Lyotropic Polymer Research Articles

Shear flow of liquid-crystalline polymer solutions as investigated by small-angle light-scattering techniques

(Hydroxypropyl)cellulose in water and poly(γ-benzyl L-glutamate) in m-cresol has been investigated. A comparison between the rheological and rheooptical properties shows that the physical mechanisms involved under the shear flow undergo a drastic modification at the onset of the shear thinning region at high shear rates. A new structural model, based on the defects concept, is proposed for the rheology of lyotropic polymers

Small-angle light scattering of polymer liquid crystals under shear flow

We presented some experimental results on flow small-angle light scattering (‘‘flow SALS’’) of lyotropic polymer liquid crystals which involved real-time, in situ, and simultaneous measurements of mechanical properties and small-angle light scattering (SALS) of a complex structured fluid. The flow-SALS studies were conducted under steady-state Couette flow and during relaxation process occurring after the cessation of the steady-state shear flow. We found the following universal behavior on the structure and properties for two kinds of the liquid crystal systems, i.e., poly(γ-benzyl L-glutamate) in m-cresol and hydroxypropyl cellulose in water. (i) Upon increasing shear rate γ̇, the ‘‘polydomain’’ structure gradually tends to be transformed to the essentially ‘‘monodomain’’ texture through annihilation of the disclinations. On the top of this general tendency, we found more specific characteristic of the fluid systems with γ̇, (ii) at γ̇<γ̇c, a critical shear rate above which a remarkable shear thinning occurs, the disclinations are more or less uniformly distributed in space, while at γ̇>γ̇c the disclinations are localized into domains and dispersed in the more or less uniform medium with a high degree of orientation, (iii) the relaxation after cessation of the steady state shear depends on its γ̇ before the cessation and is quite different below and above γ̇c, and (iv) the cessation from γ̇>γ̇c involves formation of the ‘‘band texture’’ during the relaxation process of the fluids.

Rheology, Phase Equilibria and Processing of Lyotropic Liquid Crystalline Polymers

Abstract The structure and rheological properties of liquid-crystalline solutions of stiff-chain and semi-stiff-chain polymers are analyzed in connection with the pecularities of their phase states. Of special importance are the observation and reasonable utilization of optimal thermodynamic conditions in combination with rheological properties in processing lyotropic polymers.

Rheology of A Lyotropic Polymer Liquid Crystal of Rodlike Polymers and Main-Chain Thermotropic Liquid-Crystalline Polymers

Abstract Dynamic viscoelastic properties of main-chain thermotropic liquid crystalline copolymers random copolyesters (PHB/PET) at different temperatures have been investigated. The form of the viscoelastic functions depends on both temperature and the composition ratio of copolymers. It was cleared that in certain temperature region, the viscoelastic behaviors for random copolyesters with optimum composition ratio were quite similar to those for a lyotropic polymer liquid crystals of PBG.

Orientability of liquid crystal polymers in elongational flow

AbstractThe orientation development in elongational flow (spinning) of liquid crystal polymers (LCP) has been studied and a physical model derived which relates the modulus development and extensional deformation. The model defines an orientability parameter, λ, which in addition to the total elongational deformation (drawdown ratio) are related to the orientation (modulus) level of the final spun fiber. Five LCPs were included in the study—a lyotropic polymer: Poly (p‐phenylene‐terephthalamide) and four wholly aromatic naphthalene‐containing polyesters. The experimental results have shown good agreement with the proposed model and indicate that λ is independent of the spinneret size and is characteristic of the orientability in elongational flow of each of the polymers investigated.

