Relationships between the physical properties and biodegradability and bacteria toxicity of fatty acid-based ionic liquids

Abstract

This work is focused on the correlation between several physical properties (kinematic viscosity, viscosity index, refractive index, density and water solubility) and biodegradability and bacteria toxicity of a family of ionic liquids synthesized from fatty acids as anion precursor (FAILs): methyltrioctylammonium hexanoate [N 8881 ][C 6:0 ], methyltrioctylammonium octanoate [N 8881 ][C 8:0 ], methyltrioctylammonium laurate [N 8881 ][C 12:0 ], methyltrioctylammonium palmitate [N 8881 ][C 16:0 ], methyltrioctylammonium stearate [N 8881 ][C 18:0 ] and methyltrioctylammonium oleate [N 8881 ][C 18:1 ]. To that end, new values of these physical properties, biodegradability and bacteria toxicity were determined, although literature data for the [N 8881 ][C 8:0 ], [N 8881 ][C 12:0 ] and [N 8881 ][C 16:0 ] FAILs were also needed. It was found a good linear relationship (r 2 > 0.90) between the biodegradability index (BOD 5 /COD) and the logarithm of kinematic viscosity, refractive index and water solubility for the saturated FAILs. Besides, the toxicity on both Vibrio fischeri and Escherichia Coli can be successfully predicted using the logarithm of kinematic viscosity and viscosity index. Therefore, kinematic viscosity, which is an essential parameter for a lubricant, is the most promising physical property to estimate both biodegradability and bacteria toxicity of a family of ionic liquids. The double bond in the structure of the unsaturated FAIL ([N 8881 ][C 18:1 ]) is responsible for the worsening of the linear dependence between physical and environmental properties.

Two fatty acid anion-based ionic liquids - part I: Physicochemical properties and tribological behavior as neat lubricants

“…In addition, Yu et al [63] observed that longer alkyl chain makes the salt more viscous because of an increase in van der Waals interactions. However, both properties decrease in this research with the increase of the alkyl chain length of the anion, similarly to other FAILs employed in previous research works [64][65][66][67]. The differences in viscosity behavior could be explained in a similar way that what happen with surface tension [46].…”

“…, the[N 6,6,6,6 ][C 16:0 ] IL has the highest viscosity index, showing that an increase in the alkyl chain length improves the lubrication potential of the FAIL[64,67].…”

pH-Responsive Nanostructures Based on Surface Active Fatty Acid-Protic Ionic Liquids for Imiquimod Delivery in Skin Cancer Topical Therapy

“…Furthermore, the cation and/or anion amphiphilic nature can be finely balanced to trigger the self-assembling behavior of ILs [ 40 , 41 , 42 , 43 , 44 ]. In this framework, fatty acids raised remarkable interest as building blocks for ILs containing natural hydrophobic tails [ 45 , 46 , 47 , 48 , 49 , 50 ] and such materials were investigated in pharmaceutical applications [ 42 , 51 , 52 , 53 , 54 ]. An intriguing subclass of ILs is that of the so-called protic ionic liquids (PILs), which are easily prepared by reacting a Brønsted acid and a Brønsted base [ 55 , 56 ].…”

Ionic Liquids as High-Performance Lubricants and Lubricant Additives

“…To understand the correlation between the molecular structure and biodegradability and toxicity of ILs is essential to design green IL lubricants. Nowadays, many experimental studies [21,33] have been conducted to evaluate the environmental impact of ILs. In addition, computational approaches [34][35][36] are also employed to assess their toxicity.…”