| 摘要: | 本研究採用四種方法實施疏水薄膜材料之製備研究，藉由製造表面粗糙度與表面疏水官能基之披覆以達到疏水的特性。首先以氟素高分子與二氧化矽的前驅物在溶劑中進行溶凝膠反應。藉著氟素高分子提供疏水官能基，並利用溶凝膠法在高分子中成長形成二氧化矽粒子以製造表面粗糙度。其中所使用的氟素高分子聚二氟乙烯(PVDF)可溶於溶劑中，因此可適用於溶凝膠反應；然而，因水與高分子間之不互溶性，水量無法加入太多，太多的水會造成氟素高分子在溶劑中相分離。此外前驅物太多會使塗層材料變脆，甚至無法成膜。以此方法所製得到之塗層表面粗糙度較小，因此接觸角維持在90度左右。其中，以溶凝膠法所形成之二氧化矽應具有相當多親水性之氫氧基，可是以FTIR觀察並未發現氫氧基，可能是二氧化矽粒子受到PVDF之披覆且受限於TEOS之添加量較少，使得薄膜中所形成的二氧化矽粒子較少，因此所得到的薄膜材料依然具有疏水特性。 為了增加二氧化矽在氟素高分子的比例，以增加表面粗糙度，改採用第二種方法，以二氧化矽粉末與氟素高分子混合。在此章研究中，分別使用兩種氟素高分子PVDF與四氟乙烯-六氟丙烯共聚物(FEP)和兩種尺寸(5微米與310奈米)之二氧化矽粒子混合，並將其塗佈於玻璃基材表面。量測水滴對塗層材料表面的接觸角，並以SEM觀察塗層的表面型態。實驗結果發現以奈米尺寸的二氧化矽粉體添加於PVDF中，利用奈米二氧化矽所堆積形成的表面粗糙度，可提升表面接觸角至110度左右；以奈米尺寸的二氧化矽粉體添加於FEP高分子中，利用奈米二氧化矽堆積形成的表面粗糙度，搭配FEP全氟之疏水特性，甚至可得到更高的表面接觸角134度。 本研究中所採用的第三種製備疏水薄膜的方法，即在PVDF之中分別加入PPG或PEG製膜，並以溶劑將PPG或PEG移除，在PVDF薄膜表面會留下孔洞，藉此增加PVDF的表面粗糙度，以提升PVDF的表面接觸角。實驗結果顯示PVDF表面接觸角會隨PPG與PEG的加入有所增加。但是當PEG/PVDF或PPG/PVDF?0.5時，會有相反轉現象。當PPG/PVDF=0.4時，PVDF有最大表面接觸角度123度；然而當PPG/PVDF?0.5產生相反轉時，因表面粗糙度下降，接觸角會大幅下降。在PEG/PVDF的系統中，相反轉時，因有藕斷絲連之結構可提供表面粗糙度，所以接觸角會繼續上升；而在PPG/PVDF的系統中，可能因為丙酮在室溫下會些微融解PVDF，破壞了相反轉形成之藕斷絲連結構，所以接觸角會大幅下降。 本研究所使用的第四種方法即採用兩步驟溶凝膠法製作具有粗糙表面之塗層，再以三甲基氯烷(TMCS)將表面改質。利用兩步驟的溶凝膠法控制生成的二氧化矽粒子之尺寸，藉著不同尺寸的二氧化矽粒子的聚集，可形成不同的表面粗糙度，並得到不同的接觸角結果。在兩步驟的溶凝膠製程，當第一步驟中的水量增加時，因為在酸性環境下，水參與水解反應產生較多的silanol，ts與tg會隨之下降。當較多的酸加入反應時，會加快反應速率，而生成的粒子透過聚集與縮合可形成粗糙的表面，使接觸角增大。當氨水的添加量增加時，反應速率會增加，使ts與tg下降。當TEOS：Ra：R：HCl為 1：0.5：3.5：3.36x10-4，且NH4OH/HCl大於5.6時，溶液中會有大的粒子生成，這些大粒子經過聚集與縮合反應可製成粗糙表面，而表面接觸角可大於140 o。當TEOS：Ra：HCl為 1：0.5：3.36x10-4，R值控制在2.9以上，塗層材料的表面接觸角幾乎都大於140o。在本研究中，實驗所得到最好的結果可達到超疏水，表面接觸角為150度。 In this study, four methods were applied to make hydrophobic films. First, the coating materials were made by the combination of PVDF and sol-gel processes. Since PVDF could be dissolved in the solvent, it was the better choice for the hydrophobic hybrid materials, which were made by the combination of fluoropolymer and sol-gel process. However, in this process, only a little water could be added. Too much water would result in phase separation. And too much precursor added would result in brittleness of coating materials. For there was not a lot of TEOS added, the roughness of the coating materials could not be increased, therefore the contact angles of the surface of the materials did not increase. However, the hydrophilic silica did not decrease the contact angle of the films, due to less silica formed in the films and the surface of silica covered by PVDF. Besides, to increase the content of silica in PVDF, silica powder was mixed with the fluropolymer. The surface roughness was formed by aggregation of silica to promote the hydrophobia of fluoropolymer. Since FEP had better hydrophobia, it was a better choice than PVDF. The contact angles of the surface of the SiO2/FEP film can be 134o. But the content of silica was limited. The size of silica was submicron. Too much silica would make the blending difficult. The third method is to add PPG or PEG into PVDF solutions to make membranes. After the PPG or PEG were removed from the membranes, there were holes left on the membranes. It increased the roughness of the surfaces of the membranes. The contact angles of the membranes could be 123 degree. When PEG/PVDF or PPG/PVDF?0.5, there was phase inversion occurred. As PEG/PVDF ? 0.5, the contact angles of the films still increased. There was web structure left in the films to provide roughness. When PPG/PVDF?0.5, the contact angles went down, due to the web being destroyed by acetone. In this study, the last method, the two-step sol–gel process was used to prepare hydrophobic coating films on the glass substrates. The first step was to add hydrogen chloride into TEOS (tetraethoxysilane) solution, and then the second step was to add ammonia into the above reacted solution. We adopted different amount of hydrogen chloride and ammonia to control the sol–gel reaction and observed the change of the viscosity, gelatin period of the solution and contact angles of the coating films. By this method, we created a surface with roughness and then the hydroxyl groups were terminated by adding trimethylchlorosilane (TMCS) to produce a hydrophobic coating layer. The amount of the acid, base and water added in the solution influenced the reaction rate and resulted in the aggregation and condensation of the particles to form rough surfaces. Consequently, the rough surfaces made by aggregation and condensation of the large particles, which were modified by TMCS resulted in higher contact angles (>140o). In this study, a surface with contact angle 150o was obtained. |
