侧链密度对聚酰亚胺取向膜性能的影响

成功地合成了二胺单体十二烷氧基苯-4′,4″-二氨基三苯胺(DPDTA),并用此单体与3,3′-二甲基-4,4′-二氨基二苯甲烷(DMMDA)和二苯醚四羧酸二酐(ODPA)共缩聚,采用低温缩聚-热酰亚胺化、通过调节共聚物组成制备了2种聚酰亚胺(PI)。利用FT-IR、NMR、UV-Vis与DSC等手段对合成二胺单体及PI进行了结构表征和性能测试。研究了其取向性能、透光性能和耐热性能。结果表明,在摩擦前,含10%DPDTA的PI不能诱导液晶分子取向,含25%DPDTA的PI能诱导液晶分子垂直取向,预倾角可达89.6°。而摩擦后,两种PI都能使液晶分子平行取向,预倾角分别为1.8°和2.4°。两种PI膜在500～800nm区域透光率都在80%以上,玻璃化温度都在230℃以上。     

基于4-辛氧基联苯酚-3,5-二氨基苯甲酸酯的聚酰亚胺的合成及性能研究

利用4-辛氧基联苯酚-3,5-二氨基苯甲酸酯(C8)、3,3′-二甲基-4,4′-亚甲基二苯胺(DMMDA)以不同比例与4,4-氧双邻苯二甲酸酐(ODPA)一步法聚合制得第一体系不同二胺含量的聚酰亚胺(PI)。研究了二胺含量对PI的溶解性、取向性、预倾角和热稳定性的影响。用C8、DMMDA以相同比例与ODPA、均苯四甲酸酐(PMDA)、3,3′,4,4′-二苯甲酮四羧酸二酐(BTDA)一步法反应,制得第二体系不同二酐结构的PI,研究了二酐结构对PI溶解性和热稳定性的影响。     

新型可溶性聚酰亚胺液晶垂直取向剂的合成

利用4-十二烷氧基联苯酚-3,5-二氨基苯甲酸酯、3,3′-二甲基-4,4′-亚甲基二苯胺(DMMDA)按不同比例和4,4-氧双邻苯二甲酸酐(ODPA)通过一步法共聚合成一系列聚酰亚胺,该聚酰亚胺在N-甲基吡咯烷酮(NMP)、N,N-二甲基甲酰胺(DMF)、N,N-二甲基乙酰胺(DMAC)、二甲基亚砜(DMSO)以及氯仿(TCM)等溶剂中显示出良好的溶解性,并且显示出优异的垂直取向性能,即使摩擦以后所引起的预倾角也未出现显著的下降。     

聚合工艺对联苯侧链型聚酰亚胺薄膜取向性能的影响

以4,4′二氨基二苯醚(ODA)、 3,5-二氨基苯甲酸{6-[4′-(苯基)苯氧基]}己基)酯(C6-DABBE)、4,4′-二苯醚四羧酸二酐(ODPA) 为单体,分别采用一步法和两步法共聚合成一系列含有联苯侧链的聚酰亚胺.采用衰减全反射红外光谱(ATR-FTIR)、表面能、原子力显微镜(AFM)、光电子能谱(XPS)等测试手段对薄膜的基本性能进行了研究.通过对预倾角的测量考察了液晶分子在联苯侧链聚酰亚胺薄膜上的取向性能.结果表明,一步法和两步法合成的聚酰亚胺表面分子结构基本一致,都能使液晶分子表现出良好的取向性能;液晶分子的预倾角随着聚酰亚胺侧链含量的增加而增加;由于两步法更有利于侧链在表面富集,所以采用两步法可获得更大的预倾角.     

聚酰亚胺主链结构对液晶取向膜性能的影响

采用一步法,以N,N-二(4-氨基苯基)-4-(十二烷氧基联苯基)-4’-氨基苯醚(C12-BAAPE)为控制预倾角的功能性二胺,2,2’-双三氟甲基-4,4’-联苯二胺(TFDB)或4,4’-二氨基二苯醚(ODA)为辅助二胺,分别与2,2’-双(3,4-二羧苯基)六氟丙烷四羧酸二酐(6FDA)和4,4’-联苯醚二酐(ODPA)聚合,得到三种主链结构不同的聚酰亚胺(PI-1、PI-2和PI-3)。利用NMR、FT-IR、DSC、TGA、偏光显微镜和预倾角测试仪对聚合物的结构、热性能以及制备的液晶盒的取向性进行了表征,同时测试了3种PI的溶解性能。结果表明,PI-2液晶取向膜的耐摩擦性能明显优于PI-1和PI-3,且具有更高的玻璃化转变温度(Tg)和分解温度(Td),更好的溶解性能。分子模拟(MS)表明,由于PI-2分子主链垂直构象的存在,增加了分子链的刚性,因而提高了取向膜的耐摩擦性能。     

