High water-content thermoresponsive hydrogels via electrostatic macrocrosslinking of cellulose nanofibrils

Abstract

Atom transfer radical polymerization (ATRP) has been utilized to synthesize tri‐ and star‐block copolymers of poly(di(ethylene glycol)methyl ether methacrylate) (PDEGMA) and quaternized poly(2‐(dimethylamino)ethyl methacrylate) (qPDMAEMA). The block copolymers, all with a minimum of two cationically charged blocks, were sequentially used for electrostatic macrocrosslinking of a dilute dispersion of anionic TEMPO‐oxidized cellulose nanofibrils (CNF, 0.3 wt%), forming free‐standing hydrogels. The cationic block copolymers adsorbed irreversibly to the CNF, enabling the formation of ionically crosslinked hydrogels, with a storage modulus of up to 2.9 kPa. The ability of the block copolymers to adsorb to CNF was confirmed by quartz crystal microbalance with dissipation monitoring (QCM‐D) and infrared spectroscopy (FT‐IR), and the thermoresponsive properties of the hydrogels were investigated by rheological stress and frequency sweep, and gravimetric measurements. This method was shown to be promising for the facile production of thermoresponsive hydrogels based on CNF. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3415–3424

Alcohol induced gelation of TEMPO-oxidized cellulose nanofibril dispersions

“…These oxidized cellulose nanofibrils (OCNFs) are anionic particles and form stable dispersions of individualized nanofibrils in water. [20][21][22] OCNFs can selfassemble in an aqueous environment due to the influence of concentration, 23 OCNF aspect ratio, 24 co-solutes, such as surfactants, 16 salts, 9,25,26 or block copolymers 27 as well as pH. [28][29][30] This flexibility makes OCNFs a good choice as building blocks in self-assembled hydrogels.…”

Tough, Stimuli‐Responsive, and Biocompatible Hydrogels with Very High Water Content

“…Hydrogels with high water content have wide applications in biomaterials, biomedical, and agriculture fields, such as drug delivery and release, ophthalmic lens, bone repair, seed germination, and seedling growth, benefiting from their excellently biocompatible, environmentally friendly, and rapidly stimuli‐responsive features. In recent years, several novel hydrogels with high water content have been developed, and some are with very high water content, for example, polyethylene glycol‐containing hydrogels (97.5–99.4 wt%), noncovalent interactions and Diels–Alder chemical bonds dually cross‐linked hydrogels (98 wt%), graphene oxide/hemoglobin composite hydrogels (98.5 wt%), star‐block quaternized poly(2‐(dimethylamino)ethyl methacrylate)‐poly(di(ethylene glycol)methyl ether methacrylate) copolymer hydrogels (98.9–99.2 wt%), cucurbit[8]uril complexed supramolecular hydrogels (99.5–99.7 wt%), cellular‐structured nanofibrous hydrogels (99.8 wt%) . In general, two main strategies are adopted to prepare very‐high‐water‐content hydrogels.…”

“…In general, two main strategies are adopted to prepare very‐high‐water‐content hydrogels. The most widely employed one is called “direct preparation method,” which directly generates hydrogel networks at low solid concentrations by chemical and/or physical cross‐linking . Supramolecular self‐assembly interactions play a dominant role in this strategy.…”

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interactions and Diels-Alder chemical bonds dually cross-linked hydrogels (98 wt%), [3] graphene oxide/hemoglobin composite hydrogels (98.5 wt%), [6] starblock quaternized poly(2-(dimethylamino) ethyl methacrylate)-poly(di(ethylene glycol) methyl ether methacrylate) copolymer hydrogels (98.9-99.2 wt%), [7] cucurbit [8] uril complexed supramolecular hydrogels (99.5-99.7 wt%), [8] cellular-structured nanofibrous hydrogels (99.8 wt%). [9] In general, two main strategies are adopted to prepare very-high-water-content hydrogels.

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“…The most widely employed one is called "direct preparation method," which directly generates hydrogel networks at low solid concentrations by chemical and/ or physical cross-linking. [3,[6][7][8] Supramolecular self-assembly interactions play a dominant role in this strategy. The other strategy is called "equilibrium swelling method," which means a low-watercontent hydrogel is first prepared and then the as-prepared hydrogel is immersed into deionized water to reach equilibrium swelling.…”