FLUOROPHOBIC EFFECT IN THE SELF-ASSEMBLY OF POLYMERS AND MODEL COMPOUNDS CONTAINING TAPERED GROUPS INTO SUPRAMOLECULAR COLUMNS

The synthesis and characterization of the tapered building blocks 6H,6 H,7H,7H,8H,8H-perfluorododecan-1-yloxy)benzoic acid (11-8/4), 4H,4H,5H ,5H,GH,6H-perfluorododecan-1-yloxy)benzoic acid (11-6/6), 2H,2H,3H,3H, 4H,4H-perfluorododecan-1-yloxy)benzoic acid (11-4/8), 2-{2-[2-(2-hydro xyethoxy)ethoxy]ethoxy}ethyl H,6H,7H,7H,8H,8H-perfluorododecan-1-yloxy )benzoate (19-8/4), 2-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}ethyl H,4H, 5H,5H,6H,6H-perfluorododecan-1-yloxy)benzoate (19-6/6), and 2-{2-[2-(2 -hydroxyethoxy)ethoxy]ethoxy}ethyl H,2H,3H,3H,4H,4H-perfluorododecan-1 -yloxy)benzoate (19-4/8) and of the methacrylates and polymethacrylate s of 19-8/4, 19-6/6, and 19-4/8 (i.e, 20-8/4, 20-6/6, 20-4/8 and respe ctively 21-8/4, 21-6/6, and 21-4/8) are described. All tapered buildin g blocks 11-m/n, 19-m/n, and the polymers 21-m/n (where m + n = 12 and m = number of hydrogenated, n = number of perfluorinated methylenic g roups of their alkyl tails) self-assemble into tubular supramolecular architectures which display an enantiotropic hexagonal columnar (Phi(h )) mesophase. The self-assembling ability of model compounds and polym ers was compared to that of their perhydrogenated analogues. From the perhydrogenated compounds, only the polymer 21-12/0 forms a Phi(h) pha se. Semifluorination of all model compounds and polymers first decreas es the melting temperature of the supramolecular assembly and uncovers and/or enhances the thermal stability of the Phi(h) phase (n = 4). A further increase of n from 4 to 6 and respectively 8 increases both th e isotropization temperature of the Phi(h) phase and the melting tempe rature. A parallel increase of the diameter of the supramolecular colu mns with the increase of n is observed. A mechanism for this dramatic increase in the self-assembly process via microsegregation of the perf luorinated and perhydrogenated parts of the tapered groups due to the fluorophobic effect was proposed.