聚酰亚胺添加剂对液晶预倾角的影响

液晶取向剂是制造液晶显示器的关键材料之一.目前对聚酰亚胺结构对液晶预倾角的影响研究较多,而添加剂对预倾角影响的研究还较少.文章用均苯四甲酸二酐(PMDA),4[(4-氨基苯基)-二(4-甲氧基苯基)甲基]苯胺,1,2,3,4-环丁烷四羧酸二酐(CBDA),4-己烷氧基联苯酚-3′,5′-二胺基苯甲酸酯和不同含量的添加剂制备了聚酰亚胺液晶取向剂.通过偏光显微镜观察,液晶分子在4种PI膜上都获得了均匀取向.研究发现,含添加剂的PI膜具有良好的耐溶剂性能,液晶分子的预倾角随添加剂含量的增加先增大后减小.     

聚酰亚胺单体配比对液晶预倾角的影响

液晶取向剂是制造液晶显示器的关键材料之一,目前文献大多研究聚酰亚胺结构对液晶预倾角的影响,而单体配比对预倾角影响的研究还较少。文章用均苯四羧酸二酐(PM-DA)、4,4′-二氨基二苯甲烷(MDA)和4-(4-(三氟甲氧基)苯甲酰基)环己基-3,5-二胺基苯甲酸酯(TBCA)制备了一系列三元共聚型聚酰亚胺液晶取向剂,用原子力显微镜对取向剂诱导液晶分子取向能力进行了考察,首次研究了单体配比对液晶预倾角的影响。研究发现,所有取向剂对液晶分子均有较好的取向性能;液晶分子的预倾角随TBCA含量增加而增大;在保持两种二胺配比不变的情况下,随着二酐含量增加而先增大后减小。并最终在单体配比为n(PMDA)∶n(MDA)∶n(TBCA)=104∶60∶40的条件下,合成了一种预倾角高达7.7°、成本较低的聚酰亚胺液晶取向剂。     

聚酰亚胺制备条件对液晶预倾角的影响

液晶取向层性能优劣直接影响液晶分子在基板表面的排列效果,进而影响液晶显示器的光电性能,因此是制造液晶显示器的关键材料之一。文献大多研究聚酰亚胺结构对液晶预倾角的影响,而加料顺序对预倾角影响的研究,迄今还未引起注意。文章用均苯四酸二酐(PMDA)、4,4′-二胺基二苯甲烷(MDA)和具有较大支链的4-(4-(三氟甲氧基)苯甲酰基)环己基-3,5-二胺基苯甲酸酯(TBCA)等单体制备聚酰亚胺(PI),首次研究了单体加料顺序对液晶预倾角的影响,同时也研究了二胺配比对液晶预倾角的影响问题,并探讨了预倾角的热稳定性等问题。实验发现:先将PMDA加入TBCA的NMP溶液中,待PMDA完全溶解后,再加入MDA继续反应2 h,可得到预倾角为4.1°的聚酰亚胺液晶取向剂,且液晶盒在120℃下保持4 h后预倾角没有明显变化,预倾角稳定性良好。     

聚酰亚胺液晶垂直取向膜的制备与性质

虽然传统的平行取向技术已广泛应用于液晶显示器的生产,但其存在窄视角、低对比度和慢响应时间等问题,因此液晶分子的垂直取向技术在国外已经被广泛研究。在实验中,一种含有液晶结构侧链的聚酰亚胺通过均苯四羧酸二酐(PMDA),4,4′-二胺基二苯甲烷(MDA)和4-己氧基联苯酚-3′,5′-二胺基苯甲酸酯(C6BBDA,实验室自制)共聚被制备,并且被用作液晶取向膜,研究其取向性能。试验发现,该种聚酰亚胺作为取向膜可以诱导液晶分子垂直取向,即使在摩擦之后依然可以获得大于89°的预倾角;使用正交偏光显微镜观察所制得液晶盒中的液晶取向效果,发现垂直取向均匀良好;为了测试该垂直取向的热稳定性,将制备的液晶盒在120℃下烘烤12h后,偏光显微镜下观察发现垂直取向仍然良好均匀,表明该取向膜具有良好的热稳定性。     

