Showing papers on "Polymer published in 1968"

[125] Monolayer techniques in electron microscopy of nucleic acid molecules

Abstract: Publisher Summary This chapter discusses the monolayer techniques in electron microscopy of nucleic acid molecules and describes a method in which DNA or RNA of a bulk solution is transformed to a monomolecular layer. To do this, a film of protein floated onto an aqueous solution is used. Many globular proteins in solution, and similar polymers, are capable of producing surface films on an aqueous solution in a fiat trough. As the protein is surface-denatured, it forms an insoluble film. This protein film can be considered as a monomolecular layer and assumed to exist as a molecular net of unfolded polypeptide chains. The DNA or RNA is adsorbed to it by basic side groups of amino acid residues. This adsorption effectively brings a nucleic acid molecule from a three-dimensional position in an aqueous solution (the subphase) to a two-dimensional position—that is, adsorbed to the polypeptide net. After adsorption, the monolayer, consisting of the protein net and the adsorbed nucleic acid, is itself adsorbed to a solid support and then dried. The preparation can be contrasted for electron microscopy, and electron micrographs are taken. The three procedures are employed and discussed in the chapter—a spreading procedure, a diffusion procedure, and a one-step release procedure. These three procedures explains that most globular proteins have sufficient spreading activity and these proteins become surface-denatured on top of the subphase; more information is needed as to whether DNA or RNA is enveloped as a complex of protein and nucleic acid, or more likely, is nakedly adsorbed to polypeptide chains by a few adsorption side groups per unit length; and the final concentration of nucleic acids adsorbed in the diffusion procedure depends on concentration in the subphase, period of adsorption, salt concentrations, and size of the nucleic acid.

Water-soluble,ionic,glyoxylated,vinylamide,wet-strength resin and paper made therewith

Abstract: THE IONIC-HYDROPHILIC VINYLAMIDE POLYMERS WHICH HAVE SUFFICIENT -CHOHCHO SUBSTITUENTS TO BE THERMOSETTING POSSES THE PROPERTY OF PROVIDING PAPER WITH WET AND DRY STRENGTH RAPIDLY AT NEUTRAL PH, WITH OR WITHOUR EXPOSURE TO THERMOSETTING TEMPERATURES. THE PAPER RAPIDLY BECOMES A PULP SUITABLE FOR RE-USE WHEN SLURRIED IN WATER HAVING A MILDLY ALKALINE PH. BLENDS OF IONIC-HYDROPHILIC VINYLAMIDE POLYMERS AND GLYOXAL ARE STORAGE STABLE WHEN DRY, YET FORM THE ABOVE-DESCRIBED THERMOSETTING POLYMERS WHEN THEY ARE DISSOLVED IN WATER AT ROOM TEMPERATURE AND THE RESULTING SOLUTION IS AGED.

Vulcanizable silicon terminated polyurethane polymers

Abstract: A ROOM TEMPERATURE CURABLE SILICON TERMINATED ORGANIC POLYMER COMPRISING AN ISOCYANATE TERMINATED POLYURETHANE PROPOLYMER CONTAINING AT LEAST TWO URETHANE LINKAGES PER POLYMER MOLECULE, WHEREIN THE ISOCYANATE TERMINAL GROUPS HAVE BEEN REACTED WIGH AN ORGANOSILICON COMPOUND TO TERMINATE, THAT IS CAP OR ENDBLOCK SAID POLYMERS WITH ORGANOSILICON GROUPS.

The effect of carbon fibre reinforcement on the friction and wear of polymers

Abstract: Thermosetting and thermoplastic polymers have been reinforced with carbon fibres of high strength and elastic modulus, and their friction and wear properties examined. During dry sliding against steel, randomly oriented chopped fibres reduce both the coefficients of friction and the wear rates of polymers to levels which are approximately independent of the matrix material. Fibre orientation is also important, and minimum wear is obtained when the fibres are normal to the sliding surface. Carbon fibre reinforced polymers are less abrasive than those containing glass, exhibit lower friction and have greater moduli of elasticity; the flexural strengths are also often greater, and particularly so with polytetrafluoroethylene (PTFE). It is concluded that the carbon fibres reduce the friction and wear of polymers by preferentially supporting part of the applied load, and in addition by smoothing the surface of the steel counterface.

