Multiresponsive Cellulose Nanocrystal Cross-Linked Copolymer Hydrogels for the Controlled Release of Dyes and Drugs.

Yuchen Jiang,Zaiwu Yuan,Fangong Kong,Guihua Li,Chenyu Yang

doi:10.3390/polym13081219

Yuchen Jiang, Zaiwu Yuan + Show 3 more

Open Access

https://doi.org/10.3390/polym13081219

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Abstract

Multiresponsive hydrogels have attracted tremendous interest due to their promising applications in tissue engineering, wearable devices, and flexible electronics. In this work, we report a multiresponsive upper critical solution temperature (UCST) composite hydrogel based on poly (acrylic acid-co-acrylamide), PAAc-co-PAAm, sequentially cross-linked by acid-hydrolysis cellulose nanocrystals (CNCs). Scanning electron microscopy (SEM) observations demonstrated that the hydrogels are formed by densely cross-linked porous structures. The PAAc/PAAm/CNC hybrid hydrogels exhibit swelling and shrinking properties that can be induced by multiple stimuli, including temperature, pH, and salt concentration. The driving force of the volume transition is the formation and dissociation of hydrogen bonds in the hydrogels. A certain content of CNCs can greatly enhance the shrinkage capability and mechanical strength of the hybrid hydrogels, but an excess addition may impair the contractility of the hydrogel. Furthermore, the hydrogels can be used as a matrix to adsorb dyes, such as methylene blue (MB), for water purification. MB may be partly discharged from hydrogels by saline solutions, especially by those with high ionic strength. Notably, through temperature-controlled hydrogel swelling and shrinking, doxorubicin hydrochloride (DOX-HCl) can be controllably adsorbed and released from the prepared hydrogels.

Highlights

Polymer hydrogels are three-dimensional polymer networks that can hold a large amount of water in the interspaces of their network [1,2,3,4,5]
The obtained suspension was purified by dialysis against Milli-Q water until the effluent remained at neutral pH, resulting in a desulfated cellulose nanocrystals (CNCs) (DCNC) suspension
A broad band from 3455 to 3100 cm−1 was observed for the PAAc-co-PAAm and PAAc/PAAm/CNC2 hydrogels, which is characteristic of hydrogen bonds between the −COOH groups of PAAc, –CONH2 groups of PAAm, and −OH groups of CNCs [28,29]

Summary

Introduction

Polymer hydrogels are three-dimensional polymer networks that can hold a large amount of water in the interspaces of their network [1,2,3,4,5]. Numerous polymers have been used to synthesize multiresponsive hydrogels, such as poly(N-isopropyl acrylamide) (PNIPAM) [14], polyacrylamide (PAAm) [15], poly (acrylic acid) (PAAc) [16], and poly(N, N-diethylacrylamide) [17]. Most thermoresponsive hydrogels are based on polymers with LCSTs, and polymers with UCSTs are rarely reported in the fabrication of smart hydrogels [19,20,21]. Thermoresponsive hydrogels were constructed with the incorporation of PAAm, which is not a thermoresponsive polymer. When polymer–polymer hydrogen bonds are stronger than polymer–water bonds, UCST polymers in water can be obtained. Dai and coworkers designed smart hydrogels with UCST characteristics by constructing an interpenetrating network (IPN) of PAAm and PAAc with chlorophyllin incorporated as the chromophore [16]

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