基于含氟改性籠狀倍半硅氧烷一步法制備透明超疏水涂層

徐亞洲，何瑾馨,b，朱衛彪，董霞,c，趙強強,b

基于含氟改性籠狀倍半硅氧烷一步法制備透明超疏水涂層

徐亞洲a，何瑾馨a,b，朱衛彪a，董霞a,c，趙強強a,b

（東華大學 a.化學化工與生物工程學院 b.紡織面料技術教育部重點實驗室 c.國家染整工程技術研究中心，上海 201620）

為了研究出一種在光滑鏡面基材上大面積制備透明耐用的超疏水涂層，需要克服當前超疏水涂層存在的理化穩定性差、光學透明度不高以及制備繁瑣、難以大面積實施等問題。通過向聚氨酯丙烯酸酯疏水性光固化樹脂體系中引入含氟低表面能改性的籠狀倍半硅氧烷（POSS），結合噴涂法和相分離法在聚碳酸酯（PC）表面制備了一種超疏水光固化涂層。探究了低表面能改性POSS的摻雜量和乙醇添加量對構筑超疏水涂層的影響。當POSS-SH-DFMA7的摻雜量為樹脂含量的40%、乙醇的添加量為溶劑THF的25%時，涂層表現出優異的超疏水特性，靜態水接觸角和滑動角分別可達到156.92°和3.24°；良好的光學透明性，光線透過率為85.63%；可靠的機械穩定性，承受6 h的水滴沖擊后依然保持超疏水特性；穩定的耐候和耐化學性，經歷戶外環境和不同pH值化學試劑的侵蝕后仍可保持涂層原有的潤濕性能。在光固化樹脂體系中引入一定量的含氟單體改性POSS結合乙醇的作用可以一步法制備出透明、理化性能穩定的超疏水涂層。

POSS；超疏水涂層；透明；耐用；噴涂；相分離；紫外光固化

超疏水表面因為自身獨特的潤濕性能，已經在越來越多的領域得到廣泛應用，如防污自清潔[1-2]、減阻[3-4]、防覆冰[5-6]、油/水分離[7-8]等。最早科學家們受自然界中“荷葉效應”[9]的啟發，于2002年首次提出了呈現這種大接觸角和低附著力是由于表面微納復合結構協同作用的觀點，為之后超疏水表面的模型構建提供了理論基礎。目前，制備超疏水表面的構筑方法主要分為兩大類——自上而下[10]和自下而上[11]，自上而下法包括模板法[12]、等離子體刻蝕法[13]、印刷法[14]等，自下而上法包括化學沉積法[15]、相分離法[16]、溶膠-凝膠法[17]、噴涂法[18]等。雖然方法紛雜多樣，但構造原理都是從降低表面能和提高表面粗糙度這2個角度出發。

近些年來，隨著超疏水技術在人們生產生活中扮演的角色愈發重要，涂層技術的研究一直在不斷革新，從對超疏水基礎結構的研究發展到將功能化納米粒子低牢度化附著于表面，再到超疏水成分與整體涂層形成均一穩定的連結體系。雖然很多研究已經在超疏水表面的創新性構造方面取得了重大進步，但是真正能規模化生產的產品卻少之又少。現階段，構筑超疏水表面能常使用的低表面能材料主要為長鏈全氟硅烷[19]、含氟丙烯酸酯[20]和氟硅共聚物[21]，結合納米粒子的添加形成低表面能的粗糙化表面。但是如何提升納米粒子與聚合物的有效鍵合，以及如何改善改性納米粒子與基材表面的穩定黏附與耐久性始終是一個難點。而且對于一些透明[22]、光滑的基材，如何在不影響透光率的基礎上使其具備良好的各項應用性能，是目前透明超疏水涂層領域的一大難題。

