Karapanagiotis Ioannis, Manoudis Panagiotis N, Zurba Andreea, Lampakis Dimitrios
Department of Management and Conservation of Ecclesiastical Cultural Heritage Objects, University Ecclesiastical Academy of Thessaloniki , Thessaloniki 54250, Greece.
Langmuir. 2014 Nov 11;30(44):13235-43. doi: 10.1021/la503583c. Epub 2014 Oct 29.
The cross-influence effects of treatment temperature and time on the wettability of a siloxane elastomer is investigated in detail, through static and tilt contact angle measurements. The material is heated at 400, 500, 600, 650, 700, and 800 °C for various periods, ranging from 1 to 300 s. The siloxane surface is subjected to multiple wettability transitions with treatment time: from intrinsic hydrophobicity to superhydrophobicity (and water repellency) and then through intermediate stages (hydrophobicity and hydrophilicity) to superhydrophilicity. For the time scale used herein (1-300 s), this scenario is recorded for treatment at 650, 700, and 800 °C. For treatment at lower temperatures (400, 500, and 600 °C) only the first transition, from intrinsic hydrophobicity to superhydrophobicity, is recorded. Scanning electron microscopy, micro-Fourier transform infrared (micro-FTIR), and micro-Raman spectroscopies are employed to correlate the aforementioned wettability transitions with structural and chemical changes of the siloxane surface, developed during thermal treatment. It is shown that the first transition from intrinsic hydrophobicity to superhydrophobicity is accompanied by a severe surface-structure evolution that increases surface roughness. Once superhydrophobicity is achieved, the surface structure reaches a saturation point and it is not subjected to any other change with further thermal treatment. FTIR spectroscopy shows that the intensity of the O-H/C-H peaks increases/decreases with treatment time, and Raman measurements show that the C-Si-C vibrations gradually disappear with treatment time. The evaporation of a droplet resting on a superhydrophobic, water-repellent siloxane surface, which was produced after appropriate thermal treatment, is monitored. It is shown that droplet evaporation initially follows the constant contact area mode. At later evaporation stages, a transition to the constant contact angle mode is recorded. Finally, it is demonstrated that the superhydrophobic and water-repellent siloxane surfaces exhibit self-cleaning properties, good durability, and furthermore do not practically affect the optical transparency of glass substrates.
通过静态和倾斜接触角测量，详细研究了处理温度和时间对硅氧烷弹性体润湿性的交叉影响。该材料在400、500、600、650、700和800℃下加热不同时间，范围从1到300秒。硅氧烷表面的润湿性随处理时间经历多次转变：从固有疏水性转变为超疏水性（及防水性），然后经过中间阶段（疏水性和亲水性）转变为超亲水性。对于本文所用的时间尺度（1 - 300秒），在650、700和800℃处理时记录到了这种情况。在较低温度（400、500和600℃）处理时，仅记录到了从固有疏水性到超疏水性的首次转变。采用扫描电子显微镜、微傅里叶变换红外光谱（micro - FTIR）和微拉曼光谱来关联上述润湿性转变与热处理过程中硅氧烷表面的结构和化学变化。结果表明，从固有疏水性到超疏水性的首次转变伴随着严重的表面结构演变，这增加了表面粗糙度。一旦实现超疏水性，表面结构达到饱和点，进一步热处理不会使其发生任何其他变化。FTIR光谱表明，O - H/C - H峰的强度随处理时间增加/减少，拉曼测量表明，C - Si - C振动随处理时间逐渐消失。监测了静置在经过适当热处理后产生的超疏水、防水硅氧烷表面上的液滴蒸发情况。结果表明，液滴蒸发最初遵循恒定接触面积模式。在后期蒸发阶段，记录到向恒定接触角模式的转变。最后，证明了超疏水和防水硅氧烷表面具有自清洁性能、良好的耐久性，并且实际上不会影响玻璃基板的光学透明度。
