Responsive and Healable Materials Constructed via Dynamic-Covalent Bonds

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NON-TECHNICAL SUMMARY: This project will test the hypothesis that dynamic interactions can be used to prepare materials that reversibly assemble and disassemble in solution or in the bulk state. Two specific classes of materials will be considered. The first system will involve nanosized polymeric assemblies that can be triggered to disassemble when high concentrations of sugar are in the surrounding solution. Provided these assemblies can be loaded with molecular cargo, such materials may prove useful for the sugar-induced release of insulin or other therapeutics. The second system to be investigated will consist of bulk plastic or elastomer-like materials capable of healing after being torn, scratched, or broken. Materials that self-heal may find utility in a variety of applications, including being used in medical devices, coatings, and elastomers. Both classes of materials to be studied will derive their adaptability and healability from the design and architectural structure introduced by the synthetic approach in this project. In addition to the development of new materials, studying their underlying chemical and physical properties, and considering the potential utility of these materials, this research will help to educate and train scientists at many levels in a field that is inherently multidisciplinary. TECHNICAL SUMMARY: This research plan is designed to exploit boronic/boronate ester reversibility within the field of responsive polymeric materials. The main hypothesis of the proposed research is that the dynamic-covalent nature of boronic/boronate ester crosslinks can be utilized to achieve stimuli-responsive and self-healing behaviors in two classes of materials. The first class of materials is composed of polymeric vesicles crosslinked via boronic esters. Block copolymers with one hydrophilic block and one boronic acid-containing block will be self-assembled and crosslinked with a multifunctional diol that can be induced to dissociate under high concentrations of sugars and other small molecule diols. The second class of materials to be investigated consists of bulk polymeric materials crosslinked via boronic esters. Upon material failure, healing can be induced by boronic ester exchange at the damage interface. While this phenomenon has been employed for small molecule organic synthesis, molecular recognition, and saccharide sensing, its incorporation in the fields of materials design and controlled polymer synthesis has been significantly limited. Materials that autonomously self-heal may find utility in a variety of applications, including being used in medical devices, coatings, and elastomers. Graduate students involved in this project will gain valuable insight into the emerging fields of reversible-covalent and self-healing materials. Outreach efforts will be a key component of this project and will involve exposure of area high school and community college students to research in these areas.