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 polyamide. 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.