Covalent Hydrogels with Dual Temperature and Time Memory Function Based on Supramolecular Host–Guest Complexation

Abstract

Temperature is among the most important measured physical parameters. Despite that numerous polymeric temperature sensors having been reported, none of these systems can record the time that the object was heated to a certain temperature. Here, we report a supramolecular approach for developing a smart polymeric hydrogel capable of measuring the temperature and the duration of the heat exposure. This double memory principle is based on dual kinetic control of the dissociation of cyclobis(paraquat-p-phenylene) tetrachloride (CBPQT 4+ ,4Cl – )-naphthalene host–guest complexes within a thermoresponsive naphthalene functionalized poly(N-isopropylacrylamide) hydrogel. Heating-induced collapse of this LCST polymer hydrogel induces host–guest complex dissociation, followed by the diffusion-controlled release of the free CBPQT 4+ ,4Cl – host into the medium surrounding the hydrogel. This partial host release is governed by the heat exposure time and the heating temperature that controls the extent of dehydration of the hydrogel and, thus, the diffusion rate of the CBPQT 4+ ,4Cl – . Hence, the amount of host released is an indicator for both the heating temperature and the heating time of the hydrogel and can be recorded by determining the reswelling capability of the hydrogel in water. As such, measuring the reswelling capability provides information on how long the hydrogel system was exposed to a certain temperature.

Plug-and-Play Biointerfaces: Harnessing Host–Guest Interactions for Fabrication of Functional Polymeric Coatings

“…Fabrication methods using host–guest supramolecular interactions have attracted significant attention since self-assembly processes drive the association of building blocks at the molecular level. − Among reported macrocyclic host molecules, crown ethers, cyclodextrins (CDs), , calixarenes, and calixpyrroles are among the most widely explored ones. In addition to these traditional hosts, cucurbiturils (CB­[ n ]), blue-box, pillar­[ n ]­arenes, and resorcinarene have attracted attention in recent years. Among these macrocyclic structures, CDs have been widely used to fabricate polymeric self-assembled materials for biomedical applications due to their ready availability, low toxicity, excellent biocompatibility, and ability to make strong complexation with a variety of guests. − Among CD-based host–guest pairs, adamantane (Ada) is a rigid hydrophobic molecule known to form a stable complex with βCD with a high association in an aqueous environment .…”

“… 24 − 26 Among reported macrocyclic host molecules, crown ethers, 27 cyclodextrins (CDs), 28 , 29 calixarenes, 30 and calixpyrroles 31 are among the most widely explored ones. In addition to these traditional hosts, cucurbiturils (CB[ n ]), 32 blue-box, 33 pillar[ n ]arenes, 34 and resorcinarene 35 have attracted attention in recent years. Among these macrocyclic structures, CDs have been widely used to fabricate polymeric self-assembled materials for biomedical applications due to their ready availability, low toxicity, excellent biocompatibility, and ability to make strong complexation with a variety of guests.…”

Reversible Electronic Patterning of a Dynamically Responsive Hydrogel Medium

“…[6,7] Presumably, the modularity and versatility of these "dynamic patterning modules" [8][9][10] confer efficiencies for biology, while also providing individual organisms with mechanisms to learn and adapt to their local conditions. [11] In technological studies, dynamically responsive materials systems [12][13][14][15][16] offer the opportunity to control bottom-up self-assembly by the precise addition of external information (i.e., top-down cues) that are often imposed using stamping [17][18] or printing [19] methods. In many such studies, synthetic polymers are selected that possess intrinsic stimuli-responsive properties (e.g., thermalresponsiveness) [13] or are synthesized to have moieties that confer dynamically responsive properties (e.g., pH-dependent metal chelating groups).…”

“…In technological studies, dynamically responsive materials systems [ 12–16 ] offer the opportunity to control bottom‐up self‐assembly by the precise addition of external information (i.e., top‐down cues) that are often imposed using stamping [ 17–18 ] or printing [ 19 ] methods. In many such studies, synthetic polymers are selected that possess intrinsic stimuli‐responsive properties (e.g., thermal‐responsiveness) [ 13 ] or are synthesized to have moieties that confer dynamically responsive properties (e.g., pH‐dependent metal chelating groups).…”