Phase Behavior and Rheological Properties of Concentrated Lecithin Aqueous Solutions with Additives

The phase behavior and rheological properties of the concentrated lecithin aqueous solutions were investigated at 37°C. When adding Isopropyl myristate (IPM) to lecithin solutions, besides an anisotropic liquid crystal (LC) phase, an isotropic liquid (L₂) region and an isotropic viscous (I) phase are found. By continuously adding Brij 97, the LC region shifts towards higher water content and the L₂ region is extended to the area of lower IPM concentration, meanwhile the I phase disappears. By analyzing the shear rate (η_γ=0.1) and yield stress (σ₀), adding IPM to lecithin solutions increases the values of η_γ=0.1 and σ₀, and after further adding Brij 97, the η_γ=0.1 and σ₀ decrease dramatically. Notably, different from the lecithin/DDAB/water system studied by Youssry and Montalvo, in lecithin/Brij 97/IPM/H₂O system, at the relatively higher water content area of the LC phase, the water content has little effect on the critical stress. It is also found that the change of dynamic storage modulus (G′) is similar with that of η_γ=0.1 and σ₀ parameters when adding IPM and Brij 97. Maxwell model fitting results show that in the LC phase, the relaxation of the water molecule is prolonged by adding IPM and Brij 97 to lecithin solutions.     

Lamellar Liquid Crystals Formed in Ternary DEP/Oil/Water Systems

Lamellar liquid crystals of the nonionic surfactant dodecyl polyoxyethylene (4) polyoxypropylene (5) ether (DEP) were investigated by means of phase diagram and rheological technique at 25°C in the presence of different solvents. The aqueous medium includes pure water, physiological saline and 20% sucrose solution, and the oil phase includes isopropyl myristate (IPM), oleic acid, and geraniol, which are all pharmaceutically accepted chemicals. The steady and dynamic rheological property analyses of the lamellar liquid crystals formed in DEP/H₂O/IPM system indicate that the lamellar samples constructed by this special surfactant behave as pseudo-plastic fluid with relatively high elasticity and possess defects in their assembled structure. Also in this system, the elastic character gets decreased with increase in the water content. Furthermore, the comparison investigations show that the relatively high polar oil component increases the network strength of the lamellar phase, while increase in the polarity of water phase enhances the structure defects.     

嵌段共聚物L64在1-丁基-3-甲基咪唑四氟硼酸盐离子液体中形成的层状液晶

利用偏光显微镜(POM)、小角X射线散射(SAXS)及傅里叶变换红外(FTIR)光谱技术研究了嵌段共聚物PluronicL64(PEO13PPO30PEO13)(PEO:聚氧乙烯;PPO:聚氧丙烯)在室温离子液体1-丁基-3-甲基咪唑四氟硼酸盐[Bmim][BF4]中的聚集行为.绘制了L64/[Bmim][BF4]体系的相图,当L64浓度介于40%-65%(w,质量分数)之间时,L64可与[Bmim][BF4]形成层状液晶.SAXS结果表明,液晶层间距随L64浓度的增加而降低.温度对液晶微结构影响较大,液晶层间距随温度的升高而增大,极性头截面积则减小.并且,在一定温度范围内,升温可使体系的有序性增强.但是,随温度的进一步升高,[Bmim][BF4]与PEO链段之间的氢键被破坏,双折射现象消失,液晶有序性降低.此外,分析了层状液晶的形成机理,[Bmim][BF4]与L64分子间的氢键作用力、静电作用力以及疏溶剂力是液晶形成的驱动力.     

