Magnetic Field Dependence of the Ultrasonic Attenuation and Resistance of a Superconducting Granular Lead Film

Schmidt, J.; Schenstrom, A.; Levy, M.

doi:10.1051/jphyscol:198510156

Cited by 36 publications

(25 citation statements)

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“…The situation at the Si interface is far less clear and is affected by the nature of the Si surface, i.e., if it is the native oxide or if it is passivated with HF . If it is assumed that the segregation at both interfaces (air and substrate) is similar to that predicted at the air surface by the mean-field theory of Schmidt and Binder with surface energy parameters from ref , the maximum shift in the phase separation temperature can be estimated. The film was modeled by layers of homogeneous composition parallel to the film surface with incremental changes in the composition between layers used to approximate the composition profile normal to the surface as predicted by Schmidt and Binder.…”

Section: Resultsmentioning

confidence: 99%

Small-Angle Neutron Scattering Studies on Thin Films of Isotopic Polystyrene Blends

Ho¹,

Briber²,

Jones³

et al. 1998

Macromolecules

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Thin films of various thicknesses ranging from 100 µm down to 1390 Å of an isotopic polystyrene blend were examined using small-angle neutron scattering. It was found that absolute scattering data with reasonable signal-to-noise could be obtained from single films as thin as 1390 Å supported on single-crystal Si wafers by optimizing the neutron optics and by carefully eliminating background arising from the substrate. The wave vector dependence of the neutron scattering from all of the films examined could be described using the random phase approximation with the same FloryHuggins interaction parameter and R G values as found in the bulk. No dependence of the scattering on film thickness was found. These results demonstrate that quantitative small-angle neutron scattering measurements can be obtained from single ultrathin films of polymer mixtures.

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Section: Resultsmentioning

confidence: 99%

Small-Angle Neutron Scattering Studies on Thin Films of Isotopic Polystyrene Blends

Ho¹,

Briber²,

Jones³

et al. 1998

Macromolecules

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“…Spinodal decomposition of polymer blends leading to patterned phase morphologies in the bulk is a fascinating subject that has been studied for the past two decades. − More recently, it has been realized that the presence of a surface breaks the rotational and translational symmetry, thus strongly altering both the equilibrium phase morphology and the phase separation kinetics. − Binary mixtures of polymers (for example, deuterated poly(ethylene propylene) (dPEP) and poly(ethylene propylene (hPEP)) are useful model systems to study these effects. For example, in a film of a two-phase isotopic polymer blend on a silicon substrate, preferential adsorption of the dPEP component to the surface and hPEP to the silicon leads to the formation of a macroscopic bilayer with the dPEP-rich phase wetting the surface and the hPEP-rich phase wetting the silicon. , In the early stages oscillatory composition profiles originate from both the surface and the substrate and propagate into the bulk of the film. − For compositions near the critical value, the wetting layer thickens as a + bt 1/3 where t is the time after the quench, consistent with a process controlled by diffusive material exchange across the layer. , For off-critical quenches where the majority component wets the surface, the wetting layer grows faster, its thickness increasing approximately linearly with t . These kinetics are attributed to hydrodynamic transport by flow of dPEP through a perforated layer of hPEP-rich domains just below the dPEP-rich wetting layer. − …”

Section: Introductionmentioning

confidence: 99%

Spinodal Decomposition in a Subsurface Layer of a Polymer Blend Film

et al. 1999

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We have studied phase separation in off-critical mixtures of poly(ethylene propylene) (hPEP) and perdeuterated poly(ethylene propylene) (dPEP) inside the metastable and unstable region of the phase diagram but under the influence of a surface that attracts the majority component (dPEP). In the adjacent depletion region nucleation barriers are eliminated, and the film starts to phase separate long before phase separation occurs in the bulk. The hPEP-rich domains are confined to grow anisotropically within the unstable region. The growth gives rise to the formation of a regular roughness pattern on the surface when the domains relax into a more circular shape driven by interfacial tension. The volume fraction versus depth profiles are obtained using time-of-flight forward recoil spectrometry (TOF-FRES) while the roughness pattern that mirrors the phase morphology in the depletion layer can be monitored by scanning force microscopy (SFM). Depending on initial dPEP volume fraction the lateral bicontinuous phase pattern inside the unstable region either develops into a dPEP-rich layer containing hPEP-rich droplets or forms a continuous hPEP-rich layer with dPEP-rich droplets. The lateral growth of the pattern follows a λ(t) ) λ(t)0) + bt 0.80 law where λ(t)0) and λ(t) are the pattern wavelength initially and at time t after the quench.

