The synthesis and structural analysis of a library containing 13 taper- and conical-shaped self-assembling dendrons, 16 dendritic monomers, and their corresponding polymers is reported. Fifteen of these polymers exhibit a well-defined cylindrical shape produced by the self-assembly of their dendritic side groups that self-organizes in a hexagonal columnar two-dimensional liquid crystalline lattice. The retrosynthetic analysis of this lattice by X-ray diffraction (XRD) showed that the diameter (60 to 41 Å) and the number of repeat units forming the cylinder cross-section (7 to 1.9) of these polymers are determined by the structure of their dendritic side groups. This demonstrates that, in the hexagonal columnar lattice, the conformation (from helical to fully extended) and the stiffness of the polymer backbone penetrating through the center of the cylinder are controlled in a systematic and predictive way by the structure of the side groups. Dynamic and static light-scattering experiments have demonstrated the same trend for the stiffness of these polymers in solution (Kuhn segment length from 200 to 1032 Å). Single chains and monolayers of these polymers were visualized and quantitatively analyzed by scanning force microscopy (SFM) on a graphite surface to provide the first comparative study of the conformation, stiffness, and contour length in solution (by light scattering), in the disordered solid state on a flat substrate (by SFM), and in the hexagonal columnar lattice (by XRD). The elaboration of this library of visualizable cylindrical macromolecules with controlled chain conformation and stiffness accesses the elucidation of many fundamental problems of the field of polymer science at the molecular level and the design of multifunctional nanoscale systems based on single polymer chains.

No abstract

The synthesis of the first generation AB 3 monodendrons 3,4,5-tris[6-alkyloxy-2-methylnaphthyloxy]benzoic acid (with decyl, dodecyl, tetradecyl, and hexadecyl alkyl groups), 3,4,5-tris[4-(4′dodecyloxyphenyl)benzyloxy]benzoic acid, their ω-hydroxy(tetraethylene glycol) esters, and the corresponding methacrylates and poly(methacrylate)s is described. All monodendrons and the corresponding polymers self-assemble into supramolecular columns that self-organize in a columnar hexagonal (Φh) thermotropic liquid crystalline (LC) phase. The characterization of their Φh phase by a combination of differential scanning calorimetry (DSC), thermal optical polarized microscopy, and X-ray diffraction experiments demonstrated an intracolumnar microsegregated model for these supramolecular structures. The role and the contribution of the aliphatic, aromatic, oligooxyethylenic, and polymethacrylate fragments to the formation and the control of the external diameter, the internal structure, and the stability of these supramolecular columns and of the Φ h phase were quantitatively evaluated and demonstrated that the contribution of the aromatic component dominates over that of the other structural components both in the control of column diameter and in thermodynamic stability of the resulted Φh phase. Scheme 2. Synthesis of 3,4,5-tris-[n-alkyloxy]benzoic Acid Derivatives, 8-n-Nf (n ) 10, 12, 14, 16) and 8-12-Bp