多种凝胶因子杂化成胶Hybrid organogels and aerogels from co-assembly of

a
Indian Institute of Science, Department of Organic Chemistry, Bangalore, 560012, India. E-mail: maitra@orgchem.iisc.ernet.in Univ. Bordeaux, ISM, UMR 5255, F-33400 Talence, France. E-mail: a.del-guerzo@ism. u-bordeaux1.fr
The blending of perfluorinated bile ester derivatives with the gelator 2,3-didecyloxyanthracene (DDOA) yields a new class of hybrid organo- and aerogels displaying a combination of optical and mechanical properties that differ from those of pure gels. Indeed, the nanofibers constituting the hybrid organogels emit polarized blue light and display dichroic near-UV absorption via the achiral DDOA molecules, thanks to their association with a chiral bile ester. Moreover, the thermal stability and the mechanical yield stress of the mixed organogels in DMSO are enhanced for blends of DDOA with the deoxycholic gelator (DC11) having a C11 chain, as compared to the pure components' gels. When the chain length of the ester is increased to C13 (DC13) a novel compound for aerogel formation directly in scCO2 is obtained under the studied conditions. A mixture of this compound with DDOA is also able to gelate scCO2 leading to novel composite aerogel materials. As revealed by SAXS measurements, the hybrid and the pure DDOA and DC13 aerogels display cell parameters that are very similar. These SAXS experiments suggest that crystallographic conditions are very favorable for the growth of hybrid molecular arrangements in which DDOA and DC13 units could be interchanged. Specific molecular interactions between two components are not always a pre-requisite condition for the formation of a hybrid nanostructured material in which the components mutually induce properties.
Received 17th January 2013 Accepted 26th March 2013 DOI: 10.1039/c3tc30104d /MaterialsC
Introduction
Supramolecular gels, a class of so materials, are formed by the self-assembly of low molecular weight organic gelators (LMOG's) through a variety of non-covalent interactions such as H-bonding, p–p stacking, solvophobic/van der Waals interactions and metal coordination.1,2 In these materials, the solvent is immobilized by a three dimensional network generated by the molecular self-assembly of the gelling agent. Xerogels and aerogels, two kinds of solid materials, can be obtained by drying these gels. A xerogel is formed upon conventional drying of the wet gels, by increasing the temperature or decreasing the air pressure with concomitant collapse of the initially uniform gel body due to capillary forces. In contrast, aerogels are obtained by gelling a liquid or a supercritical uid, and subsequently replacing the uid by air without signicantly altering the
Cite this: J. Mater. Chem. C, 2013, 1, 3305
Hybrid organogels and aerogels from co-assembly of structurally different low molecular ቤተ መጻሕፍቲ ባይዱeight gelators
Supratim Banerjee,a Rajat K. Das,abcd Pierre Terech,e Arnaud de Geyer,f ´ Del Cyril Aymonier,d Anne Loppinet-Serani,d Guillaume Raffy,bc Uday Maitra,*a Andre Guerzo*bc and Jean-Pierre Desvergne*bc
Journal of Materials Chemistry C
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network structure or the initial volume of the gel, yielding pores and high inner surface area.3 Gels are widely used in cosmetics, lubricants and other industrial applications, but evolution in LMOG research paves the way for their developments in hightech materials and biomaterials.4,5 Among these, hybrid, composite and mixed materials stimulate a high interest due to the fact that two different components, which can have very different origins, are merged into a unique material with properties that cannot be achieved by one of the building blocks alone. Several non-covalent gels were prepared using two or more components. In a rst case, strengthening of the gel occurs by using molecules that are complementary and interact in the gel, for example by synergistic H-bond interactions (Vel´ azquez and co-workers)6 or by inserting photo-polymerizable units (D´ ıaz and co-workers).6 In a second case, molecules with very similar structures are used, for example by reinforcing the mechanical stability of gels by using additives (Hamachi and co-workers)6 or by blending a gelator with a structurally similar chiral analogue to induce supramolecular chirality (Schenning, Ajayaghosh and co-workers).2 In contrast, two structurally different molecules can self-assemble orthogonally to form two different nanostructures, such as a brillar network and vesicles (Van Esch and co-workers).2 Comparably, distinguishable nano-structures such as nanobers and nanoparticles (metallic NPs, Smith and co-workers,2 or clays, Aida