Silicon surfactant

Place Arcol Polyol F-3022 (100 g, 0.1 eq., 56 OH, mixed PO/EO triol from Bayer) into a suitable container. To this add distilled water (3.3 g, 0.4125 eq.), Niax Silicone L-620 (0.5 g, a silicone surfactant from OSi Specialties), and Niax C-183 (0.12 g, an amine catalyst from OSi Specialties). Thoroughly blend this mixture without incorporating air bubbles. Then add Dabco T-9 (0.25 g, stannous octoate from Air Products) and mix again. The T-9 must be added last because it is quite water sensitive, so its exposure to the water-containing polyol blend should be kept to a minimum. To this polyol blend, quickly add Mondur TD-80 (42.6 g, 0.4868 eq., a mixture of 80% 2,4-TDI and 20% 2,6-TDI isomers from Bayer) and immediately stir at 3000 rpm for 5 s. Quickly pour the reaction mixture into a suitable container such as a 1-qt paper or plastic cup and allow the foam to free-rise. The stir blade may be wiped or brushed clean. 

Summary New lyophilic cationic silicone surfactants have been synthesized by direct quatemization of halogenated siloxanyl precursors or by transformation of these precursors into tertiary amines with a subsequent quatemization step. After transformation of the precursors into secondary amines, reaction with maleic anhydride and neutralization, new anionic products were obtained. 

Only few attempts have been made recently to study the influence of the spacer between the silicone backbone and the hydrophilic head group on the interfacial properties of silicone surfactants [1,2,3]. Further the strong dispersion interactions caused by cyclic hydrocarbon sUuctures, especially the dicyclopentadienyl unit [4] have never been recognized to be an effective tool to counterbalance the known reverse effect of the methyl groups of the siloxanyl unit in coventional silicone surfactants. 

The physicochemical data underline the striking influence of the dicyclopentadienyl unit on the properties of these silicone surfactants. In comparison to conventional products [7], the critical micelle formation concentration was lowered for up to two orders of magnitude whereas the minimum surface tension reached rose only slightly. The data collected indicate that the type of surfactant has been changed from the initial "effective" to a more "efficient" one. 

The unique surface characteristics of polysiloxanes mean that they are extensively used as surfactants. Silicone surfactants have been thoroughly studied and described in numerous articles. For an extensive, in-depth discussion of this subject, a recent chapter by Hill,476 and his introductory chapter in the monograph he later edited,477 are excellent references. In the latter monograph, many aspects of silicone surfactants are described in 12 chapters. In the introduction, Hill discusses the chemistry of silicone surfactants, surface activity, aggregation behavior of silicone surfactants in various media, and their key applications in polyurethane foam manufacture, in textile and fiber industry, in personal care, and in paint and coating industries. All this information (with 200 cited references) provides a broad background for the discussion of more specific issues covered in other chapters. Thus, surfactants based on silicone polyether co-polymers are surveyed.478 Novel siloxane surfactant structures,479 surface activity and aggregation phenomena,480 silicone surfactants application in the formation of polyurethane foam,481 foam control and... 

Hill, R. M. Siloxane Surfactants. In Silicone Surfactants-, Hill, R. M., Ed. Surfactant Science Series Dekker New York, 1999 Vol. 86, Chapter 1, pp 1-47. 

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 ... 

Industrially, silicone surfactants are used in a variety of processes including foam, textile, concrete and thermoplastic production, and applications include use as foam stabilisers, defoamers, emulsifiers, dispersants, wetters, adhesives, lubricants and release agents [1]. The ability of silicone surfactants to also function in organic media creates a unique niche for their use, such as in polyurethane foam manufacture and as additives to paints and oil-based formulations, whilst the ability to lower surface tension in aqueous solutions provides useful superwetting properties. The low biological risk associated with these compounds has also led to their use in cosmetics and personal care products [2]. 

A broad range of silicone surfactants are commercially available, representing all of the structural classes—anionic, non-ionic, cationic, and amphoteric. The silicone moiety is lyophobic, i.e. lacking an affinity for a medium, and surfactant properties are achieved by substitution of lyophilic groups to this backbone. The most common functionalities used are polyethylene glycols however, a broad range exist, as shown in Table 2.8.1 [2,3]. 

Examples of different types and substituents of silicone surfactants [2,3]... 

The polyether-modified structures are the most important silicone surfactants currently in use, examples of which are shown in Fig. 2.8.1. These are known by many names, including silicone polyethers, polyethermethylsiloxanes (PEMSs), dimethicone copolyols,... 

Atmospheric pressure ionisation-mass spectrometric characterisation of silicone surfactants... 

Non-ionic silicone surfactants such as M2D-C3-0-(E0)n-CH3 (1), are thus detectable by API-MS methods as adducts with NH4, Na+ and K+ cations as shown in Fig. 2.8.3 [29]. Minor [M + H]+ adducts for M2D-C3-0-(E0)n-H (2) have been observed, although, in the case of M2D-C3-0-(E0)n-CH3 these were not detected even with the addition of acidic media. Only singly charged species of M2D-C3-0-(EO) —Me (n 3-16) were observed for all cone voltages [29], as is consistent with that expected for the polyethylene glycol (PEG) oligomeric distribution [37,38],... 

Flow injection analysis (FIA) ESI-MS and APCI-MS spectra for an EO/PO polyether modified silicone surfactant (PEMS) used as a personal care product have been obtained in positive and negative ionisation modes with the positive ionisation mode yielding the best results [41]. The spectra obtained in both modes were highly complicated, and thus no assignment was given. Significant differences in the ionisation results were obtained from the two interfaces, with those ions observed in the ESI-MS spectrum appearing in the lower... 

An industrial blend of ethylene oxide (EO) PEMS marketed as a personal care product was examined by positive ion FIA-APCI-MS and LC-APCI-MS-MS (Fig. 2.8.8) [41]. The FIA-APCI-MS spectrum without LC separation (Fig. 2.8.8(a)) is dominated by ions corresponding to unreacted PEG (m/z 520, 564, 608, 652,...), whilst the ions corresponding to the PEMS (m/z 516, 560, 604, 648,...) could only be clearly observed following LC separation (Fig. 2.8.8(b)). Comparison of the TIC chromatograms of PEMS and PEG (Fig. 2.8.8(c) and (h)) demonstrates the dominance of the PEG by-products in the commercial formulation. It is unclear whether the observed relative intensities are representative of the actual amounts or of the different ionisation efficiencies, due to the confidential nature of the product composition. However, the spectra indicate a trisiloxane surfactant structure of that shown in Fig. 2.8.2 (R = Ac) and FIA-MS analysis of another commercial formulation of this product showed good spectra dominated by the silicone surfactants [48], indicating that the PEG by-product composition can vary significantly in commercially available PEMS formulations. 

API—MS methods have also been applied to qualitative and quantitative determinations of the degradation of silicone surfactants [29]. Comparison of the APCI—MS spectrum of M2D—C3—O—(EO) —Me with that following 24 h equilibration in the presence of halloysite clay is shown in Fig. 2.8.9. 

I. Schlachter and G. Feldmann-Krane, In K. Holmberg (Ed.), Silicone Surfactants, Novel Surfactants, Surfactant Science Series, Vol. 74, Marcel Dekker, New York, USA, 1998, p. 201. 

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