Search results for "Polystyrene"

Residual order in amorphous dry films of polymer latices: indications of an influence of particle interaction

2002

Abstract We report small angle X-ray scattering and atomic force microscopy measurements on macroscopically thick, dry films of polymer latex particles. While the surface of dried droplets has long range order due to layering effects, the overall bulk structure is amorphous. This holds for both low charge polymethylmetacrylate particles and for highly charged polystyrene particles with additional stabilisation with sodiumdodecylsurfate. In the latter case, however, considerable amounts of residual crystal-like order is observed.

NMR Matrix Technique for Detecting Self Diffusion in Polymers

1979

A technique is discussed where monodisperse small spheres or cylindrical fibers of a polymer are embedded in a matrix of the corresponding fully deuterated polymer. On annealing the sample at a temperature above the glass transition the protonated macromolecules diffuse into the deuterated matrix and vice versa. Since the NMR spectrum depends upon the intermolecular proton proton dipolar coupling, the decrease of this coupling can be used to monitor the diffusion process. For particle diameters d ∼ 10−4 cm and annealing times t ∼ 105 s, extremely small diffusion constants D < d2/t are attainable. The NMR analysis of prospective diffusion experiments with polystyrene is discussed in some det…

A friction factor analysis of the coupling between polymer/solvent self- and mutual-diffusion: polystyrene/toluene

1996

The Bearman statistical mechanical theory, which couples the mutual-diffusion and self-diffusion coefficients via friction factors, has been applied to polystyrene/toluene solutions with polystyrene molecular weights of 18 kDa and 900 kDa. Toluene and polystyrene self-diffusion coefficients, obtained from the literature and measured here, along with polystyrene/toluene binary mutual-diffusion coefficients and thermodynamic data, were employed to independently calculate the three friction coefficients (ξ 12 , ξ 11 , and ξ 22 ) required to describe transport within binary solutions. Results reveal that the frequently used geometric mean approximation (GMA) for relating the friction coefficien…

Polymer-induced phase separation in suspensions of bacteria

2010

We study phase separation in suspensions of two unrelated species of rod-like bacteria, Escherichia coli and Sinorhizobium meliloti, induced by the addition of two different anionic polyelectrolytes, sodium polystyrene sulfonate or succinoglycan, the former being synthetic and the latter of natural origin. Comparison with the known behaviour of synthetic colloid-polymer mixtures and with simulations show that "depletion" (or, equivalently, "macromolecular crowding") is the dominant mechanism: exclusion of the non-adsorbing polymer from the region between two neighbouring bacteria creates an unbalanced osmotic force pushing them together. The implications of our results for understanding phe…

1986

The variation of the Huggins coefficient KH with the relative molecular mass M of the polymers was measured for solutions of polystyrene and of polyisobutylene and found to be most pronounced in the case of thermodynamically good solvents but vanishing at the theta-temperature, where the individual curves kH (T; M) intersect with each other. The experimental results are interpreted as a consequence of the rheological inequality of inter- and intra-molecular contacts between polymer segments. A model is presented according to which kH should be a linear function of M−(a−0,5), where a is the exponent of the intrinsic viscosity-relative molecular mass relationship (Kuhn-Mark-Houwink). The eval…

Surface-Functionalized Latex Particles as Controlling Agents for the Mineralization of Zinc Oxide in Aqueous Medium

2005

Polystyrene latex particles modified at the surface with different hydrophilic functional groups were prepared by miniemulsion polymerization and used as controlling agents in the crystallization of zinc oxide from aqueous medium. The effects of the chemical nature of the surface functionalization and the latex concentration on the crystal growth, morphology, and crystalline structure of the resulting zinc oxide were analyzed. Micro- and submicrosized crystals with a broad variety of morphologies depending on the functionalization were obtained. Among the different latexes studied, the acrylic-acid-derived particles were shown to be a convenient system for further quantitative investigation…

Interfacial tension of demixed polymer solutions: augmentation by polymer additives

1997

The interfacial tension between phase separated polymer solutions increases pronouncedly upon the addition of asmall amounts of incompatible polymers. This feature is demonstrated by means of measurements with solutions of polystyrene in cyclohexane and the folloowing additives: poly(styrene-block-dimethylsiloxane), polyisobutylene and polydimethylsiloxane. Theoretical considerations based on a correlation between the lenth of the tie lines and the corresponding interfacial tension corroborates this finding

Miscibility of a DGEBA Based Epoxy Resin Blended with Thermoplastic Mixtures of Poly(styrene) and Block Copolymers: Influence of the Copolymer Conten…

2008

The miscibility and phase behavior of ternary systems formed by a DGEBA based epoxy resin, polystyrene (PS), and diblock copolymers has been investigated through phase diagrams experimentally obtai...

Modification of commercial UF membranes by electrospray deposition of polymers for tailoring physicochemical properties and enhancing filtration perf…

2020

Abstract The main challenge for a widespread use of nanoporous membranes in the removal of ionic contaminants lies in the adjustment of their physicochemical properties to allow adequate ion rejection and mitigate fouling based on the targeted application. Most of the commercial membranes are negatively charged and their use is thus not necessarily relevant for divalent cation rejection. The main objective for researchers is therefore to provide novel tailored membranes by developing specific synthesis or modifying available membranes. It is proposed here to tailor physicochemical properties of a commercial low molecular weight cut-off ultrafiltration membrane by electrospray deposition of …

Über eine Beziehung zwischen Verdünnunasentropie und Verdünnungsenthalpie in Lösungen von Polystyrol und Polymethylmethacrylat

1973

Durch Lichtstreuungsmessungen wurde der Entropieanteil und der Enthalpieanteil des 2. osmotischen Virialkoeffizienten (A2) von athermischen und exothermischen Losungen von Polystyrol (PS) und Polymethylmethacrylat (PMMA) bei 25°C und Normaldruck bestimmt. Zur Auffindung von athermischen und exothermischen Losungsmitteln fur diese Polymeren wurde die Temperaturabhangigkeit des STAUDINGERindex verwendet. Die ermittelten thermodynamischen Grosen A2, A2,S und A2,H ergeben zusammen mit fruheren Messungen eine beziehung, die nahezu unabhangig vom speziellen System ist. The second osmotic virial coefficient A2 and its entropic and enthalpic parts of athermal and exothermal solutions of polystyrene…