Structure of inhomogeneous polymer networks prepared from telechelic polybutadiene

The structure and dynamics of segmented polyurethane networks prepared from poly(butadiene) diols (PBD) of different molecular weights M-n = 1200, 2160,2650,4690 and 10,300 g mol(-1), 4,4'-diphenylmethane diisocyanate (MDI) and poly(oxypropylene) triol (POPT) (M, = 710 g mol-1) have been investigated by dynamic mechanical analysis, dielectric relaxation spectroscopy, differential scanning calorimetry (DSC), small- and wide-angle X-ray scattering (SAXS and WAXS). Microphase separation on Danometre scale has been confirmed by SAXS in all networks. Except for the highest molecular weight of PBD, the networks consist of microdomains of similar size and composition dispersed in the soft phase of polybutadiene segments. Dielectric spectroscopy revealed the existence of three types of noncrystalline phases, each characterised by a well-developed dynamic glass transition. Absence of crystallinity has been proven by WAXS and DSC. (C) 2002 Elsevier Science Ltd. All rights reserved.status: publishe

SANS study of multilayer nanoparticles based on block copolymer micelles

A novel type of three-layer nanoparticles was studied using small-angle neutron scattering (SANS). The particles were prepared by adding methyl methacrylate monomer to a polystyrene-block-poly(methacrylic acid) micellar solution in aqueous buffer and subsequent polymerization by gamma -irradiation. The contrast-matching SANS experiments revealed that upon polymerization, the PMMA chains form a layer on the surface of the PS cores of the original micelles. This is in agreement with the finding that at room temperature, MMA monomer molecules do not penetrate into the micelle core in detectable amounts. In the presented example, the mean core radius of original micelles and the layer thickness were determined to be 99 and 17 Angstrom, respectively. Both characteristics are expected to be controllable by the choice of block copolymer micelles and the parameters of the polymerization process. (C) 2001 Elsevier Science Ltd. All rights reserved

Polymer dynamics In an Interface-confined space: NMR study of poly(hexyl ethacrylate)-block-poly(acrylic acid) and poly(dodercyl methacrylate)-block-poly(acrylic acid) micelles in D2O

The mobility of distant methyl side groups in poly(hexyl methacrylate)-block-poly(sodium acrylate) (PHMA−PAANa) and poly(dodecyl methacrylate))-block-poly(sodium acrylate) (PLMA−PAANa) micelles, dispersed in D2O and characterized by SANS, was studied using 1H single and double quantum high-resolution and MAS NMR. Transverse and rotating-frame relaxation was studied at temperatures 320−345 K in the original micellar solutions and in the systems with their viscosity gradually increased by additions of high-molecular-weight poly(ethylene oxide) and with the micellar cores gradually swollen by chlorobenzene. The relaxation data were quantitatively evaluated using a pragmatic model based on Cohen-Addad's theory. The results obtained strongly indicate that the side groups are relatively immobilized to an even higher degree than in poly(2-ethylhexyl acrylate)-block-poly(acrylic acid) micelles at the same conditions. The most immobilized groups are at or near the interface. Possible underlying effects, including penetration resistance of the surrounding water molecules, fixation of the polymer backbone at the interface, and motional correlation between the distant side group and the backbone are discussed

Structure and properties of melt-spun Al-Zr-Ti alloys 1. composition of as-melt-spun ribbons

Translated from Czech (Kovove Materialy 1999 (6) p. 386-398)Available from British Library Document Supply Centre-DSC:9023.190(9750)T / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Structure and properties of melt-spun Al-Zr-Ti alloys III phase transformations at elevated temperatures

Translated from Russian (Kovove Mater. 2000 (2) p. 77-95)SIGLEAvailable from British Library Document Supply Centre-DSC:9023.190(9833)T / BLDSC - British Library Document Supply CentreGBUnited Kingdo