TLCP/PEI共混体系的流变特性与结构关系的研究

研究了VectraA950/PEI共混体系多层次结构与共混体系动态流变特性的关系.在研究液晶高分子的动态流变特性时,引入Palierne模型对动态实验结果进行预测.结果表明,TLCP分散相在高频时偏离了球形,导致Palierne模型拟合的结果与TLCP/PEI共混体系的实验结果在高频时不吻合.这与VectraA950/PEI共混体系中多层次结构在动态流场中的流变响应有关:在频率偏高时,液晶高分子取向不能完全松弛,易于形成各向异性结构,在流场作用下,易产生大形变;由于液晶高分子液滴的回缩过程很慢,在频率偏高时,产生的大形变不易回复,所以保留了纤维结构.     

含聚碳酸酯、4-羟基苯甲酸、己二醇和1,4-苯二甲酸结构的嵌段共聚物的合成与表征

以端酰氯基团的热致液晶共聚酯ＨＴＨ ６和端酚羟基的聚碳酸酯（ＰＣ）齐聚物为原料，通过溶液缩聚法制备了含ＰＣ和ＨＴＨ ６的嵌段共聚物，并用ＩＲ、ＰＯＭ、ＤＳＣ、ＷＡＸＤ等手段对共聚物结构、热行为和结晶行为进了表征．ＤＳＣ和ＰＯＭ结果证明这些嵌段共聚物都属向列型热致性液晶．在２８０℃以下的温度范围内无相分离，而在较高温度（＞２８０℃）为两相结构．共聚物的结晶结构与ＨＴＨ ６相同，结晶度随ＨＴＨ ６含量增加而增加，结晶速度也受到ＰＣ含量的影响．     

含氧化偶氮苯介晶基元共聚醚的合成与液晶行为

以1,6-二溴己烷(A)和1,10-二溴癸烷(B)为共缩聚单体,按不同摩尔配比与4,4'-二羟基氧化偶氮苯经相转移催化共聚醚化反应,合成了一系列主链上含有氧化偶氮苯介晶基元的共聚醚,它们均有好的液晶性,其取向膜观察到条带织构,当A/B的摩尔比为1时液晶态范围最宽。     

光致变色液晶高分子研究(Ⅳ)─含苯甲酸－4－甲氧基苯酯介晶基元和偶氮苯光色基元侧链共聚硅氧烷的液晶行为

用热台偏光显微镜和DSC法研究了含苯甲酸-4-甲氧基苯酯介晶基元和偶氮苯光色基元侧链共聚硅氧烷(PSⅡ)的液晶性。将非介晶基元并入液晶均聚物PSⅡ-1,共聚物PSⅡ-2、PSⅡ-3的液晶态类型不变,PSⅡ-4仅存在近晶相,PSⅡ-5～8无双折射现象,保持共聚物液晶性的最低含介晶基元单体的极限摩尔含量为80%.在液晶共聚物中,非介晶基组分含量增加时,其T_m、ΔH_m和ΔS_m降低;非介晶组分在10mol%时,T_i、ΔH_i和ΔS_i具有最小值。     

Orientation dynamics in commercial thermotropic liquid crystalline polymers in transient shear flows

In situ X-ray scattering measurements of molecular orientation under shear are reported for two commercial thermotropic liquid crystalline polymers (TLCPs), Vectra A950® and Vectra B950®. Transient shear flow protocols (reversals, step changes, and flow cessation) are used to investigate the underlying director dynamics. Synchrotron X-ray scattering in conjunction with a high-speed area detector provides sufficient time resolution to limit the total time spent in the melt during testing, whereas a redesigned X-ray capable shear cell provides a more robust platform for working with TLCP melts at high temperatures. The transient orientation response upon flow inception or flow reversal does not provide definitive signatures of either tumbling or shear alignment. However, the observation of clear transient responses to step increases or step decreases in shear rate contrasts with expectations and experience with shear-aligning nematics and suggests that these polymers are of the tumbling class. Finally, these two polymers show opposite trends in orientation following flow cessation, which appears to correlate with the evolution of dynamic modulus during relaxation. Specifically, Vectra B shows an increase in orientation upon flow cessation, an observation that can only be rationalized by the assumption of tumbling dynamics in shear. Together with prior observations of commercial LCP melts in channel flows, these results suggest that this class of materials, as a rule, exhibits director tumbling.     

