Different Degrees Of Hydrophilicity Research Articles

Investigation into the Heterocoagulation of Two-Component Disperse Systems Containing Nanosized and Submicron Particles with Different Degrees of Hydrophilicity

The aggregate stability of binary mixtures that contain two hydrophobic components [SiO2-FeOOH, Au-Fe(OH)3], hydrophobic and hydrophilic components (SiO2-ZrO2, SiO2-CeO2, FeOOH-natural diamond), and two hydrophilic components (CeO2-natural diamond, ZrO2-natural diamond) is investigated by photometry and ultramicroscopy over wide ranges of KCl concentrations and pH. It is shown that the stability of binary mixtures containing one or two hydrophobic components can be qualitatively explained in terms of the Derjaguin theory of heterocoagulation of hydrophobic colloids. The stability of mixed binary sols is determined by the stability of the component with a dominant number concentration of particles. The heteroadagulation stabilization due to the ionic electrostatic or structural stability ratio of the nanosized component in the mixture is revealed.

Effect of hydrophilicity on fouling of an emulsified oil wastewater with PVDF/PMMA membranes

Membranes with different degrees of hydrophilicity were prepared from PVDF and PMMA. The hydrophilicity was determined by using the contact angle technique. The distribution of pore radius was obtained from polydispersed solute permeation, scanning electron microscope (SEM) and hydraulic permeability. A higher hydrophilic character with the increase of PMMA in the casting solution and the appearance of larger macrovoids in the porous substructure were found without a substantial modification of the selective surface structure. However, a significant effect of compaction was evidenced due to the transmembrane pressure on membranes with high content of PMMA. An effluent from an engine factory was used to study the ultrafiltration performance of the prepared membranes. These assays show that membranes with a higher content of PMMA lead to a lower fouling.

Water sorption properties of poly(ethyl acrylate‐co‐hydroxyethyl methacrylate) macroporous hydrogels

AbstractSynthetic porous hydrogels are becoming more and more important in the field of biomaterials. Different studies demonstrate that the porous structure promotes the colonisation of living cells and improves the biocompatibility of the implants. The macroporous structure allows not only the control of cellular ingrowth morphology but also the mechanical integration and the regulation of nutrient and hydraulic flow in the hydrogel. In this work poly(ethyl acrylate‐co‐hydroxyethyl methacrylate) (PEA/PHEMA) copolymers were polymerized using 2% of ethylene glycol dimethacrylate as cross‐linking agent and azoiso‐botyronitrile as initiator. Five samples were prepared with the EA/HEMA weight ratios of 75/25, 50/50, 25/75 and pure PEA and PHEMA polymers, obtaining different degrees of hydrophilicity. The macroporous structure was obtained by adding poly(acrylonitrile) fibres to the monomers. After polymerization the fibres were eliminated by dissolution in dimethyl formamide. The holes are cylinders of approximately 40μm diameter and are all, more or less, in the same direction, although they are not uniformly distributed. Water sorption isotherms and diffusion properties of the macroporous samples are compared with the samples without holes.

Thermoplastic polymers as modifiers for urea‐formaldehyde (UF) wood adhesives. I. Procedures for the preparation and characterization of thermoplastic‐modified UF suspensions

AbstractAcrylic thermoplastic copolymers with different degrees of hydrophilicity were prepared and introduced into a commercial aqueous urea‐formaldehyde (UF) suspension at 5–10% w/v. The most hydrophilic acrylic thermoplastic was introduced into the UF suspension as an aqueous solution, whereas the most hydrophobic acrylic was introduced as a surfactant‐stabilized suspension. Acrylics with intermediate hydrophilicity were introduced into the UF suspension as a self‐dispersed aqueous suspension. The thermoplastic‐modified UF suspensions with 5% thermoplastic (58% solids) had a viscosity at 30°C of ∼ 114 cP, compared with a viscosity of ∼112 cP for the original UF suspension (60% UF solids). At 10% thermoplastic (63% solids), all the thermoplastic‐modified UF suspensions exceeded 200 cP. The viscosity of the UF suspension modified with self‐dispersed thermoplastic was reduced by ∼ 50% by reducing the thermoplastic molecular weight. SEM micrographs of cured thermoplastic‐modified UF showed phase‐separated thermoplastic domains in a continuous UF phase for the UF modified with self‐dispersed and surfactant‐stabilized thermoplastic, but UF modified with the water‐soluble thermoplastic showed a single phase. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 890–897, 2003

