SELF-ASSEMBLY OF TAPER-SHAPED MONOESTERS OF OLIGO(ETHYLENE OXIDE) WITH 3,4,5-TRIS(P-DODECYCLOXYBENZYLOXY)BENZOIC ACID AND OF THEIR POLYMETHACRYLATES INTO TUBULAR SUPRAMOLECULAR ARCHITECTURES DISPLAYING A COLUMNAR MESOPHASE

The taper-shaped monoesters of mono- 3a, di- 3c, tri- 3d, and tetra- 3 f ethylene glycol with 3,4,5-tris(p-dodecyloxybenzyloxy)benzoic acid 1 and their corresponding polymethacrylates, 6a, b, c and d, respective ly, self-assemble into a tubular supramolecular architecture displayin g an enantiotropic columnar hexagonal ((PHI(h)) mesophase. Characteriz ation of this supramolecular architecture by a combination of differen tial scanning calorimetry, wide- and small-angle X-ray scattering, the rmal optical polarized microscopy, and molecular modelling suggests a model in which the stratum of the column is formed by in between 3.9 a nd 5.4 molecules of 3 or 4.5 and 5.9 repeat units of 6 with their olig o(oxyethylenic) segments melted and segregated in the centre of the co lumn and their melted alkyl tails radiating towards the columns periph ery. 2-(2-Methoxyethyl) 3,4,5-tris(p-dodecyloxybenzyloxy)benzoate 3b ( the model compound of 3a in which the hydroxy group has been replaced by a methoxy group) is only crystalline, while is(p-dodecyloxy-benzylo xy)benzoyloxy]ethoxy}ethyl) ether 3g (which is the dimer of 3c) displa ys a monotropic PHI(h) phase. These results support that endo-recognit ion by H-bonding of the oligo(oxyethylenic)receptor of 3 and exo-recog nition provided by the tapered 3,4,5-tris(p-dodecyloxybenzyloxy)benzoa te fragment of 3 (most probably functioning by hydrophobic-hydrophobic interactions) provide the driving force for the self-assembly of this tubular supramolecular architecture. In the case of the supramolecula r architectures derived from 6, the H-bonding interaction is replaced by the poly(methacrylate) backbone which leads to a PHI(h) mesophase t hat undergoes isotropization at temperatures that are 40-degrees-C hig her than those of 3. The channel penetrating the middle of the supramo lecular cylinders derived from both 3 and 6 dissolves alkali-metal tri flates and the ionic interaction generated by the dissolved ion-pairs enhances the thermal stability of their PHI(h) phase. These results al lowed for the first time a comparison between a 'molecular' polymer ba ckbone effect (polymethacrylate) and a 'supramolecular' polymer backbo ne effect (generated by way of H-bonding and ionic interactions) to be made.