Trisiloxane superspreader/superspreading

What Super Spreads — An Analysis of the Spreading Performance of the Single Components of the Trisiloxane Superspreader Type M2D -(CH2)3-(0CH2CH2) -0CH3... 

One major application of trisiloxane superspreading surfactants is therefore as adjuvants in a agriculture applications [87], The superior coverage increases the contact area of the active ingredient with the plant additionally, the low surface tension promotes stomatal infiltration and an accelerated uptake and translocation of the active ingredient into the plant. Subsequently, this leads to improved rainfastness. 

Churaev NV, Esipova NE, Hill RM, Sobolev VD, Starov VM, Zorin ZM (2001) The superspreading effect of trisiloxane surfactant solutions. Langmuir 17 1338-1348... 

Kumar N, Couzis A, Maldarelli C (2003) Measurement of kinetic rate constants for the adsorption of superspreading trisiloxanes to an air/aqueous interface and the rele-... 

Raney K, Benton W, Miller CA (1987) Optimum detergency conditions with nonionic siufactants II. Effect of hydrophobic additives. J Colloid Interface Sci 119 539-549 Rosen MJ, Wu Y (2001) Superspreading of trisiloxane surfactant mixtures on hydrophobic siufaces 1. Interfacial adsorption of aqueous trisiloxane surfactant -M-alkyl pyrrolidinone mixtures on polyethylene. Langmuir 17 7296-7305 Stevens PJG, Kimberely MO, Mimphy DS, Policello GA (1993) Adhesion of spray droplets to foliage - the role of dynamic surface tension and advantages of organosil-icone surfactants. Pesticide Sci 38 237-245... 

Stoebe T, Lin Z, Hill RM, Ward MD, Davis HT (1997) Superspreading of aqueous films containing trisiloxane surfactant on mineral oil. Langmuir 13 7282-7286 Stoebe T, Hill RM, Ward MD, Scriven LE, Davis HT (1996) Surfactant-enhanced spreading. Langmuir 12 337-344... 

Wu Y, Rosen MJ (2002) Superspreading of trisiloxane surfactant mixtures on hydrophobic surfaces 2. Interaction and spreading of aqueous trisiloxane surfactant -n-alkyl pyrrolidinone mixtures in contact with polyethylene. Langmuir 18 2205-2215... 

By using a recently developed magnesium hydride technology, the trisiloxane lyophobic part in superspreading surfactants can be substituted by a trimethylsilane moiety. This synthetic route leads to both nonionic and ionic silane surfactants, which are hydrolytically stable even under extreme pH. Aqueous solutions of these new surfactants exhibit surface tension and wetting properties comparable to the traditional organomodified trisiloxane surfactants. The combination of hydrolytic stability and biodegradability offers chance for the widespread application of these silane based surfactants. 

For a series of lV-alkyl-2-pyrrolidinones that produce enhanced superspreading of the POE trisiloxane mentioned above on polyethylene film, it has been shown (Rosen, 2001) that the addition of the alkylpyrrolidinone to the trisiloxane surfactant produces little or no increase in the total surfactant at the hydrophobic solid-air or aqueous solution-air interfaces, but a considerable increase in the total surfactant adsorption at the hydrophobic solid-aqueous solution interface. This enhanced adsorption of surfactant at the aqueous solution-solid interface relative to that at the aqueous solution-air interface produces a decrease in the surfactant concentration at the air-solution interface in the thin precursor film at the wetting front (Figure 6-8). This results in a surface tension gradient in the precursor film promoting movement of the aqueous phase to the wetting front. 

The order of increased surfactant adsorption on the solid produced by the different alkyl pyrrolidinones parallels the order of their enhancement of superspreading. In addition, it was shown (Wu, 2002) (1) that the change in the spreading coefficient (equation 6.1) parallels enhancement of superspreading and (2) that the order of increased attractive molecular interaction between the different alkylpyr-rolidinones and the trisiloxane surfactant at the hydrophobic solid-aqueous solution interface, as measured by the interaction parameter Psl° (Chapter 11) n-butyl < n-cyclohexyl < -octyl < n-hexyl < 2-ethylhexyl, is exactly the same order as that of their enhancement of the superspreading. 

Trisiloxane surfactants have been used as adjuvants in agriculture. They increase the foliar uptake of pesticides, due to reduction of surface tension and superspreading. A method for improving the performance of agricultural compositions under conditions of low humidity has been developed, by using silicone surfactants that reduce the surface tension to less than 30 mN/m in 0.10% (w/w) aqueous solution, without concomitant spreading of the spray solution [60]. 

Keywords Trisiloxane Surfactants / Superspreading / Phase Behavior... 

Aqueous solutions of certain trisiloxane surfactants wet rapidly low-energy surfaces (water contact angle > 90°) [1]. The spreading rate of a superspreader solution significantly exceeds that expected for a purely liquid diffusion controlled process [2, 3]. 

Keywords Superspreading / Trisiloxane / Surface Tension / Silicone / Vesicles... 

The wetting exhibited by some trisiloxane surfactants is so extensive and rapid that it has been referred to as superspreading [3]. Typically, a small drop (50 pL) of a diluted aqueous solution (0.1 % w/w) of such a trisiloxane spreads out on a hydrophobic surface such as a polypropylene sheet into a thin, wetting film approx. 80 mm in diameter within tens of seconds. This is about 20 times the area wetted by a 1 % w/w solution of a conventional organic surfactant such as a nonylphenol ethoxylate. 

These theories, however, do not explain why only some trisiloxane surfactants exhibit superspreading behavior, and why minor variations in the hydrophilic head group can lead to dramatically reduced spreading. This effect is demonstrated in Table 1 for the four specific trisiloxane surfactants used in our studies. 

The following experiments describe some phenomena which can be observed with superspreading trisiloxane surfactants. They can all be explained with the help of these theoretical considerations and therefore further support these statements. 

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