Selective Synthesis of Single‐Handed Helical Polymers from Achiral Monomer and a Mechanism Study on Helix‐Sense‐Selective Polymerization

Abstract

Inspired by the exquisite helices in Nature,f abrication of helical materials with controlled handedness has attracted considerable attention. Herein, we report on precis synthesis of single left-and right-handed helical polyisocyanides through living polymerization of achiral monomers using chiral palladium catalysts under helix-sense-selective manner.Mechanism study revealed that the yielded helices with opposite handedness showed different activity of the living chain end. The helix with unfavored handedness was selfterminated, while the one with favored handedness showed high activity and could undergo chain propagation to form ah igh molecular weight polymer with maintained singlehanded helicity.

Helicity‐ and Molecular‐Weight‐Driven Self‐Sorting and Assembly of Helical Polymers towards Two‐Dimensional Smectic Architectures and Selectively Adhesive Gels

“…Only left‐handed polymer chains could be observed on the AFM image of M ‐poly‐ 1m ‐Py, while AFM images of P ‐poly‐ 1m ‐Py polymers only showed right‐handed helical chains (Figure S15, SI). The ee h values of the polymers estimated by AFM were generally agree with the CD analyses, and were all up to 99 % [32, 48] . These studies convinced the single‐handed helicity of the synthetic polyisocyanides bearing Py‐ and Np‐probes.…”

“…The chiral ligand and the Pd II ‐terminus were removed after the polymerization [32] . The helical structures were quite stable, no racemization was observed in THF at 55 °C for one week, probably due to the stabilization by the long alkyl tails and amide functions (Figure S16, SI) [48] …”

“…Polyisocyanide is generally prepared via the polymerization of the corresponding isocyanide monomer by using transition metal complexes or cations as catalysts [43–46] . However, the recent emerging mononuclear alkyne‐palladium(II) catalysts is of particular useful, which can catalyze living polymerizations of various isocyanides and efficiently produce stereoregular polyisocyanides in high yields with expected molecular weight ( M n ) and low polydispersity ( M w / M n ) [32, 47, 48] . Taking advantage of this method, a variety of polyisocyanides in different topologies and broad applications have been facilely prepared [49–54] .…”

“…Recently, we have realized a controlled synthesis of single‐handed helical polyisocyanide from achiral isocyanide monomer using the alkyne‐Pd II catalyst carrying chiral phosphine ligands [32, 48] . The large optical activity of the resulting polyisocyanides was solely from the single‐handed helicity, and inexistence of any other chiral moieties on the chain ends nor on the pendants.…”

A Chiral Metal-Organic 1D-Coordination Polymer Upon Complexation of Phenylene-Bridged Bipyrrole and Palladium (II) Ion

“…expectation that BPI/Pd polymer can form a helical CP by attachment of chiral substituent groups on iminonitrogens (Huang et al, 2018;Wang et al, 2019;Zhou et al, 2020).…”