The Study Of The Fabrication Of Robust Olyelectrolyte Multilayers By Post-Photo-Cross-Linking

Layer-by-layer (LbL) self-assembled technique has been proved to be apowerful method to construct nanothin films with tailored composites andstructures. After decades of development, various functional buildingblocks have been employed to prepare multilayers by using electrostaticinteraction, hydrogen bonding, and/or coordination bonding as drivingforces. However, since the interlayer driving forces involved in LbLassembly are generally weak supramolecular interactions, the stability ofthe assembled films should be improved to cater to some laboratoryapplications under extreme conditions and fit to the durability of thepotential commercial products. In general, two methods have beendeveloped to improve the chemical durability by converting the interlayerforces from weak supramolecular interactions to strong covalent bonds.One is to fabricate multilayers using chemical reactions as driving forces;the other is post-crosslinking of the as-prepared self-assembled films.In this study, we have developed a facile method to stabilize LbLmultilayers of weak polyelectrolytes. Using PAH/PAA and PAH/PSS multilayer films as a model system, we post-infiltrated DAS as aphotosensitive crosslinking agent, and then exposed the films to UVirradiation to initiate inter-and intra-layer photo-cross-linking. Theexperimental data show that the durability of the multilayers is highlyimproved, resulting in films that remain stable even under ultrasonicationin an saturated SDS solution for10min. Moreover, a patterned surfacewas prepared by taking advantage of the different stability of the filmbefore and after UV irradiation. Considering that the azido groups caneasily form chemical bonds with almost any kind of organic surfaceunder UV irradiation, we believe that by proper post-treatment thismethod could be extended to other LbL systems, especially suitable forbiomacromolecules with weak charges. Moreover, this method ispromising for laboratory applications of LbL films used under extremeconditions and could promote its potential commercial applications.