含氟液晶新动向

本文对含氟液晶的研究动态、液晶的市场动向、ＳＴＮ液晶材料、ＴＦＴ液晶材料、ＦＬＣ液晶、ＡＦＬＣ液晶的研究进展作了报道，并指出了含氟液晶的研究方向。     

主链液晶聚硅（氧）烷的液晶行为

综述了主链液晶聚硅烷和主链液晶聚硅氧烷（包括线型、环型和梯形结构）的热致和溶致液晶行为，指出主链液晶聚硅（氧）烷具有较稳定的热致液性能，其液晶相态温度范围最宽可达３７５℃，且多数在室温下 柱状液晶相态。带有表面活性苈团例链的线型聚硅烷以水为溶剂时，可形成溶致液晶，其呈现液晶行为的临界浓度约为３０％。液晶聚硅（氧）烷所具有的液晶行为膜使其成为一种新型的功能性硅橡胶。     

液晶弹性体的研究进展

本文综述了液晶弹性体的最新进展,主要是主链型液晶弹性体、侧链型液晶弹性体以及混合型液晶弹性体的取向性、压电性、铁电性与软弹性等性质,并阐述了液晶弹性体在传感器、驱动器以及仿生机械领域的研究成果与应用前景。     

热致规则全芳液晶聚酯酰胺的合成和液晶相转变

本工作采用含酯键的全芳复合二酰氯在 NMP-LiC1 溶剂体系中,分别和 H_2N 进行低温溶液缩聚反应,合成了五种全芳规则聚酯酰胺:PEA-Ar-SO_2、PEA-Ar-M、PEA-Ar-P、PEA-Ar-OHP、PEA-Ar-MeOP。用 DSC 和偏光显微镜研究了这五种 PEA 的热致液晶行为,发现只有 PEA-Ar-MeOP 具有热致液晶特性,其 T_m=330℃,T_d=415℃。由于刚性单元空间构型的非线性,PEA-Ar-SO_2不具备热致液晶特性。而 PEA-Ar-M、PEA-Ar-P、PEA-Ar-OHP 三种聚合物的 T_m>T_d,同样不具备热致液晶的相转变特性。     

第二代超级工程塑料—液晶聚合物

本文综述第二代超级工程塑料,即液晶聚合物(LCP)的发展近况。同时,也报道了LCP的机械及高温等性能,并对其应用情况作了简要介绍。     

液晶聚合物及其应用

一概述液晶聚合物(Liquid Crystal Polyme简称为LCP)是八十年代发展起来的新型聚合物材料,由于它具有优良的耐热性、耐老化性、阻燃性、耐磨性、电性能和机械加工性能,而受到世界各国的关注并竞相开发研制。 1984年,美国Dartco Mfg公司第一个市售了热致液晶聚合物Xydar,其生产能力为1万吨/年。Xydar是由对苯二甲酸、对羟基苯甲酸和4,4-联苯二酚等三种单体制得的共聚芳酯,其热变形温度为354℃,拉伸强度是钢的15倍,缺口冲击强度为208J/m,在50℃的20％硫酸中浸泡1个月和在98％     

液晶聚合物

液晶聚合物简称LCP,由刚性的杆形有序分子构成,这些分子即使在熔化时也保持晶态次序。按照分子的定向情况,液晶聚合物可分为向列相型(晶体定向相同但次序却是任意的)和层列相型(晶体定向相同并在不同的层次上)两种,其中向列相型的液晶聚合物作为高性能的热塑性材料的潜力非常     

液晶聚酯的液晶行为与加工性能

液晶聚酯由于具有特异的液晶行为和高强高模性能而越来越受到人们的关注。本文对液晶聚酯的液晶态形成原因、液晶态类型与链结构的关系、液晶态热稳定性及其成型加工性能进行了讨论，指出了提高液晶态热稳定性的方法及液晶聚酯的发展趋势。     

