Copolymer and its use as coating

A polymer comprising:

• phenylene methylene units obtained from a first monomer of the general formula (I)
• wherein Z1 is selected from the group consisting of fluoro, chloro, bromo, iodo, hydroxyl, toluene-4-sulfonyloxy (—O—SO2—C6H4—CH3) and methylsulfonyloxy (—O—SO2—CH3), and
• durene units obtained from a second monomer of the general formula (II)
• wherein
• Z2 is selected from the group consisting of fluoro, chloro, bromo, iodo, hydroxyl, toluene-4-sulfonyloxy (—O—SO2—C6H4—CH3) and methylsulfonyloxy (—O—SO2—CH3),
• Y is selected from the group consisting of
• CH2Z3,
• wherein Z3 is selected from the group consisting of fluoro, chloro, bromo, iodo, hydroxyl, toluene-4-sulfonyloxy (—O—SO2—C6H4—CH3) and methylsulfonyloxy (—O—SO2—CH3);
• a linear or branched C1-C30 alkyl, a linear or branched C2-C30 alkenyl, a linear or branched C2-C30 alkynyl, sulfo (—SO3H), nitro, amino, hydroxy,
• NHCOR5, —CONHR6, —OCOR7, —COOR8 and —OR9,
• wherein R5, R6, R7, R8 and R9 are selected from the group consisting of a linear or branched C1-C30 alkyl, a linear or branched C2-C30 alkenyl and a linear or branched C2-C30 alkynyl;
• and
• R1, R2, R3 and R4 are independently from each other selected from the group consisting of linear or branched C1-C30 alkyl, a linear or branched C2-C30 alkenyl, a linear or branched C2-C30 alkynyl, sulfo (—SO3H), nitro, amino, hydroxy, oligo(C2 to C4-alkylene glycol), —NHCOR5, —CONHR6, —OCOR7, —COOR8 and —OR9,
• wherein R5, R6, R7, R8 and R9 are selected from the group consisting of a linear or branched C1-C30 alkyl, a linear or branched C2-C30 alkenyl and a linear or branched C2-C30 alkynyl.