A polymeric photoinitiator, being a co-polymer of at least one monomer with at least one monomer, wherein: - monomer is a photoinitiator monomer of the formula: wherein: Pi is a photoinitiator moiety; Z is a linker moiety; R 1 is selected from optionally substituted C 1 -C 30 alkyl, optionally substituted C 3 -C 30 alkenyl, optionally substituted C 3 -C 30 alkynyl, optionally substituted C 3 -C 12 cycloalkyl, optionally substituted -[(C 1 -C 6 alkylene)-O-(C 1 -C 6 alkylene)] p -H moiety, optionally substituted heterocyclyl, and optionally substituted aryl; p is an integer from 1-6; X 1 and X 2 are each independently selected from optionally substituted C 1 -C 12 alkylene, optionally substituted C 2 -C 12 alkenylene, -O-, -S-, -NR 4 -, -C(=O)-, -C(=NR 3)-, -Si(R 3) 2 -O-, optionally substituted C 3 -C 8 cycloalkyl, optionally substituted heterocyclyl, optionally substituted aryl, and combinations thereof; X 1 and X 2 or a part thereof may be linked to one another or to linker Z or R 1, to form one or more ring structures; Z, R 1, X 1 and X 2 are selected such that N is a quaternary ammonium; R 3 is H or optionally substituted C 1 -C 12 alkyl; R 4 is optionally substituted C 1 -C 12 alkyl; X - is a counterion, or a negatively charged moiety that is covalently bound to any carbon atom of Pi, Z, R 1, X 1, X 2 or their optional substituents, to form a betaine-type structure; W 1 and W 2 are each independently selected from -OH (forming a secondary alcohol), -CH 2 OH (forming a primary alcohol), -NH 2, -NHR 6, -SH, -Si(OR 6) 2 -H, -SiH(R 6) 2, - C(=O)-OSi(R 6)3, -NCO, -NCS, -COOH, -COOR 6, -COO-aryl, -C(=O)-Cl, -O-C(=O)-Cl, -C -NH 2, -C -NHR 5, -NH-C -OR 5, and -OC -NHR 5; R 5 is H or C 1 -C 6 alkyl; and R 6 is C 1 -C 6 alkyl. - monomer is a photoinitiator monomer of the formula: wherein: Pi is a photoinitiator moiety; Z is a linker moiety; R 1 is selected from optionally substituted C 1 -C 30 alkyl, optionally substituted C 3 -C 30 alkenyl, optionally substituted C 3 -C 30 alkynyl, optionally substituted C 3 -C 12 cycloalkyl, optionally substituted -[(C 1 -C 6 alkylene)-O-(C 1 -C 6 alkylene)] p -H moiety, optionally substituted heterocyclyl, and optionally substituted aryl; p is an integer from 1-6; X 1 and X 2 are each independently selected from optionally substituted C 1 -C 12 alkylene, optionally substituted C 2 -C 12 alkenylene, -O-, -S-, -NR 4 -, -C(=O)-, -C(=NR 3)-, -Si(R 3) 2 -O-, optionally substituted C 3 -C 8 cycloalkyl, optionally substituted heterocyclyl, optionally substituted aryl, and combinations thereof; X 1 and X 2 or a part thereof may be linked to one another or to linker Z or R 1, to form one or more ring structures; Z, R 1, X 1 and X 2 are selected such that N is a quaternary ammonium; R 3 is H or optionally substituted C 1 -C 12 alkyl; R 4 is optionally substituted C 1 -C 12 alkyl; X - is a counterion, or a negatively charged moiety that is covalently bound to any carbon atom of Pi, Z, R 1, X 1, X 2 or their optional substituents, to form a betaine-type structure; W 1 and W 2 are each independently selected from -OH (forming a secondary alcohol), -CH 2 OH (forming a primary alcohol), -NH 2, -NHR 6, -SH, -Si(OR 6) 2 -H, -SiH(R 6) 2, - C(=O)-OSi(R 6)3, -NCO, -NCS, -COOH, -COOR 6, -COO-aryl, -C(=O)-Cl, -O-C(=O)-Cl, -C -NH 2, -C -NHR 5, -NH-C -OR 5, and -OC -NHR 5; R 5 is H or C 1 -C 6 alkyl; and R 6 is C 1 -C 6 alkyl. Pi is a photoinitiator moiety; Z is a linker moiety; R 1 is selected from optionally substituted C 1 -C 30 alkyl, optionally substituted C 3 -C 30 alkenyl, optionally substituted C 3 -C 30 alkynyl, optionally substituted C 3 -C 12 cycloalkyl, optionally substituted -[(C 1 -C 6 alkylene)-O-(C 1 -C 6 alkylene)] p -H moiety, optionally substituted heterocyclyl, and optionally substituted aryl; p is an integer from 1-6; X 1 and X 2 are each independently selected from optionally substituted C 1 -C 12 alkylene, optionally substituted C 2 -C 12 alkenylene, -O-, -S-, -NR 4 -, -C(=O)-, -C(=NR 3)-, -Si(R 3) 2 -O-, optionally substituted C 3 -C 8 cycloalkyl, optionally substituted heterocyclyl, optionally substituted aryl, and combinations thereof; X 1 and X 2 or a part thereof may be linked to one another or to linker Z or R 1, to form one or more ring structures; Z, R 1, X 1 and X 2 are selected such that N is a quaternary ammonium; R 3 is H or optionally substituted C 1 -C 12 alkyl; R 4 is optionally substituted C 1 -C 12 alkyl; X - is a counterion, or a negatively charged moiety that is covalently bound to any carbon atom of Pi, Z, R 1, X 1, X 2 or their optional substituents, to form a betaine-type structure; W 1 and W 2 are each independently selected from -OH (forming a secondary alcohol), -CH 2 OH (forming a primary alcohol), -NH 2, -NHR 6, -SH, -Si(OR 6) 2 -H, -SiH(R 6) 2, - C(=O)-OSi(R 6)3, -NCO, -NCS, -COOH, -COOR 6, -COO-aryl, -C(=O)-Cl, -O-C(=O)-Cl, -C -NH 2, -C -NHR 5, -NH-C -OR 5, and -OC -NHR 5; R 5 is H or C 1 -C 6 alkyl; and R 6 is C 1 -C 6 alkyl.