為了解決以上問題，本研究采用籠狀低聚倍半硅氧烷（POSS[23]）作為粗糙度構建的納米材料，因為其本身天然的尺度優勢（2～5 nm）以及獨特的分子內化結構，8個頂點處的Si原子可以通過化學反應連接各種反應性或非反應性基團。因此可以通過巰基-烯點擊化學反應[24]將含氟單體引入到POSS中，得到的產物不僅具備低表面能特性，還可以參與多層次粗糙結構的構建。另外，由于POSS本身具備良好的溶解性、尺寸穩定性和熱穩定性等優點，涂層的各項應用性能會隨著POSS的加入得到顯著提升。所以本研究采取將改性納米POSS與光固化樹脂[25]（成膜速度快，與基材附著力強）混合，采用一步噴涂法結合相分離法，在聚碳酸酯[26]表面制備出了操作簡便、可大規模實施的超疏水涂層。該涂層在不影響基材本身光學透明性的同時還具備良好的機械和化學穩定性。該研究可以為超疏水涂層的大面積生產以及在透明光學領域的大范圍應用提供參考。

1 試驗

1.1 八乙烯基POSS的疏水改性

1.1.1 八乙烯基POSS的巰基化

在吳城峰等[27]提出的POSS-SH8合成方法的研究基礎上，先對八乙烯基POSS進行巰基化處理，得到了POSS-SH8。然后利用巰基-烯點擊反應對POSS- SH8進行氟烷基改性。

1.1.2 巰基POSS的氟烷基化

A液：將5.6 g甲基丙烯酸十二氟庚酯（DFMA）和0.06 g光引發劑I907溶于20 mL無水THF中，并且用錫箔紙將其裹好作避光處理。B液：稱量2.77 g POSS-SH8溶于20 mL無水THF中。整個反應體系是在充滿干燥N2的氛圍下進行。A液通過恒壓漏斗以20 mL/h的恒定速度滴入裝有B液的平底石英單口燒瓶中，待A液滴加完后，在紫外燈下繼續曝光攪拌反應6 h。用聚四氟乙烯注射器濾膜濾去反應后溶液中的不溶物，然后旋轉蒸餾除去部分THF溶劑。向剩余溶液內加入一定量的無水乙醇后，使用離心機高速離心，得到白色固體物質。接著，使用無水乙醇反復沖洗白色固體物質5～8次。最后在50 ℃的真空干燥烘箱放置36 h，完全去除溶劑后，得到目標產物POSS-SH-DFMA7。

1.2 涂層的制備

先將0.05 g疏水性樹脂與稀釋劑HDDA混合均勻后（疏水性樹脂∶HDDA=4∶1），再加入混合樹脂質量分數為2%的光引發劑（I907），以上體系混合均勻后將其加入到5 mL的THF中。室溫下，在轉速為800 r/min的條件下磁力攪拌2 h，形成均勻的樹脂溶液。然后將不同質量分數的POSS-SH-DFMA7（10%、20%、30%、40%、50%）（占樹脂添加量）和不同體積分數的乙醇（15%、25%、35%、45%、55%）（占THF添加量）分別先后加入到溶液中，先在超聲波震蕩裝置中超聲分散1 h，然后室溫下磁力攪拌24 h。

1.3 樹脂的噴涂與固化

在噴槍口徑為1.0 mm、流速為0.25 mL/s、壓縮氣壓為0.6 MPa的設置下進行噴涂，基材距離噴槍噴嘴25～27 cm，移動速度為3 cm/s，自上而下進行S型噴涂。將自然晾干的涂層試樣放入紫外光固化儀中，紫外光源是1 000 W的高壓汞燈，基材距離紫外燈源28～30 cm，在N2氛圍下固化5 min。

1.4 表征與性能測試

采用傅里葉變溫紅外光譜儀記錄FTIR光譜，分析所得樣品中主要物質的化學組成。靜態水接觸角（WCA）使用座滴法通過在樣品涂層表面滴加5滴5 μL的液滴取其平均值。通過掃描電子顯微鏡和三維超景深顯微鏡，研究不同粗糙結構復合涂層的表面形貌和粗糙度。采用紫外分光光度計測量涂層的透光率，測試范圍380～800 nm。

