The cardo tetrafunctional benzoxazines (BZ-aP-ffa, P-aP-ffa and BBA-aP-ffa) were synthesized from bis-phenols (phenolphthalein, bisphenol-Z and bisphenol-BA), paraformaldehyde, aminophenol and furfurylamine under appropriate experimental conditions. Their structural, thermal, hydrophobic, morphology and dielectric properties were characterized using modern analytical methods. Thermal studies indicate that the poly(P-aP-ffa) possesses better thermal stability (char yield 61%) than that of other two polybenzoxazines, viz. poly(BZ-aP-ffa) and poly(BBA-aP-ffa) (char yield 50 and 56%, respectively). Polybenzoxazine (P-ap-ffa) composites reinforced using varied weight percentages (10, 20, 30, 40 and 50 wt%) of GPTMS-functionalized vermiculite were prepared and the properties studied and compared with those of neat benzoxazine matrices. The values of water contact angle of neat poly(BZ-aP-ffa), poly(BBA-aP-ffa) and poly(P-aP-ffa) are found to be 142°, 141° and 142°, respectively, while that of vermiculite-reinforced poly(P-aP-ffa) composites have a water contact angle of 135° regardless of vermiculite content. A similar study indicated that the values of dielectric constant of neat polybenzoxazine matrix, 10, 20, 30, 40 and 50 wt% of GPTMS-functionalized vermiculite-reinforced poly(P-ap-ffa) composites are 3.34, 2.11, 2.01, 1.92, 1.86 and 1.84, respectively. The value of the dielectric constant is appreciably lowered to the extent of an ultra-low-k level, when vermiculite concentration increases. Results indicated that benzoxazines and composites developed in the present work can be used in the form of sealants for printed circuit boards in the field of microelectronics.