Chain Macromolecules Research Articles

Ganglioside, protein, hexose, and sialic acid changes in the trisected optic tectum of the chick embryo

Spatiotemporal changes in membrane constituents of cells from the optic tectum of the chick embryo were analyzed during the period of maximum differentiation and synaptogenesis. Each tectum from 6-, 8-, 10-, and 12-day embryos was cut into three subregions along the topological gradient of differentiation. Electrophoretic analysis of proteins revealed an already complex population by Day 6 which remained relatively unchanged through later stages, with little if any topological variations. In contrast, chromatographic analysis of gangliosides showed an increasingly complex pattern as differentiation proceeded, with a growing preponderance of multisialogangliosides. Total membrane protein increased symmetrically with tissue mass in each subregion. However, hexose concentration and sialic acid/hexose ratios showed strikingly asymmetrical topological distributions as early as Day 8, and tended to fluctuate reversibly within brief (1 day or less) time periods. These results suggest that during the period of maximal differentiation and retino-tectal synaptogenesis in the optic tectum of the chick, the membrane protein population remains relatively stable and topologically invariant, whereas the polysaccharide chains of membrane macromolecules fluctuate according to topological position and developmental state in a complex, relatively rapid, and apparently oscillatory fashion.

Simplified solution of the Kirkwood-Riseman equations for the intrinsic viscosity of a chain macromolecule

A minor rearrangement of the Kirkwood-Riseman equations puts them in a form more suitable for solution than the standard form. Solution then involves the inversion of a single matrix of order N (where N is the number of segments) as the most difficult step. The results are exactly the same as the standard procedure, but the work is simplified. Die Gleichungen von Kirkwood und Riseman wurden gelost durch eine Umordnung, die eine viel einfachere Losung erlabut. Bei diesem nuen Verfahren mus man nureine einzige Matrize der Ordnung N invertieren (wobei N die Zhal der Kettenglieder bedeutet). Diese Umkehrung ist der schwierigste Schritt in dieser Methode. Die Resultate stimmen genau uberein mit jenen des gewohnlichen Verfahrens, aber der Aufwand ist wesentlich geringer.

Mechanical behavior of a number of polymers at helium temperatures

An experimental investigation of the mechanical behavior of a number of polymers in the range 4.2–240°K has been made. It has been shown that at helium temperature the Poisson ratio is governed by the free volume. It has been established that the dynamic Young's modulus and shear modulus of these polymers at 4.2°K depend on the chemical structure: their values are determined by the mean distance between neighboring macromolecule chains.

Synthesis and study of polyarylene phosphazenes

Polyphosphazenes containing arylene radicals in the main chain of macromolecules were obtained by ammonolysis of p-phenylene and p-xylylene-bis-tetrachlorophosphoranes with ammonium chloride under varying conditions. Similar polymers were also formed by ammonolysis of organo-bis-tetrachlorophosphoranes with liquid ammonia and subsequent deammonolysis of the product. Polyarylene phosphazenes are infusible insoluble substances and have increased heat resistance.

On the nature of polymeric liquid crystals

AbstractStarting from the theory of formation of liquid crystalline mesophases in solutions of rod‐like rigid chain macromolecules, developed by Flory and DiMarzio, the situation is analyzed where the flexibility parameter, f, which is essential in this theory, is variable and concentration dependent. It is shown that energetic factors of physical‐chemical origin expressed by the polymer‐solvent interaction parameter, χ1, and connected with the selectivity of these interactions may influence substantially f, changing its value from the supercritical ( > 0.63), when self‐organization in an ordered mesophase is impossible, to the subcritical, i.e., values down to f→ 0, when a spontaneous formation of a liquid crystalline phase occurs. In quite a similar manner (the analogy encompassing even the corresponding formulae) f is affected by external fields, as a result, in a stationary orienting field a system of flexible chain macromolecules may become equivalent to a unperturbed system of rigid chain macromolecules. The external field can also decrease the critical concentration of the formation of the liquid crystalline phase in rigid chain systems and liquidate the domain structure, thus transforming such a system into a unique “liquid single crystal”. This is shown to be true for the behavior of a rigid chain polymer polyparabenzamide in strong magnetic fields.The analysis leads to the conclusion that a purely entropic formalism for the description of the formation of extended chain liquid crystals is neither necessary nor sufficient, and purely energetic factors most certainly must be taken into account. However, following incorporation of these data, it becomes possible to reduce the formation of the ordered phase to the “entropic” mechanism of Flory‐DiMarzio.