全芳热致性液晶高分子/玻纤原位复合材料的合成与表征

以对羟基苯甲酸(HBA)、4,4′-联苯二酚(HB)、1,3-二溴丙烷(DP)、对苯二甲酸(TA)为共聚物单体,玻纤为增强共聚组分,采用原位熔融缩聚的方法,一步混合直接投料聚合出全芳香族液晶共聚酯/玻纤原位复合材料。用核磁共振(1HNMR)、差热分析(DSC)、偏光显微镜(POM)、扫描电镜(SEM)等测试分析手段对复合材料的结构、热性能和液晶特性进行了表征。研究结果表明,合成所得的复合材料呈现明显的向列性热致液晶的特性,取代基的引入降低了复合材料的熔点,而取代基链长直接影响复合材料的熔点。玻纤的加入增强了复合材料的强度,在TLCP的基体中,玻纤拥有良好的取向性,同时TLCP也有自纤化现象的产生。     

添加剂对高双折射液晶紫外稳定性影响

高双折射液晶在液晶显示中具有重要的应用价值,但是由于分子结构中含有不饱和共轭结构,在紫外下不稳定,本文对高双折射液晶紫外不稳定的问题进行了研究。首先在混晶母体A中分别加入几种不同结构的添加剂三苯氧膦、丙基双环己基甲醛、丙基苯(3,5-2F)溴苯、UV-P,搅拌使其溶解均匀,将液晶灌入TN-7.0-R测试盒,在紫外下曝光后测试混晶的各项参数。实验结果表明:UV-P明显提高了高双折射液晶的抗紫外性能,因为UV-P的紫外吸收光谱带与高双折射液晶母体A的紫外吸收光谱带最接近。     

Liquid crystal applications in photonics

We developed new optical switches based on nematic and ferroelectric liquid crystal (LC) cells for photonics applications. Certain new LC switches based on the effect of total internal reflection in nematic LC and deformed helix ferroelectric effect ferroelectric LC with very fast response time were developed. Fast bistable optical switches of the light polarization based on ferroelectric liquid crystal cells were proposed. The switches are characterized by 100 us switching time and 26 dB crosstalk at the wavelength of 632.8 nm and bistable, i.e., required zero power consumption in the switch state.High frequency hysteretic free electrically controlled 0-2π phase modulation of light has been proposed using a very short helix pitch (less than 400 nm) deformed helix ferroelectric liquid crystal. The electrically controlled 0-2π hysteretic free phase modulation was achieved at the driving voltage frequency up to 4 kHz and the voltage amplitude of 32 V. The application of fast V-shaped deformed helix ferroelectric ferroelectric LC (DHF-FLC) for new active-matrix liquid crystal display (LCD) and optical data processing devices is envisaged.Photoalignment technology can be very useful for the new generation of liquid crystal devices as well as in new photovoltaic, optoelectronic and photonic devices based on highly ordered thin organic layers. We have investigated the LC photoalignment in superthin tubes, which are basic elements of switchable photonic crystal/liquid crystal structures and obtained the order parameter comparable with usual homogeneous nematic LC cells. We studied LC alignment on silicon surfaces with submicrometer-sized straight and curved waveguide profiles. The liquid crystal cladding refractive index was then varied according to the applied voltage, and subsequently the microresonator resonance wavelengths were tuned. Based on our initial measurements, the free spectral range (FSR) wavelength shift within the range of 20 nm was obtained, which is comparable with a thermooptic effect. The new voltagecontrollable Si-based add drop filters are envisaged based on this principle.     

阳离子表面活性剂/醇/水三元体系液晶的研究

在25℃时绘制了阳离子表面活性剂3-辛烷氧基-2-羟丙基三甲基溴化铵(R8TAB)／正丁醇／水的三元体系的相图，在偏光显微镜下发现该体系中的某些区域呈现出彩色液晶。一些绚丽的彩色照片清楚地显示了不同的液晶纹理。用。HNMR和小角X衍射与纹理照片对照．确定了该体系的液晶结构类型，用差示扫描量热法证实了液晶结构的转化。研究分析了液晶层厚度、温度和时间对液晶颜色变化的影响，结果表明．液晶膜厚度是产生颜色的关键因素。     

