具有特殊浸润性的二氧化硅功能表面的制备与研究

【作者】 刘湘梅；

【导师】 贺军辉；

【作者基本信息】 中国科学院研究生院（理化技术研究所） ， 有机化学， 2009， 博士

【摘要】 透明材料(如玻璃、塑料)在工农业生产和日常生活以及军事领域中有着广泛的用途,例如护目镜、激光防护镜、望远镜及各种摄像设备的镜头、机械观察窗、运动潜水镜、浴室玻璃及镜子、车辆挡风玻璃及后视镜、头盔、太阳能电池板、测量仪器的观察窗、温室的玻璃墙等等。然而雾化问题给人们的生产和生活带来了诸多的不便,甚至造成了重大的损失。防雾技术与防雾材料的研究与开发倍受科学界和企业界的关注。目前所研究的防雾表面按其作用机理分为三种:第一种是利用具有光催化性能的物质,如二氧化钛及氧化锌,它们受紫外光或可见光的辐照后,具有超亲水的性能;第二种方法是制备含高分子或者含表面活性剂的涂料;第三种方法是通过制备特殊结构使材料表面具有超亲水或者超疏水性能。本论文第一章从原理介绍和发展状况两方面分别介绍了防雾材料和抗反射材料。总的来说,制备方法简单、原料成本低廉、具有优异的耐磨性、粘结性、透明性和持久性的防雾表面,是研究者们的一直努力方向。本论文正是基于以上思路,以无需光照的防雾涂层作为导向,采用较低的反射率、较高的光透过率、较好的亲水性以及很好的耐磨性能的二氧化硅材料,设计并制备出几种性能良好的功能性涂层(包括防雾涂层、超亲水增透涂层以及高接触角低滚动角的超疏水涂层),具体研究内容和结果如下:1.以聚电解质为媒介,通过静电组装技术把小尺寸的二氧化硅纳米粒子组装到大尺寸的二氧化硅纳米粒子表面,制备出类覆盆子结构的复合粒子。再通过静电组装把该复合粒子组装到沉积有聚电解质的玻璃片上,得到具有阶层粗糙表面结构的涂层,再经过煅烧提高涂层的机械强度以及涂层与玻璃表面的粘附力。我们用扫描电镜,透射电镜观察了粒子及其涂层的微观结构,用接触角仪测量了水滴与涂层的接触角及其铺展速度,并且详细讨论了表面结构与表面性能的关系。实验结果表明,该涂层结合了二氧化硅本身的高亲水性能和所制备的阶层粗糙结构的高比表面积,所设计的阶层粗糙结构达到了预期的超亲水效果,并实现了无需光照的超亲水防雾性能。2.与实心的类覆盆子二氧化硅复合粒子涂层相比,空心的二氧化硅纳米粒子涂层由于表面的毛细管作用,水滴在其表面应该具有更快的铺展速度,同时由于空心球表面是纳米尺寸的粒子,涂层的透光率应该有所提高,因此我们设计并制备了空心球涂层。首先用层状自组装方法制备出聚苯乙烯球核/二氧化硅纳米粒子壳的类覆盆子结构的有机/无机复合粒子,然后把该复合粒子组装到沉积有聚电解质的玻璃基片上,再经过煅烧去除聚苯乙烯球核以及聚电解质,得到具有阶层粗糙结构和阶层孔结构的空心球涂层。我们通过扫描电镜和透射电镜观察了有机/无机复合粒子、二氧化硅空心球以及空心球涂层的微观结构,用接触角仪测量了该涂层的接触角以及铺展速度,并测量了其防雾效果。实验结果表明,该涂层有很好的超亲水性,尤其是水滴在其表面铺展到接近0o所需的时间小于33 ms,具有很好的防雾性能。3.超亲水防雾材料表面的浸润性是很重要的影响因素,同时透光率是很关键的因素。我们用层状自组装结合煅烧方法制备出不同尺寸的二氧化硅粒子夹心涂层。水滴在煅烧后的(PDDA/S-150)3/(PDDA/S-30)2涂层表面铺展到接触角接近0o所需的最短时间大约为0.28 s,实现了超亲水性能;而涂层(PDDA/S-30)8的最大透光率达到98.5%,大大高于普通玻璃的透光率(91.3%),达到了增透的效果。我们对涂层的超亲水以及增透性能的影响因素如沉积层数,粒子尺寸,表面粗糙度等进行了系统研究。通过对实验条件的优化,我们制备出既具有超亲水性能又具有增透性能的(PDDA/S-30)8/(PDDA/S-150)2/(PDDA/S-30)2涂层,其最大透光率达到97.1%,而铺展到接近0o所需要的时间<0.5 s。同时我们对S-30(30 nm的二氧化硅纳米粒子)和S-150(150 nm的二氧化硅纳米粒子)在涂层中所起的作用分别进行了讨论。4.在本论文的第五章中,我们以普通玻璃片为原料,用一步水热法制备出了具有阶层粗糙结构的表面。表面形貌从网状结构、花状结构到刺球状结构可以通过对反应温度和反应时间的调控来控制。直接制备出的表面干燥后显示出超亲水性,接触角接近0o,当经过氟硅烷表面处理之后,表面显示出超疏水性,接触角高达160o,滚动角低至1o。另外,在文中我们对其形成机理也进行了详细的讨论,该方法操作简单,原料廉价,无论从操作上还是成本上都具有很大的优越性。更多还原

