Here, a precipitous drop of this ratio occurs as the concentration of DDA is increased from 2 ppm to about 30 ppm, beyond which the ratio changes only slowly. These results are consistent with the scenario presented above that DDA engages in H-bonding interaction with Brij-35, and that a critical percolation threshold exists in such type of co-operative H-bond formation. More results related these observations can be found in the supplementary materials section (Figure and S4), Surfactants in organic phase. We now explore what happens when the surfactants are dispersed in an organic phase. The UV-spectroscopic studies were conducted with pure DDA, Brij-35 and their mixture in dodecane. Figure shows that the peak corresponding to 100 ppm of DDA, which is centered around 210 nm, is rather broad. This is consistent with the existing literature that carboxylic acid self-associates even in an apolar solvent. One would expect that the probability of dimerization would be rather low if DDA is present at a low concentration (~0.1 ppm). This result is indeed borne out, as Figure shows that the UV peak of the carboxylic acid becomes narrower, and it exhibits a hypsochromic shift, relative to that at 100 ppm concentration. We expected that a similar hypsochromic shift should occur in the aqueous phase as well, provided that its concentration is rather low and if the study is conducted at a low Figure . UV spectra of (A) Dodecanoic acid, (B) Brij-35 and (C) their mixture (50:50) in dodecane in the absence of water. In Figure A, the spectrum obtained for 100 ppm of dodecanoic acid is compared with 0.1 ppm dodecanoic acid in dodecane and that in aqueous phase at pH=3. DPD-MD simulations (D-F) show that dodecanoic acid molecules aggregate at least up to a trimer on its own, while Brij-35 formed dimers (E) under similar conditions. However, together with Brij-35, larger cluster (F) are formed. Panels (G-I); water vapor is infused into the samples. DPD-MD simulations show that inverted emulsion can form with each of the surfactants Panels (J-L), the stability of any of the aggregates can be discerned from the ratios of 𝑡 -𝑎𝑛𝑑 𝑡 + (see text). Color coding are as follows, Red: DDA, Green: Brij-35 and Blue: water. pH (i.e. ~3), where both the H-bonding with the protonated and de-protonated carboxylic acid would be diminished, which is, indeed, borne out in the experimental observation. Figure shows that the UV peak of DDA dispersed in the aqueous phase at pH 3 is rather close to that of DDA in dodecane when its concentration is as low as 0.1 ppm. The mixture of DDA and Brij-35 (50 ppm:50 ppm) in dodecane shows an absorption peak at 210 nm, which is similar to that of 100 ppm DDA in dodecane (compare Figures and). The peak at 205 nm for the Brij-35 (Figure ) virtually disappears in the mixture as it merges with that of the dodecanoic acid.