Abstract
In this study, we show a strategy of formulating highly and fully water dilutable sustainable microemulsions with dibasic esters as oil pseudophase. First, di-Me or di-Et DBEs with different nos. of carbon atoms between the ester functions (succinate C2, glutarate C3, and adipate C4) or DBE blends and a surfactant-cosurfactant melt consisting of sodium dodecylsulfate and 1-pentanol with a const. ...
Abstract
In this study, we show a strategy of formulating highly and fully water dilutable sustainable microemulsions with dibasic esters as oil pseudophase. First, di-Me or di-Et DBEs with different nos. of carbon atoms between the ester functions (succinate C2, glutarate C3, and adipate C4) or DBE blends and a surfactant-cosurfactant melt consisting of sodium dodecylsulfate and 1-pentanol with a const. wt. ratio of 1:2 are used. We investigated the extent of the realms of existence of homogeneous single phases and represent them with pseudoternary phase diagrams. It was possible to formulate fully water dilutable oil-rich single-phase solns. with all di-Me dibasic esters but not with the di-Et ones. By mixing the most hydrophilic dibasic ester with the most hydrophobic one with a mass ratio of 3:2, a fully water dilutable oil-rich single phase could also be obtained. The presence of water-in-oil, bicontinuous, and oil-in-water microemulsions was checked with cond. and dynamic light scattering measurements. A percolative behavior was obsd. for all systems. Second, to formulate green and sustainable microemulsions, we replaced successively sodium dodecylsulfate by sodium oleate and 1-pentanol by ethanol or 1,5-pentanediol. With sodium oleate, highly water dilutable microemulsions were obtained. Homogeneous and translucid samples in the very dild. area turned bluish after several days. Longtime pH measurements of systems contg. sodium oleate showed no degrdn. of the dibasic esters at low water content and a rapid hydrolysis at high water content with 1-pentanol as cosurfactant. Always in presence of sodium oleate, the substitution of 1-pentanol by ethanol or 1,5-pentanediol drives the system to microemulsions showing an instability of the ester at any water concns. Thermal gravimetric anal. measurements at 32 °C for 24 h confirmed a rapid evapn. of ethanol and water and negligible evapn. of 1,5-pentanediol. [on SciFinder(R)]
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