Chiral Azo polyurethane(urea): Preparation,optical properties and low power consumption polymeric thermo‐optic switch

Azo chromophore molecule (NPMBR) was synthesized by using 4‐nitroaniline, sodium nitrite and chiral reagent, R‐α‐methyl benzylamine. Then, NPMBR was polymerized with isophorone diisocyanate and polyether polyol to obtain novel chiral azo polyurethane(urea) (PUUR). The chemical structures of NPMBR and PUUR were characterized by FTIR and UV‐Vis spectroscopy. The UV‐induced trans/cis photoisomerization and reflex‐isomerization behaviors were investigated and the results indicated that the PUUR solution could undergo photochromism after irradiated by UV light. The measurements of refractive index and thermo‐optic coefficient (dn/dT) of PUUR were demonstrated at different wavelengths and different temperatures by ATR technique. By using CCD digital imaging devices, transmission loss of the internal waveguide was measured. The refractive index dispersions and Sellmeyer coefficients of PUUR were obtained by Sellmeyer equation. A Y‐branched switch based on thermo‐optic effect was proposed and the performance of switch was simulated. With branching angle of 0.143° and FD‐BPM method, the result showed that the power consumption of the thermo‐optic switch could be only 0.4 mW, and the response time of the switch could reach about 3 ms. It has a significant improvement in reducing the power consumption and response time compared with those of the normal Y‐branched polymer thermo‐optic switch. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

偶氮聚电解质的合成及其pH敏感行为和热光性能研究

利用偶氮聚电解质上的羧基和偶氮生色基团的特性,研究了侧链偶氮聚电解质的pH值敏感性和热光性能.采用重氮-偶合反应方法合成了偶氮苯生色分子4-(4′-硝基苯基偶氮)苯酚,将生色分子、环氧氯丙烷和α-甲基丙烯酸通过自由基聚合法,合成了侧链偶氮聚电解质.利用傅里叶红外光谱(FTIR)、紫外-可见光谱(UV-V is)和核磁共振(1H-NMR)等分析手段对所合成的侧链偶氮聚电解质进行了结构表征.采用差示扫描量热分析仪(DSC)对偶氮聚电解质进行了热稳定性表征,其玻璃化转变温度(Tg)为189.8℃,表明具有较高的热稳定性.研究了不同pH值的偶氮聚电解质溶液的紫外-可见光谱,结果表明,偶氮聚电解质对pH值具有高度敏感性.采用衰减全反射(ATR)原理测量聚合物波导薄膜在650 nm和TM偏振下的折射率和热光系数dn/dT,其值为-1.92479×10-4℃-1,是无机材料如硅酸锌玻璃(5.5×10-6℃-1)和硼硅酸盐玻璃(4.1×10-6℃-1)的10倍以上,较有机材料聚苯乙烯(-1.23×10-4℃-1)和PMMA(-1.20×10-4℃-1)大.     

Thermo-optic characteristics in transparent glass fabric reinforced composite using inorganic–organic hybrid materials

The thermo-optic characteristics of the transparent glass fabric composite and matrix resin have been investigated. The inorganic–organic hybrid materials modified with sulfur are synthesized as transparent matrix resin with the same refractive index and Abbe number as glass. The optical characteristics of the transparent composite relate to temperature due to the fact that the thermo-optic coefficient (dn/dT) for glass fiber (1.00 × 10⁻⁵K⁻¹) is different to that of inorganic–organic hybrid materials (−1.99 × 10⁻⁴K⁻¹). As the temperature increases, the transparent composite gradually becomes opaque and hazy due to the increased difference in the refractive index between the glass fiber and the matrix. The change in optical characteristics is reversible, meaning that the transparent composites can be used in for various applications in optical devices.     

