液晶聚合物调控的蓄热调温材料的储热性能

通过3,3′,4,4′-二苯甲酮四甲酸二酐(BPTCD)与聚乙二醇2000(PEG2000)的酯化反应,制备了具有光热响应的相变聚合物BPTCD-PEG,该聚合物在相变过程中可以形成液晶态.在偏光显微镜下,BPTCD-PEG呈典型的焦锥花形向列相液晶织构.采用DSC对BPTCD-PEG的热性能进行表征,结果表明,BPT...     

Electro‐optical properties of polymer dispersed liquid crystal prepared by successively controlled living radical polymerization

Polymer dispersed liquid crystal (PDLC) films were obtained by successive controlled living radical polymerizations: starting polystyrene (M1) was obtained by reversible addition‐fragmentation polymerization (RAFT), M1 was converted to P‐chloromethylated polystyrene (M2) which was grafted with polystyrene branches by atom transfer radical polymerization (ATRP) to yield RAFT‐initiating graft polymer containing trithiocarbonate moieties in the backbone (M3, RAFT‐active grafted polystyrene), and then PDLC films were prepared by photo‐induced RAFT copolymerization of methyl acrylate with M3 in the presence of a nematic liquid crystal. The electro‐optical properties of the films were investigated for the purpose to apply them to optical devices. Experimental results showed that preferable properties could be acquired by controlling the amount of M3 and the liquid crystal E7 in the polymer matrix of PDLC films. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Permeability barriers by controlled morphology of polymer blends

Melt fabricated plastic articles with improved solvent and vapor barrier properties are of great need in the packaging industry. Various techniques, such as coextrusion, surface treatments, and coatings, are being employed currently towards this objective. Present work has identified a unique polymer blend approach to impart solvent and gas barrier properties to a polyolefin material. This involves incorporation of small amounts of a modified nylon barrier material, and processing under controlled conditions, in single step blowmolding or other extrusion processes. The unusual barrier effects obtained at small concentrations of the barrier material are obtained by the controlled morphology of the dispersed phase and optimum formulation of the ingredients.     

液晶高分子原位复合材料

简介液晶高分子及其分子复合材料定义、特性和分类；重点阐述分子复合材料的研究领域和应用前景。     

Novel polymeric alcohols by controlled catalytic polymer functionalization

Novel EPDM (e thylenep ropylened iene m onomer) and polybutadiene polyols can be synthesized by a two-step process of controlled hydroformylation and then reduction of the formyl groups to place a desired amount of pendant alcohol groups along the polymer chain. The degree of functionalization can be controlled by measuring gas uptake from a calibrated reservoir during hydroformylation. Hydroformylation can be performed in solution or under simulated melt-phase conditions using either HRh(CO)(PPh₃)₃ or Rh(acac) (CO)₂ as catalysts. Reduction of the polyaldehyde by NaBH₄ generates the polymeric alcohol without further reaction of the remaining double bonds. Polymer functionalization and further modifications were followed by H-NMR and FTIR. These unique hydrophobic polyols can be reacted further to produce other polymer systems. As an example, urethanes have been made with these polyols by reaction with diisocyanates. © 1995 John Wiley & Sons, Inc.     

Compressibility of the polymer crystal

Results for the compressibilities of a wide range of polymer crystals along the fibre- and the transverse crystal axes are presented. Good agreement is found between the theoretical and the experimental results of different authors.     

Induced orientational behavior of liquid crystal polymer by carbon fibers

Experimental results are presented that show that the structure of carbon fibers induces molecular orientation of liquid crystal polymers. X-ray diffraction data are used to demonstrate final collinearity of the polymer molecular axis and carbon fiber axis independent of fabrication approaches or prefabrication orientation of the polymer relative to the carbon fiber direction. The final degree of polymer molecular orientation approximately equals the degree of carbon basal plane orientation within the carbon fiber.     

Advanced functional polymer membranes

This feature article provides a comprehensive overview on the development of polymeric membranes having advanced or novel functions in the various membrane separation processes for liquid and gaseous mixtures (gas separation, reverse osmosis, pervaporation, nanofiltration, ultrafiltration, microfiltration) and in other important applications of membranes such as biomaterials, catalysis (including fuel cell systems) or lab-on-chip technologies. Important approaches toward this aim include novel processing technologies of polymers for membranes, the synthesis of novel polymers with well-defined structure as ‘designed’ membrane materials, advanced surface functionalizations of membranes, the use of templates for creating ‘tailored’ barrier or surface structures for membranes and the preparation of composite membranes for the synergistic combination of different functions by different (mainly polymeric) materials. Self-assembly of macromolecular structures is one important concept in all of the routes outlined above. These rather diverse approaches are systematically organized and explained by using many examples from the literature and with a particular emphasis on the research of the author's group(s). The structures and functions of these advanced polymer membranes are evaluated with respect to improved or novel performance, and the potential implications of those developments for the future of membrane technology are discussed.     

