Hydrogels are soft materials that are largely comprised of water, and as such, have found extensive utility in hygiene, contact lens, medical implants, and wound care products (a 27 billion dollar industry by 2022). Despite the importance of this class of materials, molecular-level strategies to design new hydrogels are not well understood. The objective of this work is to develop a set of molecular design principles that can govern and control the physical properties of hydrogels. Triblock copolymers with geometrically defined end-groups will be synthesized. These polymers are expected to spontaneously self-assemble in water to afford hydrogel compositions. The nano- and micro-structure of the hydrogels will be characterized and correlated to the physical properties of the hydrogels. This interdisciplinary research program lies at the interface between the fields of polymer science and supramolecular chemistry, and aims to train the next generation of scientists in these fields. The broader impacts of this proposal include stimulating pre-college and college students to become interested in polymer science, and increasing the diversity of scientists, particularly from societally and economically disadvantaged backgrounds. The Principal Investigator will emphasize teacher training to maximize the effectiveness of the broader impacts of this project. The program outlined includes the creation of educational modules that introduce polymer science to students in K-12, undergraduate, and graduate stages of their learning careers, as well as the engagement of disadvantaged and under-represented groups in STEM.
Wholly synthetic sequence-specific polymers are challenging to synthesize, and the design rules that govern the self-assembly of these polymers is incredibly complex. Accordingly, there is a need to develop a strategy to afford hierarchically self-assembled synthetic polymers that does not rely on precise monomer sequences. The primary objective of this work is to develop a platform that supramolecularly engineers block copolymers by introducing supramolecular functionalities at precise locations of a polymer chain--such as at the polymer termini or at the interface between polymer blocks--in order to control the assembly of these macromolecules into larger, well-defined ensembles in aqueous media. The central hypothesis is that geometrically defined hydrogen bonding systems can self-assemble into linear arrays or rosettes within the hydrophobic domain of a hydrogel-forming triblock copolymer, as long as the glass transition temperature of the respective block is far below room temperature. Triblock copolymers with the composition, poly(alkylglycidyl ether)-b-poly(ethylene glycol)-b-poly(alkylglycidyl ether), will be synthesized and functionalized at the chain ends with array-forming hydrogen bonding motifs such as ureas. These triblock copolymers will hierarchically self-assemble in aqueous solution to afford hydrogels. The viscoelastic properties of these materials will be characterized by rheometry and the nano- and microstructure of the hydrogels will be determined by small and wide-angle x-ray scattering. This fundamental study will afford new hierarchically assembling hydrogels for use in bioprinting for tissue engineering and drug delivery, wherein the physical properties of the hydrogel can ultimately be controlled at the molecular level.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
