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Adsorption and Self-Assembly of Surfactants at Air-Liquid and Liquid-Metal Interfaces Studied by Sum Frequency Generation (SFG) Spectroscopy

Khan, Md Rubel
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1620212735093219

Abstract Details

2021, Doctor of Philosophy (PhD), Ohio University, Chemistry and Biochemistry (Arts and Sciences).
Surfactants are extensively used as corrosion inhibitors to mitigate the internal corrosion of oil and gas pipelines. Surfactants are amphiphilic, consisting of both polar headgroup and nonpolar tail group. The arrangement of headgroup and tail group governs the adsorption as well as the inhibition process. In this dissertation, we explore the conformation of the short alkyl chain length and the nature of the headgroup of surfactants that affects on the ordering of interfacial water molecules. Quaternary ammonium compound (Quat) with five different chain lengths were synthesized via Quaternization of primary amine with Bromo alkane. Imidazolines with five different chain lengths were synthesized from fatty acid or aldehyde and amine. Aqueous solutions of Quat at different ionic strengths were studied by surface and interface selective sum frequency generation spectroscopy technique at the air-liquid interface. We found that Quat solutions containing 0%, 1%, and 10% NaCl salt showed no clear trend for the number of gauche defect as a function of ionic strength. In general, the longer chain surfactants were found to have more ordered interfacial water molecules compared to the shorter ones at the air-liquid interface. The SFG results were correlated with the surface tension measurements and pH values. As a continuation, the self-assembly of surfactant was also studied in-situ at the liquid-metal interface by SFG spectroscopy. A self-assembled monolayer at liquid-metal interface is vital for corrosion, catalysis, and electrochemical reactions. We probed the adsorption and self-assembly of Quats at the liquid-metal interface by SFG spectroscopy without applying any external potential. This provides direct evidence of the effect of alkyl chain length of surfactants in the conformational changes of an adsorbed monolayer on the liquid-metal interface. We found that longer chain surfactant forms highly ordered monolayer due to the strong tail-tail interaction. On the other hand, shorter chain surfactant forms less ordered monolayer due to weak tail-tail interaction.
Katherine Cimatu, Dr. (Advisor)
Jixin Chen, Dr. (Committee Member)
Micheal Held, Dr. (Committee Member)
John Staser, Dr. (Committee Member)
192 p.
Chemistry; Physical Chemistry; Physics
Corrosion; Surfactant; Spectroscopy; SFG; Interface; Surface; Nonlinear; Optics; and Ultrafast

Recommended Citations

Citations

  • Khan, M. R. (2021). Adsorption and Self-Assembly of Surfactants at Air-Liquid and Liquid-Metal Interfaces Studied by Sum Frequency Generation (SFG) Spectroscopy [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1620212735093219

    APA Style (7th edition)

  • Khan, Md Rubel. Adsorption and Self-Assembly of Surfactants at Air-Liquid and Liquid-Metal Interfaces Studied by Sum Frequency Generation (SFG) Spectroscopy. 2021. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1620212735093219.

    MLA Style (8th edition)

  • Khan, Md Rubel. "Adsorption and Self-Assembly of Surfactants at Air-Liquid and Liquid-Metal Interfaces Studied by Sum Frequency Generation (SFG) Spectroscopy." Doctoral dissertation, Ohio University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1620212735093219

    Chicago Manual of Style (17th edition)

ohiou1620212735093219
187
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This open access ETD is published by Ohio University and OhioLINK.