Cellulose gelation in NaOH solutions is due to cellulose crystallization

Pereira, Ana; Duarte, Hugo; Nosrati, Pegah; Gubitosi, Marta; Gentile, Luigi; Romano, Anabela; Medronho, Bruno; Olsson, Ulf

doi:10.1007/s10570-018-1794-3

Cited by 26 publications

(28 citation statements)

References 24 publications

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“…In particular, it is well known that the stability of cellulose solutions in aqueous alkali is strongly temperature dependent. The gelation time has been found to decrease exponentially with increasing temperature [64,65]. Nevertheless, the reason for such gelation is still not fully clear [21,[65][66][67].…”

Section: Rheological Analysis Of Cellulose Solution and Cellulose/mbamentioning

confidence: 99%

“…The gelation time has been found to decrease exponentially with increasing temperature [64,65]. Nevertheless, the reason for such gelation is still not fully clear [21,[65][66][67]. Recently it has been suggested that the observed gelation is due to the precipitation of cellulose where the crystallites would then act as bridging points, competing for the same cellulose Polymers 2020, 12, 373 5 of 15 molecules, and thus acting as effective cross-linkers to form the 3D gel network [65].…”

Section: Rheological Analysis Of Cellulose Solution and Cellulose/mbamentioning

confidence: 99%

“…Nevertheless, the reason for such gelation is still not fully clear [21,[65][66][67]. Recently it has been suggested that the observed gelation is due to the precipitation of cellulose where the crystallites would then act as bridging points, competing for the same cellulose Polymers 2020, 12, 373 5 of 15 molecules, and thus acting as effective cross-linkers to form the 3D gel network [65]. Additionally, Isobe et al have suggested that upon heating a cellulose solution, gelation is triggered by the hydrophobic stacking of monomolecular sheets, followed by their mutual association via hydrogen bonding [68].…”

Section: Rheological Analysis Of Cellulose Solution and Cellulose/mbamentioning

confidence: 99%

“…When MBA is present, the amorphous cellulose content increases for the samples cured at higher temperature. Recently, the gelation of cellulose in alkaline aqueous solutions has been suggested as a consequence of cellulose precipitation/crystallization, where cellulose chains may participate in more than one crystallite, forming a cross-linked physical network [65]. suggested as a consequence of cellulose precipitation/crystallization, where cellulose chains may participate in more than one crystallite, forming a cross-linked physical network [65].…”

Section: Ftir and Raman Analysis Of Accessibility Of Cellulose Hydrogelmentioning

confidence: 99%

“…Recently, the gelation of cellulose in alkaline aqueous solutions has been suggested as a consequence of cellulose precipitation/crystallization, where cellulose chains may participate in more than one crystallite, forming a cross-linked physical network [65]. suggested as a consequence of cellulose precipitation/crystallization, where cellulose chains may participate in more than one crystallite, forming a cross-linked physical network [65]. Data strongly suggest that the MBA chemical cross-linking inhibits the system from forming more ordered crystallites, thereby resulting in a more amorphous hydrogel.…”

Section: Ftir and Raman Analysis Of Accessibility Of Cellulose Hydrogelmentioning

confidence: 99%

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Simple One Pot Preparation of Chemical Hydrogels from Cellulose Dissolved in Cold LiOH/Urea

