Novel Hydrogen-Bonding Pattern of Water in Polycarbonate

We study the hydrogen-bonding structure of the water in polycarbonate (PC) (OC6H4C(CH3)2C6H4OCO)n by near- and mid-infrared spectroscopy. We extensively analyze the effects of the hydration interaction on the near- and mid-infrared absorptions of the hydrating water and on those of the phenyl and carbonyl groups, either of which should interact with the water in PC. The analysis has consistently led us to the conclusion that the water is hydrogen bonded to the phenyl group but not to the carbonate C=O, against the prediction that the hydrogen-bonding energy of the water to the former should be significantly smaller than that to the latter (P. R. Rablen et al., J. Phys. Chem. A1998, 102, 3782). To explain the unexpected hydration, we propose a novel hydration pattern, in which the water is fittingly settled into the “phenyl hollow” formed by the two adjacent phenyl groups, obliquely connected by -C(CH3)2- in-between. The key factor of the hydration pattern or that the water symmetrically acts as proton donor to the π clouds of the phenyl groups has been proved to be perfectly consistent with the observed spectral features of the hydrating water.