Novel Benzoxazine Monomers Containing p-Phenyl Propargyl Ether: Polymerization of Monomers and Properties of Polybenzoxazines

Novel benzoxazine monomers containing arylpropargyl ether were prepared, and highly thermally stable polybenzoxazines were obtained by the thermal cure of the monomers. One monomer is a monofunctional benzoxazine, 4-propargyloxyphenyl- 3,4-dihydro-2 H -1,3-benzoxazine (P-appe), and the other is a bifunctional benzoxazine, bis(4-propargyloxyphenyl-3,4-dihydro-2 H -1,3-benzoxazinyl)isopropane (B-appe). The chemical structures of these novel monomers were confirmed by IR and 1 H NMR. The cure behavior of the monomers, P-appe and B-appe, and the properties of the resulting polymers were studied in comparison with 4-phenyl-3,4-dihydro-2 H -1,3-benzoxazine (P-a) and bis(4-phenyl-3,4-dihydro-2 H -1,3-benzoxazinyl)isopropane (B-a) as typical benzoxazine monomers without propargyl groups. DSC cure of both P-appe and B-appe showed a single exotherm corresponding to the ring-opening polymerization of oxazine ring and cross-linking of arylpropargyl ether group at almost the same temperature range as P-a and B-a. The T g values of polybenzoxazines derived from propargyl-containing monomers, PP-appe and PB-appe, were higher by ca. 100 and 140 °C than those of typical polybenzoxazines without propargyl groups, PP-a and PB-a, respectively. The storage moduli of PP-appe and PB-appe were maintained constant up to higher temperature for ca. 100 °C than that of PP-a and PB-a. The higher thermal stability of the novel polybenzoxazines, PP-appe and PB-appe, than that of the typical polybenzoxazines, PP-a and PB-a, was proved from thermogravimetric analyses.