Organosilicone surfactants

Penner, D. Burow, R. Roggenbuck, F. C. Use of Organosilicone Surfactants as Agricultural Adjuvants. In Silicone Surfactants Hill, R. M., Ed. Surfactant Science Series Dekker New York, 1999 Vol. 86, Chapter 9, pp 241-258. 

The synthesis of organosilicones and organosilicone surfactants has been well described elsewhere [36-39] and hence only a brief review is given here. Industrially the manufacture of silicones is performed stepwise via the alkylchlorosilanes, produced through the reaction of elemental silicon with methyl chloride (the Muller—Rochow Process) [40,41]. Inclusion of HC1 and/or H2(g) into the reaction mixture, as in Eq. (1.2), yields CH3HSiCl2, the precursor to the organofunctional silanes, and therefore the silicone surfactants ... 

SPECTROMETRY—V. NON-IONIC SURFACTANTS FLOW INJECTION ANALYSIS—MASS SPECTROMETRY AND LIQUID CHROMATOGRAPHY—MASS SPECTROMETRY OF ORGANOSILICONE SURFACTANTS... 

Organosilicone surfactants can be classified according to the position of the lyophilic moiety with respect to the Si-O-Si polymer. The abbreviations M, D, T and Q, referring to the number of oxygen atoms bonded to the silicon, are used to define the silicone portion as shown in Table 2.8.2. Insertion of the lyophilic moiety (A) into the silicone polymer itself leads to monofunctional, i.e. M(D A)M, and polyfunctional linear, i.e. MID A D M, type surfactants. Polyfunctional linear versions are also described as rake, comb- or graft-copolymers. Substitution at the ends of the silicone polymer yields surfactants... 

The use of organosilicone surfactants in agrochemical formulations has become increasingly widespread [13]. These products are known to enhance spray coverage and in many cases increase the foliar uptake of... 

API-MS techniques (ESI and APCI) have been shown to be informative methods for the qualitative and quantitative analysis of organosilicone surfactants. The use of HPLC-API-MS has enabled improvements in... 

L.S. Bonnington, Analysis of Organosilicone Surfactants and their Degradation Products, PhD Thesis, University of Waikato, Hamilton, New Zealand, 2001. 

The results indicate that persistence of organosilicone surfactants in the parent molecule form will be limited on typical soil media and in aqueous environments. Reduced recovery was considered to be a result of abiotic degradation and/or strong sorption processes. Losses were most significant on solid media exhibiting extreme pH values and were also enhanced in the presence of clay substrates. Studies on clays indicated that pH, potential for intercalation and surface charges are important factors in the removal process. 

Sun JS, Foy CL (1996) Structurally related organosilicone surfactants, their physicochemical properties and effects on uptake and efficacy of primisulfuron in velvetleaf (Abutilon theophrasti Medicus). FRI Bulletin 193 225-230 (Proceedings of the fourth international symposium on adjuvants for agrochemicals, 1995)... 

The bacteria Pseudomonas syringae pv. tagetis, which is pathogenic to Jerusalem artichoke (Shane and Baumer, 1984), can apparently be used to repress weed populations. Spray applications of the organism (5 x 10s cells-mL1) in aqueous buffer with a non-ionic organosilicone surfactant (e.g., Silwet L-77 or Silwet 408), the latter being essential for infection, are said to produce severe disease symptoms, although no data were shown (Johnson et al., 1996). 

Although not siloxane based, organosilicon surfactants have also been made from per-methylated carbosilanes containing an Si-C-Si structure. The simplest version of this is the trimethyl silylated alkyl polyether discussed by Klein [22] and Wagner [11, 23]. These surfactants are more hydrolytically stable wetting agents than the trisiloxanes. 

Summary The hydrolysis of current organosilicone surfactants occurs at the Si-O-Si bonds. 

Baylis AD and Hart CA Varying responses among weed species to glyphosate-trimesium in the presence of an organosilicone surfactant, Proceedings, 1980 British Crop Protection Conference - Weeds, pp. 1331-1336 (1993). 

Gaskin RE and Stevens, PJG Antagonism of the foliar uptake of glyphosate into grasses by organosilicones surfactants. Parts 1 and 2 Effect of plant species, formulation, concentrations and timing of application. Pesticide Science, 38 185-200 (1993). 

Organosilicone surfactants can exhibit improved surface tension lowering (for improved leaf wetting) and low dynamic surface tension (for spray-drop retention on leaves), and are used in some commercial spray-application products [88]. 

R. J. Field, N. G. Bishop, Promotion of Stomatal Infiltration of Glyphosate by the Organosilicone Surfactant Silwet L-77 Reduces the Critical Rainfall Period , Proceedings of the European Weed Research Society,l98S, pp. 205-206. 

Adjuvants are most often nsed with herbicides, but they are also used with selected insecticides and fungicides. The adjuvants conunonly in use include surfactants, oils, solvents, polymers, foams, salts, and photo protectants, as weU as combinations of these components. Adjuvants for herbicides delivered from water dilutions are most commonly nonionic surfactants and crop oil concentrates. Nonionic surfactants are added for wetting of the leaf surfaces, and the crop oil concentrates are added as penetration enhancers. Organosilicone surfactants have been shown to enhance the availability of several pesticides. The silicone surfactants reduce the surface tension below 20 dyne/cm and are often referred to as super wetting surfactants. 

The existence of relatively polar routes across the cuticle remains controversial, though there may be localized regions of greater permeability. If this is the case, these may facilitate preferential penetration of properly formulated polar herbicides, especially under high-humidity conditions. The use of certain organosilicone surfactants appears to result in the reduction of surface tension to a level which permits mass flow through the stomatal aperture. 

Chem. Descrip. Organosilicone surfactant/alcohol ethoxylate surfactant blend Silfar S194 [Wacker-Chemie AG]... 

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