Highly exothermic polymerizations often cause broad molecular weight distributions(MWD)in conventional larger vessels,where mixing of highly viscous solutions is insufficient,and hence,inappropriate temperature distribution(sometimes hotspot)and resultant excessive reaction tend to occur.In solution polymerization to overcome the problem,heat generation is small since monomer is diluted by solvent to be less viscous and less reactive.Straight tubular microreactors were already applied to the solution polymerization and showed an improvement in MWD due to efficient heat and mass transfer1.