Design and demonstration of hybrid multilayer structures: Layer-by-layer mixed covalent and ionic interlayer linking chemistry

We report on the growth of layered molecular assemblies where the interlayer attachment chemistry is controlled layer-by-layer. We demonstrate the compatibility of chemistry where the layers are connected by ionic coordination chemistry [ROPO32--Zr4+--O2CR]+OH- and by the formation of covalent urea moieties. A maleimide-vinyl ether (MVE) copolymer containing pendant benzoic acid and butyl alcohol functionalities is used for ionic layer growth. Coupling of covalently bonded adlayers to the MVE polymer is achieved by the attachment of poly(ethylene imine), PEI, to the MVE surface. Subsequent reaction of the PEI surface with diisocyanates and diamines produces urea-linked covalent multilayers. The covalent multilayers can be converted to ionic growth chemistry by treatment of the aminated terminal surface with POCl3 and water followed by further reaction with MVE polymer and Zr4+ ions. We report the reaction schemes for these hybrid layer structures and the characterization of these novel materials by optical ellipsometry, FTIR and UV-vis spectroscopy, XPS, and X-ray diffraction. The data show the formation of robust multilayer assemblies characterized by limited order within each layer.