# Synthesis, characterization and surface properties of an organosilicon surfactant

## TL;DR

This study creates and tests a new organosilicon surfactant with high surface activity and thermal stability as an alternative to fluorocarbon surfactants.

## Contribution

A novel organosilicon surfactant with hydroxyl quaternary ammonium salt is synthesized and characterized for high performance and thermal stability.

## Key findings

- The surfactant has a critical micelle concentration of 9.10 mmol/L and surface tension of 22.81 mN/m.
- When combined with sodium hexanesulfonate, the CMC and surface tension decrease significantly.
- Micellization is a spontaneous, entropy-driven process confirmed by thermodynamic analysis.

## Abstract

In order to explore alternative substances for traditional fluorocarbon surfactants while maintaining high surface activity, this study successfully designed and synthesized an organosilicon surfactant (SiCH) containing a hydroxyl quaternary ammonium salt. Its molecular structure was confirmed by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and mass spectrometry (MS). This surfactant exhibits excellent thermal stability, with an initial decomposition temperature of 167 °C and minimal residue at high temperatures. The critical micelle concentration (CMC) and the surface tension (γ
CMC) at the CMC of SiCH are 9.10 mmol/L and 22.81 mN/m, respectively. The organosilicon surfactant–sodium hexanesulfonate (SiCH-SHS) exhibits significant synergistic effect, reducing the CMC and γ
CMC to 6.88 mmol/L and 21.03 mN/m respectively. The area occupied by a single surfactant molecule at the air/water interface (A
S) of the SiCH-SHS is 1.24 nm2, and the pC20 is 2.91. The size distribution of SiCH is unimodal, and they can self-assemble into non-uniform sized spheroidal aggregates (122–295 nm). Moreover, the thermodynamic process of micelle formation of the surfactant was studied through conductivity tests conducted at different temperatures (298.15
−
303.15 K). Thermodynamic analysis indicates that micellization is a spontaneous (
ΔGm0
<0), entropy-driven process.