Design and fabrication of single mode rib waveguides using sol–gel derived organic–inorganic hybrid materials

Multi-layer buried rib waveguides were fabricated using sol–gel derived photopatternable organic–inorganic hybrid materials through multi-step spin coating and photolithography. A single mode circular waveguide at 1,550 nm was designed and fabricated using the equivalent refractive index method. Propagation loss in the order of 1.0 dB/cm was measured by cutback method. Waveguide thermal stability and thermo-optic coefficient were investigated using thermogravimetric analysis (TGA) and spectroscopic ellipsometry, respectively. Results suggest that the single mode waveguide can be used to develop thermal optical devices such as thermo-optic switches.     

Determination of Specific Refractive Index Increment （dn/dc）_μ at a Constant Chemical Potential,for Solutions of Polymer in Mixed Solvents by the GPC Method

A new chromatographic method is described for the determination of specific refractive index increment(dn/dc)μ at a constant chemical potential,for polymer/mixed solvent systems.In this method the(dn/dc)is obtained by measuring the areas of solvated-polymer peaks when the mixed solvent is used as an eluent.Values of(dn/dc)μ for the poly(dimethylsiloxane)(PDMS)-benzene-methanol system,determined by the proposed method are in good agreement with those determined by the conventional dialysis method.The new approach has the advantages of simplicity,fast speed,and high reproducibility.The experimental results for stearic acid-chloroform-methanol system show that this method can also be applied to nonpolymer/mixed solvent systems for the determination of(dn/dc)μ.     

Order parameter studies from effective order geometry in 4O.Om and 7O.Om liquid crystalline compounds

The effective geometry parameter, α_g = n _o /n _e, is used to evaluate the orientational order parameter, S, in the case of N-(p-n-butyloxybenzylidene)-p-n-alkoxy anilines, 4O.Om and N-(p-n-heptyloxybenzylidene)-p-n-alkoxy anilines, 7O.Om compounds with m?=?3–7 and 9 in the former case and m?=?3, 5–7 and 9 in the later materials. The results obtained are compared with those calculated using the standard techniques of molecular polarisability and birefringence. The effective geometry parameter's influence on the deflection of light by the liquid crystal compounds is also studied. The variation of temperature gradient of the ordinary refractive index, dn _o /dT, and extraordinary refractive index, dn _e /dT, of the liquid crystals is also studied.     

高热稳定性氟化聚酰亚胺的合成及在热光开关中的应用

用一种新型超支化氟化聚酰亚胺(FHBPI)作为波导材料制备了聚合物热光开关. 采用DSC, TGA, 近红外吸收谱和原子力显微镜(AFM)等方法对FHBPI的热稳定性及光学特性进行了表征. 结果显示, FHBPI的玻璃化转变温度为189 ℃, 在空气中5%的热失重温度为596 ℃, 表明具有良好的热稳定性; 旋转涂膜法制备的FHBPI薄膜具有良好的成膜性; 薄膜表面粗糙度为0.54 nm; FHBPI在光通信波段有较小的吸收损耗, 适合制备低损耗的光波导器件; 用FHBPI-50为波导芯层材料, FHBPI-30为包层材料, 设计制作的热光开关响应上升时间为267.9 μs, 下降时间为254.1 μs.     

Determination of the Water/AOT/Isooctane Reverse Micelles Size Parameters from Their Refractive Index Data

The present paper aims to study the proprieties of water confined in water/AOT/isooctane reverse micelles from their refractive indices at 298.5 K. The refractive indices of the microemulsions were investigated at increasing water concentration and at different micellar volume fractions, Φ _d. The refractive index of micellar water was deduced for a large water to AOT molar ratio, W ₀. The refractive index of interfacial water was also calculated. Then, the molar faction of interfacial water, α, was deduced for different W ₀ values and compared with those measured by NMR as reported in the literature. The results show qualitative agreement. Finally, the average aggregation number, n _agg, the area per surfactant headgroup, σ, as well as the interfacial thickness, d _i, of the reverse micelles were determined for the W ₀ values studied. The values of these structural parameters also show good qualitative agreement with NMR and small angle X-ray scattering data reported in the literature. Thus, the refractive index method can be a cheap and fast alternative for these two methods.     

