Graphene Oxide Induces Miscibility In PVDF/PMMA Blends And The Preparation And Characterization Of Functional Membranes

Polymer blending is one of the important methods to prepare materials with high performance.The additive or even synergistic effect of various components can be achieved through blending.Phase separation is a common phenomenon in polymer blends,and it is possible to prepare polymer blends with desired phase structure and further to improve the performance by controlling the phase separation behavior.Crystalline/amorphous system has received extensive attention for a long time,understanding the mechanism of the interaction between crystallization and phase separation is beneficial to obtain high-performance and multifunctional materials.With the development of nanotechnology,it has become a research hotspot to improve the performance of blend composites by adding nanoparticles into polymer blends.Graphene oxide(GO),as an important derivative of graphene,has attracted wide attention in academia because of its large aspect ratio,lots of oxygen-containing functional groups,high Young's modulus and amphiphilic characteristic.The introduction of GO into crystalline/amorphous compatible blends will induce two phenomenon.On the one hand,GO will selectively adsorb the component with strong affinity and cause concentration fluctuation in system and further change the phase separation behavior of blend composites.On the other hand,GO will induce the nucleation in polymer blends,while its large aspect ratio will limit the movement of molecular chains in blends,and then hinder the growth of crystals.So the introduction of GO into polymer blends will have a great influence on the crystallization and phase behavior of blends.Understanding the mechanism and applying it to guide the preparation of high-performance blend composite is of great significance.This thesis aims to investigate the effects of GO on the crystallization and phase separation behavior of Poly(vinylidene fluoride)/Poly(methyl methacrylate)(PVDF/PMMA)melt-compatible system.Firstly,the effects of GO on the heat-induced phase separation behavior of the polymer blends were studied by dynamic rheology method.Secondly,the effects of GO on the crystallization behavior and the crystallization-induced phase separation were studied by dielectric relaxation spectrum.Finally,the porous PVDF/PMMA/GO membrane was prepared according to the influence of PMMA on the crystallization behavior of the blend.Furthermore,the application of this functional membrane in the field of sewage treatment was explored.Based on these researches,the main results are listed as follows:1.PVDF/PMMA/GO ternary nanocomposites were prepared by solution method.The results of interfacial tension between GO and the components in the matrix show that GO exhibits more affinity with PMMA.The results show that GO selectively adsorb PMMA molecular chains.The phase separation temperature of the composites were measured by Han plots,VGP curves and dynamic temperature scanning.The results show that the phase separation temperature of the composites is increased by 3 ~? with the increase of GO content.The results of dynamic time scanning show that GO delays the phase separation process of the composites by about 30 minutes.2.The relaxation of the molecular chains in amorphous region of PVDF/PMMA/GO composites was studied by dielectric relaxation spectrum.The effects of GO on the non-isothermal crystallization and crystallization-induced phase separation behavior of the blends were investigated by non-isothermal dielectric relaxation spectra and non-isothermal DSC.The results show that the introduction of GO slows down the crystallization rate of the composites and reduces the crystallization-induced phase separation temperature by 5~10~?.Through analyzing the results of isothermal dielectric and DSC,it can be found that GO restricts the movement of molecular chains and thus hinders the growth of PVDF crystals.3.The multilayer membrane based on pure PVDF or PVDF/PMMA blend as the substrate and GO as the upper layer was prepared by spin-coating.The effects of PMMA on the micro-morphology of the composite membrane was studied by SEM.The results show that the introduction of PMMA increases the space between the spherulites in the composite membrane and provides more channels for the contact between the MB molecules and GO.Adsorption results show that the adsorption capacity of the composite film is gradually increased with the increase of GO content,and the maximum adsorption amount is 71 mg/g.