Showing papers on "Polymer published in 1983"

The physics of amorphous solids

Abstract: The Formation of Amorphous Solids Amorphous Morphology: The Geometry and Topology of Disorder Chalcogenide Glasses and Organic Polymers The Percolation Model Localization Delocalization Transitions Optical and Electrical Properties Index.

Introduction to polymer viscoelasticity

Abstract: Phenomenological Treatment of Viscoelasticity Time--Temperature Correspondence Transitions and Relaxation in Amorphous Polymers Statistics of a Polymer Chain Rubber Elasticity Viscoelastic Models Dielectric Relaxation Chemical Stress Relaxation Appendix References Answers to Problems List of Major Symbols Index

Surface thermodynamics of bacterial adhesion.

Abstract: The adhesion of five strains of bacteria, i.e., Staphylococcus aureus (strain 049), Staphylococcus epidermidis (strain 047), Escherichia coli (strains 055 and 2627), and Listeria monocytogenes, to various polymeric surfaces was studied. The design of the experimental protocol was dictated by thermodynamic considerations. From the thermodynamic model for the adhesion of small particles from a suspension onto a solid substratum, it follows that the extent of adhesion is determined by the surface properties of all three phases involved, i.e., the surface tensions of the adhering particles, of the substrate, and of the suspending liquid medium. In essence, adhesion is more extensive to hydrophilic substrata (i.e., substrata of relatively high surface tension) than to hydrophobic substrata, when the surface tension of the bacteria is larger than that of the suspending medium. When the surface tension of the suspending liquid is larger than that of the bacteria, the opposite pattern of behavior prevails. Suspensions of bacteria at a concentration of 10(8) microorganisms per ml were brought into contact with several polymeric surfaces (Teflon, polyethylene, polystyrene, and acetal and sulfonated polystyrene) for 30 min at 20 degrees C. After rinsing, the number of bacteria adhering per unit surface area was determined by image analysis. The surface tension of the suspending medium. Hanks balanced salt solution, was modified through the addition of various amounts of dimethyl sulfoxide. It was found that the number of bacteria adhering per unit surface area correlates well with the thermodynamic predictions and that these data may be used to determine the surface tension of the different bacterial species. The surface tensions of the bacteria obtained in this fashion are in excellent agreement with those obtained by other methods.

Static and dynamic light scattering from branched polymers and biopolymers

Abstract: The striking properties of synthetic polymers and biological macromolecules are largely determined by their shape and the internal mobility. Both quantities are closely related to the architecture of the molecules. This article deals with branched macromolecules in dilute solution, where the individual molecules are observed. The common technique for determining the shape of macromolecules is static light scattering. Information on the internal mobility and the translational motion of the mass centre can be obtained from the more recent technique of quasi-elastic or dynamic light scattering.

Phase Behavior in Copolymer Blends : Poly(2,6-dimethyl-1,4-phenylene oxide) and Halogen-Substituted Styrene Copolymers

Abstract: A recently introduced mean field theory of phase behavior in polymer/copolymer systems is extended to random copolymer/copolymer systems. Miscibility in these systems does not require any specific interaction but rather a "repulsion" between the different covalently bonded monomers of the copolymers. Conversely, immiscibility may occur in systems with specific interaction due to an "attraction" between the different covalently bonded monomers of the copolymers. Using the mean field approach, we discuss in detail the phase behavior in polymer/copolymer systems. The requirements for the occurrence of a symmetric or an asymmetric (im)miscibility window in a temperature-copolymer composition diagram are derived. Using this treatment, we calculate all the segmental interaction parameters for blends of poly(2,6-dimethyl-l,4- phenylene oxide) with poly(o-chlorostyrene-co-p-chlorostyrene), poly(o-fluorostyrene-co-p-fluorostyrene), poly(styrene-co-o-chlorostyrene), poly(styrene-co-p-chlorostyrene), poly(styrene-co-o-fluorostyrene), and poly(styrene-co-p-fluorostyrene). The absence of miscibility in blends of poly(2,6-dimethyl-l,4-phenylene oxide) with any poly(o-bromostyrene-co-p-bromostyrene) copolymer is explained.