Growth of sculptured polymer submicronwire assemblies by vapor deposition

We have grown helical nanowire assemblies of parylene C, thereby demonstrating that polymeric sculptured thin films (STFs) can be fabricated by a combination of physical and chemical vapor deposition processes. The deposition method is explained in detail and electron micrographs of 200-400 nm size sculptured thin film of parylene are given. The shapes of the submicron and nanowire assemblies can be engineered so that the polymeric STF acts as a template for preferential attachment of biomolecules.     

Creation of dense polymer brush layers by the controlled deposition of an amphiphilic responsive comb polymer

We introduce a copolymer with a comb topology that has been engineered to assemble in a brush configuration at an air-water interface. The molecule comprises a 6.1 kDa poly(methyl methacrylate) backbone with a statistical amount of poly[2-(dimethyl amino)ethyl methacrylate] polybase side chains averaging 2.43 per backbone. Brush layers deposited with the hydrophobic PMMA backbone adsorbed to hydrophobized silicon are stable in water even when stored at pH values less than 2.0 for over 24 h. The use of a Langmuir trough allows a simple controlled deposition of the layers at a variety of grafting densities. Depth profiling of brush layers was performed using neutron reflectometry and reveals a significant shifting of the responsiveness of the layer upon changing the grafting density. The degree of swelling of the layers at a pH value of 4 (below the pK_b) decreases as grafting density increases. Lowering the pH of the subphase during deposition causes the side chains to become charged and more hydrophilic extending to a brush-like configuration while at neutral pH the side chains lie in a “pancake” conformation at the interface.     

Laser drilling of liquid crystal polymer composite

This investigation studies the laser machining behavior of a glass fiber reinforced liquid crystalline polymer (LCP) composite by using two different types of lasers, namely; pulsed Nd:YAG and excimer. A theoretical model is established to predict the maximum depth-of-drill of the YAG laser machined holes. Moreover, the effects of the YAG laser output parameters on the geometry and the quality of the machined surface of the hole are discussed. The laser machining characteristics of the composite are compared for the two different types of lasers in terms of laser absorptivity. The results show that the glass fiber reinforced LCP has a higher absorption towards UV radiation than infrared light. Scanning electron microscopy examinations were also conducted to assess the surface quality of the machined holes. In YAG laser drilling, a high pulse energy or excessive pulses caused severe carbonization of the surface, and many cracks formed. On the other hand, excimer laser did not cause any significant carbonization of the surface; however, a large number of voids were found in the process affected zone.     

工程塑料改性及成型加工技术特集之六液晶聚合物改性及应用

就利用液晶聚合物特性的新材料开发，对高循环成型材料和流动性和机械物性同时改性的填料应用、耐热新规格聚合物的骨架、精密成型材料及其回收再生适应性作了说明。     

A study of polycarbonate-liquid crystal polymer blends

The morphology and the thermal and mechanical properties of blends of bisphenol-A polycarbonate (PC) with a wholly aromatic liquid crystal copolyester-amide (Vectra-B of Hoechst-Celanese) are discussed with reference to the conditions used for their preparation. The blends made by extrusion behave as mixtures of incompatible polymers: the dispersed liquid crystalline phase is more or less oriented in the extrusion direction and acts as a reinforcing filler for the PC matrix. The behaviour of the blends prepared in a batch mixer depends strongly on mixing time. A slight decrease in the mechanical properties (especially tensile strength and elongation) accompanies the morphological changes associated with a progressive improvement in the compatibility of the two polymers, which finally leads to an apparently homogeneous material after 45 min mixing at 290°C and 150 rpm. These effects are interpreted in terms of chemical interactions taking place between the two components of the blends.     

Metallization of a liquid crystal polymer by PVD using a nickel interlayer

In this paper metallization of a liquid crystal polymer (LCP) substrate by physical vapor deposition (PVD) is described. Pretreatment of LCP substrates with oxygen-containing plasma improves the adhesion strength between the PVD copper layer and substrate. When a nickel interlayer was used, the adhesion was improved further. Still higher adhesion was also achieved with appropriate bias used during deposition of the nickel interlayer by PVD. Even after 1000 cycles of thermal shock the adhesion strength of Cu/Ni on LCP pretreated with oxygen plasma was still high.     

