Polarities-Induced Weakening of Molecular Interaction and Formation of Nanocellulose with Different Dimensions

Additives with different polarities were used in the fabrication of nanocellulose by ball-milling. It was found that the dimension of cellulose nanomaterials could be controlled by the additive polarity. Because there are hydrophilic and hydrophobic crystal planes, additives with different polarities may permeate into the interface between the crystal planes with different additive hydrophilicities. It was suggested that the polar additive molecules could migrate into the interface between the hydrophilic crystalline faces (110 and 11̅0) and weaken the hydrogen bonding interaction during milling, which results in slippage and peeling along the 110 and 11̅0 planes and eventually allows one dimensional cellulose nanofibers. On the other hand, nonpolar and medium-polar additive molecules can only permeate into the interface between the hydrophobic crystalline face (200 plane) and weaken the hydrophobic interaction during milling, which results in the slippage and peeling along 200 planes and the formation of two dimensional cellulose nanosheets. The results of this study may facilitate the regulated and controllable fabrication of micro-/nanocellulose with different morphologies and dimensions.

本研究在通过球磨法（ball-milling）制备纳米纤维素（nanocellulose）时，使用了不同极性的添加剂。研究发现，纤维素纳米材料的尺寸可通过添加剂的极性进行调控。由于纤维素存在亲水与疏水晶面，不同极性的添加剂可渗透至与自身亲疏水性匹配的晶面界面之间。研究表明，极性添加剂分子可在球磨过程中迁移至亲水晶面（110与11̅0）的界面处，削弱该处的氢键相互作用，进而引发沿110和11̅0晶面的滑移与剥离，最终生成一维纤维素纳米纤维。另一方面，非极性与中极性添加剂分子仅能渗透至疏水晶面（200晶面）的界面处，在球磨过程中削弱该处的疏水相互作用，进而引发沿200晶面的滑移与剥离，最终形成二维纤维素纳米片。本研究结果可为不同形貌与尺寸的微/纳米纤维素的可调控制备提供助力。