Reverse Thermal Gelation of Aromatic Solvents by a Series of Easily accessible Organic Salt Based Gelators|

C Soft Matter Dynamic Article Links < Cite this: Soft Matter, 2012, 8, 2595 PAPER www.rsc.org/softmatter Downloaded by University of St Andrews Library on 26 September 2012 Published on 23 January 2012 on http://pubs.rsc.org | doi:10.1039/C2SM06957A Reverse thermal gelation of aromatic solvents by a series of easily accessible organic salt based gelators† Pathik Sahoo, Indrajit Chakraborty‡ and Parthasarathi Dastidar* Received 13th October 2011, Accepted 12th December 2011 DOI: 10.1039/c2sm06957a Exploiting crystal engineering and supramolecular synthon concepts, a series of new gelator salts based on primary ammonium dicarboxylate (PAD) salts of azobenzene-4,40 -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. Introduction Supramolecular synthon, originally coined by Desiraju,1 is a wellstudied and accepted tool in supramolecular chemistry2 in general and crystal engineering3 in particular for designing desired supramolecular materials.4 By analogy, supramolecular synthon plays the same pivotal role in supramolecular synthesis as synthon does in covalent organic synthesis.5 Among the various supramolecular materials that have been synthesized using the supramolecular synthon approach,6 low molecular weight organic gelators (LMWGs)7 are important due to their various potential applications such as in the field of electrooptics/ photonics,8 sensors,9 cosmetics,10 structure directing agents,11 conservation of art,12 drug delivery,13 and bio-medical applications,14 catalysis15 etc. LMWGs (molecular weight