Copolymers for near-infrared radiation-sensitive coating compositions for positive-working thermal lithographic printing plates

A copolymer having the general structure:

• wherein:
• a, b, and d are molar ratios varying between about 0.01 and about 0.90 and c is a molar ratio varying between 0 and about 0.90,
• A1 represents monomer units of formula:
• wherein:
• R is hydrogen, methyl or ethyl,
• R1 is absent or represents one to four alkyl substituents;
• the alkyl substituents optionally comprising one or more ether, ester, amine, amide, urea, piperazinyl, sulfonamide, or carbamate functional groups, the alkyl substituents optionally being substituted with one or more cyano,
• U1 is an amide or ester linker,
• V1 is absent or represents alkyl optionally comprising one or more ether, ester, amine, amide, urea, piperazinyl, sulfonamide or carbamate functional group, the alkyl optionally being substituted with one or more cyano, and
• W is —CN or
• A2 represents monomer units of formula:
• wherein:
• R is hydrogen, methyl or ethyl,
• R1 is absent or represents one to four alkyl substituents, the alkyl substituents optionally comprising one or more ether, ester, amine, amide, urea, piperazinyl, sulfonamide, or carbamate functional groups,
• U2 is absent or represents an amide or ester linker,
• V2 is absent or represents alkyl optionally comprising one or more ether, ester, amine, amide, urea, piperazinyl, sulfonamide or carbamate functional group, and
• Y is
• wherein R2 each time it appears is independently hydrogen or alkyl optionally comprising one or more ether, ester, amine, amide, urea, piperazinyl, sulfonamide, or carbamate functional group;
• A3 represents monomer units of formula:
• wherein
• R is hydrogen, methyl or ethyl,
• U3 is absent or is an amide or ester linker, and
• Z is alkyl or aryl, the alkyl being optionally substituted with one or more hydroxy, alkyloxy or halide and the aryl being optionally substituted with one or more alkyls that are optionally substituted with one or more hydroxy, alkyloxy or halide;
• and
• A4 represents monomer units of formula:
• wherein R is hydrogen, methyl or ethyl,
• R1 is absent or represents one to four alkyl substituents;
• the alkyl substituents optionally comprising one or more ether, ester, amine, amide, urea, piperazinyl, sulfonamide, or carbamate functional groups,
• U4 is absent or represents an amide or ester linker,
• V4 is absent or represents alkyl optionally comprising one or more ether, ester, amine, amide, urea, piperazinyl, sulfonamide or carbamate functional group, and
• A is —COOH, —PO(OH)2,