壳聚糖表面接枝聚苯胺的防腐蚀性能
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摘要
利用壳聚糖结构中氨基的特性,采用过硫酸铵为氧化剂,通过化学氧化聚合,合成了不同表面浸润性的3种壳聚糖接枝聚苯胺。掺杂酸分别为辛酸、十四酸和全氟辛酸。通过聚苯胺在壳聚糖上的接枝,改善了聚苯胺的可加工性,并保持了聚苯胺的导电性。Tafel极化曲线和电化学阻抗结果表明壳聚糖接枝聚苯胺在0.10 mol/L H_2SO_4中对A3碳钢表现出良好的防腐蚀性能,且其防腐效率随着壳聚糖接枝聚苯胺的疏水性增加而提高;疏水性最强的壳聚糖接枝全氟辛酸掺杂聚苯胺材料静态触角为142°,防腐效率为70.75%。研究表明不同接枝材料的疏水性能是受掺杂酸的影响,另外采用红外光谱和核磁共振证实了壳聚糖与聚苯胺的有效接枝。
In this paper, three kinds of conducting chitosan-graft-polyaniline were successfully prepared in order to improve the processability of polyaniline(PANI). Chitosan was grafted with polyaniline through oxidative-radical copolymerization using ammonium persulfate in acidic medium. And three acids(octanoic acid, dodecanoic acid and perfluorooctanoic acid) were used as dopant. The processability of PANI is successfully improved by grafting onto the chitosan and the electrical conductivity of PANI is maintained at 10~(-4)～10~(-2) S/cm. Tafel polarization and electrochemical impedance spectroscopy show that the chitosan-graft-polyaniline has a good anticorrosion protection to A3 carbon steel exposed to 0.10 mol/L H_2SO_4 aqueous solution, and the anticorrosion efficiency of the chitosan-graft-polyaniline increases with increasing the hydrophobicity of the chitosan-graft-polyaniline. This is due to the hydrophobic conducting chitosan-graft-polyaniline coating inhibited water from being absorbed by the coating, thus preventing corrosive chemicals and corrosion products from diffusing through the coatings. The perfluorooctanoic acid doped chitosan-graft-polyaniline has the highestest hydrophobicity with a contact angle of 142° and the anticorrosion efficiency of 70.75%. The grafting of PANI onto the chitosan molecules is confirmed by Fourier transform infrared spectroscopy(FT-IR) and ~1H-nuclear magnetic resonance(~1H-NMR) spectroscopy. As FT-IR shown, grafted polymers has not only the characteristic peaks of chitosan and polyaniline, but also peak shift phenomenona which is affected by the space effect after grafting. Therefore, the relation between chitosan and polyaniline is not physical mixing but grafting.
In this paper, three kinds of conducting chitosan-graft-polyaniline were successfully prepared in order to improve the processability of polyaniline(PANI). Chitosan was grafted with polyaniline through oxidative-radical copolymerization using ammonium persulfate in acidic medium. And three acids(octanoic acid, dodecanoic acid and perfluorooctanoic acid) were used as dopant. The processability of PANI is successfully improved by grafting onto the chitosan and the electrical conductivity of PANI is maintained at 10~(-4)～10~(-2) S/cm. Tafel polarization and electrochemical impedance spectroscopy show that the chitosan-graft-polyaniline has a good anticorrosion protection to A3 carbon steel exposed to 0.10 mol/L H_2SO_4 aqueous solution, and the anticorrosion efficiency of the chitosan-graft-polyaniline increases with increasing the hydrophobicity of the chitosan-graft-polyaniline. This is due to the hydrophobic conducting chitosan-graft-polyaniline coating inhibited water from being absorbed by the coating, thus preventing corrosive chemicals and corrosion products from diffusing through the coatings. The perfluorooctanoic acid doped chitosan-graft-polyaniline has the highestest hydrophobicity with a contact angle of 142° and the anticorrosion efficiency of 70.75%. The grafting of PANI onto the chitosan molecules is confirmed by Fourier transform infrared spectroscopy(FT-IR) and ~1H-nuclear magnetic resonance(~1H-NMR) spectroscopy. As FT-IR shown, grafted polymers has not only the characteristic peaks of chitosan and polyaniline, but also peak shift phenomenona which is affected by the space effect after grafting. Therefore, the relation between chitosan and polyaniline is not physical mixing but grafting.
引文
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[2] Yang X G,Li B,Wang H Z.Anticorrosion performance of polyaniline nanostructures on mild steel [J].Prog.Org.Coat.,2010,69:267-271.
[3] Takahashi K,Nakamura K,Yamaguchi T,et al.Characterization of water-soluble externally HCl-doped conducting polyaniline [J].Synth.Met.,2002,128:27-33.
[4] Tiwari A,Singh V.Synthesis and characterization of electrical conducting chitosan-graft-polyaniline [J].Express Polym.Lett.,2007,1:308-317.
[5] Coskun E,Martinez-Ramirez S M,Antunez-Flores W,et al.Improving polyaniline processability by grafting acrylic copolymer [J].Synth.Met.,2012,62:344-351.
[6] Ramaprasad A T,Rao V,Sanjeev G,et al.Grafting of polyaniline onto the radiation crosslinked chitosan [J].Synth.Met.,2009,159:1983-1990.
[7] Hosseini S H,Simiari J,Farhadpour B.Chemical and electrochemical grafting of polyaniline onto chitosan [J].Iran.Polym.J.,2009,18:3-13.
[8] Yang S,Tirmizi S A,Burns A,et al.Chitaline materials:soluble chitosan-polyaniline copolymers and their conductive doped forms [J].Synth.Met.,1989,32:191-200.
[9] 邢翠娟,于良民,张志明.超疏水性聚苯胺微 / 纳米结构的合成及防腐蚀性能 [J].高等学校化学学报,2013,34(8):1999-2004.Xing C J,Yu L M,Zhang Z M.Superhydrophobic polyaniline micro/nano structures as anticorrosion coating [J].Chemical Journal of Chinese Universities,2013,34(8):1999-2004.
[10] 朱英,张敬畅,郑咏梅,等.浸润性可调的导电聚苯胺 / 聚丙烯腈同轴纳米纤维 [J].高等学校化学学报,2006,27(1):196-198.Zhu Y,Zhang J C,Zheng Y M,et al.Conducting PANI/PAN coaxial nanofibers with tuned wettability [J].Chemical Journal of Chinese Universities,2006,27(1):196-198.
[11] Genzer J,Efimenko K.Recent developments in superhydrophobic surfaces and their relevance to marine fouling:a review [J].Biofouling,2006,22:339-360.
[12] 王兴.碱诱导合成聚苯胺微/纳米结构及应用研究 [D].长春:吉林大学,2006.Wang X.Alkali-guided synthesis of polyaniline micro/nano structures and their application [D].Changchun:Jilin University,2006.