Conformational analysis of poly(N-vinylcarbazole) by NMR spectroscopy and molecular modeling

NOESY experiments and molecular mechanics calculations have been used to examine the solution conformation of the synthetic polymer poly(N-vinylcarbazole) (PNVC), The diagonal and cross-peak volumes of theoretical NOESY spectra have been calculated for several mixing times by employing the complete relaxation matrix analysis (CORMA) introducing as structural models for the polymer chain conformation the triad stereochemical sequences (isotactic, heterotactic, and syndiotactic). Comparison between measured volumes and volumes calculated from the proposed structures allowed an assessment of the validity of the model structures. The data do not support a single conformational model, and only conformational averaging between different model structures can provide satisfactory agreement between theoretical and experimental parameters. On the basis of the conformational preference of the bulky carbazole groups of PNVC in the various stereochemical sequences, some useful conclusions were derived in relation to the photophysical behavior of this commercial polymer.