Optical properties of poly 2-methoxy-5-hexyloxy phenylenevinylene and related copolymers

We have measured the dielectric function of poly 2-methoxy-5-hexyloxy phenylenevinylene and the alternating copolymers with N-hexylphenothiazine grown on glass using variable angle spectroscopic ellipsometry and Raman spectroscopy at room temperature. Using the parametric optical constant model, we estimated the dielectric function of each polymer and also determined the band gap parameters, such as threshold energy, broadening, and amplitude. We also determined the band gap parameters by performing lineshape curve-fitting on the second derivative of the fit dielectric function using standard critical point model, and compared to those of the parametric optical constant model. We discussed the shift of band gap parameters and phonon wave numbers in terms of the chemical structures. (C) 2004 American Institute of Physics.