Herein, three novel bi-functional benzoxazines were synthesized using aurin as the precursor phenol with three different aromatic amines (i.e.) aniline, fluoroaniline, and trifluoromethylaniline with paraformaldehyde through Mannich condensation. The structural confirmation was done using FTIR and proton NMR. The effects of substituents present in the amines on the curing behaviour and thermal stability were studied using DSC and TGA. The aurin based trifluoromethyl substituted benzoxazine shows better thermal stability than that of the other two benzoxazines and it was selected for the preparation of composites with varying weight percentages of graphitic carbon nitride derived from dicyandiamide (Dicy-GCN) to utilize them for high k applications. The dielectric behaviour and thermal properties of both neat polymer matrix and composites were studied and compared. The 15 wt% Dicy-GCN reinforced composite shows the highest dielectric constant value of 10.25, with a low dielectric loss value of 0.046 at 1 MHz frequency. The polybenzoxazine composites developed show better thermal stability and superhydrophobic behaviour than those of neat polybenzoxazine matrix. These properties ascertain that the aurin based bifunctional polybenzoxazines and its composites can be considered for high-performance high k applications.