Although the rheology of cellulose nanocrystalline (CNC) suspensions has been widely studied, less attention has been paid to the modified cellulose nanocrystals such as cationic and anionic cellulose hydrogels. In this work, the rheological behavior of cellulose nanocrystals (CNCs), anionic CNCs (pCNCs), and cationic CNCs (nCNCs), was comparatively studied. The rheological behavior demonstrated that the nCNC and pCNC form hydrogen bonding, which significantly contributes to the increase in the gel strengths in the sonicated state. The formation of such structures between individual fibers prevents flocculation due to the increased suspension stability. In addition, the extensive formation of hydrogen bonding in the case of nCNC compared to that of pCNC explains its enhanced rheological properties. The effect of pre-shear has been studied in detail for these systems by considering a combination of pre-shear and startup of steady shear in different shearing directions with certain rest/recovery time in between to eliminate strain history and thus eliminate the possible bias of pre-shearing on structure formation.

中文翻译：

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阳离子和阴离子纤维素纳米晶体（CNC）水凝胶：流变学研究

尽管已经对纤维素纳米晶体（CNC）悬浮液的流变学进行了广泛研究，但对改性纤维素纳米晶体（如阳离子和阴离子纤维素水凝胶）的关注却很少。在这项工作中，对纤维素纳米晶体（CNCs），阴离子CNCs（pCNCs）和阳离子CNCs（nCNCs）的流变行为进行了比较研究。流变行为表明，nCNC和pCNC形成氢键，这在超声处理后显着促进了凝胶强度的提高。由于增加的悬浮液稳定性，在单根纤维之间形成这种结构可防止絮凝。另外，与pCNC相比，nCNC形成氢键的原因广泛，这说明其流变性得到增强。