UP/GF/TLCP原位混杂复合材料的性能研究

采用自行合成的双键液晶聚合物（TLCP），通过原位复合的方法制备了不饱和聚酯（UP）／玻璃纤维（GF）／TLCP原位混杂复合材料。研究了TLCP用量对UP／GF／TLCP复合材料的磨损性能、流变性能和材料表面电阻和体积电阻的影响。结果表明，TLCP用量对材料的流变性能、磨损性能和吸水性能有较大影响，当加入质量分数为5％的TLCP时，材料的流动性能最好，熔体体积流动速率达到0．097cm^3／s；当TLCP质量分数为7．5％时，材料的磨损量比未加TLCP的材料减少50％；随着TLCP用量的增加，材料的吸水性降低；TLCP用量对材料电性能影响不大。     

Influence of viscosity ratio on processing and morphology of thermotropic liquid crystal polymer‐reinforced poly(ethylene 2,6‐naphthalate) blends

Thermotropic liquid crystal polymer (TLCP) microfibril‐reinforced poly(ethylene 2,6‐naphthalate) (PEN) composites with various intrinsic viscosities were prepared by a melt compounding method. Polymer composites consisting of bulk cheap polyester with a small amount of expensive TLCP are of interest from a commercial perspective. The TLCP acts as a nucleating agent in the TLCP/PEN composites, enhancing the crystallization of the PEN matrix through heterogeneous nucleation. The structural viscosity index of the TLCP/PEN composites was lower than that of PEN and TLCP, which was attributed to the formation of TLCP fibrillar structures with elongated fibrils in the PEN matrix. The TLCP/PEN composites with higher intrinsic viscosity than the polymer matrix contained these elongated fibrils, and had a TLCP component with a smaller average diameter, and a narrower diameter distribution than TLCP/PEN composites with lower intrinsic viscosity. The higher intrinsic viscosity of the polymer matrix, the higher shear rate and the lower viscosity ratio of TLCP to PEN can all favour TLCP fibrillation in the polymer composites. Copyright © 2006 Society of Chemical Industry     

A comparative study of thermotropic LCP and organoclay as fillers in high molecular mass polyethylene with different blending sequences

The influences of thermotropic liquid crystalline copolyester (TLCP) on viscosity reduction in high molecular mass polyethylene (HMMPE) filled with organoclay were investigated by controlling the blending sequence. The interactions between organoclay and TLCP in HMMPE create different morphologies and influence rheological properties of the clay/TLCP/HMMPE blends. When the organoclay was blended with TLCP first, large amounts of organoclay formed partially intercalated structures in TLCP, with phase separation occurring at the temperature when TLCP was in the nematic phase, corresponding an antagonistic effect which weakens viscosity reduction ability of TLCP for HMMPE. However, with first blending of TLCP with HMMPE and then adding organoclay into the blend, most of the organoclay enriched on TLCP surfaces in the blend. Such interaction prevents TLCP droplets from coalescing at high shear stresses, enlarging the processing window. A phenomenological model, originally for HMMPE/TLCP systems, was successfully adopted to predict the flow behaviors of clay/HMMPE/TLCP blends. POLYM. ENG. SCI., 50:1679–1688, 2010. © 2010 Society of Plastics Engineers     

Hierarchical structure of thermotropic liquid crystalline polymer formed in blends jointly by dynamic and thermodynamic driving forces

The hierarchical structure of thermotropic liquid crystalline polymer (TLCP), especially microfibrils with an average diameter of 30 nm has been obtained in polyamide 6 (PA6)/TLCP/glass bead (GB) ternary blends by capillary flows. Thermodynamically the different interfacial tensions between PA6 and GB, and between TLCP and GB, make the glass beads migrate to the vicinity of the TLCP melt droplets. Then the strong extensional flow field formed by the micro-rollers of these glass beads exerts strong extensional action on TLCP coils so that results in the formation of TLCP microfibrils, which are usually generated with neat TLCP melt only. The hierarchical structure of thermotropic liquid crystalline polymer (TLCP) in PA6/TLCP/GB ternary blends can enhance mechanical performance of such blends.     

