# Grafting of (3-Chloropropyl)-Trimethoxy Silane on Halloysite Nanotubes Surface
## 2 Materials and Methods
### Characterization of HNTs-CPTMS  
An elemental analyzer, Perkin Elmer PE 2400 (Perkin Elmer, Waltham, MA, USA), was used to perform elemental analysis of carbon and hydrogen (EA) of the grafted HNT samples which were altered by (3-chloropropyl) trimethoxy silane. The degree of grafting (DG) of HNTs-CPTMS samples were obtained using Equation (1) [20,21]:  
\[DG=\frac{\text{carbon (\%) obtained from }EA}{\text{carbon content (\%) theoretically}} \tag{1}\]  
and the carbon content (%) theoretically can be computed by using Equation (2):  
\[\text{carbon content (\%)theoretically}=\frac{\text{No. of carbon atoms in }CPTMS*No. of moles of CPTMS*12}{\text{No.of }g\text{ of }HNTs+No. of g\text{ of }CPTMS-No. of g\text{ of }alcohol\text{ }eliminated} \tag{2}\]  
The confirmation of the grafting of (3-chloropropyl) trimethoxy silane onto the haloysite nanotube surface was done by characterization of the obtained material using Fourier transform infrared (FT-IR) spectra. Compact FT-IR Spectrometer: ALPHA II (Manufacturer Bruker Optics) was used for FT-IR measurements in the wavenumber range (4500-500) cm\({}^{-1}\) by considering 24 scans, and each scan was 30 s. Thermogravimetric analysis (TGA) was done by a Mettler Toledo device (Columbus, OH, USA) for the unmodified halloysite nanotubes and the greatest modified sample (HNTs-CPTMS). The mass of the sample was measured against time during the temperature changes from 27 to 1000 \({}^{\circ}\)C with a heating rate of 30 \({}^{\circ}\)C min\({}^{-1}\) under a nitrogen flow of 60 mL/min. Scanning electron microscope (SEM) images were obtained by using a Carl Zeiss EVO LS 10 Device (Manufacturer: Carl Zeiss NTS, Jena, Germany). It was used to study the morphology of unmodified halloysite nanotubes and the greatest modified sample (HNTs-CPTMS). Carbon tape was used to reduce charging effects. Minimal electron dose was used (3 kV) and the sample distance was 5.1 mm.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Molar Ratio** & **Solvent** & **Catalyst** & **T/\({}^{\circ}\)C** & **Refluxing** & **Content, \%** & **Degree of** \\ (HNTs/CPTMS/ H\({}_{2}\)O)** & & & **Time (h)** & **C** & **H** & **Grafting (\%)** \\ \hline
1:1:0 & 20 mL toluene & 110 & 4 & 2.17 & 1.83 & 24.29 \\
1:1:33:0 & 20 mL THF & 66 & 4 & 1.20 & 1.63 & 11 \\
1:1:3 & 20 mL toluene & 110 & 4 & 3.26 & 2.22 & 36.5 \\
1:1:0 & 20 mL ethanol & 79 & 4 & 0.96 & 1.53 & 10.75 \\
1:1:33:0 & 5 mL toluene & 110 & 4 & 1.40 & 1.90 & 12.84 \\
1:1:0 & 20 mL toluene & 110 & 35 & 2.01 & 1.86 & 22.5 \\
1:1:0 & 20 mL toluene & 110 & 48 & 1.89 & 1.97 & 21.16 \\
1:2:0 & 20 mL toluene & 110 & 4 & 2.41 & 2.03 & 17.13 \\
1:2:0 & 17 mL toluene & 110 & 48 & 2.98 & 1.95 & 21.19 \\
1:1:3 & 20 mL toluene & 0.5 mL Et\({}_{3}\)N & 110 & 7 & 4.31 & 2.85 & 48.26 \\
1:1:3 & 20 mL toluene & 0.2 g urea & 110 & 4 & 6.63 & 2.97 & 27.77 \\
1:1:33:0 & 20 mL n-hexane & 1 mL Et\({}_{3}\)N & 69 & 4 & 3.69 & 2.14 & 33.83 \\
1:1.33:0 & 20 mL 1,4 dioxane & 1 mL Et\({}_{3}\)N & 100 & 4 & 2.655 & 2.175 & 24.34 \\
1:1.33:0 & 20 mL n-hexane & 69 & 4 & 1.67 & 1.96 & 15.320 \\
1:1.33:0 & 20 mL 1,4 dioxane & 100 & 4 & 1.56 & 1.86 & 14.3 \\
1:1:3 & 20 mL toluene & 0.5 mL Et\({}_{3}\)N & 110 & 4 & 4.84 & 2.22 & 54.19 \\
1:1:3 & 40 mL toluene & 0.5 mL Et\({}_{3}\)N + 0.5 & & 4.55 & 2.13 & 50.95 \\
1:1:3 & 20 mL toluene & mL NH\({}_{4}\)OH & 110 & 4 & 7.26 & 2.55 & 81.35 \\
1:1:0 & 20 mL toluene & 3 drops (EtO)\({}_{4}\)Ti & 110 & 4 & 3.17 & 2.1 & 35.49 \\
1:1:3 & 20 mL toluene & 0.5 mL Et\({}_{3}\)N + 0.138 & & 4 & 4.52 & 2.24 & 50.67 \\  & & mL NH\({}_{4}\)OH & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: The different parameters which were used for the grafting process and the results obtained from elemental analysis.