Brian Carrick

Poly(benzyl methacrylate) exhibits lower critical solution temperature phase behavior in ionic liquids due to unique solvent-solute interactions stabilizing the polymer in solution at room temperature and drive the solution to phase separate at higher temperatures. This behavior is unable to be predicted by the classical Flory-Huggins polymer solution theory and much uncertainty remains surrounding these systems. In this work, we describe the rheological behavior of poly(benzyl methacrylate) in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide for solvent-rich solutions. Upon heating, a four-order-of-magnitude increase in both the storage and loss moduli is registered near the optical phase separation temperatures. The increase in modulus can be halted by annealing a sample during phase separation, yet it exhibits a high level of reversibility. This is indicative of gelation, as the response is larger than if the polymer chains were chemically cross-linked, a behavior that is not typically observed within homopolymer solutions. The rheological gel temperatures follows a similar trend to previous cloud point measurements, demonstrating the critical composition of this system lies away from the theoretical 5 – 7 wt% as predicted by Flory-Huggins solution theory.