Calcite Surfaces Modified with Carboxylic Acids (C₂ to C₁₈): Layer Organization, Wettability, Stability, and...

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Understanding mineral surface interactions with modifiers is crucial for controlling mineral filler production and applications.
• Amphiphilic surface modification agents play a key role in tailoring the properties of mineral fillers.

Purpose of the Study:

• To precisely control and investigate the formation of carboxylic acid layers on calcite surfaces via vapor deposition.
• To analyze the properties and molecular structure of these modified surfaces.

Main Methods:

• Vapor deposition for controlled layer formation.
• Surface-sensitive techniques including atomic force microscopy (AFM), contact angle measurements, angle resolved X-ray photoelectron spectroscopy (XPS), and vibrational sum-frequency spectroscopy (VSFS).

Main Results:

• Achieved low wettability using long-chain carboxylic acids like stearic acid.
• Observed the growth of patchy layers into homogeneous monolayers with increasing vapor exposure.
• Demonstrated increased layer stability with longer hydrocarbon chains and higher packing density.
• Confirmed all-trans conformation and anisotropic distribution of alkyl chains, forming epitaxial monolayers.
• Identified interaction of carboxylic acid headgroups with the calcite surface in both protonated and deprotonated states.

Conclusions:

• Vapor deposition offers precise control over carboxylic acid layer formation on calcite.
• The study provides molecular-level understanding of surface modification for mineral fillers.
• Results enhance control over mineral filler production and applications through tailored surface properties.