A novel boron–silicon–alkynyl hybrid copolymer

Abstract

A novel boron–silicon–alkynyl hybrid copolymer (BSD) was synthesized by condensation polymerization of 1,3-diethynylbenzene with dichloromethylsilane and boron trifluoride etherate. Fourier transform infrared and ¹H-, ¹³C-, and ²⁹Si-nuclear magnetic resonance spectroscopies were used to confirm the structures of the copolymers. Thermogravimetric analysis and differential scanning calorimetry showed that the polymer exhibited excellent heat resistance and thermo-oxidative stabilities under nitrogen and air. The cure cross-linking reaction mechanisms of the BSD were related to Diels–Alder intermolecular cyclization involving two C≡C bonds and hydrosilylation reaction between Si–H and C≡C bonds. The $T_{d_5}$ of the BSD was above 591°C and 530°C under nitrogen and air, respectively. The residues at 1000°C were above 88% under nitrogen and 25% in air. X-ray diffraction was used to study the formation of ceramics. The precursor for ceramics (β-SiC, α-SiC, and B₄C) was formed at 1600°C under an argon atmosphere. The thermo-oxidative stabilities of the copolymers were attributed to the existing organic groups of alkynyl and inorganic elements of silicon and boron.