Studies on adsorption of poly(vinyl butyral) and dispersibility of γ-fe2o3 in magnetic paints

The adsorption of poly(vinyl butyral) (PVB) at the γ-Fe₂O₃–benzene interface and the air–water interface was investigated by means of the adsorbance on γ-Fe₂O₃ and surface pressure (π)–area (A) curves. The adsorption isotherms of PVB on γ-Fe₂O₃ from the various solvents are of the Langmuir type and can be explained by competitive adsorption between PVB and the solvents. From the π–A curves of monolayers and the adsorbance on γ-Fe₂O₃, it was confirmed that the adsorbed PVB on γ-Fe₂O₃ is in a train-loop conformation with the hydroxyl groups and the butyral segments directed toward the solution phase. The packing density of γ-Fe₂O₃, particles in the magnetic coatings preferentially depends on the conformation of polymers on the particle surface. The PVB–solvent system which gives the most compact train-loop conformation gives the highest dispersion and packing of γ-Fe₂O₃ in the magnetic coatings.