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

NOESY experiments and molecular mechanics calculations have been used to ex amine the solution conformation of the synthetic polymer poly(N-vinylcarbaz ole) (PNVC), The diagonal and cross-peak volumes of theoretical NOESY spect ra 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 vo lumes calculated from the proposed structures allowed an assessment of the validity of the model structures. The data do not support a single conforma tional model, and only conformational averaging between different model str uctures can provide satisfactory agreement between theoretical and experime ntal parameters. On the basis of the conformational preference of the bulky carbazole groups of PNVC in the various stereochemical sequences, some use ful conclusions were derived in relation to the photophysical behavior of t his commercial polymer.