Superabsorbent polymers are hydrophilic networks that can absorb and retain huge amounts of water or aqueous solutions. They are currently used in many areas including hygienic and bio-related uses (particularly in disposable diapers), agricultural uses (e.g., water reserving in soil, soil conditioning, and controlled release of agrochemicals), pharmaceutical dosage forms, separation technology, fibers/textiles, water-swelling rubbers, soft actuators/valves, electrical, construction, packaging, artificial snow, sludge/coal dewatering, fire-extinguishing gels, etc. Addition of clays and organo-modified clays into superabsorbent formulation has funded new generations of these hydrogels, i.e., superabsorbent hydrogel composites (SHCs) and superabsorbent hydrogel nanocomposites (SHNCs). New superabsorbent hydrogels are cheaper in price, and possess superior mechanical properties than non-composite counterparts. This review introduces the SHC and SHNC polymers with the focus on different minerals and humic additives, synthetic methods, the hydrogel characteristics and their applications. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers

Superabsorbent hydrogel composites and nanocomposites: A review

Oxidation of cyclobutanol by aqueous Fe(IV) generates cyclobutanone in ∼70% yield. In addition to this two-electron process, a smaller fraction of the reaction takes place by a one-electron process, believed to yield ring-opened products. A series of aliphatic alcohols, aldehydes, and ethers also react in parallel hydrogen atom and hydride transfer reactions, but acetone and acetonitrile react by hydrogen atom transfer only. Precise rate constants for each pathway for a number of substrates were obtained from a combination of detailed kinetics and product studies and kinetic simulations. Solvent kinetic isotope effect for the self-decay of Fe(IV), kH2O/kD2O = 2.8, is consistent with hydrogen atom abstraction from water.

Reactivity of aqueous Fe(IV) in hydride and hydrogen atom transfer reactions.

http://www.emec.licp.cas.cn/kycg/201007/W020110509523832293957.pdf

Nanocomposite of carboxymethyl cellulose and attapulgite as a novel pH-sensitive superabsorbent: Synthesis, characterization and properties

Evaluation of ammonium removal using a chitosan-g-poly (acrylic acid)/rectorite hydrogel composite

The coordination compounds of the tridentate oligopyridine ligand 2,2′:6′,2′′-terpyridine (tpy) are utilized in very different fields of research, such as materials science (e.g. photovoltaics), biomedicinal chemistry (e.g. DNA intercalation), and organometallic catalysis. Applications in the latter area have arisen from initial reports on electro- or photochemical processes and, today, a broad range of reactions—from artificial photosynthesis (water splitting) to biochemical and organic transformations as well as polymerization reactions—have been catalyzed by terpyridines and their transition metal complexes. In this review, the scope and the limitations of these applications, which emerged particularly in organic and macromolecular chemistry, will be evaluated.

Catalytic Applications of Terpyridines and their Transition Metal Complexes

A series of novel composites and nanocomposites xerogels based on acrylic acid, sepiolite and N,N′-methylenebisacrylamide were prepared using a solution polymerization technique at 70 °C. The quality of dispersion of the micronized sepiolite in the monomer is the crucial point for obtaining nanocomposites. A good dispersion explains the improvement of the absorbent properties of the nanocomposites with respect to the composites. This work investigates not only the influence of the mixing procedure on the swelling behaviour, but also the effect of the amount of clay on the absorbency of these hydrogels in deionized water and saline solution (0.2 wt% NaCl(aq)). A crosslinker concentration of 5 wt% sepiolite nanocomposite superabsorbent was shown to give the best results (1419 g g−1). Moreover, experimental results indicate that the absorbency in saline solution is smaller than that in deionized water. Rates of swelling for these absorbents were found to fit the Voigt expression. Finally, the model approximates Case II sorption in the early stages of the swelling process and Case I in the later stages. Copyright © 2006 Society of Chemical Industry

Synthesis and swelling behaviour of poly (sodium acrylate)/sepiolite superabsorbent composites and nanocomposites

Comparative study of the catalytic behaviour of Ru(III) and Ru(VI) on the oxidation of alcohols by hexacyanoferrate(III)

The host–guest chemistry between cucurbit[7]uril (CB7) and a series of bolaform (Bn) surfactants with different chain lengths, n = 12–22, was the target of our study. [3]Pseudorotaxanes are formed when the alkyl chain of the bolaform has more than 14 carbon atoms. In these cases, two CB7 molecules can be accommodated between the two head groups of the bolaform without addition of electrolytes to the medium. In the case of a bolaform with 12 carbon atoms, the electrostatic repulsion between the carbonyl groups of the CB7 molecules avoids the threading of a second CB7 molecule yielding a mixed structure formed by a [2]pseudorotaxane and an external host–guest complex. The assembly behavior was investigated using NMR spectroscopy, isothermal titration calorimetry (ITC), and kinetic measurements.

Electrostatic repulsion between cucurbit[7]urils can be overcome in [3]pseudorotaxane without adding salts.

Oxidation of 2,3-butanediol by alkaline hexacyanoferrate(III) using Ru(III) or Ru(VI) as catalyst†

The kinetics of the Ru(VI)-catalyzed oxidation of benzyl alcohol by hexacyanoferrate(III), in an alkaline medium, has been studied using a spectrophotometric technique. The initial rates method was used for the kinetic analysis. The reaction is first order in [Ru(VI)], while the order changes from one to zero for both hexacyanoferrate(III) and benzyl alcohol upon increasing their concentrations. The rate data suggest a reaction mechanism based on a catalytic cycle in which ruthenate oxidizes the substrate through formation of an intermediate complex. This complex decomposes in a reversible step to produce ruthenium(IV), which is reoxidized by hexacyanoferrate(III) in a slow step. The theoretical rate law obtained is in complete agreement with all the experimental observations. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 421–429, 2002

F. J. Poblete

Papers

Synthesis and swelling behaviour of poly (sodium acrylate)/sepiolite superabsorbent composites and nanocomposites

Comparative study of the catalytic behaviour of Ru(III) and Ru(VI) on the oxidation of alcohols by hexacyanoferrate(III)

Electrostatic repulsion between cucurbit[7]urils can be overcome in [3]pseudorotaxane without adding salts.

Oxidation of 2,3-butanediol by alkaline hexacyanoferrate(III) using Ru(III) or Ru(VI) as catalyst†

Kinetic study of the ruthenium(VI)‐catalyzed oxidation of benzyl alcohol by alkaline hexacyanoferrate(III)