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Carboxymethyl Chitosan and Its Hydrophobically Modified Derivative as pH-Switchable Emulsifiers
Simo Kalliola1, Eveliina Repo1, Varsha Srivastava1
1Lappeenranta University of Technology , Sammonkatu 12, Mikkeli FI-50130, Finland.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 7, 2018
Summary
Carboxymethyl chitosan (CMChi) and its hydrophobic derivative (h-CMChi) show pH-dependent emulsification of dodecane. Adjusting pH allows for reversible emulsion formation, creating gel-like structures with potential particle interactions.
Area of Science:
- Colloid and Surface Chemistry
- Materials Science
- Biopolymers
Background:
- Chitosan derivatives are explored for emulsification applications.
- Understanding pH and concentration effects is crucial for controlling emulsion properties.
Purpose of the Study:
- To investigate the emulsification capabilities of carboxymethyl chitosan (CMChi) and hydrophobically modified CMChi (h-CMChi).
- To determine the influence of pH and oil/water ratio on emulsion stability and phase inversion.
- To assess the reversibility and structural characteristics of the formed emulsions.
Main Methods:
- Emulsification experiments were conducted using CMChi and h-CMChi solutions.
- The pH was systematically varied between 6 and 10.
- Dodecane/water ratios were adjusted from 0.1 to 2.0.
- Emulsion stability, phase inversion, particle size, and adsorption were analyzed.
Main Results:
- Emulsion stability for CMChi increased with decreasing pH from 10 to 7, shifting phase inversion to higher oil/water ratios.
- At pH 6, CMChi formed nanoparticles (200-300 nm), leading to no phase inversion and maximum emulsification at a 1.2 oil/water ratio.
- h-CMChi exhibited similar pH-dependent behavior, with phase inversion shifted to higher values (pH 7-10) and increased emulsified oil at pH 6 compared to CMChi.
- Adsorbed particle amounts correlated with emulsified oil, and reversible emulsification was achieved via pH adjustment.
- The resulting emulsions were gel-like, indicating particle-particle interactions.
Conclusions:
- Both CMChi and h-CMChi act as effective emulsifiers for dodecane, with properties tunable by pH.
- Hydrophobic modification enhances emulsification capacity, particularly at lower pH.
- The pH-responsive nature allows for reversible emulsion formation and suggests potential applications in controlled release or responsive materials.
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