The rigid rod polymers poly(p-phenylenebenzobisthiazole) and poly(benzobisthiazole-p-phenylenebisvinylene) have been prepared as thin film samples by spin coating Lewis acid complexes from solution and regenerating the uncomplexed polymer by washing with water and drying in vacuo. This approach allows fabrication of films that show well resolved vibronic structure in their linear absorption spectra In this paper we present results of linear- and electro-absorption spectra From the latter we are able to deduce the average exciton radius which we find to be 13 Angstrom in PBZT and 15 Angstrom in PBTPV. The average change in polarisability accompanying the lowest energy pi-pi* optical transition is also determined. Comparison of our results is made with previous studies.