聚合物电光调制器包覆层材料研究

随着信息技术的飞速发展 ,利用光作为信息传输、存储、处理工具的光电子信息技术将得到广泛的应用 .电光调制器是将电信号调制到光束上的电光器件 ,在光通讯领域有十分重要的应用背景[1～ 5] .与通常基于无机材料 (如 ,LiNbO3 、KH2 PO4晶体等 )的电光调制器相比 ,基于聚合物材料的电光调制器具有非线性光学系数大、能量损耗低 (聚合物材料的介电常数很低 )和制作方法简单等优点[6,7] .因此 ,可应用于聚合物电光调制器的新材料是最近一、二十年来研究的热点和前沿 ,受到人们的广泛关注 .通常Mach Zehnder聚合物电光调制器具有“三明治”…     

一种光交联电光聚合物的合成及其外部电光测量

合成了一种新的带有光交联基团的电光聚合物,其高分子基体是双酚A环氧树脂,二阶非线性生色团对硝基苯胺和光交联基团肉桂酰氯都键接在高分子链上.将聚合物溶解后旋涂成膜,对薄膜进行电晕极化.极化的后阶段用紫外光照射,使聚合物体系交联成网络结构,形成生色团取向长时间稳定的聚合物电光薄膜.用这种聚合物电光薄膜构成外部电光调制系统,测量了共面波导上的电信号.     

二阶非线性光学聚氨酯对电光效应的共振增强

二阶非线性光学聚合物是最有希望实现在电光器件方面应用的材料之一.该类材料的非线性光学系数很高,响应速度快,与半导体材料的相容性较好,且比有机和无机晶体的制备更方便.目前所用的电光调制器多为光传输型,高光学活性的极化聚合物一般光学损耗较大,尤其是其吸收波段更大,使得调制器只能在其透明波段内使用,否则,传输型波导器件由于这种损耗将无法使用.     

极化聚合物电光材料研究进展

极化聚合物由于其在集成光电子学领域的潜在应用前景已经引起了广泛关注。本文在简要介绍电光调制器及其材料有关知识的基础上,综述了近几年来极化聚合物电光材料的研究进展,主要介绍发色团和聚合物的设计、合成、并对这类材料将来的发展方向作了探讨。     

基于分子间侧向氢键作用的电光材料制备及性能

通过重氮耦合和酯化等反应制备了一系列侧向含有酰胺基团的偶氮苯类非线性光学生色团, 并将其与聚合物进行掺杂或通过分子间的侧向氢键作用制备了主客体型及超分子型的电光薄膜材料. 生色团的结构通过核磁共振谱(¹H NMR, NMR)、 红外光谱(IR)、 质谱(MS)和元素分析(EA)等进行了表征, 结果表明, 生色团形成了分子间的氢键作用. 通过紫外-可见(UV-Vis) 光谱研究了材料的极化性能. 相比主客体型电光薄膜材料, 由分子间侧向氢键作用形成的超分子型电光薄膜材料无需与聚合物基体材料复合, 更有利于提高材料的生色团含量、 极化取向度及稳定性. 通过Teng-Man简单反射法研究了主客体型和超分子型电光材料的二阶非线性光学性质, 结果表明, 基于分子间侧向氢键作用形成的超分子体系具有更大的电光系数.     

基于氢键的侧链型超分子电光聚合物的制备与表征

设计并制备了一种基于氢键的侧链型超分子聚乙烯基吡啶电光聚合物,非线性发色团与聚合物主链之间的氢键作用经红外光谱进行表征。采用氢键将发色团挂接到聚合物,可一定程度地抑制发色团分子的聚集,防止宏观相分离,实现发色团的高浓度掺杂。同时,利用超分子氢键作用挂接也可在一定程度上抑制发色团间的偶极-偶极相互作用力,测得此体系极化电光聚合物薄膜的最大电光系数为17.6 pm/V。     

树枝状电光材料研究进展

电光材料是以光子为载体的新一代信息材料. 目前, 研究的焦点主要集中在树枝状电光材料. 综述了近几年树枝状电光材料的研究进展, 主要包括树枝状电光大分子、树枝状电光高分子以及超分子自组装电光聚合物.     

基于蒽基团的光交联型非线性光学聚合物的合成与表征

在有机二阶非线性光学聚合物聚甲基丙烯酸甲酯侧链中引入可交联的蒽基团，合成含蒽基团的甲基丙烯酸甲酯类聚合物。采用紫外-可见光谱法明确蒽基团在薄膜中的光交联时间，利用蒽基团在光照条件下的可控[4+4]环加成交联反应提高聚合物的取向稳定性。差示扫描量热法（DSC）研究结果表明交联反应后聚合物薄膜的玻璃化转变温度提高了约10℃。聚合物在60℃条件下加热220 h后电光系数仍可保持原来的90%左右，交联后的二阶非线性聚合物的取向稳定性明显提升。     

