Soft Functional Materials Induced by Fibrillar Networks of Small Molecular Photochromic Gelators

Low-molecular-mass organogelators (LMOGs) based on photochromic molecules aggregate in selected solvents to form gels through various spatio-temporal interactions. The factors that control the mode of aggregation of the chromophoric core in the LMOGs during gelation, gelation-induced changes in fluorescence, the formation of stacked superstructures of extended pi-conjugated systems, and so forth are discussed with selected examples. Possible ways of generating various light-harvesting assemblies are proposed, and some unresolved questions, future challenges, and their possible solutions on this topic are presented.

Metal cholate hydrogels: versatile supramolecular systems for nanoparticle embedded soft hybrid materials

This work describes the formation of hydrogels from sodium cholate solution in the presence of a variety of metal ions (Ca2+, Cu2+, Co2+, Zn2+, Cd2+, Hg2+ and Ag+). Morphological studies of the xerogels by electron microscopy reveal the presence of helical nanofibres. The rigid helical framework in the calcium cholate hydrogel was utilised to synthesize hybrid materials (AuNPs and AgNPs). Doping of transition metal salts into the calcium cholate hydrogel brings out the possibility of synthesising metal sulphide nano-architectures keeping the hydrogel network intact. These novel gel-nanoparticle hybrid materials have encouraging application potentials.

Organophotocatalysis in nanostructured soft gel materials as tunable reaction vessels: comparison with homogeneous and micellar solutions

Riboflavin tetraacetate-catalyzed aerobic photooxidation of 1-(4-methoxyphenyl)ethanol was investigated as a model reaction under blue visible light in different soft gel materials, aiming to establish their potential as reaction vessels for photochemical transformations. Three strategies involving different degrees of organization of the catalyst within the gel network were explored, and the results compared to those obtained in homogeneous and micellar solutions. In general, physical entrapment of both the catalyst and the substrate under optimized concentrations into several hydrogel matrices (including low-molecular-weight and biopolymer-based gels) allowed the photooxidation with conversions between 55 and 100% within 120 min (TOF similar to 0.045-0.08 min(-1); k(obs) similar to 0.011-0.028 min(-1)), albeit with first-order rates ca. 1-3-fold lower than in solution under comparable non-stirred conditions. Remarkably, the organogel made of a cyclohexane-based bisamide gelator in CH3CN not only prevented the photodegradation of the catalyst but also afforded full conversion in less than 60 min (TOF similar to 0.167 min(-1); k(obs) similar to 0.073 min(-1)) without the need of additional proton transfer mediators (e. g., thiourea) as it occurs in CH3CN solutions. In general, the gelators could be recycled without detriment to their gelation ability and reaction rates. Moreover, kinetics could be fine-tuned according to the characteristics of the gel media. For instance, entangled fibrillar networks with relatively high mechanical strength were usually associated with lower reaction rates, whereas wrinkled laminated morphologies seemed to favor the reaction. In addition, the kinetics results showed in most cases a good correlation with the aeration efficiency of the gel media.

Studies On Friction And Formation Of Transfer Layer In Hcp Metals

Surface texture plays an important role in the frictional behavior and transfer layer formation of contacting surfaces. In the present investigation, basic experiments were conducted using an inclined pin-on-plate sliding apparatus to better understand the role of surface texture on the coefficient of friction and the formation of a transfer layer. In the experiments, soft HCP materials such as pure Mg and pure Zn were used for the pins and a hardened 080 M40 steel was used for the plate. Two surface parameters of the steel plates—roughness and texture—were varied in tests that were conducted at a sliding speed of 2 mm/s in ambient conditions under both dry and lubricated conditions. The morphologies of the worn surfaces of the pins and the formation of the transfer layer on the counter surfaces were observed using a scanning electron microscope. In the experiments, the occurrence of stick-slip motion, the formation of a transfer layer, and the value of friction were recorded. With respect to the friction, both adhesion and plowing components were analyzed. Based on the experimental results, the effect of surface texture on the friction was attributed to differences in the amount of plowing. Both the plowing component of friction and the amplitude of stick-slip motion were determined to increase surface textures that promote plane strain conditions and decrease the textures that favor plane stress conditions.

Impedance tube technology for flow acoustics

Acoustic impedance of a termination, or of a passive subsystem, needs to be measured not only for acoustic lining materials but also in the exhaust systems of flow machinery, where mean flow introduces peculiar problems. Out of the various methods of measurement of acoustic impedance, the discrete frequency, steady state, impedance tube method [1] is most reliable, though time consuming, and requires no special instrumentation.

Novel Algorithm for estimation of Swell Pressure of Fine Grained Soils Based on Diffuse Double Layer (DDL) Theory

Use of engineered landfills for the disposal of industrial wastes is currently a common practice. Bentonite is attracting a greater attention not only as capping and lining materials in landfills but also as buffer and backfill materials for repositories of high-level nuclear waste around the world. In the design of buffer and backfill materials, it is important to know the swelling pressures of compacted bentonite with different electrolyte solutions. The theoretical studies on swell pressure behaviour are all based on Diffuse Double Layer (DDL) theory. To establish a relation between the swell pressure and void ratio of the soil, it is necessary to calculate the mid-plane potential in the diffuse part of the interacting ionic double layers. The difficulty in these calculations is the elliptic integral involved in the relation between half space distance and mid plane potential. Several investigators circumvented this problem using indirect methods or by using cumbersome numerical techniques. In this work, a novel approach is proposed for theoretical estimations of swell pressures of fine-grained soil from the DDL theory. The proposed approach circumvents the complex computations in establishing the relationship between mid-plane potential and diffused plates’ distances in other words, between swell pressure and void ratio.

