Synthesis and characterisation of branched poly(ethylene terephthalate)s
This report details the work carried out on the synthesis and characterisation of branched polyesters. The experimental effort concentrated on the branching of PET-type polymers with a variety of potential branching agents, such as trimesic acid, and the control of branching with end-capping agents, such as benzyl alcohol. The polymers synthesised were then characterised by solution viscosity, end-group analysis, DSC analysis, theological analysis and light scattering. Extensive branching of polymers has been observed and controlled via end-capping agents. One group of polyesters synthesised with increasing levels of brancher, were characterised by absolute Mw values which increased from -10K to -350K. Despite this, all of the macromolecules displayed roughly the same solution viscosity. Though the corresponding melt viscosity increased with Mw, the values achieved were far below those expected for analogous linear polymers of comparable Mw. A second group of polyesters synthesised with a fixed level of brancher and increasing levels of end-capper were characterised by a much narrower range of Mw values. These polymers however had melt viscosities lower than those of linear polymers yet had Mw's of between -3 and - 15 times greater than those of linear polymers.