Electrochemical studies of some conducting polythiophene films

Abstract: Polythiophene and ..beta..-substituted polythiophenes are prepared by electrochemical oxidation and polymerization of their respective monomers. A property-structure correlation between monomers and their corresponding polymers is obtained by systematic variation of the chemical structure of the monomers. Film growth and conductivities are dependent on ..beta..-substituents, with conductivity of the order of 1 ohm/sup -1/ cm/sup -1/ obtained for poly(..beta..-methylthiophene).

Molecular dynamics of solid polymers as revealed by deuteron NMR

Abstract: Pulsed deuteron NMR spectroscopy is described, which has recently been developed to become a powerful tool for studying molecular dynamics in solid polymers. It is shown that by analyzing the line shapes of2H absorption spectra and spectra obtained via solid echo and spin alignment, respectively, both type and timescale of rotational motions can be determined over an extraordinary wide range of characteristic frequencies, approximately 10 MHz to 1 Hz. By applying these techniques to selectively deuterated polymers, motional mechanisms involving different segments of the monomer unit can be monitored. In addition, motional heterogeneities in glassy polymers can be detected. The information about polymer dynamics available now is illustrated by a number of experimental examples. The chain motion in the amorphous regions of linearpolyethylene is discussed in detail and it is shown that it can clearly be distinguished from the chain motion of an amorphous polymer above the glass transition, wherepolystyrene is used as an example. Localized motions in the glassy state are illustrated through the jump motion phenyl groups exhibit both in the main chain (polycarbonate) and as a side group (polystyrene). The latter polymers also serve as examples for detecting motional heterogeneity. Finally, the mobility in novel classes of systems,liquid crystalline polymers andpolymer model membranes as revealed by2H NMR are described.

Improved section adhesion for immunocytochemistry using high molecular weight polymers of L-lysine as a slide coating.

Abstract: Poly-l-lysine (PPL) has been used to coat glass slides in the preparation of tissue sections for immunocytochemical staining. The adhesive properties of different molecular weight (m.w.) polymers of l-lysine have been tested on pre-fixed cryostat sections which were subjected to a 3 day washing treatment. It has been found that the higher the molecular weight of the polymer, the greater the adhesive force it provides. PLL (m.w. 350,000) at concentrations in the range of 0.05–0.1% was found to be the most effective polymer.

Physicochemical Aspects of Polymer Surfaces

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On entanglements of flexible and rodlike polymers

Abstract: Determination du nombre d'atomes entre les enchevetrements pour 62 polymeres flexibles, semiflexibles ou fibreux

New method for estimating the parameters of the wormlike chain model from the intrinsic viscosity of stiff-chain polymers

Abstract: Emploi de l'equation de Yamakawa Fujii. Influence du volume exclu. Application au polyisocyanate d'heuyb, a un polyoside extracellulaire, le schizophyllane, aux polypeptides, trinitrate de cellulose et polyamides

Chemistry and technology of water-soluble polymers

Abstract: 1. The Interface between the Chemistry of Aqueous Polymer Solutions and Their Application Technology.- 2. The Rheological Characterization of Concentrated Solutions and Gels of Water Soluble Polymers.- 3. Methods of Polymerization for Preparation of Water Soluble Polymers.- 4. Water Sensitive Chemically Cross-linked Gels.- 5. Chemical Modification and some Cross-linking Reactions of Water Soluble Polymers.- 6. Thermoreversible Gelation.- 7. Solution Thermodynamics of Non-ionic Water Soluble Polymers.- 8. Fractionation and Characterization of Water Soluble Polymers.- 9. Water Solubility and Sensitivity-Hydration Effects.- 10. Aqueous Solutions of Polyelectrolytes.- 11. Polymer-Small Molecule Interactions.- 12. Excluded-Volume Interactions of Neutral Polymers in Solution.- 13. Polymer Adsorption.- 14. The Role of Polymers in the Stabilization of Disperse Systems.- 15. Water Soluble Polymers in the Stabilization of Dispersions, including Polymerizing Systems.- 16. Medical and Pharmaceutical Applications of Water Soluble Polymers.- 17. Some Properties of Polyvinyl Alcohol and their Possible Applications.- 18. Polymeric Flocculants.- 19. Polymers in Oil Recovery and Production.

