Dong Fangyuan, Zhang Mi, Tang Wai-Wa, Wang Yi
†Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Hum, Kowloon, Hong Kong SAR.
‡Food Safety and Technology Research Center, Hong Kong PolyU Shenzhen Research Institute, Shenzhen, PR China.
J Phys Chem B. 2015 Apr 23;119(16):5321-7. doi: 10.1021/acs.jpcb.5b00011. Epub 2015 Apr 9.
Superhydrophobic/hydrophobic surfaces have attracted wide attention because of their broad applications in various regions, including coating, textile, packaging, electronic devices, and bioengineering. Many studies have been focused on the fabrication of superhydrophobic/hydrophobic surfaces using natural materials. In this paper, superhydrophobic/hydrophobic surfaces were formed by an amphiphilic natural protein, zein, using electrospinning. Water contact angle (WCA) and scanning electron microscopy (SEM) were used to characterize the hydrophobicity and surface morphology of the electrospun structures. The highest WCA of the zein electrospun surfaces could reach 155.5 ± 1.4°. To further understand the mechanism of superhydrophobic surface formation from amphiphiles using electrospinning, a synthetic amphiphilic polymer was selected, and also, a method similar to electrospinning, spray drying, was tried. The electrospun amphiphilic polymer surface showed a high hydrophobicity with a WCA of 141.4 ± 0.7°. WCA of the spray-dried zein surface could reach 125.3 ± 2.1°. The secondary structures of the zein in the electrospun film and cast-dried film were studied using ATR-FTIR, showing that α-helix to β-sheet transformation happened during the solvent evaporation in the cast drying process but not in the electrospinning process. A formation mechanism was proposed on the basis of the orientation of the amphiphiles during the solvent evaporation of different fabrication methods. The droplet-based or jet-based evaporation during electrospinning and spray drying led to the formation of the superhydrophobic/hydrophobic surface by the accumulation of the hydrophobic groups of the amphiphiles on the surface, while the surface-based evaporation during cast drying led to the formation of the hydrophilic surface by the accumulation of the hydrophilic groups of the amphiphiles on the surface.
超疏水/疏水表面因其在涂层、纺织、包装、电子设备和生物工程等各个领域的广泛应用而备受关注。许多研究都集中在使用天然材料制备超疏水/疏水表面上。在本文中，通过两亲性天然蛋白质玉米醇溶蛋白，利用静电纺丝法制备了超疏水/疏水表面。采用水接触角（WCA）和扫描电子显微镜（SEM）对静电纺丝结构的疏水性和表面形貌进行了表征。玉米醇溶蛋白静电纺丝表面的最高水接触角可达155.5±1.4°。为了进一步了解使用静电纺丝法由两亲物形成超疏水表面的机理，选择了一种合成两亲性聚合物，并且还尝试了一种类似于静电纺丝的方法——喷雾干燥。静电纺丝两亲性聚合物表面表现出高疏水性，水接触角为141.4±0.7°。喷雾干燥玉米醇溶蛋白表面的水接触角可达125.3±2.1°。利用衰减全反射傅里叶变换红外光谱（ATR-FTIR）研究了静电纺丝膜和流延干燥膜中玉米醇溶蛋白的二级结构，结果表明，在流延干燥过程中的溶剂蒸发过程中发生了α-螺旋向β-折叠的转变，而在静电纺丝过程中未发生这种转变。基于不同制备方法的溶剂蒸发过程中两亲物的取向，提出了一种形成机理。静电纺丝和喷雾干燥过程中基于液滴或射流的蒸发导致两亲物疏水基团在表面堆积，从而形成超疏水/疏水表面，而流延干燥过程中基于表面的蒸发导致两亲物亲水基团在表面堆积，从而形成亲水表面。
