Radiation sensitive material suitable for the production of radiation sensitive plates for lithographic printing plate manufacture is based on a polymer including a plurality of structural units represented by the formula:
in which, R represents H or CH₃; each R₁, which may be the same or different represents H or alkyl; R₂ represents a single bond or a substituted or unsubsti­tuted divalent radical; Ar represents a substituted or unsubstituted divalent radical derived from an aromatic or heteroaromatic compound; X represents O, S or NH; A represents an anion; Y represents a carbonyl oxy or aromatic radical; and n is an integer equal to or greater than 1.