A comparative molecular dynamics study of crystalline, paracrystalline and amorphous states of cellulose

Abstract

The quintessential form of cellulose in wood consists of microfibrils that have high aspect ratio crystalline domains embedded within an amorphous cellulose domain. In this study, we apply unitedatom molecular dynamics simulations to quantify changes in different morphologies of cellulose. We compare the structure of crystalline cellulose with paracrystalline and amorphous phases that are both obtained by high temperature equilibration followed by quenching at room temperature. Our study reveals that the paracrystalline phase may be an intermediate, kinetically arrested phase formed upon amorphisation of crystalline cellulose. The quenched structures yield isotropic amorphous polymer domains consistent with experimental results, thereby validating a new computational protocol for achieving amorphous cellulose structure. The non-crystalline cellulose compared to crystalline structure is characterized by a dramatic decrease in elastic modulus, thermal expansion coefficient, bond energies, and number of hydrogen bonds. Analysis of the lattice parameters shows that Ib cellulose undergoes a phase transition into hightemperature phase in the range of 450-550 K. The mechanisms of the phase transition elucidated here present an atomistic view of the temperature dependent dynamic structure and mechanical properties of cellulose. The paracrystalline state of cellulose exhibits intermediate mechanical properties, between crystalline and amorphous phases, that can be assigned to the physical properties of the interphase regions between crystalline and amorphous cellulose in wood microfibrils. Our results suggest an atomistic structural view of amorphous cellulose which is consistent with Electronic supplementary material The online version of this article (

A comprehensive review on pre-treatment strategy for lignocellulosic food industry waste: Challenges and opportunities

“…polymorphs II, III and IV. Cellulose also exists in amorphous form which is soluble and can be easily digested by enzymes (Kulasinski, Keten, Churakov, Derome, & Carmeliet, 2014).…”

Traction–separation laws and stick–slip shear phenomenon of interfaces between cellulose nanocrystals

“…Through a combination of computational (Dri et al, 2013;Kulasinski et al, 2014;Sinko et al, 2014;Wu et al, 2013) and experimental (Kong and Eichhorn, 2005;Lindman et al, 2010;Nishiyama et al, 2002;Tashiro and Kobayashi, 1991) studies, it has been established that both hydrogen bonding and secondary van der Waals interactions play a crucial role in determining the emergent macroscale properties of these crystals. For Iβ cellulose, commonly called "natural" cellulose, it has been shown that hydrogen bonding is dominant along the (110) plane while van der Waals interactions are dominant along the (200) plane (Sinko et al, 2014), with these planes indicated in Figure 1A.…”

“…Smaller nanocrystals exhibit lower fracture surface energy, whereas larger crystals have reduced surface area to volume ratio, making this intermediate length-scale optimal for nanocomposites. While a number of recent studies have characterized the elastic and fracture properties of crystalline cellulose at the molecular level (Eichhorn and Davies, 2006;Kulasinski et al, 2014;Matthews et al, 2006;Sinko et al, 2014), the focus has been on the axial and transverse tensile properties of individual CNCs. Much less is known about interfaces between multiple CNCs, or shear failure of CNCs under various loading scenarios relevant to nanocomposites and neat films (Chen et al, 2009;Cox, 1952;Gao and Li, 2005).…”

Not Just Lumber—Using Wood in the Sustainable Future of Materials, Chemicals, and Fuels

“…For example, united-atom MD simulations were used to quantify changes in different morphologies of cellulose to reveal that the semicrystalline phase may be an intermediate, kinetically arrested phase formed at amorphous cellulose formation. 73 MD simulation showed in Ib crystalline cellulose that elastic modulus, Poisson's ratio, yield stress and strain, and ultimate stress and strain are highly anisotropic, and that although properties that describe elastic behavior of the material are independent of strain rate, yield and ultimate properties increase with increasing strain rate. 74 In another MD study, 75 the fracture energy of crystalline cellulose was found to depend on crystal width, due to edge defects that significantly reduce the fracture energy of small crystals but have a negligible effect beyond a critical width.…”