The reaction of [NPCl2](n) with substoichiometric amounts (x < 0.5) of the biphenol (HO)(2)C12H8 and K2CO3 followed by pr(e)cipitation into cold water allowed the isolation of the stable chlorine-containing copolymers {[NP(O2C12H8)](1-x)[NPCl2](x)}(n) (1) [(O2C12H8) = 2,2'-dioxy-1,1'-biphenyl], with x = 0.12 (1a), 0.28 (1b), and 0.43 (1c), having M-w of the order of 10(6), and the chain structure of strictly alternating copolymers. Larger x values resulted in the formation of hydrolyzed insoluble materials with no controlled composition. The polymers 1 could be hydrolyzed in THF/water solutions at rates that varied from very slow (x = 0.12 at room temperature) to very fast (x = 0.43 at reflux). However, in water suspensions the polymers 1 with x < 0.5 are not chemically affected, and only a reduction of the average M-w (as measured by GPC) could be observed at 100 degrees C. Molecular dynamics simulations were performed on model compounds of polymer 1. The results of these calculations explain the hydrolytic behavior of the polymer.