Layer-by-layer Self-assembly Under High Gravity Field

Layer-by-layer(LbL)self-assembly is a versatile,simple,and economically viable technique to construct multilayer thin films.The LbL self-assembly method can be utilized in constructing multilayer thin films by using various building blocks like polyelectrolytes,carbon nanotubes,nanoparticles,bio-macromolecules and polymer micelles etc.,thereby,exhibit wider applicability towards end applications including sensors,superhydrophobic and biocompatible coating,microporous films,enzymes immobilization,surface pattering,and surface molecular imprinting etc.The widely used conventional LbL self-assembly method is simple but time consuming process,which limits its further applications.Therefore,multilayer fabrication process needs to be optimized by reducing the fabrication time without affecting the morphological changes.High gravity(HG)technique is a well-known technique which is mainly applied in chemical engineering which can intensify the heat and mass transfer strongly.In this thesis,I combined HG with LbL technique to develop LbL self-assembly to enhance the fabrication efficiency while keeping the surface morphology.The first project includes the LbL assembly using poly(diallyldimethyl ammonium chloride)(PDDA)/polystyrene-poly(acrylic acid)(PS-PAA)micelles as positive and negative charge building blocks respectively.I investigated the self-assembly behavior of as-prepared multilayers thin films under both processes.The results indicated that efficiency is enhanced under HG field.Meanwhile,the resulting multilayer films also achieved quality comparable to that constructed under conventional dipping method.Moreover,I also examined the multilayers of PDDA/polymer micelles incorporated with small molecule pyrene prepared under both processes and investigated the release behavior of pyrene from polymer micelles.In addition,LbL self-assembly under HG field with PDDA and graphene oxide(GO)as positive and negative charge building block was also studied.The last project includes the development of facile method to increase the efficiency of surface molecular imprinted layer-by-layer(SMI-LbL)devices in HG field while keeping its selectivity same as in conventional dipping method.As in model system first I construct multilayers of composite of poly(allylamine hydrochloride)(PAH)and meso-tetra(4-carboxyphenyl)-porphine(Por)as the positive building block(PAH-Por)and poly(acrylic acid)(PAA)as a negative building block via conventional LbL methods.Cross-linking agent 4,4’-diazostilbene-2,and 2’-disulfonic acid disodium salt(DAS)was infiltrated in to multilayer films followed by photo cross-linking to develop robust and high fatigue resistance SMI-LbL device.The template molecule extraction from SMI-LbL films and reloading of template molecule into the SMI-LbL films was done under HG field and also with conventional dipping method.I have successfully improved the efficiency of extraction and reloading of template while keeping its selectivity comparable to that found in conventional dipping method.The achieved results showed that HG field has successfully enhanced the efficiency of LbL self-assembly by hastening the diffusion process.Further,the method is helpful in promoting LbL self-assembly for commercial applications and industrial productions.