| Abstract: | The consequences of solvent order, imposed by the two smectic phases of 1,1,1,2,2,3,3,4, 4,5,5,6,6,7,7,8,8,9,9,10,10-heneicosylfluoroeicosane (F10H10, a “diblock” molecule) on the photochemistry of 1,1,1,2,2,3,3,4,4,5,5.6,6,7,7-pentadecylfluoro-8-hexadecanone (F7COH8) were investigated. Results from irradiations of F7COH8 in smectic F10H10 are compared to those obtained in hexane, perfluorohexane, and the isotropic phase of F10H10. They are complemented by 2H-NMR experiments on F10H10 solutions of F7COH8 deuterated at the methylene alpha to the carbonyl, and differential scanning calorimetry thermograms. More than 85% of the photoproducts are derived from carbonyl reduction and Norrish II processes. Based upon the 2H-NMR spectra and Norrish II photoproduct ratios, the microscopic environment experienced by the locus of reaction of F7COH8 in smectic F10H10 is not very restrictive towards the solute shape changes that must occur. This conclusion was not anticipated because the macroscopic order of the smectic phases of F10H10 is high. |
