Polarization anisotropy in mesoscale domains of poly(phenylene vinylene) thin films

We investigate the orientational ordering in poly(phenylene vinylene) (PPV) thin films by polarization modulation near-field optical microscopy. PPV films show nonuniform mesoscale anisotropic domains. The average domain size is similar to0.3 mum, and the coefficient fur linear dichroism is similar to1.25 x 10(4) cm(-1). Both quantities are independent of film thickness up to 90 nm. The small linear dichroism as compared with the absorption coefficient indicates that polymers within domain are only partially aligned. The coefficient for linear dichroism is constant implies that there are not several domains with different polymer orientation vertically.