Polarization holography reveals the nature of the grating in polymers containing azo-dye

in Optics Communications (2000), 185(1-3), 1-12

To study the origin of reversible holographic recording in three polymers containing the same azo-dye, we have measured the diffraction efficiency and analyzed the gratings characteristics for various ... [more ▼]

To study the origin of reversible holographic recording in three polymers containing the same azo-dye, we have measured the diffraction efficiency and analyzed the gratings characteristics for various writing beams polarizations. The amplitude of the holographic grating, as well as the ratio between index and absorption modulations, have been investigated by gratings shifting. The total amount of diffracted power and the diffraction efficiency versus the reading beam polarization has been measured by non-degenerated four waves mixing. These experiments have revealed that the molecular mechanisms of holographic recording in the studied compounds are different. The photoinduced orientation of the chromophores is predominant for C6-C11-DMNPAA; so, in C11-C6-DMNPAA (DMNPAA: 2,5-dimethyl-4-(p-nitrophenylazo)anisole), the refractive index variation comes from the presence of both trans and cis populations generated by photoisomerization. The behavior of the PVK:DMNPAA is included between these extreme cases since both phenomena act. [less ▲]

Synthesis and polarized light-induced birefringence of new polymethacrylates containing carbazolyl and azobenzene pendant groups

in Journal of Polymer Science. Part B, Polymer Physics (2000), 38(1), 205-213

Low Tg copolymers of [11(N-carbazolyl)undecylmethacrylate] and [2,5-dimethylphenyl-[(4-nitrophenyl)azo]-phenoxyalkylmethacrylate] have been synthesized and the polarized light-induced birefringence of ... [more ▼]

Low Tg copolymers of [11(N-carbazolyl)undecylmethacrylate] and [2,5-dimethylphenyl-[(4-nitrophenyl)azo]-phenoxyalkylmethacrylate] have been synthesized and the polarized light-induced birefringence of thick films (70 m) has been investigated at a constant deducted temperature relative to Tg (T - Tg = 10 °C). The optical properties of these copolymers have been studied in relation to the azo-dye content and the length of the alkyl spacer between the azo-dye and the methacrylic backbone. They have been compared with the dispersion of (4-methoxy-2,5-dimethylphenyl)-(4-nitrophenyl)diazene (DMNPAA) within a poly[11(N-carbazolyl)undecyl-methacrylate] and a poly[N-vinylcarbazole] (PVK) matrix. The experimental curves have been fitted by biexponentials, so emphasizing the effects of the copolymer structure on the kinetics of the writing process. The photoinduced orientation is more than three orders of magnitude higher in a grafted material compared to the dispersion version. The azo-dye concentration also has an important role in both the amplitude and the dynamics of the photo-orientation. [less ▲]

Dynamics of the photo-induced orientation and relaxation of new polymethacrylates containing carbazolyl and azobenzene pendant groups

in Polymer International (1999), 48(3), 205-211

Polarized-light-induced birefringence has been investigated in copolymers of [-(N-carbazolyl)alkyl methacrylate] and [2,5-dimethylphenyl-[(4-nitrophenyl)azo]phenoxyalkyl methacrylate]. Optical properties ... [more ▼]

Polarized-light-induced birefringence has been investigated in copolymers of [-(N-carbazolyl)alkyl methacrylate] and [2,5-dimethylphenyl-[(4-nitrophenyl)azo]phenoxyalkyl methacrylate]. Optical properties of the side-chain copolymers have been compared with materials in which the azo-dye was merely dispersed in a poly[-(N-carbazolyl)alkyl methacrylate] matrix. Increasing the temperature of the film has a dramatic depressive effect on the maximum of photo-induced orientation near and above the glass transition temperature (Tg) region, while its effect was restricted under this temperature. Kinetics of the photo-orientation and the thermal relaxation as a function of temperature have been analysed by a biexponential model based on two rate constants. The universal Williams-Landel-Ferry (WLF) theory has been used to correlate the writing process and relaxation relative time constants with the relative temperature, i.e. T-Tg . The validity of this model for the studied materials leads to the assumption that photo-orientation and relaxation processes are mainly dependent on the free volume in the polymer matrix. This hypothesis has been assessed in the case of [11-(N-carbazolyl)undecyl methacrylate]-based materials. [less ▲]

Synthesis and electrooptic properties of a new chromophore dispersed or grafted in a carbazolyl methacrylate matrix

in Chemistry of Materials (1998), 10

A copolymer of [11-(N-carbazolyl)undecyl methacrylate] and ethyl (E)-2-cyano-3[5-(5-(4-methacryloyloxy)piperidino-2-thienylcarbonyl)-2-thienyl]-2-propenoate has been prepared. The photoconductivity and ... [more ▼]

A copolymer of [11-(N-carbazolyl)undecyl methacrylate] and ethyl (E)-2-cyano-3[5-(5-(4-methacryloyloxy)piperidino-2-thienylcarbonyl)-2-thienyl]-2-propenoate has been prepared. The photoconductivity and the electrooptic properties of a hot-pressed thin film of this copolymer have been measured and compared with the properties of the dispersion of ethyl (E)-2-cyano-3[5-(5-piperidino-2-thienylcarbonyl)-2-thienyl]-2-propenoate within a poly[11-(N-carbazolyl)undecyl methacrylate] matrix. The electrooptic coefficient has been measured by both interferometric and polarimetric techniques. The interferometric technique was not appropriated because the strong electric field applied to the electrodes changes the film thickness of these low Tg materials. A value of up to 5 pm/V for the figure of merit n3(r13 − r33) has been reported for the dispersed material, which is 10 times higher than the corresponding grafted material, and a linear relationship between the poling intensity and the electrooptic coefficient has been observed for the two materials. [less ▲]

Electrochemical synthesis of new electroactive polymers from dithienylene-vinylene derivatives

in Synthetic Metals (1997, January), 84(1-3), 163-164

Highly conjugated thiophene derivatives, based on thienylene-vinylene and thieneylene-vinylene-phenylene units, have been synthesized in order to examine: (i) the effect of such regular conjugated monomer ... [more ▼]

Highly conjugated thiophene derivatives, based on thienylene-vinylene and thieneylene-vinylene-phenylene units, have been synthesized in order to examine: (i) the effect of such regular conjugated monomer structures on the polymerization; (ii) the optical and electrochemical properties of the corresponding conjugated polymers. The all-trans monomers have been prepared by a Wittig reaction and the polymers have then been synthesized electrochemically. The polymers are electrochromic and can be reversibly doped both oxidatively and reductively. Their electrochemical behavior and optical properties have been analysed on the basis of quantum-chemical calculations. [less ▲]