Figure 5.

Textural changes of hybrid gels during exposure to vapors of (a) hexane, (b) ethyl acetate, and (c) chloroform and subsequent recovery, as observed through the POM and corresponding signals extracted from video analysis. POM photos were taken with crossed polarizers at room temperature, (a) 5CB hybrid gel. The hexane vapors drive 5CB to isotropization, whereas during the recovery period, the nematic radial droplets are restored. Time stamps refer to the time after the start of exposure. The white line corresponds to 50 μm, (b) ring formation of TFCDs exhibited by a hybrid gel containing 8CB. 0 s: initial state, exposure to ethyl acetate starts, 0.7 s: onset of the smectic A to nematic transition, 1.3 s: nematic phase almost at completion, 3.9 s: 8CB turns isotropic. At 5 s, diethyl ether is expelled and the recovery period starts. 5.1 s: isotropic to nematic transition, 6.3 s: nematic phase, 7.3 s: onset of the nematic to smectic A transition, 7.8 s: onset of the TFCD formation, 14.7 s: completion of the TFCD formation. The white line corresponds to 25 μm. Time stamps refer to the time after the start of exposure, (c) dark droplets formed in 8CB hybrid gels. 0 s: initial state, exposure to chloroform starts, 0.3 s: onset of the smectic A to nematic transition, 0.6 s: progress of the nematic phase formation, 3.2 s: 8CB turns isotropic. At 5 s, chloroform is expelled and the recovery period starts, 6.3 s: isotropic to nematic transition, 6.9–9.8 s: nematic phase progress toward the smectic A transition, 14.8 s: smectic A phase. The white line corresponds to 50 μm. Time stamps refer to the time after the start of exposure. An example of the signals was obtained through video frame analysis using ImageJ from e-nose experiments conducted using the polarizing optical microscope. Exposure to acetone vapors (calculated via ImageJ) is portrayed for the hybrid nCB gels (d) 5CB, (e) 8CB. Four consecutive cycles are depicted, each 5 s of exposure (gray columns) followed by 15 s of recovery with ambient air.