Temporal Control of Gelation and Polymerization Fronts Driven by an Autocatalytic Enzyme Reaction

Abstract

Chemical systems that remain kinetically dormant until activated have numerous applications in materials science. Herein we present a method for the control of gelation that exploits an inbuilt switch: the increase in pH after an induction period in the urease‐catalyzed hydrolysis of urea was used to trigger the base‐catalyzed Michael addition of a water‐soluble trithiol to a polyethylene glycol diacrylate. The time to gelation (minutes to hours) was either preset through the initial concentrations or the reaction was initiated locally by a base, thus resulting in polymerization fronts that converted the mixture from a liquid into a gel (ca. 0.1 mm min−1). The rate of hydrolytic degradation of the hydrogel depended on the initial concentrations, thus resulting in a gel lifetime of hours to months. In this way, temporal programming of gelation was possible under mild conditions by using the output of an autocatalytic enzyme reaction to drive both the polymerization and subsequent degradation of a hydrogel.

Mechanistic Kinetic Modeling of Thiol–Michael Addition Photopolymerizations via Photocaged “Superbase” Generators: An Analytical Approach

“…13,52 Yet, they are known to contain trace amounts of acidic species, as impurities, that temporally suppress the thiol–Michael reaction in its initial stages and reduce the conversion rates if not properly eliminated prior to the reaction. 53 This inhibitory effect is characterized by the development of an induction time, τ , given by eq 29, derived from an acid–base neutralization equilibrium established as bimolecular termination mechanism for the photogenerated base. Figure 5a describes the effect of the induction time on the reaction kinetics obtained from numerical computations of the mechanistic scheme detailed in Table 1.…”

Dynamic Environments as a Tool to Preserve Desired Output in a Chemical Reaction Network

“…[1] Examples of networks giving temporal, or spatiotemporal, control over the concentrations of the molecules in the system include the generation of wave fronts, [2] pattern formation with as o-calledg o-fetch model, [3] oscillations, [4][5][6][7][8] supramolecular oscillators [9] synchronisation and pattern formation with multiple oscillators through diffusional spatiotemporal coupling, [10] adaptive response networks, [11] systemss howing homeostasis, [12] self-replicating systems that can diversify into differents pecies, [13] self-replicators that can transiently form micelles, [14,15] temporally controlled material properties [16][17][18] and transientv esicle, [19] droplet, [20] fibril and gel formation. [1] Examples of networks giving temporal, or spatiotemporal, control over the concentrations of the molecules in the system include the generation of wave fronts, [2] pattern formation with as o-calledg o-fetch model, [3] oscillations, [4][5][6][7][8] supramolecular oscillators [9] synchronisation and pattern formation with multiple oscillators through diffusional spatiotemporal coupling, [10] adaptive response networks, [11] systemss howing homeostasis, [12] self-replicating systems that can diversify into differents pecies, [13] self-replicators that can transiently form micelles, [14,15] temporally controlled material properties [16][17][18] and transi...…”

Temporally‐Programmed Transient Supramolecular Gels

“…The second trigger causes a subsequent decrease in pH ( Figure ). To minimize mixing issues during gelation, we utilize the autocatalytic reaction between urease and urea to generate NH 3 for a controlled and uniform pH increase that leads to homogeneous hydrogelation as we have shown previously . This method developed by Jee et al allows a controlled increase in pH .…”