Self‐assembly of supramolecular polymers into tunable helical structures

Abstract

ABSTRACT:There is growing interest in the design of synthetic molecules that are able to selfassemble into a polymeric chain with compact helical conformations, which is analogous to the folded state of natural proteins. Herein, we highlight supramolecular approach to the formation of helical architectures and their conformational changes driven by external stimuli. Helical organization in synthetic self-assembling systems can be achieved by the various types of noncovalent interactions, which include hydrogen bonding, solvophobic effects, and metal-ligand interactions. Since the external environment can have a large influence on the strength and configuration of noncovalent interactions between the individual components, stimulus-induced alterations in the intramolecular noncovalent interactions can result in dynamic conformational change of the supramolecular helical structure thus, driving significant changes in the properties of the materials. Therefore, these supramolecular helices hold great promise as stimuli-responsive materials.

Amplification of macromolecular helicity of dynamic helical poly(phenylacetylene)s bearing non-racemic alanine pendants in dilute solution, liquid crystal and two-dimensional crystal

“…Green et al demonstrated that copolymerization of achiral isocyanates with a tiny amount of optically active ones, or copolymerization of non-racemic isocyanates with a small enantiomeric excess (ee), produced optically active polyisocyanates with a greater excess of one-handed helical conformation, and termed these highly cooperative processes as the 'sergeants and soldiers effect' 7 and 'majority rule' , 8 respectively. These unique chiral amplification phenomena have been now observed in other varieties of covalent and non-covalent polymeric 6,9-14 and supramolecular helical systems [3][4][5][6] involving noncovalent helical assemblies consisting of chiral-achiral or chiral-chiral (R/S) small molecular components.…”

“…[1][2][3][4][5][6] Starting with the pioneering work carried out by Green et al 1,7,8 in polymeric systems using stiff, rod-like polyisocyanates, the substantial feature of the dynamic macromolecular helicity of polyisocyanates, which consist of right-and left-handed helical segments separated by energetically unfavorable, rarely occurring helical reversals, has been experimentally and theoretically revealed. Green et al demonstrated that copolymerization of achiral isocyanates with a tiny amount of optically active ones, or copolymerization of non-racemic isocyanates with a small enantiomeric excess (ee), produced optically active polyisocyanates with a greater excess of one-handed helical conformation, and termed these highly cooperative processes as the 'sergeants and soldiers effect' 7 and 'majority rule' , 8 respectively.…”

Recent advances in arylene ethynylene folding systems: Toward functioning

“…Ever since the folding behaviors of m-phenylene ethynylene (mPE) oligomers were first reported by Moore and coworkers in 1997 [26], mPE and related arylene ethynylene foldamer systems have been extensively developed and investigated [27][28][29][30][31][32][33][34][35][36][37][38][39]. Compared with many other foldamer systems containing non-natural, aromatic units, such as aromatic oligoamides [15,16,[40][41][42][43], arylene polymer/oligomers [21,24,25,[44][45][46][47][48][49][50][51][52][53][54][55], poly(phenylacetylene)s [21,23,[56][57][58], iso-polydiacetylenes [59,60], poly(N-propargylamides) [61], poly(N-octylcarbazole ethylene) [62], polydiacetylene [63], etc., arylene ethynylene foldable systems (AEFS) exhibit a distinct feature that they mainly rely on weak, noncovalent interactions among non-adjacent backbone units to realize folding...…”

Synthesis and Function of Double‐Stranded Helical Polymers and Oligomers

“…Lee and coworkers successfully synthesized double-stranded supramolecular metallopolymers (poly-10-Cu in Scheme 2) [52,53] from a bent-shaped bispyridine ligand bearing a dendron and Cu 2þ ion, which further self-assembled into a double helix, as confirmed by XRD and transmission electron microscopy (TEM) measurements with the aid of the density functional theory (DFT) calculations. Interestingly, the double helix formation is highly affected by the nature of the transition metals: the same bispyridine ligand reacted with a Pd 2þ ion to form a similar metallopolymer (poly-10-Pd), but resulting in a lamellar structure.…”