Abstract
BackgroundSuperabsorbent hydrogels show a large potential in a wide array of applications due to their unique properties. Carboxymethylcellulose (CMC) is a commercially available water-soluble cellulose derivative of major interest in the hydrogel synthesis. High-energy irradiation allows the chemical crosslinking without the use of crosslinking agents, while the introduction of other natural or synthetic polymers offers a convenient way to modify the gels. In this study we examined the effect of the addition of starch, a low-cost renewable polysaccharide, on the properties of carboxymethylcellulose-based hydrogels.ResultsSuperabsorbent gels were prepared by gamma irradiation from aqueous mixtures of carboxymethylcellulose and starch. The partial replacement of CMC with starch improved the gel fraction, while a slight increase in the water uptake was also observed. However, very high starch content had a negative impact on the gelation, resulting in a decrease in gel fraction. Moreover, higher solute concentrations were preferred for the gelation of CMC/starch than for pure CMC. Hydrogels containing 30% starch showed the best properties: a water uptake of ~350 gwater/ggel was achieved with ~55% gel fraction synthesized from 15 w/w% solutions at 20 kGy. Heterogeneous gel structure was observed: the starch granules and fragments were dispersed in the CMC matrix. The swelling of CMC/starch gels showed a high sensitivity to the ionic strength in water due to the CMC component. However, the mixed gels are less sensitive to the ionic strength than pure CMC gels.ConclusionsThe introduction of starch to carboxymethylcellulose systems led to improved properties. Such gels showed higher water uptake, especially in an environment with high electrolyte concentration. CMC/starch hydrogels may offer a cheaper, superior alternative compared to pure cellulose derivative-based gels depending on the application.
Highlights
Superabsorbent hydrogels show a large potential in a wide array of applications due to their unique properties
Between 10 and 50% starch content the gel fraction did not change and at 10 kGy above 50% a sudden decrease was observed in the gel fraction
Hydrogels with superabsorbent properties were successfully prepared from carboxymethylcellulose/ starch solutions
Summary
Superabsorbent hydrogels show a large potential in a wide array of applications due to their unique properties. Carboxymethylcellulose (CMC) is a commercially available water-soluble cellulose derivative of major interest in the hydrogel synthesis. There is a significant and ever growing interest in the use of natural materials for superabsorbent preparation. The focus of these studies is mainly on the most common and Fekete et al Chemistry Central Journal (2017) 11:46 cheapest renewable resources, such as the cellulose [6], chitosan [7], starch and their derivatives, but other biomaterials like lignin [8] and various polysaccharide gums [9, 10] show a large potential. Carboxymethylcellulose (CMC) is in the center of research, but significant literature is available for other cellulose derivatives as well [6]
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