Methyl ester ethoxylates surface properties

Methyl ester ethoxylates and their alcohol ethoxylate counterparts have similar surface properties. Gibbs plot for pure C14 7-mol (no other ethox-ymers except the 7-mol homolog) methyl ester ethoxylate is compared to its pure Ci4 7-mol alcohol ethoxylate counterpart in Fig. 11. The methyl ethoxylate shows a higher CMC and a lower surface tension at the CMC than its alcohol ethoxylate equivalent. This increase in CMC is presumably due to the presence of the ester moiety which adds rigidity and steric constraint to the methyl ester ethoxylate molecule. This would likely reduce the tendency of a molecule to micellize, leading to a slightly higher CMC. 

There is also a difference in dynamic surface properties between methyl ester ethoxylates and alcohol ethoxylates. As shown in Fig. 12 for pure 7-mol homologs, the methyl ester ethoxylate maintains a lower surface tension than its alcohol ethoxylate counterpart as measurements become more dynamic (bubble rate of bubble tensiometer is increased). This suggests that methyl ester ethoxylate is more effective in lowering surface tension (can achieve the same surface tension reduction with a lower surfactant concentration at the interface) and/or it diffuses through aqueous solution at a faster rate. 

Based on the surface property data discussed earlier, methyl ester ethoxylates would be expected to perform similarly to alcohol ethoxylates, which is indeed the case. As shown in Fig. 13, methyl ester ethoxylates are comparable to alcohol ethoxylates, as well as other commonly used surfactants (see Table 1), in their ability to remove soil from fabric. Compositional variables affect the performance of methyl ester ethoxylates and alcohol ethoxylates. Lauryl range and tallow range methyl ester ethoxylates provide the best detergency, while optimal ethylene oxide content appears to depend on soil/ cloth-type (Fig. 14). Interaction with other surfactants also affects detergency performance. As shown in Fig. 15, methyl ester ethoxylates act synergistically with alcohol ethoxylates, while the opposite can be observed with alcohol sulfate and alcohol ether sulfate. 

There is also a difference in dynamic surface properties between methyl ester ethoxylates and alcohol ethoxylates. As shown in Figure 12 for pure 7-mole homologs, the methyl ester ethoxylate maintains a lower surface tension than its al-... 

Based on the surface property data discussed earlier, methyl ester ethoxylates would be expected to perform similarly to alcohol ethoxylates, which is indeed the case. As shown in Figure 13, methyl ester ethoxylates are comparable to al-... 

The impact of unsaturation stems from the increase in rigidity caused by the presence of one or more double bonds to the alkyl chain. Although studies so far show that unsaturation has a relatively low impact on water solubility and viscosity, it has been reported to lower melting points by about 5-10°C [16]. Studies also show (Fig. 20) that unsaturation affects surface properties. Gibbs plots of 14.5-mole ethoxylates produced from hydrogenated and nonhydrogenated Cig is methyl ester show that unsaturation appears to increase surface tension below the CMC. This suggests that unsaturation reduces the hydrophobic character of the methyl ester chain. 

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