Chemical Communications Blog

Gels are used in a number of applications, including wound dressings and fibre optics. They consist of a 3D network made up of one or more gelators held together by various non-covalent interactions (hydrogen bonding, π-π stacking, van der Waals interactions…) which serve to trap solvent molecules. Depending on the solvent and gelator used, the structure and/or viscosity of the gel can be controlled. A popular method of gel formation is through the addition of a gelator, or thickening agent, to a solution or solvent. Specifically, the development of low molecular weight gelators (LMWG) for the formation of new gels is a very active area of research. Once you can control the shape and viscosity of gels, as well as when and how they form, the possibilities for these systems are endless.

Many research groups have attempted to develop tools that allow gelation to be predicted for a given solvent, but most of these are limited to particular solvents or gelators. There is still no ‘magic bullet’ available for predicting the gelling ability of any solvent. Having said that, Matthieu Raynal and Laurent Bouteiller at UPMC University of Paris and CNRS in Paris, are one step closer towards addressing this deficiency.

Scientists can predict gel formation

In their work, Raynal and Bouteiller applied Hansen solubility parameters (HSPs) to predict the gelling ability of LMWGs in various solvents. These parameters were initially developed to determine solubility, or to see if a given substance will dissolve in another. To reach this conclusion, three contributions must be considered: dispersive interactions, polar interactions and hydrogen bonding, and these values are then plotted on to a 3D graph, called Hansen space. The closer two molecules are to each other, the more likely they will dissolve each other. Although not without its limitations, HSPs have successfully been used by polymer chemists to select solvents for paints or coatings.

To determine if these values could be used to predict gel formation, the duo gathered information on a number of solvents and LMWG sets for which the HSPs were known. When the team plotted the information in to Hansen space, they were surprised to find for each LMWG studied that gel-forming solvents clustered together.  Raynal and Bouteiller were then able to determine the so called  ‘gelation sphere’ (a region of the Hansen space in which solvents forming gels were located in preference to those that form a solution or insoluble species) specific to each LMWG. They then plotted the distance between each solvent and the centre of the sphere predicting the solvents that would form gels, which were easily separated from those that formed a solution or insoluble species with a particular LMWG.

This work could prove to be a real time-saving method for predicting the gelation of a LMWG in any solvent, but first, more LMWGs need to be studied, in a wide variety of solvents. Hopefully gel scientists around the world are on the case and we will soon be able to predict gel formation of a LMWG in any solvent.

Published on behalf of web science writer, Patricia Pantos

Read the full story here:
Organogel formation rationalized by Hansen solubility parameters
Matthieu Raynal and Laurent Bouteiller
Chem. Commun., 2011, 47, 8271-8273

Scientists in China have designed a low-cost copper-amine complex and used it as a template for the one-pot synthesis of a zeolite that exhibits excellent catalytic performance.

One-pot synthesis of copper zeolite

Feng-Shou Xiao from Zhejiang University and co-workers from Jilin and Beijing Normal Universities, worked together on rationally designing the copper zeolite (Cu-ZJM-1) with changeable Si/Al ratios. The resulting Cu-ZJM-1 has much higher copper content and a better dispersion of copper cations compared to other zeolites reported in the literature. It exhibits excellent properties when it comes to the selective catalytic reduction of the environmentally harmful gas nitrogen oxide (NOx), by ammonia.

Download this ChemComm communication, which will be free to access until the 15th July 2011.

A new iron carbonyl catalyst efficiently reduces amides using lower catalyst concerntrations, quicker reaction times and lower reaction temperatures, say scientists in Japan.

Iron carbonyl catalyst reduces various carboxamides using hydrosilane

Hideo Nagashima and colleagues from Kyushu University have reported a new heptanuclear iron carbonyl catalyst that can reduce various carboxamides using hydrosilane, 1,2-bis(dimethylsilyl)benzene. This is an important development as the catalyst actually shortens the reaction times, even at lower catalyst concentrations and at lower temperatures, when compared with other reported iron-catalysed hydrosilane reductions. 

Fancy reading more? Then download the ChemComm communication, which will be free to access until the 15th July 2011.

Human lysozyme on mesoporous silica (SBA-15) has been visualised in 3D, say scientists in Italy.

Ultrathin section of embedded mesoporous materials

Maura Monduzzi and her co-workers at Università di Cagliari, used an immunochemical method to investigate the location of human lysozyme molecules loaded onto SBA-15. Using post-embedding immunogold staining and transmission electron microscopy results in a 3D reconstruction and shows that the protein molecules were located on the external and internal surfaces of the mesoporous silica. This result may have important consequences in biocatalysis and applications requiring sustained drug release.

Want to know more? Then download the ChemComm communication, which will be free to access until the 15^th July 2011.

Making new n-type materials for bulk-heterojunction solar cells (BHJ) can be achieved by simply modifying the fullerene framework, say scientists in Japan.

Looking at LUMO and charge-density of modified fullerene

The BHJ solar cells may be an alternative to conventional silicon-based solar cells, if the low power conversion efficiency can be overcome. Yasujiro Murata and colleagues from Kyoto University have shown that structurally manipulating the C₆₀ skeleton is a promising approach for creating better acceptor materials for BHJ solar cells. This new approach means that the team can effectively control the lowest unoccupied molecular orbital (LUMO) level of the  C₆₀ pi-system, resulting in a clear improvement in open-circuit voltage – a promising development.

Fancy finding out more? Then download the ChemComm communication, which will be free to access until the 15^th July 2011.

A team of UK scientists have made gadolinium and dysprosium discs that can ‘chill well and relax slowly’ with interesting magnetic properties.

Structure of the gadolinium heptametallic complex

David Collison and his colleagues from the University of Manchester have designed heptametallic discs (i.e. with 7 metal centers) and have studied their structures and magnetic properties. The dysprosium disc shows single molecule magnetism behaviour and the gadolinum analogue shows a large magnetocaloric effect.  Fancy finding out more? Then download the ChemComm communication, which will be free to access until the 15th July 2011.

Also, are you interested in molecule-based magnetism research? Then take a look at Chem Soc Rev‘s recently published themed issue on Molecule-based Magnets, (Issue 6, 2011) guest edited by Joel Miller and Dante Gatteschi.