Controlling the assembly of hydrogen-bonded supramolecular polymers by the strategy of molecular tectonics

Abstract

Studies of how hydrogen bonding can be used to control molecular association continue to yield exciting discoveries in supramolecular chemistry. A simple way to make molecules that associate predictably is to link carefully selected cores to functional groups that form multiple hydrogen bonds according to reliable patterns. Bifunctional molecules constructed according to this strategy can associate to form linear aggregates robust enough to warrant the name supramolecular polymers, even though the bifunctional monomers are joined only by hydrogen bonds. More complex molecules with multiple hydrogen-bonding sites can be devised so that neighbors are held in predetermined positions, giving crystalline solids with predictable architectures and properties not previously seen in other materials. Initial studies of the ability of such compounds to associate in solution and in the molten state suggest that hydrogen-bonded networks can be purposefully designed to create novel par- tially ordered liquid materials, including liquid crystals, gels, and fluids with unusual rheological properties.

PTC effect in HDPE filled with carbon blacks modified by Ni and Au metallic particles

“…It is well known that bifunctional monomeric units with complementary groups (proton donor and proton acceptor) can be incorporated into the polymer backbone by self‐assembling. The self‐assembly of carboxylic acids as proton donors with pyridyl fragments as proton acceptors is most frequently used in the formation of hydrogen‐bonded structures 11, 12, 25, 28. We choose three commercially available pyridine derivatives, 4,4′‐bipyridyl, 1,2‐bis(4‐pyridyl)ethylene, and 4,4′‐azopyridine, to build supramolecular polymers, SP1 , SP2 , and SP3 , respectively, with above‐synthesized dicarboxylic acid, 2 (Scheme ).…”

“…The presence of the pyridyl ring that is an electron‐deficient aromatic heterocycle with a localized lone pair of electrons in the sp 2 orbital on nitrogen atom improves the electron transporting properties 29. Different from similar compounds reported in literature by us25 and others,12, 30 having liquid crystal behavior, this time we obtained polymers in the form of single crystals, which are also desirable in electronics. The structures of the derived supramolecular polymers were investigated by Fourier transform infrared (FTIR) and proton magnetic resonance ( 1 H NMR) spectroscopy and X‐ray single‐crystal diffraction.…”

“…Various structures based on multiple hydrogen bonds have been synthesized and investigated 7–10. However, a wide variety of main‐chain, side‐chain, combined, and network polymeric complex structures have also been built based on a single H‐bond between acceptor and donor (i.e., carboxyl and pyridyl functional groups) 11, 12…”

Dendrimer-like assemblies based on organoclays as multi-host system for sustained drug delivery

“…While MTM clay is found in the form of irregular aggregates of primary stacks consisting of multiple layers of aluminosilicate sheets with individual platelets, its fundamental units are comprised of two tetrahedral sheets sandwiched with edge-shared octahedral sheet [10] and the geometry of SiO 4 tetrahedrons on the surface of the aluminosilicates is conducive to cooperative hydrogen bonding [36]. Thus, MTM-APTES-CD units incorporates a quadruple DDAA pattern, which is self-complementary and thereby permits the formation of linear chains (Scheme 2a), cyclic dimmer (Scheme 2b) and cyclic multimer (Scheme 2c) DDAA array in solution and in the solid state [44].…”

“…Moreover, in optimal concentration of MTM-APTES-CD, the strategy of molecular tectonics [44][45][46] can be used to place neighboring (a), (b) and (c) in predetermined positions, giving ordered three-dimensional (3D) coils with high packing density (Scheme 2d), and then nucleation or starting to redirect growth into the branches/arms (Scheme 3a) and subsequently self-assembling them into nanoscale assemblies (Scheme 3b). Fig.…”