Layer By Layer Self-assembly Preparation Of Superhydrophobic Wood

Polyelectrolyte/nanoparticles multilayers created by layer-by-layer (LbL) assembly can be deposited on the wood surface, but there is little research on the functionality. In this paper, based on the principle of fabricating superhydrophobic surface, TiO2 nanoparticles, SiO2 nanoparticles and montmorillonite nanoplatelets were successfully grown on the wood surface using an LbL assembly method and the treated wood thus possessed a superhydrophobic surface. The main contributions of this thesis are listed as follows:1、A cationic polymer adsorbed wood surface was prepared by an LbL assembly method, using the Zeta potential measurement, CNS elemental analyzer to analyze PDDA/PEI adsorbed wood surface and discussing the adsorption of polycations to cut wood surfaces is sensitive to both pH and the concentration of NaCl. It provided a theoretical basis for the next inorganic nanoparticles adsorbed wood surface and further research of preparing superhydrophobic wood surface.2、Response Surface Methods (RSM) was used to optimize the LbL assembly of the wood surface, the optimum reaction condition (reaction at PSS and TiO2 with a pH of 6, PDDA with a pH of 10.5 and SiO2 with a pH of 4) could lead to the water contact angle (WCA) of 158°,153° and 161° proving that the model was feasible with little difference between the predicted value.3、These analytical results of the chemical composition about the wood samples before and after treatment having been characterized respectively by Zeta potential measurement, energy dispersive X-ray analysis (EDXA), X-ray photo-electronic spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscope (SEM) showed that a film of TiO2 nanoparticles, SiO2 nanoparticles and montmorillonite nanoplatelets by LbL assembly technique and a thin layer of 1H,1H,2H,2H-perfluoroalkyltriethoxysilane (POTS) reagent have chemically combined on wood surface.4、The contact angle (CA) measurements demonstrated that after assembled with 5 multilayers or more, the wood surface has exhibited excellent superhydrophobic property with the highest WCA reached 162°. The self-assembled layers had important effect on the generation of TiO2 nanoparticles during the LbL assembly process, the amount of TiO2 nanoparticles, SiO2 nanoparticles and montmorillonite nanoplatelets deposited on the wood surface increased with the increase of the multilayers keeping the other experimental parameters unchanged and the more self-assembled layers reached, the larger the WCA retained.5、Thermogravimetric (TG) analysis showed that 9.1% of the original weight remained for the untreated wood sample,12.8%,21% and 29% for the wood samples treated with TiO2 nanoparticles, SiO2 nanoparticles and montmorillonite nanoplatelets,21.2%,25% and 38% for the wood samples subsequent modified with the POTS molecules. The results showed that the hydrophobic wood has good thermal stability.6、Through Cassie equation and the related research of superhydrophobic interface, the formation mechanism of the superhydrophobic wood surface in this study could be explained by the combination of the high surface roughness of TiO2 nanoparticles, SiO2 nanoparticles and montmorillonite nanoplatelets and the low surface free energy film of POTS on wood surface.7、The dimension stability analysis showed that the weight gain rate reduced with the increase of self-assembled layers, the hydrophobic wood had good ASE, the WCAs of the prepared wood surfaces still keep their hydrophobicity for a long time in air and the water. Thus, it can be concluded that the hydrophobic wood had good dimension stability.