Studies in interaction between polyvinyl pyrrolidone and stilbene fluorescent compounds. Part I: Interaction with individual compounds

Interaction between polyvinyl pyrrolidone (PVP) and two stilbene‐type fluorescent compounds has been examined from the results of emission, excitation, and ultraviolet absorbance measurements. Results obtained indicate preferential interaction of the trans form of the fluorescent compound with PVP resulting in complex formation and increase in fluorescence due to such complex formation. However, at higher concentrations of PVP in the aqueous phase the cis form also forms a complex which has no fluorescing characteristics. The calculated values of free energy change indicate weak bonding between both the fluorescent compounds and PVP. Fluorescent compound‐binding capacity as well as the number of monomers of PVP combined remain more or less constant in the range of molecular weights of PVP studied.