Oil-soluble interpolymers of n-vinylthiopyrrolidones

Abstract: N-Vinylthiopyrrolidone, and its lower alkyl-substituted homologs, are interpolymerized with polymerizable alkyl (Cs or greater) carboxylates and (optionally) other oxygen-containing monomers to produce oil-soluble polymers. These polymers are useful in lubricating oils as viscosity index improvers, dispersants and oxidation inhibitors.

Photopolymerization of epoxy monomers

Abstract: A PROCESS FOR POLYMERIZING EPOXY MONOMERS WHICH COMPRISES MIXING WITH EPOXY MONOMERS PHOTOSENSITIVE ARYLDIAZONIUM COMPOUNDS AND THEREAFTER SUBJECTING THE RESULTING MIXTURE TO ACTINIC RADIATION. THE ARYLDIAZONIUM COMPOUND DECOMPOSE TO PRODUCE POLYMERIZATION INITIATOR IN THE FORM OF A LEWIS ACID, THEREBY CATALYZING THE POLYMERIZATION OF THE MONOMER TO THE POLYMER. EXAMPLES OF PHOTOSENSITIVE COMPOUNDS USEFUL IN THE PROCESS ARE PNITROBENZENEDIAZONIUM HEXAFLUOROPHOSPHATE, P-N-MORPHOLINOBENZENEDIAZONIUM HEXAFLUOROARSENATE, AND 2,4-DICHLOROBENZENEDIAZONIUM HEXACHLOROANTIMONATE.

Structural studies on urethane elastomers

Abstract: A number of techniques have been used to study structural organization and transitions in polyether- and polyester-based urethane elastomers. Scanning thermal methods reveal three characteristic transitions common to samples of varying composition, namely, the major glass transition and two higher transitions believed due to disruption of different types of hydrogen bonding. Other transitions are assigned to melting of ester and of urethane crystallites. Light-scattering measurements on turbid polyether-based samples indicate both isotropic and anisotropic contributions to scattered intensity, the latter reflecting structural ordering on a small scale. X-Ray diffraction studies of stress-induced crystallization in the polyetherbased elastomer show reflections attributed to crystallites of polyether segments. It is concluded that separation into a domain structure occurs in both types of elastomers, but to a higher degree in the polyether-based polymers than in the polyester-based polymers, possib...

Infrared spectra and regular sequence lengths in isotactic polymer chains

Abstract: In order to elucidate the relationship between IR-spectra and the sequence lengths of the segments which assume the regular helical conformation in isotactic polymer chains, the IR-spectra have been measured for isotactic copolymers of normal and deuterated styrenes in various ratios. The absorption intensities of the bands characteristic of the TG skeletal conformation of the isotactic polystyrene molecule have been investigated in relation to the length of the normal styrene sequences in the copolmers. In the case of the highly crystalline samples of the copolymers, the absorption coefficients per normal styrene unit have been found to decrease with decreasing statistical sequence length of the normal styrene units in the copolymer chain. A simple statistical treatment of the intensity data has provided the critical length which is necessary to produce each characteristic band. Each band has its characteristic value of the critical length depending on the vibrational mode to which the band is due. The band intensities measured on the carbon disulfide solution at a low temperature have shown a dependence on the regular sequence length very similar to that of the highly crystalline samples. This indicates that the molecule assumes rather regular helical conformation in solution at a low temperature. An Hand der IR-Spektren verschiedener isotaktischer Copolymerer aus „normalem” Styrol und deuteriertem Styrol wurde die Frage untersucht, wie sich die Sequenzlangen von Segmenten, die in Helixkonformation vorliegen, in den IR-Spektren bemerkbar machen. Dazu wurden die Extinktionen der fur die TG-Konformation charakteristischen Banden mit den SequenzIangen des „normalen” Styrols in Beziehung gesetzt. Bei hochkristallinen Copolymeren nehmen die auf einen „normalen” Styrolgrundbaustein bezogenen Absorptionskoeffizienten ab, wenn die statistische Sequenzlange der „normalen” Styrol-Grundbausteine abnimmt. Eine einfache statistische Behandhlung der Extinktionsdaten erlaubt es, die kritischen Sequenzlangen anzugeben, die notig sind, um die verschiedenen charakteristischen Absorptionsbanden hervorzurufen; die fur jede Bande Charakteristische kritische Sequenzlange hangt von dem Schwingungsmodus ab, der sie verursacht. Die bei niedriger Temperatur in Schwefelkohlenstoff-Losung gemessenen Extinktionskoeffizienten zeigen eine Abhangigkeit von der Sequenzlange, die derjenigen bei hochkristallinen Proben sehr ahnlich ist. Dies'zeigt, das die Molekule bei niedriger Temperatur und in Losung eine ziemlich regelmasige Helixkonformation annehmen.