A Main‐Chain de Vries Smectic Liquid Crystal Polymer Prepared by Hoveyda–Grubbs Catalyst Initiated Acyclic Diene Metathesis Polymerization

A main‐chain liquid crystalline polymer has been obtained by applying a Hoveyda–Grubbs 2nd generation catalyst in acyclic diene metathesis polymerization (ADMET) of a monomer containing on one end a terminal dimethylvinylsilyl group and at the other end a terminal C C double bond. This material showed an interesting Iso‐de Vries SmA* – SmC* – Glass phase transition with a very small layer shrinkage on progressing from the SmA* phase into the SmC* phase. Will this material present a helical structure along the fiber axis in the SmC* temperature range? Several physical characterization methods including XRD, optical observation, and microtome technique have been used to investigate the internal structural organization in this liquid crystalline fiber.

     

正、负离子表面活性剂混合体系溶致液晶生成的相行为

研究了烷基(C8,C12,C14)三甲基溴化铵、烷基(C12,C14)溴化吡啶与烷基(C8,C12)硫酸钠混合体系溶致液晶形成的条件与结构的变化.在高浓度的水溶液中,随着正、负离子表面活性剂摩尔比接近于1,液晶结构由六角相过渡为层状相.表面活性剂非极性链长改变,对相行为影响显著,短碳链的正、负离子表面活性剂混合体系,在等摩尔比时,体系为层状液晶或立方液晶为主,夹杂少许沉淀.随碳链增长,两类表面活性剂间的静电吸引效果表现为生成沉淀的摩尔比例范围变宽,沉淀量增多,共存的液晶相减少,甚至消失.若只改变正离子的极性头基,季胺盐比吡啶盐与烷基硫酸盐的作用要强,形成不溶物的混合摩尔比例范围更宽.     

A New Type of Macroscopically Oriented Smectic‐A Liquid Crystal Elastomer

Smectic‐A liquid single crystal elastomers (S_A‐LSCE) are materials where the rubber elasticity of the polymer network is combined with the one‐dimensional positional long‐range order of mesogenic groups which are covalently attached to the network. In the systems investigated so far, a mechanical deformation of the network causes significant reorientation processes of the layered structure. We present a new type of S_A‐LSCE in which this structure remains unaffected on mechanical deformation both parallel and perpendicular to the director. The thermoelastic behavior, macroscopic dimensions, and stress–strain measurements parallel as well as perpendicular to the director are investigated. X‐ray studies confirm that a deformation parallel and perpendicular to the layer normal does not alter the macroscopically ordered lamellar structure with respect to the order parameter and the layer correlation length. We propose a simple picture where defects within the lamellar structure might account for these findings.

     

不同光滑度立方体氧化铁对液晶电光性能的改善

向列相液晶被广泛应用于液晶显示中,但是由于杂质的存在,会导致液晶的驱动电压变大,增加能耗。 为了降低阈值电压和饱和电压,通常向液晶中添加纳米颗粒来提高电光性能。 本文利用水热法制备了表面粗糙和光滑的两种立方体Fe₂O₃纳米颗粒,其形貌均匀,尺寸约550 nm。 将二者分别掺杂到向列相液晶E7中,结果表明,粗糙立方体Fe₂O₃/E7复合体系具有比光滑立方体Fe₂O₃/E7复合体系和向列相液晶E7更优的电光性能,且在掺杂质量分数为0.4%时,其电光性能达到最优,阈值电压和饱和电压分别降低9.9%和11.6%,对比度增大80%,响应时间降低至6.0 ms。 这归因于粗糙立方体Fe₂O₃具有足够的表面积和表面所带电荷更多,所以会更易吸附体系中的杂质离子和减弱杂质离子的屏蔽作用,从而提高了电光性能。     

Modelling the Vapor–Liquid Equilibrium of Polymer Solutions Using a Cubic Equation of State

This work presents the vapor–liquid equilibrium calculations in an isothermal flash, applied to polymer solutions, using the Peng–Robinson cubic equation of state modified by Stryjek–Vera, and the mixing rule introduced by Wong–Sandler. This rule allows combining the rigid lattice thermodynamic model of Flory–Huggins to the Peng–Robinson–Stryjek–Vera equation of state. As the Gibbs free energy must be minimum in the equilibrium state, a stochastic optimization method, the simulated annealing algorithm, was used to find out the extreme of this thermodynamic potential.     

