Summary: Nitroxide‐mediated polymerization of styrene in a continuous tubular reactor has been demonstrated for the first time. The polymerization kinetics in the tubular reactor are similar to those in a batch reactor. The number average molecular weight increases linearly with conversion, and chain extension experiments were successful, indicating that the living nature of the polymerization is maintained in the tubular reactor.Evolution of molecular weight as measured by GPC for chain‐extended latex in continuous tubular reactor.magnified imageEvolution of molecular weight as measured by GPC for chain‐extended latex in continuous tubular reactor.

In previous work, a modified nitroxide‐mediated miniemulsion polymerization was demonstrated in a continuous tubular reactor to prepare a latex of polystyrene homopolymer dispersed in water. There, the initial reaction step (low conversion bulk polymerization to prepare the macroinitiator) was done in a batch reactor while the miniemulsion polymerization step was done in a continuous tubular reactor. The present paper describes an extension of that work in which all the reaction steps have been achieved in the continuous tubular reactor. Chain extension of the polystyrene latex to give polystyrene‐block‐poly(butyl acrylate) diblock and polystyrene‐block‐poly(butyl acrylate)‐block‐polystyrene triblock copolymers is also described.

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Residence time distribution (RTD) studies were done to determine the flow characteristics in a continuous tubular reactor. Pulse tracer experiments were done at different flow rates and temperatures, and a comparison was made between a homogeneous aqueous salt mixture versus a heterogeneous miniemulsion mixture. The heterogeneous system was studied under two different conditions, one with a monomer‐in‐water droplet dispersion and one with fully formed polymer particles dispersed in water. There were differences observed between all of the systems tested and none of them matched an ideal plug flow condition. The reactor contains stagnant zones of varying volume and tracer spreading was observed in all cases. The dispersion model was found to model the system quite well in most cases.