POSS基含氟醚链偶氮苯聚合物的制备及其油润湿性光响应可逆转换的研究

Smart surfaces with reversible wettability transitions under external stimuli have recently generated extensive interest due to their wide applicability in various fields.The difficulty to fabricate oleophobic surface resulted from the low surface tension of oily liquids limits the study of switchable oil wettability. Long chain fluorocarbons with low surface free energy are suitable to be used in preparing the switchable oil wettability surface. However, there are increasing evidences for bioaccumulation and/or toxicity of the long chain perfluoroalkyl and its derivatives. Fluoroether-containing compounds seem to be the promising substitute for long-chain fluorocarbons due to their excellent physical and chemical properties such as high chemical resistance, high lubricating ability, low surface energy and low toxicity. In the past decades, polyhedral oligomeric silsesquioxane (POSS)-incorporated polymer materials have attracted increasing interest due to their remarkable performance on the polymer matrix such as higher usage temperature, improved mechanical property and special topography formation than their pristine counterpart. In this study, fluoroether-containing azobenzene compounds will be synthesized to prepare the novel POSS-based azobenzene polymer. The synthesized POSS-based polymer containing azobenzene group and fluoroether chain is supposed to be reversible switching between oleophilicity and oleophobicity, or even superoleophilicity and superoleophobicity in response to UV/visible irradiation. The aim of this study is to explore the relationship between the chemical structures and chem-physical properties of the synthesized monomers and polymers. The polymers with photoswitchable oil wettability are attributed to azobenzene groups reversible photoisomerization between cis and trans conformations. The trans-azobenzene groups cause the surface free energy low enough to achieve the oleophobicity due to the connected fluoroether chains stretching to the most top layer of the surface, and the cis-azobenzene groups make the surface change to oleophilicity because of the higher surface free energy resulted from aliphatic chain exposing to the surface. Under the both conditions, POSS segments with the micro- and nanoscale hierarchical surface structures enhance the oil wettability.

环境响应润湿性智能表面具有广泛的应用前景。但油的表面张力较小，使疏油表面较疏水表面制备困难，制约了油润湿性环境响应智能表面的发展。长氟碳链化合物表面自由能极低，适于该类智能表面的制备，但存在难生物降解和环境不友好等缺点。用于高级润滑剂的氟醚类聚合物，也具有较低表面自由能，且易被生物降解，有望开发成为长氟碳链化合物的替代品。笼状结构的多面体低聚倍半硅氧烷（POSS）具有天然纳米尺度，能提高聚合物热稳定性及力学性能，并赋予表面特殊形貌，成为材料领域研究热点。本项目拟合成含氟醚链偶氮苯化合物，制备新型POSS基含氟偶氮苯聚合物，研究物质制备-结构-性质之间内在联系。所得聚合物在不同光照下，偶氮苯基团发生光致顺反异构转换，与之相连的脂肪链、氟醚链交替伸向表面，改变表面自由能，实现亲油-疏油可逆转换；POSS基团微相分离构建多尺度微纳表面结构，增强响应强度，实现超亲油-超疏油可逆转换。

环境响应性润湿智能表面在微流体装置、智能膜、可控药物释放、传感器及湍流研究等领域具有潜在的应用前景。目前，光响应水润湿性可逆转换已具有一定的研究基础，但光响应油润湿性的研究鲜有报道。长氟碳链（-CnF2n+1，n ≥ 8）化合物表面自由能极低，适于该类智能表面的制备，然而长氟碳链难被生物降解，具有持久性和累积性，严重危害环境，影响生物体及人类健康。本项目采用全氟醚链替代长氟碳链，成功制备含氟偶氮苯及其POSS基聚合物，对其光致异构行为及其疏水疏油光响应行为进行了系统研究。. 为了与同类含氟偶氮苯化合物及其聚合物进行比较，本项目在研究全氟醚链偶氮苯单体及其POSS基聚合物的同时，也制备了含氟短碳链（全氟丁基，全氟己基）、含氟长碳链（全氟辛基）偶氮苯化合物及其POSS基聚合物。通过比较，系统研究了四类含氟偶氮苯化合物的光致异构行为及其POSS基聚合物疏水疏油性的光响应性。. 主要研究内容如下： . 以全氟丁基碘烷、全氟己基碘烷和全氟辛基碘烷为原料经过乌尔曼反应、重氮偶合反应和酯化反应，制备了含全氟烷基链的丙烯酸酯单体7a～c。以六氟环氧丙烷三聚体(THPF)为原料经过酰胺化反应、重氮偶合反应和酯化反应，制备了含全氟醚链的丙烯酸酯单体12。化合物7a～c和12分别与甲基丙烯酸甲酯(MMA)和八乙烯基低聚倍半硅氧烷(Ov-POSS)在发生自由基聚合反应制得具有不同POSS含量的POSS基全氟烷基偶氮苯聚合物（P1～P16）和POSS基全氟醚链偶氮苯聚合物（P17～P20）。所得聚合物经1H NMR，19F NMR、29Si NMR、FT-IR、UV和TGA等分析进行结构和物理性能的表征。经聚合物P13～P16整理后的棉织物表面S1～S4与水和色拉油的最大接触角分别可达156°和143°。经聚合物P17～P20整理后的织物表面S5～S8与水和色拉油的最大接触角分别可达153°和140°。经紫外光照射10 min后，整理后织物表面S1～S8与水和色拉油的接触角最大分别降低21°和30°，S5～S8与水和色拉油的接触角最大分别降低19°和22°。再将S1～S8放置在可见光下照射1 h后，S1～S8与水和色拉油的接触角均能恢复至紫外光照前的水平。经过四个紫外-可见光的照射循环，织物表面与水和色拉油的接触角仍能发生润湿性可逆变化，说明其具有耐疲性。