Selective De-Cross-Linking of Transformable, Double-Network Hydrogels: Preparation, Structural Conversion, and Controlled Release

Abstract

This study has demonstrated the design of stimuli-responsive double-network hydrogels that are formed by sequential polymerization and show chemical transformation by selective de-cross-linking without structural failure owing to chemical orthogonality. Each self-immolative and thermoresponsive network established together the double-network structure through a thiol−ene click reaction and radical polymerization. The hydrogel exhibited enhanced mechanical strength but chemically transformed through the selective de-cross-linking of specific network triggered by a molecular stimulus, which significantly alters physical properties of the material such as tunable toughness and lower critical solution temperature behavior. In addition, the material displayed a thermoresponsive, controlled release. Only after treatment with the stimulus did the hydrogel release cargo molecules on demand via de-cross-linking while maintaining the entire structure.

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

“…The cloud points where 50% transmittance appeared were found to be 25.7 and 27 °C for ncSNH and ncDNH, respectively. We conjecture that the delayed LCST behavior in ncDNH can be attributed to the carrageenan network that forms the interpenetrating structure and hampers the phase transition of the second, NIPAM-based network . The macroscopic thermal behavior was nonetheless well developed in the entire supramolecular networks, as observed in common linear poly­(NIPAM) chains.…”

“…We conjecture that the delayed LCST behavior in ncDNH can be attributed to the carrageenan network that forms the interpenetrating structure and hampers the phase transition of the second, NIPAM-based network. 46 The macroscopic thermal behavior was nonetheless well developed in the entire supramolecular networks, as observed in common linear poly(NIPAM) chains. The representative photographs for the turbidity change in ncDNH are shown in Figure S5.…”

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 ].…”

Recent Progress on Near-Infrared Photoacoustic Imaging: Imaging Modality and Organic Semiconducting Agents

“…Additionally, self-propagating reactions, such as self-assembly or triggered head-to-tail depolymerization [114,115,116,117,118], can readily turn on–off or even amplify the PA signal. Furthermore, addition of the PA properties to various network materials, such as porous materials or hydrogels [119,120,121,122,123,124,125,126], can provide a non-destructible in situ monitoring system or facile, selective manipulation of physical properties of the networks in response to NIR.…”