Rodlike Macromolecules Research Articles

Extended-chain lamellar structure and chain segregation in lyotropic liquid crystals of poly{5,7-dodecadiyne-1,12-diol bis[((4-butoxycarbonyl)methyl)urethane

The supermolecular structure of thin films of poly{5,7-dodecadiyne-1,12-diol bis[((4-butoxycarbonyl)methyl)urethane]) (P-4-BCMU), a soluble polydiacetylene, and mixtures of two P-4-BCMUs with different average lengths of molecules were investigated by means of TEM. An extended-chain lamella is observed in thin films of the polymer and mixtures. The influences of the weight fraction of a component and the difference between the average lengths of molecules on the supermolecular structure are discussed. Models describing structural features of extended-chain lamellae for the polymer and mixtures are suggested. The chain segregation according to the distribution of the extended-chain length of the rodlike macromolecules and the formation of the extended-chain lamella are discussed

Polymeric Hemiporphyrazines, a New Class of Rodlike Macromolecules Suitable for the Langmuir–Blodgett Technique

Out of the square form of the alkoxy-substituted hemiporphyrazinatogermanoxane 1 (R1 = CH3, R2 = C8H17) a new molecular architecture arises. The previously known rodlike molecules used for the LB technique all possess cylindrical symmetry.

Statistical theory and structure factor of a semidilute solution of rodlike macromolecules interacting by van der Waals forces

The second and third virial coefficients are estimated for a semidilute suspension of macromolecular rods interacting by van der Waals forces. Whenever the attractive interaction becomes strong enough to be noticeable, it is no longer quantitatively correct to adopt a second virial approximation. Nevertheless, the statistical properties of the second virial fluid are investigated because it is a very convenient idealization of strongly interacting molecular fluids. Sufficient conditions for the local thermodynamic stability of the isotropic phase are set up. The coupling of orientational with translational degrees of freedom which arises from the anisotropic van der Waals interaction between two rods is particularly manifest in the structure factor. This is calculated analytically with the help of a variational theorem.

Remarks on the association of rodlike macromolecules in dilute solution

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTRemarks on the association of rodlike macromolecules in dilute solutionPaul Van der SchootCite this: J. Phys. Chem. 1992, 96, 14, 6083–6086Publication Date (Print):July 1, 1992Publication History Published online1 May 2002Published inissue 1 July 1992https://doi.org/10.1021/j100193a079RIGHTS & PERMISSIONSArticle Views54Altmetric-Citations13LEARN 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 (562 KB) Get e-Alerts

Photochemistry and Photophysics of Nanocomposites Prepared from Rod-like Macromolecules by Lb-Technique

Abstract The design of macromolecules described as “hairy rods” proved to be most successful in the attempt to construct layered structures of optimized quality by the Langmuir—Blodgett—technique. Novel types of supramolecular architectures could be realized best described as “molecularly reinforced liquids”. First attempts to build prototype devices based on layered assemblies of these non—conventional polymers are reported. The relative orientation of the rod—like macromolecules can be changed deliberately in each layer as well as the chemical nature of the polymer such that true nanocomposites are obtained.

Structure factor of a semidilute solution of polydisperse rodlike macromolecules

The static structure factor of a semidilute solution of polydisperse rodlike macromolecules interacting via a hard core repulsion is calculated in the second virial approximation. A suitable substitution reduces the governing set of coupled integral equations to a single integral equation, which is attacked analytically by applying a variational principle. It is shown that the resulting expression for the structure factor is thermodynamically consistent. By way of example the structure factor of a bidisperse solution of rods is discussed and the marked effect of very small amounts of the higher molecular weight species demonstrated

Analysis of Depolarized Light Scattering from a Solution of Rod-Like Macromolecules Through A Laplace Transform Method

Abstract In this work, an analysis is made of the depolarized component of the light scattered by a solution of rod-like macromolecules by measuring the Laplace Transform (LT) of the time interval probability between successive photoelectrons, P(t). The study was performed in forward scattering conditions, which allows direct evaluation of the Rotational Diffusion Coefficient, Dr. Results were obtained by means of computer simulation and are compared with those obtained through the measurement of the second order correlation function, g(2)(τ), for the same experimental conditions.

The structure of the nematic–isotropic interface in polymer systems

Abstract The structure of the nematic–isotropic interfacial layer is studied theoretically for systems formed by rod-like and persistent macromolecules. It is shown that the width of interfacial layer is normally of the order of the straight part of a molecule. This allows us to use the approach which describes intermolecular interactions phenomenologically (i.e. it allows us to consider all interactions), at the same time this approach describes molecular flexibility microscopically (i.e. it allows us to study the effects of flexibility correctly). It was found, that non-monotonic gradient profiles in the surface layer of the order parameter or of the concentration of molecules as a function of the coordinate perpendicular to the interface are possible. For example, a thin layer with abnormal ordering of molecules along the surface may exist near the interface for some systems.