涂層機械穩定性測試：采用自制裝置，水滴以2 滴/s的速率在高度為30 cm處勻速釋放，測定不同時間下涂層表面的靜態接觸角。

涂層耐候性：將3種超疏水涂層置于戶外露天的環境中，每隔3 d記錄1次它們的接觸角變化。

化學穩定性測試：將3種超疏水涂層用pH值為1～14的HCl和NaOH溶液浸沒24 h，記錄各個pH值下不同涂層的接觸角。

2 結果與討論

2.1 POSS-SH8和POSS-SH-DFMA7的結構分析

POSS-SH8合成前后主要物質的紅外光譜圖如 圖1a所示。在八乙烯基POSS中，1 604 cm?1處為—C==C—的伸縮振動特征峰，3 069 cm?1處為H2C==CH—上的C—H鍵的伸縮振動特征峰，而在POSS-SH8中這2個特征峰消失了。在新產物中出現了2 548 cm?1處的—SH鍵的伸縮振動特征峰，1 022 cm?1處以及682 cm?1處C—S鍵的特征振動峰。這些特征峰的消失與出現證明了原八乙烯基POSS中的碳碳雙鍵與巰基發生了加成反應，生成了目標產物POSS- SH8。POSS-SH-DFMA7合成前后主要物質的紅外光譜圖如圖1b所示。對比2種反應物和1種生成產物的紅外光譜圖，可以發現，在發生巰基-烯點擊反應后，生成物中碳碳雙鍵的特征吸收峰消失了，說明含氟丙烯酸酯單體反應完全；在2 540 cm?1處生成物相較于反應物POSS-SH8的S—H鍵伸縮振動吸收峰有明顯的減弱，說明反應物中部分巰基參與了反應；1 182 cm?1處的碳氟鍵和1 090 cm?1處的硅氧鍵特征峰都在生成物中出現了。所以通過以上的分析可以確定POSS-SH-DFMA7被成功合成。

圖1 POSS巰基化前后（a）及巰基POSS氟烷基化前后主要物質的紅外光譜圖（b）

2.2 POSS-SH-DFMA7和乙醇的添加量對涂層潤濕性能的影響

原PC基材的接觸角為76.19°，滾動角大于90°。純聚氨酯丙烯酸酯涂層已經達到疏水效果，接觸角為92.78°。為了進一步提升涂層的疏水性能，通過加入改性過的含氟鏈段改性納米POSS來降低表面能和提升表面粗糙度。根據圖2，納米POSS-SH-DFMA7的添加量為20%時，涂層展現出最好的疏水性，WCA為127°，滾動角為17°。為了研究乙醇的添加量對涂層疏水性的影響，將POSS-SH-DFMA7的添加量初步確定為20%，探究不同乙醇添加量對疏水涂層接觸角和滾動角的變化。

如圖3所示，在POSS-SH-DFMA7添加量為20%的涂層配方體系中，當乙醇的添加量為25%時，涂層WCA的達到了139°，此時的SA最小，為11°。由于THF的揮發性大于乙醇，溶劑THF揮發后，涂層里剩下未揮發的不良溶劑乙醇，納米POSS在乙醇誘導聚集的作用下，慢慢凝聚成尺寸更大的顆粒。當體系中乙醇添加量小于25%時，期間的粗糙微結構數量雖然很多，但是由于乙醇量較少導致聚集程度不夠，顆粒多以納米級結構為主，難以托舉起水滴，因此該過程中涂層的接觸角隨乙醇量的增加而變大。當加入的乙醇量為45%時，聚集達到臨界狀態，粗糙度達到最大。進一步提升乙醇的添加量，就會促使大顆粒形成，導致表面微結構數量減少，疏水性能下降。

