## 3 Results and Discussion
### 3.2. Gelation in Organic Solvents
Compound **8c** showed excellent gelation behavior with a variety of organic solvents (toluene, THF, acetone, dichloromethane, _n_-butanol and methanol) at concentrations ranging from 0.5-3 mg/mL, and formed stable gels in several instances. Table 1 summarizes some of the best conditions for gel formation, and the minimum concentration of gelator where stable gels were obtained. In general, we conclude that the partially fluorinated urea-amide derivatives (**7a-c** and **8a-c**) are better gelators than the corresponding amide systems (**5a-c** and **6a-c**), possibly due to the ability of the urea moieties to form directional hydrogen bonds. In order to further understand the influence of amide groups in the gelation ability of these urea-amide systems, we synthesized the corresponding urea-ester derivatives, which in general did not show any gelation properties under the same gelation conditions as the urea-amide systems. For example, urea-ester derivatives **9** and **10** (comparable to urea-amides **7a** and **8b**) were synthesized via the esterification of \(N\)-Boc-\(\beta\)-alanine and \(N\)-Boc-L-aspartic acid with \(n\)-octanol, followed by deprotection and reaction of the amine with \(1H,1H,2H,2H\)-perfluorooctyl isocyanate (Figure 3). Both **9** and **10** were oils and failed to gel in common organic solvents, indicating amide functionalities are desired in addition to the urea group in the backbone of these partially fluorinated compounds to obtain good gelation properties. \begin{table}
\begin{tabular}{|l|l|l|l|} \hline  & \multicolumn{2}{l|}{**Gelation Conditions**} & \\ \cline{2-3}  & **Gelator** & **Concentration** & **Solvent** & \\
**Compound** & **mg/mL** & & & **Appearance b** \\ \hline
**5a** & 2,3 & Acetone & Partial Gel \\  & 3–4 & _n_-Butanol & Partial Gel \\
**5b** & 3 & Acetone & Partial Gel \\
**5c** & 0.5–4 & Acetone, THF, CH\({}_{2}\)Cl\({}_{2}\), & Clear Solution or \\  & & _n_-Butanol, hexane, methanol & Precipitate \\
**6a** & 3 a & Acetone & Opaque Gel \\  & 4 a & _n_-Butanol & Opaque Gel \\
**6b** & 2 a & CH\({}_{2}\)Cl\({}_{2}\) & Hazy Gel \\  & 3 a & Acetone & Hazy Gel \\
**6c** & 2 a & Acetone, methanol & Opaque Gel \\
**7a** & 2 a & THF or acetone & Opaque Gel \\  & 3 & _n_-Butanol & Partial Gel \\
**7b** & 3 a & Acetone or THF & Opaque Gel \\
**7c** & 2 & CH\({}_{2}\)Cl\({}_{2}\) & Partial Gel \\
**8a** & 2 a & Acetone & Opaque Gel \\  & 3 a & CH\({}_{2}\)Cl\({}_{2}\) & Hazy Gel \\  & 2–4 & THF, _n_-butanol & Partial Gel \\
**8b** & 2 a & CH\({}_{2}\)Cl\({}_{2}\) & Opaque Gel \\  & 3 a & Acetone & Hazy Gel \\
**8c** & 0.5 a & 1, 2, 3 & Acetone \\  & 0.5 a & CH\({}_{2}\)Cl\({}_{2}\) & Transparent Gel \\  & 2 & THF & Opaque Gel \\ \hline \end{tabular}  
* Minimum gel concentration for stable gel formation; b Hazy = partially transparent, solid gel. Transparent = completely transparent, solid gel. Opaque = solid gel, not transparent. Partial gel = solid gel with some movement. Precipitate = phase- separated liquid, with solid particles.  
\end{table} 
Table 1: Gelation properties of partially fluorinated amides (**5a–c**, **6a–c**) and urea-amides (**7a–c**, **8a–c**).