【作者】 李志涛；

【导师】 马利；

【作者基本信息】 重庆大学 ， 化学工程与技术， 2014， 博士

【摘要】 尽管大量的文献报道都证明了聚苯胺具有良好的耐腐蚀性能，但是由于分子链骨架刚性较强，分子间相互作用力大，导致溶解、加工性较差，使其在商业应用前景上受到很大的限制。对聚苯胺进行一定的化学修饰或改性，如在聚苯胺的分子链上引入一定的取代基生成聚苯胺衍生物可以有效的改善PANI难溶解和不易加工的缺陷。聚2,3-二甲基苯胺（P(2,3-DMA)）作为聚苯胺的主要衍生物之一，由于苯环上两个甲基（-CH3）的空间位阻效应，可以降低PANI分子链的刚性，减小链间相互作用力，可以很大程度上提高PANI的溶解性，因此在防腐方面具有较好的应用前景。并利用复合法制备聚2,3-二甲基苯胺/无机纳米复合材料，充分发挥聚合物和无机纳米材料各自的优势，使P(2,3-DMA)的防腐性能和热稳定性都有所提高。具体工作如下：采用乳液聚合法，以十二烷基苯磺酸（DBSA）既作为乳化剂又作为掺杂剂合成了十二烷基苯磺酸掺杂的P(2,3-DMA)。通过红外光谱，X射线衍射，场发射扫描电镜对聚合物的结构和形貌进行表征。并分别使用循环伏安法和热重分析对P(2,3-DMA)的电化学和热稳定性能进行了研究。将在同等条件下合成的PANI和P(2,3-DMA)加入到环氧树脂中，在钢铁表面进行涂层，在3.5%的NaCl溶液中测试其耐腐蚀性能。首次在磷酸体系中用过硫酸铵作氧化剂采用原位溶液聚合法合成了磷酸掺杂的P(2,3-DMA)/TiO2复合物。采用负载有复合物的碳纸为工作电极，使用电化学测试及产率表征，探讨了TiO2的含量对复合物性能的影响，得到TiO2的最佳含量为15%。同时对合成的复合物使用红外光谱，X射线衍射，场发射扫描电镜等进行结构和形貌表征。将复合物加入到环氧树脂中进行涂层，然后采用开路电位-时间曲线和交流阻抗法对其耐腐蚀性能进行研究。采用过硫酸铵为氧化剂，十二烷基苯磺酸（DBSA）为乳化剂的乳液聚合体系，合成了十二烷基苯磺酸掺杂的P(2,3-DMA)-Al2O3复合物。采用红外光谱分析、紫外可见光谱、扫描电镜对复合材料的结构和形貌进行表征。并使用循环伏安法和热重分析对复合物的电化学和热稳定性能进行了研究。将复合材料加入到环氧树脂中，在低碳钢表面制备涂层。采用塔菲尔极化曲线,开路电位-时间曲线对涂层的防腐性能进行研究。研究结果表明：（1）用十二烷基苯磺酸既做乳化剂又做掺杂剂采用乳液法成功的合成了P(2,3-DMA)。表征结果表明P(2,3-DMA)具有和PANI类似的结构。两个甲基取代基造成的空间位阻效应降低了PANI分子链的刚性，从而有效的提高了其在有机溶剂中的溶解性。通过交流阻抗谱，开路电位-时间曲线测试，Tafel极化曲线测试表明，P(2,3-DMA)具有比PANI更好的耐腐蚀性能，有可能替代PANI在金属防腐领域大规模使用。（2）对采用原位氧化聚合法在磷酸溶液中用过硫酸铵做氧化剂合成出的P(2,3-DMA)-TiO2复合物进行表征。红外光谱表明P(2,3-DMA)和TiO2之间有相互作用力的存在，这种相互作用力可能存在于P(2,3-DMA)大分子链的N原子和TiO2纳米颗粒的Ti原子之间。Ti为过度金属元素，具有3d4s的外层电子结构，有空轨道，而P(2,3-DMA)中的N原子含有孤对电子，具有空轨道的Ti原子可以和具有孤对电子的N原子之间形成N-Ti配位键。X射线衍射表明，TiO2的晶型没有受到P(2,3-DMA)的影响。场发射扫描表明TiO2纳米颗粒被P(2,3-DMA)聚合物完全包覆。在3.5%的NaCl溶液中的浸泡实验结果表明P(2,3-DMA)-TiO2复合物环氧涂层具有比P(2,3-DMA)和PANI更好的耐腐蚀性能。P(2,3-DMA)-TiO2复合物优良的耐腐蚀性能是因为其良好的屏蔽作用，P(2,3-DMA)的氧化还原性和相对较高的比表面积。（3）采用十二烷基苯磺酸既作为乳化剂又作为掺杂剂成功的合成出了十二烷基苯磺酸掺杂的P(2,3-DMA)-Al2O3复合物。结构分析表明Al2O3纳米颗粒和P(2,3-DMA)大分子之间有相互作用力的存在。热重分析表明Al2O3纳米颗粒的加入提高了P(2,3-DMA)的热稳定性。P(2,3-DMA)-Al2O3具有可逆且稳定的电化学活性，塔菲尔极化曲线,开路电位-时间曲线表明其在3.5%NaCl耐腐蚀性能高于P(2,3-DMA)。（4）P(2,3-DMA)及其无机纳米粒子复合物材料具有良好的溶解性及耐腐蚀性能，有望在防腐领域替代PANI大规模使用。更多还原