圖2 POSS-SH-DFMA7含量對涂層表面潤濕性能的影響

圖3 POSS-SH-DFMA7添加量為20%時乙醇的添加量對涂層潤濕性能的影響

由于POSS-SH-DFMA7添加量為20%時無法使涂層具備超疏水特性。于是分別探究了低表面能納米POSS添加量為30%、40%、50%的情況下乙醇的最佳添加比例。如圖4a所示，當POSS-SH-DFMA7的添加量為30%時，乙醇添加量為35%，此時疏水效果最佳，WCA增大到151°，SA降低至8°左右，已經達到超疏水效果。如圖4b所示，納米POSS-SH-DFMA7的添加量為40%、乙醇的添加量為25%時，構造出了靜態水接觸角達157°、滾動角小到3.3°的超疏水表面。如圖4c所示，低表面能納米尺寸粒子添加量為50%時，涂層疏水性的變化趨勢與POSS-SH-DFMA7添加量為40%時大體一致。乙醇添加量為25%時，涂層的疏水性能最佳，靜態水接觸角可達161°，滾動角更是小至1.8°。

2.3 POSS-SH-DFMA7光固化涂層表面形貌分析

采用SEM掃描電子顯微鏡和三維超景深顯微鏡分別對POSS-SH-DFMA7添加量為30%、40%、50%最佳疏水效果涂層進行表面形貌和粗糙度表征，結果如圖5所示。從圖5可以看出，隨著納米POSS-SH- DFMA7添加量的增加，涂層表面形成的微米團簇變得越來越多，間隙越來越小。由于團簇是微納復合結構，這種分級結構可以捕獲大量空氣，致使涂層表面和水滴之間可以產生一層“氣墊”，這層“氣墊”極大地減少了水滴與固體表面的接觸面積，因此疏水性能得到提升。粗糙度在3D超景深圖像中體現為凸起結構的高度和密度。由圖5三維超景深顯微結果可知，在乙醇相分離的作用下，粗糙度隨納米POSS-SH- DFMA7添加量的增加而變得越來越大，平均粗糙度分別為1.87、4.43、5.54 μm。這與涂層SEM圖所反映出的信息一致。

圖4 POSS-SH-DFMA7添加量分別為30%、40%和50%時乙醇的添加量對涂層潤濕性能的影響

圖5 POSS30Et35、POSS40Et25和POSS50Et25涂層試樣的表觀形貌和表觀粗糙度

2.4 涂層透光性能測試

通過紫外分光光度計測試PC空白試樣和POSS30Et35、POSS40Et25、POSS50Et25 超疏水涂層的透光率，其透光率曲線如圖6所示。從透光率曲線可以看出，在450～780 nm波段范圍內PC空白試樣的平均透光率為89.76%，涂層POSS30Et35的平均透光率為86.12%，涂層POSS40Et25的平均透光率為83.63%，涂層POSS50Et25的平均透光率為77.37%。在乙醇的相分離作用下，3種超疏水涂層的透明性是隨著納米顆粒添加量的增加呈現出下降的趨勢。光的散射和折射是影響涂層光線透過率的主要因素。

圖6 空白試樣、POSS30Et35、POSS40Et25和POSS50Et25樣品的涂層透過率曲線

2.5 涂層的機械穩定性測試

使用如圖7a所示的水滴沖擊自制設備，進行超疏水涂層機械穩定性能的表征。以每秒2滴的速率向涂層表面釋放液滴，每隔0.5 h記錄各涂層的接觸角變化，如圖7b所示。在經過水滴沖擊4 h后，涂層POSS30Et35的超疏水性消失。而另外2個涂層體系中，由于納米粒子更多且分布更均勻，即使在水滴沖擊6 h后，依然維持著良好的超疏水特性。其中涂層POSS40Et25的接觸角的下降幅度最小，說明其耐水滴沖擊性能最優異，機械穩定性最好。

