Thermal and photo reversible gel–sol transition of azobenzene based liquid crystalline organogel

• Hydrogen bonding favors the long-range self-assembly leading to an entangled network structure.
• The non-liquid crystalline gelator can be converted into liquid crystalline organogel.
• The organogel exhibited monotropic nematic and smectic A phases.
• The trans-cis isomerization of the azobenzene moiety disrupts the entanglement of gel fibers of self-assembly resulting in gel–sol transition.
• The organogel is capable of the thermal and photo induced transition from gel–sol and vice versa.

Azobenzene based photoresponsive gelator, 1,2-bis[4-(4-(10-decyloxy)phenylazo)]-benzoylhydrazine showing selective gelation in alcoholic solvent is described. Whilst their thermodynamic behaviors are investigated by polarized optical microscopy and differential scanning calorimetry, the related layer arrangement is measured by X-ray diffraction techniques in which the organogel shows monotropic liquid crystalline phase. Present work shows that the non-liquid crystalline gelator can be converted into liquid crystalline organogel in the presence of alcoholic solvent in which the trans-cis isomerization of the azobenzene moiety disrupts the entanglement of gel fibers of self-assembly resulting in gel–sol transition. The present result also shows that the organogel is capable of the thermal and photo induced transition from gel–sol and vice versa.

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