PHOTOINDUCED HOLOGRAPHIC PHASE GRATINGS BURIED IN AZOBENZENE SIDE-CHAIN POLYMER FILMS WITH A CHIRAL GROUP

An optically active polymer (PM1) containing azobenzene moieties with a chiral group (s-2-methyl-butyl) wassynthesized by homopolymerization of monomer, 4-[2-(methacryloyloxy)ethyloxy-4'-(s-2-methyl-1-butyl oxycarbonyl)azobenzene, using the free radical polymerization method. The polymer dissolved in tetrahydrofuran (THF) could be easilyprocessed into high optical quality films. The optical anisotropy of the polymer films was investigated by polarizing opticalmicroscopy (POM). The experimental results showed that irradiation with a circularly polarized beam could align theorientation of the molecules in the polymer films. Moreover, the holographic phase gratings of photo-induced polymer filmswere detected by atomic force microscopy (AFM) and POM. In comparison with polymer containing no chiral group, it wasfound from the preliminary measurement of the photo-induced holographic phase gratings that PM1 containing a chiralgroup could form holographic phase gratings buried in the films.     

偶氮苯聚合物(PGMAA-20)膜光栅结构的分子取向机制

设计合成及表征了一种含偶氮苯聚合物(PGMAA 20)材料.利用两束S偏振光作为泵浦光在PGMAA 20膜上刻写光栅并观察光栅的衍射信号;然后再用相衬显微镜直接观察偶氮苯薄膜上的光栅结构,并以分子取向机制为基础对光栅形成和消除过程提出了新解释,这种观点被实验观察结果进一步证实.     

含手性末端基偶氮聚合物膜的全息光栅研究

偶氮苯侧链型高分子由于其含有偶氮苯基团 ,在光作用下会发生可逆的顺反异构过程 ,具有光致取向特性 ,在光学处理、衍射光学、投影显示、光开关等许多方面具有潜在的应用性[1] .近 1 0多年来国内外学者对此类化合物进行了广泛的研究 ,已有文献报道可利用Ａｒ+激光束在偶氮苯聚合物薄膜上直接“写入”表面凸起光栅 ,并且通过原子力显微镜观测到光栅起伏 .这种光栅很稳定 ,并可以利用光学方法“擦去” .偶氮苯聚合物上述独有的性质引起了许多学者的兴趣[2 ,3] .另一方面 ,由于旋光性聚合物在光学物理性质上的优势 ,我们已将手性基团引入偶氮苯…     

偶氮苯聚合物膜的光致高密度存储及其三维微结构的研究

设计、合成及表征了一种偶氮苯聚合物(PGMAA-20)。研究了该偶氮苯聚合物薄膜中的高密度光学存储和三维微结构,并成功地将20套光栅储存在样品中同一个点上,储存密度是已报道的两倍;用简单的2波混频光路在该材料中刻写出长方格子和六角星型的微结构,在制作多重不同周期不同角度的高密度光栅结构的实验过程中,观察到不同周期光栅的刻写顺序对整个微结构形成的最终结果具有决定性的影响。     

Photo-fabrication of surface relief gratings on polymer films

Surface relief gratings were optically produced on a number of azobenzene-based polymer films. The surface grating formation was investigated by monitoring the diffraction efficiency and using atomic force microscopy. The effect of the structure of the chromophores on surface modulation was investigated. The surface deformation process depended on the polarization state of the writing beams. The localized variations of the light intensity and alteration of the resulting electric field polarization were essential writing conditions to the formation of the surface relief gratings. The surface pattern from straight edge diffraction established that the surface profile of the recorded gratings is proportional to negative gradient of the intensity pattern incident on the polymer film.     

Large Photoinduced Refractive Index Change in a Polyimide Film by Charge‐Transfer Complex Formation with a Polymer‐Bound Phenylazide Fragment

A large photo‐induced refractive index change as large as 0.014 at 632.8 nm in thermostable transparent polymer films has been realized for the first time by using photoirradiation of polyimide precursor films containing a phenylazide and successive imidization. The phenylazide fragment forms a charge‐transfer complex with imide moiety. The films maintained high transmittance in a wide visible region in contrast to usual polyimide films. This value of refractive index change is sufficient to make thermostable channel waveguides and other optical devices.     

热诱导金属/聚合物膜系图案化控制的研究

近年来 ,在简单体系上形成复杂规则的图案已引起诸多学者的注意 ,其中以聚合物为母体的体系发展了模板、局部紫外照射和激光诱导等一系列技术 ,从而得到可控的表面图案[1～ 6] .本文用激光刻蚀法对溅射在聚合物膜上的金属薄膜进行处理 ,在热诱导情况下使金属 /聚合物膜系表面产生了规则的图案 .薄膜热应力的可控释放作用和激光刻蚀造成的区域局限作用被认为是诱导这种可控图案产生的两种基本要素 .通过控制激光刻蚀区域 ,可控制薄膜表面形貌变化 ,从而实现可控的图案化设计 .1　实验部分1.1　原料及仪器　聚苯乙烯 (PS) :北京燕山石油化工…     