2.6 涂層的耐候和化學穩定性能測試

圖8a是3種超疏水涂層在戶外環境中的耐候測試結果，在相同的測試周期中，3種涂層的接觸角都呈現出了一定的下降趨勢，其中涂層POSS40Et25的下降幅度最小，說明該涂層的耐候性能最穩定。圖8b是3種超疏水涂層的化學穩定性測試結果。3種超疏水涂層對不同pH值范圍的溶液展現出不同的化學穩定性，根據圖示曲線的起伏程度，可發現涂層POSS40Et25對不同溶劑的適應力更強，化學穩定性最佳。相較于涂層POSS30Et35，涂層POSS40Et25具有更致密的粗糙結構和更高的表面起伏，不管是雨水還是酸堿溶液，與空氣的接觸面積大，不易與涂層內部直接接觸，受侵蝕的程度更小，疏水性能的保持能力更好。而涂層POSS40Et25比涂層POSS50Et25的耐候和化學穩定性更優，主要歸因于前者涂層體系中納米POSS的添加量適度，相分離后的粗糙結構與光固化樹脂之間存在的有效連接趨向于體系的飽和值。另外，在本試驗條件下制備的涂層對涉及酸雨的實際應用效果更好。

圖7 耐水滴沖擊測試裝置圖（a）及3種涂層表面在6 h水滴的持續沖擊下接觸角值的變化（b）

圖8 3種超疏水涂層在戶外環境中的耐氣候測試（a）及不同pH值下的化學穩定性測試（b）

3 結論

本文選取一步噴涂相分離法結合紫外光固化技術作為制備超疏水涂層的方法。采用聚氨酯疏水改性丙烯酸酯作為樹脂基體，HDDA為預聚體稀釋劑，低表面能的POSS-SH-DFMA7為納米填料，THF為溶劑，乙醇為不良溶劑。綜合探究分析后，得出以下結論：當納米POSS-SH-DFMA7添加量為樹脂的40%，不良溶劑乙醇添加量為THF的25%時，涂層的超疏水效果優異，WCA值可達到156.92°，滾動角小至 3.24°，而且涂層的各項應用性能更貼合使用需求，比如高達85.63%的涂層透明度、經受長時間水滴沖擊測試后可靠的涂層黏結力、多元環境長期作用后優異的涂層耐候性能以及不同pH值化學試劑侵蝕后穩定的涂層耐化學性能。

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Transparent Superhydrophobic Coating Prepared by One-step Method Based on Fluorinated Cage-like Sesimiloxane

a,a,b,a,a,c,a,b

(a. School of Chemistry, Chemical Engineering and Biotechnology, b. Key Lab of Textile Science & Technology, Ministry of Education, c. National Engineering Research Center for Dyeing and Finishing of Textiles, Donghua University, Shanghai 201620, China)

The coating film-forming method has good application prospects in the preparation of transparent superhydro-phobic coatings due to its simple process, good repeatability and low equipment requirements. However, the nanofillers in the existing coating film-forming methods generally have defects such as easy aggregation and poor durability. POSS is an organic- inorganic hybrid with a special cage-like structure. Compared with ordinary nanofillers, POSS has the characteristics of monodi-spersity and flexible functional modification. At present, most of the researches on POSS in the field of superhydrophobic coatings are based on rough substrate surfaces, but few researches have been done in the field of mirror-transparent optics. Therefore, the purpose of this study is to select POSS as a nanofiller and use a one-step coating film-forming method to construct a large-area transparent and durable superhydrophobic coating on a mirror substrate.