et al. 2020

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In this work, non-derivatized cellulose pulp was dissolved in a cold alkali solution (LiOH/urea) and chemically cross-linked with methylenebisacrylamide (MBA) to form a robust hydrogel with superior water absorption properties. Different cellulose concentrations (i.e., 2, 3 and 4 wt%) and MBA/glucose molar ratios (i.e., 0.26, 0.53 and 1.05) were tested. The cellulose hydrogel cured at 60 • C for 30 min, with a MBA/glucose molar ratio of 1.05, exhibited the highest water swelling capacity absorbing ca. 220 g H 2 O/g dry hydrogel. Moreover, the data suggest that the cross-linking occurs via a basic Michael addition mechanism. This innovative procedure based on the direct dissolution of unmodified cellulose in LiOH/urea followed by MBA cross-linking provides a simple and fast approach to prepare chemically cross-linked non-derivatized high-molecular-weight cellulose hydrogels with superior water uptake capacity.Polymers 2020, 12, 373 2 of 15 enhance their potentials for applications, affect their release profiles and even allow specific processing, such as their injection [19]. In this respect, the mechanical and flow properties cannot be neglected when judging the feasibility of a hydrogel for a specific biological application. For instance, suitable flow properties allow hydrogels to be exciting candidates as injectable therapeutic delivery carriers if they are capable of shear-thinning during application at a proper shear stress; rapid self-healing; and adopting a solid-like behavior once the stress is removed [20].The general processing of cellulose, including the hydrogel formation, is challenging, since the biopolymer does not dissolve in water or in common organic solvents. Cellulose dissolution requires the disruption of the relatively extended inter-and intramolecular hydrogen bond network within its structure, as well as the van der Waals and hydrophobic interactions among the less polar faces of the anhydroglucose units [21][22][23][24].It is thus not surprising that for cellulose-based hydrogels the majority of studies have mainly focused on systems involving cellulose derivatives that can be easily dissolved in aqueous media [3,5,25,26]. Some studies have focused on physical hydrogels from several cellulose derivatives [27,28], while chemical cross-linking is more commonly used [3]. In this respect, chemically crosslinked cellulose-based hydrogels have been prepared using different methodologies, such as esterification [29], and radical and graft polymerization [30,31]. Methods involving free-radical initiation using an initiator compound or a high energy irradiation source, such as microwaves, γ-rays or glow discharge by electrolysis plasma, have also been suggested [29,[32][33][34][35][36][37][38][39]. Most of these processes involve time-consuming procedures requiring large quantities of chemicals, which make the post-treatment challenging. Consequently, these are generally expensive and poorly efficient strategies [32].Chemical cross-linking overcomes the problem of poor robustness of physical hydro...

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Section: Rheological Analysis Of Cellulose Solution and Cellulose/mbamentioning

confidence: 99%

Section: Rheological Analysis Of Cellulose Solution and Cellulose/mbamentioning

confidence: 99%

Section: Rheological Analysis Of Cellulose Solution and Cellulose/mbamentioning

confidence: 99%

Section: Ftir and Raman Analysis Of Accessibility Of Cellulose Hydrogelmentioning

confidence: 99%

Section: Ftir and Raman Analysis Of Accessibility Of Cellulose Hydrogelmentioning

confidence: 99%

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Simple One Pot Preparation of Chemical Hydrogels from Cellulose Dissolved in Cold LiOH/Urea

et al. 2020

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Tunable Photoluminescence Properties of Microcrystalline Cellulose with Gradually Changing Crystallinity and Crystal Form

Jiang

Liu

et al. 2021

Macromol. Rapid Commun.

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Nonconventional luminogens with persistent room temperature phosphoresce (p-RTP) are attracting increasing attention owing to their momentous significance and diverse technical applications in optoelectronic and biomedical. So far, the p-RTP emission of some amorphous powders or single crystals has been studied in depth. The p-RTP emission of amorphous and fully crystalline states and their emission properties are widely divergent, while the difference of their p-RTP emission mechanism is still controversial. The relevance between crystallinity change and p-RTP properties is rarely studied. Furthermore, there is almost no research on the photoluminescence (PL) property change and emission mechanism under the crystal form transformation of semi-crystalline polymer. Herein, microcrystalline cellulose (MCC) is chosen as a model compound to explore its crystallinity and the change in luminescence during the crystal form transformation to make up for this gap. By precisely adjusting the crystallinity and crystal cellulose conversion of MCC, the changing trend of quantum efficiency, and p-RTP lifetime is consistent with the change of crystallinity, and the cellulose I may be more beneficial to PL emission than cellulose II. Clustering-triggered emission mechanism can reasonably explain these interesting photophysical processes, which also can be supported by single-crystal analysis and theoretical calculations.

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Different rheological behaviours of cellulose/tetrabutylammonium acetate/dimethyl sulfoxide/water mixtures

et al. 2020

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Cellulose gelation in NaOH solutions is due to cellulose crystallization

Cited by 26 publications

References 24 publications

Simple One Pot Preparation of Chemical Hydrogels from Cellulose Dissolved in Cold LiOH/Urea

Simple One Pot Preparation of Chemical Hydrogels from Cellulose Dissolved in Cold LiOH/Urea

Tunable Photoluminescence Properties of Microcrystalline Cellulose with Gradually Changing Crystallinity and Crystal Form

Different rheological behaviours of cellulose/tetrabutylammonium acetate/dimethyl sulfoxide/water mixtures

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