Irreversible Adsorption of Polymer Melts

1996 ◽  
Vol 464 ◽  
Author(s):  
U. Sawhney ◽  
C.J. Durning ◽  
B. O'Shaughnessy ◽  
G.S. Smith ◽  
J. Majewski
Keyword(s):  
Room Temperature ◽  
Adsorbed Layer ◽  
Equilibrium Structure ◽  
Pmma Film ◽  
Irreversible Adsorption ◽  
Equilibrium Conditions ◽  
Melt Structure ◽  
Neutron Reflection ◽  
Reflection Data ◽  
Adsorbed Layers

ABSTRACTWe studied the equilibrium architecture of polymer layers strongly adsorbed from the melt. Immobilized layers of poly-(methyl methacrylate) (PMMA) were produced by the following method: 1) The polymer was spin-coated onto silanol bearing surfaces of single crystal and fused quartz, and annealed at melt conditions, 2) The annealed layer was quenched to room temperature (below the glass transition temperature) in order to “freeze in” the melt structure near the substrate, 3) Unbound material was leached away in good solvent (benzene) to leave a residual, strongly-adsorbed layer. The architecture of this layer was studied by neutron reflection. Data on dried adsorbed layers indicates a dense PMMA film whose thickness gradually increases with annealing time in the melt from a minimal value. Evidently, annealing gradually relaxes a rather flat non-equilibrium structure produced by spin-coating. The thicknesses, h, in a series of dry layers annealed long enough to achieve equilibrium conditions in the melt scale as h ∼ N1/2. Data on swollen layers suggest a dilute, extended layer, but the preliminary results cannot give a definitive confirmation of the brush structure predicted by Guiselin.11

Specular neutron reflection at the mica/water interface – irreversible adsorption of a cationic dichain surfactant

2014 ◽  
Vol 47 (5) ◽  
pp. 1638-1646 ◽  
Author(s):  
Kathryn Louise Browning ◽  
Lucy Rachael Griffin ◽  
Philipp Gutfreund ◽  
Robert David Barker ◽  
Luke Ashley Clifton ◽  
...  
Keyword(s):  
Scattering Length ◽  
Crystal Defects ◽  
Thin Layers ◽  
Water Interface ◽  
Irreversible Adsorption ◽  
Neutron Reflection ◽  
Reflection Data ◽  
Muscovite Mica ◽  
Critical Edge ◽  
Solid Liquid Interface

Neutron reflection from the important mineral mica at the solid/liquid interface is presented here using a new approach – a very thin mica crystal supported on a silicon substrate. This approach avoids the problems of crystal defects and surface undulations that have hindered previous work. The use of mica as a reflectivity substrate is important as it is a model surface, which is atomically smooth with a high structural charge. In this work the mica/water interface is fully characterized. In particular, a characteristic double critical edge is observed, arising from the higher scattering length densities of the mica and D2O subphase relative to the silicon support. The experimental data are modelled using a combined approach: conventional amplitude summation (matrix method) for the thin layers and reflected intensity summation with attenuation terms for the thick layers of mica and hydrocarbon adhesive. Reflection data from the adsorption of the dichain cationic surfactant didodecyldimethylammonium bromide (DDAB) to the surface of muscovite mica from aqueous solution are also presented. It is found that, at twice the critical micelle concentration, a bilayer of DDAB with a thickness of 24 Å is observed, containing essentially no water. Its partial removal by washing and ion exchange is also presented.

Defect Structure and Composition of Fe1-xO

1981 ◽  
Vol 39 ◽  
pp. 80-81
Author(s):  
C. Lebreton ◽  
L. W. Hobbs
Keyword(s):  
Defect Structure ◽  
Room Temperature ◽  
Imaging Techniques ◽  
Equilibrium Structure ◽  
Dark Field ◽  
Lattice Imaging ◽  
Zone Method ◽  
Equilibrium Conditions ◽  
Additional Defect ◽  
Tetrahedral Complexes

Wüstite, Fe1-xO, is the principal oxide scale formed on iron above 843 K. Wüstite exhibits a broad range of non-stoichiometry (0.05 < x < 0.15), and even in equilibrium with iron maintains a minimum 5% iron deficiency. Its large departures from stoichiometry are accommodated by octahedral iron vacancies which associate into tetrahedral complexes about ferric ion interstitials. Despite a great many studies, further details of the defect structure have been slow in coming. We report here additional defect microstructure information for wüstite in equilibrium conditions and after annealing below the 843 K eutectoid, as revealed by electron diffraction, high-resolution dark-field and lattice-imaging techniques.Single crystals, prepared by a floating-zone method, were equilibrated within the wüstite phase field in CO/CO2 atmospheres providing controlled oxygen fugacity. Samples were oil-quenched so that they reached room temperature within a few seconds and are therefore expected to have retained the initial equilibrium structure.

