Cross-linked polymers based on 2,3,5,6-tetra-substituted pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP): synthesis, optical and electronic properties

A series of 2,3,5,6-tetra-substituted pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) derivatives carrying thienyl-, 3,4-ethylenedioxy-thienyl- (EDOT-) and 3,4-ethylenedithiathienyl- (EDTT-) substituent groups have been synthesized and electrochemically polymerized. The polymers were investigated using UV/vis absorption spectroscopy and cyclic voltammetry. It was found that the growth of the polymers proceeded as random coupling of the thiophene groups in the 2-,3-,5-, and 6-positions of the DPP chromophore. In the cross-linked polymers, conjugated sequences were only built through coupling of thiophene groups in 3,6-positions, and separated by non-conjugated sequences through coupling with thiophene units in other positions of the DPP core.