Organoclay/thermotropic liquid crystalline polymer nanocomposites. Part VI: Effects of intercalated organoclay on nanocomposite morphology,thermal and rheological properties

A study of a typical intercalated structure of a thermotropic liquid crystalline polymer (TLCP) with organoclay was performed to elucidate the influence of intercalated organoclay on the TLCP molecules, especially on their liquid crystallinity, thermal and rheological properties. The intercalated structures were confirmed in TLCP and organoclay formed molecular interactions with TLCP molecules in the system. Such intercalated structures caused the glass transition temperature of the nanocomposite to become invisible in thermal measurement and also caused loss of liquid crystallinity. The TLCP molecules inside the organoclay galleries showed higher thermal stability and transition temperatures, but the orderly structure of the TLCP molecules outside the galleries was destroyed by the organoclay, causing the TLCP to display lower thermal stability and transition temperatures than pristine TLCP. At 185°C, where TLCP is in the nematic phase, the nanocomposite had three orders of magnitude higher viscosity in the linear viscoelastic region than that of TLCP, with chain mobility and relaxation time slowed due to the intercalated effects in the nanocomposite. Steady shear altered the domain sizes and oriented the highly anisotropic organoclay layers or tactoids along the shear direction.     

Shear-induced interactions in blends of HMMPE containing a small amount of thermotropic copolyester HBA/HQ/SA

Shear-induced interactions between high molecular mass polyethylene (HMMPE) melt and a thermotropic liquid crystalline copolyester, HBA/HQ/SA (TLCP) were investigated using large amplitude oscillatory shear and capillary shear. Polarized optical microscopy (POM) observations show that the mono-domain nematic TLCP droplets embedded inside a HMMPE melt may be readily elongated using large amplitude oscillatory shear. The HMMPE melt adjacent to the elongated TLCP filament was observed to crystallize faster than that in the matrix away from the interface. TEM analysis on the 1 wt% TLCP/HMMPE blend quenched after capillary shear shows that there are strong interfacial interactions between the elongated TLCP filament and the HMMPE matrix. Long range PE lamellae orientational order up to 2 μm away from the TLCP filament surface were observed, with all the lamellae surface normal parallel to the TLCP fiber. Additionally, a strong interfacial compatibility between the TLCP filament and the HMMPE matrix with an interfacial thickness of ∼30 nm has also been observed. The enhanced interfacial compatibility is attributed to the -CH₂- group interactions due to chain alignment in both components at their interface. These results provide a fundamental insight to other TLCP containing thermoplastics where compatibilities may be present due to segmental interactions.     

Morphology evolution of a thermotropic liquid‐crystalline polymer in a polyamide 6,6 matrix regulated by graphene

A two‐step process, thermotropic liquid‐crystalline polymer (TLCP) premixing with reduced graphene oxide (RGO) followed by blending with polyamide 6,6 (PA66), was used to prepare ternary TLCP/RGO/PA66 blends. The rheological behaviors, morphology, and mechanical properties of the blends were investigated. The results show that RGO migrated from the TLCP phase to the interface between the TLCP and PA66 phase during melt blending; this was due to a similar affinity of the RGO nanosheets to both component polymers. The dimensions of the dispersive TLCP domains were markedly reduced with the mounting RGO content; this revealed a good compatibilization effect of RGO on the immiscible polymers. The hierarchical structures of the TLCP fibrils were found in both the unfilled TLCP/PA66 blends and TLCP/RGO/PA66 blends. This supposedly resulted from the extensional and torsional action of unstable capillary flow. With the addition of RGO, the viscosities of the blends decreased further, and the fibrillation of TLCP and the mechanical performance of TLCP composites were both enhanced. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43735.     

