The increasing precision of the primary (e.g. microstructure sequence, molecular weight dispersity, etc.) and secondary structure (helical sense, persistence length, thermal stability, etc.) of polycarbodiimides has resulted in chiroptical switching without the use of chiral monomers, solvents, or additives, and without any obvious sensing functional groups on alternating pendant groups. The initial design and chiroptical properties of poly(N-(n-octadecyl)-N’-(1-naphthyl)carbodiimide), or polyNOC, will be described along with previous studies elucidating the presence of an equilibrium of expanded (state A) and contracted (state B) conformations. Recent characterization of polyNOC surfaces and bulk phases will be presented that suggests the state A/B population is concentration independent and can be kinetically trapped in the solid-state. Once trapped in the solid state the state A/B population can be reversibly modulated with solvent exposure. VOC sensing using the state A/B population of polyNOC films will be introduced for the first time, using ATR-FTIR spectroscopy for transduction. An example of biasing the population of polyNOC in the solid state is shown in figure 1 using chloroform and dichloromethane vapor. Additional examples will be presented including non-polar hydrocarbons and common laboratory solvents. Complimentary differential scanning calorimetry and grazing incidence, X-ray diffraction studies will also be presented that further elucidate the conformation switching mechanism.

Serendipitous discovery of an unlikely polycarbodiimide switch and recent application to VOC sensing

251st National Meeting (2016)

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