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“…The surface chemical composition of polymer blends has been extensively investigated in the past decade, both experimentally − and theoritically. − Most studies revealed that the lower surface free energy γ component was enriched at the air−polymer interface in order to minimize the magnitude of interfacial free energy. For instance, in the case of the miscible polystyrene/poly(vinyl methyl ether) (PS/PVME) blend film, X-ray photoelectron spectroscopic (XPS) and surface tension measurements revealed that the surface was covered with PVME chains with lower γ. , Also, in the case of the (PS/deuterated PS) blend film, it was revealed from dynamic secondary ion mass spectroscopic (DSIMS) and forward recoil elastic scattering (FRES) measurements that deuterated PS was preferentially segregated at the film surface, since the magnitude of γ for deuterated PS is lower than that of PS due to the lower polarizability of the C−D bond compared with that of the C−H one …”

Section: Introductionmentioning

confidence: 99%

Surface Molecular Aggregation Structure and Surface Molecular Motions of High-Molecular-Weight Polystyrene/Low-Molecular-Weight Poly(methyl methacrylate) Blend Films

1998

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Surface molecular aggregation structure and surface molecular motions of high-molecular-weight polystyrene/low-molecular-weight poly(methyl methacrylate) (HMW-PS/LMW-PMMA) blend films were investigated on the basis of X-ray photoelectron spectroscopic measurements and scanning force microscopic observations. Monodisperse PS with M n = 1450k, where M n denotes the number-average molecular-weight, and monodisperse PMMAs with M n 1.2k, 4.2k, 40.5k, 144k, and 387k were used as HMW-PS and LMW-PMMAs, respectively. Static contact angle measurements revealed that the magnitudes of surface free energy, γ, of PMMAs for all M ns studied here were higher than that of PS with M n = 1450K. In the case of the (HMW-PS/LMW-PMMA) blend films, in which the M n for each PMMA was less than 144K, PMMA was preferentially segregated at the air−polymer interface, even though PMMA had a main chain with a higher γ compared with that of PS. It was found from scanning viscoelasticity microscopic measurements that the surface molecular motion of the (PS with M n = 1450k/PMMA with M n = 4.2k) blend film was fairly activated in comparison with that of the bulk one due to the surface segregation of LMW-PMMA. The surface enrichment of LMW-PMMA can be explained by enthalpic and entropic terms as follows. (1) Since the magnitudes of γ of both chain end groups of a polymer chain synthesized by an ordinary living anionic polymerization are smaller than that of the main chain part, the chain end groups are preferentially segregated at the surface. Therefore, the chain end effect at the air−polymer interface becomes more remarkable with a decrease of M n, due to an increases in the number density of chain end groups. (2) Since polymeric chains existing in a surface region are compressed along the direction perpendicular to the film surface, the surface chains take smaller conformational entropy in a confined state compared with that of bulk chains. The difference in conformational entropy between the surface chain and the bulk one, that is, the conformational entropic penalty of the polymeric chain at the surface, decreases with a decrease in M n. Then, when the enthalpic and entropic effects mentioned above overcome the γ difference of main chain parts between PS and PMMA, PMMA with higher γ is stably enriched at the blend film surface.

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Magnetic Field Dependence of the Ultrasonic Attenuation and Resistance of a Superconducting Granular Lead Film

Cited by 36 publications

References 0 publications

Small-Angle Neutron Scattering Studies on Thin Films of Isotopic Polystyrene Blends

Small-Angle Neutron Scattering Studies on Thin Films of Isotopic Polystyrene Blends

Spinodal Decomposition in a Subsurface Layer of a Polymer Blend Film

Surface Molecular Aggregation Structure and Surface Molecular Motions of High-Molecular-Weight Polystyrene/Low-Molecular-Weight Poly(methyl methacrylate) Blend Films

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