AbstractThe catalytic effects of three typical metal salts, HgCl2, Hgl2, and ZnCl2, on the ringopening polymerization of (PNCl2)3/(PNCl2)4in terms of the hard/soft concept for acids and bases were studied. The influence of the nature and the concentration of the initiators on the onset of gelation, the extent of polymerization, and on the polymer molecular weight is described. A new technique to follow the substitution reaction of chlorine in poly(dichlorophosphazene) by the 4‐methylphenoxy group is propose