Department of Materials Science and Engineering , National University of Singapore , Singapore 117574 , Singapore.
Singapore Institute of Manufacturing Technology, Agency for Science, Technology, and Research (A*STAR) , 73 Nanyang Drive , Singapore 637662 , Singapore.
Langmuir. 2019 Jan 29;35(4):839-847. doi: 10.1021/acs.langmuir.8b03560. Epub 2019 Jan 15.
The antioil-fouling characteristic of an amorphous cellulose (a-cellulose) surface was elucidated using the sessile droplet method (static) and a modified Wilhelmy plate technique (dynamic). As compared to other hydrophilic surfaces (cellulose acetate, poly(vinyl alcohol), and glass), the oil (poly(dimethylsiloxane)) contact angle on the a-cellulose surface underwater shows the largest value (170.5 ± 5.0°), having the smallest deviation from its theoretical value (180.0°) as estimated by Young's equation. Also, the a-cellulose surface demonstrates the strongest affinity with water in an oil medium (stable hydrophilicity). Moreover, the work of adhesion between the receding oil phase and a-cellulose underwater is quantified to be 10.3 mN/m, approximately one-fourth of that in air (42.0 mN/m). The overall wetting study suggests a rather low oil/solid/water three-phase contact line (TPL) friction in the direction that water displaces oil. A proposed mechanism attributes these phenomena to the water-accessible rigid cellulose chains and supramolecular structure of a-cellulose. The former hinders molecular rearrangement during processing or upon exposure to oil, such that its polar hydroxyl groups are readily accessible to water, thereby retaining its hydrophilicity. The latter allows water to diffuse across the TPL, forming the hydration shells that weaken the van der Waals interactions between oil and cellulose chains. Such findings of the a-cellulose surface can be exploited to fabricate mesh membranes with high water permeation flux (375.4 ± 13.5 L m h Pa), high oil/water separation efficiency (93-98%), and long-lasting stability, which is suitable for offshore oil spill remediation.
使用固着液滴法（静态）和改进的吊片法（动态）阐明了无定形纤维素（a-纤维素）表面的抗油污特性。与其他亲水表面（醋酸纤维素、聚乙烯醇和玻璃）相比，a-纤维素表面在水下的油（聚二甲基硅氧烷）接触角显示出最大的值（170.5 ± 5.0°），与其理论值（180.0°）的偏差最小，这是由杨氏方程估计的。此外，a-纤维素表面在油介质中表现出与水的最强亲和力（稳定的亲水性）。此外，还定量测量了油相后退时与 a-纤维素在水下的粘附功为 10.3 mN/m，约为空气中的四分之一（42.0 mN/m）。总的润湿研究表明，在水驱油的方向上，油/固/水三相接触线（TPL）的摩擦力相当低。提出的机制将这些现象归因于可接触水的刚性纤维素链和 a-纤维素的超分子结构。前者阻碍了加工过程或暴露于油时的分子重排，使得其极性羟基基团易于接触水，从而保持其亲水性。后者允许水在 TPL 中扩散，形成水合壳，从而削弱油和纤维素链之间的范德华相互作用。这种 a-纤维素表面的发现可用于制造具有高水渗透通量（375.4 ± 13.5 L m h Pa）、高油水分离效率（93-98%）和持久稳定性的网孔膜，适用于海上溢油的修复。
