【作者】 邢文涛；

【导师】 武利民； 游波；

【作者基本信息】 复旦大学 ， 材料物理与化学， 2008， 硕士

【摘要】 聚倍半硅氧烷（Polysilsesquioxanes,PSSQ）是一指结构式为RSiO_3/2的有机硅聚合物,R可以是氢基、烷基、芳香基、烯烃基以及其他的有机取代基团。聚倍半硅氧烷基本组成是由Si-O键构成主链,侧链则是与硅原子相连的各种有机基团。因此,在聚倍半硅氧烷结构中既含有“有机基团”,又含有“无机骨架”。这种特殊的分子结构使其具有优异的耐热性、耐候性、耐化学性、力学性能和电学性能,所以被广泛地用于涂层材料、塑料及电子材料等领域。聚倍半硅氧烷制备通常通过溶胶-凝胶方法来制备,一般分为两步,第一步是预聚物的制备,一般由三氯硅烷或者三烷氧基硅烷的水解缩聚而制得。第二步是预聚物的进一步缩合最终成膜。通过这种方法制备的涂膜能够给基材提供疏水保护层,可以用作耐腐蚀涂层。但是,由于其制备过程常用小分子酸（如盐酸、硝酸、醋酸）作催化剂,体系中的游离酸在成膜过程中容易腐蚀金属基材,所以其耐腐蚀性能不够理想。本论文首次采用大分子植酸为催化剂,通过水解缩合甲基三乙氧基硅烷（MTES）、缩水甘油醚氧丙基三甲氧基硅烷（KH560）和正硅酸乙酯（TEOS）制备了植酸催化的倍半硅氧烷涂层。植酸(C₆H₁₈O₂₄P₆)是一种天然的有机膦酸化合物,分子中有6个磷酸键,可与金属络合,形成一层致密的单分子有机保护膜。我们用GPC、¹³C NMR、²⁹Si NMR、SEM以及电化学测试分析手段（包括动电位极化曲线和电化学阻抗谱）等分析手段表征,对比盐酸催化的聚倍半硅氧烷,发现植酸催化的聚倍半硅氧烷交联度高、分子量大,并且其结构上的螯合基团与金属表面键合,在金属表面形成致密的保护层,耐腐蚀性能明显提高。我们进一步研究了植酸和正硅酸乙酯的用量对倍半硅氧烷涂层的耐腐蚀性能的影响,并发现当植酸用量为0.010-0.014mol/L以及TEOS用量为0.055-0.01mol/L时,植酸催化的倍半硅氧烷涂层的耐腐性能最优。另外,为了探求不同的酸性催化剂对聚倍半硅氧烷耐腐蚀性能的影响,我们进一步选用不同的酸:植酸（phytic acid）,羟基乙叉二膦酸（1-hydroxyethylidene-1,1-diphosphonic acid）,单宁酸（tannic acid）作为催化剂,水解缩合甲基三乙氧基硅烷（MTES）、缩水甘油醚氧丙基三甲氧基硅烷（KH560）和正硅酸乙酯（TEOS）,制备了不同酸催化的聚倍半硅氧烷涂层。我们通过使用¹³C NMR,²⁹Si NMR,GPC,SEM,电化学测试方法以及耐盐雾测试来比较不同酸对聚倍半硅氧烷结构和耐腐蚀性能的影响,我们发现不同酸催化的倍半硅氧烷涂层的耐腐性能依次如下;植酸＞羟基乙叉二膦酸＞单宁酸＞盐酸。为了进一步增加聚倍半硅氧烷涂层的附着力和成膜性,我们先制备了PMMA/甲基丙烯酰氧丙基三甲氧基硅烷（KH570）共聚物,利用共聚物中硅烷的烷氧基基团和甲基三乙氧基硅烷（MTES）、缩水甘油醚氧丙基三甲氧基硅烷（KH560）和正硅酸乙酯（TEOS）共水解缩合的方法,制备了均相的PMMA改性的酸催化倍半硅氧烷涂层。我们用GPC、²⁹Si NMR、FTIR、SEM系统的研究了PMMA改性倍半硅氧烷涂层的基本组成和微观形貌,另外,我们通过电化学方法研究了不同PMMA含量以及PMMA分子量对涂层耐腐蚀性的影响,并发现PMMA改性的酸催化倍半硅氧烷涂层有着非常优异的耐腐蚀性能。更多还原

