Experimental section

Materials

Reagents and chemicals used in this work, including methylene blue, isoprene, maleic acid anhydride, dimethylformamide (DMF), glyoxal, cyclohexylamine, ethanol, 2-octanol, methanesulfonyl chloride, triethylamine, 4-dimethylaminopyridine (DMAP), and dichloromethane (DCM), were all purchased from Sigma-Aldrich and used without further purification. Materials used for fabricating the CSTR cascade were bought from McMaster-Carr Supply Company.

Reactor design

A single CSTR unit consists of three main components, including a polytetrafluoroethylene (PTFE) reactor block, a heat-resistant glass cover and a stainless steel cover (Fig. 1a). The PTFE reactor is a 30 mm × 30 mm square block with a thickness of 19 mm. The cylinder-shaped inner chamber has a diameter of 18 mm and a depth of 10 mm. An O-ring gap surrounds the chamber for the 1/16′′ FEP O-ring with a silicone core. The glass cover is heat-resistant borosilicate glass (Pyrex) with dimensions of 30 mm × 30 mm × 4.8 mm. The stainless steel cover is super-corrosion-resistant 316 stainless steel with dimensions of 30 mm × 30 mm × 3.2 mm. All extruded 2D shapes were fabricated using water jet machining (OMAX MicroMAX JetMachining Center). In addition to 2D shapes, the reactor chamber and the O-ring gap were machined using CNC milling (ProtoTRAK SMX). Multiple CSTR units are mounted on an aluminum holder (Fig. 1b). The aluminum holder (150 mm × 70 mm × 3.2 mm) can hold up to 8 CSTRs. All connection ports have 1/4-28 threads, which can be directly connected using common IDEX fittings (IDEX Health & Science LLC.) without additional adapters. Two CSTRs are connected using a tube with 1/4-28 thread outside.

Fig. 1 Sketch of the miniature CSTR cascade design. (a) The single-stage CSTR shown in CAD drawing, and the three main components of the actual product. (b) Multiple CSTRs in series on an aluminium holder. The white scale bars in the pictures above are 10 mm.