Search results for " Coatings and Film"
showing 10 items of 2323 documents
Butene Isomerization and Double-Bond Migration on the H-ZSM-5 Outer Surface: A Density Functional Theory Study
2011
Isomerization of trans-but-2-ene to cis-but-2-ene and double bond migration of trans-but-2-ene to but-1-ene have been investigated by means of density functional theory calculations on a suitable model of H-ZSM-5 surface. The study has been afforded on outer surface sites by considering the hydroxyl group of either a SiO2(OH)2 or a AlO2H(OH)2 moiety. On these outer surface sites, one alkoxide species occurs as a stable intermediate both along the isomerization and double bond migration pathways. The latter process could also occur via a single-step mechanism, which involves a six-center transition state. The energy barriers of the outer surface processes above do not take any advantage by t…
Phase Separation and Nematic Order in Lyotropic Solutions: Two Types of Polymers with Different Stiffnesses in a Common Solvent
2021
The interplay of the isotropic-nematic transition and phase separation in lyotropic solutions of two types of semiflexible macromolecules with pronounced difference in chain stiffness is studied by Density Functional Theory and Molecular Dynamics simulations. While the width of the isotropic-nematic two-phase coexistence region is narrow for solutions with a single type of semiflexible chain, the two-phase coexistence region widens for solutions containing two types of chains with rather disparate stiffness. In the nematic phase, both types of chains contribute to the nematic order, with intermediate values of the order parameter compared to the corresponding single component solutions. As …
Homocoupling of terminal alkynes on calcite (10.4)
2018
Abstract On-surface synthesis has been identified as highly versatile strategy to prepare molecular structures on surfaces with single-atom precision. Inspired by the classical Glaser coupling, homocoupling of terminal alkynes has attracted great attention for on-surface synthesis. This coupling is known for providing a rigid and linear linkage, which is highly interesting for the synthesis of molecular wires. For molecular wire formation, non-conductive substrates are needed for electronic decoupling. So far, however, coupling of terminal alkynes has not been performed on a bulk insulator surface. Here, we present an atomic force microscopy study, indicating that 4,4″-diethynyl-[1,1′:4′,1″…
Effect of carboxymethyl cellulose concentration on rheological behavior of milk and aqueous systems. A creep and recovery study
2009
Carboxymethyl cellulose (CMC) is an anionic polysaccharide used mainly as stabilizer and thickener agent. The purpose of this study was to investigate the effect of CMC concentration on viscoelasticity of dairy and aqueous model systems through the analysis of creep and recovery tests. The viscoelastic properties of different concentrations of CMC (0.75, 1.00, 1.25, and 1.50% w/w) in two milk systems (skimmed milk and whole milk) were compared with those of the same concentration of biopolymer in aqueous solution. Creep curves were fitted to a six parameter mechanical model (Burger + Kelvin-Voigt), whereas an empirical equation was used for recovery. The creep and recovery properties of sam…
Micropatterning of neurons using organic substrates in culture
1997
Abstract In this study, we have used spatially defined surfaces of organic thin films to micropattern the outgrowth of central nervous system neurons in culture. Glass substrates were first chemically modified with synthetic peptides derived from an extra-cellular matrix protein laminin to couple a functionality that promotes a neuron-substrate interaction. The modification procedure was verified using X-ray photoelectron spectroscopy. The functionality of the modified glass surfaces was examined by growing neurons dissociated from mammalian central nervous tissues in culture. Spatially defined surfaces of the peptide were then fabricated by selectively attaching the peptide to coplanar sur…
Self-organization of amphiphilic N-acylated linear polyethyleneimines: investigation of a reversible monolayer collapse
1996
Abstract Poly-N-4-decyloxybenzoylethyleneimine, highly crystalline in bulk, forms a stable monolayer at the air-water interface which undergoes a reversible collapse into a probable bilayer structure at higher surface pressures. We achieved transfer both from the monolayer and “bilayer” region of the polymer film at the water surface onto hydrophilic and hydrophobized quartz supports. Based on X-ray investigations on the deposited Langmuir-Blodgett films, a possible mechanism for the reversible collapse is proposed.
Unmixing of Polymer Blends Confined in Ultrathin Films: Crossover between Two-Dimensional and Three-Dimensional Behavior
2006
The interplay between chain conformations and phase separation in binary symmetric polymer mixtures confined into thin films by "neutral" hard walls (i.e., walls that do not preferentially attract or repel one of the two components of the mixture) is studied by Monte Carlo simulations. Using the bond fluctuation model on a simple cubic lattice in the semi grand canonical ensemble, we locate the critical temperature of demixing via finite size scaling methods for a wide range of chain lengths (16/= N/= 256 effective monomers per chain) and film thicknesses (2/= D/= 19 lattice spacings). Simultaneously, we investigate the geometrical structure of the chains, showing that despite using melt de…
Electrical Voltage Control of the Pressure-Induced Spin Transition at Room Temperature in the Microporous 3D Polymer [Fe(pz)Pt(CN)4]
2019
Fine control and direct monitoring of the spin crossover properties driven by pressure at room temperature are reported for the porous three-dimensional coordination polymer {Fe(pz)[Pt(CN)4]} by us...
Perovskite solar cells prepared by flash evaporation
2015
A simple vacuum deposition method for the preparation of high quality hybrid organic-inorganic methylammonium lead iodide perovskite thin films is reported. When sandwiched in between organic charge transporting layers, such films lead to solar cells with a power conversion efficiency of 12.2%.
Solvent Determines Nature of Effective Interactions between Nanoparticles in Polymer Brushes
2015
We study the effective interaction between two parallel rod-like nanoparticles in swollen and collapsed polymer brushes as a function of penetration depth by 2D self-consistent field calculations. In vertical direction, the interaction is always attractive. In lateral direction, the behavior under good and poor solvent conditions is qualitatively different. In swollen brushes (good solvent), nanoparticles always repel each other. In collapsed brushes (poor solvent), we identify two different regimes: an immersed regime, where the nanoparticles are fully surrounded by the brush, and an interfacial regime, where they are located in the interface between brush and solvent. In the immersed regi…