Siloxane-containing polymers

Abstract: The properties of polymeric compositions can be improved by the presence of a polysiloxane unit of formula ##STR1## where Q is a substituted or unsubstituted aromatic group, Z is ##STR2## D is unsubstituted or substituted hydrocarbylene R 1 , R 2 , R 3 , R 4 , R 5 and R 6 each, independently, is unsubstituted or substituted hydrocarbyl x, y and z each independently has a value from 0 to 100 Polyimides containing these units display improved solubility and adhesion; they are useful, among other things, as protective coatings

The chemical and physical properties of pyrrole‐based conducting polymers: The oxidation of neutral polypyrrole

Abstract: A series of experiments on the physics and chemistry of polymers derived from pyrroles show that the oxidation of neutral insulating polypyrrole (PP0) to its conducting counterpart (PP+) is a multistep process. In particular, the conductivity of the polymers increases only in the early stages of oxidation, whereas significant changes in the optical and EPR properties occur in later stages of the oxidation when no further changes in the conductivity take place. The early stages of oxidation lead to an ionic (PP+ anion−) polymer and the later stages of oxidation result in chemistry at the nitrogen atoms of the pyrrole rings. Similar behavior is observed for all the oxidized pyrrole polymers independent of the method of oxidation.

Composites on a molecular level: Phase relationships, processing, and properites

Abstract: Phase relationships in concentrated solution and in the bulk of a solvent/rigid-rod/flexible-coil system were investigated. The solvent was a mixture of two strong acids. The rigid-rod polymer was poly-p-phenylenebenzobisthiazole (PBT). The flexible-coil polymer was poly-2,5(6)benzimidazole (ABPBI). The concentrated solution and bulk morphologies were investigated by means of polarized optical microscopy, small-angle light scattering, scanning electron microscopy, and wide-angle x-ray diffraction techniques. Above a critical concentration, Ccr, the pseudo ternary solution separated into two coexisting phases, one optically anisotropic (liquid crystalline) and the other isotropic. The anisotropic domains were highly birefringent. They contained primarily the PBT macromolecules oriented perferentially along a domain axis. Numerical values of Ccr, determined experimentally, were in good agreement with calculated predictions. Aggregates composed of PBT molecules were observed to be dispersed in a con...

Electrochemical synthesis of electrically conducting polymers from aromatic compounds

Abstract: Amorphous, electrically conducting polymeric films can be deposited from acetonitrile solutions of specific aromatic compounds containing an appropriate electrolyte. Free-standing films peeled off a platinum electrode have electrical conductivities between 10-3 and 1 Ω-1 -cm-1. Polymers resembling the better-known polypyrrole have been obtained from benzenoid, nonbenzenoid, and heterocyclic monomers. A few characteristic examples are discussed to highlight the characterization efforts. Also discussed are the chemical investigations which have provided some insight into the mechanism of formation and the structure of these conducting polymers.

Cationic compounds having clay soil removal/anti-redeposition properties useful in detergent compositions

Abstract: Water-soluble zwitterionic compounds having clay soil removal/anti-redeposition properties. The zwitterionic compounds are selected from monozwitterionic compounds, dizwitterionic compounds, polyzwitterionic compounds, and zwitterionic polymers. These zwitterionic compounds are useful in detergent compositions at from about 0.05 to about 95% by weight. In addition to the zwitterionic compounds, the detergent compositions further comprise from about 1 to about 75% by weight of a nonionic, anionic, ampholytic, zwitterionic, or cationic detergent surfactant or mixture thereof.

