Extracted nanocellulose from natural resources commonly requires modification before it is used as an effective nanofiller. In the present study, through an enzymatic polymerization of α-d-glucose 1-phosphate from the primer 2-(glucosyloxy)ethyl methacrylate (GEMA), a novel type of two-dimensional methacrylate-containing cellulose nanosheets (CNS) with a thickness of about 6 nm, named as GEMA-CNS, was directly synthesized under a mild condition by a “bottom-up” method. The structure and morphology of GEMA-CNS were characterized by 1H-nuclear magnetic resonance (NMR), matrix-assisted laser desorption/ionization time-of-flight mass spectra (MALDI-TOF MS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Afterward, the obtained GEMA-CNS was covalently incorporated into poly(ethylene glycol) matrix through thiol–ene Michael addition, fabricating a series of GEMA-CNS-based nanocomposite hydrogels. The addition of GEMA-CNS effectively improved the mechanical strength and altered the internal network structures of hydrogels; additionally, the swelling/biodegradation behaviors of gels in phosphate buffer saline (pH 7.4) at 37 °C were affected to some degree. This species of property-tunable hydrogels with GEMA-CNS dosage demonstrates potential applications in tissue engineering. The current presentation opens a new road for direct enzymatic preparation of reactive nanocellulose and its novel applications in nanocomposite materials.

A series of aerogels composed of chitosan and/or silica were fabricated by tuning their feeding ratios. They were characterized by FTIR, thermogravimetric analysis, and X-ray diffraction; pore structures were analyzed by Brunauer–Emmett–Teller (BET) nitrogen sorption and scanning electron microscopy (SEM); adsorption capacities to Congo red were explored as well. The incorporation of silica enhances the thermostabilization of chitosan in gels. And as silica content increases, bulk densities of aerogels decrease gradually, while porosities, pore volumes, and surface areas obtained via BET method increase consequently; as well, porous structure becomes more regular and pore size tends to be smaller that was observed by SEM. The adsorption capacities of chitosan-containing aerogels to Congo red reach as high as about 150 mg/g, much higher than that of pure silica (17 mg/g), demonstrating their potential as a class of novel adsorbent materials.

A series of poly(N-isopropylacrylamide) (PNIPA) hydrogels were fabricated through click chemistry by using a well-defined azido-PNIPA carrying pendant azido groups, and linear α,ω-bis propargyl PNIPAs with different chain lengths. Here linear α,ω-bis propargyl PNIPAs were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization by using a bis propargyl terminal chain transfer agent, whose chain lengths were modulated by changing polymerization conditions. The obtained hydrogels showed increasing ESR values in the swollen state and increasing volume phase transition temperatures (VPTTs) with increasing molecular weights of bis propargyl PNIPAs, ascribed to the lengthening distance between crosslinks and improving hydrophilicity. The incorporation of amine together with crosslinking modified the hydrophilicity of a click hydrogel, resulting in the elevated VPTT and additional pH sensitivity. The present study provided a facile method to regulate swelling properties and/or to impart special functions for PNIPA hydrogels, by adjusting the chain length of crosslinkers or by introducing other functional groups.

Different amounts of graphene oxide (GO) were incorporated to N,N-dimethylaminoethyl methacrylate (DMAEMA), fabricating a series of pH and temperature dual sensitive PDMAEMA/GO hybrid hydrogels by in situ polymerization. Their microscopic network structures as well as swelling properties and Cr(VI) adsorption were characterized. The equilibrium swelling ratios (ESR) of hydrogels increased significantly with 0.5 wt% GO feeding of DMAEMA amount, and then decreased with further GO loading increasing. All hydrogels showed obvious deswelling when pH value of swelling mediums increased from 5 to 10 gradually. At pH 7, hydrogels revealed slight ESR increment with temperature up to 50 °C, above which obvious deswelling occurred. In pH 8 buffer, 0.5 wt% of GO loading triggered lower critical solution temperature (LCST) to decrease by 3 °C, and 2–7 °C increment was observed when 1–6 wt% of GO was loaded, as compared with that of GO-free PDMAEMA hydrogel. Cr(VI) adsorption of hydrogels was also improved by the introduction of GO to some extent, and the maximum Cr(VI) adsorption of 180 mg/g was realized, indicating that the obtained PDMAEMA/GO hybrid hydrogels possess excellent adsorption performance.

Water properties in a novel thermoswelling hydrogel, which was prepared from poly(vinyl alcohol)-trimellitate (PVA-T) by a simple chemical cross-linking and swollen in 0.1−1.0 M Li2SO4 solutions, were investigated through nuclear magnetic resonance and Fourier transform infrared (FTIR) spectroscopies. The spin−spin relaxation of the water proton in the hydrogel was measured at 5−35 °C, and the results were analyzed with a two-component model to obtain a long T2 and a short T2 as well as their fractions (fshort = 1 − flong). The fshort values thus obtained proved to be a linear function of the gel swelling ratio, and all of the data, except for an upper deviation at 1.0 M Li2SO4, were found to be on an almost same line irrespective of the temperature and the salt concentration. This dependency of fshort on the swelling degree strongly suggests that the temperature increment has an equivalent effect as that of the SO42- concentration; namely, scission of inter(intra-)molecular hydrogen bonding (HB) between the COOHs on the side group must be responsible for the observed thermoswelling in the sulfate salt solutions. The upper deviation of fshort at 1.0 M from the “master line” was reasonably interpreted in terms of the salting-out effect by the concentrated sulfate anion. On the other hand, attenuated total reflection−FTIR measurements for a gel plate revealed that an appreciable dissociation of the carboxyl group occurred only in the 1.0 M Li2SO4 system. This finding, in turn, means that gel swelling with an increase in the salt concentration up to 0.5 M is not caused by the ionization of the gel and supports the scission of the intermolecular HB. Hydrophobic hydration around the main chain was investigated via a peak shift of the stretching vibration of −CH2−, and the slight red shift observed only at 1.0 M suggested that the salting-out effect onto the hydrophobic hydration is rather limited and the hydration around the main chain still remained even with the significant deswelling at 1.0 M.

Different amounts of graphene oxide (GO) were incorporated to N,N-dimethylaminoethyl methacrylate (DMAEMA), fabricating a series of pH and temperature dual sensitive PDMAEMA/GO hybrid hydrogels by in situ polymerization. Their microscopic network structures as well as swelling properties and Cr(VI) adsorption were characterized. The equilibrium swelling ratios (ESR) of hydrogels increased significantly with 0.5 wt% GO feeding of DMAEMA amount, and then decreased with further GO loading increasing. All hydrogels showed obvious deswelling when pH value of swelling mediums increased from 5 to 10 gradually. At pH 7, hydrogels revealed slight ESR increment with temperature up to 50 °C, above which obvious deswelling occurred. In pH 8 buffer, 0.5 wt% of GO loading triggered lower critical solution temperature (LCST) to decrease by 3 °C, and 2–7 °C increment was observed when 1–6 wt% of GO was loaded, as compared with that of GO-free PDMAEMA hydrogel. Cr(VI) adsorption of hydrogels was also improved by the introduction of GO to some extent, and the maximum Cr(VI) adsorption of 180 mg/g was realized, indicating that the obtained PDMAEMA/GO hybrid hydrogels possess excellent adsorption performance.