Interaction forces between adsorbed polymer layers

The interaction forces between adsorbed polymer layers were investigated. Two types of graft copolymers that were adsorbed on hydrophobic surfaces have been investigated: (i) a graft copolymer consisting of polymethylmethacrylate/polymethacrylic acid back bone (the B chain) on which several poly(ethylene oxide) chains are grafted (to be referred to as PMMA/PEO_n); and (ii) a graft copolymer consisting of inulin (linear polyfructose with degree of polymerization > 23) (the A chain) on which several C₁₂ chains are grafted (INUTEC SP1). In the first case adsorbed layers of the graft copolymer were obtained on mica sheets and the interaction forces were measured using the surface force apparatus. In the second case the interaction forces were measured using Atomic Force Microscopy (AFM). For this purpose a hydrophobically modified glass sphere was attached to the tip of the cantilever of the AFM and the glass plate was also made hydrophobic. Both the sphere and the glass plate contained an adsorbed layer of INUTEC SP1.In the surface forces apparatus one essentially measures the energy E(D)–distance D curves for the graft copolymer of PMMA/PEO_n between mica surfaces bearing the graft copolymer and this could be converted to interaction energy between flat surfaces. Using the de Gennes scaling theory, it is possible to calculate the interaction energy between the polymer layers. The same graft copolymer was used in latex dispersions and the high frequency modulus G′_∝ was measured as a function of the volume fraction ? of the dispersion. This high frequency modulus could be related to the potential of mean force. In this way one could compare the results obtained from rheology and those obtained from direct measurement of interaction forces.In the AFM method, the interaction forces are measured in the contact area between two surfaces, i.e. a spherical glass particle and a glass plate. Both glass spheres and plates were hydrophobized using dichlorodimethylsilane. Results were obtained for adsorbed layers of INUTEC SP1 in water and in the presence of various concentrations of Na₂SO₄ (0.3, 0.8, 1.0 and 1.5 mol dm^{− 3}). All results showed a rapid increase of force with a decrease of separation distance and the forces were still repulsive up to the highest Na₂SO₄ concentration. This explains the high stability of dispersions when using INUTEC SP1 as stabilizer.     

Viscosities of Binary and Ternary Mixtures of Water,Alcohol, Acetone,and Hexane

This articles studied and determined the viscosities of the binary mixtures of water–methanol, water–ethanol, water–propanol, water–acetone, acetone–ethanol, methanol–ethanol, and acetone–hexane and the ternary mixtures of water–methanol–ethanol and water–ethanol–acetone at 20°C. It is shown that the mixing of water with the alcohols and acetone resulted in a positive deviation of viscosity, which reached the maximum value at the water mole fraction x ₁ ～ 0.7 for water–methanol, x ₁ ～ 0.72 for water–ethanol, x ₁ ～ 0.74 for water–propanol, and x ₁ ～ 0.83 for water–acetone binary mixture. This viscosity deviation can be mainly attributed to the formation of micelles of alcohol or acetone molecules in water because of the hydrophobic attraction between the hydrocarbon chains. The micelle surfaces are surrounded by hydration layers, leading to the positive viscosity deviation in the liquid mixtures because the water in hydration layers has a much higher viscosity than bulk water. Also, the contrary observation was found in the binary mixtures of acetone–ethanol and acetone–hexane, having a negative viscosity deviation.     

Hydrodynamic thickness and deformational properties of adsorption layers of poly(ethyleneoxides)

From the measurements of surface potentials of quartz capillaries before and after adsorption of poly(ethylene oxides) (PEO) of various molecular mass, an assessment of the equilibrium hydrodynamic thickness of the adsorption layers has been obtained. The results have been compared with those of independent measurements of . The flow of the polymer solution under increasing pressure drops at the ends of a capillary, which causes the corresponding shear stress () on the surface of adsorbed PEO layers, results in the deformation of the latter, which manifests itself in decreasing 5. The values decrease by several times when the shear stress rises to 2×10₂ N m^–2. Such values of have been obtained using thin capillaries (r = 5÷6 mm) and by application of the capillary electrokinetic method with pressure drops up to 5÷6 MPa.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 31–37, January, 1994.     

Solution Layer Deposition: A Technique for the Growth of Ultra‐Pure Manganese Oxides on Silica at Room Temperature

With the ever increasing miniaturization in microelectronic devices, new deposition techniques are required to form high‐purity metal oxide layers. Herein, we report a liquid route to specifically produce thin and conformal amorphous manganese oxide layers on silicon substrate, which can be transformed into a manganese silicate layer. The undesired insertion of carbon into the functional layers is avoided through a solution metal–organic chemistry approach named Solution Layer Deposition (SLD). The growth of a pure manganese oxide film by SLD takes place through the decoordination of ligands from a metal–organic complex in mild conditions, and coordination of the resulting metal atoms on a silica surface. The mechanism of this chemical liquid route has been elucidated by solid‐state ²⁹Si MAS NMR, XPS, SIMS, and HRTEM.     

Surface patterns of block copolymers in thin layers after vapor treatment

A systematic study of formation of surface patterns in block copolymer thin layers after their exposure to solvent vapors was performed. The studied effect involves layers of thickness approximately equal to the ordering size of polymers - about 45 nm. Experiments were performed on three styrene - methacrylate derivative block copolymers, synthesized by living anionic polymerization: poly(4-octylstyrene)-block-poly(butyl methacrylate), poly(4-fluorostyrene)-block-poly(butyl methacrylate) and poly(p-octylstyrene)-block-poly(methyl methacrylate). The polymers were exposed to vapors of chloroform, 1,4-dioxane, hexane, acetone and tetrahydrofuran.     

