Visualizable Cylindrical Macromolecules with Controlled Stiffness from Backbones Containing Libraries of Self-Assembling Dendritic Side Groups

Abstract

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.

Structure–Property Relationships for Self‐Assembled Zinc Chlorin Light‐Harvesting Dye Aggregates

“…, and Hünigs base (N-ethyldiisopropylamine) in dry dichloromethane, [18] leading to the corresponding esters 7 a-c in yields of 51-76 % and 8 d,e in yields of 57-63 %. Subsequently, the 3 1 -vinyl group of 7 a-c was transformed into the corresponding diol with osmium tetroxide, followed by oxidative cleavage by sodium periodate to afford the respective formyl derivatives 8 a-c in yields of 65-98 %.…”

Molecular weight and arm number of a star‐shaped styrene–butadiene block copolymer synthesized on a pilot‐vessel scale

“…22,37 The retardation of the large molecules in the size exclusion separation reflects the hyperbranched molecular architecture; the origin of the retardation, however, remains unclear. 38,39 Core-core coupling or entanglement of the partial, large branched molecules in the pore of the column packing may be the explanation of the delay in size exclusion separation. Moreover, the hydrodynamic radii of the partial, large molecules for star-shaped SBS become relatively small as a result of core-core coupling or molecule entanglement.…”

Self-assembly using dendritic building blocks—towards controllable nanomaterials

“…For example, when attached to short flexible backbones, the dendrons can produce a spherical polymer conformation, whilst when attached to long polymer chains, the self-ordering pattern of the monodendrons gives rise to a cylindrical system [171]. The structure of the dendritic groups plays a role in controlling the conformation and stiffness of the polymer backbone [172]. The ability to control the conformation of polymeric molecular systems using this type of approach is of considerable current interest, with designed folding systems being referred to as foldamers [173].…”