Fluorine/adamantane modified cyanate resins with wonderful interfacial bonding strength with PBO fibers

Novel compound (AEAF) with both cage-type adamantanes and fluorine-containing structures was synthesized from bisphenol AF, 1-adamantyl chloride and epichlorohydrin through successive esterification and O-alkylation reaction, which was then introduced into the curing networks of bisphenol A cyanate ester (BADCy) resins through copolymerization, to obtain AEAF-co-BADCy resins. AEAF presented low polarizability & dipole density, rigid cage adamantane, and stable CF₃ group. When the mass fraction of AEAF was 6 wt%, AEAF-co-BADCy resins displayed the minimum real part (ε′_r), imaginary part (ε”_r) of complex permittivity, and dielectric loss tangent (tanδ) values, which were 2.49, 0.012, and 0.0048, respectively. And the corresponding wave transmission efficiency (T) was 92.3%, significantly higher than that of pure BADCy (86.6%). AEAF-co-BADCy resins also possessed excellent mechanical properties and better interfacial compatibilities with poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers. The corresponding flexural strength (126.5 MPa) and impact strength (15.2 kJ m⁻²) were increased by 16.6% and 47.6%, in comparison to pure BADCy (flexural strength of 108.5 MPa and impact strength of 10.3 kJ m⁻²). Meantime, the single fiber pull-out strength of PBO fibers/AEAF-co-BADCy (6 wt% AEAF) micro-composites also displayed an increase from 3.1 MPa (PBO fibers/BADCy) to 3.4 MPa.