Studies in interaction between poly(vinyl pyrrolidone) and azo dyes

Interaction between poly(vinyl pyrrolidone) (PVP) and monoazo dyes containing different numbers of ionic groups situated at different locations in the dye molecule has been examined from the results of spectrophotometric, conductometric, and viscosity measurements. Results indicate the maximum dye binding capacity as well as number of monomer units of PVP combined with the molecule of dye depends on the number of ionic groups present in the dye molecule but not on the location of these groups. The calculated values of free energy change indicate weak bonding between the dyes examined and PVP at different pH's in the range of 4–10.7. Dye binding capacity as well as number of monomers of PVP combined also depend on the molecular weight of PVP. Changes in the configuration of the polymer molecule of PVP take place as a result of dye–polymer interaction.