الفهرس 
chapter 1Only 14 pages are availabe for public view
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Abstract
Poly (methyl methacrylate) nanoparticles are of extended use in different research areas and applications from industrial application to drug delivery vehicles. Polymethyl methacrylate (PMMA) nanoparticles have been successfully prepared by microwave-free/emulsifier-free emulsion polymerization with potassium persulphate (KPS) as initiator. After confirming the composition using FT-IR, particle characterization by Transmission Electron Microscopy (TEM) revealed the morphology of uniformly sized fine-tuned nanoparticles can be obtained at less than 50 nm particle size.
In chapter 1 we showed a comprehensive introduction and literature survey, importance and applications of PMMA nanoparticles. Methacrylate synthesis, processing and reaction mechanisms have been illustrated. Then, we discussed the reactor design fundamentals, general approach for reactor design and general mass balance concepts.
In chapter 2 we explained the reaction proposed apparatus that have been used to prepare the PMMA nanoparticles as well as all the material and experimental steps involved. The PMMA nanoparticles were synthesized through SFEP with a monomer feeding system, in which the monomer was fed as gas phase. The manner and the rate of feeding MMA monomer were very important in controlling the particle size. The gas phase monomer could diffuse very fast and uniformly into the nucleated particles in wide range of reaction medium compared with the liquid phase monomer. Therefore, smaller and uniform nanoparticles could be obtained by the gas phase monomer feeding.
In chapter 3 the emulsifier-free emulsion polymerization of (MMA) was carried out at different temperatures using potassium persulphate (KPS) as initiator. In 40% V/V water-acetone mixture, the conversion-time curves for the polymerization are reported for different monomer concentrations, initiator concentration, and temperatures.
The rate of polymerization was found to be 0.89 powers dependent on the monomer concentration .This order may be attributed to the greater rate of participation of the monomer in the initiation step. The effects of the Rp and the conversion have been studied by varying the concentration of the initiator in the range 8.0X10-3 to 20.0X10-3 mol/L; it is observed that with the increase in KPS concentration in that range, the conversion and Rp were found to increase. The rate of polymerization was found to be 0.38 powers dependent on the in initiator concentration. In conclusion, the rate of polymerization, Rp at 70˚C was expressed by the equation, Rp=K [KPS] 0.38 [MMA] 0.89.
The Arrhenius plot of log Rp vs. 1/T was found to be linear with a negative slope and the activation energy was computed to be 43.5 kJ/mol, which is low as compared to the standard value 47 kJ/mol reported for peroxo compounds. The activation energy for initiator decomposition Ed was found to be 45 kJ/mol which is much lower than the standard value of 56.6 kJ/mol and 137 kJ/mol for t-butyl perbenzoate.
In addition; effects of different monomer concentrations, initiator concentrations, and temperatures on the particles size of obtained polymer have been investigated using TEM. Error! Reference source not found.The TEM data reveal that the particle size of the PMMA emulsion latex is less than 50 nm can be controlled by monomer concentration change. This proves that polymerization can be utilized to prepare such a particle size without using neither surfactant nor microwave irradiation. The gas phase monomer added in the early stage could greatly enhance the probability of homogenous nucleation which was crucial for the formation of particles with smaller size and narrower size distribution. Up to certain initiator concentration (8mM) the particle size are kept under the 100 nm size range. It is found that he particle size gets larger with increasing amounts of initiator molecule and this tendency has been reported for SFEP systems. By varying the reaction temperatures from 50 to 70 ◦C; the particle size stayed almost constant.
Based on the kinetic data obtained from our experiments, initiator and monomer profiles with respect to time will be deduced as well as the material balances for different components are established. Accordingly, a simplified preliminary model for PMMA nanoparticles reactor that utilized SFEP have been proposed. Also, the reactor structure and component are described.