Artificial enzymes based on imprinted liquid‐crystalline materials

Abstract

Liquid‐crystal elastomers, imprinted around indole, are assessed as artificial enzymes for the isomerisation of benzisoxazole into 2‐cyano phenol. Two types of material are synthesised, tested in the catalysis and compared with non‐liquid‐crystal imprinted polymers: an imprinted liquid‐crystalline elastomer and a semi‐interpenetrated imprinted liquid‐crystal network. The catalytic effect of all materials is close. However, the main benefit for the liquid‐crystal elastomer is shown to be the shape memory of the material at the molecular scale, because the isomerisation kinetics are found to be identical before and after deformation of the cavities either by thermal treatment up to the isotropic state or by solvent induced swelling. This fact is related to the coupling between the order and the conformation of the polymer chains, which is fixed by the crosslinking process. On the other hand, the imprinted sites of the semi‐interpenetrated imprinted liquid‐crystal elastomer are shown to be almost 100 times more active than the non‐imprinted sites in the catalysis. This factor is only 22 for the corresponding non‐liquid‐crystalline network.

Keywords:

• elastomers
• enzymes
• liquid‐crystalline polymers
• molecular imprinting
• semi‐interpenetrated networks

Acknowledgements

The authors wish to thank the French Ministry of Education and Research for a grant to M. Weyland. They also wish to thank P. Vicendo and C. Blonski for helpful discussions. Y. Chollet, P. Lavedan and C. Routaboul are acknowledged for their help in NMR and IR experiments. The Center of Electronic Microscopy Applied to Biology of the medicine faculty of Toulouse is also acknowledged for help with SEM experiments.