The optico-deformation effect in irradiated polyethylene

The absorption of light by polyethylene film subjected to extension and electron bombardment has been investigated on the wavelength interval 220–800 nm. It is shown that irradiation and illumination by a xenon lamp during extension reduce the stresses corresponding to the beginning of high-elastic deformation of the polyethylene. It is established that deformation and electron bombardment lead to an increase in the light absorption of the polyethylene film with absorption maxima at 245 and 290 nm. It is assumed that the nature of the effect is associated with reorientation of the macromolecule chains under the influence of mechanical stress and the appearance of allyl radicals-CH2-CH ≡ CH-ĊH-CH2-.

Polymerization as a model chain reaction

The building of long chain macromolecules offers the best opportunity for the study of chain reactions and the free radical mechanism.

Thermooxidative stability of copolymers having polyconjugated fragments in the main chain of macromolecules

Copolymers have been synthesized which consist of polyazophenylene (1-50%) and polyisoprene (or polystyrene) fragments. Synthesized copolymers have some specific properties caused by intermolecular interaction of polyconjugated blocks. The inhibiting activity of polyazophenylene blocks of copolymers was ascertained considerably to surpass the inhibiting effect of polyazophenylene addition to corresponding homopolymers in the processes of thermal destruction and oxidation of polymers. This is reflected in the decreased rate of oxygen absorption at constant temperature, in the decreased rate of weight losses in isothermal conditions, and in the increased temperatures of 50% weight losses of copolymers by the dynamic thermogravimetric analysis. The increased inhibiting activity of polyconjugated blocks is explained by their improved compatibility and distribution in polymer substrate and by the increase of conjugation degree owing to intermolecular interaction of polyconjugated blocks.

On the stochastic approach to irreversible statistical mechanics of chain macromolecules

Expressions are given for the probability P of local configurational changes on a chain macromolecule and for the relaxation times.

The Structure of κ-Carrageenan from Gigartina Tenella

Abstract An alkaline treatment of κ-carrageenan from Gigartina tenella resulted in the change of the proportions of galactose, 3,6-anhydro-galactose and sulfate from 100 : 91 : 124 to 95 : 96 : 119. Fragmentation of the methylated polysaccharide gave 2,4,6-tri-O-, 2,6-di-O-, and mono-O-methyl-d-galactose in the molar proportions of 1 : 18 : 0.8 together with 3,6-anhydro-d-galactose and its 2-O-methyl-derivative in the molar proportion of 1 : 4. From these and other data, it is concluded that the polysaccharide is composed of the residues of 1,3-linked β-d-galactose 4-sulfate (95 mol), 1,4-linked α-d-galactose 6-sulfate (5 mol), and 1,4-linked 3,6-anhydro-α-d-galactose (67 mol) and its 2-sulfate (24 mol), and that the 1,3- and 1,4-linked residues are repeated alternatingly to form a chain macro-molecule.

Kinetics of cooperative transconformations of chain macromolecules

Measurements of the absorption of ultrasonic longitudinal waves in solutions of chain molecules are interpreted in terms of local cooperative transconformations, using a two-state kinetic model presented recently.

