Use of micromixers to control the molecular weight distribution in continuous two-stage nitroxide-mediated copolymerizations

The synthesis of poly(n-butyl acrylate)-block-poly(styrene) copolymers by nitroxide-mediated radical polymerization (NMRP) in two serial continuous microtube reactors have been performed. The influence of the micromixer used to mix the first block with the second monomer, either an interdigital multilamination micromixer or a T-junction, on the control of the polymerization reaction as well as the copolymerization temperature was investigated. Results were compared with those obtained in a macroscale batch reactor. The main advantage of interdigital micromixers is their ability to achieve an efficient and intimate mixing between a viscous (first block) and a liquid (comonomer) fluid due to the small film thicknesses of the lamellae. In all experiments, the microtube reactors coupled with a multilamination micromixer give the narrowest molecular weight distributions, which implies that the control of the copolymerization reaction is improved.