Molecular orientation in sheared molten thermotropic random copolyester

The macromolecular alignment and texture orientation in sheared thermotropic copolyester were investigated using in situ wide-angle X-ray scattering (WAXS) and polarizing optical microscopy (POM). The molecular behavior was correlated with viscoelastic properties. The polymer is a random copolyester based on 60 mol% 1,4-hydroxybenzoic acid (B) and 40 mol% ethylene terephthalate (ET) units. X-ray scattering showed that the molecular chains were aligned along the flow direction. The degree of molecular orientation, , is an increasing function of the applied shear rate. However, rheo-optics showed that shear flow could not orient the polydomain texture, i.e., neither defect stretching nor elimination of defects was observed. Instead, shear compressed the microdomains and gave rise to long-range orientation correlations. Rheology showed that the nematic melt is viscoelastic, the loss modulus G″ dominates the elastic modulus G′, and the dynamic viscosity η* is shear thinning. Moreover, the steady shear viscosity, η, also behaved shear thinning, while the first normal stress difference N ₁ remained positive. The empirical Cox–Merz rule did not hold, , within the shear rate range studied. The microscopic and rheological properties suggest that B–ET is a flow-aligning nematic polymer.     

BLENDS OF THERMOTROPIC LIQUID CRYSTALLINE POLYESTER AND POLY(ETHYLENE TEREPHTHALATE)

Two kinds of blends of thermotropic liquid crystalline polymers (LCPs) and poly(ethylene terephthalate) (PET) were prepared by solution and melt blending, respectively. Crystallization behavior of the blends was observed by differential scanning calorimetry (DSC). The LCP in both blends considerably decreased the cold crystallization temperature of PET and increased the crystallization rate in the low-temperature region, but did not show any significant effect on crystallization in the high-temperature region. Phase behavior of samples prepared by melt blending was investigated with the scanning electronic microscope (SEM). It was found that LCP/PET blends display a biphasic structure with an aromatic unit-rich phase as a dispersed domain, and a highly oriented fibrous structure was formed on the fracture surface of the blends. During the melt blending process, PET reacted with LCP through transesterification, as indicated by both DSC and SEM measurements.     

Imaging of bacteria using chromonic liquid crystals

We explored adsorption isotherms of Escherichia coli (E.coli) and Salmonella over the poly-L-lysine (PLL) coated glass surface. The detection of the adsorbed bacteria was explored using 14 wt% di-sodium-chromo-glycate (DSCG) solution in water and 5CB. The textures of the optical cells made up of LCs and the adsorbed bacteria over PLL-coated glass substrate were obtained by using a polarized microscope in the transmission mode under crossed polars. We found that DSCG solution exhibits a dark spot on the adsorbed E.coli and Salmonella. In contrast to DSCG solution, 5CB did not show any dark spot.     

一类含萘环结构的聚酯酰亚胺液晶聚合物的结构与性能研究

利用Higashi芳香聚酯直接缩聚法的原理,采用分步投料的方法,以N,N′-1,6-亚己基-双苯偏三酸酰亚胺二酸(IA6)、6-羟基-乙-萘甲酸(HNA)和4,4′-二羟基二苯酮(DHBP)为单体原料,合成了一系列聚酯酰亚胺共聚物.用核磁共振(NMR)、差热分析(DSC)、偏光显微镜(PLM)、广角X射线衍射(WAXD)、热重分析(TGA)等手段对所合成的聚酯酰亚胺的液晶行为、结构以及热性能进行了表征.研究结果表明,当HNA投料量占单体总投料量高于33mol%时,所得聚合物均呈明显的向列型热致液晶特性.但是,此类液晶聚合物仅在升温过程中出现液晶的相转变,而在降温过程中并未观察到液晶的相转变行为.由DSC结果分析可知,此类聚合物具有较高的玻璃化转变温度(Tg)和较低的熔融温度(Tm),有望成为一类既具有较低加工温度又有较高使用温度的液晶聚合物材料.     

STUDY ON THE EFFECTS OF TLCP ON PYROLYSIS OF PET AND ITS RETARDANT MECHANISM

The flame retardancy of aromatic thermotropic liquid crystal phosphorus-containing copolyester,TLCP,on PET was investigated.The results show that the presence of TLCP promotes char formation of the substrate and enhances thermal stability of char,hence delay its decomposition.SEM pictures show that the char formed from PET/TLCP is more compact, therefore is more resistant to fire and heat than that from pure PET.Evolved gas analysis by I.R measurements indicates that TLCP would decompose to produce phosp...