Showing papers on "Polystyrene published in 1981"

Heat Capacity and Other Thermodynamic Properties of Linear Macromolecules. IV. Polypropylene

Abstract: The heat capacity of polystyrene from 0 K to 600 K is reviewed on the basis of measurements on 29 samples reported in the literature. A set of recommended data for amorphous polystyrene is derived. The effect of tacticity on the heat capacity is also evaluated. Entropy and enthalpy functions are calculated. This paper is the fifth in a series of publications which will ultimately cover all heat capacity measurements on linear macromolecules.

Interactions in mixtures of colloidal silica spheres and polystyrene molecules in cyclohexane

Abstract: Phase separations in dispersions of different types of spherical, lyophilic, monodisperse silica particles and polystyrene molecules in cyclohexane at the theta temperature were investigated. We used silica particles stabilized with a chemically bonded layer of stearyl alcohol molecules and silica particles stabilized with tetraethylenepentamine-terminated polyisobutene molecules. At a fixed silica concentration (1.0 or 5.0% w/v) a liquid-liquid phase separation occurs above some limiting polystyrene concentration. The limiting concentration, c lim , usually is of the order of a few percent (w/v), and depends on the molar mass of the polymer. High-molar-mass polymers show a lower c lim value than low-molar-mass polymers. An increase in the concentration of the silica particles lowers the c lim value. The radius of the silica particles also influences c lim . The experimental results are interpreted in terms of a simple “hard sphere-cavity” model, with which a theory is worked out which is based on first principles only. Most experimental results can be reproduced by theoretical calculations on a semiquantitative scale. Discrepancies between theory and experiment only are found with the silica samples that obviously do not conform to the hard sphere model used.

Anomalous preferences of cultured macrophages for hydrophobic and roughened substrata.

Abstract: Peritoneal macrophages were plated out on a series of artificial haptotactic substrata consisting of grid patterns of vacuum-evaporated palladium metal alternating with hydrophobic untreated polystyrene and with hydrophilic sulphonated polystyrene. By their active locomotion the macrophages accumulated preferentially onto the less hydrophilic of either pair of these alternative substrata. This order of substratum preference is precisely the opposite to that shown by fibroblastic cells. Macrophages were also found to accumulate preferentially onto roughened culture surfaces as opposed to smooth ones, which is again opposite to the behaviour of fibroblasts. These opposite substratum preferences shown by macrophages may reflect physical as well as functional differences in their surfaces, and could serve as assay criteria for macrophages and cell types putatively equivalent to macrophages.

Metal‐polymer interfaces: Adhesion and x‐ray photoemission studies

Abstract: The interfaces formed by evaporating copper, nickel, and chromium layers on polystyrene, polyvinyl alcohol, polyethylene oxide, polyvinyl methyl ether, polyvinyl acetate, and polymethyl methacrylate have been studied with x‐ray photoemission spectroscopy (XPS). The adhesion strengths of the metal films to the polymers were measured by a tensile‐pull test. At submonolayer coverages of the metals, the peak positions and widths of the metallic electron core levels measured with XPS vary significantly from one polymer substrate to another. Most of these variations can be accounted for in terms of changes in the atomic and extra‐atomic relaxation energies during the photoemission process. Much of this change is brought about when the metal atom deposited on an oxygen‐containing polymer interacts with the substrate oxygen and forms a metal‐oxygen‐polymer complex. The presence of this complex is verified by changes in the photoemission lineshapes of the substrate carbon and oxygen atoms. The XPS signatures of th...

Bacterial adherence to polystyrene: a replica method of screening for bacterial hydrophobicity.

Abstract: A simple replica method is described for the rapid identification of colonies of bacteria which adhere to polystyrene. A correlation was found between the adherence of bacterial strains to polystyrene and cell surface hydrophobicity, suggesting the use of this technique in screening for cell surface mutants and in the isolation of hydrophobic bacteria from nature.

Phase separation of polymer blends in thin films

Abstract: Films of polystyrene-poly(vinylmethyl ether) blends of various compositions are formed by a dip-coating procedure, the thickness of the film being controlled by the concentration of the solution. The substrates used are glass and gold. The phase separation process is followed by a laser light scattering experiment in which the total forward scattering intensity is monitored as a function of temperature. Morphological examination shows that phase separation occurs by a spinodal decomposition mechanism. A thickness effect on the phase separation temperature is noticeable when film thickness is smaller than 1 μm. This effect is substrate dependent. In all films formed on gold the spinodal temperature increases as film thickness decreases. Films formed on glass exhibit a destabilizing effect on decreasing film thickness. This effect is slight in films of composition poorer in polystyrene than the critical composition, and is enhanced in films richer in polystyrene. The stabilizing effect of decreasing the thickness of films formed on the gold substrate is considered to reflect mainly a purely geometrical effect. The decreasing dimensionality is shown by simple theoretical considerations to increase the phase-separation temperature. However, the phase separation behavior of thin films on glass appears to be the result of two kinds of substrate-polymer interactions in addition to the geometrical effect: (a) electrostatic interaction of the charged glass surface (a destabilizing effect at all film compositions) and (b) selective adsorption of polystyrene on glass.

Quasielastic light scattering measurements of polystyrene latices and conformation of poly(oxyethylene) adsorbed on the latices.

