Investigation of the thermal properties of novel adamantane‐modified polybenzoxazine

Two novel structures of adamantane‐modified benzoxazines were synthesized from 4‐(1‐adamantyl)‐phenol through the incorporation of adamantane as a pendant group into the polybenzoxazine backbone. Both 1H‐NMR and Fourier transform infrared spectra were used to characterize these structures. The rigid structure of the adamantane tended to hinder the chain mobility (boat anchor effect) and substantially enhanced the thermal properties, including the glass‐transition temperature and decomposition temperature, especially for poly(6‐adamantyl‐3‐methyl‐3,4‐dihydro‐2H‐1,3‐benzoxazine). In the poly(6‐adamantyl‐3‐phenyl‐3,4‐dihydro‐2H‐1,3‐benzoxazine) system, however, the opposite result for the glass‐transition temperature was observed and it was interpreted as lower crosslinking density. The phenyl group was bulkier than the methyl group, and the movement of the molecular chain was hindered between bridging points during the curing process; this resulted in a lower crosslinking density and a lower glass‐transition temperature than those of poly(6‐adamantyl‐3‐methyl‐3,4‐dihydro‐2H‐1,3‐benzoxazine).