Effect of Solvent on the Morphology and Microstructure of Light Emitting Organogels D. Dasgupta, 1 S. Srinivasan, 2 A. Ajayaghosh, * 2 J.M. Guenet * 1 Summary: Self assembly of oligo(phenylene vinylene) based gelator is studied in three different solvents namely, trans-decahydronaphthalene (trans-decalin), benzene and benzyl alcohol. The morphology as well as the thermal properties are different for benzyl alcohol gel as compared to those gels in trans-decalin or benzene. X-ray diffraction studies indicate that in case of benzyl alcohol gel, the molecular organization is highly ordered with respect to the fibrils grown in other two solvents. Keywords: lamellae; light emitting gel; self assembly; X-ray diffraction; p-p stacking Introduction The design and self-assembly of organic molecules to form functional superstruc- tures is the main goal of supramolecular chemistry. Self-assembly of p-conjugated organic molecules in solution is a funda- mental step to design ‘‘bottom up’’ optoe- lectronic devices. [1] In particular, molecular assemblies consisting of high degree of p-p stacking are of interest as the photo excited charge carriers can travel through it. [2–6] Therefore, to use the solution processing of such superstructures for device fabrication is of the utmost importance to understand how the self-assembly of these active molecules are influenced by the solvent used. George et al. has reported a new class of Oligo (p-phenylene vinylene) (OPV) based amphiphile molecules which form highly anisotropic nanostructures in apolar sol- vents like hexane, dodecane etc. when their isotropic solution are quenched to room temperature or below, resulting in the gelation of the solvent medium. [7] The OPV gelators stacks onto one another by p-p non covalent interaction forces to produce fibrillar structures. The long pen- dent aliphatic chains build up a lamellar structure in one hand and in the other hand, several OPV molecules are also linked together by hydrogen bonding involving the hydroxymethyl end groups (see Scheme 1). Thus the fibrillar cross section is attributed to H-bonded supramolecular polymer chains laterally connected to each other by van der waals forces. Therefore, the preferential growth in either direction should determine the shape of these fibrillar crystals. In this contribution, we have made an attempt to explore the possible influences of solvent on the supramolecular organization of these light emitting gel fibrils. We have investigated the gelation behaviour in three solvents: benzene and a benzene derivative that can establish p-p interactions with the OPV namely, benzyl alcohol, which, in addition, mimics the terminal groups of the OPV molecule, and the two conformers of decahydronaphthalene (cis and trans- decahydronaphthalene designated as cis- decalin and trans-decalin in what follows), which does not contain any p electrons. Experimental Part Materials The synthesis and properties of oligo (p-phenylene vinylene) gelator (OPVOH) is described in reference. [8] The basic Macromol. Symp. 2011, 303, 134–140 DOI: 10.1002/masy.201150518 134 1 Institut Charles Sadron, CNRS UPR22, 23 rue du Loess, BP 84047, F-67034 STRASBOURG Cedex2, France E-mail: jean-michel.guenet@ics-cnrs.unistra.fr 2 National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Industrial estate P.O, Pappanamcode, TRIVANDRUM 695019, India Copyright ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com