Poly(alkylene phosphate)s by polycondensation of phosphonic diamides with diols

Polycondensation of diols with phosphonic bis(dialkylamide)s leads to high‐molecular‐weight polyphosphites (M̄n up to 4 · 104). Model reactions of 1‐butanol, 2‐butanol and phenol with phosphonic bis(diethylamide) (1) were studied and it was established, that these reactions exhibit characteristic induction periods. Linearization of the kinetic curves after addition of amines prior to reaction enabled us to postulate the mechanism of esterification, involving activation of 1 by hydrogen‐bonding to amines. However, the major side reaction lowering the degree of polymerization was found to be dealkylation of the formed ester units by added and/or evolved amine. Therefore, in order to increase the rate of polycondensation and to prevent the formed polymer chain from breaking down by dealkylation, the process was conducted at increased temperature (90°C) in a nonsolvent for the polymer of higher molecular weight. Thus, the polymer separates from the major solution and becomes less prone to dealkylation.