To obtain a new polymer composition having a phosphono-substituent by using a phosphono-substituted carboxylic acid (ester) and a functional material polymerizable with the acid as essential components.

The objective composition contains (A) an aliphatic or aromatic phosphono-substituted carboxylic acid or its ester, preferably phosphonosuccinic acid or its dimethyl ester and (B) a mono or polyfunctional material polymerizable with the component A, preferably ethylene glycol, propylene glycol, neopentyl glycol, 1,4-dimethylolcyclohexane, glycerol, succinic acid, terephthalic acid, phthalic acid anhydride, naphthalic acid, naphthalic acid anhydride, an aliphatic or aromatic polyamine, ethylenediamine, an aliphatic or aromatic polyisocyanate or a polyepoxide.