Conducting polymer diffraction gratings on gold surfaces created by microcontact printing and electropolymerization at submicron length scales

Conducting polymer diffraction gratings on Au substrates have been created using microcontact printing of C18-alkanethiols, followed by electropolymerization of either poly(aniline) (PANI) or poly(3,4-ethylenedioxythiophene) (PEDOT). Soft-polymer replicas of simple diffraction grating masters (1200 lines/mm) were used to define the alkanethiol template for polymer growth. Growth of PANI and PEDOT diffraction gratings was followed in real time, through in situ tapping-mode atomic force microscopy, and by monitoring diffraction efficiency (DE) as a function of grating depth. DE increased as grating depth increased, up to a limiting efficiency (13-26%, with white light illumination), defined by the combined optical properties of the grating and the Au substrate, and ultimately limited by the loss of resolution due to coalescence of the polymer films. Grating efficiency is strongly dependent upon the grating depth and the refractive index contrast between the grating material and the surrounding solutions. Both PEDOT and PANI gratings show refractive index changes as a function of applied potential, consistent with changes in refractive index brought about by the doping/dedoping of the conducting polymer. The DE of PANI gratings are strongly dependent on the pH of the superstrate solution; the maximum sensitivity (DeltaDE/DeltapH) is achieved with PANI gratings held at +0.4 V versus Ag/AgCl, where the redox chemistry is dominated by the acid-base equilibrium between the protonated (emeraldine salt) and deprotonated (emeraldine base) forms of PANI. Simulations of DE were conducted for various combinations of conducting polymer refractive index and grating depth, to compute sensitivity parameters, which are maximized when the grating depth is ca. 50% of its maximum obtainable depth.     

Confinement of surface patterning in azo-polymer thin films

Azobenzene polymer thin films are known to spontaneously generate surface patterns in response to incident light gradients. This peculiar process is investigated in terms of the dynamics of the various azobenzene photomotions, which occur on different length scales. In particular, the formation and thermal erasure of surface relief gratings are measured as a function of film thickness and by using combinatorial samples with thickness gradients. The thermal erasure of gratings in this system provides a direct measure of the glass-transition temperature, which is found to deviate substantially from the bulk value. Thin azo films exhibit a glass transition up to 50 K higher than the bulk. These dynamical measurements allow the authors to probe the length scale of mass transport, which is found to be approximately 150 nm. Furthermore, surface mass transport is completely arrested in thin films<40 nm. According to these results, mass transport involves the coordinated motion of many polymer chains in the depth of the sample, rather than surface diffusion of individual chains.     

The effect of nanographites dispersed in Undec-10-enic acid on optical property and morphology of PDLC films

The electric conductivity is an important factor for reducing the switching voltage of polymer-dispersed liquid crystals (PDLC) films. The electric conductivity of polymer matrix is changed by doped nanographite which is uniform dispersed in polymer matrix in acid condition. The influence of doped nanographite to switching electric field is studied. With increasing of doped nanographite, the switching voltage is dramatically reduced. The effect of nanographite on the polymerization and electro-optic are discussed. The kinetic polymerization of the PDLCs is monitored in lights scattering by UV/VIS spectrometer. The polymerization speed is compared by the max scattering point in different samples which doped by nanographite. The electro-optic of PDLCs films is measured by Polarimeter (PerkinElmer Model 341) to determine the threshold voltage. Information gained from polarizing optical microscope and Fourier transform infrared image depict the morphology of the liquid crystal droplets dispersed in polymer matrix.     

Fabrication of TiO2 Grating with Composites of Azobenzene Polymer and TiO2 Nanoparticles

We have used the formation of surface relief gratings (SRG) on azobenzene polymers to manipulate TiO₂ nanoparticles and to fabricate TiO₂ nanoparticle gratings. Suspensions of an azobenzene polymer (PDO3) and TiO₂ were used to spin coat thin films on glass slide substrates. By interfering coherent light from an Argon laser on the surface of the PDO3‐TiO₂ composite films, SRGs were fabricated. Atomic force microscopic images of the SRGs show TiO₂ nanoparticles dispersed throughout the sample, and in particular, at the peaks of the SRG after oxygen plasma treatment. The lateral forces acting on the azobenzene polymer during the SRG fabrication drag the TiO₂ nanoparticles. These results indicated that it is feasible to create TiO₂ nanoparticle gratings with the composites.     

The influence of light on the conduction switching effect in thin polymer films

The effect of exposure to visible light on pressure- and field-induced switching from the low-conductivity to the high-conductivity state in thin polymer films was experimentally studied. The switching effect was observed in poly(diphenylene phthalide) and polyvinylcarbazole layers doped with a cyanine dye. Doping with the dye reduces the voltage at which the polymer is switched to the conducting state. However, an Al—dye complex is formed with time, which results in an increase in the switching voltage and pressure. It was found that illumination leads to the appearance of additional conductivity in the sample; in the samples prone to switching to the conducting state, light stimulates switching and leads to blocking the injection sites for charge carriers in the low-conductivity state.     

