To purposely design high performance polybenzoxazine, fundamental studies are conducted. A phenol/aniline type monofunctional benzoxazine monomer, PH-a, is synthesized and highly purified to study the intrinsic thermal ring-opening polymerization of benzoxazines without the influence of any impurity. DSC studies show that polybenzoxazines of 1,3-benzoxazines can be obtained by both the traditional thermally accelerated (or activated) polymerization, where impurities or purposefully added initiators are involved in the reaction; or, by the classic thermal polymerization, where only heat is enough to initiate the reaction. Therefore, hydrogen bonding is designed in the monomer to lower the polymerization temperature. Intermolecular and intramolecular hydrogen bonding behavior are studied by FT-IR and NMR by using two amide containing model compounds pHBA-a and oHBA-a. Thus, smart ortho-structure molecular design is a preferred way to make high performance polybenzoxazine, including hydrogen bonding and latent catalyst effects on easy synthesis, low polymerization temperature, high thermal stability, and low dielectric constant.