CAREER: Dissipative Non-Equilibrium Supramolecular Hydrogels Using Fuels

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Nontechnical SummaryMaterials found throughout nature, including those which compose the cells and tissues of the body, have structures that often exist transiently and are dependent on the presence of certain stimuli. Recreating the transient, stimuli-dependent states of natural materials with synthetic constructs thus offers an approach to more precisely engineer replicates of natural materials in pursuit of more life-like materials. This CAREER award seeks to establish new routes to the creation of transient materials which will inform the future design of functional constructs and therapeutic devices. Specifically, materials for which formation and stability is dictated by the presence of a continuously consumed fuel source are envisioned, wherein the lifetime of the material is tunable through altering the dosage of applied fuel or changing the environmental conditions to which the material is exposed. Similarly, toward harnessing light as a fuel, other materials are envisioned which convert applied light into a directive cue driving transient material formation with tunable lifetime. Accessing transient states in soft materials, by way of chemical fuels or by using light, points to a new direction in the design of soft materials with enhanced functionality rooted in their nature-mimetic transient states, with uses in advancing a number of material applications. Integrated within this convergent research program is an ongoing effort to build and expand laboratory and classroom training in the area of molecular engineering, and an overarching goal to advance the practice of scientific communication through research, mentorship, community outreach, and experiential training for graduate trainees in the chemical and materials sciences.Technical SummaryNature achieves remarkable function from materials which exist in dissipative non-equilibrium states; one must look no further than the cell structure and motility which arises from ATP-fueled non-equilibrium assembly of its actin cytoskeleton. Accordingly, this CAREER award integrates research and training in an effort to create bio-inspired materials with fuel-dependent formation and transient stability, and which subsequently dissipate when fuel is limited. Recreating the dissipative non-equilibrium states of natural materials with synthetic analogues has captivated many in recent years. While efforts have focused almost exclusively on fuel-dependent assembly of small molecules, a new paradigm is described here for fuel-dependent non-equilibrium formation of host–guest supramolecular hydrogels. This outcome will be achieved through recognition motifs which are dependent on a continuous supply of a consumable chemical fuel source, or by using light-responsive motifs to actuate a light stimulus into altered affinity and/or dynamics of the motif. When the specific chemical or light fuel sources are limited, these materials will exist transiently and dissipate to their designed equilibrium state of a sol or weak gel. More broadly, host–guest supramolecular recognition affords a useful class of soft materials which have properties directly attributed to the dynamic nature of their crosslinking interactions. These materials have thus exhibited a variety of useful emergent properties in their application as new biomaterials and therapeutic delivery devices, and also afford features desirable for a number of industrial applications. The ability to further integrate transient and fuel-dependent formation of this class of materials seeks increased biomimetic function to further expand on their possible uses. This research plan is placed within a multidisciplinary training environment tailored to train leaders in the convergent discipline of molecular engineering, which is further augmented by classroom instruction. In addition, training aimed at improving scientific communication in the chemical and materials sciences seeks to achieve improved public engagement conveying the importance of scientific research.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.