Preparation And Properties Of Polymer/Inorganic Sheets Covalent Assembly Materials

Recently, organic-inorganic composites have attracting more interest due to their industrial applications and the exploring of theory, including optics, electrics, organisms, catalysis, membrane materials and mechanics. Among the various kinds of organic-inorganic hybrids, polymer/clay composites have become the most potential for applications because of the very low cost of clay components, relatively simple preparation, their nanometer size that provides unique features and extraordinarily high surface area.As far as we are aware, polymer/clay composites become more widely studied in academic, government and industrial laboratories. Based these studies, many composites with high performance and new functional properties were prepared, including the fire-retardant, barrier materials, optical materials, controlled-release materials, antibacterial agent and medical materials, which exhibited the potential or industrial applications.The study has demonstrated that the toughening of the composites has the formidable increase when the juxtaposition of inorganic and organic matrix was realized to form the orderly nanostructure. Thus, the new procedure and method were developed to form the novel composites and kinds of assemblies with different morphologies were obtained.However, none of the previous techniques reports the possibility for generating polymer-clay assemblies based on chemical bindings by in-situ polymerization, and the structure and properties of the assemblies were confused. Herein, the structure and properties of the composites were explored and the formidable results were showed as follows:(1) The possibility of the modification of VMTsThe exfoliated vermiculites (VMTs) were prepared through the grinding, intercalation and exfoliation of commercial VMTs. Exfoliated VMTs were chemical modified by the silane coupling agent KH-550and KH-560and the relationship between the usage of silane coupling agent and the loading ratios of modified VMTs. The change of the structure of VMTs before and after the chemical modification was studied by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Thermogravimetric Analysis (TGA). The results indicated that two kinds of modified VMTs, including amino-modification and epoxy-modification VMTs, were prepared after the chemical modification of silane coupling agent. When the usage of silane coupling agent was0.75ml, the loading ratio of modified VMTs was1.62%. The loading ratio of modified VMTs was increased with the increasing of the usage of silane coupling agent. The loading ratio of modified VMTs could increase to6.06%when the usage of silane coupling agent was5.00ml.(2) The assembly of modified VMTs and polymer monomers and their assembly mechanismThe hexamethylene adipamide/amino-modified VMTs (HA/AMVMTs) composites was prepared through the in-situ polymerization of hexamethylene adipamide and modified VMTs. The assembly of the modified VMTs and interaction between the modified VMTs and polymers were explored by FTIR, XPS, Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). The results showed that the polymer brush was formed onto the VMTs through the covalent bindings of-NH2and-COOH, resulting in the assembly of modified VMTs in the polymer matrix. The loading ratios and modifying ratios of the VMTs played an important role in their self-assembly:with the increasing of the loading ratios, the fiber-, network-and dendritic-like assemblies were observed; with the increasing of polymer brush, the morphology of the assemblies changed from fiber-like to layered-like. For the high ratios of VMTs, leaf-like and rod-like assemblies were prepared by controlling the quantities of the polar groups on the VMTs.The lactic acid/expoxy-modified VMTs (LA/GMVMTs) composites were prepared through the in-situ polymerization of lactic acid and modified VMTs. The assembly of the modified VMTs in the poly (lactic acid) and assembly mechanism of VMTs were explored by FTIR, XPS and TEM. The results showed that the poly (lactic acid) was also formed onto the modified VMTs, resulting in the assembly of modified VMTs in the polymer matrix, the rod-like assemblies were obtained.(3) The structure and properties of the compositesThe Young’s modulus of the HA/AMVMTs assemblies was characterized through SEM and Atomic Force Microscopy (AFM) and the crystallization behavior and tensile properties of the composites were tested. The results showed that the Young’s modulus of the assemblies was higher than that of their constituents after the assembly of inorganic and organic materials. The crystallization behavior and tensile properties of the composites with assemblies were greatly improved compared with the pure polymer system.The Young’s modulus, cytocompatibility, crystallization behavior and thermal stabilities of the LA/GMVMTs composites were characterized through AFM, Confocal laser scanning microscope (CLSM), Polarizing Optical Microscope (POM) and TGA test, respectively. The results showed that the Young’s modulus of the assemblies was also higher than that of their constituents and cells proliferated and reached confluence on the surface of the assemblies, which indicated that the assemblies exhibited the potentiality of biomaterials applications. Compared with pure polymer system, the crystallization rate of the composites became faster and crystallization size of the composites became smaller, while the decomposition temperature of the composites was greatly improved.(4) The exploring of the assembly of VMTs by Molecular Dynamic simulationsBoth PA66/AMVMTs and HA/AMVMTs corresponding models were simulated and calculated by the use of Materials Studio. The interface structure of two models and influence factors on the assembly process of VMTs were studied. The results showed that the HA/AMVMTs model exhibited a better compatibility and higher stability of organic and inorganic matrix compared with PA66/AMVMTs model. In addition, the height and density of polymer molecules on the VMTs had an important role in the assembly of VMTs. With the brush height and density increasing of polymer molecules, the VMTs models were more easily self-assembled. The theory basis on the design and preparation of novel composites was provided based on these results.