Solvent-dependent nanostructures of gels of a Gemini surfactant based on perylene diimide spacer and oligostyrene tails

• Gels of non-ionic Gemini surfactant with perylene diimide spacer and oligostyrene tails.
• Folded fiber morphology with trans-decalin gel; vesicles with other solvents.
• Gelation without any hydrogen bonding groups or charge centers in the molecule.
• Higher structural order with trans-decalin gel.
• Modulus higher with trans-decalin gel than with other solvents.

We discuss the thermo-reversible gelation of a non-ionic Gemini surfactant with perylene tetracarboxylic diimide (PTCDI) as the spacer and oligostyrene as the tails, with cyclohexane, toluene, cis-decalin and trans-decalin. The gel with trans-decalin shows a morphology that is distinctly different from those of other solvents. As is usually seen with Gemini surfactants, vesicular morphology is observed in the case of gels using cyclohexane, toluene and cis-decalin, with a wall thickness of about 40 nm. The trans-decalin gel shows a fibrous morphology, and these fibers exhibit an eaves-trough type of folding as was seen before with other systems that we studied (Dahan and Sundararajan, 2014; Khanna et al., 2009). X-ray diffraction and UV–Vis spectroscopy indicate that the molecular packing is more ordered in the case of trans-decalin gels. In addition, the storage modulus (G′) of the trans-decalin gels is an order of magnitude higher than those of gels from the other three solvents. Unlike the other reported cases of gels with either perylene diimide derivatives or Gemini surfactants, gelation occurs in the present work, without any hydrogen bonding moieties or charge centers in the structure of the molecule studied here.

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