枝化二阶非线性发色团分子的合成及在聚合物体系中的电光性能

设计合成了一类以2-二氰基次甲基-3-氰基-4,5,5-三甲基-2,5-二氢呋喃(TCF)为受体、己氧基取代噻吩为π电子桥的新型有机非线性光学化合物, 并利用紫外光谱、红外光谱、核磁共振以及质谱对化合物分子结构进行了鉴定, 同时对此类化合物在有机聚合物体系中的电光性能进行了表征和研究. 结果发现, 该类发色团分子与聚合物相容性好, 电光活性高, 并且随着发色团分子在聚合物体系中浓度的升高, 聚合物体系的宏观电光活性也有所提高, 甚至当发色团的掺杂质量分数高达47.2%时, 体系的电光活性仍呈上升趋势, 显示了该发色团的静电相互作用得到了明显抑制. 此时测得聚合物体系的电光系数为30 pm/V(1310 nm).     

异氰酸酯交联的环氧树脂基二阶非线性光学聚合物

通过双酚A 二 (缩水甘油醚 )与苯胺的逐步聚合反应合成环氧树脂类先驱聚合物BPAN ,进一步通过先驱聚合物的后重氮偶合反应 ,制备了侧链带偶氮生色团的二阶非线性光学聚合物BPAN 1A NT .将BPAN 1A NT与适当量的异氰酸酯交联剂M2 0S混合 ,得到了双组分非线性光学聚合物体系BPAN 1A NT M2 0S .该体系在电场极化的同时可发生交联固化 ,极化后其二阶非线性光学系数高达 10 5 2pm v(λ =1 0 6 4 μm) ,同时还具有很好的极化偶极取向稳定性 ,2 0 0℃时的非线性光学系数仍可维持在初始的 80 %以上 .上述双组分非线性光学聚合物材料 (BPAN 1A NT M2 0S)同时具有高二阶非线性光学系数和高极化偶极取向稳定温度 ,可以预期 ,在聚合物电光调制器、光开关等器件中将有很好的应用前景 .     

聚酰亚胺多层膜的制备及其在非线性光学中的应用

报道了一种通过旋涂制备NLO聚合物多层膜的方法.紫外-可见吸收光谱及膜的厚度表征说明,在所得多层膜的结构中,聚合物单层膜的厚度可以较好地控制在100~200nm之间,所得含有5个双层的NLO多层膜(厚度1.6μm)具有良好的结构均一性,光学显微镜下没有观察到明显的结构缺陷.与单层具有较大厚度的NLO聚合物薄膜(如2~4μm)相比,所得聚合物多层膜可以允许掺杂更多的发色团而不发生相分离.     

Optical and electrical control of circularly polarised fluorescence in CdSe quantum dots dispersed polymer stabilised cholesteric liquid crystal shutter

In the present communication, we report on the synthesis and electro-optic investigation of photosensitive CdSe quantum dots (QDs) dispersed polymer stabilised liquid crystal (PSCLC) luminescent gel. The assembly of the fluorescence properties of CdSe QDs facilitate the anisotropy of PSCLC gel and hence manipulates the optical and electro-optic switching properties, which was further investigated using polarised fluorescence spectrophotometer. The circularly polarised fluorescence intensity was tuned electrically so as to affect the orientations of liquid crystal in the helix. It was found that the electro-optic switching behaviour of QDs-doped sample predicts the improvement in threshold voltage and hence makes them applicable for the switchable liquid crystal contrivances with low power consumption.     

Polymer films derived from aligned and polymerised reactive liquid crystals

The principles and methods of fabricating thin polymer films with particular optical properties via the process of in‐situ photopolymerisation of reactive liquid crystals are described. The optical properties of these films are described in terms of their retardation profile. Some possible applications, such as compensation films for improving the viewing angle of a TN‐TFT liquid crystal display are discussed. A novel way of combining the properties of a quarter wave foil and a compensation film for a broad band cholesteric brightness enhancement film is also described.     

Volume-stabilized ULH structure for the flexoelectro-optic effect and the phase-shift effect in cholesterics

Flexoelectric coupling gives rise to a linear electro-optic response in cholesterics (flexoelectrooptic effect) with a uniformly lying helix (ULH) structure and this electro-optic effect is strongly reliant on the homogeneity and quality of the texture. The ULH structure, unfortunately, is complicated in itself and may be perturbed by factors such as dielectric coupling, surface/liquid crystal interactions and phase transitions, and often there is a tendency for relaxation into the Grandjean texture (standing helix structure) with time. Hence, in order to exploit the flexoelectro-optic effect in cholesterics any instability of the ULH structure must be ruled out. We have overcome these problems by incorporating a polymer network by means of photopolymerization of a reactive monomer added to the cholesteric. The volume stabilized ULH structure still exhibits the flexoelectro-optic effect, it is stable and it is also retained after heating to the isotropic phase and going back to the cholesteric phase. In addition to the flexoelectro-optic mode, the ULH structure is of interest in an electro-optic mode characterized by a pure phase-shift with no change in amplitude (transmittance). This mode, which has obvious applications in spatial light modulators, optical computing devices and electrically controlled kinoforms and phase holograms working without polarizers, is also briefly discussed.     

