Spatiotemporal Control of Enzyme‐Induced Crystallization Under Lyotropic Liquid Crystal Nanoconfinement

Water nanoconfinement has important effects on the properties of biomolecules and ultimately on their specific functions. By performing experiments and molecular dynamic simulations, we show how intrinsic nanoconfinement controls the crystallization of small organic molecules converted by enzymatic reactions within the water nanochannels of lipid cubic phases (LCPs). By controlling the nanochannel size, enzymatic reactions in LCPs can be engineered to turn the same converted substrate into its soluble, microcrystal, or needle‐like crystal form due to the large variability in water dynamics. Differential scanning calorimetry studies, supported by molecular dynamics simulations, show that most of water within the mesophase nanochannels behaves differently due to interactions with the LCP interface, and that this mechanism has a larger impact for smaller channels. These findings suggest that the amount of free water in the core of the nanochannels is the key factor determining local substrate diffusion and self‐assembly within LCPs.     

甲壳型液晶高分子的构筑、自组装及其功能化

甲壳型液晶高分子的发展很大程度上依赖于聚合物自组装的发展,而各种可设计、可预测、可调控的自组装策略的涌现,将甲壳型液晶高分子研究推向前所未有的高度,同时也极大地丰富了高分子化学与物理的内容,提升了研究水准.研究表明,侧链"甲壳效应"在调控甲壳型液晶高分子有序结构等方面有着重要作用.本综述从甲壳型液晶高分子设计合成、液晶相态调控、嵌段共聚物自组装和功能化应用等方面,总结和评述了近年来该领域国内的最新研究进展.最后,本综述总结了甲壳型液晶高分子在发展中所面临的主要问题,并对其发展趋势进行了展望.     

液晶聚合物的单层与Langmuir-Blodgett膜

系统研究了手性液晶聚硅氧烷和光致变色液晶聚硅氧烷两个毓的侧链液晶聚合物在空气/水界面的单层行为和Langmuir-Blodgett(LB)膜沉积特性,对LB膜结构与存在的聚集现象进行了系统的表征,并初步探讨了LB膜中液晶聚合物表现的功能性。     

Liquid Crystal Polymers: Overview of Characteristics and Applications in Communication and Biomedical Technologies

Russian Journal of Applied Chemistry - Liquid crystals polymers (LCPs) are aromatic polymers with unique properties which enable their usage in various applications. LCPs are herein discussed, in...     

Chiral liquid crystalline polymers: Recent issues and perspectives

The syntheses and structures of chiral liquid crystalline polymers (LCPs) are briefly reviewed with emphasis on the established structure-property correlations. The most recent advances and future trends in their potential applications in optics and electrooptics are also outlined, with particular reference to the ferroelectric, electroclinic, piezoelectric, and nonlinear optical properties of chiral LCPs.     

Stimuli‐Responsive Lipidic Cubic Phase: Triggered Release and Sequestration of Guest Molecules

New stimuli‐responsive nanomaterials, made up of host–guest lipidic cubic phases (LCPs) are presented. These biocompatible, stable, transparent and water‐insoluble LCPs are composed of monoolein (MO) as a neutral host, and small amounts of one of three judiciously designed and synthesized designer lipids as guest that preserve the structure and stability of LCPs, but render them specific functionalities. Efficient pH‐ and light‐induced binding, release and sequestration of hydrophilic dyes are demonstrated. Significantly, these processes can be performed sequentially, thereby achieving both temporal and dosage control, opening up the possibility of using such LCPs as effective carriers to be used in drug delivery applications. Specifically, because of the inherent optical transparency and molecular isotropy of LCPs they can be envisaged as light‐induced drug carriers in ophthalmology. The results presented here demonstrate the potential of molecular design in creating new functional materials with predicted operating mode.     

Infrared spectra of unsaturated organosilicon compounds with a pent a methyldisilyl group

Summary Consideration of the IR spectra of a number of alkenylsilanes with a pentamethyldistlyl group shows that substitution of a methyl radical in the trimethylsilyl group of the alkenylsilane for the (CH₃)₃Si group results in a noticeable lowering of the intensity of the absorption band for the double bond of the alkenylsilane.     

