Stable polymer/inorganic composite multilayers using covalent cross-linking assisted by a magnetic field

Abstract

In this study, stable composite multilayers incorporating magnetic montmorillonite (MMT) and weak polyelectrolyte were prepared under the assistance of a magnetic field. We reported a facile method for fabrication of covalently cross-linked Layer-by-Layer (LbL) multilayers using a photosensitive cross-linking agent 4,4′-diazostilbene-2,2′-disulfonic acid disodium salt that carried double azido groups. The multilayers after cross-linking presented improved stability against extreme solution conditions (basic solution pH = 14), and over 78.15% of magnetic MMT remained on the substrate, in clear contrast with the non-cross-linked multilayers, for which less than 8% of the magnetic MMT remained. The results of UV–Vis spectroscopy and scanning electron microscopy (SEM) measurements supported the improvement in the stability of the multilayers. Moreover, the assistance of the external magnetic field improved the LbL assembly efficiency and the cross-linking step achieved the molecular retarded release. When gauze was used as the substrate, the mass loading under the magnetic field was approximately 0.976 mg/cm2, which was 4.2 times the amount deposited on gauze without an external magnetic field. After interfacial modification of gauze using LbL multilayers, the static contact angle transformed from hydrophobic (111.25°) to perfect hydrophilic. When we employed aspirin as the target drug, it took 23 h for the cross-linked multilayers to achieve saturated release, as opposed to 9 h for the non-cross-linked multilayers.