A comprehensive investigation was undertaken in order to determine the effect of different reaction parameters on the molecular weights of polymers formed in a Suzuki polycondensation. In particular, we studied how the choice of solvent, base, ligand cocatalyst, palladium source, and monomers could affect the molecular weights. For these particular polymerizations, the best solvent and base were found to be CH2Cl2 and aqueous 3 M K3PO4, respectively. More interestingly, we determined that tri(o-tolyl)phosphine far surpassed not only the traditional triphenylphospine ligand cocatalyst, but also the more-recently developed hindered, electron-rich ligands that have yielded impressive results in small-molecule Suzuki coupling reactions. Molecular weights were also found to depend upon the source of palladium, with bis[tri(o-tolyl)phosphine]palladium(0) providing the best overall catalyst system. Finally, contrary to earlier reports, we found no advantage to replacing the more readily accessible bromide monomers with the corresponding iodides, and that pinacol boronic esters were inferior to the more traditional 1,3-propanediol boronic ester monomers. In sum, the work performed here shows that under optimized conditions, molecular weights on the order of 105 g/mol can be readily achieved with a Suzuki polycondensation.

Polymers containing conjugated oligo(phenylene) segments of defined length alternating with solubilizing regions of di-to hexa(ethylene glycol) have been synthesized using a Suzuki coupling protocol. Soluble and characterizable materials with up to four benzene rings linked together have been formed without the inclusion of conjugation-disrupting solubilizing side chains. The polymers were generated with weight-averaged molecular weights as high as 158 000 g/mol as determined by GPC-LS. The thermal and luminescence properties of these materials were studied in order to determine how these properties varied with the lengths of the two types of blocks. While the terphenyl polymers were amorphous, the quaterphenyl polymers exhibited multiple transitions in their DSC thermatograms. Polarized light microscopy and X-ray diffractometry were used to investigate this behavior. All of the polymers fluoresced strongly in the blue region of the visible spectrum with a 40 nm red shift in emission between solution and solid-state spectra. UV-visible and fluorescence studies were performed at different concentrations and in solvent/nonsolvent mixtures in order to study possible causes for this spectral shift, which appears to be due to the presence of ground state aggregates.