Gels

Exploiting crystal engineering and supramolecular synthon concepts, a series of new gelator salts based on primary ammonium dicarboxylate (PAD) salts of azobenzene-4,4′-dicarboxylic acid and primary alkyl amines have been synthesized and characterized by various physico-chemical techniques. Most of the salts were shown to form gels with various solvents. Interestingly, most of the gelator salts possessed rarely observed reverse-thermal gelation (gelation with the rise of temperature) ability of aromatic solvents which may be relevant in developing thermo-responsive materials.

New organogelator, N,N′-bis(3,4,5-tridodecyloxy)benzoylurea (1), gelled organic liquid such as alcohol, hydrocabons, ethyl acetate, salad oil, terpenes, and essential and perfume oil at low concentration of gelator. The terpene and perfume gels show good release of the volatile components for a long time.

It is accepted that terpenes are effective penetration enhancers to promote the passage of drugs or chemicals through the human skin barrier. However the physical and chemical changes of a pharmaceutical vehicle induced by the incorporation of terpenes have not been explored. Thus, this study examines the effects of three terpenes (linalool, cineole, limonene) on the rheology and chemical stability of an organogel composed of dibutyllauroylglutamide (GP1) and propylene glycol (PG).

Arjunolic acid, a triterpenoid, renewably resourced from Terminalia arjuna saw- dust, has the potential of being used as a structural molecular framework in supramolecular chemistry and nanoscience. The nanosized chiral triterpenoid on derivatization could immo- bilize varieties of organic solvents at low concentrations. The low-molecular-mass organic compounds self-assembled in organic media to form fibrous network structures having fibers of nano- to micrometer diameters. A dual-component supramolecular gelation has been demonstrated, exhibiting interesting thermochromic property.

A super-gelator for cyclohexane is presented, one of four cholesterol-appended ferrocene derivatives specifically designed and prepared as new low-molecular-weight organogelators. The gel forming from this system can be molded into films, forms at room temperature, and is responsive to various stimuli (see figure), including heating, shaking, sonication, and chemical oxidation, which endows it with promising potential applications.

Five 1-O-methyl-4,6-O-ben- zylidene derivatives of the monosac- charides d-glucose, d-galactose, and d- mannose were synthesized. The b-iso- mer of the d-glucose derivative was sparingly soluble in most organic sol- vents, whereas the a-isomer of the d- mannose derivative was soluble in many organic solvents. The a-isomer of the d- glucose derivative and the a- and b- isomers of the d-galactose derivative acted as versatile gelators of various organic solvents ; this indicates that sac- charides are useful as potential tem- plates for the molecular design of chiral gelators.

Some methyl 4,6-O-benzylidene monosaccharides can act as strong low molecular weight gelators for various organic solvents. As they are accessible in a variety of homologues, each with a unique molecular architecture, they can be used for systematic studies of gelation phenomena. Structural details of their hydrogen-bond-based fiber network in the gel phase can be resolved by small angle X-ray scattering (SAXS).

Polymers are a widespread class of materials that provide an often advantageous combination of properties. Easy processability and high versatility combined with low costs make polymers the materials for an increasing number of high-tech and commodity applications. Semi-crystalline polyolefins are an important class of polymers, produced in more than 150 million metric tons per year. They are used to make a wide range of products ranging from fibers with superior mechanical properties to flexible packaging and molded parts.

Gelation tests of rod like liquid crystals (LCs), columnar LCs, and cholesteric LCs rod-like have been employed. 4-Cyanophenyl 4-n-alkoxybenzoates, 4-cyano-4’-alkoxybiphenyls, 4,4’-dialkanoyloxybiphenyls, azoxybenzene derivatives, 2,3,6,7,10,11-hexaalkoxytriphenylenes, and cholesteryl esters, except for cholesteryl alkyl carbonates and cholesteryl esters with alkenyl side chain, gelled organic liquids. By using these LCs as organogelator, terpene and perfume gels containing 95% or more of terpenes and essential oil could be prepared.

Graphene oxide (GO) has been recognized as a unique two-dimensional building block for various graphene-based supramolecular architectures. In this article, we systematically studied the three-dimensional self-assembly of GO sheets in aqueous media to form hydrogels. The gelation of GO can be promoted by different supramolecular interactions, including hydrogen bonding, π-stacking, electrostatic interaction, and coordination. Furthermore, the lateral dimensions of GO sheets also have strong influences on GO gelation.