DEGRADATION OF POLY[BIS(ETHYLAMINO)PHOSPHAZENE] IN AQUEOUS-SOLUTION

Three polymers of poly[bis(ethylamino)phosphazene] (PBEAP) containing different amounts of the residual P-Cl moieties, which had been hydrol yzed into P-OH in the following sample purification processes, were pr epared by substitution of the chlorines on poly(dichlorophosphazene) w ith ethylamine. Only the polymer which had the highest side-chain cont ent of ethylamino groups (ca. 93%) had a film-forming ability and a cr ystalline nature. The hydrolytic degradation of PBEAP in acidic soluti ons was investigated using the solution viscosity data obtained as a f unction of standing time. Acetic acid, 0.5 and 1 N, pure acetic acid, and 2,2,2-trifluoroethanol were used as solvents. The degradation was composed of random breaking processes along the polymer chain, especia lly at the -N=P(OH)(2)- and -N=P(OH)(NHC2H5)-units, and an unzippering -like breaking process which was started at the chain ends produced by the former random breaking. The random breaking caused an abrupt decr ease in viscosity at the beginning of the degradation, and on the cont rary, the unzippering-like breaking appeared as a gradual decrease in viscosity at the later stages of degradation. The total rate of degrad ation depended on the concentration of the ethylamino groups.