Xylan-rich Hemicelluloses-graft-Acrylic Acid Ionic Hydrogels with Rapid Responses to pH, Salt, and Organic Solvents

Abstract

Exploitation of biomaterials derived from renewable resources is an important approach to address environmental and resource problems in the world today. In this paper, novel ionic hydrogels based on xylan-rich hemicelluloses were prepared by free radical graft copolymerization of acrylic acid (AA) and xylan-rich hemicelluloses (XH) by using N,N-methylene-bis(acrylamide) (MBA) as cross-linker and ammonium persulfate/N,N,N',N'-tetramethylethylenediamine (APS/TMEDA) as redox initiator system. The network characteristics of the ionic hydrogels were investigated by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), as well as by determination of mechanical properties, swelling, and stimuli responses to pH, salts, and organic solvents. The results showed that an increase in the MBA/XH or AA/XH ratio resulted in higher cross-linking density of the network and thus decreased the swelling ratio. Expansion of the network hydrogels took place at high pH, whereas shrinkage occurred at low pH or in salt solutions as well as in organic solvents. The ionic hydrogels had high water adsorption capacity and showed rapid and multiple responses to pH, ions, and organic solvents, which may allow their use in several areas such as adsorption, separation, and drug release systems.

Hemicellulose-Based Hydrogels Present Status and Application Prospects: A Brief Review

“…The results showed as-prepared hydrogels can absorb 91 to 822 times weight of itself, and were sensitive to ph. The hydrogels also have the feature of reversible on-off switching behavior in acidic-basic solutions or water-ethanol or acetone solution (Peng, Ren, Zhong, Peng, & Sun, 2011). In another study, the hydrogel by grafting acrylic acid on the backbone of hemicellulose possessed honeycomb-like porous structure and had remarkable pH-sensitivity.…”

“…The mechanism of the preparation of hydrogels briefly as follows: sulfate anion radical generated from ammonium persulfate deprives of hydrogen from the hydroxyl group of hemicellulose backbone to form alkoxy radicals, resulting in active centers on the hemicellulose to radically initiate polymerization (Peng et al, 2011;Sun et al, 2015). (Cao, Peng, Zhong, & Sun, 2014) and potassium persulfate (KPS) (Maleki, Edlund, & Albertsson, 2015), sodium sulfite (Maleki et al, 2015), AcGGM was materials for thiolation through one-pot synthetic methodology, this reaction realized by the AcGGM-mediated nucleophilic ring-opening reaction of thiobutyrolactone via the activation of the polysaccharide pendant hydroxyl groups.…”

Chemical Pretreatments of Wood Chips Prior to Alkaline Pulping - A Review of Pretreatment Alternatives, Chemical Aspects of the Resulting Liquors, and Pulping Outcomes

“…The second class of polymeric application manufactured from hemicelluloses includes the production of hydrogels (Gabrielii et al 2000;Peng et al 2011a;Pohjanlehto et al 2011). Due to the high hydrophilicity, the abundance of hydroxyl groups together with biodegradability, nontoxicity, and responsiveness to environmental stimuli (pH, ionic strength, solvent composition, temperature, as well as electric and magnetic fields) hemicelluloses-derived hydrogels have attracted attention, especially in the manufacture of biomedical product applications, such as controlled drug delivery systems, biological scaffolds for tissue engineering, biosensors, immobilized carriers for the encapsulation of living cells, and barrier materials for regulating biological adhesions (Söderqvist-Lindblad et al 2005;Edlund and Albertsson 2008;Sun et al 2013;Maleki et al 2014).…”

Enhanced Absorbent Products Incorporating Cellulose and Its Derivatives: A Review

“…The importance of hemicellulose was also shown by Laine and Stenius (1997), who demonstrated a positive relationship between fiber ionic charge and swelling with water. Recently several researchers have attempted to take advantage of the hydrophilic nature of hemicelluloses by using them as a key component of highly absorbent hydrogels (Gabrielli and Gatenholm 1998;Gabrielli et al 2000;Meena et al 2011;Peng et al 2011;Pohjanlehto et al 2011;Salam et al 2011a;Yang et al 2011;Karaaslan et al 2010Karaaslan et al , 2011Karaaslan et al , 2012.…”