Hydrophobic but hygroscopic polymer films-identifying interfacial species and understanding water ingress behavior

Erik Hsiao, Anna L. Barnette, Laura C. Bradley, Seong Kim

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

The hydrophobic but hygroscopic nature of polydimethylsiloxane (PDMS) with quaternary ammonium cationic side chains adsorbed on a SiO2 surface was investigated with sum frequency generation vibration spectroscopy (SFG) and attenuated total reflectance infrared spectroscopy (ATR-IR). PDMS with cationic side chains, named cationic polymer lubricant (CPL), forms a self-healing boundary lubrication film on SiO2. It is interesting that CPL films are externally hydrophobic but internally hydrophilic. The comparison of SFG and ATR-IR data revealed that the methyl groups of the PDMS backbone are exposed at the film/air interface and the cationic side groups and counterions are embedded within the film. The hydrophobicity must originate from the surface CH3 groups, while the ionic groups inside the film must be responsible for water uptake. The surface hydrophobicity can alleviate the capillary adhesion while the hygroscopic property enhances the mobility and self-healing capability of the CPL boundary lubrication film.

Original languageEnglish (US)
Pages (from-to)4236-4241
Number of pages6
JournalACS Applied Materials and Interfaces
Volume3
Issue number11
DOIs
StatePublished - Nov 23 2011

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

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