Surface Modification Of CaCO₃ Nanoparticles And Synthesis Of PMMA Composite Microspheres

As an important aspect of nano-science, nano-materials are becoming the focus of material science. With the development of nanotechnology, nano-materials attract more and more interests in both fundamental research and industrial applications. It is a new challenge in nanotechnology that the synthesis of a unique composite material which has the properties in both organic and inorganic components. In the past years, many kinds of composites have been considered as innovative advanced materials, and promising applications have been expected in many fields, including optics, electronics, ionics, mechanics, membranes, protective coatings, catalysis, sensors, biology, and others. Many functional nano-materials can be prepared by selective design and project ideas by the different methods.In this dissertation, we modified the inorganic nanoparticles with different modifying agents and the diversiform functional inorganic/organic composite microsheres were synthesized in the soapless emulsion polymerization process. The property of the composite microsheres can be charactered by apparatus.In order to improve the compatibility between interface of the inorganic nanoparticles and PMMA matrix, we studied the surface property and the disperse state of CaCO3 nanoparticles after these nanoparticles were modified by oleic acid (OA), sodium stearate (SS) and Methl Methacrylate (MMA).SS and OA could interact with CaCO3 nanoparticles, which changed the surface property of the nano-CaCO3 particles from hydrophilic to hydrophobic. At the same time, an unsaturated C=C chemical bond could be introduced to the CaCO3 nanoparticles after the modification with OA. While the PMMA as a modifying agent only improved the compatibility between the CaCO3 particles and polymer matrix. The morphology, component, crystal, size distribution and the surface property of the modified CaCO3 nanoparticles were indicated with the results of TEM, .FT-IR, XRD, PCS, contact angle. The dispersing state of CaCO3 nanoparticles could be improved but the diameter of CaCO3 nanoparticles did not change after the surface modification. Furthermore, the modified CaCO3 nanoparticles showed a better property on the whiteness and the value of oil absorption, which made it advantageous to be applied as the filler in polymer matrix.The detailed experiment conditions which were verified in the process of CaCO3 nanoparticles were modified with OA, such as the amount of surfactant, reactive temperature and stirring speed. In conclusion, the optimal conditions were 2wt% modifying agents to CaCO3 latex, 60°C and 300 rpm stirring rate. The possible mechanism for the formation of the hydrophobic CaCO3 nanoparticles could be proposed as follows: The electronic interaction between the positive charges and negative charges on the surface of CaCO3 nanoparticles made the organic chain of OA or SS array regularly. Modifying agents reacted with the active sites Ca, which made modifying agents grafted on the surface of CaCO3 after the process of modification. And hydrophilic CaCO3 nanoparticles modified by MMA can be explained that organic polymer grafted on the surface of CaCO3 nanoparticles. Both hydrophilic CaCO3 and hydrophobic CaCO3 improved the disperse state in polymer matrix.The strong interface adhesion between the organic matrix and nanofillers is a key for the application of inorganic nanoparticles as fillers. So the modification is a basic process to synthesize the inorganic/organic composites. We obtained CaCO3/PMMA composite microspheres through a soapless emulsion polymerization process. The components of the CaCO3/PMMA composite microspheres were determined through FT-IR and XRD investigations. The presence of CaCO3 nanoparticles in the CaCO3/PMMA composite microspheres was confirmed by XRD analysis. And in the FT-IR spectra of the composites, we found the presence of an ester group that came from PMMA. The results of SEM and PCS showed the change of the polymer microshperes diameter. The morphology of CaCO3/PMMA was not smooth as that of PMMA. In addition, CaCO3 nanoparticles could not be observed in the CaCO3/PMMA composite samples anywhere. The result allowed us to assume that CaCO3 nanoparticles were located in the PMMA polymer microspheres and made the polymer particles become larger.The TEM pictures of the CaCO3/PMMA composite microspheres were obtained from the emulsion system. The CaCO3 nanoparticles were encapsulated or embedded in the PMMA matrix. In addition, the CaCO3 nanoparticles were apt to disperse at the edge of the PMMA polymer spheres.Therefore, a possible mechanism for the formation of the CaCO3/PMMA composite microspheres in a soapless emulsion polymerization process could be proposed as the mechanism of homogeneous nucleation. According to this mechanism model, we can synthesize the different inorganic/organic composites.The results of TGA showed that the encapsulating ratios of inorganic nanoparticles in the composite microspheres could be controlled in this soapless emulsion polymerization process. At the same time, the weight loss of CaCO3 nanoparticles was not obvious till the pH value down to 2. Therefore, it was indicated that the nanoparticles could be protected against decomposition in the subacidity solution because of the encapsulation by the PMMA matrix.The peaks of DTA can be exactly indicated the temperature at the maximal reactive velocity. It was worth mentioning that the temperature of the composite increased by about 84 ?C compared to the pure PMMA, which indicated that the thermal stability of the polymer matrix was improved by the addition of CaCO3.Composite microspheres often exhibit completely different properties from those polymer systems that a micrometer level inorganic component has been added into a polymer matrix. Soapless emulsion polymerization has few or no surfactants, which provided advantages for the synthesis of monodisperse latex.We studied what was the most important factor to improve the amount of nanoparticles in the inorganic/organic composites. The synthesis of poly(methylmethacrylate)-calcium carbonate nanocomposites via the soapless emulsion polymerization was investigated after the CaCO3 nanoparticles were modified with different modifying agents Such three kinds of modifying agents as sodium stearate (SS), oleic acid (OA), and PMMA were used to improve the surface property of CaCO3 nanoparticles. The results of the TGA, FTIR, and the contact angles indicated that the hydrophobic surface of CaCO3 nanoparticles was crucial to improve the compatibility between the CaCO3 and MMA monomer in emulsion system.We have reported that the possible mechanism for the formation of the CaCO3/PMMA composite microspheres in a soapless emulsion polymerization process. Here we want to prepare the functional composites with Cu and ZnO nanoparticles.At first, we worked on the functional property of the different inorganic/organic composites. The copper nanoparticles were pretreated by sodium oleate (SOA) to improve the interfacial adhesion strength between Cu nanoparticles and PMMA. The Cu nanoparticles could be well dispersed in the monomer droplets due to their hydrophobic surface, which contributed to prevent the oxidation of Cu nanoparticles during the polymerization process. The intensity of the emission peak at 365 nm decreased when the loadings of Cu nanoparticles increased in the composites. It was worth pointing out that the friction behavior and fluorescence property of the Cu/PMMA nanocomposites differed from those of the pure PMMA spheres. In this soapless emulsion polymerization process, the Cu nanoparticles were dispersed in PMMA matrix and changed the fluorescent property of PMMA, which could be a potential application in optical plastic. And the composite microshperes with unusual friction behavior in oil will be a potential application in lubricating oil industry.ZnO/PMMA inorganic/organic composite microspheres were synthesized in the yield of 83% via soapless emulaion polymerization. ZnO nanoparticles with hydrophobic property were prepared by oleic acid modification. The existence of ZnO was indicated by the XRD characteristic peaks of the composite microshperes. The TEM images showed that the morphology of the composite microspheres was uniform and ZnO nanoparticles could be well encapsulated in the polymeric microspheres. When the ZnO nanoparticles participated in the polymerization process, the surface morphology of composite microshperes changed from slick to scraggy which was charactered by FESEM. It was worth pointing out that the ZnO/PMMA composites with better fluorescence property could be applied in many fields in the future. So we find an effective method to solve the dispersion state of inorganic nanoparticles in the PMMA matrix.