Charge transport and contact resistance in coplanar devices based on colloidal polyaniline dispersion

The charge transport properties of thin films prepared from colloidal dispersion of polyaniline stabilized by poly(N‐vinylpyrrolidone) (PANI/PVP) have been investigated. The electrical characterization of coplanar device comprising of gold electrodes and PANI/PVP film deposited by spin coating served to gain insights into the contact and bulk resistance. The films prepared from PANI/PVP colloidal dispersion show high stability over a large temperature range. Temperature dependent measurements in the range from 90 to 350 K reveal that the charge transport can be described by a three‐dimensional variable‐range hopping mechanism as the dominant mode in the films. The stability of the films cast from dispersion within a large temperature range opens the possibility of the application as a polymer semiconductor layer in sensors and charge‐transport interlayer in organic solar cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1710–1716     

Structure of BaGd2（MoO4）4 Crystal

The title compound belongs to monoclinic,space group C2/c with a=5.2694(1),b=12.6659(4),c=19.4108(2) ,β=91.504(2)°,V=1295.06(5) 3,Z=4 and Dc=5.599 g/cm3. The structure of BaGd2(MoO4)4 contains a MoO4 tetrahedron,a distorted GdO8 polyhedron,and Ba2+ ions in a tenfold coordination. The GdO8 polyhedra are linked together through edge-sharing to give a two-dimensional Gd layer. The MoO4 tetrahedra connected to the Gd atoms are capped up and down the Gd layer through common oxygen apices,thus forming a new Gd-Mo layer. Finally,the Gd-Mo layers are held together through bridging BaO10 polyhedra to form a three-dimensional framework. Since the Ba-μ3-O bond has a large average distance of 2.888 ,this structural characteristic will result in a cleavage along the (001) plane.     

Synthesis and Crystal Structure of Isonicotinic Acid [1-（3,5-Dibromo-2- hydroxyphenyl）methylidene]hydrazide Methanol

A new Schiff base compound, C13H9Br2N3O2·CH3OH, isonicotinic acid [1-(3,5- dibromo-2-hydroxyphenyl)methylidene]hydrazide methanol, has been synthesized and characterized by elemental analysis, IR spectra, and single-crystal X-ray diffraction. The compound comprises a Schiff base moiety isonicotinic acid [1-(3,5-dibromo-2-hydroxyphenyl) methylidene]hydrazide and a methanol molecule. The crystal belongs to the triclinic system, space group P1 with a = 8.464(1), b = 9.511(2), c = 10.901(2) , α = 92.940(2), β = 110.456(2), γ = 96.040(2)o, Z = 2, V = 814.0(2) 3, Dc = 1.759 g/cm3, Mr = 431.09, λ(MoKα) = 0.71073 , μ = 4.994 mm-1, F(000) = 424, R = 0.0440 and wR = 0.1061. A total of 3284 unique reflections were collected, of which 2197 with I > 2σ(I) were observed. The molecule adopts a trans configuration about the C=N double bond. The dihedral angle between the benzene and pyridine rings is 22.0(4)o. The crystal structure is stabilized by intermolecular O-H···N and C-H···O hydrogen bonds, forming layers parallel to the ac plane. The preliminary biological tests show that the compound has potential antibacterial activities.     

PREPARATION OF POLY（METHYL METHACRYLATE）/LAYERED DOUBLE HYDROXIDES NANOCOMPOSITES via in situ SOLUTION POLYMERIZATION

An exfoliated layered double hydroxides/poly(methyl methacrylate)(LDHs/PMMA)nanocomposite was prepared by in situ solution polymerization of methyl methacrylate(MMA)in the presence of 4-vinylbenzenesulfonate intercalated LDHs(MgAl-VBS LDHs).MgAl-VBS LDHs was prepared by the ion exchange method,and the structure and composition of the MgA1-VBS LDHs were determined by X-ray diffraction(XRD),infrared spectroscopy and elemental analysis.XRD and transmission electron microscopy(TEM)were employed to examine the structure of LDHs/PMMA nanocomposite.It was indicated that the LDHs layers were well exfoliated and dispersed in the PMMA matrix.The grafting of PMMA onto LDHs was confirmed by the extraction result and the weight fraction of grafted PMMA increased as the weight fraction of LDHs in the nanocomposites increased.     

Synthesis and Structural Characterization of a New Cadmium(Ⅱ) Complex Bridged by Endo-norbornene-cis-5,6-dicarboxylic Acid

A polynuclear complex [Cd(endc)(H2O)]n·nH2O (endc = endo-norbomene-cis5,6-dicarboxylate anion) has been synthesized by the hydrothermal reaction of cadmium nitrate tetrahydrate with endo-norbomene-cis-5,6-dicarboxylic acid in 1:1 molar ratio,and structurally characterized by single-crystal X-ray diffraction.It crystallizes in monoclinic,space group P21/c with a = 1.16471(7),b = 0.95334(7),c = 0.91109(9) nm,Z = 4,V= 1.01035(14)nm3,Dc.= 2.160 g/cm3,μ= 2.172 mm-1,F(000) = 648,R =0.0302 and wR = 0.0752.According to structural analysis,each Cd(Ⅱ) ion is coordinated to six O atoms from three endc anions and one water molecule,giving a distorted octahedral geometry.Two- dimensional layer arrangement of the title complex is constructed from the bridging nature of endc.It is worth notice that adjacent two-dimensional layers are joined together to form a three-dimensional supramolecular framework via intermolecular hydrogen bonding interactions.