【Abstract】 Transparent materials have important applications, including mirrors, glasses, goggles, laser safety eye protective lenses, face masks, windows for vehicles, and solar cells. However, fogging usually occurs when their surface temperature is lower than that of their air surrounding, which has caused serious influences in industry and our daily life, and antifogging coatings have been attracting much attention of scientists and investors.To date, several approaches have been developed to prepare antifogging coatings. The first involves the use of photochemically active materials such as TiO2 or ZnO that become superhydrophilic after exposure to UV, or after suitable chemical modifications and exposure to visible radiation. The second involves spraying an appropriate surfactant or polymer solution to lower the surface energy. The third case is the use of rough surfaces to fabricate superhydrophilic (water droplet contact angle <5°within 0.5 s or less )or superhydrophobic (water droplet contact angle >150°and low contact angle hysteresis ) surfaces. The theory and development of anti-fogging and antireflective materials have been reviewed in chapter 1. In a word, antifogging coatings with good mechanical durability, transmittance, and stability have been attracting much attention.In this work, we have designed and fabricated several functional coatings based on silica with low reflectivity, good hydrophilicity and good mechanical durability. The functional coatings include antifogging coatings, superhydrophilic and antireflective coatings, and superhydrophobic coatings with high contact angle and low sliding angle. The main works are listed as follows:1. Raspberry-like silica nanospheres were prepared by electrostatic self-assembly of polyelectrolytes and monodisperse silica nanoparticles of two different sizes, and their coatings were fabricated via layer-by-layer assembly with polyelectrolytes and following calcination. The morphology of the raspberry-like silica nanospheres and their coatings were observed by scanning and transmission electron microscopies. The surface properties of these coatings were investigated by measuring their water contact angles, and the results showed that such hierarchically structured coatings had unique superhydrophilic and antifogging properties. Finally, the formation mechanism and the property–structure relationship were discussed in details.2. Raspberry-like organic/inorganic composite spheres are prepared by stepwise electrostatic assembly of polyelectrolytes and silica nanoparticles onto monodisperse polystyrene spheres. Hierarchically structured porous films of silica hollow spheres are fabricated from these composite spheres by layer-by-layer assembly with polyelectrolytes followed by calcination. The morphologies of the raspberry-like organic/inorganic composite spheres and the derived hierarchically structured porous films are observed by scanning and transmission electron microscopies. The surface properties of these films are investigated by measuring their water contact angles, water-spreading speeds, and antifogging properties. The results show that such hierarchically structured porous films of silica hollow spheres have unique superhydrophilic and antifogging properties. Finally, the formation mechanism of these nanostructures and property–structure relationships are discussed in detail on the basis of experimental observations.3. Superhydrophilic and antireflective coatings were fabricated from silica nanoparticles of 30 nm (S-30), 150 nm (S-150) and polyelectrolytes of poly(diallyldimethylammonium) chloride (PDDA) and sodium poly(4- styrenesulfonate) (PSS) via layer-by-layer assembly and post-calcination. The time for a droplet to spread flat decreases to as short as 0.28 s by applying a coating of (PDDA/S-150)3/ (PDDA/S-30)2 while the maximum transmittance reaches as high as 98.5% by applying a coating of (PDDA/S-30)8. Factors that affect the superhydrophilic and antireflective properties of coatings, such as the number of deposition cycles, size of nanoparticles and surface roughness, were investigated in details by observing their surface morphologies and by measuring their water contact angles, water spreading time and transmittances. Systematic investigation gave an optimal structure of calcinated (PDDA/S-30)8/(PDDA/S-150)2/(PDDA/S-30)2 for the superhydrophilic and antireflective coating. Its maximum transmittance and the time for a droplet to spread flat reached 97.1% and <0.5 s, respectively, indicating that both antireflective and superhydrophilic properties were achieved by a single coating. Finally, the roles of S-30 and S-150 nanoparticles in enhancing the superhydrophilic and antireflective properties were discussed.4. Hierarchically structured coatings were fabricated on glass substrates by one-step hydrothermal method. The surfaces of the coatings are rough, and are composed of flower-like particles assembled by nanoflakes or urchin-like particles constructed by nanowires. These rough surfaces exhibit superhydrophilicity, their water contact angles reaching 0o in less than 40 ms. After surface modification by 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane, the wetting properties of these coatings switch from superhydrophilicity to superhydrophobicity, with water contact angles as high as 160o and slide angle as low as 1o. The formation mechanism of the hierarchically structured coatings is discussed in details on the basis of experimental results.更多还原