Volatile Organic Compound Sensing and Other Remarkable Properties of Carbodiimide Polymers and Polymerizations

Abstract

Polycarbodiimides are a developing class of helical polymers formed via synthesis, which utilize transition-metal facilitated polymerizations and contain the ability to incorporate a wide range of pendant groups onto the amidinate backbone, allowing for numerous applications. These highly regioregular polymers, confirmed by 15N NMR spectroscopic analysis, shows potential in practical applications concerning volatile organic compound sensing using poly(N-1-naphthyl-Noctadecylcarbodiimde) (PolyNOC), due to the chiroptical switching nature of the polymer in the presence of temperature and solvent variation. This phenomenon is confirmed by studies conducted utilizing a real-time ATR-FTIR probe monitoring the rapid polymer response to various solvent and solvent mixtures, such as hydrogenated pyrolysis gas. PolyNOC’s varying responses to similar solvents were quantified and clarified using Hansen Solubility Parameters, assigning polycarbodiimides favorability to solvents with reduced standard deviations in polarity (δp), dispersion forces (δd), and hydrogen bonding forces (δh). Due to polyNOC’s and polyPOC’s (poly[N-1-phenyl-N-octadecylcarbodiimde]) helical nature and excellent solubility in various solvents, lyotropic liquid crystal behavior was observed with possible exhibition of Blue Phase III. Previously documented articles discuss the living nature of carbodiimide polymerizations mediated through titanium (IV) initiators, but were only verified for the Ti(IV) catalysts containing one alkoxide ligand. First-order kinetic experiments confirmed that chiral Ti(IV)-BINOL catalysts, that contain two potential activation sites, do not polymerize carbodiimides in a living fashion due to chain transfer existing in the system. Finally, potential chiral sensing properties to create a standard to determine enantiomeric excess across various functional groups were explored using carbodiimide copolymers with boronic ester functionality to reversibly bind chiral diols. The initial experiments indicated promise in imparting a helicity onto the achiral copolymer backbone using the chiral diol.