Phosphinated phenols from acid‐fragmentation of bisphenols and their unsymmetrical diamine derivatives for copolyimides

Four novel diamines (9–12) were prepared by a two‐step procedure from phosphinated phenols (1–4) that were prepared from acid‐fragmentation of four bisphenols, including bisphenol A, 4,4′‐isopropylidenebis(2,6‐dimethylphenol), cis(4‐hydroxyphenyl)cyclohexane, and 9,9′‐bis(4‐hydroxyphenyl)fluorene, followed by nucleophilic addition of 9,10‐dihydro‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO). Copolyimides based on (9–12)/4,4′‐diaminodiphenyl ether (ODA)/dianhydride were prepared. The structure‐property relationship on the copolyimides was discussed. Due to the structural similarity, (9)/ODA‐based copolyimides were compared with (10)/ODA‐based copolyimides, while (11)/ODA‐based copolyimides were compared with (12)/ODA‐based copolyimides. The dimethyl substitutents cause (10)/ODA‐based copolyimides to display higher Tg, modulus, dimensional stability, contact angle, and better solubility than (9)/ODA‐based copolyimides. (12)/ODA‐based copolyimides that exhibit fluorene moieties display higher Tg and thermal stability, but a lower contact angle and poorer solubility than (11)/ODA‐based copolyimides that exhibit cyclohexane moieties.