The molecular dynamics of p-phenylene vinylene (PPV) oligomers, synthesised by a condensation reaction and separated by molecular distillation, have been investigated using the electrooptic Kerr effect. The experimental Kerr constants of these materials change sign from positive to negative in going from n = 1 to n = 2 and are not in good agreement with theoretical results. The discrepancies, which increase in magnitude as n increases, can be attributed to solvent-solute interactions, the nonplanar nature of PPV oligomers, or the nonvalidity of the additivity scheme chosen for calculation of theoretical quantities.