Investigation of poly(arylene vinylene)s, 41 - Synthesis of soluble dialkoxy-substituted poly(phenylene alkenylidene)s by applying the Horner-reaction for condensation polymerization

Soluble poly[2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylene-1,2-ethenylene] ( MEH-PPV) and its alternating copolymer poly[2,5-dimethoxy-1,4-phenylene-1,2 -ethenylene-2-methoxy-5-(2-ethylhexyloxy) -1,4-phenylene-1,2-ethenylene] (M 3EH-PPV) were successfully synthesized by condensation polymerization of su bstituted terephthalaldehydes with substituted xylylene bisphosphonates via the Horner reaction. This polycondensation method was also applied to the synthesis of the analogous poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene -1,3-butadiene-1,4-diyl] (MEH-PPB), which contains a 1,3-butadiene instead of a vinylene unit. The optical data of MEH-PPV and M3EH-PPV (solid film, a bs. lambda(max) 484 nm, em. lambda(max) 583 nm) are consistent with those p reviously reported for MEH-PPV from the dehydrohalogenation route. In compa rison to MEH-PPV, the longer alkenylene sequence of MEH-PPB exhibits a slig ht red shift in its absorption and fluorescence spectra (abs. lambda(max) 5 02 nm, em. lambda(max) 604 nm). All three polyphenylene alkenylidenes (MEH- PPV, M3EH-PPV, and MEH-PPB) are completely soluble in common solvents. They are well-defined conjugated polymers of high molecular weight ((M) over ba r(w) > 20000) and possess all-trans structure. Optical quality solid films are easily prepared from these polymers by solution processing. Blends with phenyl-substituted PPV derivatives can also be prepared in this way. This combination of properties is highly desirable for many light-emitting, nonl inear optical, and photoelectrical applications.