Butynediol-ethoxylate based trisiloxane: Structural characterization and physico-chemical properties in water

A gemini-type superspreader: Synthesis, spreading behavior and superspreading mechanism

“…Similar results were reported in the literature [29,30]. Notably, these γ CAC values were significantly lower than those of hydrocarbon-based surfactants (30-40 mN/m) [31] and were similar to those reported for other trisiloxane surfactants (20-25 mN/m) [7,8] and fluorosurfactants (18-28 mN/m) [9], which might be attributed to the two hydrophobic trisiloxane groups of the gemini surfactant molecules better facilitating the self assembly into aggregates and more efficiently decreasing the surface tension than the corresponding monomeric surfactants. Moreover, other physicochemical parameters (Γ CAC , A CAC , △G θ mic , and △G θ ads ) related to surface activity were calculated according to previous studies [32][33][34][35].…”

“…On the one hand, the average sizes of the aggregates increased as the hydrophobic spacer increased (e.g., from 209.09 nm for S 2 (EO) 4.14 (m = 2) and 216.95 nm for S 4 (EO) 4.14 (m = 4) to 237.04 nm for S 6 (EO) 4.14 (m = 6); from 205.50 nm for S 2 (EO) 8.68 (m = 2) and 215.56 nm for S 4 (EO) 8.68 (m = 4) to 234.91 nm for S 6 (EO) 8.68 (m = 6); and from 195.34 nm for S 2 (EO) 13.23 (m = 2) and 214.68 nm for S 4 (EO) 13.23 (m = 4) to 229.89 nm for S 6 (EO) 13.23 (m = 6)) likely due to the progressive penetration of the spacer into the hydrophobic core of the micelle, which allowed the surfactant molecules to pack tighter and form larger aggregates, which was reflected in the increase in diameter. On the other hand, the average sizes of the aggregates decreased with increasing length of the hydrophilic ethoxy chains (e.g., from 209.09 nm for S 2 (EO) 4.14 and 205.5 nm for S 2 (EO) 8.68 to 195.34 nm for S 2 (EO) 13.23 ; from 216.95 nm for S 4 (EO) 4.14 and 215.56 nm for S 4 (EO) 8.68 to 214.68 nm for S 4 (EO) 13.23 ; and from 237.04 nm for S 6 (EO) 4.14 and 234.91 nm for S 6 (EO) 8.68 nm to 229.89 nm for S 6 (EO) 13.23 ) potentially due to the strong interaction between the hydrophilic ethoxy chains and water molecules lowering the hydrophobicity of the surfactant molecules and resulting in less favorable micellization, which was reflected in the decrease in diameter [36,37]. Furthermore, some large aggregates (sizes of approximately 300-350 nm) coexisted with small spherical micelles.…”

“…The obtained parameters for the as-prepared gemini surfactants are summarized in Table 1. The surface tension at the same concentration increased as S 6 (EO) 4.14 < S 4 (EO) 4.14 < S 2 (EO) 4.14 < S 6 (EO) 8.68 < S 4 (EO) 8.68 < S 2 (EO) 8.68 < S 6 (EO) 13.23 < S 4 (EO) 13.23 < S 2 (EO) 13.23 , and the same trend was obtained for the CAC: S 6 (EO) 4.14 (3.84×10 mol/L) and γ CAC (21.00 mN/m) of S 6 (EO) 4.14 (m = 6). The CAC and γ CAC of S m (EO) n slightly decreased with an increasing number m (m = 2, 4 or 6, respectively) of -CH 2 -groups in the spacer because of the increased molecular hydrophobicity, easily reducing the surface tension and forming aggregates.…”

“…This stage was undetectable for S 6 (EO) 4.14 , S 4 (EO) 4.14 , S 2 (EO) 4.14 , S 6 (EO) 13.23 , S 4 (EO) 13.23, and S 2 (EO) 13.23 because their second stage was relatively slow. In addition, the adsorption time of the spreaders increased in the following order: S 6 (EO) 8.68 < S 4 (EO) 8.68 < Silwet L-77 < S 2 (EO) 8.68 < S 6 (EO) 4.14 < S 4 (EO) 4.14 < S 2 (EO) 4.14 < S 6 (EO) 13.23 < S 4 (EO) 13.23 < S 2 (EO) 13.23 . A shorter adsorption time corresponds to a faster migration rate of the superspreaders.…”

“…The surface tension of aqueous superspreader solutions at the critical aggregation concentration (CAC) is relatively low (20)(21)(22)(23)(24)(25) mN/m) [7,8], but not lower than that of fluorosurfactants (18-28 mN/m) [9]. However, trisiloxane-based surfactants promote the rapid spreading of water droplets over hydrophobic surfaces and even wet them completely.…”