Refractive index modulation in polymeric photochromic films

Photochromic properties of methylacrylate monomers and polymers containing azobenzene groups with heterocyclic sulfonamide functionalities viz sulfisomidyne (4-amino-N-[2,6-dimethylpyrimidyn-4-yl]benzenesulfonamide) and sulfamethoxazole (4-amino-N-[5-methylisoxazol-3-yl]benzenesulfonamide) substituents were investigated. On illumination with light the azobenzene group underwent trans-cis isomerisation, which was manifested by a drop in the absorbance of the maximum absorption peak at ca. 450 nm and by decrease in refractive index. Quantum chemical calculations showed significant differences in UV-VIS spectra, dipole moments, polarizability and refractive index between both cis and trans form of the chromophoric monomers. The illumination of spin-coated polymer films during ellipsometry measurements resulted in a change in refractive index within the range of 0.014 to 0.025. The dynamics of growth and decay of refractive index changes, was described by biexponential functions approach.     

Use of Neural Network to Control a Refractive Index of SiN Film Deposited by Plasma Enhanced Chemical Vapor Deposition

Refractive index of silicon nitride film deposited in a plasma enhanced chemical deposition system is modeled by using neural network. The deposition process was characterized with a full factorial experiment. Additional 12 experiments were conducted to test model appropriateness. Predicted model behaviors were in good agreement with actual measurements. Deposition mechanisms were qualitatively examined especially with respect to the pressure. Possible interactions between the pressure and other factors (SiH₄, NH₃, radio frequency (RF) power, and substrate temperature) were examined on the basis of SiH/NH bond ratio. The refractive index increased with increasing either SiH₄ flow rate or RF power. In contrast, the refractive index decreased with increasing NH₃ flow rate. Little interactions between the pressure and RF power were observed. Pressure effect on the refractive index was quite different depending on the level of SiH₄ flow rate or substrate temperature. In general, increasing the pressure increased the refractive index. Meanwhile, the refractive index was insensitive to parameter variations at relatively high pressures. The most complex interaction occurred as the pressure interacted with the temperature. Useful clues to control the refractive index were revealed from the predictive model.     

Optical waveguiding and nonlinear optical characterization of 2-docosylamino-5-nitropyridine Langmuir-Blodgett films

Well ordered Y-type Langmuir-Blodgett (LB) multilayers of 2-docosylamino-5-nitropyridine (DCANP) have been characterized with linear and nonlinear optical techniques. The nonlinear optical susceptibilities have been determined for the wavelengths λ = 1064 nm (d₃₃ = (7.8±1) pm/V, d₃₁ = (2.0 ± 0.5) pm/V) and λ = 1318 nm (d₃₃ = (5.6 ± 1) pm/V). Waveguiding experiments with grating couplers allowed the excitation of TE_o and TM_o modes propagating over more than 20 mm. Guided wave attenuation coefficients as low as 12 dB/cm (at the wavelength λ = 632.8 nm) are reported. Coupling experiments allowed the determination of the dispersion of the refractive index n₃ (n₃^{632.8 nm} = 1.598). The refractive index data could be used to calculate phase-matching conditions for frequency doubling with TE modes in DCANP waveguides.     

Deposition of SiO2-Like Films by HMDSN/O2 Plasmas at Low Pressure in a MMP-DECR Reactor

The effects of process parameters such as O₂/HMDSN (hexamethyldisilazane) ratio, microwave discharge power and deposition pressure on the growth rate, chemical bonding nature, and refractive index of thin films deposited by microwave plasma from HMDSN with oxygen, have been investigated. The plasma was created in a Microwave Multipolar reactor excited by Distributed Electron Cyclotron Resonance. The films were deposited at room temperature and characterized by Fourier Transform Infrared spectroscopy and ellipsometry. Growth rate increased with the discharge power P or the deposition pressure but decreased significantly with increasing O₂/HMDSN ratio. A large change in the film composition was observed when the O₂/HMDSN ratio was varied: films deposited with only HMDSN precursor are polymer-like but as the O₂/HMDSN ratio increased, organic groups decreased. For relative pressure values over 70%, deposited films are SiO₂-like with refractive index values close to those found for thermal silicon dioxide.     

