A biuret-based quaternized polymer comprising a polymeric building block according to formula wherein A represents at least one unit of the following formulae, and wherein R 1, R 2, R 4, R 5 and R 6 are independently selected from the group consisting of C 2 -C 12 -alkanediyl and -(CH 2) c -[CH(Ra 6)-CH 2 -O] d -(CH 2) e -, wherein c is an integer ranging from 0 to 3; wherein d is an integer ranging from 1 to 100; wherein e is an integer ranging from 1 to 3; wherein Ra 6 is independently selected from the group consisting of hydrogen, alkyl, aryl, aralkyl, alkanediyl, arenediyl and -(CH 2) f -[CH(Ra 7)-CH 2 -O] g -(CH 2) h -, wherein f is an integer ranging from 0 to 3; wherein g is an integer ranging from 1 to 100; wherein h is an integer ranging from 1 to 3; wherein Ra 7 is independently selected from the group consisting of hydrogen, alkyl, aryl and aralkyl; wherein R 3 is selected from the group consisting of C 1 -C 12 -alkanediyl and -(CH 2) c -[CH(Ra 6)-CH 2 -O] d -(CH 2) e - wherein c is an integer ranging from 0 to 3; wherein d is an integer ranging from 1 to 100; wherein e is an integer ranging from 1 to 3; wherein Ra 6 is independently selected from the group consisting of hydrogen, alkyl, aryl, aralkyl, alkanediyl, arenediyl and -(CH 2) f -[CH(Ra 7)-CH 2 -O] g -(CH 2) h -, wherein f is an integer ranging from 0 to 3; wherein g is an integer ranging from 1 to 100; wherein h is an integer ranging from 1 to 3; wherein Ra 7 is independently selected from the group consisting of hydrogen, alkyl, aryl and aralkyl; wherein X is independently selected from the group consisting of wherein Z is independently selected from the group consisting of -CH 2 -, O, S; wherein z and z' are integers independently ranging from 1 to 6, wherein R 7 and R 8 are independently selected from the group consisting of hydrogen, alkyl, aryl, aralkyl and -CH 2 -CH 2 -(OCH 2 CH 2) y -OH, wherein y is an integer from 1 to 4; wherein in case X is pyridinium, R 1, R 2, R 4, R 5 and R 6 can also be -CH 2 -; wherein n is an integer ranging from 1 to 40; wherein D is selected from the group consisting of -CH 2 -CH -CH 2 -, -CH 2 -CH -CH 2 -, -(CH 2) i -[CH(Rd 1)-CH 2 -O] j -(CH 2) k - and -CH 2 -CH -(CH 2) l -[CH(Rd 2)-CH 2 -O] m -(CH 2) p -CH -CH 2 -, wherein i is an integer ranging from 0 to 3; wherein j is an integer ranging from 1 to 100; wherein k is an integer ranging from 1 to 3; wherein Rd 1 is independently selected from the group consisting of hydrogen, alkyl, aryl and aralkyl; wherein I is an integer ranging from 1 to 3; wherein m is an integer ranging from 1 to 100; wherein p is an integer ranging from 1 to 3; wherein Rd 2 is independently selected from the group consisting of hydrogen, alkyl, aryl and aralkyl, wherein the individual units A may be the same or different, and wherein the individual units D may be the same or different. wherein R 1, R 2, R 4, R 5 and R 6 are independently selected from the group consisting of C 2 -C 12 -alkanediyl and -(CH 2) c -[CH(Ra 6)-CH 2 -O] d -(CH 2) e -, wherein c is an integer ranging from 0 to 3; wherein d is an integer ranging from 1 to 100; wherein e is an integer ranging from 1 to 3; wherein Ra 6 is independently selected from the group consisting of hydrogen, alkyl, aryl, aralkyl, alkanediyl, arenediyl and -(CH 2) f -[CH(Ra 7)-CH 2 -O] g -(CH 2) h -, wherein f is an integer ranging from 0 to 3; wherein g is an integer ranging from 1 to 100; wherein h is an integer ranging from 1 to 3; wherein Ra 7 is independently selected from the group consisting of hydrogen, alkyl, aryl and aralkyl; wherein R 3 is selected from the group consisting of C 1 -C 12 -alkanediyl and -(CH 2) c -[CH(Ra 6)-CH 2 -O] d -(CH 2) e - wherein c is an integer ranging from 0 to 3; wherein d is an integer ranging from 1 to 100; wherein e is an integer ranging from 1 to 3; wherein Ra 6 is independently selected from the group consisting of hydrogen, alkyl, aryl, aralkyl, alkanediyl, arenediyl and -(CH 2) f -[CH(Ra 7)-CH 2 -O] g -(CH 2) h -, wherein f is an integer ranging from 0 to 3; wherein g is an integer ranging from 1 to 100; wherein h is an integer ranging from 1 to 3; wherein Ra 7 is independently selected from the group consisting of hydrogen, alkyl, aryl and aralkyl; wherein X is independently selected from the group consisting of wherein Z is independently selected from the group consisting of -CH 2 -, O, S; wherein z and z' are integers independently ranging from 1 to 6, wherein R 7 and R 8 are independently selected from the group consisting of hydrogen, alkyl, aryl, aralkyl and -CH 2 -CH 2 -(OCH 2 CH 2) y -OH, wherein y is an integer from 1 to 4; wherein in case X is pyridinium, R 1, R 2, R 4, R 5 and R 6 can also be -CH 2 -; wherein n is an integer ranging from 1 to 40; wherein D is selected from the group consisting of -CH 2 -CH -CH 2 -, -CH 2 -CH -CH 2 -, -(CH 2) i -[CH(Rd 1)-CH 2 -O] j -(CH 2) k - and -CH 2 -CH -(CH 2) l -[CH(Rd 2)-CH 2 -O] m -(CH 2) p -CH -CH 2 -, wherein i is an integer ranging from 0 to 3; wherein j is an integer ranging from 1 to 100; wherein k is an integer ranging from 1 to 3; wherein Rd 1 is independently selected from the group consisting of hydrogen, alkyl, aryl and aralkyl; wherein I is an integer ranging from 1 to 3; wherein m is an integer ranging from 1 to 100; wherein p is an integer ranging from 1 to 3; wherein Rd 2 is independently selected from the group consisting of hydrogen, alkyl, aryl and aralkyl, wherein the individual units A may be the same or different, and wherein the individual units D may be the same or different.