Oxide Glasses in Light of the “Ideal Glass” Concept: I, Ideal and Nonideal Transitions, and Departures from Ideality*

Abstract: This two-part paper develops a basis for discussing glass properties which has features in common with standard “actual vs. ideal” treatments of physicochemical behavior, by defining thermodynamically an ideal state for the glass and discussing the states of the actual glasses in terms of their “departures from ideality.” The glass transition, which freezes the state of the actual glass, is seen as the consequence of the progress of the liquid toward the ideal state, which, for kinetic reasons, is unattainable. The single complexion limit of the Gibbs-DiMarzio treatment for chain polymers and a minimum volume zero excess entropy condition related to random close packing for simple liquids are seen as complimentary descriptions of the ideal state, which also sets the thermo-dynamic low-temperature limit to the liquid state. Glasses formed from simpler molten salt and concentrated aqueous solution systems appear to approach the ideal state and thus provide a behavior pattern against which departures from ideality in the more complex silicate and borate glasses of practical interest may be assessed. In part I general aspects of the problem posed by the glass transition phenomenon are discussed, a dynamic interpretation for simple glasses in terms of the state of phonon excitation of the glassy solid is conjectured, and the concepts of ideal and nonideal (practical) glasses and glass transitions are elucidated from consideration of thermodynamic and kinetic factors involved in the volume relaxation of liquids toward the glassy state. Attention is given to units for describing departures from ideality to permit comparisons among different systems. The limited data for inorganic glasses are examined. Departures from ideality, as usually found in the physicochemical comparison of “actual” with “ideal” behavior, are attributable to specific interactions among the particles of the system, but magnitudes also depend on heat capacity changes. The former factor reaches a maximum in vitreous SiO2 which thus may be one of the least ideal of glasses.

Infrared studies of stereoregular polymerization of methyl methacrylate and methacrylonitrile by organometallic compounds

Abstract: Infrared spectra of reaction mixtures of methyl methacrylate or methacrylonitrile with an equimolar amount of organometallic compounds were investigated in relation to the stereoregulating ability of the catalysts in polymerization. It was found that the carbonyl or nitrile stretching frequency correlated with the stereoregularity of polymers prepared with the corresponding catalysts; i.e., the higher the frequency, the higher the isotacticity. From these results a mechanism of isotactic polymer formation was proposed, in which catalyst counterion was located near the carbonyl group in polymer terminal and that of monomer to be reacted, and consequently the isotactic polymerization is facilitated.

Crystallization kinetics of polymer-diluent mixtures. Influence of benzophenone on the spherulitic growth rate of isotactic polystyrene

Abstract: As an extension of earlier work on the crystallization kinetics of isotactic polystyrene, the spherulite growth rate in mixtures of isotactic polystyrene and benzophenone has been measured over a concentration range extending from pure polymer to a mixture containing about 30% benzophenone. The glass transition temperature has been measured over the entire range from pure polymer to pure benzophenone. For the mixtures the dependence of the growth rate on temperature is similar to that of the undiluted polymer. The addition of benzophenone causes a shift of the crystallization range to lower temperatures. For mixtures containing up to about 20% benzophenone, the maximum in the growth rate increases with increasing content of benzophenone. On addition of more benzophenone, the maximum rate is depressed. Taking into account the glass transition temperature of the mixtures, the influence of benzophenone on the melting point of isotactic polystyrene, and the volume fraction of polymer, we can describe the influence of benzophenone on the growth rate in a semiquantitative way.

