Helical Polyallenes: From Controlled Synthesis to Distinct Properties.

Polyallenes with appropriate pendants can form stable helices and exhibit significant optical activity. These helical polyallenes contain reactive double bonds that allow for further functionalization, making them a class of chiral functional materials with broad application prospects. This review article delves into the intricacies of synthesizing well-defined helical polyallenes through controlled synthetic methodologies, including helix-sense selective living polymerization, regioselective and asymmetric living polymerization, and one-pot block copolymerization of allenes with aryl monomers. The systemically outlined characteristics of the resulting helical polyallenes and related copolymers are summarized include their unique chiroptical properties, stimuli-responsiveness, helix-induced chiral self-assembly, and circularly polarized luminescence (CPL). Additionally, current challenges and future perspectives in the research of controlled synthesis, functionalities, and applications of helical polyallenes are discussed in detail.