Effect of Temperature Variations on Molecular Weight Distributions - Batch, Chain Addition Polymerizations

The Maximum Principle was applied to determine the types of temperature variations that minimize and maximize the breadth of the molecular weight distribution (MWD) for chain addition polymerizations in batch reactors. It was found that the variations which minimize the breadth of the MWD keep the instantaneous number average chain length constant. The variations which maximize the breadth of the MWD are step changes in temperature resulting in bimodal distributions. Numerical and experimental examples of such variations are presented. MWDs with minimum and maximum breadths are compared to those that might be formed by temperature variations in real reactors. Under most conditions, temperature variations appear to have a much greater effect on MWD than residence time distributions and micromixing.