Phase Behavior of a Designed Cyclopropyl Analogue of Monoolein: Implications for Low‐Temperature Membrane Protein Crystallization

Lipidic cubic phases (LCPs) are used in areas ranging from membrane biology to biodevices. Because some membrane proteins are notoriously unstable at room temperature, and available LCPs undergo transformation to lamellar phases at low temperatures, development of stable low‐temperature LCPs for biophysical studies of membrane proteins is called for. Monodihydrosterculin (MDS) is a designer lipid based on monoolein (MO) with a configurationally restricted cyclopropyl ring replacing the olefin. Small‐angle X‐ray scattering (SAXS) analyses revealed a phase diagram for MDS lacking the high‐temperature, highly curved reverse hexagonal phase typical for MO, and extending the cubic phase boundary to lower temperature, thereby establishing the relationship between lipid molecular structure and mesophase behavior. The use of MDS as a new material for LCP‐based membrane protein crystallization at low temperature was demonstrated by crystallizing bacteriorhodopsin at 20 °C as well as 4 °C.     

液晶聚合物材料的红外光谱表征

红外光谱以高选择性、无破坏性以及高超的分辨和实时跟踪能力成为从分子水平研究液晶聚合物的的重要分析手段,而偏振二向色技术、时间分辨步扫描技术和二维相关分析技术的发展进一步提高了红外光谱分析复杂液晶聚合物的能力。本文介绍了传统傅里叶变换红外光谱及各种新型光谱分析技术（主要是二维相关技术）对液晶聚合物材料表征的研究进展,特别是对于液晶聚合物分子氢键、共聚和共混物相容性以及外场（温度、电场、光场、应力场）作用下液晶分子取向等的研究,并分别进行了具体的应用实例分析。     

A literature review on the in situ generation of reinforcing fibers

Liquid crystal polymers (LCPs) are a relatively new class of materials. These polymers usually consist of rigid rodlike molecular chains and they are capable of forming highly oriented structures even in the as-made product, with strength/modulus significantly higher than those of the conventional flexible chain polymers. Blending of LCPs with conventional polymers produces composite-like structures with LCPs serving as the reinforcing component. The properties of the blends are affected by the size, shape and distribution of the LCPs in the matrix polymer, which in turn are related to the processing conditions such as the blend composition, the extrusion and drawing conditions, the viscosity ratio of the component polymers and the type and grade of the LCPs and the matrix polymers. Improved processability of the blend due to the reduction in viscosity and the improved interfacial adhesion between reinforcing fibers and the matrix polymer are among the advantages of these materials over the conventional short fiber reinforced composites. This paper gives a brief review of the work currently available in the literature on rheology, fabrication, blend morphology and mechanical/thermal properties of the in situ composites from blends of LCPs and conventional polymers.     

Enantioselective alkenylation and phenylation catalyzed by a chiral CuF complex

A new method for CuF-catalyzed alkenylation and phenylation of aldehydes and an activated ketone using air- and moisture-stable alkenylsilanes and phenylsilane as a nucleophile is described. This methodology was extended to highly enantioselective catalytic alkenylation and phenylation using DTBM-SEGPHOS as a chiral ligand. Substrate generality is broad, and an alkenylsilane with a long alkyl chain and an internal alkenylsilane can be also used as a nucleophile. The key to success partly involves the accelerated regeneration of reactive alkenylcopper and phenylcopper through transmetalation from the silylated nucleophiles, and stabilization of the reactive copper reagents, both of which are effected by the diphosphine ligands.     

Extension-Enhanced Conductivity of Liquid Crystalline Polymer Nano-Composites

Our aim here is to predict elongational flow-induced enhancements in thermal or electrical conductivity of liquid crystal polymer (LCP) nano-composites. To do so, we combine two classical mathematical asymptotic analyses: slender longwave hydro-thermo-dynamics for fibers and exact analysis of pure elongation of LCPs in solvents for bulk phases without boundary effects; and homogenization theory for effective properties of low volume-fraction spheroidal inclusions. Two implications follow: elongational flow dominates fiber free surface and thermal effects on electrical and thermal conductivity enhancements; and, there appears to be no sacrifice in enhancements by producing much higher radius, bulk fibers.     