Neutron Reflection Study of Phenol Adsorbed at the Surface of Its Aqueous Solutions:  An Unusual Adsorbed Layer

1998 ◽  
Vol 102 (1) ◽  
pp. 185-192 ◽  
Author(s):  
Z. X. Li ◽  
R. K. Thomas ◽  
A. R. Rennie ◽  
J. Penfold
Keyword(s):  
Aqueous Solutions ◽  
Adsorbed Layer ◽  
Neutron Reflection

Electrocaloric Effect of (110) Oriented KNbO3 Film

2021 ◽  
Vol 21 (10) ◽  
pp. 5247-5252
Author(s):  
MinYa Jin ◽  
JianHua Qiu ◽  
ZhiHui Chen ◽  
XiuQin Wang ◽  
NingYi Yuan ◽  
...  
Keyword(s):  
Electric Field ◽  
Thermodynamic Equilibrium ◽  
Thermodynamic Potential ◽  
Room Temperature ◽  
Misfit Strain ◽  
Equilibrium Conditions ◽  
Electrocaloric Effect ◽  
Phase Map ◽  
The Stability

The room temperature electrocaloric effect is researched for (110) oriented KNbO3 film based on Landau-Devonshire theory. The phase map with different ferroelectric states is built at room temperature with the considerations of thermodynamic equilibrium conditions and minimum of thermodynamic potential. Five ferroelectric structural phases are obtained theoretically. The negative in-plane misfit strains are conducive to form the tetragonal c phase and the positive strains are in favor of the stability of tetragonal a1 and a2 phases. The electrocaloric effect relies on both misfit strain and electric field. Moreover, large electrocaloric effect is achieved in the orthorhombic phases.

scholarly journals Electrodynamic balance measurements of thermodynamic, kinetic, and optical aerosol properties inaccessible to bulk methods

2015 ◽  
Vol 8 (6) ◽  
pp. 2397-2408 ◽  
Author(s):  
S. S. Steimer ◽  
U. K. Krieger ◽  
Y.-F. Te ◽  
D. M. Lienhard ◽  
A. J. Huisman ◽  
...  
Keyword(s):  
Refractive Index ◽  
Light Scattering ◽  
Room Temperature ◽  
Shikimic Acid ◽  
Resonance Spectroscopy ◽  
Equilibrium Conditions ◽  
Electrodynamic Balance ◽  
Mie Resonance ◽  
Water Diffusivity ◽  
Activity Density

Abstract. Measurements of a single, levitated particle in an electrodynamic balance are an established tool for deriving thermodynamic and material data such as density, refractive index and activities of components of an aqueous solution under supersaturated conditions, where bulk measurements are not possible. The retrieval relies on combining mass-to-charge data and size data from light scattering. Here, we use a combination of low- and high-resolution Mie resonance spectroscopy to obtain radius data, enabling an accurate size determination not only when the particle is in equilibrium, but also when it is out of equilibrium due to kinetic limitation of mass transport. With the data measured under non-equilibrium conditions, it is possible to retrieve the water diffusivity. A challenge is that the radius retrieval by comparing measured light scattering with Mie theory requires the knowledge of refractive index as a function of concentration. Here, we show an iterative retrieval of refractive index and size for compounds for which data cannot be obtained in the bulk either due to lack of sufficient amounts of sample or limited solubility. We demonstrate the measurement strategy and the retrieval of water activity, density, refractive index and water diffusivity for aqueous shikimic acid. Water diffusivity in concentrated shikimic acid decreases by 6 orders of magnitude at 250 K compared to that at room temperature.

