SYNTHESIS OF NOVEL POLY[(2,5-DIMETHOXY-P-PHENYLENE)VINYLENE] PRECURSORS HAVING 2 ELIMINATABLE GROUPS - AN APPROACH FOR THE CONTROL OF CONJUGATION LENGTH

Poly[(2,5-dimethoxy-p-phenylene)vinylene] (DMPPV) of varying conjugati on length was synthesized by selective elimination of organic soluble precursor polymers that contained two eliminatable groups, namely, met hoxy and acetate groups. These precursor copolymers were in turn synth esized by competitive nucleophilic substitution of the sulfonium polye lectrolyte precursor (generated by the standard Wessling route) using methanol and sodium acetate in acetic acid. The composition of the pre cursor copolymer, in terms of the relative amounts of methoxy and acet ate groups, was controlled by varying the composition of the reaction mixture during nucleophilic substitution. Thermal elimination of these precursor copolymers at 250 degrees C, yielded partially conjugated p olymers, whose color varied from light yellow to deep red. FT-IR studi es confirmed that, while essentially all the acetate groups were elimi nated, the methoxy groups were intact and caused the interruption in c onjugation. Preliminary photoluminescence studies of the partially eli minated DMPPV samples showed a gradual shift in the emission maximum f rom 498 to 598 nm with increasing conjugation lengths, suggesting that the color of LED devices fabricated from such polymers can, in princi ple, be fine-tuned.