Production of hyperbranched polystyrene by high-temperature polymerization

An experimental investigation of the free-radical high-temperature (>300 degreesC) polymerization of styrene/divinyl benzene in a steady-state continuous-stirred tank reactor is reported. Under these conditions, backbiting followed by beta-scission, which is the dominant chain degradation mechanism, is very aggressive. This allows for utilization of large amounts of cross-linker, thus producing hyperbranched polymers with high cross-link density, without the formation of gel. We have also shown experimentally that the propensity of the system to gel depends on the ratio between the rate of propagation and the rate of backbiting/beta-scission, which can be controlled by the operating conditions, such as reaction temperature, average reactor residence time, and solvent level. Thus, through these parameters, it is possible to control the polymer molecular weight and cross-link density, as well as the occurrence of gelation. Therefore, high-temperature polymerization in a continuous-stirred tank reactor provides an economic and reliable technique for producing polymers of hyperbranched nature that can find various unique applications in polymer technology.