NMR Study of Hyperbranched Polyphenylenes from the AB2, (AB2 + AB) and (A2 + B3) Methods

Abstract

AbstractSummary: The 1H NMR and 13C NMR spectra of hyperbranched polyphenylenes synthesised from AB2, (AB2 + AB) and (A2 + B3) 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 1H and 13C 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 (A2 + B3) 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 1H NMR time scale. This can be proved both by EXSY and variable‐temperature experiments. Steric constraints were also deduced for the AB2 polyphenylenes from signal line shape.Selected spectra from a VT 1H NMR experiment on polymer 7b (solvent: C2D2Cl4; *–13C satellites of the solvent; signal at 7.3 ppm due to traces of CHCl3).magnified imageSelected spectra from a VT 1H NMR experiment on polymer 7b (solvent: C2D2Cl4; *–13C satellites of the solvent; signal at 7.3 ppm due to traces of CHCl3).