Local motion in the beta-transition range of partially crystalline polyethylene studied by neutron scattering

We have performed inelastic neutron scattering experiments on protonated and fully deuterated partially crystalline polyethylene. Using a high-resolution, three-axes spectrometer with an energy resolution of 80 mu eV, it was possible to detect a quasielastic process in the dynamic structure factor with a FWHM of 0.3meV. This process was shown to be active above T-0 = 260 K and its FWHM was nearly independent of temperature and scattering vector. The spatial extent of the underlying motional process was determined from the corresponding Debye-Waller factor. The mean squared displacement increases strongly with T above T-0 up to 4 Angstrom(2) at T = 380 K. Comparison with results from similar work on fully amorphous polymers suggests to relate T-0 to the glass transition of the amorphous phase in partially crystalline polyethylene. The coherent structure factor shows no evidence for a significant contribution of correlated motion to the process. A speculative explanation of the observed phenomenon as a non-equilibrium soft-mode is proposed

Domain structure and crystallization in a blend of a PE-PEO diblock copolymer and an epoxy resin

A series of blends of a PE-PEO diblock copolymer (M=1400) with a bisphenol A-type expoxy resin (ER) is studied in the full range of composition. Curing of the mixture was done at T = 110? C. DSC shows well separated melting peaks for both blocks of the copolymer. The ER rich samples only show the melting of the PE domains. The structure of the copolymer is investigated with SAXS. It shows a lamellar microphase separated structure at room temperature and disorder at high T. In the blends a sequence of structures is found with decreasing fraction of the copolymer. The ER is swelling the PEO domains thus increasing the lamellar period. Heterogeneous structures are found at intermediate compositions. Samples with small fraction of copolymer are characterized as micellar structures. Several models are applied to describe the SAXS results. The lamellar as well as the micellar structures are quantitatively described. The intermediate range is heterogeneous displaying structure on an hierarchy of length scales

Dielectric and IR spectroscopy of the macromolecular reaction of anhydridization in a functionalized side-chain liquid crystalline copolymer containing acrylic acid groups

The anhydrization reaction has been investigated in functionalized side-chain random liquid crystalline (LC) copolymers containing cyanobiphenyl mesogenic and acrylic acid (38 mol %) groups. Heat treatment of the LC copolymer at 130 degreesC for 5-200 h is accompanied by formation of intra- and intermolecular anhydrides and network structures causing an increase of the glass transition and clearing temperatures. The influence of annealing on the reorientational dynamics of the copolymers was investigated by broad-band dielectric relaxation spectroscopy. The local dynamics of the side group involving spacer motion (gamma relaxation) and mesogen rotation about the long axis (beta relaxation) do not depend on the annealing time. At the same time a considerable (more than 2 orders of magnitude) decrease in the relaxation rates of the cooperative delta and alpha processes was observed due to a gradual increase in the main-chain rigidity during the annealing. The molecular mechanism of all relaxation processes detected is discussed

The Static and Dynamic Structure Factor of a Diblock Copolymer Melt via Small-Angle X-ray Scattering and X-ray Photon Correlation Spectroscopy

We present a detailed X-ray scattering study of the static and dynamic behavior of a styrene–isoprene diblock copolymer melt with a styrene volume fraction of 0.3468. At 115 and 120 °C, we observe splitting of the principal Bragg peak, which we attribute to phase coexistence of hexagonal cylindrical and cubic double-gyroid structure. In the disordered phase, above 130 °C, we have characterized the dynamics of composition fluctuations via X-ray photon correlation spectroscopy. Near the peak of the static structure factor, these fluctuations show stretched-exponential relaxations, characterized by a stretching exponent of about 0.36 for a range of temperatures immediately above the MST. The corresponding characteristic relaxation times vary exponentially with temperature, changing by a factor of 2 for each 2 °C change in temperature. At low wavevectors, the measured relaxations are diffusive with relaxation times that change by a factor of 2 for each 8 °C change in temperature