星型液晶的合成、相行为与应用研究

通过SiCl4的Si-Cl键与偶氮苯类液晶基元末端OH的有效联接，合成了三种新的 星型液晶，利用红外光谱（IR）、核磁共振（^1H NMR)对其分子结构进行了鉴定， 利用偏光显微镜（POM）和示差扫描量热法（DSC）对 其液晶相行为进行了表征， 并对其在毛细管气相色谱分析中的应用进行了初步探讨。     

Thermoreversible Contraction and Extension of Layer Spacing in Smectic Phase of Side Chain Liquid Crystal Poly(fumarate)s

Two types of liquid crystal poly(fumarate)s having cyanobiphenyl mesogen in side chain were prepared by radical polymerization of disubstituted fumarate monomers in bulk. The mesogen is thus connected via alkyl spacer to every carbon atom in the main chain. The liquid crystalline temperature range expands with an increase in the molecular weight and with alkyl chain spacer length. The poly(fumarate)s form a smectic A_d phase whose layer spacing decreases and increases on heating and cooling, respectively. The contraction ratio is up to 15.2%. This significantly large change in the layer spacing corresponds to temperature dependence of the orientational order parameter. It may be connected to high density of the mesogen hanging from the main chain.

     

Determination of Imidazole, 4-Methylimidazole,and 2-Methylimidazole in Cigarette Additives by Ultra-High Performance Liquid Chromatography

Ultra-high performance liquid chromatography was employed for the determination of imidazole, 4-methylimidazole, and 2-methylimidazole in cigarette additives. Following solid phase extraction and filtration, the analytes were separated using isocratic elution with 5 mmol/L acetonitrile-ammonium formate (80:20, v/v) at 0.5 mL/min. The quantification of these analytes was achieved with the external standard method on a diode-array detector at 215 nm. Baseline separation was achieved within 1.3 min. The linear dynamic ranges for imidazole, 4-methylimidazole, and 2-methylimidazole were between 0.0375 and 18.0300 mg/kg. The limits of detection for the analytes were 0.0094 mg/kg. The recoveries and the relative standard deviations at fortification levels of 0.1322 mg/kg to 1.6220 mg/kg were 95.20% to 101.93% and 0.55% to 2.54%, respectively. The method offers easy operation, rapid analysis, and accurate results, and is suitable for the determination of imidazole, 4-methylimidazole, and 2-methylimidazole in cigarette additives.     

Photoactive liquid crystalline polymers: A comprehensive study of linear and hyperbranched polymers synthesized by A2B2, A2B3, A3B2, and A3B3 approaches

A series of linear and hyperbranched polyester epoxies, with varied structural parameters such as kinked structure and different dendritic architectures, were synthesized by A₂ + B₂, A₂ + B₃, A₃ + B₂, and A₃ + B₃ approaches. The structures of synthesized monomers and polymers were confirmed by Fourier transform infrared, ¹H NMR, and ¹³C NMR spectroscopic techniques. The effect of varied structural parameters on phase behavior and photoresponsive properties was investigated by using differential scanning calorimeter, thermal optical polarized microscope, UV–visible spectroscopy, photoviscosity, and refractive index studies. The transition temperatures of hyperbranched polymers were higher than that of the corresponding linear analogues. All the polymers showed nematic phase (nematic droplets) over a broad temperature range. The effect of kinked structural unit on photoresponsive property is less in both linear and hyperbranched architectures. Although the effect of architectural nature is highly considerable within the hyperbranched architectures, the polymer (HPE–33) synthesized by A₃ + B₃ approach showed highest rate of photocrosslinking, followed by HPE–I 32; HPE–T 32, and HPE–23, which were synthesized by A₃ + B₂ and A₂ + B₃ approaches, respectively. The findings in photoresponsive properties were further supported by molecular modeling studies. Substantial variation of refractive index (0.015–0.024) indicates that these polymers could be used for optical recording. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

