Electromodulation in Poly(Para-Phenylene)-Type Ladder Polymer

We report studies on the electronic structure of the methyl substituted poly(para-phenylene)-type ladder polymer (m-LPPP) using electromodulation-techniques. Electric fields from 10 kV/cm up to a few hundred kV/cm were applied to the samples either parallel or perpendicular to the incident light. The lineshape of the electroabsorption(EA)-spectra follows very closely the first derivative of the unperturbed absorption-spectra. Comparing EA-measurements with perpendicular and parallel field geometry provides further insight into the nature of ordering of the polymer-chains in films of different thickness.