Investigation of Polymer Brushes and Adsorbed Layers under Shear

1997 ◽  
Vol 30 (5) ◽  
pp. 680-683 ◽  
Author(s):  
D. Nguyen ◽  
C. J. Clarke ◽  
A. Eisenberg ◽  
M. H. Rafailovich ◽  
J. Sokolov ◽  
...  
Keyword(s):  
Shear Rate ◽  
Polymer Brushes ◽  
Adsorbed Layer ◽  
Random Copolymer ◽  
Neutron Reflectometry ◽  
Recent Theory ◽  
Observable Effect ◽  
Density Profiles ◽  
Adsorbed Polymer ◽  
Adsorbed Layers

Neutron reflectometry was used to investigate the density profiles of polymer brushes and an adsorbed polymer layer under shear. The brushes consisted of end-functionalized deuterated polystyrene. The adsorbed polymer was a random copolymer of deuterated styrene and 4-vinylpyridine. The brush and the adsorbed layer were sheared by the flowing of solvents over the polymer, with a maximum shear rate of 104s−1. Density profiles of the brush and the layer were determined before, during and after shear. The shear had no observable effect on the polymer profiles in any of the experiments. We discuss these results in the context of other experiments and a recent theory.

Structure of an Adsorbed Layer ofn-Dodecyl-N,N-dimethylamino Acetate at the Air/Solution Interface As Determined by Neutron Reflection

1997 ◽  
Vol 101 (36) ◽  
pp. 7121-7126 ◽  
Author(s):  
J. D. Hines ◽  
P. R. Garrett ◽  
G. K. Rennie ◽  
R. K. Thomas ◽  
J. Penfold
Keyword(s):  
Adsorbed Layer ◽  
Neutron Reflection ◽  
Solution Interface

Electrochemical Atomic Layer Deposition and Characterization of CdTe and PbTe Thin Films

2015 ◽  
Vol 31 ◽  
pp. 30-39 ◽  
Author(s):  
Amal Kabalan ◽  
Pritpal Singh
Keyword(s):  
Room Temperature ◽  
Atomic Layer ◽  
Flow Cell ◽  
X Ray ◽  
Optical Reflection ◽  
Reflection Data ◽  
Layer Deposition ◽  
Glancing Angle ◽  
Layer Flow

This study reports the cycle chemistries involved in depositing CdTe and PbTe nanofilms. An automated thin-layer flow cell electrodeposition system was used to deposit the films at room temperature. Cyclic voltammetry was used to study the Underpotential Deposition (UPD) of the compounds. The monolayer/cycle deposition rate was also monitored in order to insure that the film is depositing at a uniform rate. The chemical composition of the films was characterized using Energy-Dispersive X-ray Spectroscopy (EDS) on a Scanning Electron Microscope (SEM). The crystallinity of the films was studied using a glancing angle X-ray diffractometer. The bandgaps of the films were calculated using measured optical reflection data.

Giant Magnetoresistance in Single Layer and Multilayer Phase Separating Alloy Films

1993 ◽  
Vol 313 ◽  
Author(s):  
S. Hossain ◽  
A. Waknis ◽  
D. Seale ◽  
M. Tan ◽  
M.R. Parker ◽  
...  
Keyword(s):  
Thin Films ◽  
Field Dependence ◽  
Giant Magnetoresistance ◽  
Room Temperature ◽  
Single Layer ◽  
Multilayer Films ◽  
Equilibrium Conditions ◽  
Ferromagnetic Layers ◽  
Novel Processing ◽  
New Phase

ABSTRACTThe phenomenon of giant magnetoresistance (GMR), previously measured only in multilayer films comprising ferromagnetic layers separated by nonmagnetic spacers, has recently been observed in single layer ‘granular’ alloy thin films prepared by cosputtering a ferromagnet and a nonmagnet which tend to phase separate (cluster) under equilibrium conditions. We have systematically studied the magnetoresistance of two new phase separating GMR systems (Ni66Fe16Co18-Ag and Co9oFelo-Ag) both of which exhibit large room temperature GMR (>11% and >14%, respectively). We have also attempted to influence the details of the field dependence of the magnetoresistance in the previously studied Co-Ag system by employing novel processing methods including interrupted sputtering and layering of the Co-Ag alloy with Cu spacers.

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