Synthesis of Some Polymeric Dyes

Polymeric dyes derived from 4‐vinyl phthalic acid and 2,2′‐divinyl benzidine were prepared. Diethyl 4‐vinyl phthalate was synthesized as follows: The Diels‐Alder reaction between 2‐ethyl butadiene and dichloromaleic anhydride led to the formation of 4‐ethyl phthalic anhydride which was esterified, α‐brominated in the side chain by NBS, and dehydro‐brominated by heat. The resulting monomer was polymerized and polydiethyl 4‐vinyl phthalate was reacted with phenol and resorcinol to yield “polyphenolphthalein” and “polyfluorescein” respectively. 2,2′‐Divinyl benzidine was diazotized and coupled with naphthionic acid, anthranilic acid and N,N′‐dimethylaniline respectively, but the resulting vinylic dyes did not polymerize due to steric reasons. However, polymeric dyes were obtained by homopolymerizing, or copolymerizing, 2,2′‐divinyl benzidine with vinyl monomers, diazotizing the corresponding soluble polymers and coupling them with the above reagents. All the polymeric dyes exhibited indicator functions, changing their colour in basic or acidic media.