A new class of the thermally stable, hydrophobic, sustainable, and renewable eugenol (E)-based benzoxazines is synthesized using 4-aminobenzonitrile (abn) isophoronediamine (ipda) separately. Polybenzoxazines were formed by thermal ring-opening polymerization of respective monomers and confirmed by spectral analyses. TGA results indicated that the residual char yield value obtained at 850°C for poly(abn) and poly(ipda) are 36% and 32%, respectively. Poly(E-abn) showed better thermal stability than poly(E-ipda) due to the presence triazine cross-linkages in the matrix system. The water contact angle studies showed that poly(E-ipda) possesses better hydrophobic character than poly(E-abn) due to the presence of isophorone (alicyclic) group and allyl substitutions.