Mechanism of cellulose gelation from aqueous alkali-urea solution

Isobe, Noriyuki; Kimura, Satoshi; Wada, Masahisa; Kuga, Shigenori

doi:10.1016/j.carbpol.2012.03.023

Cited by 97 publications

(58 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The first experimental proof that molecular sheets are formed by hydrophobic interactions as the initial structure was demonstrated by Isobe et al, who reported that the peak of the (110) plane of Na-cellulose IV first appeared when cellulose from cellulose/aqueous alkali/urea solution was regenerated. 123 It should be mentioned that these features were already deduced from cellulose biosynthesis where the fundamental groundwork supports the previous ideas. 30,133,134 Essentially, it was found that cellulose crystallization is a three step process: (a) formation of monomolecular glucan chain sheets by van der Waals forces; (b) association of these sheets into mini-crystals by H-bonding; and (c) convergence of the mini-crystals (= subelementary fibrils) into the native crystalline microfibril.…”

Section: -127mentioning

confidence: 48%

See 1 more Smart Citation

The relevance of structural features of cellulose and its interactions to dissolution, regeneration, gelation and plasticization phenomena

Lindman

Medronho

Alves

et al. 2017

Phys. Chem. Chem. Phys.

195

109

View full text Add to dashboard Cite

aCellulose is the most abundant polymer and a very important renewable resource. Since cellulose cannot be shaped by melting, a major route for its use for novel materials, new chemical compounds and renewable energy must go via the solution state. Investigations during several decades have led to the identification of several solvents of notably different character. The mechanisms of dissolution in terms of intermolecular interactions have been discussed from early work but, even on fundamental aspects, conflicting and opposite views appear. In view of this, strategies for developing new solvent systems for various applications have remained obscure. There is for example a strong need for using forest products for higher value materials and for environmental and cost reasons to use water-based solvents. Several new water-based solvents have been developed recently but there is no consensus regarding the underlying mechanisms. Here we wish to address the most important mechanisms described in the literature and confront them with experimental observations. A broadened view is helpful for improving the current picture and thus cellulose derivatives and phenomena such as fiber dissolution, swelling, regeneration, plasticization and dispersion are considered. In addition to the matter of hydrogen bonding versus hydrophobic interactions, the role of ionization as well as some applications of new knowledge gained are highlighted.

show abstract

Section: -127mentioning

confidence: 48%

“…122 Additionally, the type of solvent and non-solvent strongly influences the properties (morphological and mechanical) of the regenerated cellulose material. 123 …”

Section: Cellulose Regeneration and Gelationmentioning

confidence: 99%

The relevance of structural features of cellulose and its interactions to dissolution, regeneration, gelation and plasticization phenomena

Lindman

Medronho

Alves

et al. 2017

Phys. Chem. Chem. Phys.

195

109

View full text Add to dashboard Cite

show abstract

“…In addition, we previously proposed a mechanism for structural formation of cellulose II from a cellulose/ aqueous system using MD simulations (Miyamoto et al 2009). Isobe et al (2012) experimentally proved that the sheets as the initial structure appeared from the solution. Medronho and Lindman have discussed that the hydrophobic interaction plays a very important role in cellulose solubility (Medronho et al 2012;Lindman et al 2010;Medronho and Lindman 2014a, b).…”

Section: Resultsmentioning

confidence: 96%

“…The existence of the molecular sheet formed by hydrophobic interactions has been suggested experimentally by many studies (Hayashi et al 1974;Hermans and Weidinger 1948;Hermans 1949;Isobe et al 2012;Medronho et al 2012;Lindman et al 2010;Medronho and Lindman 2014a, b). From these reports, it turns out that the molecular sheet structure associated by hydrophobic interactions is a basic feature of regenerated cellulose.…”

Section: Introductionmentioning

confidence: 88%

Molecular dynamics simulation of dehydration in cellulose/water crystals

2015

View full text Add to dashboard Cite

It is well known that there are two crystal types for a cellulose/water complex: Na-cellulose IV and cellulose II hydrate. The water molecules in these crystals are released with increasing temperature and the hydrated models are then transformed into cellulose II crystals. Dehydration can be observed even when the cellulose/water crystal is soaked in water. In this study, we investigated the dehydration process in Na-cellulose IV and cellulose II hydrate using molecular dynamics simulations. In both crystals, as simulation time progressed, the water molecules were gradually released from the crystal while forming hydrogen bonds with the hydroxyl groups of cellulose. Interestingly, water molecules were released from the spaces between the molecular sheets formed by hydrophobic interactions. All hydroxyl groups existed on the surface of the molecular sheets. Therefore, it is reasonable to suggest that water molecules pass between the sheets. For Na-cellulose IV, the ratio of gt conformations was high. In addition, it was observed that water molecules were in the space between O6 and O3 on each adjacent molecular sheet forming hydrogen bonds during simulation. On the other hand, the gg conformations were mainly observed in cellulose II hydrate probably because of the presence of the O6ÁÁÁO6 intermolecular hydrogen bond. During the simulation, the water molecules were present in the space between O2 and O3 while forming hydrogen bonds.

show abstract

“…Lina Zhang's group has been instrumental in investigating the effect of urea on cellulose solubility. Recently, an interesting study has been presented by Isobe et al (Isobe et al 2012) on the regeneration of cellulose, either using a coagulant or upon heating, in an aqueous alkali-urea solvent, following the process by time resolved synchrotron X-ray radiation. The authors suggested that when the medium surrounding the cellulose molecules becomes energetically unfavorable for molecular dispersion, regeneration starts and the initial process would consist in stacking the hydrophobic glucopyranoside rings (driven by hydrophobic interactions) to form monomolecular sheets, which then would line up by hydrogen bonding to form Na-cellulose IV type crystallites, a hydrate form of cellulose II.…”

Section: Cellulose Amphiphilicity and Hydrophobic Interactions: A Brimentioning

confidence: 99%

Probing cellulose amphiphilicity

Medronho

Duarte

Alves

et al. 2015

Nordic Pulp &Amp; Paper Research Journal

View full text Add to dashboard Cite

SUMMARY: Cellulose dissolution and regeneration is an increasingly active research field due to the direct relevance for numerous production processes and applications. The problem is not trivial since cellulose solvents are of remarkably different nature and thus the understanding of the subtle balance between the different interactions involved becomes difficult but crucial. There is a current discussion in literature on the balance between hydrogen bonding and hydrophobic interactions in controlling the solution behavior of cellulose. This treatise attempts to review recent work highlighting the marked amphiphilic characteristics of cellulose and role of hydrophobic interactions in dissolution and regeneration. Additionally, a few examples of our own research are discussed focusing on the role of different additives in cellulose solubility. The data does support the amphiphilic behavior of cellulose, which clearly should not be neglected when developing new solvents and strategies for cellulose dissolution and regeneration. ADDRESSES OF THE AUTHORS

show abstract

Mechanism of cellulose gelation from aqueous alkali-urea solution

Cited by 97 publications

References 23 publications

The relevance of structural features of cellulose and its interactions to dissolution, regeneration, gelation and plasticization phenomena

The relevance of structural features of cellulose and its interactions to dissolution, regeneration, gelation and plasticization phenomena

Molecular dynamics simulation of dehydration in cellulose/water crystals

Probing cellulose amphiphilicity

Contact Info

Product

Resources

About