The effect of intermolecular donor–acceptor energy transfer on emission anisotropy in uniaxially oriented polymer films

Excitation energy transport between donors and acceptors is studied for uniaxially stretched and unstretched poly(vinyl) alcohol films. Donor emission anisotropy courses versus acceptor concentration as well as donor–acceptor emission anisotropy spectra occurred quite different in stretched and unstretched films. Upon donor excitation the total emission anisotropy rapidly decreases when passing from the donor to the acceptor fluorescence band in disordered systems. However, such a pronounced effect has not been found in partly ordered films. Donors and acceptors exhibit highly preferential mutual orientation in strongly ordered films resulting in the preservation of acceptor emission anisotropy.