Sum-frequency vibrational spectroscopy of a helically structured conjugated polymer

The use of a novel technique, sum frequency vibrational frequency, to probe the molecular chirality of thin polymer films was discussed. It was found that the chiral vibrational spectra of poly(bithienylene-phenylene) (PBTP) were obtained and the two enantiomers were distinguished by an interference method between their chiral and achiral responses. It was observed that the sensitivity of the technique could be enhanced by vibration-electronic double resonance. The results show that the vibration-electronic double resonance was responsible for the observation of unusually strong chiral spectra of the phenylene vibration modes.