NMR study of hyperbranched polyphenylenes from the AB2, (AB2 + AB) and (A2+ B3) methods

The H-1 NMR and C-13 NMR spectra of hyperbranched polyphenylenes synthesised from AB(2), (AB(2) + AB) and (A(2) + B-3) monomers (A: ethynyl group; B: cyclopentadienonyl group) were analysed with respect to the characteristic substructures of these polymers. The broad and overlapping NMR spectra were studied by a combination of 1D and 2D NMR techniques. Furthermore, appropriate model compounds were synthesised, and their H-1 and C-13 NMR spectra were fully assigned. The signal assignments achieved allow to substantiate the different hyperbranched polyphenylene structures. Steric hindrance in densely packed di- and trihexaarylphenyl substituted units of the (A(2) + B-3) polyphenylenes results in the decrease of the rotation frequency of phenyl rings in these structures to such an extent that the motion is slow on the H-1 NMR time scale. This can be proved both by EXSY and variable-temperature experiments. Steric constraints were also deduced for the AB(2) polyphenylenes from signal line shape.