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A interação do polímero poli(4-vinilpiridina) (P4VP) e íons tiocianato com cobre em soluções ácidas foi estudada através de voltametria cíclica, termogravimetria, análise elementar e espectroscopia na região do infravermelho. Observou-se que os íons Cu(I) eletrogerados em ca. -0,45 V/ECS na superfície do eletrodo promovem uma reação de complexação com P4VP e SCN -, ambos presentes em solução. O complexo polimérico eletroativo resultante cresce sobre a superfície do eletrodo como um filme e o centro metálico é oxidado para Cu(II) numa etapa subseqüente em ca. -0,23 V/ECS. De acordo com os resultados termogravimétricos, o complexo obtido é menos estável do que o P4VP puro, conforme indicado pelo abaixamento da temperatura inicial de degradação de ca. 400 ºC (P4VP) para ca. 200 ºC (complexo). A análise elementar do filme revelou uma composição química de 2:1:2 para P4VP:Cu:SCN -e os espectros na região do infravermelho indicaram que tal complexo polimérico é formado por um centro metálico de cobre coordenado pelos átomos de nitrogênio dos anéis piridínicos e íons tiocianato.The interaction of poly(4-vinylpyridine) (P4VP) and thiocyanate ions with copper in acid solutions was studied by cyclic voltammetry, thermogravimetry, elemental analysis and infrared spectroscopy. It is shown that at ca. -0.45 V/SCE the electrogenerated Cu(I) ions at the surface of a copper electrode induce a complexing reaction with P4VP and SCN -both present in solution. The resulting electroactive polymer-complex grows onto the electrode surface as a film, and the metallic center is further oxidized to Cu(II) in a subsequent step at ca. -0.23 V/SCE. According to thermogravimetric results, the polymer-complex is less thermally-stable than P4VP as evidenced by the lowering in the initial temperature of degradation from ca. 400 ºC (P4VP) to ca. 200 ºC (complex). The elemental analysis revealed a chemical composition of 2:1:2 for P4VP:Cu:SCN, and the infrared spectra indicated that the complex comprises a copper metallic center coordinated with nitrogen pyridinic rings (P4VP) and thiocyanate ions.

Neste trabalho investigou-se a capacidade de filmes de poli(4-vinilpiridina) (P4VP) em melhorar as propriedades de corrosão do cobre em H 2 SO 4 0,1 mol L -1 . Filmes que formam o complexo macromolecular Cu(P4VP) 2 (SCN) 2 foram obtidos por métodos eletroquímicos ou espontaneamente (por imersão) em soluções contendo 3% de ácido acético, KSCN 0,1 mol L -1 e P4VP. As características morfológicas dos filmes e o seu efeito sobre a corrosão do cobre foram analisados por técnicas de microscopia e eletroquímicas, respectivamente. Um aumento acentuado na resistência à corrosão de amostras de cobre recobertas por filmes de P4VP gerados espontaneamente foi observado em comparação às amostras não recobertas. A melhor condição para a obtenção destes filmes consiste na imersão do cobre em soluções contendo P4VP 0,1 mol L -1 durante 3 -4 h. Empregando-se esta metodologia, registraram-se eficiências de inibição (EI) de 94 -98%. Para filmes gerados eletroquimicamente, a EI foi de 70 -85%.We report here on the ability of poly(4-vinylpyridine) (P4VP) films to improve the copper corrosion properties in 0.1 mol L -1 H 2 SO 4 . Films formed by Cu(P4VP) 2 (SCN) 2 macromecularcomplex were electrochemically or spontaneously (by immersion) grown onto copper surfaces in 3% acetic acid, 0.1 mol L -1 KSCN and P4VP containing solutions. Imaging and electrochemical techniques were employed to characterize the film morphology and evaluate its effect on the copper corrosion, respectively. A substantial increase in corrosion resistance of copper samples spontaneously coated by P4VP films was found in comparison to the uncoated ones. The optimum conditions for spontaneous growth comprise a 3 -4 h immersion period in a 0.1 mol L -1 P4VP containing solution. Inhibition efficiencies (IE) of 94 -98% were recorded by employing this methodology. For electrochemically grown P4VP films, the IE was 70 -85%. Keywords: poly(4-vinylpyridine), corrosion, copper IntroductionThe use of d-block metals to produce coordination complexes in polymer blends has been studied over the past few decades. 1 By physically mixing transition-metals cations and coordinating polymers, it has been possible to obtain materials with properties different from those of the individual bulk components. 2,3 Recently, the importance of developing macromolecular complexes was highlighted because of their optical, magnetic, electronic and solution properties. 4 For instance, the conducting and thermal properties of poly(4-vinylpyridine) (P4VP) are significantly changed when the polymer is complexed with copper ions. 5 The technological applications of the P4VP/ copper system include reactive blending, 6 catalyst, 7-9 cation exchange resins and membranes designed to preconcentrate metals from dilute solutions 10 or remove them from wastewater, 11 solid-state electrochemical cells, 12 circuit manufacturing on microscopic smoothly polymeric surfaces 13 and anti-corrosion methods. 14 Poly(4-vinylpyridine)/cupric salts complexes can be synthesized by physical mixing methods, and their therma...

The effect of poly(2-vinyl pyridine) (P2VP) and poly(4-vinyl pyridine) (P4VP) isomers on the growth of surface films on copper substrates was studied by electrochemical, spectroscopic, thermogravimentric, and microscopic methods. In acid environment (3% v/v acetic acid) and in the presence of KSCN, electrochemically generated copper cations reacted rapidly with SCN À and P2VP or P4VP, yielding coordination compounds, which deposited onto copper surfaces as films. The characteristics of such polymer-metal complexes (films) were markedly isomer-dependent. Cu(I)/ P2VP/SCN À complexes with monovalent cations and sulfur-coordinated thiocyanate were obtained in the presence of P2VP, whereas the formation of Cu(II)/P4VP/SCN À complexes with divalent cations and nitrogen-coordinated thiocyanate was observed in the presence of P4VP. Interestingly, similar physical-chemical properties (electronic structure, stoichiometry, and thermal behavior) were observed for materials synthesized by electrochemical and chemical methods. These results suggest, therefore, that control over the surface properties of copper substrates can be achieved using electrosynthesized films based on different PVP isomers. Besides acting as effective protective barriers against aggressive media and thus reducing the metal dissolution (corrosion) kinetics, these materials are potentially attractive for other applications in which surface properties are paramount, such as in catalysis.