Abstract
A controlled radical polymerization process using the Reversible Addition-Fragmentation Chain Transfer (RAFT) approach was scaled up by a factor of 100 from a small laboratory scale of 5 mL to a preparative scale of 500 mL, using batch and continuous flow processing. The batch polymerizations were carried out in a series of different glass vessels, using either magnetic or overhead stirring, and different modes of heating: Microwave irradiation or conductive heating in an oil bath. The continuous process was conducted in a prototype tubular flow reactor, consisting of 6 mm ID stainless steel tubing, fitted with static mixers. Both reactor types were tested for polymerizations of the acid functional monomers acrylic acid and 2-acrylamido-2-methylpropane-1-sulfonic acid in water at 80 °C with reaction times of 30 to 40 min. By monitoring the temperature during the exothermic polymerization process, it was observed that the type and size of reactor had a significant influence on the temperature profile of the reaction.
Highlights
The Reversible Addition-Fragmentation Chain Transfer (RAFT) method is arguably the most convenient and versatile approach to controlled free radical polymerizations, as it is compatible with most monomers amenable to free radical polymerization [1,2,3,4,5,6]
We report the scale-up of exothermic RAFT
The reactions were performed in a prototype tubular continuous flow reactor containing static mixer arrays and compared to batch reactions performed at different scales and in different reaction vessels
Summary
The Reversible Addition-Fragmentation Chain Transfer (RAFT) method is arguably the most convenient and versatile approach to controlled free radical polymerizations, as it is compatible with most monomers amenable to free radical polymerization [1,2,3,4,5,6]. Microreactor technology has transformed the way chemical synthesis is conducted in research laboratories [7,8,9,10,11,12,13,14,15,16,17,18,19,20], replacing batch reactions classically carried out in laboratory glassware by continuous flow processes using tubular [21,22,23,24] or chip/plate based [25,26,27] reactor designs. The advantageous heat transfer performance of micro-structured flow reactors for use in exothermic solution phase polymerization reactions was first described by Iwasaki et al [28]. The results were compared to a macro-scale batch process resulting in an improved control over the molecular weight distribution of the polymer product in the microreactor, especially for the highly exothermic reactions of (meth)acrylate monomers. The reactions were performed in a prototype tubular continuous flow reactor containing static mixer arrays and compared to batch reactions performed at different scales and in different reaction vessels
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