Langmuir films and mechanical properties of polyethyleneglycol fatty acid esters at the air-water interface

Autor(es)

Ortiz-Collazos, Stephanie ^[1] ; Goncalves, Yan M. H. ^{[2, 1]} ; Horta, Bruno A. C. ^[2] ; Picciani, Paulo H. S. ^{[3, 4]} ; Louro, Sonia R. W. ^[5] ; Oliveira, Jr., Osvaldo N. ^[3] ; Pimentel, Andre S. ^[1]

Afiliação do(s) autor(es)

^[1] Pontificia Univ Catolica Rio de Janeiro, Dept Quim, BR-22453900 Rio De Janeiro, RJ - Brazil

^[2] Univ Fed Rio de Janeiro, Inst Quim, BR-21941909 Rio De Janeiro, RJ - Brazil

^[3] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13566590 Sao Carlos, SP - Brazil

^[4] Univ Fed Rio de Janeiro, Inst Macromol Professora Eloisa Mano, BR-21941598 Rio De Janeiro, RJ - Brazil

^[5] Pontificia Univ Catolica Rio de Janeiro, Dept Fis, BR-22453900 Rio De Janeiro, RJ - Brazil

• Tipo de documento: Artigo Científico
• Fonte: COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS; v. 498, p. 50-57, JUN 5 2016.
• Citações Web of Science: 7

Resumo

Polyethylene glycol (PEG) fatty acid esters are used in various industries for their interfacial properties, especially because their emulsifying characteristics can be varied considerably by altering the size of the PEG or fatty acid chains. In this study, we combine experimental surface-specific methods and molecular dynamics (MD) simulations to probe the effects from changing both the hydrophilic and hydrophobic chain sizes. PEG fatty acids containing either stearic or palmitic acid ethoxylated PEG chains of average molecular weight 200 or 400 g mol(-1) (referred to as PEG200 and PEG400, respectively) had critical aggregation concentrations between 30 and 50 mu M, and formed Langmuir films at the air/water interface with compressibility modulus typical of liquid-expanded phases. The area per molecule was consistently smaller for the PEG200 series owing to an increased ordering of the hydrophilic chains inferred from the polarization-modulated infrared reflection absorption (PM-IRRAS) spectra, which was corroborated by MD simulations. With PM-IRRAS and MD simulations, we also noted that the hydrophobic chain had increased order when its size increased from palmitic to stearic acid, which was attributed to a higher melting temperature for longer saturated hydrocarbon chains. (C) 2016 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 13/14262-7 - Filmes nanoestruturados de materiais de interesse biológico
• Beneficiário: Osvaldo Novais de Oliveira Junior
• Modalidade de apoio: Auxílio à Pesquisa - Temático