Thesis (D.Eng.)--Chulalongkorn University, 2005

Copolymerizations of ethylene/a-olefin were investigated with homogeneous Ti-based catalysts. In the first part slurry phase of polymerizations by using various cocatalyst such as, borane (B(C[subscript 6]F[subscript 5])[subscript 3]), borate (Ph[subscript 3]CB(C[subscript 6]F[subscript 5]) [subscript 4]), methylaluminoxane (MAO), dried-methylaluminoxane (d-MAO), modified-methylaluminoxane (MMAO) and dried-modified-methylaluminoxane (d-MMAO) were conducted with [t-BuNSiMe[subscript 2]Flu]TiMe[subscript 2] catalyst. Polymerization was conducted in the atmospheric pressure of ethylene by using a glass reactor. It revealed that the types of activators had influence on the polymerization behavior and polymer microstructure, for example borate system gave the highest insertion of 1-hexene.Moreover, the effect of solvent medium was chosen to study. Four solvents were selected: heptane, toluene, chlorobenzene, dichloromethane. To investigate the effect of solvent, polymerization proceeded in a high pressure autoclave system, and it was revealed that the solvent with high polarity showed high activity and the optimum value of dielectric constant was found to be used of toluene. The different kind of co-monomers for linear low density polyethylene (LLDPE) were also investigated in this polymerization system and found that 1-octene exhibited the best co-monomer to produce LLDPE. Moreover, we have modified the catalyst structure form [t-BuNSiMe[subscript 2]Flu]TiMe[subscript 2] to [t-BuNSiMe[subscript 2]Cp*]TiMe[subscript 2] to investigate the effect of catalyst structure ,and found that LLDPE produced from the former system had a better ability for the insertion of alpha olefins. All the polymers obtained were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) to observe the polymer properties and polymer microstructure.