Capsules Made of Cross-Linked Polymers and Liquid Core: Possible Morphologies and Their Estimation on the Basis of Hansen Solubility Parameters

The model substance 2-methylbenzothiazole with moderate amphiphilic properties, which is used as liquid corrosion inhibitor, was encapsulated via interfacial polymerization with three types of polymers with high cross-link density: polyurethane, polyurea, and plolyamide. The structure of the resulting capsules depends on the type of polymer. Polyurethane and polyurea formed compact particles with 2-methylbenzothiazole homogeneously distributed in the polymer matrix, while in the case of polyamide core-shell structures were formed. Compact morphologies form due to the high affinity of the liquid capsule component to the polymer; core-shell morphology is formed when the affinity is low. Application of the Hansen solubility parameters approach allows prediction and control of the morphology of capsules made of cross-linked polymers.