Role of the cationic headgroup to conformational changes undergone by shorter alkyl chain surfactant and water molecules at the air-liquid interface

Md Rubel Khan, Uvinduni I. Premadasa, Katherine Leslee A. Cimatu

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

Hypothesis: Surfactants are commonly used as corrosion inhibitors for oil-and-gas pipelines. The alkyl chain of surfactants and their overall conformation contributes to the adsorption, flotation, and foam separation in the inhibition process. We hypothesize that the conformation of shorter alkyl chains and chemical nature of surfactants has an effect on the ordering of water molecules at the air-water interface which is not yet well understood. Experiments: Alkyl (C4, C6, C8, C10, and C12) dimethylbenzylammonium bromides (Quats) were synthesized. Aqueous solutions at 0% and with different salt concentrations were studied at the air-liquid interface using sum frequency generation spectroscopy. Surface tension and pH measurement were also conducted for comparison. Findings: Surfactant solutions at 0%, 1%, and 10% salt showed a zigzag trend for the number of gauche defects. At 0% salt, an increasing trend of OH band intensity at 3182 cm−1 was observed from C6 to C12 SFG spectra. Yet, C4 showed a more prominent SFG signal from strongly hydrogen-bonded water molecules compared to C6. The headgroup's chemical nature was found to play a role in the ordering of water molecules for a C4 alkyl chain length. The OH band intensity decreases with increasing ionic strength.

Original languageEnglish
Pages (from-to)221-233
Number of pages13
JournalJournal of Colloid and Interface Science
Volume568
DOIs
StatePublished - May 15 2020
Externally publishedYes

Funding

The authors acknowledge with sincere gratitude Drs. David Young, Marc Singer, Srdjan Nesic, Sumit Sharma and graduate student, Negar Moradighadi from the Institute of Corrosion and Multiphase Technology (ICMT) in the Department of Chemical and Biomolecular Engineering at Ohio University for fruitful discussions. This work is supported by a grant from the National Science Foundation (NSF; grant CBET-1705817 ). The authors would like to thank NSF (grants CHE-0947031 and CHE-1338000 ) for the acquisition of the femtosecond laser and nuclear magnetic spectrometer. Additionally, the authors are grateful to the Department of Chemistry and Biochemistry, the College of Arts and Sciences, the Vice President for Research and the Nanoscale and Quantum Phenomena Institute for financial support. The authors acknowledge with sincere gratitude Drs. David Young, Marc Singer, Srdjan Nesic, Sumit Sharma and graduate student, Negar Moradighadi from the Institute of Corrosion and Multiphase Technology (ICMT) in the Department of Chemical and Biomolecular Engineering at Ohio University for fruitful discussions. This work is supported by a grant from the National Science Foundation (NSF; grant CBET-1705817). The authors would like to thank NSF (grants CHE-0947031 and CHE-1338000) for the acquisition of the femtosecond laser and nuclear magnetic spectrometer. Additionally, the authors are grateful to the Department of Chemistry and Biochemistry, the College of Arts and Sciences, the Vice President for Research and the Nanoscale and Quantum Phenomena Institute for financial support.

Keywords

  • Adsorption
  • Air-liquid interface
  • Cationic surfactant
  • Chain length
  • Corrosion
  • Ionic strength
  • SFG spectroscopy
  • Surface tension

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