Fabrication of High Performance PET/TLCP Fibers through the Synergistic Interfacial Enhancement and Compatibilization of Functional 1D and 2D Carbon Nanomaterials

The maleic anhydride functionalized graphene oxide (GO-MA) is fabricated by an efficient and solvent-free Diels–Alder reaction. Polyethylene terephthalate (PET)/thermotropic liquid crystal polyester (TLCP), PET/TLCP/GO-MA, PET/TLCP/aminated multi-walled carbon nanotubes (MWCNTs-NH₂), and PET/TLCP/GO-MA/MWCNTs-NH₂ composite fibers are systematically melt-spun. The structure and compatibilizing effects of GO-MA and MWCNTs-NH₂ on the mechanical, thermal, and crystallization properties of the composite fibers are indicated. The non-isothermal crystallization kinetics and X-ray diffraction (XRD) data show that TLCP and nanofillers can change the crystalline morphology of PET. The mechanical properties of the fibers rise with increasing TLCP content. The tensile strength 929 MPa and modulus 17.5 GPa of the fibers with 7 wt% TLCP and 0.25 wt% nanofillers (0.1 wt% GO-MA and 0.15 wt% MWCNTs-NH₂) are significantly higher than those with 7 wt% TLCP (tensile strength 622 MPa and modulus 16.1 GPa) and even higher than those with 15% TLCP (tensile strength 836 MPa, and modulus 18.0 GPa). When the GO-MA and MWCNTs-NH₂ co-exist, the anti-dripping phenomenon is improved. Therefore, the TLCP, GO, and MWCNTs synergistically strengthens the mechanical properties. This is promising for the industrial fabrication of high-strength fibers.     

Inhibited transesterification and enhanced fibrillation of TLCP by nano-SiO2 in polycarbonate matrix

Hybrid composites composed of a thermotropic liquid crystalline polymer (TLCP), nano-SiO₂ and polycarbonate (PC) were prepared by melt blending in a twin-screw extruder. Infrared spectroscopy analysis indicated that the transesterification between PC and TLCP molecules during melt blending was significantly reduced in TLCP/PC blends filled with nano-SiO₂, compared to the unfilled TLCP/PC one. Scanning electron microscopy (SEM) observation showed that better compatibility and finer TLCP dispersion were reached in the unfilled blend, which made the fibrillation of TLCP difficult in capillary flow even at high shear rate. In contrast to this, well-developed TLCP fibrils were formed by capillary flow in nano-SiO₂ filled TLCP/PC blends. By increasing the nano-SiO₂ concentration and shear rate, the fibrillation of TLCP was significantly enhanced. Thermodynamically the interfacial tension between these components and dynamically the viscosity ratio of TLCP to PC were used to investigate the mechanism of nano-SiO₂ in inhibiting the transesterification and enhancing the fibrillation of TLCP droplets in these hybrid composites.     

Carboxylated multiwall carbon nanotube-reinforced thermotropic liquid crystalline polymer nanocomposites

Thermotropic liquid crystalline polymer (TLCP) nanocomposites reinforced with carboxylated multiwall carbon nanotube (c-MWCNT) were prepared through melt compounding in a twin screw extruder. The thermal stability of TLCP/c-MWCNT nanocomposites increased with even a small amount of c-MWCNT added. The rheological properties of the TLCP/c-MWCNT nanocomposites were depended on the c-MWCNT contents. The contents of c-MWCNT have a slight effect on the complex viscosity of TLCP/c-MWCNT nanocomposites due to the high-shear thinning of TLCP. The storage modulus of TLCP/c-MWCNT nanocomposites was increased with increasing c-MWCNT content. This result can be deduced that the nanotube–nanotube interactions were more dominant, and some interconnected or network-like structures were formed in the TLCP/c-MWCNT nanocomposites. Incorporation of very small amount of c-MWCNT improved the mechanical properties of TLCP/c-MWCNT nanocomposites, and this was attributed to the reinforcement effect of c-MWCNT with high aspect ratio and their uniform dispersion through acid treatment in the TLCP matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008