Depletion layer of a lyotropic polymer liquid crystal at the air-solution interface

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDepletion layer of a lyotropic polymer liquid crystal at the air-solution interfaceTheo OdijkCite this: Macromolecules 1987, 20, 6, 1423–1424Publication Date (Print):June 1, 1987Publication History Published online1 May 2002Published inissue 1 June 1987https://doi.org/10.1021/ma00172a047RIGHTS & PERMISSIONSArticle Views64Altmetric-Citations6LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (273 KB) Get e-Alerts Get e-Alerts

Fibres from mixtures of rigid-chain and flexible-chain polymers

In the present article we make an attempt to generalize the incomplete literature material on the characteristics of mixtures of polymers where at least one of them is a rigidchain polymer, as applicable to fibre-forming polymers and to fibres based on them. From the behavioral features of the polymer mixtures and the complex of properties acquired by the mixed fibre, it seems advisable to subdivide mixtures of flexible- and rigid-chain polymers on the basis of the ratio of the two components in them (systems with a large and with a low content of the rigid-chain polymer). Phase Equilibria in Three-Component Systems Involving a Solvent and Rigid- and FlexibleChain Polymers. PPTA and other rigid-chain polyamides are lyotropic liquid-crystalli ne (LC) substances, since they do not melt up to the decomposition point and form the LC state only in solution. Another group of fibre-forming LC polymers, mainly aromatic polyesters and polyazomethines, is characterized by a weaker intermolecular interaction due the absence of hydrogen bonds, and melts at lower temperatures; they belong to the thermotropic substances. A transition from the crystalline to the LC state is effected on the melting of these substances. Phase separation has been studied as yet only for the lyotropic polymers. As concerns mixtures involving thermotropic polymers, investigation of these is attended with large difficulties, caused by the occurrence of slow exchange reactions between the heterochain polymers in the case where they are mixed at high melt temperatures. Thereupon, apparently a physical mixture of the polymers can exist only for a short time, being transformed with the passage of time into a block-copolymer and a true statistical copolymers. The phase equilibrium state in a solution of a rigid-chain polymer with rod-like mole

Theory of lyotropic polymer liquid crystals

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTheory of lyotropic polymer liquid crystalsTheo OdijkCite this: Macromolecules 1986, 19, 9, 2313–2329Publication Date (Print):September 1, 1986Publication History Published online1 May 2002Published inissue 1 September 1986https://doi.org/10.1021/ma00163a001RIGHTS & PERMISSIONSArticle Views1846Altmetric-Citations419LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Apparatus to Measure Small-Angle Light Scattering Profiles of Polymers under Shear Flow

The apparatus and the principle to measure flow small-angle light scattering (“flow-SALS”) are presented as one of the rheo-optical techniques. The flow-SALS technique presented here enables one to investigate small-angle light scattering profiles and rheological properties of polymer solutions, liquids, and mixtures, as well as polymer liquid crystals under various types of shearing, i.e., steady-state shear flow, oscillatory shear flow, and shear recovery after the cessation of steady-state flow. This technique may be useful to investigate the flow-induced formation, dissolution, and deformation of supermolecular structure with spatial correlation length of a few microns, and also their effect on rheological properties. In order to demonstrate the prospect of its use, some preliminary results on flow-SALS from the lyotropic polymer liquid crystal [20 wt% poly(γ-methyl-d-glutamate) in m-cresol] are presented.

Measurements of the anisotropic viscous and elastic properties of lyotropic polymer nematics

We summarize the current status of our studies of the macroscopic linear mechanical properties of nematic liquid crystals formed from solutions of rigid or semirigid rod-like polymers. The polymer system we have studied is a racemic mixture of poly(benzyl glutamate) dissolved in a mixture of dioxane and methylene chloride. We have also studied nematics formed from colloidal suspensions of tobacco mosaic virus which may be viewed as an ideal model system representing a rigid-rod polymer solution. We review briefly the current theoretical understanding of the elastic and viscous parameters characterizing a nematic. Then we discuss our experiments, both Frederiks-transition studies and quasielastic Rayleigh scattering. The Frederiks transition in its well known simple forms is not easily utilized in these systems, mainly because of the intervention of a number of phenomena not normally encountered in low-molecular-weight liquid crystals. However, these phenomena have been analysed theoretically and can be used to extract information on elastic and viscous properties. Quasielastic Rayleigh scattering on well oriented single crystals has proved to be an excellent technique for measuring ratios of elastic and viscous parameters. We describe the scattering geometries we have used and our results.

