Collaborative Proposal: How to Gel Oil (or Water) in an Immiscible Oil-Water Mixture: A Systematic Study of Phase-Selective Gelation

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Everyone knows that oil and water do not mix. This award will study how one of these liquids can be selectively converted into a gel – a process that is termed phase-selective gelation. To induce such gelation, molecules will be synthesized that will find their way into either the oil or the water layer and then undergo ‘self-assembly’ there. Self-assembly implies that the molecules will spontaneously join and form structures – in this case, long fibers – with nanoscale sizes. In turn, the nanofibers will entangle with each other and thus convert the liquid into a paste-like material (with the consistency of ketchup or hair gel). This will be the first systematic study on phase-selective gelation. The insights from this award could help design new materials to clean-up oil spills or to remediate oil-contaminated ground water. The focus of this award will be on the fundamental science behind the phenomenon of phase-selective gelation, and the goal will be to develop design rules connecting molecular structure, interfacial properties, and gel structure/rheology. A range of amphiphilic molecules will be synthesized and their ability to gel either the oil or water phase in a mixture will be studied. Key criteria for a molecule to be a phase-selective gelator are: (a) it should not emulsify the oil-water mixture; and (b) it should also not get appreciably solubilized in either of the phases. The hypothesis is that such gelation can be accomplished by striking the right balance of non-covalent interactions between the amphiphilic molecules such as hydrogen-bonding between the head groups as well as pi-pi and van der Waals interactions between the tails. The proposed research will also be integrated with educational, mentoring, and outreach activities at the collaborating institutions.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.