Search results for "Polystyrene"

“Ball at the wall” — A new lamellar multiphase morphology in a polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock copolymer

1994

Structural Characterization of the “Knitting Pattern” in Polystyrene-block-poly(ethylene-co-butylene)-block-poly(methyl methacrylate) Triblock Copoly…

1998

In a polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock copolymer (SBM) a morphological transition from a lamellar (ll) morphology (with sequence ABCB) to the knitting pattern (kp) morphology occurs upon hydrogenation of the center PB block. Structural information of the nonhydrogenated and the hydrogenated material is provided from small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). For the nonhydrogenated SBM sample the SAXS profile correlates well with a simple periodic lamellar structure. The hydrogenated sample forming the kp morphology displays a more complex SAXS pattern. From the TEM images of the knitting pattern the two-dimensional…

NMR-investigation of the mechanism of silver mercaptide thermolysis in amorphous polystyrene

2007

Polymer-embedded silver clusters have been prepared by thermal decomposition of silver dodecylmercaptide previously dissolved in amorphous polystyrene. The morphology and structure of silver clusters have been determined by transmission electron microscopy (TEM) and large angle X-ray diffractometry (XRD), respectively. The mechanism involved in the thermolysis reaction was elucidated by different NMR techniques. The thermolysis produced thiol-derivatized silver clusters (i.e., silver clusters coated with a self-organized thiol monolayer, Agx(SC12H25)y) and had the effect of increasing the branching degree of polystyrene due to enhanced cross-linking.

Synthesis of 3D dendritic gold nanostructures assisted by a templated growth process: Application at the detection of traces of molecules

2020

International audience; Complex architectures like 3D gold dendritic nanostructures were synthesized by an in situ templated growth method using a thin film of a block copolymer [polystyrene-b-poly(4-vinylpyridine)] deposited onto silicon substrates. The overall study has demonstrated the strong link between the morphology, size, and distribution of the structures and the synthetic physicochemical parameters, such as pH, reaction temperature, concentration, and nature of reactants. A nonequilibirum state of the medium has been required to create a fractal growth of the gold structures onto a prepatterned gold-seeded surface and has led to a better control of the structures' surface coverage…

Crystallization kinetics of colloidal binary mixtures with depletion attraction.

2014

In this work the crystallization kinetics of colloidal binary mixtures with attractive interaction potential (Asakura–Oosawa) has been addressed. Parameters such as fraction of crystals, linear crystal dimension and crystal packing have been quantified in order to understand how the crystal formation is driven in terms of the depth of the attractive potential and the composition of the binary mixture (described by the number ratio). It was found that inside the eutectic triangle, crystallization is mainly governed by nucleation and the crystal packing is close to the close-packing of hard spheres. Moving out from the eutectic triangle towards small component results in the crystallization o…

Advances in organic and organic-inorganic hybrid polymeric supports for catalytic applications

2016

In this review, the most recent advances (2014–2016) on the synthesis of new polymer-supported catalysts are reported, focusing the attention on the synthetic strategies developed for their preparation. The polymer-supported catalysts examined will be organic-based polymers and organic-inorganic hybrids and will include, among others, polystyrenes, poly-ionic liquids, chiral ionic polymers, dendrimers, carbon nanotubes, as well as silica and halloysite-based catalysts. Selected examples will show the synthesis and application in the field of organocatalysis and metal-based catalysis both for non-asymmetric and asymmetric transformations.

Capacitive scanning dilatometry and frequency-dependent thermal expansion of polymer films

2000

The dilatometric properties of polymer films near and above their glass-transition temperatures were explored using capacitive high-frequency detection in temperature ramping as well as in harmonic temperature cycling experiments. The broad applicability of capacitive scanning dilatometry is demonstrated by the investigation of macromolecular systems of vastly different polarity such as polystyrene, polybutadiene, and polyvinylacetate. From temperature cycling experiments the real and imaginary parts of the frequency-dependent thermal-expansion coefficient are determined in the sub-Hz regime.

A contribution to the kinetics of the polymerization of styrene with CF3SO3H as catalyst

1978

The time dependence of the cationic polymerization of styrene in CH2Cl2 with CF3SO3H as catalyst can be formally described as being first-order with respect to monomer concentration [M]0. The reaction rate shows a third-order dependence in catalyst concentration [C]0. A high polymer and a low polymer polystyrene fraction are found at [M]0>0.2 mole · l−. The reaction rate of the high polymer fraction is proportional to [C] 0 3 , that of the low polymer fraction probably proportional to [C] 0 2 . The polymerization active species may thus be triple ions in the first and ion pairs in the second case.

Pressure dependence of the demixing of polymer solutions determined by viscometry

1981

From the break-down in the viscosity of a polymer solution, associated with the entrance into the two phase region, the pressure dependence of the demixing temperatures of solutions of polystyrene (M = 600.000) in cyclohexane, cyclopentane, diethylmalonate and 1-phenyldecane was measured up to 1000 bar. The application of pressure increases the solubility of polystyrene in cyclopentane and diethylmalonate, but decreases that in 1-phenyldecane; in the case of cyclohexane, a pressure of optimum miscibility is observed at ca. 120 bar.

Testing of a kinetics equation of mechanical degradation

1987

A modification of the kinetics equation of mechanical degradation of Harrington and Zimm is proposed to fit experimental data taken on a molten polystyrene. This equation is applied to each molecular weight of the discretized molecular weight distribution curve, and the limiting molecular weight is determined for each molecular weight. With this modification the theoretical curves fit both Mw and Mn curves well.