固相萃取/高效液相色谱-串联质谱法测定罗非鱼中9种邻苯二甲酸酯

建立了罗非鱼中邻苯二甲酸二(2-甲氧基)乙酯(DMEP)、邻苯二甲酸二乙酯(DEP)、邻苯二甲酸丁基苄基酯(BBP)、邻苯二甲酸二(2-丁氧基)乙酯(DBEP)、邻苯二甲酸二戊酯(DPP)、邻苯二甲酸二(4-甲基-2-戊基)酯(BMPP)、邻苯二甲酸二己酯(DHXP)、邻苯二甲酸二(2-乙基)己酯(DEHP)、邻苯二甲酸二正辛酯(DNOP)共9种邻苯二甲酸酯(PAEs)的高效液相色谱-串联质谱测定方法。样品经乙酸乙酯提取后,经LC-Si固相萃取柱净化,以甲醇和甲酸-乙酸铵缓冲溶液为流动相,梯度洗脱,采用HPLC-MS/MS电喷雾正离子(ESI+)电离,多反应监测(MRM)模式检测,基质匹配外标法定量。9种PAEs在1.0～200.0μg.L-1范围内均具有良好的线性关系,相关系数不低于0.991 8,平均加标回收率为75%～107%,批内、批间相对标准偏差分别在1.9%～11.8%和3.6%～13.1%之间。该方法具有简单、快速、灵敏度高和定性准确等优点,满足残留分析的要求。     

鞘磷脂和神经节苷脂对磷脂酰乙醇胺混合脂超分子体系液晶态立方相Im3m和Pn3m结构影响的研究

用磷脂酰乙醇胺(DEPE)、鞘磷脂(Sphingomyeline, Sph)、神经节苷脂(Gm1)和胆固醇(Chol)模拟了生物膜超分子体系液晶态结构, 通过用小角X射线衍射(SAXD)对混合脂体系液晶态结构进行了研究, 鉴定出了两种立方相: 即Im3m(Q²²⁹)和Pn3m(Q²²⁴)结构. 实验发现, 鞘磷脂的含量对DEPE膜的结构有一定的影响, 随着鞘磷脂浓度的增加, 混合脂体系的液晶态结构发生了由Im3m(Q²²⁹)到Pn3m(Q²²⁴)的变化. 神经节苷脂(Gm1)的含量对混合脂体系的液晶态结构也有一定的影响, 当神经节苷脂(Gm1)含量达到某一临界值时, 混合脂体系的液晶态结构发生了从Im3m(Q²²⁹)到Pn3m(Q²²⁴) 的变化. 当DEPE-Shp-Gm1超分子聚集体中含有胆固醇时, 胆固醇的极性头部(—OH)与磷脂酰乙醇胺(DEPE)、鞘磷脂(Shp)、神经节苷脂(Gm1)的极性头部通过氢键相互作用形成液晶态立方相Im3m(Q²²⁹)结构, 再通过疏水/亲水相互作用形成稳定的Pn3m (Q²²⁴)结构.     

Optically Biaxial,Re‐entrant and Frustrated Mesophases in Chiral,Non‐symmetric Liquid Crystal Dimers and Binary Mixtures

