A highly stereocontrolled synthesis of five kinds of cis-poly[(arylenevinylene)-alt-(2,5-dioctyloxy-1,4-phenylenevinylene)]s has been accomplished by Suzuki-Miyaura-type polycondensation [arylene = p-phenylene (3af), m-phenylene (3bf), 4,4'-biphenylene (3cf), 2,7-fluorenylene (3df), 9,9-dihexyl-2,7-fluorenylene (3ef)]. Reactions of (Z,Z)-bis(2-bromoethenyl)arenes (1a-e) with 2,5-dioctyloxybenzene-1,4-diboronic acid (2fx) in toluene in the presence of Pd(PPh3)4 catalyst, aqueous KOH base, and Bu4NBr as a phase-transfer catalyst at 80 C for 24 h form 3af-ef with number-average molecular weight (Mn) of 5700-9500 in 77-99% yields. The stereoregularity of vinylene linkages in the polymer backbone has been found at least 95%. The starting monomers (1a-e) were prepared in almost geometrically pure forms (99% cis), either by ruthenium-catalyzed hydrosilylation of diethynylarenes followed by bromodesilylation of the resulting bis(2-bromoethenyl)arenes or by addition of bromine to arenediacrylic acids followed by debrominative decarboxylation promoted by Et3N. MALDI-TOF-MS analysis of cis-3af has revealed the presence of two types of polymers having different end groups. Type I polymer bears (Z)-4-(2-bromoethenyl)phenyl and 2,5-dioctyloxyphenyl group at each end, whereas type II polymer has 2,5-dioctyloxyphenyl groups at both ends. Type I polymer is successfully converted to type II polymer by palladium-catalyzed reaction with 2,5-dioctyloxybenzeneboronic acid to obtain cis-poly[(p-phenylenevinylene)-alt-(2,5-dioctyloxy-1,4-phenylenevinylene)] in a single form.
Macromolecules, 39 (6), 2039 -2048, 2006. 10.1021/ma052183l
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