Amount Of Hydrophobic Groups Research Articles

A facile approach to fabricate self-cleaning paint

A self-cleaning paint was developed by adding palygorskite (Pal) modified by amino silicon oil (ASO) and aminopropyltriethoxysilane (APTES) to traditional paint (TP). Therein, ASO and APTES could effectively make a Pal form with plenty of nano-clusters, and significantly increase the roughness and amount of hydrophobic groups on the surface of Pal. After this modification, the originally hydrophilic Pal was superhydrophobic and could be used as an effective hydrophobic agent to change the hydrophilic paint to super-hydrophobic one with high self-cleaning ability. This work provides a facile approach to fabricate a self-cleaning paint so as to significantly save the labor and lower the cost.

Interaction of Anionic Polyacrylamide with Cationic Surfactants

It is noteworthy that the hydrophobically associating acrylamide copolymer is a new class of watersoluble polymers,derived from polyacrylamide by introducing a relatively low amount of hydrophobic groups( generally less than 5%,molar fraction) in polymer hydrophilic macromolecule chains. Because of special pro-perties of temperature resistance,salt tolerance,resistance to shear and storage stability,the material has been widely used in industry. The water-soluble negatively charged polyacrylamide was prepared by free radical copolymerization method. The interaction between cationic surfactants and polyacrylamide was researched in aqueous solution and Na Cl solution including solubility,viscosity and rheological properties.

Synthesis and solution properties of novel comb-shaped acrylamide copolymers

An amphiphilic macro-monomer of allyl polyoxyethylene-12 ether with butyl-end group (AE12B) was synthesized, and its chemical structure was characterized. AE12B and the other two macro-monomers with different hydrophobic and hydrophilic groups were copolymerized with acrylamide to prepare the novel comb-shaped acrylamide copolymer (CPAM) through aqueous free radical polymerization. The solution properties of CPAM with different side-chain lengths were studied and compared with those of partially hydrolyzed polyacrylamide (HPAM). The experimental results show that the obtained CPAM, compared to HPAM, exhibited a dramatic enhancement in the heat- and salt-resistant properties. In addition, the increase of the side-chain length and the amount of hydrophobic groups in the side-chain improved the thickening properties of CPAM solution under high temperature and high mineralization conditions. Among the investigated macro-monomers, AE12B was optimized for the enhanced thickening properties of the CPAM solution.

Synthesis of associating poly(acrylic acid) in supercritical carbon dioxide and its solution properties

Hydrophobically associating polymers have been synthesized in supercritical carbon dioxide by copolymerization of acrylic acid with different amounts of acrylate with hydrocarbon or fluorocarbon groups. It was found that conversion of hydrocarbon comonomers was above 95% whereas that for fluorocarbon comonomers was only about 50%. In addition, large amounts of hydrophobic groups could be easily introduced to poly(acrylic acid) by reaction in supercritical carbon dioxide. The solution properties were investigated by rheology. The results indicated that intermolecular association of the copolymer was strong and viscosity was maximum under acidic conditions. In aqueous solutions fluorocarbon hydrophobes associated much more strongly than the hydrocarbon variety, but the viscosifying effect of PAAC-18 series copolymers in 2% (w/w) solution was more pronounced than that of the PAAF series, results which did not agree with the conclusions of Ravey and Stebe. It was also found that the thixotropy behavior of copolymer solution at pH 3.2 was more complex than that at pH 5.0, at which pseudoplasticity only was observed for solutions of all copolymers. Contact angles of copolymer solutions on a glass sheet were measured. The data indicated that contact angles of hydrocarbon-modified polymers were smaller than those of fluorocarbon analogues. As time passed the contact angle became smaller and smaller. Fluorocarbon analogues were better than hydrocarbon analogues, and longer hydrophobic chains were better than shorter chains, at maintaining the hydrophobic character of the surface.

Emulsifying properties of neutral and ionic polymer surfactants based on dextran

The emulsifying properties of neutral and anionic polymer surfactants derived from dextran (a neutral polysaccharide) are described. The kinetics of interfacial tension lowering by the amphiphilic polymers is first characterized by the use of semi-empirical equations. These equations allow the determination of the equilibrium value of surface tension by extrapolation to infinite time. Oil-in-water emulsions are prepared by sonication in the presence of the polymers previously dissolved in the aqueous phase. The average droplet size of the emulsions is determined immediately after preparation and followed during several weeks. Ageing of the emulsions is shown to result from molecular diffusion in accordance with previous work. The increase of droplet size with time is correctly depicted by the theoretical equation derived by Lifshitz, Slyozov and Wagner (LSW). It seems that creaming has no real effect on emulsion ageing up to 1 μm. The influence of oil nature is clearly related to the physical properties of the oil (solubility in water, diffusion coefficient, interfacial tension), a typical consequence of molecular diffusion. An increase in the amount of hydrophobic groups fixed on the polymer leads to slower ageing. An increase in the anionic group content of the polymer has the reverse effect. Ionic strength has a significant effect on ageing of emulsions stabilized by dextran derivatives bearing ionic groups. Increasing ionic strength in the continuous phase gives rise to slower emulsion ageing. An attempt is made to rationalise all these facts by relating emulsion ageing to the data of interfacial tension measurements. The results follow approximately the tendency predicted by the LSW equation.

Dynamic behaviour of water in hydrogel containing hydrophobic side chains as studied by pulse 1H NMR

1H NMR measurements on spin–lattice relaxation time ( T 1) and spin–spin relaxation time ( T 2) were carried out on water contained in water-swollen copolymer gels prepared from hydrophilic methacrylic acid and hydrophobic stearyl methacrylate (SMA) or lauryl methacrylate (LMA). The degree of swelling of the copolymer gels decreases drastically with increasing component of hydrophobic monomers. 1H T 1 and T 2 of water show linear relationship with the cube root of the degree of swelling. Motion of water is restrained with the decreasing network size and the amount of hydrophobic groups in the network. T 1 measurements with temperature change revealed that the hydrogen bondings in water are decreased by introducing hydrophobic groups into the hydro gel..