【Abstract】 Despite the large amount of literature has demonstrated that polyaniline has goodcorrosion resistance of mild steel, the poor solubility and processing properties of PANIcaused by its high rigidity of molecular chain backbone and large intermolecularinteractions restricted its commercial applications greatly. One of a certain chemicalmodifications of polyaniline, such as the introduction of certain substituents generatepolyaniline derivatives can effectively improve the insolubility and difficultprocessability of PANI. Poly(2,3-dimethylaniline)(P(2,3-DMA)) is a major derivativesof polyaniline, which was substituted by two methyl groups on the same side of benzenering. The stiffness of PANI backbone was effectively decreased due to the high sterichindrance between the molecular chains so that the solubility of PANI could beimproved. P(2,3-DMA) has a good application prospect in terms of corrosion. Thepolymer–nano-inorganic materials-based composites may combine the advantages ofpolymers like flexibility, processability, durability, load bearing capability, etc. and ofinorganic nanofillers like selectivity, thermal stability, high melting and boiling points,and densities. So we prepared a series of poly(2,3-dimethylaniline)/nano-inorganiccomposite materials in order to improve the corrosion resistance and thermal stability ofP(2,3-DMA). Details are as follows:P(2,3-DMA) was synthesized by emulsion polymerization using dodecyl benzenesulfonic acid as emulsifier and dopant. Effects of the two methyl substituents on thestructure and morphology of polyaniline were characterized by Fourier TransformationInfrared spectroscopy (FTIR), Wide-angle X-ray diffraction (WXRD), Field emissionscanning electron microscopy (FESEM). Cyclic voltammetry measurements (CV) andthermogravimetric analysis (TGA) was used to study the electrochemical and thermalstability. Epoxy resin coating containing P(2,3-DMA) and PANI respectively werepainted on mild steel and accelerated immersion tests were performed to evaluate theanticorrosion property of the coatings in3.5%NaCl solution.Poly(2,3-dimethylaniline)-TiO2composite (PTC) was prepared by oxidativepolymerization of2,3-dimethylaniline in phosphoric acid medium with ammoniumpersulphate as oxidant for the first time. Carbon papers loaded PTC were used asworking electrode for electrochemical tests to study the effects of TiO2on the propertiesof the composite. The results showed that the property was best when the content of TiO2was15%. The composite was characterized by Fourier transformation infrared(FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM).Suitable coating with PTC was formed on steel using epoxy resin, and its corrosionresistance behavior was studied by open circuit potential (OCP) and electrochemicalimpendence spectroscopy (EIS) in3.5%NaCl solution.Poly(2,3-dimethylaniline)/nano-Al2O3composite (PAC) was synthesized byemulsion polymerization using dodecyl benzene sulfonic acid as emulsifier and dopant.The structure of PAC was characterized by Fourier fransformation infrared spectroscopy,UV–visible adsorption spectroscopy, and field emission scanning electron microscopy.The thermal stability was studied by thermogravimetric analysis, and theelectrochemical performances were studied by cyclic voltammetry measurements.Epoxy coatings containing PAC and P(2,3-DMA) respectively, were painted on steel,and accelerated immersion tests were performed to evaluate the anticorrosion propertyof the coatings in3.5%NaCl solution.The results showed that:(1) P(2,3-DMA) was successfully prepared by emulsion polymerization usingdodecyl benzene sulfonic acid (DBSA) as emulsifier and dopant. The results indicatedthat the structure of P(2,3-DMA) was similar with that of PANI. The high sterichindrance between the molecular chains caused by the two methyl group substitutionseffectively decreased the stiffness of PANI backbone so that the solubility of PANI wassignificantly improved. The coatings of P(2,3-DMA) were found to offer good corrosionprotection and showed a better anticorrosion performance than conventional polyanilinecoating according to the results of EIS, OCP and TAF measurements in3.5%NaClsolution, which shows a promising prospect for P(2,3-DMA) in the field of corrosionprotection and more suitable for the industrialization.(2) P(2,3-DMA)-TiO2composite was successfully prepared by chemicalpolymerization of2,3-DMA and TiO2in the presence of phosphoric acid usingammonium persulfate as oxidant. The FTIR spectra show that there is an interactionexists at the interface of P(2,3-DMA) and TiO2particles. The interaction may beassociated with the interaction of titanic and nitrogen atom in P(2,3-DMA)macromolecule. Titanium is a transition metal, has intense tendency to formcoordination compound with nitrogen atom in P(2,3-DMA) macromolecule. XRDpattern of PTC indicates that the crystallinity of TiO2is not altered by P(2,3-DMA)polymer. The SEM study of PTC clearly shows that TiO2particles are fully covered by P(2,3-DMA). Open circuit potentials and impedance studies of coated samples in3.5%NaCl immersion test have shown that coating containing PTC has got higher corrosionresistant property than that of P(2,3-DMA) and PANI. The higher corrosion protectionability of coating containing PTC has been associated with the increase in barrier todiffusion, redox properties of P(2,3-DMA) as well as very large surface area availablefor the liberation of dopant due to the addition of nano-TiO2particles.(3) PAC was successfully prepared by emulsion polymerization using DBSA asemulsifier and dopant. The structure characterization shows that there is an interactionbetween the Al2O3nanoparticles and P(2,3-DMA) macromolecules. The TGA indicatesthat the thermal stability of PAC is much better than that of P(2,3-DMA). Theelectrochemical behavior of the PAC is reversible and stable, and its anticorrosionperformance is better than that of P(2,3-DMA) in3.5%NaCl solution.(4) P(2,3-DMA) and its inorganic nanoparticles composites have good solubilityand corrosion resistance, is expected to replace the massive use of PANI in the field ofanticorrosion of metals.更多还原