New Carbamates and Ureas: Comparative Ability to Gel Organic Solvents

Abstract

Two series of novel amphiphilic compounds were synthesized based on carbamates and ureas structures, using a modification of the synthesis methods reported by bibliography. The compounds were tested for organic solvent removal in a model wastewater. The lipophilic group of all compounds was a hexadecyl chain, while the hydrophilic substituent was changed with the same modifications in both series. The structures were confirmed by FT-IR, NMR, molecular dynamic simulation and HR-MS and their ability to gel organic solvents were compared. The SEM images showed the ureas had a greater ability to gel organic solvents than the carbamates and formed robust supramolecular networks, with surfaces of highly interwoven fibrillar spheres. The carbamates produced corrugated and smooth surfaces. The determination of the minimum gelation concentration demonstrated that a smaller quantity of the ureas (compared to the carbamates, measured as the weight percentage) was required to gel each solvent. This advantage of the ureas was attributed to their additional N-H bond, which is the only structural difference between the two types of compounds, and their structures were corroborated by molecular dynamic simulation. The formation of weak gels was demonstrated by rheological characterization, and they demonstrated to be good candidates for the removal organic solvents.

Topochemical Synthesis of Conducting Radical Polymers

“…It is common for urea-or carbamate-containing hydrogen-bonded synthons to lead to self-assembly and, thus, gel formation in most of these systems. 53 Therefore, as expected, the diphenyl-DA monomer formed a gel in various organic solvents, including in benzene, toluene, and chloroform with critical gelation concentrations (CGC) of 0.5, 0.4, and 1.75% (by weight), respectively (Figure 2a and Figure S1), indicating that less polar and/or nonpolar aromatic solvents stabilize the assembly in gel state. This shows that the diphenyl-DA monomer can be considered as a supergelator (when CGC < 1%) for the nonpolar aromatic solvents.…”

“…The propargyl carbamate was then coupled by treatment with CuI and TMEDA via a Glaser–Hay coupling to yield the corresponding diphenyl-DA or di-TEMPO–DA. It is common for urea- or carbamate-containing hydrogen-bonded synthons to lead to self-assembly and, thus, gel formation in most of these systems . Therefore, as expected, the diphenyl-DA monomer formed a gel in various organic solvents, including in benzene, toluene, and chloroform with critical gelation concentrations (CGC) of 0.5, 0.4, and 1.75% (by weight), respectively (Figure a and Figure S1), indicating that less polar and/or nonpolar aromatic solvents stabilize the assembly in gel state.…”