Soft-chemical routes to synthesis of solid oxide materials

We describe three different families of metal oxides, viz., (i) protonated layered perovskites, (ii) framework phosphates of NASICON and KTiOPO4 (KTP) structures and (iii) layered and three-dimensional oxides in the H-V-W-O system, synthesized by 'soft-chemical' routes involving respectively ion-exchange, redox deinteracalation and acid-leaching from appropriate parent oxides. Oxides of the first family, HyA2B3O10(A = La/Ca; B = Ti/Nb), exhibit variable Bronsted acidity and intercalation behaviour that depend on the interlayer structure. V2(PO4)3 prepared by oxidative deintercalation from Na3V2(PO4)3 is a new host material exhibiting reductive insertion of lithium/hydrogen, while K0.5Nb0.5 M0.5OPO4(M = Ti, V) are novel KTP-like materials exhibiting second harmonic generation of 1064 nm radiation. HxVxW1-xO3 for x = 0.125 and 0.33 possessing alpha-MoO3 and hexagonal WO3 structures, prepared by acid-leaching of LiVWO6, represent functionalized oxide materials exhibiting redox and acid-base intercalation reactivity.

Soft-chemical synthesis of new non-linear optical materials, K0.5M0.5Ti0.5OPO4(M = Nb, Ta),related to KTiOPO4

Soft-chemical oxidation of KTiOPO4-like KM(0.5)(V)Ti(0.5)(III)OPO(4) (M = Nb, Ta) using chlorine in CHCl3 is accompanied by partial deintercalation of potassium, yielding K(0.5)MV(0.5)Ti(0.5)(IV)OPO(4) compounds which are new non-linear optical materials that exhibit efficient second-harmonic generation of 1064 nm radiation, as does KTiOPO4.

Multi-component, Self-assembled, Functional Soft Materials

Supramolecular chemistry is an emerging tool for devising materials that can perform specified functions. The self-assembly of facially amphiphilic bile acid molecules has been extensively utilized for the development of functional soft materials. Supramolecular hydrogels derived from the bile acid backbone act as useful templates for the intercalation of multiple components. Based on this, synthesis of gel-nanoparticle hybrid materials, photoluminescent coating materials, development of a new enzyme assay technique, etc. were achieved in the author's laboratory. The present account highlights some of these achievements.

Tribological response of soft materials sliding against hard surface textures at various numbers of cycles

In the present investigation, various kinds of textures were attained on the steel surfaces. Roughness of the textures was varied using different grits of emery papers or polishing powders. Pins made of pure Al, Al-4Mg alloy and pure Mg were then slid against prepared steel plate surfaces at various numbers of cycles using an inclined pin-on-plate sliding tester. Tests were conducted at a sliding velocity of 2mms(-1) in ambient conditions under both dry and lubricated conditions. Normal loads were increased up to 110N during the tests. The morphologies of the worn surfaces of the pins and the formation of transfer layer on the counter surfaces were observed using a scanning electron microscope. Surface roughness parameters of the plate were measured using an optical profilometer. In the experiments, it was observed that the coefficient of friction and formation of a transfer layer (under dry and lubricated conditions) only depended on surface texture during the first few sliding cycles. The steady-state variation in the coefficient of friction under both dry and lubrication conditions was attributed to the self-organisation of texture of the surfaces at the interface during sliding. Copyright (C) 2012 John Wiley & Sons, Ltd.

White light emitting soft materials from off-the-shelf ingredients

Balanced white light emitting systems are important for applications in electronic devices. Of all types of white light emitting materials, gels have the special advantage of easy processability. Here we report two white light emitting gels, which are based on lanthanide cholate self-assembly. The components are commercially available and the gels are prepared by simply sonicating their aqueous solutions (1-3min), unlike any other known white light emitting systems. Their CIE co-ordinates, calculated from the luminescence data, fall in the white light range with a correlated color temperature of ca. 5600 K.

Soft-particle model analysis of effect of LPS on electrophoretic softness of Acidithiobacillus ferrooxidans grown in presence of different metal ions

The effect of Surface lipopolysaccharides (LPS) on the electrophoretic softness and fixed charge density in the ion-penetrable layer of Acidithiobacillus ferrooxidans cells grown in presence of copper or arsenic ions have been discussed, The electrophoretic mobility data were analyzed using the soft-particle electrophoresis theory. Cell surface potentials of all the strains based on soft-particle theory were lower than those estimated using the conventional Smoluchowski theory, Exposure to metal ions increased the Surface electrophoretic softness with decrease in the fixed charge density. Effect of cell surface lipopolysaccharides on the model parameters are investigated and discussed.