FLUOROPHOBIC EFFECT INDUCES THE SELF-ASSEMBLY OF SEMIFLUORINATED TAPERED MONODENDRONS CONTAINING CROWN-ETHERS INTO SUPRAMOLECULAR COLUMNAR DENDRIMERS WHICH EXHIBIT A HOMEOTROPIC HEXAGONAL COLUMNAR LIQUID-CRYSTALLINE PHASE

The rational design, synthesis, and characterization of the building b locks obtained by the esterification of the first generation of tapere d monodendrons 3,4,5-tris(p-dodecan-1-yloxy)benzoic acid (12-AG) and 3 ,3,5-tris[p-(n-dodecan-1-yloxy)benzyloxy]benzoic acid (12-ABG) contain ing semifluorinated dodecyl groups [i.e., 12Fn-AG-15C5 (n = 0, 4, 6, 8 ), 12Fn-AG-B15C5, 12Fn-ABG-15C5, and 12Fn-ABG-B15C5 (n = 0 and 8) wher e n following the letter F represents the number of outer perfluorinat ed methylenic units of the dodecyl group] with 4'-hydroxymethyl(benzo- 15-crown-5) (B15C5) and 1-hydroxymethyl(15-crown-5) (15C5) are describ ed. All building blocks self-assemble into supramolecular cylindrical or rod-like dendrimers via ion-mediated complexation processes. These rod-like supermolecules form a thermotropic hexagonal columnar (Phi(h) ) liquid crystalline (LC) phase. The fluorination of the dodecyl group s of these tapered building blocks enhances dramatically their self-as sembly ability. The building blocks based on n = 6 and 8 self-assemble into supramolecular columns solely via the fluorophobic effect. Direc t structural characterization of the supramolecular columns obtained v ia these two molecular recognition processes by a combination of techn iques consisting of differential scanning calorimetry, X-ray diffracti on, and thermal optical polarized microscopy, and of the columns obtai ned solely via the fluorophobic effect allowed the construction of mol ecular models for the supramolecular columns obtained via these two or ganizing forces. An increase in the column diameter with increasing n and with the complexation of metal salts (i.e., alkali metal trifluoro methanesulfonates) accounts for a structural model in which the uncomp lexed and complexed crown ethers are placed side-by-side in the center of the column with the melted tapered side groups radiating toward it s periphery. The perfluorinated segments of the building blocks are mi crosegregated from the perhydrogenated and aromatic segments of the co lumn. The supramolecular columns obtained from building blocks with n = 8 align homeotropically in the Phi(h) LC phase on untreated glass sl ides, i.e., form single crystal liquid crystals in which the long axes of their columns are perpendicular to the glass surface. Both the sel f-assembly of supramolecular columns induced solely by the fluorophobi c effect and the homeotropic alignment of these columns in their Phi(h ) LC phase open extremely interesting new synthetic and technologic op portunities in the area of self-assembly of well-defined supramolecula r architectures obtained from monodendrons and other building blocks.