Retention properties of novel β-CD bonded stationary phases in reversed-phase HPLC mode

With the given special structures, the CD bonded stationary phases are expected to have complementary retention properties with conventional C18 stationary phase, which will be helpful to enhance the polar selectivity in RP mode separation. In this work, two β-cyclodextrin (β-CD) bonded stationary phases for reversed-phase HPLC, including 1, 12-dodecyldiol linked β-CD stationary phase (CD1) and olio (ethylene glycol) (OEG) linked β-CD stationary phase (CD2), have been synthesized via click chemistry. The resulting materials were characterized with FT-IR and elemental analysis, which proved the successful immobilization of ligands. The similarities and differences in retention characteristics between the CD and C18 stationary phases have been elucidated by using comparative linear solvation energy relationships (LSERs). The force related to solute McGowan volume has no significant difference, while the hydrogen bonding and dipolar interactions between solutes and CD stationary phases are stronger than between solutes and C18, which is attributed to the special structures (CD and triazole groups) of CD stationary phases. Chemical origins are interpreted by comparison between CD1 and CD2. Similar dispersive interactions of CD1 and CD2 are attributed to their similar length of spacer arms. CD2 which contains OEG spacer arm has relative weaker HBD acidity but stronger HBA basicity. CD stationary phases display no serious different methylene selectivity and higher polar selectivity than in the case of C18. Higher acid selectivity and lower basic selectivity are observed on CD2 than on CD1. Distinctive retention properties and good complementary separation selectivity to C18 make the novel CD bonded stationary phases available for more application in RPLC.     

Molecular dynamics and ordering of side chain liquid crystal polymers as studied by paramagnetic resonance

Abstract

Molecular dynamics of side chain liquid crystalline polymers (LCP) and their components were studied using the technique of paramagnetic resonance. A cigar shape spin probe (COL) and a nearly spherical spin probe (TPL) were used to study the motions and order of the LCPs. Computer simulations of the observed spectra were performed. Both rotational correlation times and order parameters were extracted from these simulations. We found that LCPs containing 30 per cent and 50 per cent of mesogenic side chains had about the same viscosity as indicated by nearly equal tumbling times at the same temperature. In addition, the LCPs motion is considerably slower than that of the monomeric liquid crystal indicating that the spacer couples the motions of the side chains to those of the main chain. Rotations about axes perpendicular to the side chain are slowed more than rotations about an axis parallel to the side chain. DSC measurements were employed to study the phase transitions. The 30 and 50 per cent LCPs displayed first order NS_A transitions, but the 50 per cent LCPs transition was much weaker, in agreement with McMillan's theory which predicts a first order transition for T _NS/T _NI>0.87 (observed ratios are 0.98, 0.90 and 0.86 for 30, 50 and 100 per cent LCPs, respectively). The 30 per cent LCP has a very short nematic range so that the nematic order, which is not saturated at the NS transition, can couple with the smectic order. This was indicated by a sharp change in slope of the order parameter versus temperature plot as the smectic is entered. The LCPs studied formed a highly ordered glass when cooled in a 1 T field. If one could find a LCP with similar ordering properties whose glass temperature is well above room temperature, then one would have a useful binder for the manufacture of haze-free polymer dispersed liquid crystal displays.     

Properties of blends containing two liquid crystalline polymers

Blends containing two, wholly aromatic, naphthalene-based liquid crystalline polymers (LCPs) are studied. Experimental results show that the viscosities of the resulting blends are lower than the parent LCPs over the entire shear-rate range investigated. The orientation development following capillary flow demonstrates, that over a defined blend composition range, some blends have higher orientability than the constituent polymers. This is further manifested in the tensile and flexural properties of injection-molded specimens. A detailed analysis indicates that in the composition range where synergistic effects are observed in orientation development as well as in mechanical properties, only one glass transition temperature is detected. This suggests that “miscibility” is desirable for obtaining maximum properties in these blend systems.     

全芳香族热致液晶聚合物与热塑性树脂聚砜的原位复合材料

用自制的四种全芳香族热致液晶聚合物ＢＰ ＬＣＰ、ＢＰＭ ＬＣＰ、ＢＰＡ ＬＣＰ、ＢＰＳ ＬＣＰ与热塑性树脂聚砜（ＰＳＦ）熔融共混，制备了一系列原位复合材料．研究了所得材料的微观形态、热性能、力学性能等，结果显示：四种液晶聚合物中，ＢＰ ＬＣＰ，ＢＰＳ ＬＣＰ在所用加工条件下可在ＰＳＦ中取向成纤，而且这两种共混物断面上存在皮 核效应；ＢＰＭ ＬＣＰ和ＢＰＡ ＬＣＰ未成纤，均以球状存在于ＰＳＦ中．这四种液晶聚合物与ＰＳＦ的相容性较差，各共混物的Ｔｇ均分别接近于二纯组分的Ｔｇ值，ＳＥＭ照片上明显的相界面也能说明以上问题．液晶聚合物对ＰＳＦ有增强作用，但增强效果不很显著，这可能是二者相容性较差所致     

