# Synthesis of Oligomeric Silicone Surfactant and its Interfacial Properties
## 2 Experimental Design
### Characterization Methods  
The methods for measurement and determination of the properties of OSSF are described in this section. FT-IR. FT-IR was recorded using an FT-IR spectrometer (Thermo Fisher Scientific, Waltham, MA, USA). Measurements were performed by dispersing samples in anhydrous KBr pellets. Determination of molecular weight of VOGO. The average molecular weight of the oligomeric was determined by GPC ([PERSON], model Xevo TQ, Milford, MA, USA) with a refractive index detector using PL gel column (Agilent Technologies Inc., Palo Alto, CA, USA) in tetrahydrofuran with a flow rate of 1 mL/min. The tested mass concentration of OSSF in the THF solution was 0.5%, and its intrinsic viscosity was 1.12 dL/g at 30 \({}^{\circ}\)C. The molecular weights were calculated with a calibration relative to polystyrene standards. Measurement of surface tension. Surface tension measurements were performed using an interfacial tensiometer Sigma 701 (KSV, Helsinki, Finland). A dynamic Wilhelmy plate method was used to perform each series of measurements. The mass concentration was manually changed with microsyringes. Each value was the average of the three measurements. In addition, critical micelle mass concentration was determined by the cross point of the two lines before and after critical micelle mass concentration on the \(\gamma\)-p\({}_{\rm n}\) curve. Measurement of thermal stability. OSSF solutions with a pH value adjusted to approximately 9-10 using a NaOH solution (10.00 M, H\({}_{2}\)O) were first heat-rolled for 16 h in a roller oven (Haian Petroleum Scientific Research Instrument, Jianngsu, China), and then the surface tension of the heat-rolled solutions was measured at 25 \({}^{\circ}\)C.  
Measurement of salt tolerance. OSSF was added to the NaCl, KCl, and CaCl\({}_{2}\) solutions, respectively. The solution was first stirred well and then allowed to stand for 24 h at room temperature indoors. Subsequently, the surface tension of the solution was measured at 25 \({}^{\circ}\)C.  
Measurement of the size and distribution of micelles. The size and distribution of micelles in the OSSF solutions were measured using a laser nanometer analyzer (Malvern Instruments, Malvern, UK) at 25 \({}^{\circ}\)C.  
Core preparation. The cores were prepared in the following steps: first, the cores were cut into thick slices (about half a centimeter). OSSF was dissolved in water (OSSF solution). Then, the cores slices were cleaned with water and evacuated for several hours in a vacuum chamber. Next, the slices were steeped in 100 mL of the OSSF solution, whose pH value was adjusted to approximately 9 to 10 using a NaOH solution (10.00 M, H\({}_{2}\)O). The mixture was then heat-rolled for 8 h at 150 \({}^{\circ}\)C in a roller oven. Finally, the cores slices were dried in a vacuum drier at 150 \({}^{\circ}\)C for 4 h and then cooled to 25 \({}^{\circ}\)C.  
Contact angle measurement and surface energy determination. Contact angle was formed between the plane tangent to the surface of the cores and liquids (water and ethylene glycol) at the wetting perimeter. It was measured by a JC200D3 contact angle meter (Zhongchen Digital Technology Equipment, Shanghai, China) and calculated using the five-point fitting method. Following the Owens-Wendt geometric theory, the surface energy (\(\gamma_{s}\)) of the cores was calculated by Equations (1) and (2) [21; 22]:  
\[(1+\cos\theta)\gamma_{L}=2\Big{(}\gamma_{s}^{d}\gamma_{L}^{d}\Big{)}^{1/2}+2 \Big{(}\gamma_{s}^{p}\gamma_{L}^{p}\Big{)}^{1/2} \tag{1}\]  
\[\gamma_{s}=\gamma_{s}^{d}+\gamma_{s}^{p} \tag{2}\]  
where \(\theta\) (\({}^{\circ}\)) is the contact angle between the core surface and liquid; \(\gamma_{L}\) (N/m) is the free energy of the liquid surface; \(\gamma_{S}\) (N/m) is the free energy of the core surface; \(\gamma_{s}^{d}\) (N/m) is the core dispersion force; \(\gamma_{L}^{d}\) (N/m) is the liquid dispersion force; \(\gamma_{s}^{p}\) (N/m) is the core polar force; and \(\gamma_{L}^{p}\) (N/m) is the liquid polar force. Measurement of adsorption isotherms.