Ring-Opening Polymerization Using Flow Microreactor Systems

5 Ring-Opening Polymerization Using Flow Microreactor Systems 

The most popular approach for the synthesis of polyamides from amino acids [224] is the amino acid V-carboxyanhydride (NCA) method (Fig. 31) [225]. The initiation with a base such as a tertiary amine is followed by the reaction of another NCA molecule with the resulting activated NCA anirm to produce a dimer with an electrophilic N-acyl NCA end group and a nucleophihc carbamate group. Then, N-carbamic acid is detached as carbrai dioxide during the propagation reaction. It is known that deprotonation of NCA and attack of the NCA anion are relatively fast 

A silicon-glass-based flow microreactor system that is suitable for long periods of use has been developed and applied to the polymerization of amino acid NCAs [229]. The flow microreactor exhibits excellent controllability of the molecular weight distribution. Moreover, a single flow microreactor can produce 100 mg/min of copoly(Lys-Leu). This means that more than 200 g of copoly(Lys-Leu) acids can be produced in 2 months. 

The continuous-flow microwave-assisted polymerization of 2-ethyl-2-oxazoline was reported by Paulus et al. [232]. The flow process overcomes the problems associated with scale-up of the batch process, including safety issues. 

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