Gum Arabic Glycoprotein Is a Twisted Hairy Rope

Separation of the wound exudate from Acacia senegal (L.) Willd., "gum arabic," on a preparative Superose-6 column gave two major fractions: a high molecular weight gum arabic glycoprotein (GAGP) containing about 90% carbohydrate and a lower molecular weight heterogenous gum arabic polysaccharide fraction. Hydrogen fluoride-deglycosylation of GAGP gave a large ( approximately 400 residue) hydroxyproline-rich polypeptide backbone (dGAGP). Alkaline hydrolysis of GAGP showed that most of the carbohydrate was attached to the polypeptide backbone as small ( approximately 30 residue) hydroxyproline (Hyp)-polysaccharide substituents. After partial acid hydrolysis of the Hyp-polysaccharide fraction we identified O-galactosylhydroxyproline as the glycopeptide linkage, identical with that of hydroxyproline-rich arabinogalactan-proteins (AGPs). However, unlike the acidic alanine-rich AGPs, GAGP is basic and notably deficient in alanine. Thus, while the GAGP polypeptide backbone more closely resembles that of the Hyp-rich cell wall protein extensin, the GAGP polysaccharide sidechains resemble AGPs. Possibly all three proteins comprise a phylogenetically related extensin superfamily of extended rod-like macromolecules. The "wattle-blossom" model for AGP and gum arabic predicts a few large polysaccharide substituents along the polypeptide backbone of a spheroidal macromolecule. On the contrary, our data imply a rodlike molecule with numerous small polysaccharide substituents (attached to 24% of the Hyp residues), regularly arranged along a highly periodic polypeptide backbone based, hypothetically, on a 10 to 12 residue repetitive peptide motif. Thus, a simple statistical model of the gum arabic glycoprotein predicts a repeating polysaccharide-peptide subunit of about 7 kilodaltons. The small polysaccharide substituents will maximize intramolecular hydrogen bonding if aligned along the long axis of the molecule, forming in effect a twisted hairy rope. Electron micrographs of rotary shadowed GAGP molecules support that prediction and may also explain how such apparently large molecules can exit the cell by endwise reptation through the small pores of the primary cell wall.

Towards an understanding of the static structure of suspensions of ionic rod-like macromolecules

Structural properties of charged rod-like systems are analyzed in order to understand the onset of angular correlations in a concentration regime where the centres of mass separation between the rods is comparable to their elongation L. This study includes Monte Carlo simulations and first-order perturbation theories. The angular dependent correlation function g(12) and the static structure factor S M (k) are expanded in terms of rotational invariants and the first five coefficients are evaluated. In particular, from the g(220; r) coefficient, referred to a space-fixed frame, the angular ordering parameter in the system is calculated. As intermolecular potential, we use a dumb-bell model with a screened Coulomb form between two interaction centres on each rod, which includes a cylindrical hard core part to avoid overlap on increasing the rod concentration. The results of perturbation theories are obtained according to the mean potential, and reference averaged Mayer potential (RAM), the angular median pot...

Structure factor of a solution of charged rodlike macromolecules in the isotropic phase

A theory of the static and dynamical structure factor of a solution of charged rodlike polymers for the isotropic and VH-depolarized scattering was developed. The following are the major conclusions: (i) The isotopic dynamical structure factor and VH-depolarized one were given as functions of the scattering vector, delay time, rod length L and diameter B, polymer number concentration, the Debye length, and polymer charge density; (ii) The structure factor of a suspension of charged rods can be approximated with that of equivalent uncharged rods having an effective diameter b eff

Light scattering from liquid crystalline solutions of rod-like macromolecules

Light scattering from liquid crystalline solutions of rod-like macromolecules

Non-newtonian viscosity of fiber suspensions

It has been established that the introduction of fibers not only increases the viscosity of the matrix (a Newtonian liquid), but also leads to dependence of the viscosity on the shearing stress a viscosity anomaly [1-3]. At certain concentrations of monodisperse fibers and with certain viscosities of the matrix, a viscosity "superanomaly" has appeared, in which the values of the first difference of the normal stresses in simple shear were negative [4]. It was found that this phenomenon also occurs in shear flow of lyotropic liquid crystals [5]. The suspensions studied in [I] contained uniform-length fibers (s = 54.3, = 1.25 mm). Here we are presenting results from an investigation of suspensions with a variation of fiber length from one suspension to another and also mixtures of such suspensions. According to [6], molecular composites containing rigid rodlike molecules in a matrix of flexible molecular coils can be considered, at the molecular level, as analogs of composites filled with macroscopic chopped fibers. A system of randomly positioned, rigid, rodlike macromolecules in a solvent was examined in [7]. Unit volume of such a suspension contains n rigid rods with length s and diameter d; the volume fraction of fibers C = ~ns ~. For a flowing liquid suspension, the following inequalities must be fulfilled:

