Layer-By-Layer Self-Assembly Multilayers Under High Gravity Field

In this paper, we used high gravity layer-by-layer self-assembly method (higee-LBL) for rapid construction of multilayer membrane. Respectively from surface morphology and compactness, we examined the quality of the multilayer membrane prepared on planner substrates, studied the film building regularity of the three kinds of system, which are PDDA/Au NPs, PDDA/PAzo, PEI1800/Por. Higee-LBL was used on non-planar substrate for the first time. In addition, we also studied the self-assembly behavior of small molecules under high gravity through the PEI/Por system, to explore the premise conditions of LBL.In PDDA/Au NPs system, we determinated the adsorption rates of Au NPs and the multilayer membrane assembly process, characterized the surface morphology of the multilayer membrane on silicon wafer and nickel foam. The results shows that the adsorption equilibrium time of Au NPs by dipping is about 16 min, while it is 9 min,5 min,2 min,1 min by higee corresponding to the rotating frequencies of 20 Hz,30 Hz,40 Hz,50 Hz. So the rapid construction of multilayer membrane can be realized by higee, the surface roughness of the multilayer film (PDDA/Au NPs) 5 by dipping is about 14.3 nm, which is reduced to only about 10.3 nm by higee, SEM figures also showed that the multilayer membrane surface is more smooth by higee. Higee-LBL was achieved on a non-planar substrate, while the multilayer film quality was not affected.In PDDA/PAzo system, we determined the adsorption rates, the self-assembly process and the surface morphology of the multilayer membranes, studied electrochemical properties and optical properties of the multilayer membrane. The results showed that the adsorption equilibrium time of PAzo by dipping is about 10 min, while it is 4 min,2 min,1 min by higee corresponding to the rotating frequencies of 30 Hz,40 Hz,50 Hz. So the rapid construction of multilayer membranes can be realized by higee. The surface roughness of the multilayer film (PDDA/PAzo) 5 by dipping is about 2.0 nm, which is only about 1.0 nm by higee. We can obtain more smooth multilayer membrane by higee. The smaller the concentration of PAzo solution is, the greater the size of the chain is, PAzo can flat out on the basement membrane, which makes the surface roughness of membrane smaller. Compared to dipping, the self-assembly multilayer prepared by higee had a smaller CV curve peak area and a lower peak current. Under ultraviolet light the balance time of cis-trans isomerization for PAzo also increased from 70 s to 120 s, grew by 70%, showed that the compactness of multilayer film prepared by higee is better.In PEI1800/Por system, we also determined the adsorption rates and the desorption rates of Por by dipping and higee (the rotating frequency is 40 Hz), multilayer membrane assembly process and the influence on the multilayer film surface morphology. The results showed that the adsorption and desorption equilibrium time are 2.5 min and 50 min by dipping, it is respectively 40 s and 100 s by higee, the adsorption and desorption phenomenon is more obvious. The assembly process with pumping into the solution for 30 s can be realized, when extending the time to 100s, it was impossible for assembly, which stated that the switching characteristics of basement membrane surface charge is the basic condition of self-assembly. Because of the obviously desorption phenomenon of Por, we can achieve effective control of multilayer membrane structural quality by properly selecting the time of the assembly process.