Crystalline Conjugated Block Copolymer Self-Assembly

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TECHNICAL SUMMARYRod-coil block copolymers play a central role in many recent efforts to optimize organic optoelectronic devices, but it is clear that structure must be controlled on multiple length scales ranging from the atomic spacing in a crystalline lattice to the 10 nm length scale of block copolymer self-assembly and the 100 nm to micron scale of the device. Critical to these efforts is an understanding of how these interactions occurring over drastically different length scales work in combination. The goals of this project involve the synthesis and self assembly of conjugated block copolymers, gaining a fundamental understanding of phase separation in these rod-coil block copolymers, and understanding the interplay of structural effects on charge mobility. In the longer term, this fundamental understanding will be used to guide the design of semiflexible block copolymers and ultimately impact fields such as organic optoelectronics and biomaterials.The interplay between backbone shape, block copolymer self-assembly, crystallinity, and semiconducting properties is crucial both for a fundamental understanding of structure-property relationships as well as for the future design of optimized materials with controllable properties. Here, synthetic design and self-assembly of conjugated rod-coil block copolymers will be utilized to: (a) Develop a detailed understanding of the relationship between chain shape, crystallinity, and charge mobility in conjugated polymers (particularly polythiophene derivatives); (b) Understand the rules associated with achieving confined crystallization in conjugated rod-coil block copolymers and the detailed morphology of crystals within these nanodomains, and (c) Probe the roles of semi-flexible rods and the balance between liquid-crystalline and block-copolymer interactions on conjugated block copolymer self-assembly.NON-TECHNICAL SUMMARYCritical to efforts for optimizing organic optoelectronic devices, biological membranes, and drug delivery applications is an understanding of the thermodynamics that control nanometer-scale self-assembly in specially designed polymeric materials. This is an integrated research program aimed at understanding the thermodynamics of self-assembly of block copolymers where molecular rigidity and semi-crystallinity affect the polymer nanostructure and charge transport properties. An important component of this project involves several integrated educational activities. Undergraduate and graduate students will all be trained on a number of national user facilities, participate in local and national meetings, and interact closely with collaborators in the process of performing this research. Additionally, a partnership is underway with a teacher at Creekside Middle School in Castro Valley to offer an exploratory module on polymer science related to this research.