Invited Lecture. Molecular order and motion in nematogens from pulsed dynamic N.M.R. A comparative study of model compounds and parent liquid-crystal polymers

Abstract

Model compounds of semiflexible liquid-crystal polymers (LCPs), specifically deuteriated at various positions of the mesogenic units and aliphatic chains, have been studied by multipulse dynamic N.M.R. techniques. Analysis of the various experiments, employing a density-matrix treatment based on the stochastic Liouville equation, provides new information about the dynamic organization of the different systems. The results, referring to monomers and dimers, are discussed in relation to the properties of the parent LCPs.

The pronounced increase in orientational order from the monomers to the dimers can be rationalized by an intramolecular order transfer via highly extended spacers, in agreement with observations for the parent LCPs. A strong dependence of the nematic order on the parity of the spacer (even-odd effect) supports this concept. However, long-range orientational order of both model compounds is completely lost upon crystallization. Thus, despite the fact that dimers already achieve unusually high order parameters in the nematic phase, many of the exceptional properties of LCPs are restricted to systems with higher molecular weights.

Molecular motions in the model compounds occur within an extremely broad dynamic range, extending from 10^?12 s (internal reorientation) in the fast-rotational to 10^?3 s (director order fluctuations) in the ultraslow-motion regime. With respect to these dynamic properties, dimers behave like conventional monomeric liquid crystals, exhibiting much faster motions than the polymers.     

Liquid Crystalline Polymers

History of Liquid Crystalline PolymersThe liquid crystalline(LC)state was first observed by Austrian botanist and chemist F.Reinitzer more than a century ago,and it was then confirmed in 1888 by German physicist O.Lehmann who named such a state of matter as"liquid crystal"in 1900.While low molecular mass(LMM)liquid crystals were successfully used in LC displays(LCDs),the development of LC polymers(LCPs)followed an independent path.Conceptually,LCPs are prepared with the incorporation of mesogenic groups that are responsible for the formation of LC mesophases,such as rod-like(calamitic)and discotic ones,into polymer chains.Depending on where the mesogens are attached,traditionally there are three major categories of LCPs.Main-chain LCPs(MCLCPs)have mesogens in the polymer backbone,while mesogens of side-chain LCPs(SCLCPs)are incorporated as side groups in a polymer with a relatively flexible main chain.In main-chain/side-chain combined LCPs(MCSCLCPs),mesogens are in both the backbone and side chains.Other classes of LCPs include mesogenjacketed LCPs(MJLCPs),dendronized LCPs,and LC networks(LCNs).     

A tensor model of liquid crystalline polymers: application to basic disclination processes

One of the features of liquid crystalline polymers (LCPs) is their strong elastic anisotropy, which means they have unequal elastic constants. Elastic anisotropy plays a crucial role in the microstructure and macroscopic properties of LCPs. In this paper, the effect of unequal elastic constants on microstructure is investigated without an external field by using a deterministic tensorial approach. In this model, the evolution of the director field can be viewed as a process driven towards the state of zero elastic torque. A tensor expression of the elastic torque is used so that the nematic symmetry is automatically conserved. In simulations of bulk samples, disclination lines of strength half and escaped integer disclinations are observed. The distortion fields around the disclinations are found to depend on elastic anisotropy. If the twist constant is the lowest, as is the case for main chain liquid crystalline polymers, the disclination lines are predominantly of the twist type.     

Supramolecular Assembly of Designed α‐Helical Polypeptide‐Based Nanostructures and Luminescent Conjugated Polyelectrolytes

Designed polypeptides with controllable folding properties are utilized as supramolecular templates for fabrication of ordered nanoscale molecular and fibrous assemblies of LCPs. The properties of the LCPs as well as the three dimensional conformation of the polypeptide‐scaffold determine how the polymers are arranged in the supramolecular construct, which highly affects the properties of the hybrid material. The ability to control the polypeptide conformation and assembly into fibers provides a promising route for tuning the optical properties of LCPs and for fabrication of complex functional supramolecules with well defined structural properties.