Sol/gel transition of oil/water microemulsions controlled by surface grafted triblock copolymer dodecyl-PEO-dodecyl: molecular dynamics simulations with experimentally validated interaction potential.

We studied a large range of identical spherical oil/water microemulsion (O/W-MI) volume fractions. The O/W-MIs are stabilized by cetylpyridinium chloride ionic surfactant (CpCl) and octanol cosurfactant and dispersed in salt water. We grafted different numbers of dodecyl-(polyEthylene oxide)-dodecyl triblock copolymer that we note ((D-PEO-D)), where varies from 0 to 12. We accomplished the grafting process by replacing a small amount of CpCl and octanol with the appropriate (D-PEO-D). The aim is to determine the interaction/structure relationship of the covered microemulsions. Precisely, we are interested in a quantitative investigation of the influence of volume fraction , temperature (), and (D-PEO-D) on the microemulsion sol/gel transition. To this end, we first study the uncoated microemulsion structure depending only on . Second, we determine the coated microemulsions structure as a function of (D-PEO-D) for different . Third, we examine the effect of temperature on the uncoated and coated microemulsion. We show that the sol/gel transition is controlled by the three main parameters, , , and (D-PEO-D). Accordingly, the uncoated microemulsion sol/gel transition, at ambient temperature, occurred for ≃ 33.65%. By increasing , the O/W-MIs show a glass state, which occurs, along with the gel state, at ≃ 37% and arises clearly at ≃ 60%. The coated O/W-MI sol/gel transition is found to be linearly dependent on (D-PEO-D) and takes place for ≃ 26.5% for (D-PEO-D) = 12. Ordinarily, the decrease in temperature leads to gel formation of microemulsions for low . Additionally, in this work, we found that the gelation temperature increases linearly with (D-PEO-D). Thus, the parameter (D-PEO-D) can control the sol/gel transition of the O/W-MIs at ambient temperature and moderate .