Mannich-type polycondensation with 4,4’-diaminodiphenylmethane (DDM), 2,2-bis(4-hydroxyphenol) propane (BPA) and paraformaldehyde (PF) in different solvents was carried out to prepare main-chain benzoxazines. When pure CHCl3 was used as the solvent, the decomposition rate of PF in CHCl3 was very slow, thus preventing gelation caused by the formation of triazine in the early reaction, producing P(B-D)1 composed of partially closed and unclosed structures. The addition of alkaline triethylamine into CHCl3 (CHCl3/triethylamine = 6:1) greatly en...
