Oxygen as a Crucial Comonomer in Alkyne-Based Polymerization toward Functional Poly(tetrasubstituted furan)s

Oxygen (O2), one of the most essential gases, is abundant, cheap, nontoxic, and environmentally friendly. However, O2 has not been used as a monomer to synthesize polymers yet, probably because of the difficulty in chain growth. In this paper, we develop a new alkyne-based polymerization in which O2 serves as a comonomer under mild reaction conditions. Functionalized diynes could react with O2 in the presence of Pd(OAc)2/ZnCl2 in N,N-dimethylacetamide (DMAc) and perfluorodecalin under atmospheric oxygen. Soluble poly(tetrasubstituted furan)s with high weight-average molecular weights (Mw up to 14 900) were obtained in high yields (up to 86%). The ratio of isomeric repeating units of P1(m) can be identified by analyzing the components of model reaction products. Moreover, P1(6) could function as a fluorescent sensor for explosive detection with superamplification quenching effect. P2–P5 with conjugated structures possess large two-photon absorption cross sections up to 1570 GM, showing great potential as two-photon absorption materials. Thus, this work not only establishes a powerful O2-involved alkyne-based polymerization but also provides poly(tetrasubstituted furan)s with versatile properties, which are potentially applicable in optoelectronic and biological fields.