Molecular Dynamics Study of Spherical Aggregates of Chain Molecules at Different Degrees of Hydrophilicity in Water Solution

We present molecular dynamics simulations of three spherical aggregates constituted of the same number of monomeric chains of increasing hydrophilic character in water solution. The three different chains are dodecane, CH3(CH2)10CH3; dodecan-1-ol, CH3(CH2)10CH2OH; and oligoethylenoxide, CH3(CH2)11(OCH2CH2)3OH, and the systems are denoted C12, C12E0, and C12E3, respectively. The three solutions are simulated at the same temperature and pressure and at about the same concentration in weight of the solute. We investigate the structural changes of the aggregate and the conformational changes of its chains after increasing the hydrophilicity of the monomers. In the C12 system, the density of the aggregate is higher than the density of the pure hydrocarbon liquid in the same thermodynamic conditions. Dodecane chains are quite rigid and mostly in the all-trans conformation. This is an effect of the strong hydrophobic repulsion exerted on the aggregate by the water. A density depletion develops at the interface between the oil core and the solvent because of the mismatch between the two components. This extra pressure is gradually released after increasing the hydrophilicity of the monomers. In the C12E3 system, the density depletion at the interface is completely canceled, and the system is homogeneous through the interface. In this system, the interfacial regions appear to be divided into an inner part, where methylene groups, oxyethylene groups, and water molecules are present, and into an outer region formed by a mixture of oxyethylene groups and water only. The local density of oxyethylene groups in the interfacial region is strongly fluctuating, and its histogram shows an effective attraction among those groups. Thus, a considerable portion of the interfacial volume is filled by the solvent only. We observe a strong tendency for the OCCO dihedrals in the hydrophilic tails to be in the gauche state, and at the same time, we observe the presence of H-bond bridges that stabilize this structure.

Study of blood compatible polymers II. Poly( N, N-disubstituted) acrylamides

Poly( N, N-disubstituted) acrylamides with both hydrophilic and hydrophobic groups as substituants were synthesized. Different degrees of hydrophilicity were achieved by varying the bulk of the hydrophobic substituent. N-alkyl, N-(2-hydroxyethyl) acrylamides with alkyl substituents propyl (PROPAAm), octyl (OCTAAm) and benzyl (BENAAm) were synthesized. The swelling capacity of the polymers decreased with increase in bulk of the hydrophobic substituent. In vitro studies showed that the surfaces of these polymers did not induce platelet aggregation. Cell compatibility of these polymers was assessed by following the growth of human umbilical cord fibroblast cells. Pronounced cell growth and spreading was observed on the surfaces of polyOCTAAm and polyBENAAm. The relatively low cell growth on polyPROPAAm was ascribed to its high water content.

Immobilisation du complexe de nickel de l'histidine L(+) sur des supports macromoléculaires hydrophiles

AbstractN‐(4‐vinylbenzyl)‐L‐histidine (5) and the corresponding methyl ester were synthesized by reacting L‐histidine or L‐histidine methyl ester with 4‐formylstyrene. N‐(4‐vinylbenzyl)‐L‐histidine methyl ester was radically copolymerized with various amounts of 2‐hydroxyethyl methacrylate and ethylene dimethacrylate, leading to resins of different degrees of hydrophilicity and crosslinking. After saponification of the histidine ester groups, the resins were chelated with Ni2+ salt in order to be used as polymeric catalysts in enantioselective ester hydrolysis reactions.