Abstract-The sum-frequency spectroscopy signatures of NH-(amide A) and C = O (amide I) groups, the amide segments in all proteins, are measured in thin films that consist of an ensemble of right-handed, helical poly--benzyl-L-glutamate (PBLG) macromolecules that are endgrafted and self-organized into a monomolecular film with a large degree of unidirectional order. Distinct sum-frequency spectral signatures associated with the amide A and the amide I bands are observed because of a strong noncentro-symmetry produced by intra-and intermolecular forces. Hydrogen bonding self-organizes amino and acidic groups within the molecular helical scaffold. In an endgrafted thin film, repulsive electrostatic forces between PBLG macromolecules stabilize the organization between molecules. The average orientation of the PBLG chain was measured. Imaging scans using sum-frequency generation, complemented by atomic force microscopy, were used to investigate the uniformity of orientation of the PBLG chains.

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The first series of conjugated organic polymers with the formula {1,4-[2-(RO)-5-(R′O)C 6 H 2 ]sNdNsC 6 H 4 s CtC-} n , where R ) methyl, R′ ) hexyl (7a) and R ) hexyl, R′ ) SiMe 2 -t-Bu (8), were produced in palladium-catalyzed cross-coupling and homocoupling reactions of selected bis(bromo) and bis(alkynyl) azo monomers. The molecular weights (M n ) for the conjugated polymers ranged from 5500 to 22 000. Degenerate four wave mixing (DFWM) with 780 nm femtosecond pulses was used to investigate electronic third-order nonlinearities for azo monomer 3a and conjugated azo polymer 7a. Both compounds had ultrafast nonlinearities with τ 1 ) 100 fs response time. The real part of 7a second hyperpolarizability, γ 7a , is negative, Re γ 7a ) -( 4.3 ( 0.3) × 10 -46 m 5 V -2 . Polymer 7a's second hyperpolarizability also has an imaginary component, Im γ 7a ) (1.7 ( 0.3) × 10 -46 m 5 V -2 . Calculated per repeat unit, polymer |γ 7a | ) (4.6 ( 0.5) × 10 -46 m 5 V -2 and is about 780 times larger than that for monomer 3a. γ 7a was analyzed with the three-level model; γ 7a enhancement is attributed to the conjugation effects in the polymer and contributions from a two-photon state. Polymer 7a's excited state had a 3.4 ps lifetime, as determined by DFWM.

The mechanism of the charge carrier photogeneration in Y-form titanyl phthalocyanine was investigated by means of fluorescence and photocurrent measurements. Sample excitation by two time-separated light pulses was applied to obtain information on the time course of the fluorescence and generation processes. Charge carrier precursors—charge pairs—were found to be generated only during the short time interval after the exciton was created. This interval is much shorter than the fluorescence state lifetime.