Dichroism of stretched poly vinyl alcohol (PVA) foils containing pyridazinium ylids II

Pyridazinium ylids are zwitterionic compounds with a visible band resulting from an intramolecular charge transfer from the carbanion towards the heterocycle. The degree of order of ylid molecules in polymer matrices can be estimated by the dichroism of thin films. The visible band intensity measured on two perpendicular directions (one parallel and other perpendicular on the film stretching direction) determines the dichroic ratio, a parameter proportional to the relative number of the oriented ylid molecules along the stretching direction. From the spectral study it results that about 53% of ylid molecules are oriented when the degree of stretching is about 4. This kind of studies contributes to establish the mechanism of the orientation of the lateral polymer chains and also can offer information about the direction of the intramolecular electronic transfer responsible for the visible absorption band appearance.