硅氧烷近晶相单体的合成及应用

为了改善聚合物分散液晶（PDLC）在智能玻璃领域应用中存在的视角较差、透明态效果不够理想以及无法实现双稳态的缺点,合成了一种具有硅氧烷长链结构的近晶相液晶单体,并将该近晶相液晶单体用于近晶相的混晶配方制备了简单的近晶相双稳态器件。以10-溴-1-癸烯、对羟基联苯氰和1,1,1,3,3,5,5-七甲基硅氧烷为原料,以较高收率合成了该近晶相液晶单体。通过核磁共振（NMR）和元素分析（EA）确认了分子结构的正确性;利用偏光显微镜（POM）、示差扫描量热仪（DSC）等对其单体液晶参数和混晶配方参数进行测定,通过基板处理、液晶盒制备、器件老化等过程制备了近晶相双稳态器件。实验表明,该近晶相混晶配方制得的近晶相双稳态器件具有较宽的近晶相温宽（-62℃~60℃）,较低的驱动电压（50 V）,透明态参数优秀（雾度=0.06%,平行光透过率=90.34%）,完全无视角缺陷,且可以仅在状态切换时需要通电实现双稳态效果。该硅氧烷类近晶相液晶单体对于改善近晶相混晶配方有着重要的作用,该材料制备方法简单,原料易得,收率较高,易于生产,对于智能玻璃领域的市场推广有着重要的作用。     

双波长晶体激光器

本文介绍了烈波长晶体激光器的概况, 重点描述了我们在双波长晶体激光器方面的研究工作。这些工作如下:建立了多波长激光器的振荡条件, 用它分析、比较了Nd:YAG, Nd:YLF, Nd:BEL和Nd:YAlO3(Nd:YAP)等晶体实现4F3/2-4I11/2和4F3/2-4I13/2跃迁双波长激光的可能性, 分析表明上述晶体均能实现脉冲双波长激光.但只有Nd:YAP晶体能实现连续双波长激光运转。根据这判断, 我们利用Nd:YAP晶体, 首次获得了晶体双波长连续激光, l079.5 nm和1341.4 nm输出功率分别选23.9 W和25.4 W。并研制成Nd:YAG和大能黄Nd:YAP双波长激光器 实验表明, 这二种激光器中二个波长的输出具有较好的时间和空间的重叠性 此外, 我们还研制成1655 nm和1663 nm双渡长及271l nm, 2730 nm和2790 nm三波长Er:YAP脉冲激光器。     

Trellis and convolutional precoding for transmitter-based interference presubtraction

This paper studies the combination of practical trellis and convolution codes with Tomlinson-Harashima precoding (THP) for the presubtraction of multiuser interference that is known at the transmitter but not known at the receiver. It is well known that a straightforward application of THP suffers power, modulo, and shaping losses. This paper proposes generalizations of THP that recover some of these losses. At a high signal-to-noise ratio (SNR), the precoding loss is dominated by the shaping loss, which is about 1.53 dB. To recover shaping loss, a trellis-shaping technique is developed that takes into account the knowledge of a noncausal interfering sequence, rather than just the instantaneous interference. At rates of 2 and 3 bits per transmission, trellis shaping is shown to be able to recover almost all of the 1.53-dB shaping loss. At a low SNR, the precoding loss is dominated by power and modulo losses, which can be as large as 3-4 dB. To recover these losses, a technique that incorporates partial interference presubtraction (PIP) within convolutional decoding is developed. At rates of 0.5 and 0.25 bits per transmission, PIP is able to recover 1-1.5 dB of the power loss. For intermediate SNR channels, a combination of the two schemes is shown to recover both power and shaping losses.     

One-dimensional equivalent circuit simulation of a photodiode-basedspatial light modulator

A one-dimensional (1-D) equivalent circuit model for an optically addressed, photodiode-based spatial light modulator (SLM) is presented. The model is first verified for a liquid crystal (LC)-based SLM via a 1-D experimental version of the device followed by a detail simulation using SPICE. It was found that the optical performance of the LC-SLM was most sensitive to the liquid crystal thickness, substrate doping concentration, and the photodiode leakage current. This model can be a useful tool for the analysis of the optical performance (such as photosensitivity and image uniformity) of a variety of photodiode-based SLMs as a function of their structural and operating parameters     

Analysis of tunable photonic crystal devices comprising liquid crystal materials as defects

The tuning properties of two-dimensional dielectric and metallic photonic crystals, which contain nematic liquid crystal materials as defect elements or layers, are thoroughly analyzed using appropriate formulations of the finite difference time domain (FDTD) method. Our methodology correctly incorporates the anisotropy introduced by the liquid crystal materials together with the dispersive properties of the metallic elements; it is used for calculating both the dispersion diagrams of the defect-free photonic crystal as well as the device response in the presence of the defect elements. Numerical simulations reveal that defect states originating from the liquid crystal impurities can be effectively tuned by the application of a local static electric field. Indeed, tuning ranges up to almost 100 nm can be achieved requiring operating voltages lower than 4 V. It is also concluded that the placement of a defect mode relative to the bandgap edges greatly influences both its linewidth as well as its tuning range.