Showing papers in "Macromolecules in 1988"

pH-Dependent Equilibrium Swelling Properties of Hydrophobic Polyelectrolyte Copolymer Gels

Abstract: Etude a 25°C de polymeres reticules a base de methacrylates de n-alkyle et de (dimethyl-amino) ethylmethacrylate Gonflement dans l'eau Transition de l'etat hydrophobe a l'etat hydrophile Influence de la composition du comonomere

Poly(lactones). 9. Polymerization mechanism of metal alkoxide initiated polymerizations of lactide and various lactones

Abstract: Polymerisation en masse et en solution entre 50 et 150°C de: β-propiolactone D,L-p-butyrolactone, e-caprolactone et L,L-lactide

A statistical theory of weakly charged polyelectrolytes: fluctuations, equation of state, and microphase separation

Abstract: Developpement d'une theorie de solutions de polyelectrolytes avec des polyions de faible densite de charge lineaire

Preferential surface adsorption in miscible blends of polystyrene and poly(vinyl methyl ether)

Abstract: : The surface structure and properties of miscible blends of polystyrene (PS) with poly(vinyl methyl ether) (PVME) have been studied as a function of the blend composition and constituent molecular weights. The lower surface tension of the PVME compared to that of PS results in preferential adsorption of PVME at the surface. The surface PVME enrichment is characterized by measurements of the surface tension as a function of the temperature, accomplished with an automated pendant drop apparatus, and by x-ray photoelectron spectroscopy (XPS). Angle-dependent XPS has been used to determine the surface concentration profiles of the blend constituents.

Cellulose-poly(vinyl alcohol) blends prepared from solutions in N,N-dimethylacetamide-lithium chloride.

Abstract: Etude de la miscibilite et de la cristallinite en fonction de la composition et de la temperature

Crystal structure and morphology of syndiotactic polypropylene single crystals

Abstract: In the past several years there have been an increased interest in the crystal structure and morphology of s-PP due to the new development of homogeneous metallocene catalysts which can produce s-PP having a high stereoregularity. In this research, the crystal structure and morphology of s-PP single crystals grown from the melt were investigated. A series of ten fractions of s-PP was studied with different molecular weights ranging from 10,300 to 234,000 (g/mol). These fractions all possess narrow molecular weight distributions (around 1.1-1.2) and high syndiotacticities ([r]{approximately}95%). The main techniques employed including transmission electron microscopy (TEM), atomic force microscopy (AFM), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS).

Glass transition and melting behavior of poly(ethylene 2,6-naphthalenedicarboxylate)

Abstract: Capacite calorifique du polymere a l'etat solide (230-350 K) et a l'etat liquide (390-600°K)

Adsorption of block copolymers in selective solvents

Abstract: We study the adsorption of A-B diblock copolymers on a solid plane in a highly selective solvent The A part is in a poor solvent and forms a molten layer on the solid wall where the solvent does not penetrate The B part, in a good solvent, forms a brush grafted on this molten layer The structure of the adsorbed copolymer film is governed by the chemical potential in the solution in contact with the wall Copolymer chains have a tendency to self-aggregate in this solution forming several different mesophases We present first a scaling theory of micelle and lamella formation and then study the geometry of the adsorbed film in equilibrium with these two phases An important issue of this work is the role of the van der Waals interaction between the wall and the adsorbed A layer If the copolymer asymmetry is large enough, Le, if the B part has a higher molecular mass than the A part, in a wide range of concentration, and this quite independent of the phase behavior of the solution, the thickness of the molten A layer results from a balance between the van der Waals energy and the stretching energy of the brush The B chains are almost fully extended in the brush Various other adsorption regimes are found when the asymmetry of the copolymer is decreased

Stoichiometry effects on rheology of model polyurethanes at the gel point

Abstract: Reseaux prepares par reaction d'α,ω-dihydroxypolypropene oxyde avec le tris(isocyanato-4 phenyl thiophosphate)

Microstructure of isotactic polypropylene prepared with homogeneous catalysis: stereoregularity, regioregularity, and 1,3 insertion

Abstract: Etude comparative par 13 C RMN de la structure stereochimique d'echantillons prepares dans differentes conditions de reaction

Interfacial tension of immiscible polymer blends: temperature and molecular weight dependence

Abstract: : Interfacial tensions between immiscible homopolymers are measured using an automated pendant drop apparatus, which utilizes Video Digital Image Processing techniques. A recently developed robust shape analysis algorithm is used to analyze the experimental drop profiles. The data show the effect of temperature and number average molecular weight (Mn) on the interfacial tension for the immiscible blends polystyrene-poly(methyl methacrylate), polybutadiene-poly(dimethyl siloxane) and polystyrene-hydrogenated 1,2 polybutadiene. Interfacial tension decreases linearly with temperature and increases with molecular weight. The data for all three systems can be approximated by an empirical relationship. The interfacial tension data for the latter blend system are compared with thermodynamic theories of polymeric interfaces. A square gradient theory approach, in conjunction with the Flory-Huggins expressions for the free energy of mixing, predicts a magnitude and temperature dependence of interfacial tension which are in reasonable agreement with experimental data, and does predict a molecular weight dependence which roughly follows the empirical relationship.

Neutron and x-ray scattering studies on semicrystalline polymer blends

Abstract: Melange de PEO avec PMMA protone ou deuterie. PMMA est incorpore dans la phase amorphe entre les lamelles cristallines

Ring-opening polymerization of 3(S)-[(benzyloxycarbonyl)methyl]-1,4-dioxane-2,5-dione: a new route to a poly(.alpha.-hydroxy acid) with pendant carboxyl groups

Abstract: Obtention d'un copolymere alterne forme d'unites acide glycolique et α-(S)-malate de benzyle

Synthesis of polyphenylene from a cis-dihydrocatechol biologically produced monomer

Abstract: Le dihydrocatechol est obtenu par oxydation du benzene par la dioxygenase contenue dans le microorganisme Pseudomonas putida. Polymerisation radicalaire en compose aromatise par chauffage

Structural Transitions from Spherical to Nonspherical Micelles in Blends of Poly(styrene-butadiene) Diblock Copolymer and Polystyrene Homopolymers

Abstract: Blending of a block copolymer with a large amount of homopolymer can result in the formation of a micellar phase consisting of spherical domains of the aggregating copolymer block. We show that transitions in micelle shape and mesophase type($ can occur by increasing the molecular weight of the homopolymer matrix, by increasing the aggregating block molecular weight, or by increasing the volume fraction of the copolymer. The new morphologies include cylindrical micelles, vesicles, and lamellar type structures. These transitions can be understood in terms of the general rule of domain morphology as a function of relative microphase volume fractions put forth by Molaul for neat block copolymers and later extended by Sadron and Gallot2 to the case of block copolymers in preferential solvents.

Polymerization of monomers containing functional silyl groups. 5. Synthesis of new porous membranes with functional groups

Abstract: Membrane microporeuse a partir d'un film de copolymere sequence prepare par polymerisation anionique vivante de l'isoprene dans le THF puis addition de (vinyl-4 phenyl) dimethyl propoxy-2 silane dans le THF