Mechanochemische aufpfropfung von polymeren an der oberfläche von füllstoffen als methode ihrer aktivierung

AbstractPeculiarities in the process of the mechanochemical grafting of polystyrene on freshly formed surface of particles of calcium carbonate on grinding in styrene were studied. It was established that the formation of homopolymer in this process is the result of rupture of individual chains of macromolecules, which are bound to the surface. If a small quantity of water is present in the monomer, the grafting is enhanced, due to an increase of the specific surface of the powder as a result of the reduction of its durability due to adsorption (Rehbinder effect). The grafting of polystyrene makes the solid surface hydrophobic and increases the activity of calcium carbonate as a filler for rubber.

Epitaxial crystallization of oligopeptides on alkali halide surfaces

Five oligopeptides—glycylglycine, glycyl- l-asparagine, glutathione, glycyl- l-prolyl- l-alanine, and glycyl- l-prolyl-glycyl-glycine—were crystallized epitaxially from solution on a variety of alkali halide (001) cleavage faces. Morphological observations, in conjunction with knowledge of the crystal structure of the first three compounds, have enabled some inferences to be drawn on molecular orientations upon the substrate surface. Comparisons have been made between the epitaxial crystallization of these oligopeptides and the oriented overgrowths formed by chain macromolecules on the same surfaces. From these studies it can be shown that some di-, tri-, and tetrapeptides, which are representative of important amino acid sequences in collagen, exhibit a specific and positive mode of association on a mineral surface.

Conformational properties of polymer molecules with side chains. Polycetylmethacrylate (PCMA)

TH~ size and structure of the lateral groups of macromolecular chains is known to affect the conformation and optical properties of the latter [1]. A sufficient increase of the lateral monomer radical at the same degree of polymerization makes it possible to observe some enlargement of the molecular coil dimensions in solution; this can be attr ibuted to a larger equilibrium rigidity of its main chain. The optical anisotropy of the polymer molecule is particularly sensitive to structural changes of the group in the side chain. The simultaneous study of the hydrodynamic and optical properties of molecular chains having branches of different length can therefore give some information about the effect of the latter on the rigidity of the main as well as the lateral chains of macromolecules [2-4, 20-26]. Systematic investigations in this direction were made only in the series of polymethacrylic acid esters. Promising dimensional data on molecules were obtained for up to polyarylmethacrylate [5-7], while the optical anisotropy was determined only for the lower homologues, including the oetyl ester [8, 9]. One of the articles [10] on asymmetrical light scattering gave the dimensions of PCMA maeromolecules in heptane. The polymers used in this s tudy had relatively low mol.wt., which makes the reliability of the results rather doubtful. Also, of greatest interest are the conformation properties of the polymer representing the alkyl methacrylate series, which has the longest groups in the branch. Sedimentation and diffusion analysis, coupled with flow birefringence, were used in this s tudy of the conformation and optical properties of PCMA fractions.

Calibration of gel permeation chromatographic columns for measuring the molecular size of poly(vinyl chloride) in tetrahydrofuran

AbstractA calibration plot of the intrinsic viscosities of poly(vinyl chloride) fractions against elution volumes gives a good correlation between the first moments, i.e., mean elution volumes, and intrinsic viscosities of poly(vinyl chloride) whole polymers. This is evidence that column permeation of chain macromolecules is governed by some sort of hydrodynamic size in a manner akin to that in which hydrodynamic size affects capillary viscosity measurements.

Polymers with a system of conjugation

1. The thermal and catalytic polymerization of phenoxyacetylene was studied; moreover, the influence of the nature, ratio, and concentration of the catalysts and the temperature upon the yield and properties of the polymers was investigated. 2. In the thermal polymerization of phenoxyacetylene, polymers are formed with an average molecular weight up to 2700, whereas in the case of polymerization on the catalyst (C2H5)3A1-TiCl4, polymers with average molecular weight up to 4700 are produced. 3. Polyphenoxy acetylenes possess comparatively high reactivity in electrophilic addition reactions. All the polymers exhibit an EPR signal (concentration 1017 PP/g) and possess an electric conductivity of 10−11−10−14 Ω−1·cm−1. 4. At the temperature 200°, the polymers lose from 25 to 40% phenol, forming insoluble three dimensional products. 5. On the basis of the differences detected in the IR spectra of polyphenoxyacetylene (1660, 1620 cm−1), in comparison with polyphenylacetylene, it was hypothesized that there is a polyene structure in the basic chain of the macromolecule. 6. A relationship of the structure of acetylene derivatives to their ability for polymerization and the properties of the polymers was established.

