摘要
Sum-frequency vibrational spectroscopy (SFVS) has been used to probe the chirality of a polymer thin film. The polymer used has a π-electron conjugated structure in the main chain, and a chiral center in the side chains that is close to the main chain, giving rise to the helically twisted main chain. The vibrational modes probed are stretches associated with the main chain. As expected for chiral responses, we find that the chiral SFVS spectra are identical for the two enantiomers, and the signal vanishes for the racemic polymer. We also confirm experimentally that the chiral nonlinear susceptibilities for SFVS for the two enantiomers have opposite signs.