Effect of Hydrophobic Tails on Orientation of SDS and SDOSS Surfactants Near the Film-Air Interface of Sty/n-BA Copolymer Latex Films

Document Type

Article

Publication Date

10-30-2001

Department

Polymers and High Performance Materials

Abstract

This study focuses on the effect of sodium dioctylsulfosuccinate (SDOSS) and sodium dodecyl sulfate (SDS) surfactants on mobility and conformational behavior in styrene/n-butyl acrylate/methacrylic acid (Sty/n-BA/MAA) copolymer latex films. Because of similar hydrophilicity of SO3-Na+ groups but differences in hydrophobic tails, SDOSS and SDS are examined near the surface for coalesced Sty/n-BA/MAA latex films. These studies show that the presence of hydrophilic SO3-Na+ groups and hydrophobic entities represented by two C8H17 tails in SDOSS and one C12H25 hydrophobic group in SDS significantly affects the magnitude of surfactant-latex matrix interactions. Furthermore, not only the surfactant conformational behavior near the film-air interface is affected but also the magnitude of the interactions of hydrophilic SO3-Na+ groups in SDOSS with H2O and COOH groups of Sty/n-BA/MAA is substantially different from its SDS counterpart. This is demonstrated by the splitting of the S-O band when hydrophilic SDOSS groups interact with H2O and COOH groups of the polymer matrix. Attenuated total reflectance Fourier transform infrared polarization studies and energy calculations using a semiempirical quantum-mechanical approach indicate that hydrophobic chains take preferentially perpendicular orientations to the latex film surface, whereas hydrophilic, SO3-Na+ groups are preferentially parallel. Semiquantitative dichroic ratio analysis revealed that the degree of orientation of the SO3-Na+ groups is also affected by hydrophobic entities.

Publication Title

Langmuir

Volume

17

Issue

22

First Page

6961

Last Page

6967

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