Native cellulose is generally a mixture of two crystal phases, Ia and Ib. It is well known that processes, such as hydrothermal treatment, influence the relative proportion of these two phases. We have recently shown that sonication has a similar effect: sonicated celluloses are indeed enriched in Ib, Besides, they show a kinked morphology and their crystallinity is decreased.<br/>We have studied the process of kinking the crystals of native cellulose, initially pure in Ia and pure in Ib, by their hydrophobic surface by molecular dynamics simulation. A three-point bending causes a local amorphization of the structure at the kinking point while the two linear segments on both side remain highly organized but undergo locally and punctually longitudinal sliding of the hydrogen-bonded sheets. The magnitude of the sliding is 0.5 nm, which corresponds to the length of a glucose residue and thus to a local allomorphic transition. Even though Ia and Ib share the same stress relaxation mechanism, Ia accumulates such transitions with increasing kinking angle whereas in Ib these transitions are only transitory. We have established a common mechanism leading to both kinking and allomorphic transition.<br/>

Allomorphic transition in native cellulose promoted by ultrasounds

255th National Meeting (2018)

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