Chemical signal activation of an organocatalyst enables control over soft material formation

Abstract

Cells can react to their environment by changing the activity of enzymes in response to specific chemical signals. Artificial catalysts capable of being activated by chemical signals are rare, but of interest for creating autonomously responsive materials. We present an organocatalyst that is activated by a chemical signal, enabling temporal control over reaction rates and the formation of materials. Using self-immolative chemistry, we design a deactivated aniline organocatalyst that is activated by the chemical signal hydrogen peroxide and catalyses hydrazone formation. Upon activation of the catalyst, the rate of hydrazone formation increases 10-fold almost instantly. The responsive organocatalyst enables temporal control over the formation of gels featuring hydrazone bonds. The generic design should enable the use of a large range of triggers and organocatalysts, and appears a promising method for the introduction of signal response in materials, constituting a first step towards achieving communication between artificial chemical systems.

Organocatalysis in aqueous media

“…32 catalyses the popular bioconjugation strategies of hydrazone and oxime formation through a transamination mechanism (Fig.4, Table 1 -reaction 16). The bioconjugation enables amongst others functionalization of polymers 134 and biomolecules for in vitro and in vivo studies. 133,135 The nucleophilic catalytic mechanism of 32 was elucidated by Cordes and Jencks back in 1962 (FIG.…”

Pros and Cons: Supramolecular or Macromolecular: What Is Best for Functional Hydrogels with Advanced Properties?

“…), gels responding to a very broad range of stimuli have been reported 2d,43. However, the range in resulting responses is substantially smaller than for MHGs, with the majority leading to a sol–gel or gel–sol transition . A few exceptions include thermo‐induced gel‐to‐gel transitions, chemical‐reaction‐induced viscosity changes,25a and light or charge‐transfer‐induced changes in optical properties .…”

Conditional Copper‐Catalyzed Azide–Alkyne Cycloaddition by Catalyst Encapsulation

“…Such control is usually made possible by light‐activated click chemistry, with potential associated problems of phototoxicity and side reactions. In expanding the CuAAC toolbox there is therefore a desire for a general method to spatiotemporally control the catalytic activity of the CuAAC to enable spatiotemporal control over gel formation, polymer conjugation, material properties, fluorescence properties, and biomolecule labeling.…”