Molecular structure and deuterium exchange in monolayers of synthetic polypeptides

Abstract: An investigation has been made of the structure and properties of synthetic polypeptide monolayers spread at the air/water interface. Two series of high molecular weight polymers have been examined, esters of polyglutamic acid and polymers with hydrocarbon side-chains. The structure has been investigated by measurement of the force/area relations and surface potentials with a Langmuir trough, and by measurement of the exchange rates of peptide deuterium. These direct methods have been supplemented by observations by infrared spectroscopy and electron diffraction on collapsed films removed from the surface. It is found that in all cases the properties of the monolayer are consistent with a structure consisting of condensed ordered arrays of $\alpha$-helices. The collapse of a monolayer to form a bilayer causes either a plateau or an inflexion in the force/area curve. From the pressure required to form the bilayer and the work of adhesion between the polymer and water, obtained from Young's equation, the free energy of the polymer/vapour interface has been calculated. The deuterium exchange measurements show that exchange can take place in an intact $\alpha$-helix, and how the exchange rate is influenced by the accessibility of the peptide group to water, the pH of the substrate and the hydrophobic nature of the side chain; the conclusions are important in the interpretation of deuterium exchange in proteins.

Time-temperature superposition and relaxational behavior in polymeric glasses

Abstract: It is shown that a free-volume treatment of the relaxational behavior of a polymer can be extended into the glassy region. A modified form of the WLF equation is derived in which the temperature is...

Graphic analysis of resin solubilities

Abstract: Positioning of organic liquids on a triangular chart in such a manner as to indicate the relative strength of three types of internal cohesive forces, (dispersive, polar and hydrogen bonding forces) has been shown to characterize quite accurately the ability of these liquids to dissolve various polymers. Having experimentally established an area of solubility for a given polymer, single liquids or mixtures can be selected with fair confidence that true solubility will result.

Polymerization of aromatic nuclei. XIII. X-ray analysis and properties of poly(p-phenylene) pellets

Abstract: X-ray diffraction experiments with poly(p-phenylene) pellets demonstrated an increase in crystallinity with increase in molding temperature or annealing temperature. The increase in crystallinity may be attributed to annealing effects and loss of chlorine under severe conditions. Lattice constants for the crystalline polymer are presented, and the crystallographic data are compared with those of the lower oligomers. Poly(p-phenylene) was investigated also in relation to oxidative thermal stability, chemical and solvent resistance, and the effect of temperature and variation in molding conditions on fracture strength. The decrease in strength at elevated temperatures appears to be related to the increase in crystallinity.

A viscometric technique for determining the layer thickness of polymer adsorbed on titanium dioxide

Abstract: A simple viscometric method for measuring the adsorbed layer thickness of polymers on nonspherical particles is proposed. With the use of viscosities at infinite shear rate the effects of flocculation are eliminated and an empirical equation relating phase volume with viscosity is obtained. By use of this equation immobilized polymer thicknesses at the solid/liquid interface have been calculated and related to polymer structure.

Water dispersible nonwoven fabric

Abstract: A WATER DISPERSIBLE NONWOVEN FABRIC COMPRISING A LAYER OF OVERLAPPING, INTERSECTING FIBERS BONDED WITH A WATER INSOLUBLE, SUBSTANTIALLY WATER INSENSITIVE, FILM-FORMING, NONSELF-CROSSLINKING POLYMER CONTAINING A WATER SOLUBLE MATERIAL HAVING PSEUDO-PLASTIC FLOW PROPERTIES UNIFORMLY DISTRIBUTED THROUGHOUT THE POLYMER.

Surface treatment of polymers. II. Effectiveness of fluorination as a surface treatment for polyethylene

Abstract: An effective surface treatment for adhesive bonding of polyethylene has been developed. It involves exposing the polymer to an environment of elemental fluorine or fluorine diluted in argon. By this treatment, extensive fluorination of the surface region is effected. The fluorinated surface permits formation of strong adhesive joints by conventional adhesive bonding techniques even though the wettability of the new surface is similar to polytetrafluoroethylene. We believe that treatment of the polymer with elemental fluorine effectively eliminates the weak boundary layer associated with polyethylene by either crosslinking or by increasing the molecular weight in the surface region.