Influence of lipophilic tail and linker groups on the surface and thermal properties of the synthesized dicationic surfactants for oilfield applications

Aqueous solubility and heat stability are the prerequisites for any surfactant design for oilfield applications. Commercial surfactants, including polyoxyethylene ether, petroleum sulfonate, and alky benzyl sulfonate, face stability issues when encounters with the harsh environment of the reservoir. In this work, we report the synthesis of four dicationic surfactants (DSs) that contain different lipophilic tail and linker groups. Confirmation of the chemical structure was done by the ¹H NMR, ¹³C NMR, FT-IR, and ESI-MS techniques. The prepared DSs displayed good aqueous solubility due to the incorporation of ethoxylates in the backbone of the chemical structure. We examined the influence of the length of the lipophilic tail and linker group utilizing thermal and surface-active properties. The thermal decomposition behavior of DSs was studied using thermal gravimetric analysis. An increase in thermal stability was observed as the length of the lipophilic tail increased. On the other hand, the impact of the increasing length of the linker group seems to be insignificant in thermal stability experiments. Overall, the decomposition temperature of DSs was around 275 °C that is higher than that of reservoir temperature (≥100 °C). An investigation of the relations between critical micellar concentration with chemical structure indicates that increasing length of both lipophilic tail and linker group results in the reduction of critical micellar concentration. However, the effect of increasing length of lipophilic tail found to be more prominent as compared to the linker group. The conducted research revealed that the synthesized DSs are stable at high temperature and exhibited excellent physicochemical properties. The outcome of this research can help for a better understanding of the structure-property relationship and might be useful for the design and development of new material for oilfield applications.