In this study, an intermediate POSS-SH8was synthesized from octavinyl POSS and ethanedithiol based on a two-step thiol-ene click chemistry reaction. Then, POSS-SH8and dodecafluoroheptyl methacrylate monomer were used as reactants to obtain low surface energy modified product POSS-SH-DFMA7through photoreaction. The effects of the doping mass fraction of F-POSS and the volume fraction of ethanol addition on the construction of superhydrophobic coatings were explored. The preparation of spraying prefabricated liquid was as follows: F-POSS with different mass fractions was blended in resin prepolymer. Resin prepolymer was composed of a mixture of hydrophobic photocurable resin (Changxing 6145-100) and diluent HDDA at 4∶1. After the prepolymer was evenly mixed, the dilution solvent THF was added to the system at a dilution ratio of 1∶20. It was dispersed uniformly in a stirrer and an ultrasonic shaker successively. In order to obtain the rough micro-nano composite structure on the smooth substrate surface, the method of spraying combined with non-solvent induced phase separation was adopted in this study. Different volume fractions of non-solvent ethanol were added to the above system to obtain a series of spraying prefabricated liquids. Next, the prefabricated solution was transferred to the surface of the smooth substrate by spraying and the coating was air-dried at room temperature. Finally, the air-dried coatings were cured in a UV curing apparatus under N2atmosphere for 5 minutes. The chemical composition of the main substances in the obtained samples was analyzed by infrared spectrum curve. The static water contact angle and dynamic rolling angle of the coatings were recorded by contact angle analysis and self-made rolling angle measuring instrument to characterize the hydrophobicity of the coatings. The surface topography and roughness of the composite coatings with different rough structures were investigated by scanning electron microscopy and three-dimensional ultra-depth-of-field microscopy. The transmittance of the coatings was measured by a UV spectrophotometer to characterize the transmittance of the coating. A self-made device was used to set water droplets to be released at a uniform rate of 2 drops per second at a height of 30 cm. The hydrophobic property retention curve of the coatings at different times were obtained to characterize the mechanical stability of the coating. The three superhydrophobic coatings were placed in an outdoor open-air environment, and their contact angle changes were recorded every 3 days to evaluate their weatherability. In addition, the above three coatings were soaked in HCl and NaOH solutions with pH values ??of 1 to 14 for 24 hours. And the contact angle curves of each coating at different pH values ??were recorded to compare their resistance to reagents.

The research results show that the coating exhibits excellent superhydrophobic properties when the doping mass fraction of POSS-SH-DFMA7is 40% of the resin content and the addition volume fraction of ethanol is 25%. The static water contact angle and sliding angle can reach 156.92° and 3.24°, respectively. In addition, the superhydrophobic coating prepared under the optimal process conditions also has good optical transparency and its light transmittance is 85.63%. The coating still maintains superhydrophobic property after being impacted by water droplets for 6 hours, indicating its mechanical stability. Not only that, the original wetting property of the coating can still be maintained after experiencing various outdoor environments and the erosion of chemical agents with different pH values. Therefore, the introduction of a certain amount of fluorine-containing monomer to modify the POSS combined with the phase separation of ethanol into the photocurable resin system can prepare a large-area transparent and superhydrophobic coating with stable physical and chemical properties in one step.

POSS; superhydrophobic coating; transparent; durable; spraying; phase separation; UV curing

tg174；tb34

A

1001-3660(2022)10-0336-08

10.16490/j.cnki.issn.1001-3660.2022.10.036

2021–09–22；

2022–01–22

2021-09-22；

2022-01-22

國家重點研發計劃項目（2017YFB0309100）

Supported by the National Key Technologies R & D Program of China (2017YFB0309100)

徐亞洲（1997—），男，碩士研究生，主要研究方向為功能性聚合物材料。

XU Ya-zhou (1997-), Male, Postgraduate, Research focus: functional polymer material.

何瑾馨（1959—），男，博士，教授，主要研究方向為紡織化學與染整工程。

HE Jin-xin (1959-), Male, Doctor, Professor, Research focus: textile chemistry and dyeing & finishing engineering.

徐亞洲，何瑾馨，朱衛彪，等. 基于含氟改性籠狀倍半硅氧烷一步法制備透明超疏水涂層[J]. 表面技術, 2022, 51(10): 336-343.

XU Ya-zhou, HE Jin-xin, ZHU Wei-biao, et al. Transparent Superhydrophobic Coating Prepared by One-step Method Based on Fluorinated Cage-like Sesimiloxane[J]. Surface Technology, 2022, 51(10): 336-343.

責任編輯：萬長清