Thesis (M.Eng.)--Chulalongkorn University, 2013

In this research, branched polycarbonate (branched PC) was synthesized by melt transesterification of bisphenol-A (BPA) and diphenyl carbonate (DPC) in a batch reactor. The effects of initial mole ratio of DPC/BPA and with or without catalyst on molecular weight of the obtained PC were investigated by gel permeation chromatography. It was found that at initial mole ratio of DPC/BPA at 1.26/1.00 without an addition of catalyst was an appropriate for the preparation of branched PC in a controlled manner. The influence of types and amount of branching agents on PC molecular weight profile were also studied. 1,1,1-tris(p-hydroxyphenyl)ethane (THPE), 3,3-bis(p-hydroxyphenyl)oxindole and 1,1,1-tris(hydroxymethyl)ethane were prove to be candidates as branching agents for branched PC synthesis. The condensation reaction of DPC/BPA with 3 mol% of THPE at temperature up to 250 oC and pressure of 100 mmHg provided molecular weight of branched PC product about of 26,294. 3 mol% of THPE was found to be the most appropriate and promising choice of branched PC synthesis as can be confirmed by NMR spectroscopy. The melt viscosity of branched PC with 3 mol% of THPE exhibited a high shear sensitivity to that of commercialized branched PC with relatively low melt flow index suggesting a presence of long chain branching in our branched PC. The thermal and thermomechanical properties of branched PC product were also studied using differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical analysis. The thermal properties of synthesized branched PC i.e. glass transition and degradation temperature were close to that of the commercial branched PC. Furthermore, synthesized branched PC possesses mechanical property similar to those commercial PC products.