Dual Cross-Linked Hydrogels That Undergo Structural Transformation via Selective Triggered Depolymerization

Abstract

This study demonstrates the preparation of dual cross-linked hydrogels capable of selective, spontaneous de-cross-linking behavior triggered by head-to-tail depolymerization. A primary covalent structure of the materials was established on a thermoresponsive network containing pendant functional moieties that could induce noncovalent interaction when combined with a macro-cross-linker. The incorporation of the macro-cross-linker not only reinforced the entire structure while providing secondary physical cross-linking but also caused the resulting materials to show autonomous responses via depolymerization. As a result, transformation of the material was achieved without structural collapse, as the noncovalent network in the materials was rapidly, selectively, and completely removed through the depolymerization reaction of the polymer cross-linker when initiated by a trace (<0.01 wt %) stimulus. Thus, the macroscopic changes in the physical and chemical properties of the hydrogels were investigated. Furthermore, we used the proposed strategy to design actuating materials that exhibit reversible, programmed, large-scale behavior and finally demonstrated re-cross-linking by the addition of an extra macro-cross-linker after the de-cross-linking reaction.

Biobased Stimuli-Responsive Hydrogels That Comprise Supramolecular Interpenetrating Networks and Exhibit Programmed Behaviors

“…Poly-(NIPAM)s generally exhibit volumetric collapse via coil-toglobule transition above the lower critical solution temperature (LCST) but are rehydrated with water as forming hydrogen bonds below LCST, causing a reversible change in the transmittance of the designed hydrogels. 45 As the temperature increased from 26.8 to 28.3 °C, the transmittance of ncDNH decreased sharply due to the LCST behavior (black, Figure 3a). Similarly, the control ncSNH demonstrated a decrease in transmittance upon heating from 25.4 to 27 °C (sky blue, Figure 3a).…”

Designing Internal Hierarchical Porous Networks in Polymer Monoliths that Exhibit Rapid Removal and Photocatalytic Degradation of Aromatic Pollutants

“…Therefore, the photocatalytic degradation of the MB dyes can be accelerated in CDPs‐HIPE‐TiO 2 , compared to the reactions in other control monoliths. Here, we demonstrated the conceptual scheme to impart the catalytic activity to the materials using TiO 2 particles, but addition of other components including 2D materials [ 64,65 ] or orthogonal control of the network [ 66,67 ] would make use of the internal structure in a more practical, sophisticated sense.…”

Recent Progress on Molecular Photoacoustic Imaging with Carbon-Based Nanocomposites

“…We anticipate that the imaging techniques and the contrast agents described will be further developed into more advanced materials and to monitor or manipulate them using the PA signals generated from the materials [ 124 , 125 ]. Therefore, on the one hand, the agent materials can be incorporated into biocompatible polymers such as hydrogels or bio-based thermosets, to enhance sensing ability as a signal transducer for PA signals under physiological conditions [ 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 ]. On the other hand, they would provide spatiotemporal control of stimuli-responsive materials that exhibit auto-inductive or reversible responses [ 133 , 134 , 135 , 136 , 137 , 138 ] or would be used to analyze interior structures when embedded in complex materials containing biomimetic or hierarchical structures [ 104 , 117 , 139 , 140 , 141 ].…”