Layer-by-layer assembly of polymers and anisotropic nanomaterials using spray-based approach
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Layer-by-layer assembly of polymers and anisotropic nanomaterials using spray-based approach Souvik De1,2,a), Anish Patel2, Jodie L. Lutkenhaus2,3 1
Department of Applied Chemistry, Jabalpur Engineering College, Jabalpur, Madhya Pradesh 482011, India Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843, USA 3 Department of Materials Science & Engineering, Texas A&M University, College Station, Texas 77843, USA a) Address all correspondence to this author. e-mail: [email protected] 2
Received: 20 October 2019; accepted: 5 February 2020
Traditional dip-assisted layer-by-layer (LbL) assembly produces robust and conformal coatings, but it is timeconsuming. Alternatively, spray-assisted layer-by-layer (SA-LbL) assembly has gained interest due to rapid processing resulting from the short adsorption time. However, it is challenging to assemble anisotropic nanomaterials using this spray-based approach. This is because the standard approach for fabricating “allpolyelectrolyte” LbL films does not necessarily give rise to satisfactory film growth when one of the adsorbing components is anisotropic. Here, polymers are combined with a model anisotropic nanomaterial via SA-LbL assembly. Specifically, graphene oxide (GO) is investigated, and the effect of anchor layer, colloidal stability, charge distribution along the carbon framework, and concentration of polymer on the growth and the film quality is examined to gain insight into how to achieve pinhole-free, smooth polymer/GO SA-LbL coatings. This approach might be applicable to other anisotropic nanomaterials such as clays or 2D nanomaterials for future development of uniform coatings by spraying.
Introduction After popularization by Decher et al., layer-by-layer (LbL) assembly has been regarded as one of the most promising nanofabrication techniques to produce conformal coatings from various combinations of materials on a wide range of substrates [1, 2, 3]. LbL assembly is based on the alternating adsorption of oppositely charged species onto a substrate through electrostatic interactions; other interactions such as hydrogen bonding, hydrophobic, host–guest, covalent, and stereochemical interactions are well documented [4]. Taking advantage of the environmentally friendly nature of the waterbased processing approach and the precise control over film morphology, a broad range of materials including polyelectrolytes [1], nanoparticles [5, 6, 7, 8], zeolites [9, 10], metal organic frameworks (MOF) [11], metal oxides [12, 13], and DNA [14] have been successfully assembled into LbL films onto substrates ranging from silicon to glass, plastic, and even textiles [11, 15]. The traditional and most robust LbL assembly approach is based on immersion of the substrate or dipping. In the case of
ª Materials Research Society 2020
dip-assisted LbL assembly, the substrate is alternately dipped for minutes into the solutions/dispersions of complementary species. Between the deposition steps, the sample is rinsed to remove the loosely bound s
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