MilliporeSigma
  • The Cloud Point of Alkyl Ethoxylates and Its Prediction with the Hydrophilic-Lipophilic Difference (HLD) Framework.

The Cloud Point of Alkyl Ethoxylates and Its Prediction with the Hydrophilic-Lipophilic Difference (HLD) Framework.

Langmuir : the ACS journal of surfaces and colloids (2015-10-16)
Silvia Zarate-Muñoz, Americo Boza Troncoso, Edgar Acosta
ABSTRACT

The hydrophobicity of surfactants has been described through different concepts used to guide the formulation of surfactant-water (SW) and surfactant-oil-water (SOW) systems. An integrated framework of hydrophobicity indicators could provide a complete tool for surfactant characterization, and insights on how their relationship may influence the overall phase behavior of the system. The hydrophilic-lipophilic difference (HLD) and the characteristic curvature (Cc) parameter, included in the HLD, have been shown to correlate with different hydrophobicity indicators including the hydrophilic-lipophilic balance (HLB), packing factor (Pf), phase inversion temperature (PIT), spontaneous curvature (Ho), surfactant partition (K(o-w)), and the critical micelle concentration (CMC). This work aims to investigate whether the HLD can further describe a concomitant hydrophobicity parameter, the cloud point (CP) of alkyl ethoxylates. After applying group contribution models to calculate the Cc of monodisperse (pure) nonionic alkyl ethoxylates, a linear correlation between the calculated Cc and the CP was observed for pure surfactants with 8 ethylene oxide (EO) units or less. Furthermore, using an apparent equivalent alkane carbon number (EACN) to represent the hydrophobicity of the micelle core, the HLD equation was capable of predicting cloud point temperatures of pure alkyl ethoxylates, typically within 5 °C. Polydisperse surfactants did not follow the linear CP-Cc correlation found for pure surfactants. After treating polydisperse samples using a liquid-liquid extraction procedure used to remove the most hydrophobic components in the mixture, the resulting treated surfactants fell in the correlation line of pure alkyl ethoxylates. A closer look at the partition behavior of these treated surfactants showed that their partition, Cc and cloud point are dominated by the most abundant ethoxymers in the treated surfactant. The HLD also predicted the cloud point depression of treated surfactants with increasing sodium chloride concentration. This work shows how the HLD framework could be extended to predict the behavior of SW systems.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Decahydronaphthalene, mixture of cis + trans, anhydrous, ≥99%
Sigma-Aldrich
Methanol solution, NMR reference standard, 4% in methanol-d4 (99.8 atom % D), NMR tube size 3 mm × 8 in.
Sigma-Aldrich
Decahydronaphthalene, mixture of cis + trans, reagent grade, 98%
Supelco
Methanol solution, contains 0.10 % (v/v) formic acid, UHPLC, suitable for mass spectrometry (MS), ≥99.5%
Sigma-Aldrich
Glycerol, for molecular biology, ≥99.0%
Sigma-Aldrich
Glycerol, BioXtra, ≥99% (GC)
Sigma-Aldrich
Glycerol, ≥99.5%
Sigma-Aldrich
Glycerol solution, 83.5-89.5% (T)
Sigma-Aldrich
Glycerol, BioUltra, for molecular biology, anhydrous, ≥99.5% (GC)
Sigma-Aldrich
Glycerin, meets USP testing specifications
Sigma-Aldrich
Cyclohexane, anhydrous, 99.5%
Sigma-Aldrich
Methanol, ACS reagent, ≥99.8%
Sigma-Aldrich
Hexane, ReagentPlus®, ≥99%
Sigma-Aldrich
Cyclohexane, ACS reagent, ≥99%
Sigma-Aldrich
Methanol, HPLC Plus, ≥99.9%, poly-coated bottles
Sigma-Aldrich
Glycerol, puriss., anhydrous, 99.0-101.0% (alkalimetric)
Sigma-Aldrich
Glycerol solution, puriss., meets analytical specification of Ph. Eur., BP, 84-88%
Sigma-Aldrich
Methanol, Laboratory Reagent, ≥99.6%
Sigma-Aldrich
Hexane, Laboratory Reagent, ≥95%
Sigma-Aldrich
Cyclohexane, ACS reagent, ≥99%
Sigma-Aldrich
Methanol, Absolute - Acetone free
Sigma-Aldrich
Methanol, ACS spectrophotometric grade, ≥99.9%
Sigma-Aldrich
Glycerol, ReagentPlus®, ≥99.0% (GC)
Sigma-Aldrich
Methanol, ACS reagent, ≥99.8%
Sigma-Aldrich
Cyclohexane, Laboratory Reagent, ≥99.8%
Sigma-Aldrich
Methanol, ACS reagent, ≥99.8%
Sigma-Aldrich
Hexane, puriss. p.a., ACS reagent, reag. Ph. Eur., ≥99% (GC)
Sigma-Aldrich
Methanol, BioReagent, ≥99.93%
Sigma-Aldrich
Methanol, puriss., meets analytical specification of Ph Eur, ≥99.7% (GC)
Sigma-Aldrich
Glycerol, puriss. p.a., ACS reagent, anhydrous, dist., ≥99.5% (GC)