【Abstract】 Polysilsesquioxanes refer to a kind of polysiloxanes with a formula of(RSiO_3/2)_n, where R is hydrogen,alkyl,aryl,alkylene groups or other organic groups.The main chains of polysilsesquioxanes are composed of Si-O structures,while the side chains consist of organic groups which attach to the silicon atom.Such unique structures contain both inorganic and organic parts,resulting in their outstanding thermal, chemical,mechanical,and electronic properties.They have been widely used as coatings,engineering plastics and electronic materials.Polysilsesquioxanes used as coatings are commonly synthesized via sol-gel process.It can be divided into two steps.The first step is the preparation of prepolymers based on acid-catalyzed hydrolysis and condensation of organotrialkoxysilanes or organotrichlorosilanes.The second step is the further condensation of the prepolymer in the film forming process.These polysilsesquioxanes can be used as anticorrosive coatings because of their hydrophobic properties.The frequently used catalysts in the sol-gel process of siloxane precursors are small molecular inorganic acids such as hydrochloric acid, acetic acid and nitric acid,which usually remain in the coatings as free molecules, causing negative influences on the corrosion resistant property of polysilsesquioxanes.In this paper,we used phytic acid as a catalyst for the first time to prepare polysilsesquioxane coatings.Phytic acid(C₆H₁₈O₂₄P₆),a natural and innoxious organic big molecule compound,consist of 6 phosphate carboxyl groups.This peculiar structure makes phytic acid have powerful chelating capability with many metal ions, forming a protective coating at the surface of the metals.The objective of this research was to explore the possibility of phytic acid-catalyzed siloxane precursors for preparation of corrosion resistant polysilsesquioxane coatings,by investigating the microstructure and properties of phytic acid-catalyzed polysilsesquioxanes with aid of ¹³C NMR,²⁹Si NMR,GPC,SEM,electrochemical techniques and salt spray test, respectively.The microstructure and properties of hydrochloric acid-catalyzed polysilsesquioxane films were also studied for the sake of comparison.It was found that phytic acid could catalyze the sol-gel reaction more efficiently than hydrochloric acid,causing greater molecule weight of polysilsesquioxanes.Potentiodynamic polarization,EIS and salt-fog praying measurements showed the phytic acid-catalyzed polysilsesquioxane coatings had better corrosion resistant performance than the hydrochloric acid-catalyzed polysilsesquioxane coatings.In addition,we found when the concentration of phytic acid is equal to 0.010-0.014mol/L,and the concentration of TEOS is equal to 0.055-0.01mol/L,optimal anticorrosive property of polysilsesquioxane coatings can be obtained.Besides,in this paper,we tried to prepare polysilsesquioxanes via sol-gel process of methyltriethoxysilane（MTES）,3-glycidoxypropyltrimethoxysilane（KH560） and tetraethoxysilane（TEOS） using phytic acid,tannic acid and 1-hydroxyethylidene-1,1-diphosphonic acid（HEDPA） as the catalysts,respectively. The objective of this research was to compare the influence of different kinds of acid catalyst on the microstructure and corrosion resistant property of polysilsesquioxane coatings with the aid of ¹³C NMR,²⁹Si NMR,GPC,SEM,electrochemical techniques and salt-spray test,respectively.The microstructure and anticorrosion property of hydrochloric acid-catalyzed polysilsesquioxanes were also studied for the sake of comparison.It was found that phytic acid catalyzed polysilsesquioxane coatings have the best anticorrosive property,HEDPA catalyzed polysilsesquioxane coatings took the second place,tannic acid catalyzed polysilsesquioxane coatings took the third place,HCl catalyzed polysilsesquioxane coatings took the forth place.In order to improve the adhesion and compactness of the film,the poly（methyl methacrylate） modified polysilsesquioxanes were successfully synthesized by using KH570 as a coupling agent.In this work,KH570 is first copolymerized with methyl methacrylate monomer by using AIBN as initiator.Subsequently,the as-prepared copolymer is then cohydrolyzed with MTES and TEOS to afford chemical bondings to the forming silica networks,giving a series of PMMA-Modified Polysilsesquioxanes.Their microstructure and corrosion resistant performance were investigated by ²⁹Si NMR,GPC,SEM and electrochemical techniques,respectively. Furthermore,the effect of PMMA content and PMMA molecular weight were also studied via electrochemical techniques.It was found that PMMA-modified polysilsesquioxane coatings had excellent corrosion resistance performance compared to polysilsesquioxanes only.更多还原