Kinetics of refractive index changes in polymeric photochromic films

Methacrylate copolymers containing, in side chain azobenzene groupings with heterocyclic sulfonamide substituents: N-(2,6-dimethylpyrimidin-4-yl)sulfamoyl (sulfisomidine) and N-(5-methylisoxazol-3-yl) sulfamoyl (sulfamethoxazole) were investigated. The materials undergo reversible trans-cis isomerisation during illumination with light. This results in changes of dipole moment, polarizability and refractive index. Ellipsometric measurements showed a distinct decreasing refractive index during illumination with light corresponding to absorption band (ca. 450 nm). Depending on the polymer, the change of real part of refractive index in spin-coated films was between 0.016 and 0.031. The dynamics of growth and decay of refractive index changes, was described by biexponential function approach.     

Optical parameters of thin calixarene films and their response to benzene,toluene and chloroform adsorption

Ellipsometry and surface plasmon-polariton resonance were used to measure both the thickness, d, and refractive index, N, of tert-butylcalix[n]arene (n = 4, 6 and 8) films, as well as the effect of the adsorption of benzene, toluene and chloroform on these parameters. The refractive index values were found to lie in the range 1.56–1.58. Exposure to benzene (chloroform) vapour increased N by 0.01–0.02, while toluene adsorption led to calixarene film swelling (up to 10–12%). Warming the films in air at 160 °C restored the former values of both d and N. Some mechanisms of interaction between the adsorbate molecules and calixarene films are proposed.     

Effects of the nanoassociation of hexadecyltrimethoxysilane precursors on the sol–gel process

Modifications to the refractive indices of meso-structured organic–inorganic films caused by variations in the mole fraction of precursors in ethanolic solutions were investigated. The refractive indices were dependent on the mole fraction of C₁₆TMS (hexadecyltrimethoxysilane) and of the C₁₆TMS/TMOS (tetramethoxysilane) (1/1) mixture in ethanol. The dependency was determined to be nonlinear, and the phenomenon was attributed to self-assembly caused by the long alkyl groups (C₁₆) on the C₁₆TMS. Changes in the maximum decreasing rate of d_n/d_x values [(d_n/d_x)_max—for d_n/d_x estimation, the curves from Fig. 1 were associated with a polynomial; using a dedicated program, d_n/d_x was calculated; maximum values of d_n/d_x were taken into account and were included in Table 1)] were used to distinguish the behavior of alcoholic precursor mixtures. In the case of using pyrene as a fluorescent probe, the ratio between two peaks from the pyrene emission spectra (I₁/I₃) strongly decreased as hydrophobic micro-surroundings formed due to the self-assembly process. The UV–VIS spectra of a cationic dye solution, R6G, was studied because dilute solutions of the dye in equilibrium form measurable ratios of dimers and monomers. The absorbance was modified as micro-surroundings with different polarities were formed. These three methods demonstrated that nano-structuration was present prior to the occurrence of the sol–gel process. The combination of C₁₆TMS with other alkyltrialkoxysilane precursors having hydrocarbon chain lengths between C₁ and C₈ provided further evidence for a nonlinear dependence of the refractive indice and fluorescence spectra of pyrene. The properties of the final hybrids obtained by the sol–gel process were significantly affected by the precursor hydrocarbon chain lengths. DSC, XRD and FTIR measurements were used to show the plasticizing phenomena of C₁₆ as other alkyltrialkoxysilanes (i.e., C₁–C₈) were added.

