TY - JOUR
T1 - Spreading of aqueous solutions of trisiloxanes and conventional surfactants over PTFE AF coated silicone wafers
AU - Ivanova, Natalia
AU - Starov, Victor
AU - Johnson, Daniel
AU - Hilal, Nidal
AU - Rubio, Ramon
PY - 2009/3/17
Y1 - 2009/3/17
N2 - Kinetics of spreading of aqueous trisiloxane surfactant Tn (with n = 4, 6, and 8 ethoxy groups) solutions and conventional aqueous surfactant solutions (Tween 20, C12E4, SDS) over silicon wafers coated with PTFE AF is experimentally investigated. It has been found that trisiloxane solutions spread on highly hydrophobic PTFE AF coated silicone wafers; however, they do not show superspreading behavior on these highly hydrophobic substrates. Solutions of conventional nonionic surfactants investigated show kinetics of spreading similar to trisiloxanes. Three regimes of spreading have been identified (i) complete non-wetting during the spreading process at low concentrations, (ii) a transition from initial nonwetting to partial wetting at the end of the spreading process at intermediate concentrations, and (iii) partial wetting both at the beginning and the end of the spreading process at higher concentrations. Transition from, the first regime (i) to the second regime (ii) takes place at the critical aggregation concentration (CAC) or critical micelle concentration (CMC), transition from regime (ii) to regime (iii) happens at the critical wetting concentration (CWC). In the case of regime (i) the spreading of nonionic surfactants solutions investigated on. PTFE AF coated silicone wafers is slow and follows a theoretically predicted law (Starov; et al. J. Colloid Interface Sci. 2000, 227 (1), 185). In the case of regimes (ii) and (iii), the spreading of the nonionic surfactant solutions investigated proceeds in two stages: the fast short first stage, which is followed by a much slower second stage. It is shown that the slow stage develops according to a previously described theoretical model. According to this theory the surfactant molecules adsorb in front of the moving three-phase contact line (autophilic phenomenon), which results in a partial hydrophilisation of an initially hydrophobic substrate and a spreading as a consequence. We assume that the first stage of the spreading is related to the disintegration of surfactant aggregates in the vicinity of the moving three-phase contact line.
AB - Kinetics of spreading of aqueous trisiloxane surfactant Tn (with n = 4, 6, and 8 ethoxy groups) solutions and conventional aqueous surfactant solutions (Tween 20, C12E4, SDS) over silicon wafers coated with PTFE AF is experimentally investigated. It has been found that trisiloxane solutions spread on highly hydrophobic PTFE AF coated silicone wafers; however, they do not show superspreading behavior on these highly hydrophobic substrates. Solutions of conventional nonionic surfactants investigated show kinetics of spreading similar to trisiloxanes. Three regimes of spreading have been identified (i) complete non-wetting during the spreading process at low concentrations, (ii) a transition from initial nonwetting to partial wetting at the end of the spreading process at intermediate concentrations, and (iii) partial wetting both at the beginning and the end of the spreading process at higher concentrations. Transition from, the first regime (i) to the second regime (ii) takes place at the critical aggregation concentration (CAC) or critical micelle concentration (CMC), transition from regime (ii) to regime (iii) happens at the critical wetting concentration (CWC). In the case of regime (i) the spreading of nonionic surfactants solutions investigated on. PTFE AF coated silicone wafers is slow and follows a theoretically predicted law (Starov; et al. J. Colloid Interface Sci. 2000, 227 (1), 185). In the case of regimes (ii) and (iii), the spreading of the nonionic surfactant solutions investigated proceeds in two stages: the fast short first stage, which is followed by a much slower second stage. It is shown that the slow stage develops according to a previously described theoretical model. According to this theory the surfactant molecules adsorb in front of the moving three-phase contact line (autophilic phenomenon), which results in a partial hydrophilisation of an initially hydrophobic substrate and a spreading as a consequence. We assume that the first stage of the spreading is related to the disintegration of surfactant aggregates in the vicinity of the moving three-phase contact line.
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U2 - 10.1021/la803679y
DO - 10.1021/la803679y
M3 - Article
C2 - 19236038
AN - SCOPUS:65249116559
SN - 0743-7463
VL - 25
SP - 3564
EP - 3570
JO - Langmuir
JF - Langmuir
IS - 6
ER -