Charge transfer interactions in polymers and the fabrication of high frequency electro-optic modulators

The synthesis and processing of second order nonlinear optical polymeric materials for application in electro-optic devices is described with particular emphasis on (1) the synthesis and incorporation into hardened polymer lattices of chromophores characterized by large μβ (where μ is the dipole moment and β is the molecular first hyperpolarizability) values; (2) the synthesis and incorporation into hardened polymer lattices of chromophores which are capable of undergoing photo-induced conformational changes and which can be processed by new multi-color photolithography techniques into buried channel active waveguides; and (3) the processing of polymeric nonlinear optical materials appropriate for the realization of full integration with very large scale integration (VLSI) drive electronics and with silica fiber optic transmission lines. Prototype modulators have been fabricated and shown to be suitable for broadband operation from 0 to 113 GHz. Optical losses associated with waveguide wall roughness and with mode mismatch in transitioning between silica and polymeric waveguides are reduced by control of the conditions of reactive ion etching and by use of the new technique of multi-color photochemical lithography.     

Morphology and electro-optic responses of poly(methyl methacrylate)/nematic liquid crystal composite films: Effect of the polymer molecular weight

The director configuration, state of liquid crystal (LC) phase aggregation, and the electooptic properties of thin polymer films of poly(methyl methacrylate) (PMMA) containing nematic liquid crystal have been studied. Measurements included scanning electron micrograph (SEM), polarized optical micrographs (POM), and transmittance response of the film with the applied electric AC voltage and frequency. Two types of PMMA with significantly different molecular weight (M_w) were used, and the effects of polymer molecular weight on morphology and electro-optic properties of the composite films were examined. © 1995 John Wiley & Sons, Inc.     

Novel PDLC type display based on cellulose derivatives

A novel type of PDLC display utilizing solid films obtained from the cellulose derivative hydroxypropylcellulose (HPC) with molecular weights of 60000 (HPC60000) and 100000 (HPC100000), cross-linked with two different di-isocyanates, 1,4-di-isocyanatobutane (BDI) and 1,6-di-isocyanatohexane (HDI), is presented. This kind of display (optical cell) is composed of a porous elastomeric film (20-60 μm thick) of HPC-BDI or HPC-HDI, impregnated with a nematic liquid crystal and contained between two transparent conducting substrates. The electro-optic behaviour of several optical cells is studied as a function of film thickness, the molecular weight of the polymer and the cross-linking agent. The preliminary studies presented in this work show that these systems present good contrast, high transmissivity in the on state and switching times in the range of some milliseconds to hundreds of milliseconds.     

一种新型的交联极化聚合物的合成及性能研究

以成膜性能优异、主链上含有多个羟基的聚双酚A二缩水甘油醚-苯胺(BPAN)为骨架,将二阶非线性光学活性发色团分子以键合形式挂接到聚合物主链上,形成新型侧链型聚合物.此聚合物保留了原聚合物体系成膜性好和可进一步交联等优点.极化过程中以含有异氰酸酯基的同种发色团分子作为交联剂,得到发色团含量进一步提高的交联型极化聚合物.采用衰减全反射法(ATR)测得体系的电光系数(r₃₃)为6.7 pm/V(1315 nm).     

Theory-guided design and synthesis of multichromophore dendrimers: an analysis of the electro-optic effect

Extensive experimental and theoretical study suggests that interchromophore electrostatic interactions are among the most severe impediments to the induction and stability of large electro-optic coefficients in electric-field-poled organic materials. In this report, multichromophore-containing dendritic materials have been investigated as a means to minimize unwanted attenuation of nonlinear optical (electro-optic) activity at high chromophore loading. The dendritic molecular architectures employed were designed to provide optimized molecular scaffolding for electric-field-induced molecular reorientation. Design parameters were based upon past experimental results in conjunction with statistical and quantum mechanical modeling. The electro-optic behavior of these materials was evaluated through experimental and theoretical analysis. Experimental data collected from the dendrimer structures depict a reasonably linear relationship between chromophore number density (N) and electro-optic activity (r(33)) demonstrating a deviation from the dipolar frustration that typically limits r(33) in conventional chromophore/polymer composite materials. The observed linear dependence holds at higher chromophore densities than those that have been found to be practical in systems of organic NLO chromophores dispersed in polymer hosts. Theoretical analysis of these results using Monte Carlo modeling reproduces the experimentally observed trends confirming linear dependence of electro-optic activity on N in the dendrimer materials. These results provide new insight into the ordering behavior of EO dendrimers and demonstrate that the frequently observed asymptotic dependence of electro-optic activity on chromophore number density may be overcome through rational design.