Deformation Studies of Liquid Crystalline Polymers

Abstract Oriented liquid crystalline polymers exhibit a macroscopic optical effect which appears as a sequence of bright and dark bands perpendicular to the orientation direction. Although these bands appear to be similar to the Williams domains in low molecular weight liquid crystals, their interpretation must satisfy not only the optical observations but also the rheological properties of the mesophases and the high mechanical properties typically exhibited by the oriented polymer morphologies produced by processing such mesophases. In view of these criteria, we discuss the formation of band patterns in thermotropic and lyotropic polymer systems and propose that the band patterns result from the ordering of macroscopic domains.

Transmission electron microscopy study of an oriented thermotropic liquid crystalline polymer

Electron microscopy studies of fibers spun from lyotropic polymer mesophases are far more common in the literature than reports of TEM of thermotropic polymers, but recently publications have appeared reporting oriented electron diffraction patterns and “banding” in TEM images of thermotropic polyesters. Considering the advantages of fiber spinning from the melt, an understanding of the detailed morphology of thermotropic polymers, their ordering in flow fields, and the influence of quenched-in mesomorphic orientation on 3-D crystalline order is desirable. The experimental study described herein utilizes a solution casting technique to produce oriented thin films of a block polyester containing alternating rigid mesogenic and flexible spacer groups (Fig. 1a).

Mesophase formation in lyotropic polymers

The behaviour of polymers for which the mesomorphic property is primarily related to rigidity or partial rigidity of the chain backbone is discussed. The former part of the paper includes an outline of current theories, which describe the phase equilibria of both low-and high-molecular-weight mesogens in the undiluted and diluted states. In the latter part of the paper phase behaviours of rigid and semi-rigid polymers are briefly reviewed. Detailed phase diagrams are considered for the systems poly-γ-benzyl-L-glutamate/dimethylformamide and poly-p-benzamide/dimethylacetamide-LiCl. The correlations between experiments and theory are discussed. The mesomorphic behaviour of cellulose and its derivatives and ternary systems involving two rodlike solutes or mixtures of rodlike and random coiled polymers are also considered. Experimental results provide substantial confirmation for the theoretical predictions of mesophase formation in lyotropic polymers.

Banded structures in oriented thermotropic polymers

Drawn fibres and shear-oriented thin films of four thermotropic liquid crystalline polymers have been examined using polarized light optical microscopy and transmission electron microscopy. A banded structure is observed in polarized light, with the striations lying perpendicular to the fibre axis or shearing direction. This structure closely resembles those previously reported in lyotropic polymers, suggesting that the supramolecular organization implied by the banded structure is a feature characteristic of oriented liquid crystalline polymers in general.

Pretransitional effects in the isotropic phase of a lyotropic polymer liquid crystal

AbstractConsolidation of chiral orientational ordering in concentrated solutions of poly(benzylglutamates) has been investigated by polarization microscopy, measurements of birefringence and optical rotatory dispersion. A pretransitional region was examined where the temperature and concentration of polymer are held just below critical conditions for phase separation of anisotropic, liquid crystal spherulites. Optical rotations observed in this visually isotropic region are considerably in excess of those found in dilute solution of the polymer and exhibit a strong temperature dependence. This critical enhancement of optical activity is attributable to short‐range chiral ordering of the long axes of macromolecules in the isotropic phase.

Photochemical and spectroscopic behavior of some liquid-crystal polymer systems

The synthesis, characterization, and applications of liquid-crystalline polymers are emerging areas of scientific research. Lyotropic and thermotropic mesomorphic polymers are briefly reviewed, and the spectroscopic properties of solutes in liquid-crystal polymer hosts are discussed. The results of some photochemical investigations in ordered systems are described. Potential uses of liquid-crystal polymers are given.