偶氮聚合物表面起伏光栅用于液晶定向研究

液晶显示具有低功耗、高画质、轻巧等优点，广泛应用于各种平板显示装置．使液晶分子能在显示器中均匀的定向排列是液晶显示的关键技术之一．液晶定向技术的主要方法有摩擦法、SiOx等氧化物或Au、Pt等金属蒸镀法、紫外偏振光(或激光)辐照法等．所谓摩擦法，即通过将基片在均匀移动的丝绒布表面摩擦来实现的．一般认为摩擦法是通过摩擦在基板表面形成的微沟槽来诱导     

Electro-nanopatterning of surface relief gratings on azobenzene layer-by-layer ultrathin films by current-sensing atomic force microscopy

The electro-nanopatterning and mechanism of pattern formation in azobenzene-containing layer-by-layer (LbL) ultrathin films is described using surface probe microscopy techniques. First, arrays of nanodots were patterned on these films to investigate applied time at constant voltage bias dependence in electro-nanopatterning. The anisotropic mass transport and polar alignment of the azobenzene-containing films were observed after applying the electric field and heating the sample locally with the cantilever tip. On the basis of this novel phenomenon, small-sized surface relief gratings (SRG)s and their alignment were fabricated and observed by current-sensing atomic force microscopy. The rate of mass transport for the polymer is mainly controlled by the applied time at constant voltage bias between the cantilever and the electrode/substrate.     

Optical switching property from a laser beam propagating in a polymer dispersed liquid crystal film

Optical switching has been studied in epoxy-based polymer dispersed liquid crystal films. A 'self-transparency' effect is observed due to refractive index variations thermally induced either by heating the sample with a hot stage, or by absorption of the incident laser power. The switching phenomena were studied for different liquid crystal contents in the composites, and experimental evidence of light modulation by a probe beam is also reported. The thermo-optical behaviour of the material is correlated with the morphology of the samples. The results obtained verify the possibility of employing this type of material in optical devices based on the thermo-optical switching effect.     

Waveguides and gratings fabrication in zirconium-based organic/inorganic hybrids

Sol–gel derived poly(oxyethylene)/siloxane organic/inorganic di-ureasil hybrids containing different amounts of methacrylic acid (McOH, CH₂=C(CH₃)COOH)) modified zirconium oxo-clusters (Zr-OMc) were processed as thin films deposited in glassy substrates via spin coating and as transparent and shape controlled monoliths. Channel monomode waveguides and diffraction gratings were UV patterned using the Talbot interferometer and the Lloyd mirror interferometer experimental setups. The time dependence of the diffraction gratings efficiency was studied for hybrids containing different amounts of Zr-OMc. Finally, the number of propagating modes and the refractive index gradient within the waveguide region, determined as a Gaussian section located below the patterned channel, was evaluated and modeled, a maximum index contrast of 2.43 × 10^?5 being estimated.     

Optical switching property from a laser beam propagating in a polymer dispersed liquid crystal film

Optical switching has been studied in epoxy-based polymer dispersed liquid crystal films. A 'self-transparency' effect is observed due to refractive index variations thermally induced either by heating the sample with a hot stage, or by absorption of the incident laser power. The switching phenomena were studied for different liquid crystal contents in the composites, and experimental evidence of light modulation by a probe beam is also reported. The thermo-optical behaviour of the material is correlated with the morphology of the samples. The results obtained verify the possibility of employing this type of material in optical devices based on the thermo-optical switching effect.     

Development and application of patterned conducting polymer thin films as chemoresponsive and electrochemically responsive optical diffraction gratings

We describe the preparation of two-dimensionally patterned polyaniline (PANI) thin films via microtransfer molding and electropolymerization techniques. This procedure yields reproducible conducting polymer patterns with excellent feature periodicity, making them useful as diffraction gratings. The fabricated polymer gratings were characterized via tapping-mode atomic force microscopy. Spectroelectrochemistry was used to characterize the optical properties associated with various intrinsic PANI redox states. In accordance with the Kramers–Kronig relation for change-in-absorptivity and change-in-index-of-refraction, electrochemically induced changes in refractive index (detected via changes in diffraction efficiency) were observed to coincide with electrochemically-induced changes in the PANI electronic absorption spectrum. In addition, the higher oxidation states of PANI and the associated changes in refractive index proved accessible via chemical oxidation. Beyond the novelty of a chemically-switchable transmission grating, the response of this system points to the possibility of developing diffraction-based chemical sensing schemes.     

Nanostructures and Functionalities in Polymer Thin Films

Several examples of self-organization in thin polymer films are considered for the fabrication of nanopatterned surfaces and nanoscopic objects. Mixed polymer brushes of statistical distribution at the surface, composed of two immiscible polymers covalently bonded to the substrate phase, segregate in the sub-micrometer scale. Interplay between lateral and perpendicular (sandwich-like) segregation effects switching behavior of the thin films upon exposure to different environments. The switching between brush morphologies is used for the fabrication of adaptive/responsive surfaces. Fabrication of nano-domains based on microphase segregation in block-copolymer systems is used for structures with lateral dimensions as small as 5-50 nm. The ordered copolymer structures are applied as templates for the fabrication of membranes, nanofibers and nanoparticles.