CHEMICAL ELECTROOPTICS AND LINEAR DICHROISM OF POLYELECTROLYTES AND COLLOIDS

Recently the controversial discussion on the reliability of electroopt ical relaxation data of polyelectrolyte systems has been revived. It c an be shown that chemical-conformational contributions, for instance, to the dichroitic absorbance changes are exactly given by Delta A(CH)= (Delta A(parallel to) +2 .Delta(perpendicular to))/3, where Delta A(pa rallel to) and Delta A(perpendicular to) are the measured at the light polarization modes sigma=0 degrees (parallel to) and sigma=90 degrees (perpendicular to), respectively. Alternatively, Delta A(CH)=Delta A( sigma) where sigma*=54.7 degrees is the magic angle (for small absorb ance changes). If Delta A(sigma) is measured at the various sigma-pola rization modes according to Delta A(sigma)=Delta A(parallel to) cos(2) sigma+Delta A(perpendicular to) sin(2) sigma, the exact value of Delt a A(CH) is readily obtained. On the other hand, the linear dichroism D elta A=Delta A(OR)(parallel to) -Delta A(perpendicular to)=Delta A(par allel to) -Delta A(perpendicular to)+(Delta A(CH)(parallel to)-Delta A (CH)(perpendicular to)) can only be determined as an approximation of the difference Delta A(-)=Delta A(perpendicular to), if Delta A(CH)(pa rallel to) and Delta A(CH)(perpendicular to) are smaller or approximat ely equal.