Polycyclotrimerization of dinitriles: A new polymerization route for the construction of soluble nitrogen-rich polytriazines with hyperbranched structures and functional properties

A new synthetic route to nitrogen-rich hyperbranched polymers is developed. The polycyclotrimerizations of dinitriles [NC-C₆H ₄-O(CH₂)₄O-C₆H₄-CN and NC-C₆H₄-O(CH₂)₄O-Ar-O(CH ₂)₄O-C₆H₄-CN Ar = isopropylidenebis(1,4-phenylene), 9,9-fluorenylenebis(1,4-phenylene) and 1,2-diphenylethenylenebis(1,4-phenylene)] catalyzed by trifluoromethanesulfonic acid proceed smoothly in 1,2-dichlorobenzene at room temperature, affording hyperbranched poly(triazine)s with high degree of branching (DB ∼63%) in high yields (up to 74.7%). All the polymers are soluble and film-forming. The polymers are thermally and morphologically stable, showing high thermal-degradation and glass-transition temperatures up to 363 and 126.5 C, respectively. They are optically transparent, allowing almost all visible and IR lights to transmit through. The polymer thin films show high refractive indices (n = 1.7456-1.5857) in a wide spectral region (400-1600 nm) as well as high Abbe numbers (ν_D′ up to 187.4) and low optical dispersions (D′ down to 0.005). Polymerization of tetraphenylethene-containing dinitrile generates a polymer with aggregation-induced emission characteristic, enabling it to be utilized as a sensitive and selective fluorescent chemosensor for ruthenium(III) ion detection.