The dependence of intrinsic viscosity [eta] on temperature for fractions of poly(maleic anhydride-co-mono-n-octylitaconate) [p(MA-co-MOI)] was studied. A discontinuity in [eta] as function of temperature similar to that of poly(mono-n-octylitaconate) (PMOI) is found which has been attributed to a conformational transition of the polymer chain. This conformational transition can be removed by the addition of poly(dimethylsiloxane) (PDMS). The effect is interpreted in terms of interpolymer complexation.