Macroscopic poly(2-hydroxyethyl acrylate) organogel beads were synthesised and applied as a chemoresponsive component in a smart valve. Monodisperse round beads with a diameter of about 3 millimetres were obtained by cryogenic dripping and subsequent photopolymerisation of the frozen aqueous monomer solution with UV light. The synthesis yields dimensionally stable, soft spheres with a macroporous architecture.
The elastic modulus increases from the soft, swollen state in benzyl alcohol to more than 250 kilopascal for networks of high density in the collapsed state in benzaldehyde. The degree of swelling in benzaldehyde is lower than in benzyl alcohol by a factor of 3 to 7, depending on the amount of polyethylene glycol diacrylate that is used as crosslinker in the precursor solution. Upon exposure to benzaldehyde the beads become opaque, which indicates a phase transition.
A kinetic analysis of the change in bead volume during swelling in benzyl alcohol and shrinkage in benzaldehyde gives half-life times in the range of 2 to 5 minutes. Beads with a macroscopic volume change of up to 71 percent were confined in a casing and acted as a smart valve in a reactor system.
The aerobic oxidation of benzyl alcohol to benzaldehyde with a catalyst mixture of TEMPOL and copper acetate demonstrated the high efficiency and the practical applicability of this self regulating component for flow control.
The study is a collaboration between the Institute of Technical and Macromolecular Chemistry at the University of Hamburg and the Institute of Technical Biocatalysis at Hamburg University of Technology, carried out within the Collaborative Research Centre CRC 1615 (SMART Reactors).
Jonah Hasse, Johannes Gmeiner, Gerrit A. Luinstra, Andreas Liese (2026). Autonomous Flow Control by a Responsive Poly(2-hydroxyethyl acrylate) Organogel-Valve during the Aerobic Oxidation of Benzyl Alcohol. Ind. Eng. Chem. Res. 65 (23), 12013-12026.
