Synthesis and characterization of thermoplastic copolyesters containing copolymerized azoic dyes

Poly(ethylene terephthalate) and a series of other amorphous copolyesters based on ethylene glycol and terephthalic/isophthalic or 2,6-naphthalenedicarboxylic/isophthalic acid mixtures were prepared by melt polycondensation. Comonomers consisting of azoic dyes having two polymerizable functions on the aromatic rings (either one alcoholic and one carbomethoxyl, two alcoholic or two carbomethoxyl groups) were also added, in amounts lower than 1% mol with respect to the sum of diesters used as starting monomers. In these conditions (P<0.1 torr and T=280°C), only few azoic dyes were found to be stable.

Among the prepared polymers, those based on dyes having sufficient thermal stability were characterized by differential scanning calorimetry and solution properties. Inherent viscosities suggest that molecular weights are high. Glass transition and melting temperatures as well as mechanical properties of colored polyesters are not affected by the presence of the azoic comonomers. UV–visible spectra of copolyester solutions were registered, and absorption coefficients were correlated with the amount of dye.