Low temperature curable benzoxazines are highly warranted due to the lower energy consumption and less energy output, which are highly required for the fabrication of industrial composite products and insulation of low melting microelectronics components. Hence, in the present study low temperature curable benzoxazines were synthesized using phenol (P1) and N, N-dimethyl group substituted phenol (P2) with two different amines such as dimethylaminopropyplamine (d1), dimethylaminodipropylenetriamine (d2) and paraformaldehyde through Mannich reaction. The synthesized benzoxazines were further converted into built-in ionic liquids using n-bromododecane. The structure property relationship was systematically studied and confirmed through the FTIR, 1H and 13C NMR analyses. The effect of long aliphatic chain from n-bromododecane in the curing behaviour of benzoxazines were studied using DSC. Among the benzoxazines, P1-d2 exhibited the lowest curing temperature of 196 °C and the presence of built-in ionic liquid further lowers the ROP about 40 °C from its maximum curing temperature. On the contrary, the thermal stability of the built-in ionic liquid polybenzoxazines was found to be lower than that of neat polybenzoxazines with decreased char yield values from 42% to 13% for poly(P1-d1). The curing kinetics of the built-in ionic liquid benzoxazines were performed using DSC at different heating rates. Using the Kissinger and Ozawa methods, the average activation energy (Ea) of the built-in ionic liquid benzoxazines were calculated and reported. The dielectric constant values of built-in ionic liquid polybenzoxazines were increased to 10.87 from 3.4 at 10 MHz frequency. The results from dielectric analysis suggests that the built-in ionic liquid polybenzoxazines can be used as a low temperature curable high dielectric material to meet the current demand for the efficient and effective processing of varied nature of industrial products and microelectronics components.