Toward Monodisperse Poly(γ–benzyl α,L-glutamate): Uniform, Polar, Molecular Rods

Poly(γ-benzyl α,L-glutamate) (PBLG) has been widely used in studies of the physics of rod-like polymer chains [1]. The helical structure of PBLG gives rise to considerable chain stiffness, such that the persistence length of the chain is on the order of 70 nm in helicogenic solvents [2]. This feature, coupled with the ease of synthesis and good solubility of the polymer has made PBLG the system of choice for the study of both isotropic [2,3] and liquid crystalline [4] solutions of rod-like macromolecules.

Structure factor of a semidilute solution of rodlike macromolecules

A simple variational treatment yielding a closed expression for the structure factor very close to the numerical data is proposed

Static and dynamic light scattering from liquid crystalline solutions of rodlike macromolecules

It is argued that concentration fluctuations in lyotropic nematics can cause significant scattering of light. We calculate the static structure factor numerically for a nematic suspension of rods in the second virial approximation. An analytical approximation is also given based on a variational principle applied to an integral equation of the Yvon type. The relation between the one-particle distribution function and the usual correlation functions is discussed. An expression is derived for the polarized dynamical structure factor. This yields the initial decay rate which emphasizes the diffusion perpendicular to the director. We show that the contribution from anisotropic scattering is negligible.

The phase behaviour and gelation of a rod-like polymer in solution and implications for microcellular foam morphology

The phase separation and gelation of the rod-like macromolecule, poly(γ-benzyl- l-glutamate), were studied in an effort to understand the mechanism by which microcellular materials are made via thermally induced phase separation processes. Previous workers have studied similarly prepared materials from molecules which exist as random coils in solution. The microcellular materials were formed by lowering the solution temperature until phase separation and solvent freezing occurred. The solvent was removed by vacuum sublimation. An emphasis was placed on dilute isotropic solutions (<5 wt%) which yield low-density materials or ‘foams’. Both one- (e.g. benzene) and two-component (e.g. dioxane/water) solvent systems were employed. The morphology produced by liquid-liquid phase separation and gelation was an open-celled, fibrous structure, which resembles a three-dimensional lattice. The cell diameters were in the range of 1–10 μm and the fibres which comprise the struts were 0.2 to 2.0 μm thick. Various experimental observations are discussed in terms of the theories and proposed mechanisms of phase separation in solutions of rod-like macromolecules. Calculations of the spinodal for the Flory theory of rod-like particles were also made to assess the possibility of placing the isotropic solutions into an unstable region.

The fractal nature of 1-step highly-branched rigid rodlike macromolecules and their gelled-network progenies

Highly branched aromatic polyamides characterized by stiff trifunctional branchpoints connected by rigid rodlike segment are prepared by one-step polycondensation and studied in their pregell and postgel states. It is shown that the nature of the growing one-step rigid aggregates in the pregel state is consistent with the fractal model and that because of of the branchpoint and segmental rigidity and the rather large average length of the segments between branch-points, the rigid one. Step fractals are remarkably porous on the scale of the solvent molecules

Orientation-dependent rotational diffusion coefficient of rod-like macromolecules in semi-dilute solution

The integral describing the topological interaction of rod-like macromolecules in the Doi-Edwards theory has been computed for the orientational distribution functionΨ expressed in spherical harmonics. It is shown that the orientation-dependent rotational diffusion coefficientDr may easily be calculated.

ChemInform Abstract: Stiff‐Chain Polymers ‐ Structure, Phase Behavior and Properties

Most of the industrial plastics used up to now consist of flexible macromolecules in which the repeat units are joined together in a nonlinear fashion by rotating bonds. Stiff-chain polymers, which in the ideal case have a rodlike shape, have received much less attention. The reason for this is that such polymers usually exhibit an exceedingly low solubility. Very often, they are absolutely insoluble and do not melt. However, in recent years these polymers have aroused technical interest because high-modulus fibers and moldings can be fabricated from them. These favorable mechanical properties are directly related to the nearly parallel arrangement of the rodlike macromolecules in the solid state which is achieved through spinning or extrusion from a liquid crystalline (nematic) state. It is therefore evident that a thorough understanding of the phase behavior and the structure is required for a universal technical utilization of these materials. The great variety of methods used in polymer science today has led to a deeper understanding of stiff-chain polymers. Experimental results together with theoretical modeling of the phase behavior have direct implications for the practical use of these macromolecular materials.