Abstract: Quasielastic Light Scattering Measurements of Polystyrene Latices and Conformation of Poly(oxyethylene) Adsorbed on the Latices

Some comments on the swelling of polymeric networks in relation to their structure

Abstract: We report measurements of the equilibrium concentration and of the elastic modulus for polystyrene networks containing controlled amounts of pendent chains that have been swollen in benzene and cyc...

Preparation and electrical properties of quaternary ammonium montmorillonite-polystyrene complexes

Abstract: Intercalation compounds of styrene and quaternary ammonium montmorillonite were prepared by immersion of the clay in styrene monomer. The intercalation of stearyltrimethylammonium (CHa(CH~)lTN(CHs)a+)-montmorillonite and styrene showed an expansion of the basal spacing to a constant value of ~32 ,~ after immersion for 10 days. After polymerization, the amount of polystyrene in the inter- layer region was determined by thermal gravimetric analysis. Styrene adsorption initially increased with increasing quaternary ammonium cation and then became approximately constant when loading of the quaternary ammonium cation exceeded 100 meq/100 g clay. The volume resistivity of the stearyltrimethyl- ammonium-montmorilionite-polystyrene complex, which was determined with a high resistance meter, was greater than that of both the quaternary ammonium-montmorillonite and the montmorillonite, and increased in proportion to the amount of polymer adsorbed. These data indicate that polystyrene improved the insulating properties of the clay films.

Method and catalyst for making bisphenol

Abstract: A sulfonated polystyrene ion-exchange resin is provided having organo mercaptan groups attached to backbone sulfone radicals by covalent nitrogen-sulfur linkages. The ion-exchange resin can be used to effect phenol-ketone condensation in the synthesis of bisphenols.

Solid-phase peptide synthesis under continuous-flow conditions

Abstract: A system is described for solid-phase synthesis of peptides under continuous-flow conditions with liquid chromatographic equipment, conventional polystyrene supports, and well-defined chemistry. The model tetrapeptide Leu-Ala-Gly-Val was assembled in 99.3% purity in about 4 hr on microporous copoly(styrene-1% divinylbenzene). During coupling, the preformed symmetric anhydrides were conserved by being recycled. Relative yields of the peptide products were determined quantitatively in 20 min by reverse-phase high-pressure liquid chromatography. This rapid assay system was used to examine the influence on product yields of (i) the time and number of couplings per cycle, (ii) microporous versus macroporous polystyrene, and (iii) tert-butoxycarbonyl (Boc) group versus 9-fluorenylmethoxycarbonyl for amine protection. Use of microporous polystyrene and two 30-min couplings of Boc-amino acids per cycle gave the best results. This continuous-flow system provides a rapid and efficient approach to solid-phase peptide synthesis. A 17-residue peptide from chicken ovalbumin was obtained in similar purity and yield from a discontinuous synthesis and from a continuous-flow synthesis.

Polymer-bound “Dimethylaminopyridine” as a Catalyst for Facile Ester Synthesis

Abstract: Polystyrene beads which covalently link a dimethylaminopyridine unit act as a catalyst for ester synthesis by the DCC method. The polystyrene beads are reusable and the synthetic method is very simplified.

Polyphenylene ether compositions

Abstract: There are provided thermoplastic compositions comprising a polyphenylene ether and a rubber modified polystyrene resin having a discontinuous phase of polystyrene particles englobed in diene rubber membranes, the particles being between about 0.1 and 0.7 microns in diameter. Such compositions provide molded articles with substantial and unexpected improvements in impact resistance and ability to transmit light in comparison with known compositions of such rubber modified polystyrenes alone or those of other polystyrenes combined with polyphenylene ethers.

Compatibility studies of styrene and hydroxyl containing styrene copolymers with poly(ethylene oxide)

Abstract: Copolymers of styrene with vinylphenyl trifluoromethyl carbinol, p-vinylphenyl trifluoromethyl carbinol, vinylphenyl hexafluorodimethyl carbinol, and p-vinylphenol are conditionally compatible with poly(ethylene oxide), depending on their composition and blending ratios, whereas copolymers of styrene and vinylphenyl methyl carbinol are much less compatible with poly(ethylene oxide), as determined by Tg criteria and differential scanning calorimetry. The crystallinity of poly(ethylene oxide) is changed in the copolymer/poly(ethylene oxide) blends, as indicated by depressions of the poly(ethylene oxide) melting point. Hydrogen-bond formation has been studied in two selected blends by infrared (IR) spectroscopy. Hydrogen bonding dissociation and reassociation as a function of temperature are reported. The conformation changes of poly(ethylene oxide) in the blends, the interaction between copolymer and poly(ethylene oxide) as well as in the reference blend, polystyrene/poly(ethylene oxide), are also investigated.

Polystyrene fluorescence: effects of molecular weight in various solvents

Abstract: Because excimer formation occurs by the rotation of bonds to bring two adjacent chromophores into a coplanar arrangement, the ratio of excimer to monomer fluorescence intensity (I/sub E//I/sub M/) was used as a probe of the conformational transitions in these molecules. Four solvents were used in the studies.

Process for the bromination of polystyrenes

Abstract: There is disclosed a process for producing a tri-halogenated polystyrene flame retardant for synthetic resins, whereby high molecular weight polystyrene is reacted with bromine chloride in a chlorinated hydrocarbon solvent, under substantially anhydrous conditions, in the presence of a catalytic amount of a Lewis acid.