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–C6H4–O(CH2)4O–C6H4–CN and NC–C6H4–O(CH2)4O–Ar–O(CH2)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 (νD′ 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.