Controlled Synthesis of Cyclic‐Helical Polymers with Circularly Polarized Luminescence

Abstract

Cyclic polymers attract attention because of their endless structure and unique properties, which differ from the linear analogs. However, the synthesis of cyclic polymers is difficult and prohibits their functions and applications. In this study, we reported chiral cyclic Pd II -catalysts that initiate a living ring-expansion polymerization of isocyanides, yielding a single-handed cyclic-helical poly(phenyl isocyanide), with predictable molecular weight (M n ) and low dispersity (M w /M n ), in good yield. Using this method, cyclic bottlebrush polymers were prepared via the grafting-onto strategy. The cyclic topology was confirmed using various spectroscopic data and atomic force microscope observation. Moreover, the cyclic polymer brushes, comprising of a one-handed helical backbone, showed interesting photoluminescence and circularly-polarized luminescence.

Selective synthesis of helical polymers

“…Copyright (2021) Wiley‐VCH; (C) synthesis of cyclic polymers and linear analogues. Reproduced with permission 47 . Copyright (2022) Wiley‐VCH); (D) helix‐sense‐selective polymerization with ((R)‐ or (S)‐BINAP) ligands (R A refers to aminoisobutyric acid decyl ester, R L and R D refer to l ‐ and d ‐alanine decyl ester via an amide linkage.…”

“…Besides the above optically active helical polyisocyanides synthesized by chiral monomers with wide applications such as chiral recognition, enantiomeric separation, optical materials and others, various of preferred-handed helical polyisocyanides were obtained by helix-senseselective polymerization of achiral isocyanide. [43][44][45][46][47] As demonstrated in Figure 4A, the chiral LA was used as chiral additive to induce the helix-sense-selective polymerization of achiral isocyanides and enantiomeric phenyl isocyanide bearing an (R)-or (S)-alanine pendent. 43 When the helical polyisocyanides were used as macroinitiators with chiral LA in second block copolymerization, the block polymers being obtained had almost the same handedness to the first block polymers.…”

“…Reproduced with permission. 47 Copyright (2022) Wiley-VCH); (D) helix-sense-selective polymerization with ((R)-or (S)-BINAP) ligands (R A refers to aminoisobutyric acid decyl ester, R L and R D refer to L-and D-alanine decyl ester via an amide linkage. Reproduced with permission.…”

Thermotropic chirality enhancement of nanoparticles constructed from foldamer/bis(amino acid) complexes

“…Artificial foldamers are often used to construct chiral materials because they can fold into a compact helical conformation, [16][17][18][19] which is stabilized by non-covalent interactions such as solvophobic interactions and π-π stacking interactions in the foldamer main chain. 20,21 In particular, they can undergo a conformation transition in response to temperature.…”

Synthesis and properties of helical polystyrene derivatives with amino acid side groups

“…1,2 Studying other non-natural materials such as helical polymers is attractive to scientists because of the close relationship between helical structures and complex living systems. [3][4][5][6][7][8][9][10][11][12][13][14][15][16] Various polymers containing helical structures have been prepared for a wide range of applications in chiral recognition, [17][18][19] enantiomer separation [20][21][22] and chiral response. 23,24 Designing and synthesizing vinyl polymers with stable helical conformations remains challenging.…”