In this thesis, eco-friendly synthesis methods of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) derivatives and synthesis of branched PPOs have been investigated. First, PPO was synthesized by oxidative polymerization of 2,6-dimethylphenol (DMP) in water using a water-soluble complex of copper and novel polymer ligands, poly(itaconic amide acid-co-acrylic acid)s. In the polymerization of DMP, the polymer ligands with various monomer ratios of itaconic amide acid:acrylic acid (4:6 and 2:8) were used, and effects of molecular weight and ratio of the polymer ligands on the polymerization of DMP were studied. The polymerization conditions were optimized varying precursor copper complexes, concentration of hydrogen chloride, molecular weight and monomer ratio of the polymer ligands, surfactant, and temperature, resulting in PPO with the best yield of 93% with number average molecular weight (Mn) of 3700 and molecular weight distribution (Mw/Mn) of 2.12. This yield is higher than that of previously reported conditions using arginine ligand in water (72%). Furthermore, the optimum condition was applied in copolymerization of DMP and 2-allyl-6-methylphenol (AMP) to provide their copolymer in 95% yield (Mn = 3000, Mw/Mn = 2.5). This allyl containing copolymer is expected to have thermally crosslinkable property; therefore its crosslinking reaction was carried out. On the other hand, recovery of the catalytic system of copper-polymer ligand was examined. The catalytic system maintains its activity even after recycling five times.
Second, to obtain PPOs with higher number of crosslinkable groups, DMP was copolymerized with bifunctional bisphenol A (BPA) or trifunctional 1,1,1–tri(4-hydroxyphenol)ethane (THP) in the presence of copper complex to produce a linear poly(2,6-dimethyl-1,4-phenylene oxide-BPA) (PPO-BPA) and a branched polymer poly(2,6-dimethyl-1,4-phenylene oxide-THP) (PPO-THP) using methanol as solvent. Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was also synthesized by similar procedure for comparison. The obtained polymers were characterized by 1H NMR spectroscopy, viscosity measurement, dynamic light scattering analysis, differential scanning calorimetry, and thermogravimetric analysis. These polymers were used for termination reaction using 4-vinyl-benzyl chloride as a functionalized group in order to add double bonds at the polymer ends to form corresponding polymers (PPO-THP-ST, PPO-BPA-ST, and PPO-ST). The vinyl terminal groups are crosslinkable by thermal annealing. We estimated the vinyl-benzyl group ratio of the polymers by peak integral ratio of 1H NMR spectra. PPO-THP-ST contains higher vinyl-benzyl group ratio than that of linear polymers, resulting in higher reactivity in annealing reaction than the linear polymers. PPOs have often been used in application of printed circuit boards (PCBs). Therefore, we measured the dielectrical constant (Dk) and dissipation factor (Df) which are the most important factors in such application. Dk and Df values of the linear and branched polymers were compared.