Sixteen optically active, non‐symmetric dimers, in which cyanobiphenyl and salicylaldimine mesogens are interlinked by a flexible spacer, were synthesized and characterized. While the terminal chiral tail, in the form of either (R)‐2‐octyloxy or (S)‐2‐octyloxy chain attached to salicylaldimine core, was held constant, the number of methylene units in the spacer was varied from 3 to 10 affording eight pairs of (R & S) enantiomers. They were probed for their thermal properties with the aid of orthoscopy, conoscopy, differential scanning calorimetry and X‐ray powder diffraction. In addition, the binary mixture study was carried out using chiral and achiral dimers with the intensions of stabilizing optically biaxial phase/s, re‐entrant phases and important phase sequences. Notably, one of the chiral dimers as well as some mixtures exhibited a biaxial smectic A (SmA_b) phase appearing between a uniaxial SmA and a re‐entrant uniaxial SmA phases. The mesophases such as chiral nematic (N*) and frustrated phases viz., blue phases (BPs) and twist grain boundary (TGB) phases, were also found to occur in most of the dimers and mixtures. X‐ray diffraction studies revealed that the dimers possessing oxybutoxy and oxypentoxy spacers show interdigitated (SmA_d) phase where smectic periodicity is over 1.4 times the molecular length; whereas in the intercalated SmA (SmA_c) phase formed by a dimer having oxydecoxy spacer the periodicity was found to be approximately half the molecular length. The handedness of the helical structure of the N* phases formed by two enantiomers was examined with the aid of CD measurements; as expected, these enantiomers showed optical activities of equal magnitudes but with opposite signs. Overall, it appears that the chiral dimers and mixtures presented herein may serve as model systems in design and developing novel materials exhibiting the apolar SmA_b phase possessing D_2h symmetry and nematic‐type biaxiality.     

New liquid‐crystalline poly(ester amide)s: The role of nitro groups in the phase behavior

New hydrogen‐bonded liquid‐crystalline poly(ester amide)s (PEA)s were obtained from 1,4‐terephthaloyl[bis‐(3‐nitro‐N‐anthranilic acid)] (5) or 1,4‐terephthaloyl[bis‐(N‐anthranilic acid)] (6), with or without nitro groups, respectively, through the separate condensation of each with hydroquinone or dihydroxynaphthalene. The dicarboxylic monomers were synthesized from 2‐aminobenzoic acid. The phase behavior of the monomers and polymers were studied with differential scanning calorimetry, polarized light microscopy, and wide‐angle X‐ray diffraction methods. Monomer 5, containing nitro groups, exhibited a smectic liquid‐crystalline phase, whereas the texture of monomer 6 without nitro groups appeared to be nematic. The PEAs containing nitro groups exhibited polymorphism (smectic and nematic), whereas those without nitro groups exhibited only one phase transition (a nematic threaded texture). The changes occurring in the phase behavior of the polymers were explained by the introduction of nitro groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1289–1298, 2004     

超高效液相色谱-串联质谱法测定不同茶叶中草甘膦、氨甲基膦酸及草铵膦的残留

建立了超高效液相色谱-串联质谱同时快速测定不同茶叶中草甘膦、氨甲基膦酸及草铵膦的方法。样品用0.05 mol/L NaOH提取,并以HCl调节pH值,Oasis HLB小柱净化除杂,氯甲酸-9-芴基甲酯(FMOCCl)柱前衍生反应后,超高效液相色谱-串联质谱法测定。本方法在5~1000μg/L浓度范围内,不同茶叶基质中草甘膦、氨甲基膦酸、草铵膦线性关系良好(R2>0.99)。在0.1,0.4和4 mg/kg添加水平下,不同茶叶(绿茶、红茶、乌龙茶、普洱茶)中3种化合物回收率均介于72.1%~109.9%之间,相对标准偏差RSD在0.5%~9.8%之间(n=6),方法定量限(LOQ)在0.03~0.08 mg/kg之间(S/N=10)。本方法稳定,简便,灵敏,能够满足检测需求。     

非水溶液盐效应的气液色谱研究——非电解质(烃、芳烃、氯代烃、酮)+盐(Nal、NaSCN、KSCN)+碳酸丙烯酯体系

The gas-liquid chromatographic method was used to measure the activity coefficients at infinite dilution (γ_1~∞) of some nonelectrolyte solutes in salt containing solutions of propylene carbonate at 333.2 K. For examining the relationship between lgγ_1~∞ and salt concentrations, the salt effect coefficients of solutes were calculated, and the interactions of solute with salt were disscused. Furthermore, the equilibrium constant of complex interaction between chloroform with anions has been obtained.