Fluorobetaine copolymer and fire fighting foam concentrates therefrom

A fluorocopolymer comprising units represented by the following formula:

• wherein Rf represents a perfluorinated alkyl group, optionally interrupted by oxygen, having at least 3 carbon atoms;
• each R1 is independently chosen from a C1-C20 hydrocarbylene;
• R8 is chosen from a C1-C20 hydrocarbyl or hydrogen;
• R2 is chosen from hydrogen, fluorine, or a C1-C4;
• s is 0 or 1;
• Y is benzyl or carbonyl, preferably carbonyl;
• RB is a group with the formula CaNbOcSfH2(a−e+b+1−2d having a structure which incorporates at least one betaine group of the formula (N+—CnH2n—CO2−) or (N+—CnH2n—SO3−) wherein a is an integer from 4-25, b is an integer from 1 to 4, c is an integer from 2 to 15, d is an integer from 0 to 3, e is an integer from 0 to 4, f is an integer from 0 to 4, the sum of e and f is from 1 to 4;
• n is independently chosen from an integer from 1 to 5;
• and R3 is chosen from hydrogen or a C1-C4 hydrocarbyl;
• and x is an integer from 1 to 10, y is an integer from 4 to 200, and the ratio of y:x is at least 1:1.