophore is described, and a small library of thienooxypyrroline monomers are prepared. Small molecules and polymers using these monomers are synthesized and shown to have promising device performance characteristics in preliminary testing of both OPVs and OFETs. Based upon the device data, possible next steps are presented for use of this building block in future materials for organic electronics.