Polymers exhibit stimuli responsive solubility that depends on the polymer microstructure, the solvent, and a chemical or physical stimulus. For example, poly(<i>N</i>-isopropylacrylamide) (PNIPAM) is a common thermoresponsive polymers whose lower critical solution temperature derives from a favorable ΔH due to hydrogen bonding with water and an unfavorable ΔS due to the organization of solvents on the polymer. This work describes how H-bond solubilization can be used to generate chemically-reversible responsive solubility of a polar polymer like PNIPAM in nonpolar alkane solvents. The acid-assisted solubilization of PNIPAM was explored using carboxylic acids like acetic, valeric, octanoic and oleic acids. The results showed that the longer aliphatic acids are more effective on a mole:mole bases at effecting PNIPAM solubilization in hexane. In both cases, the PNIPAM that dissolves in the nonpolar solvents like hexane and toluene can be recovered by addition of base and hydrogen competitor, DMF. Using dansyl-labelled PNIPAM with octanoic acid as a solubilization agent with NEt<sub>3</sub> as the chemical agent for PNIPAM precipitation, we have shown that the process of solubilization/precipitation can be repeated through at least three cycles. PNIPAM-bound rhodium catalyst successfully catalyzed the hydrogenation of 1-decene in toluene and recycled at least three times with high yield of decane produced. Ongoing studies are exploring this molecular recognition based solubilization with other solubilizing agents, other precipitation agents and exploring the use of this chemically responsive solubility both as a tool to prepare new solvent systems and new sorts of recyclable catalysts.

Polarizing nonpolar polymers with poly(N-isopropylacrylamide) in nonpolar alkanes

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.