Synthesis and characterization of stereoregular π-conjugated polyarylenynes, (-Ar-(E)-CH=CHC≡C-)n, decorated with branched bis-alkoxy side chains

Novel poly(p-phenyleneethynylenevinylene)s (PPEV) have been synthesized by step-growth oligomerization of 2,5-diethynyl-1,4-dialkoxybenzene monomers promoted by the ruthenium pre-catalyst [{RuCl(μ-Cl)(η6-p-cymene)}2] in the solvent mixture AcOH/CH2Cl2. The presence of the branched side chains 2-ethylhexyloxy or 3,7-dimethyloctyloxy in the phenylene unit allows for the formation of soluble π-conjugated short polymers, with slightly increased degree of polymerization (Xn = 5 - 10) and red-shifted photophysical properties (λem ≅ 515 nm in CHCl3) with respect to the analogues with linear alkoxy side chains. The aggregation properties of the polymer with 2-ethylhexyloxy groups have been investigated by an osmosis driven procedure, yielding nanospheres of different size depending on the adapted solvent/nonsolvent mixture.