Impact of molecular structure of two natural phenolic isomers on the protective characteristics of electropolymerized nanolayers formed on copper.

BERTUOLA MARCOS; PISSINIS D. E.; A A. RUBERT; E. PRIETO; FERNANDEZ LORENZO DE MELE, M.

ELECTROCHIMICA ACTA

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2016 p. 289 - 297

0013-4686

p { margin-bottom: 0.25cm; line-height: 120%; }Acomparative study of the electropolymerization of two naturalphenolic isomers, carvacrol (Carv) and thymol (TOH) on copper wasmade. They are components of Origanum vulgare and Thymus vulgarisessential oils. Polymerized layers (polyCarv and polyTOH) wereattained by cyclic voltammetry (CV). Electrochemical techniquescomplemented by ATR-FTIR, XPS, SEM and AFM surface analyses wereused to evaluate the composition and protective characteristics ofthe films. Results revealed that the electrochemical response inchloride solutions was dissimilar. Copper ions release by polyCarvin chloride solutions was lower than 30% of that obtained with TOHtreatments. PolyCarv is a highly protective, transparent film,remarkably different from the brownish, rough and non-protective filmobtained with TOH. ATR-FTIR results showed that the oxidation ofadsorbed Carv and TOH led to cetonic structures while afterelectropolymerization ether bonds were also found. However, polyCarvand polyTOH showed important differences in ν-OH band. Deconvolutionof C1s signal of XPS spectra led to four contributions with differentproportions for polyCarv and polyTOH. Accordingly, C (ph) -O is 50%of total C1s for polyCarv and 30% for polyTOH. C1s/O1s relationshipswere also different. AFM and SEM observations showed the presence ofround flakes, smaller for polyCarv (5 nm height) than for TOH (35 nmheight).A compact layer was found in case of polyCarv but cauliflower andsticks structures with cracks were found for polyTOH. In summary,results showed the important impact of the molecular structure on thecomposition, structure and protective characteristics of thepolymeric layers. A mechanism is proposed to interpret these results.