Supramolecular Multiblock Copolymers Featuring Complex Secondary Structures

Abstract

This contribution introduces main-chain supramolecular ABC and ABB'A block copolymers sustained by orthogonal metal coordination and hydrogen bonding between telechelic polymers that feature distinct secondary structure motifs. Controlled polymerization techniques in combination with supramolecular assembly are used to engineer heterotelechelic π-sheets that undergo high-fidelity association with both helical and coil-forming synthetic polymers. Our design features multiple advances to achieve our targeted structures, in particular, those emulating sheet-like structural aspects using poly(p-phenylenevinylene)s (PPVs). To engineer heterotelechelic PPVs in a sheet-like design, we engineer an iterative one-pot cross metathesis-ring-opening metathesis polymerization (CM-ROMP) strategy that affords functionalized Grubbs-II initiators that subsequently polymerize a paracyclophanediene. Supramolecular assembly of two heterotelechelic PPVs is used to realize a parallel π-sheet, wherein further orthogonal assembly with helical motifs is possible. We also construct an antiparallel π-sheet, wherein terminal PPV blocks are adjacent to a flexible coil-like poly(norbornene) (PNB). The PNB is designed, through supramolecular chain collapse, to expose benzene and perfluorobenzene motifs that promote a hairpin turn via charge-transfer-aided folding. We demonstrate that targeted helix-(π-sheet)-helix and helix-(π-sheet)-coil assemblies occur without compromising intrinsic helicity, while both parallel and antiparallel β-sheet-like structures are realized. Our main-chain orthogonal assembly approach allows the engineering of multiblock copolymer scaffolds featuring diverse secondary structures via the directional assembly of telechelic building blocks. The targeted assemblies, a mix of sequence-defined helix-sheet-coil and helix-sheet-helix architectures, are Nature-inspired synthetic mimics that expose α/β and α+β protein classes via de novo design and cooperative assembly strategies.

Macromolecular Superstructures: A Future Beyond Single Chain Nanoparticles

“…Moving from oligomers relying on iterative synthesis to polymers, the group of Weck, developed a remarkable toolbox of monomers that induce secondary structures in synthetic polymer strands (Figure ). To mimic sheet like architectures, rigid poly( p ‐phenylene vinylene) species (PPVs) have been employed, which can be synthetically accessed via living ring‐opening metathesis polymerization (ROMP) of substituted [2.2]paracyclophane‐1,9‐dienes (pCpd) . In addition to the rigidity of the conjugated polymer backbone, the PPV strands allow to monitor their face‐to‐face π‐π stacking through fluorescence quenching upon assembly of the strands .…”

“… Schematic Representation of the Target Supramolecular Block Copolymers Comprising π‐Sheets, Helices, and Coils via a Plug‐and‐Play Strategy Utilizing Orthogonal Metal Coordination and Hydrogen Bonding . Reprinted with permission from ( J.…”

Poly(arylenevinylene)s through Ring‐Opening Metathesis Polymerization of an Unsymmetrical Donor‐Acceptor Cyclophane

“…In both cases,t he linear relationship of [9b]/[I] with molecular weight, coupled with low dispersities,i s supportive of ac ontrolled polymerization that proceeds in the absence of early termination, chain-transfer,a nd backbiting. [27,28] Thec ontrolled ROMP is remarkable in wake of the electronically ambiguous character of MEH-BT pCpd. Introduction of as ubstituted norbornene monomer,w herein subsequent ROMP afforded conjugatednonconjugated block copolymers,e xhibited clean shifts in molecular weight and continued narrow dispersities were observed ( Figure 2).…”

A New Strategy to Synthesize α,ω‐Dihydroxy Multiblock Copolymers via [CpRu(CH3CN)3]PF6/Quinaldic Acid Catalyst

“…Multiblock copolymers (MBCs) containing random (ABBAAB) and alternating (ABABAB) segments have attracted significant scientific interest, owing to their resulting microphaseseparated morphologies, different thermal and mechanical properties with a growing list of realized and potential applications. [1][2][3][4][5] Currently, major synthesis methods to get MBCs relying on polycondensation can be divided into two categories, that is, click chemistry and coupling chemistry of α,ω-dihydroxy to form urethane, ester, or amide bonds. [6][7][8][9][10][11][12] Although some of the MBCs have been successfully prepared and got some applications, those MBCs were mainly focused on thermoplastic materials with superior performance.…”