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Published on: March 29, 2018
Forces between Two Glass Surfaces with Adsorbed Hexadecyltrimethylammonium Salicylate
1Research Center for Materials Science and Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan, and School of Chemistry, University of Sydney, Sydney, New South Wales 2006, Australia.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 24, 2009
Summary
Hexadecyltrimethylammonium salicylate (C(16)TASal) layers on glass beads exhibit hydrophobic attraction at low adsorption and electrostatic repulsion at high adsorption. The study reveals strong cohesion between C(16)TASal layers, influencing interactions during adsorption and desorption processes.
Area of Science:
- Surface Chemistry
- Colloid Science
- Materials Science
Background:
- Understanding the interfacial behavior of surfactants like hexadecyltrimethylammonium salicylate (C(16)TASal) is crucial for various applications.
- Investigating the interplay between hydrophobic and electrostatic forces in surfactant layers provides insights into their self-assembly and interaction mechanisms.
Purpose of the Study:
- To measure forces between C(16)TASal layers adsorbed on glass beads.
- To elucidate the influence of adsorption density, critical micelle concentration (cmc), and salt concentration on interaction forces.
- To characterize the phenomena of jump-in, step-in, and pull-off during surface interactions.
Main Methods:
- Force measurements were conducted on C(16)TASal layers adsorbed onto glass beads.
- Experiments involved varying C(16)TASal concentrations relative to its cmc (0.15 mM).
- The effect of varying sodium salicylate (NaSal) concentrations on interaction forces was investigated.
Main Results:
- Hydrophobic attraction dominated at low C(16)TASal adsorption, while electrostatic repulsion occurred at higher adsorption.
- Jump-in, step-in, and pull-off phenomena were observed, characteristic of surfactant layer behavior and strong molecular cohesion.
- Increasing NaSal concentration reduced electrostatic repulsion due to shielding, with force wall height peaking at 0.01 M NaSal and interlocking minimized at 0.1 M NaSal.
Conclusions:
- The study demonstrates significant cohesion within adsorbed C(16)TASal layers, independent of electrostatic repulsion effects.
- The observed force profiles and phenomena are indicative of complex interfacial interactions governed by both surfactant adsorption and solution conditions.
- Findings highlight the importance of surfactant concentration and ionic strength in controlling interfacial forces and layer stability.
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