Development of multifunctional chalcone-phthalonitrile-cyanate ester hybrids for thermal, flame-resistant,...

A series of chalcone-based phthalonitrile-cyanate ester hybrids, namely poly(CB-PN-CE), were synthesized via a stepwise reaction, in which chalcone derivatives serve as bridges between phthalonitrile (PN) and cyanate ester (CE) terminal groups. The structures of the synthesized chalcone-based phthalonitriles and hybrid cyanate esters were confirmed by FT-IR, NMR, and MASS spectroscopy. DSC analysis revealed two distinct exothermic peaks, corresponding to the sequential polymerization of cyanate ester (T _p¹ ≈ 170-220 °C) and phthalonitrile (T _p² ≈ 310-340 °C). Upon UV irradiation, the chalcone moieties of CB-PN-CE underwent [2 + 2] cycloaddition, forming cyclobutane rings. The cured poly(CB-PN-CE) hybrids exhibited excellent thermal stability (T _{d ⁱ} > 416 °C), high char yield (up to 72%), and flame-retardant behavior with a V-0 rating. The hybrids also exhibited favorable dielectric characteristics, with dielectric constants of 3.87-3.98 and low dielectric losses of 0.0070-0.0085 at 1 MHz. Furthermore, UV exposure at 365 nm for 72 h demonstrated excellent photostability of the poly(CB-PN-CE) hybrids. The synergistic incorporation of phthalonitrile, cyanate ester, and chalcone moieties endows the resulting hybrids with excellent thermal stability, flame resistance, UV stability, and favorable dielectric properties, making them promising candidates for high-performance thermosetting materials for thermally stable, flame-retardant, and electronic applications.