Investigation of thermal and thermooxidative degradation of polyarylates

A study of aging processes of polyarylates at low degrees of conversion revealed that crosslinking predominates during both thermal and thermooxidative processes. To evaluate the degree of crosslinking during the aging of polyarylates, calculation of the density of the polymer network has been carried out for the insoluble fraction of polymers according to Flory. An increase in temperature results in a regular increase of cross-linkages. Polymer Ph-2, however, loses the ability to swell at a greater rate than D-9. The effect of oxygen on the amount of crosslinking is insignificant. The molecular weight has been found to increase in the temperature range of 250–275°C., this phenomenon is a result of branching as consequence of degradation processes. An increase of the temperature to 300–350°C. results in formation of insoluble structures. At 250–350°C. both crosslinking and cleavage of the macromolecule chain occur. Formation of three-dimensional structures has also been proved by calculation of crosslinking and cleavage probabilities. Polyarylate Ph-2 undergoes crosslinking to a higher degree. This is due to the peculiarity of its composition, in that its side substituent contains the easily broken lactone ring. The presence of this substituent increases the probability of crosslinking; this is well confirmed by other data obtained by us.

Nuclear Magnetic Relaxation of Polymer Solutions. Side-Chain Motion

In this paper, the magnetic relaxation of nuclei of spin ½ which are attached to polymer molecules is calculated. The computation is based on the idea that the relaxation process is a consequence of magneticdipole interaction between spins attached to the same segment. The particular point of this paper is to treat the relaxation as a consequence of the relative motion of the spins with respect to the polymer segment to which they are attached. The polymer segment, itself, undergoes a complicated Brownian motion which has been analyzed in a previous paper in terms of the Zimm—Rouse model of chain macromolecules.

Nuclear Magnetic Relaxation of Polymer Solutions

A theory of nuclear magnetic relaxation of solutions of chain macromolecules is presented. The relaxation takes place because of the relative motion of segments of the polymer chain containing magnetic nuclei. The analysis is based on the Brownian motion of isolated polymer molecules using a model which has been applied previously for dynamic viscoelasticity and dielectric relaxation of polymer solutions. The relative motion of magnetic nuclei may be considered as arising from three sources: (a) the relative motion of pairs of atoms rigidly attached to a chain segment, (b) the relative motion of chain segments, and (c) the motion of atoms relative to a chain segment to which they are attached. Cases (a) and (b) are treated here.

Dependence of the Zero Shear Melt Viscosity and the Related Friction Coefficient and Critical Chain Length on Measurable Characteristics of Chain Polymers

Available η—Z—T data for a wide variety of well defined linear and branched polymers and polymer—diluent mixtures are well represented by the single equation η=4.8×108(X/4.7×10—15)αζ , α=3.4 for X≥4.7×10—15, α=1.0 for X≤4.7×10—15. Here X=(〈s02〉Av/va)φ1, where 〈s02〉Av is the unperturbed mean-square radius of gyration of the macromolecule, va the volume per chain atom, and φ1 the volume fraction of polymer; values of the friction factor per chain atom ζ, computed from viscosity data by this equation, agree with independently determined values in the literature. This result confirms Bueche's theory for the viscosity of short chains and supports his theory for the viscosity of long chain macromolecules. An attempt to reduce ζ-T data for different systems to a single curve by introduction into the WLF equation of the term E/RT, where E may be related to the rotational barriers within the chain, is also presented.