Patent ID: 7226987

Claim:
An aromatic polymer phosphonic acid derivative, which is represented by the formula (2), wherein —Z— represents —SO 2 — or —CO—, x and y are average molar ratios in the polymer and respectively represent 0.01 to 0.99, provided that the sum of x and y is 1; —Ar— represents a phenylene group or a biphenyldiyl group, and said —Ar— may have one or more substituents; R and R′ each independently represent an alkyl group; m and n independently represent an average number of substituents per unit structure (—Ar—O—) of an aromatic polymer compound (1), m is 0 to 8, n is a positive number of 8 or less, and the sum of m and n is 8 or less; or an aromatic polymer phosphonic acid derivative whose free acid form is represented by the formula (3): wherein —Z—, x, y, —Ar—, m and n have the same meaning as above, and R″ represents hydrogen or an alkyl group.