Synthesis of novel polymeric colorants

There are several structural types of polymeric dyes (polydyes) that have been synthesised as colorants for thermoplastic materials, particularly polyesters. This paper reviews three synthetic methods used to prepare polydyes. In method 1, anthraquinone polysulphonamide polydyes were prepared by reacting anthraquinonedisulphonyl chlorides with diamines in the presence of a base. Polymethine polydyes were prepared in method 2 by reacting bis-aldehydes containing two linked aromatic aldehyde moieties with a bis-(active methylene) component under Knoevenagel reaction conditions. In the final method, a variety of polymer types were synthesised by reacting acidic dyes containing two acidic groups with glycol sulphonates in the presence of a base. Most of the polydyes were evaluated as colorants for polyesters, by melt blending and extruding, followed by the preparation of films for further testing of properties such as fastness to light. The primary emphasis of this paper is to discuss the synthetic methods involved and to present the various types of structure that have been investigated.