Preparation of Cellulose Nanocrystals: Controlling the Crystalline Type by One-Pot Acid Hydrolysis

Cellulose nanocrystals (CNCs) have aroused increas-ing interest owing to their renewable origin and excellent properties derived from their size and morphology. Based on their chain orientation, CNCs can be prepared as two main allomorphs (I or II). However, achieving pure CNC allomorphs still requires enhanced control on the CNCs synthesis process and improved understanding of the involved reaction parameters. In this work, we study in detail a set of parameters for CNC synthesis using one-pot acid hydrolysis and evaluate their influence on the outcome with respect to yield, purity, and repeatability. We also demonstrate that a fast, nondestructive, and accurate methodology based on dynamic light scattering is an efficient alternative to the usual structural analysis of the synthesis outcome. Finally, we provide an improved protocol to reliably obtain each allomorph with mass yields of 25% for type I and 40% for type II. Emphasis is put on the reduction of the environmental impact and the overall preparation time.

Automated summary

In this study, we examined a set of parameters for cellulose nanocrystal synthesis using one-pot acid hydrolysis and assessed their impact on yield, purity, and repeatability. We also demonstrated the feasibility of using dynamic light scattering as a nondestructive and accurate method for analyzing the synthesis outcome. Ultimately, we developed an improved protocol to obtain each allomorph with mass yields of 25% for type I and 40% for type II, with emphasis on reducing environmental impact and overall preparation time.