Self-assembly of Nanofibre Gelling Materials in Organogels
Prashant Sawant, Xiang-Yang Liu*, Bing-Hung Chen, I. B. M. Noor, and . Pramesti
Department of Physics, Faculty of Science, National University of Singapore,
Singapore 117542 SINGAPORE
This is an abstract
for a presentation given at the
Foresight Conference on Molecular Nanotechnology
The gelling agents, so called 'small molecule gelling agents' are gaining popularity in the gelling of a wide range of organic solvents to form organogels.(1,2) A control over the growth of fibres and fibre network structure is a crucial step in controlling the macroscopic properties such as viscoelasticity and aesthetic look of organogels. A choice of solvent and processing conditions are crucial to control the growth of resultant nano-fibre structures.
We demonstrate this with (controlled) formation of fibres following gelators in different solvents: (a) lanosterol/dehydrolanosterol, 56:44, (denoted as L-DHL), and (b) N-lauroyl-L-glutamicacid-di-n-butylamide (LGADB). Solvents used are isostearyl alcohol (ISA), disooctylbutyl phthalate (DIOP), disooctyloctyl phthalate (DIBP), and silicone oils. Processing conditions used are temperature of gelation (Tg), and cooling rate. The growth rate of formation of these fibres is analyzed by the light scattering and the dynamic rheological methods. The microstructure of gels is examined with scanning electron microscopy, in conjunction, with a supercritical CO2 system.
Recently, we have shown that the gelation of SMGA is controlled a crystallographic mis-match branching which leads to the formation of the Caley fractal like interconnecting fibre network structures in the liquid.(1) This mechanism leads to the formation of three dimensional network structures of micro/nano-fibres, which results in the stable and clear gel.
Width of fibres is varied from nano to micron scale in different solvents and under different processing conditions like the temperature of gelation and the cooling rate. With help of these processing conditions we control the growth of fibres at nanoscale and therefore Successful in converting an unstable gel into a stable gel. In stable gels, the width of fibres is controlled to few nanometers (50-200nm).
In a nutshell, by employing proper solvents and processing conditions, it is possible to convert an unstable gel of detrimental aesthetic and rheological properties into a stable, clear and viscoelastic gel. These results are compared with other published gels systems.(2)
- (a) Mechanism of the Formation of Self-Organized Microstructures in Soft Functional Materials Liu, X. Y.; Sawant, P. D. Adv. Mater. 2002, 14(6), 421-26. (b) Formation kinetics of fractal nanofiber networks in organogels. Liu, X. Y.; Sawant, P. D. Appl. Phys. Lett. 2001, 79, 3518.
- (a) Low Molecular Mass Gelators of Organic Liquids and the Properties of Their Gels. Terech, P.; Weiss R. G. Chem. Rev. 1997, 97(8), 3133. (b) Organogels and Low Molecular Mass Organic Gelators Abdallah, D. J.; Weiss, R. G. Adv. Mater. 2000, 12, 1237.
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