Thermal lensing in poly(vinyl alcohol)/polyaniline blends

Abstract

AbstractNonlinear optical properties of poly(vinyl alcohol) (PVA)/polyaniline (PAni) blends were measured with the single‐beam Z‐scan technique with Fourier analysis. The results obtained with continuous wave (cw) excitation indicated that the self‐phase modulation had a thermal origin. Besides the Z‐scan technique, we also employed the time‐resolved mode‐mismatched thermal lens (TL) technique to obtain the temperature coefficient of the optical path length, ds/dT, and the thermal diffusivity coefficient, D, for the specific concentrations used in our blends. ds/dT varied between −0.8 and −1.0 × 10−4 K−1, whereas the thermal diffusivity varied between 1.0 and 1.3 × 10−3 cm2/s. The TL technique was further used to study the aging of the blends as they were heated to 90 °C. Unlike the electrical conductivity of PAni films, which presented a strong dependence on the doping level, the thermooptic properties presented only a slight variation with doping. This feature indicated that the PVA/glutaraldehyde network made the main contribution to the thermooptic properties (D and ds/dT) in the PAni blends. Similarly, dimethyl sulfoxide as a solvent determined the thermooptic properties of PAni solutions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1949–1956, 2002