Supramolecular Diblock Copolymers Featuring Well‐defined Telechelic Building Blocks

Abstract

We report supramolecular AB diblock copolymers comprised of well-defined telechelic building blocks. Helical motifs, formed via reversible addition-fragmentation chain-transfer (RAFT) or anionic polymerization, are assembled with coil-forming and sheet-featuring blocks obtained via atom-transfer radical polymerization (ATRP) or ring-opening metathesis polymerization (ROMP). Interpolymer hydrogen bonding or metal-coordination achieves dynamic diblock architectures featuring hybrid topologies of coils, helices, and/or π-stacked sheets that, on a basic level, mimic protein structural motifs in fully synthetic systems. The intrinsic properties of each block (e.g., circular dichroism and fluorescence) remain unaffected in the wake of self-assembly. This strategy to develop complex synthetic polymer scaffolds from functional building blocks is significant in a field striving to produce architectures reminiscent of biosynthesis, yet fully synthetic in nature. This is the first plug-and-play approach to fabricate hybrid π-sheet/helix, π-sheet/coil, and helix/coil architectures via directional self-assembly.

Coil‐helix and sheet‐helix block copolymers via macroinitiation from telechelic ROMP polymers

“…The PIC block imparts an excess helical sense resulting in an optically active diblock copolymer. Similar to our reported supramolecular sheet‐helix bcp, polymerization from the π‐π stacked PPV‐Pd sheet does not impact the intrinsic helicity of the PIC block.…”

“…The vinyl ether CTA installs an ω‐ethynyl‐palladium (II) species upon the chain end of a PNB or PPV, which, in turn, can initiate the polymerization of a phenyl isocyanide. The coil‐helix and sheet‐helix copolymers, in line with our previous reports on similar supramolecularly‐bound bcps, retain the helicity and fluorescence of the poly(isocyanide) (PIC) and PPV blocks.…”

“…The resulting coil‐helix bcp contains an optically‐active helical segment with an excess P‐ helical screw sense, as observed by CD spectroscopy, related to the chiral side‐chains (Fig. , solid line) . Whereas the features are similar to that of PIC‐Pd , we do observe a slight decrease in molar elipticity in PNB‐ b ‐PIC , likely owing to some degree of racemization in the presence of the achiral rigid‐coil PNB, as bcps containing helical blocks with achiral additives are known to cause changes in the amplitude .…”

“…Bcps containing helical features, for instance, offer potential in applications such as chiroptical switching and liquid crystals . Bcps can be engineered via both noncovalent and covalent strategies, both of which are modular and can afford polymeric scaffolds comprising multiple different polymer blocks within a single macromolecular species.…”

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 .…”