Adsorption kinetics of heptadecafluoro-1-nonanol: Phase transition and mixed control

作者：Casandra Alvin; Noskov Boris A; Hu Min Yu; Lin Shi Yow^*

来源：Journal of Colloid and Interface Science, 2018, 527: 49-56.

DOI：10.1016/j.jcis.2018.04.096

• Phase transition
• Fluorinated surfactant
• Surface tension
• Adsorption kinetics
• Mixed-control

Hypothesis: The adsorption kinetics of heptadecafluoro-1-nonanol (C9H2F17OH) onto a clean air-water interface at low surfactant concentrations (equilibrium surface tension, gamma(C) > 65 mN/m) has been reported, and the controlling mechanism was found to be mixed diffusive-kinetic controlled (Kuo et al., JCIS 402 (2013) 131). However, it remains to be determined what the adsorption kinetics are at higher concentrations. Hence, the dynamic surface tension, gamma(t) of C9H2F17OH was measured and compared with the theoretical gamma(t) curves predicted from phase transition model.
Experiments: A video-enhanced pendant bubble tensiometer was used to measure the y(t) data of aqueous C9H2F17OH solutions at higher concentrations (C > 7.7 x 10(-9) mol/cm(3)). A new generalized FrumkinLangmuir phase transition model was built up to simulate the gamma(C) and gamma(t) data.
Findings: At higher surfactant concentrations, a constant-y region at 64.8 mN/m was observed for one hundred to a few thousand seconds during the gamma(t) relaxation. This constant-gamma region implies the 'existence of a phase transition of the adsorbed surfactant monolayer at air-water interface.
The gamma(t) data of C9H2F17OH can be simulated perfectly using this mixed-controlled phase transition model with the adsorption rate constants beta(1) = 1.0 +/- 0.5 and beta(2) = 13 +/- 4 (10(5) cm(3)/mol-s). It is therefore concluded that the adsorption process of C9H2F17OH onto a clean air-water interface is of mixed-control.

• 出版日期2018-10-1