Multicomponent spiropolymerization of diisocyanides, alkynes and carbon dioxide for constructing 1,6-dioxospiro[4,4]nonane-3,8-diene as structural units under one-pot catalyst-free conditions

Carbon dioxide (CO₂) is a greenhouse gas whose release should be reduced to as low as possible. However, using this gas is another method for reducing the greenhouse effect. In this work, a novel multicomponent spiropolymerization was developed by using diisocyanides, alkynes and CO₂ based on catalyst-free one-pot polymerization under mild experimental conditions. A structural unit with 1,6-dioxospiro[4,4]nonane-3,8-diene as one of the main chains was instantly formed by converting CO₂ into spirosegments, and these resultant spiropolymers had high weight-average molecular weights (M_ws, up to 59000) and good yields (up to 87.7%). In detail, the effect of the diisocyanide monomers on the M_ws, yields and solubility of the resultant spiropolymers was investigated and discussed. The obtained spiropolymers showed excellent solubility and high thermal stability. Thus, a simple and high-atom-economical spiropolymerization for preparing new spiropolymers was established by taking full advantage of CO₂ and resulted in a unique spiroarchitecture by catalyst-free one-pot polymerization, which provided new kinds of spiropolymers for the materials science field.