Dipped rubber article

Abstract: A skin-contacting coating of a lubricating hydrogel polymer bonded to a rubber article (such as a surgeon's glove) is treated by means of surfactant material (such as a bactericidal cationic surfactant which preferably has an N-hexadecyl group) or a long chain fatty amine so as to substantially improve the lubricity of the coating with respect to damp skin. The hydrogel polymer is preferably a copolymer of 2-hydroxyethylmethacrylate (HEMA) with methacrylic acid (MAA) or with 2-ethylhexyl acrylate (EHA) or with both MAA and EHA. The copolymer contains HEMA and MAA is a molar ratio of 1 to 10:1 of HEMA and EHA in a molar ratio of 2.5 to 10:1. Such a hydrogel polymer has improved lubricity to dry skin and, if used for this purpose, need not be treated with a surfactant or fatty amine to improve the lubricity with respect to damp skin.

The influence of morphology and molecular weight on ductile-brittle transitions in linear polyethylene

Abstract: The tensile behaviour of linear polyethylene was examined over a wide range of temperatures. Samples were prepared from low and medium molecular weight polymer with different morphologies, by varying the initial crystallization conditions. It was found that the temperature of the ductile-brittle transition was markedly different for different samples. In particular, low molecular weight polymer crystallized at a low degree of of supercooling, showed brittle behaviour over most of the temperature range, with a ductile-brittle transition near to room temperature. Rapidly quenched material, where the degree of supercooling is high, showed a very low ductile-brittle transition temperature, especially in high molecular weight polymer. The reasons for these differences in behaviour are discussed both at a phenomenological level and in terms of known structural differences between the different materials examined.

Structure and oxygen-barrier properties of metallized polymer film

Abstract: The structure of thin (10 to 50 nm) aluminium layers vacuum deposited on to polyester film is examined using both transmission electron microscopy and light microscopy. The density of pinhole defects in the aluminium coating, quantified by an image analysing microscope, is shown to determine the permeability of the film to oxygen. Finite element calculations of the effect of various pinhole diameters and densities on the permeability agree with experiment, and also show that the barrier properties of the polymer layers immediately adjacent to the metal coating are critical in determining the deleterious effect of pinhole defects.

Calcination of precipitated Mg(OH)2 to active MgO in the production of refractory and chemical grade MgO

Abstract: The processes that occur during the calcination of seawater or brine precipitated Mg(OH)2 to active MgO are reviewed. Details of the commercial calcination of Mg(OH)2, and of the crystallography, mechanism and kinetics of the thermal decomposition of Mg(OH)2 to MgO are given. The effects of calcination conditions, and of chemical and physical properties of the Mg(OH)2 on the properties of the active MgO product are discussed together with the influence of typical impurities in commercial products.

Epitaxial crystallization of polymers onto benzoic acid: Polyethylene and paraffins, aliphatic polyesters, and polyamides

Abstract: Epitaxial crystallization of polyethylene, n-paraffins, aliphatic polyesters, and various polyamides has been achieved on benzoic acid crystal substrates, specifically on their (001) crystals faces, which are made up of the aromatic rings. The epitaxial relationship is very similar for all polymers investigated: it is characterized by a unique chain orientation (parallel to the b axis of the substrate) and a plane of contact which is either the b-c, plane of polyethylene, or crystallographically similar ones for polyesters, or the plane of the hydrogen-bonded sheet for polyamides. Since benzoic acid is structurally similar to its alkali-metal salts, it is inferred that the nucleating efficiency of the latter toward chemically different but structurally similar polymers may well rest on an epitaxial relationship. Finally, the highly oriented morphology made it possible, for some polyesters with a monoclinic cell, to determine the angle between the chain axis and the Z axis of the optical indicatrix, a quantity not measured so far in polymers.

Absorbable bone fixation device

Abstract: An absorbable internal bone fixation device is disclosed. The device is made from a high molecular weight polymer of L(-)lactide having an inherent viscosity above 4.5. The polymer contains less than 2% unreacted monomer and is polymerized under conditions of selected monomer to catalyst ratios and temperature.