Self-assembly On The Surface Of Cellulose Materials Based On The Interaction Between Bronic Acid And Polyols

Boronic acid-containing compounds have attracted extensive attention in various research fields since they have been found to be able to form reversible boronate ester with 1,2-diols or 1,3-diols.Especially for the research of composite materials with the phenylboronic acid-containing compounds,which apply the excellent performance of phenylboric acid to contribute new materials excellent properties.The self-assembly technology has the advantages of simple operation,substrate unrestriction,various driving force and so on,hence it has been widely studied in the material modification.In this thesis,the self-assembly on cellulose membrane was investigated by the interaction of boronic acid and polyols.The main contents of the study were as follows:1.Preparation,characterization and analysis of boronic acid modified cellulose membraneThe phenylboronic acid functional groups were grafted onto the surface of the cellulose membrane by 2,2,6,6-tetramethylpiperidine,free radical(TEMPO)oxidation and amidation reaction.The modified cellulose membrane was characterized by infrared spectroscopy and fluorescence method.The mechanical properties of the modified cellulose film were tested by tensile strength tester and burst strength tester.Finally,the adsorption and desorption of microspheres with polyol structure on the surface of cellulose membrane were investigated.The results showed that it is possible to obtain a modified cellulose membrane with better mechanical properties,when the dosage of TEMPO,NaBr and 10 wt % NaCl O were 0.05 g,0.025 g,4 mL and the oxidation time was 45 min.Besides,the cellulose membrane is pH controllable for the adsorption and desorption processes with microspheres containing polyol structure.2.Self-assembly study of boronic acid modified carnauba wax emulsion microspheres on cellulose membraneThe carnauba wax emulsion(CW)with smaller particle size and uniformity was prepared by controlling the concentration of carnauba wax,homogenization rate and homogenization time.After modification with 3-aminobenzeneboronic acid(ABBA),the CW grafted with phenylboronic acid(CW-ABBA)was synthesized.Afterwards,CW-ABBA and polyvinyl alcohol(PVA)were used as the assembly unit and a pair of PVA/CW-ABBA polymer film was assembled on the surface of the cellulosemembrane.The composite membrane with good properties of low surface energy,good film-forming and strong binding to cellulose,effectively improved the moisture resistance,water repellency and mechanical properties of the cellulose membrane.The results showed that the assembly process of PVA and CW-ABBA was pH controllable,and the optimum pH was 10.5.Under this condition,the water vapor permeability of PVA/CW-ABBA decreased 24.2%,water repellent performance increased by 60.2%,tensile index increased by 61.9%,tensile stretch increased by 0.4times.Moreover,the thermal stability of the original cellulose membrane was almost maintained.3.Multilayer assembled film preparation of Chitosan-PBA/PVA and PVAm-PBA/ PVAChitosan-PBA and PVAm-PBA were obtained by amidation reaction via grafting4-carboxyphenylboronic acid(PBA)onto the main chain of chitosan and polyvinylamine(PVAm).Subsequently,PVAm-PBA,Chitosan-PBA and polyvinyl alcohol(PVA)were used as the assembly units to prepare multilayer assembled films of Chitosan-PBA/PVA,PVAm-PBA/PVA on cellulose membrane.Meanwhile,the assembly process of polymer pairs was discussed with silicon wafer and polyethylene microspheres as substrates.The change of the film thickness in the assembly process was characterized by an ellipsometer.The surface charge variation of the microspheres was tested by a Zeta potential analyzer.The uniformity of the polymer film was analyzed by an optical profilometer.The mechanical properties of the modified cellulose membranes were tested by a tensile strength tester.Finally,the adsorption and desorption of microspheres with polyol structure on the surface of cellulose membrane were investigated.The results showed that pH had effect on the interaction between Chitosan-PBA,PVAm-PBA and PVA.Under pH 4.5,the thickness of the polymer film had no change with increased deposition times.In the pH range of 5.5-10.5,the thickness of the polymer film showed a tendency to increase first and then stable with the increase of the pH of the solution.At the same pH,the thickness of the monolayer film of Chitosan-PBA/PVA was higher than that of PVAm-PBA/PVA.The surface electrophoretic changes of the microspheres showed that the surface electrophoretic of the assembly process between Chitosan-PBA,PVAm-PBA and PVA were linear with the increase of assembly times.Meanwhile,the surface electrophoretic variation of Chitosan-PBA/PVA assembly was higher than that of PVAm-PBA/PVA.The optical profilometer test showed that the surface roughness of the silicon wafer with the same polymer assembly pair increased gradually with theincrease of pH value,and the PVAm-PBA/PVA was relatively smooth.The mechanical performance tests showed that Chitosan-PBA/PVA and PVAm-PBA/PVA had a positive effect on the mechanical properties of cellulose membrane.Among them,the enhancement effect of PVAm-PBA/PVA was better than that of ChitosanPBA/PVA and it had the best enhancement effect at pH 9.5.When the surface of the cellulose membrane was assembled with 30 pairs of PVAm-PBA/PVA,the tensile index and tensile stretch of the cellulose membrane were increased by 53% and 76%,respectively.The scanning electron microscopy showed that the modified cellulose membrane was pH controllable for the adsorption and desorption process of polyol-containing microspheres.In addition,thermogravimetric analysis showed that the thermal stability of the PVAm-PBA/PVA modified cellulose membrane was better than that of the Chitosan-PBA/PVA modified cellulose membrane.