Abstract
Abstract We present a study of the photoinduced birefringence in nanocomposite films of the azopolymer PAZO (poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfon amido]-1,2-ethanediyl, sodium salt]) doped with TiO2 nanoparticles (NP) with different concentrations before and after thermal annealing. The NP represent nanopowder with primary particle size 21 nm. The concentration of the NP was varied from 0% (non-doped azopolymer film) to 5 wt%. The thermal process, applied to the nanocomposite films, includes 1 h heating at 200°C. Previous studies of PAZO show that the polymer is stable up to 270°C. We study the dependence of the maximal birefringence induced with He-Cd laser (λ= 442 nm) on the concentration of the TiO2 NP in the azopolymer thin films as well as thermal effect on the absorbance spectra of the thin films. As indicated by our results, the birefringence is higher for the thermally annealed samples. An increase of the photoinduced birefringence is also observed for the nanocomposite layers with 1% NP for the non-annealed films, and with 2% NP for the annealed films.
Highlights
We present a study of the photoinduced birefringence in nanocomposite lms of the azopolymer PAZO (poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfon amido]-1,2-ethanediyl, sodium salt]) doped with TiO2 nanoparticles (NP) with di erent concentrations before and a er thermal annealing
We study the dependence of the maximal birefringence induced with He-Cd laser (λ = 442 nm) on the concentration of the TiO2 NP in the azopolymer thin lms as well as thermal e ect on the absorbance spectra of the thin lms
An increase of the photoinduced birefringence is observed for the nanocomposite layers with 1% NP for the non-annealed lms, and with 2% NP for the annealed lms
Summary
Abstract: We present a study of the photoinduced birefringence in nanocomposite lms of the azopolymer PAZO (poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfon amido]-1,2-ethanediyl, sodium salt]) doped with TiO2 nanoparticles (NP) with di erent concentrations before and a er thermal annealing. There is no yet established model to explain this e ect, a possible mechanism is suggested It assumes that the light scattered from the NP is able to address the “o -plane” azochromophores, to reorient them, and to contribute to the birefringence increase [10]. The scattering of light by small particles has been discussed in [13, 14] This encourages us to continue with investigations of similar nanocomposites. The present results are compared with similar azopolymer-based nanocomposites in our previous work [10, 12]
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