New Strategy to Improve Acrylic/Casein Compatibilization in Waterborne Hybrid Nanoparticles

Abstract

The grafting of casein to acrylic polymers is needed to fully exploit the possibilities of hybrid nanoparticles containing such materials. The explored alternative up to now, based on the primary radical formation onto the protein chains through the redox initiation between the casein amino groups and a hydroperoxide, produces a limited degree of compatibilization to guarantee the synergic effect between both components. A novel strategy that overcomes these limitations is presented. The strategy is based on the use of a crosslinkable casein, which in addition to the characteristic grafting capacity by redox initiation with hydroperoxides, contains acrylic groups able to radically polymerize. The degree of grafting of both acrylic and casein is significantly increased by functionalizing casein with varied amounts of pendant propagating points per protein. Moreover, it is observed that the improved degree of compatibility obtained when using the crosslinkable casein considerably enhanced the properties of the acrylic/casein films, such as their mechanical behavior and resistance to both water and organic solvent.