Core-shell morphology in poly(N-isopropyl acrylamide) copolymer gels induced by restricted diffusion of surfactant

In this paper, we report on the synthesis of copolymer gels of poly(N-isopropyl acrylamide) and poly(acryloyl aminoacids) and their interaction with anionic surfactant, namely, sodium dodecyl sulfate (SDS). While we were studying the swelling behavior of these copolymer gels in SDS solutions, we observed core-shell morphology in the swollen gels along with two discontinuous volume transitions. Such morphologies have potential applications in drug delivery systems. We provide a mechanistic interpretation of these new observations on the basis of electrostatic charge repulsion and restricted diffusion of surfactant into the gel.