New Photonic Materials from Comb Block Copolymers assembled in the Solid State

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TECHNICAL SUMMARY: This proposal describes research on the assembly of comb block copolymers into ordered arrays in the solid state to form new photonic materials. Comb block copolymers have a polymeric backbone and regularly and densely spaced polymeric arms and, because of this geometry, these polymers have ultrahigh molecular weights that are typically above one million grams per mole and may exceed fifty million grams per mole. Despite their sizes, these polymers assemble into ordered morphologies in the solid state with domain sizes (the size of the repeat unit) in excess of one hundred nanometers and, for some comb block copolymers, up to 250 nm. This work is highly original for several reasons. First, these polymers are a relatively new polymeric architecture that have molecular weights and geometries that are challenging to impossible to synthesize for linear block copolymers. Second, these polymers assemble in the solid state into ordered morphologies despite predictions based on their ultrahigh molecular weights. The common belief in this field is that polymers with ultrahigh molecular weights will not assemble, but this belief is based on assumptions for linear block copolymers. These assumptions do not hold for comb block copolymers due to their unique geometries, so they change the limits of what polymers can be assembled and, importantly, open new opportunities to assemble ultrahigh molecular weight copolymers. Third, these polymers form new photonic materials after their assembly in the solid state. This result is critically important because of the potential importance of polymers in high-end optical applications. Comb block copolymers are assembled without additives, their assembly may be more ordered than typical linear block copolymers assembled with additives that often phase segregate and form defects. In this proposal, the assembly of comb block copolymers into ordered arrays and their optical properties will be investigated. This work has both fundamental applications the assembly of a new architecture of block polymer and practical applications access to new photonic materials. NON-TECHNICAL SUMMARY: This proposal describes new polymers that spontaneously assemble into new, potentially very important, optical materials. The combination of polymers and optics is an exciting frontier with many potential high-end applications in the next generation of computers that use light rather than electrons, current and future sensors that are easily integrated into portable units, materials to speed the transfer of information using light, and many more areas of science and technology. This work describes the use of a powerful concept (self-assembly) to create ordered arrays of polymers that interact with light in predictable and, occasionally, new ways. In immediate applications, these polymers will allow precise atomic tuning to sense the presence of metals and, possibly, toxins in real time. This work is possible because these polymers can be controlled on a molecular level to integrate molecules that will change the optical properties of the polymers in response to a stress or stimuli. In addition, this proposal will make an immediate impact in the education of undergraduates including many women and minorities. A new class will be started at the University of Iowa that will encourage freshman and sophomores to become involved in research that will broaden their horizons and further their education.