Exfoliation and liquid crystal phase formation of layered double hydroxide into waterborne polyurethane coatings

Abstract

Waterborne polymer coatings based on polymer composites were prepared by using layered double hydroxides (LDH) as reinforcing inorganic particles. Starting with a model system we demonstrated the impact of the nature of the charge balancing anions of the LDH phase on the kinetics of the polymer intercalation and the film building as well as on the degree of particle dispersion. A broader scope of coating morphologies, covering particle arrangement and heterogeneities on extended length scales resulted from specific polymer–LDH particle interactions. From a combination of characterization techniques using small angle X-ray scattering, transmission electron microscopy and confocal laser scanning microscopy and by using a mixture of compatible polymers it was found that textured coatings were obtained via a liquid crystal phase of polymer stabilized LDH platelets whereas the LDH particles impact on the phase separation of incompatible polymers resulted in disperse, bicontinuous or self-stratified coatings. This novel innovative approach was found to be promising for coatings domains where a high impact resistance is needed.