Effects of ferrocenyl group on refractive index of colloidal crystal system formed by polymer-grafted silica in organic solvent

Colloidal crystallization of copolymer-grafted silica containing ferrocenyl groups in organic solvents and effects of ferrocenyl groups on effective refractive index of colloidal crystal systems were investigated. Poly(ferrocenyl metharylate (FeMA)-co-methyl methacrylate (MMA)-grafted silica gave colloidal crystallization in dimethylformamide and acetonitrile. The colloidal crystals exhibited characteristic coloration due to cooperative effects of specific absorption at 400–500 nm by ferrocenyl group and transmission of 700–800-nm light through the crystals. It was observed that effective refractive index of colloidal crystals systems of poly(FeMA-co-MMA)-grafted silica was higher than that of poly(MMA)-grafted silica. Normalized effective refractive index of the system linearly increased with mole fraction of FeMA in grafted copolymer. However, poly(FeMA-block-MMA) did not bring effective increase of the index because of bias formation of ferrocenyl group on silica.     

Phase Gratings in Photoreactive Polymers:A Way to Optically Pumped Organic Lasers

 Poly-(4-vinylbenzyl-thiocyanate) (PVBT) was investigated as a photoreactive polymer which changes its refractive index upon UV irradiation as is required for the production of phase gratings. After UV irradiation, the refractive index of PVBT films increased from n_D ²⁰ = 1.629 to n_D ²⁰ = 1.660 (Δn = +0.031). The change in the refractive index resulted mainly from the photoinduced isomerization of thiocyanate (SCN) to isothiocyanate (NCS) groups. It was possible to modify irradiated PVBT with 1-naphthylmethyl amine which lead to a further increase of the refractive index. Both the isomerization and the modification were followed with FTIR spectroscopy. This modification of the irradiated zones also yields an advantageous stabilization of phase gratings enscribed in PVBT. The investigations were carried out in the realm of novel organic distributed feedback (DFB) lasers.     

Polycyclic rod-shaped azo dyes based on aminophenylpyrimidines

We have synthesized rod-shaped tricyclic monoazo and bisazo dyes based on amino derivatives of arylpyrimidines and N,N-dialkylanilines orp-nitroso-N,N-dialkylanilines. We have shown that the process of azo coupling of the diazonium salt obtained from 2,5-bis(p-arninophenyl)pyritnidine is accompanied by dediazoniation, with substitution of the diazonium group by hydrogen or an aryl group. The monoazo dyes obtained display mesomorphic properties which are absent in the bisazo dyes.Novosibirsk Institute of Organic Chemistry, Siberian Division of the Russian Academy of Sciences, Novosibirsk 630090. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 693–702, May, 1996. Original article submitted January 25, 1996.     

Phase Gratings in Photoreactive Polymers:A Way to Optically Pumped Organic Lasers

Summary.  Poly-(4-vinylbenzyl-thiocyanate) (PVBT) was investigated as a photoreactive polymer which changes its refractive index upon UV irradiation as is required for the production of phase gratings. After UV irradiation, the refractive index of PVBT films increased from n_D ²⁰ = 1.629 to n_D ²⁰ = 1.660 (Δn = +0.031). The change in the refractive index resulted mainly from the photoinduced isomerization of thiocyanate (SCN) to isothiocyanate (NCS) groups. It was possible to modify irradiated PVBT with 1-naphthylmethyl amine which lead to a further increase of the refractive index. Both the isomerization and the modification were followed with FTIR spectroscopy. This modification of the irradiated zones also yields an advantageous stabilization of phase gratings enscribed in PVBT. The investigations were carried out in the realm of novel organic distributed feedback (DFB) lasers. Received August 22, 2000. Accepted September 22, 2000     

Determination of molecular weight of polyethylene glycol using size-exclusion chromatography with multi-angle laser light scattering and acid–base titration

Size-exclusion chromatography with multi-angle laser light scattering (SEC-MALLS) and acid–base titration were used to determine the molecular weight of a polyethylene glycol with low molecular weight. All potential uncertainty factors for each measurement were evaluated using cause-effect diagrams. Weight analysis was applied to harmonize the two different measurement results. It was found that the main uncertainty sources of SEC-MALLS measurement arose from the dn/dc value, the calibration constant of the differential refractive index (DRI) detector, and the intermediate precision of the instrument, while the sample mass, the titration volume and the concentration of titrant contributed to the uncertainty of titration measurement. The weighted mean value of the two measurement results was taken as the molecular weight of the polyethylene glycol.