Silicone polyethers

Furthermore, silicone aliphatic polyethers, in particular poly(dimethylsiloxane)-poly(ethyleneglycol),an amphiphilic 

It is worth mentioning here that PEG is a biomedical polymer with excellent biocompatibility and resistance to platelet and protein adsorption due to its mobility in aqueous environments [30]. Indeed, PEG allows biomaterials to retain their excellent water swelling properties, whereas PDMS modifies its surface to inhibit protein adsorption [17]. Hence, PDMS-PEG copolymers are considered to be ideal candidates as biomaterials 

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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... 

Legrow, G. E. Petroff, L. J. Silicone Polyether Copolymers Synthetic Methods and Chemical Compositions. In Silicone Surfactants-, Hill, R. M., Ed. Surfactant Science Series Dekker New York Vol. 86, Chapter 2, pp 49-64. 

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,... 

NMR) [24], and Fourier transform-infrared (FT-IR) spectroscopy [25] are commonly applied methods. Analysis using mass spectrometric (MS) techniques has been achieved with gas chromatography-mass spectrometry (GC-MS), with chemical ionisation (Cl) often more informative than conventional electron impact (El) ionisation [26]. For the qualitative and quantitative characterisation of silicone polyether copolymers in particular, SEC, NMR, and FT-IR have also been demonstrated as useful and informative methods [22] and the application of high-temperature GC and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) is also described [5]. 

Initial degradation of silicone surfactants is thought to occur predominantly as hydrolyis of the silicone Si—O moiety, and this is known to be enhanced at acidic or alkaline pH values [3,11,12]. At neutral pH the surfactants are generally considered stable, but residual acidity or basicity of glassware is also known to catalyse their hydrolytic degradation [7]. Silicone polyether surfactants possessing the Si—O—C... 

A significant amount of information regarding the uses of silicone surfactants is still found primarily in the patent art, but the major applications have recently been reviewed in journals. Silicone (or siloxane) surfactants are also called silicone polyethers (SPEs), polyalkylene oxide silicone copolymers, silicone poly(oxyalkylene) copolymers and silicone glycols. The International Cosmetic Ingredient Nomenclature and the Cosmetic, Toiletry and Fragrance Association (CTFA) adopted name is dimethicone copolyol. 

Legrow, G.E. and Petroff, L. J. (1999) Silicone polyether copolymers synthetic methods and chemical compositions. In R.M. Hill, (edr.), Surfactant Science Series. Dekker, New York. pp. 49-64. 

Gentle, T.E. and Snow, S.A. (1995) Adsorption of small silicone polyether surfactants at the air/water interface. Langmuir, 11(8), 2905-10. 

Silicone surfactants. For the purpose of this work, silicone surfactants will be defined as silicone polyether copolymers with hydrolytically stable silicon-carbon bonds. The manufacturing of these products involves a three-step process ... 

Silicone polyethers are used as emulsifiers, resin plasticizers, and light conditioning agents. 

Keywords silicone, polyether, water stability, pH stability... 

It is known that silicone polyether copolymers can have limited stability in aqueous media. The stability will depend on several factors, which include pH, concentration, stmcture of the copolymer, and the molecular weight of the copolymer. In this work the stability of a wide range of copolymers was investigated in aqueous media at various pH values and concentrations. The goal was to provide formulators and users with a tool to predict the long-term stability of silicone polyether surfactants in their own applications and formulations. 

To determine the stability of silicone polyether copolymers, solutions were prepared by dispersing the copolymers in standard buffer solutions ranging in pH from 2 to 12 and concentrations ranging from 0.5 to 2.0 weight percent. High-performance liquid chromatography (HPLC) was used to monitor the stability of the polymers over time. Reverse-phase HPLC is an ideal method for... 

Fig. 2. Percent of unhydrolyzed material curve for a silicone polyether copolymer, 95% Unhydrolyzed — The amount of time over which there is no hydrolysis. 80% Unhydiolyzed — The amount of time to establish a hydrolysis trend.

To fully analyze a silicone polyether copolymer, solutions ranging in pH from 2 to 12 were... 

There is a wide range of commercially available silicone polyether copolymers. They fall into three classes conventional, hydrolyzable and trisiloxane. These classes are described below. 

Conventional silicone polyether copolymers have excellent stability as the polyether groups are attached to the siloxane backbone through a series of hydrolytically stable Si-C bonds. Analysis of materials with some hydrolysis revealed that these levels of hydrolysis had no effect on pafomiance properties. 

Hydrolyzable silicone polyether copolymers are made by condensation chemistry and contain Si-O-C bonds between the silicone chain and polyether chains. This linkage offers limited resistance to hydrolysis under neutral and slightly alkaline conditions but breaks down quickly in acidic media. 

Trisiloxanes represent a unique subset within conventional silicone polyether copolymers. Their well-defined compact siloxane backbone affords distinctive application benefits (e.g., spreading and wetting). However, they tend to be more prone to hydrolysis. 

A number of silicone polyether copolymers were studied. These are detailed in Table 1 and are listed in order of increasing stability. To provide a tool for prediction of stability, 80% unhydrolyzed material was chosen as the stability limit A summary of these times is shown in Table 2 and Fig. 4. 

Table 1. Molecular weight, solubility, and architecture of silicone polyether copolymers studied.

Fig. 4. Time to reach 80% unhydiolyzed material for all silicone polyether copolymers in acidic and basic media at 1% concentration.

The rate of hydrolysis of conventional silicone polyether copolymers decreases as ... 

The recommended pH range for maintaining long-term stability of conventional silicone polyether copolymers is 5.5 to 8.5. 

Hydrolyzable silicone polyether copolymers have limited stability in aqueous media due to the presence of Si-O-C linkages. The recommended pH range for maintaining optimum stability of hydrolyzable silicone polyether copolymers is 6.0 to 8.0. 

Table 3. Optimum pH ranges for stability of silicone polyether copolymer types.

Silicone Polyether Copolymer Type pH Ranae for Optimum Stability... 

The largest volume of grease in use is made from petroleum products produced from naphthenic, paraffinic, blended, hydrocracked, hydrogenated, and solvent-refined stocks. In addition to petroleum oils, other lubricating fluids, such as esters, diesters, silicones, polyethers, and synthetic hydrocarbons, are also used. Of the synthetic fluids used in grease manufacture, the most common type is poly(alpha)olefin (PAO). 

U.S. 5393452 (1995) Raleigh et al. (General Electric) High-molecular-weight, high-viscosity silicone-polyether copolymer Improved antistatic properties conditioning shampoo... 

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