晶须增强聚合物及硫酸钙晶须／聚合物复合材料

总结了晶须增强聚合物的优势,并指出了晶须增强聚合物在性能、工艺和价格上存在的问题。对晶须增强聚合物的发展提出了建议。介绍了价廉质优并已国产化的ＣａＳＯ４晶须的性能以及ＣａＳＯ４晶须在聚合物中的应用。     

功能性聚合物基纳米复合材料

纳米复合材料是指分散相大小为纳米级（一般为1~100 rim）粒子均匀分散于基体中,可发挥各组元材料的优点,克服单一组元的缺陷,具有某种特殊性能或良好综合性能的材料。对聚合物基纳米复合材料研究现状进行了概述,并对其分类、应用、性能等方面的国内外研究进展进行了全面综述。     

Preparation of calcium sulfate dihydrate and calcium sulfate hemihydrate with controllable crystal morphology by using ethanol additive

Calcium sulfate hemihydrate (CSH) with controlled crystal morphology has attracted broad interests due to its superior physical and chemical properties, as well as excellent biological performance. In this study, calcium sulfate dehydrate (CSD) was firstly synthesized via the reaction of H₂SO₄ and Ca(OH)₂ using ethanol as morphology modifier. The prepared CSD was then converted to CSH through a hydrothermal method. It was found that the precipitation time of CSD powders was dramatically shortened and the morphology of CSD crystals was changed from thick tabular to short-rod with the increment in ethanol addition. The finally-obtained CSH crystals were found to have hexagonal prisms shape with smaller aspect ratios. The CSH powder with the desired crystal morphology would provide improved setting behavior and biological performance of the CSH bone cement.     

六水合二硼酸钙晶体合成的新方法

在pH≥11、常压和95 ℃条件下,以硼砂、氧化钙和水为原料合成硼酸钙和偏硼酸钠.待反应完全后,向体系中加入氯化钙,使生成的偏硼酸钠转化为硼酸钙.反应后的混合溶液在19～22 ℃下放置17 h,即可制备出大量的六水合二硼酸钙晶体.考察了硼砂、氧化钙、氯化钙和水的物质的量比、反应所需的最佳时间和放置的最佳温度.实验采用FT-IR,TG-DTA,XRD对六水合二硼酸钙晶体进行分析.结果表明,硼砂被完全利用,过量的氯化钙很容易从产品中除掉,合成的硼酸钙晶体纯度在98%以上,晶体合成速度提高十多倍.     

Accurate determination of calcium stearate by atomic absorption spectrophotometric method in polymer

In this study, an atomic absorption spectrophotometric method is presented for the determination of calcium stearate in polymer samples after their pyrolysis. Samples of polymers were burned in an electrical furnace at 500°C. After thermal degradation of polymeric matrix, 1M HCl solution was added to dissolve the residue. Then the absorbance of solution was measured by an atomic absorption spectrophotometer at calcium atomic line. This method has an extent linear dynamic range (0.4–50 mg/L) with a limit of detection (LOD) 0.1 mg/L in solution. LOD of the proposed method in polymer sample using 0.5 g sample size is 15 ppm as calcium stearate. Some effective parameters such as time and temperature of pyrolysis and concentration of hydrochloric acid were studied. Finally, this method was successfully applied for the determination of calcium stearate content of standard and real polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Recent advances in polymer colloidal crystal lasers

Colloids with a size in the nanometres to micrometres range are frequently used in both fundamental research and industrial applications. In this context, colloidal crystals (CCs)-3D ordered arrays of monodispersed colloidal microparticles with a diameter of several hundred nanometres-have garnered a great deal of attention in the intriguing research realm of photonic crystals (PCs) due to the feasible and high-throughput 3D-PC fabrication with CCs. For optoelectronic applications, it is of prime importance to construct 3D-PCs with photonic band-gaps (PBGs) in the visible wavelength range. With regard to photonic device applications, many reports have been made on a wide variety of optical reflection sensors and displays using CCs that shift the visible PBG wavelength in response to external stimuli. This Minireview describes the research progress in the investigation of CCs and their laser applications. We highlight not only the research background of CCs as 3D-PCs, but also new potential applications of CCs as flexible and widely tunable lasers by low-threshold optical excitation.