Molecular design of new π-conjugated poly(ketanil)s with tunable spectroscopic properties

Abstract

New conjugated aryl-substituted poly(azomethine)s, termed poly(ketanil)s, have been synthesised from 1,4-phenylenediamine (or 3,3′,5,5′-tetramethylbenzidine) and two different diketones via polycondensation with the goal to obtain new materials with tunable spectroscopic properties. It is demonstrated that both the absorption and photoluminescence spectra of these poly(ketanil)s can be modified not only by changing the chemical constitution of both repeating subunits in the polymer main chain but also via acid-base doping involving the protonation of the ketimine groups. By combining these two methods it is possible to precisely tune the absorption and emission spectra of the poly(ketanil)s. The use of bifunctional protonating agents, containing plasticising groups, for example 1,2-(di-2-ethylhexyl)ester of 4-sulfophthalic acid (DEHEPSA), in addition to modifying the spectroscopic properties of the polymers, leads to a lowering of their glass transition temperature (T_g), improving in such a manner the flexibility of the prepared poly(ketanil)s materials.