3,3,3-trifluoropropyl group

Polysiloxanes containing a-cyano and a- or ]]-fluorine substituents are. thermally labile at comparatively low temperatures and are not used in gas chromatography. Polysiloxane phases containing 3,3,3-trifluoropropyl groups are thermally Stable up to about 250-275 C and possess rather unique selectivity, particularly for electron-donor solutes, such as ketones and nitro groups. The electronegative trifluoropropyl... 

The poly(siloxane) polymers are usually prepared by the acid or base hydrolysis of appropriately substituted dichlorosilanes or dialkoxysilanes, or by the catalytic polymerization of small ring cyclic siloxanes [71-75]. The silanol-terminated polymers are suitable for use after fractionation or are thermally treated to increase molecular weight and in some cases endcapped by trimethylsilyl, alkoxy or acetyl groups [76,77]. Poly(siloxanes) synthesized in this way are limited to polymers that contain substituent groups that are able to survive the relatively harsh hydrolysis conditions, such as alkyl, phenyl, 3,3,3-trifluoropropyl groups. Hydrosilylation provides an alternative route to the synthesis of poly(siloxanes) with labile or complicated substituents (e.g. cyclodextrin, oligoethylene oxide, liquid crystal, amino acid ester, and alcohol) [78-81]. In this case... 

Aliphatic hydrocarbons such as heptane cause swelling in crosslinked polydi-methylsiloxane, as do aromatic and chlorinated hydrocarbons. Oil resistance of polydimethylsiloxane is considerably improved by substituting the methyl group by 3,3,3-trifluoropropyl groups [744]. In each dimethylsiloxane unit only one methyl group is substituted by a 3,3,3-trifluoropropyl group so that methyl-3,3,3-... 

Trifluoromethyl peroxide, 78 446 Trifluoropropyl groups, in moisture-curing silicones, 22 32... 

The presence of trIfluoropropyl groups on the polymer backbone leads to an Increase In weight loss ( 7, J8). 

Modification of the polymer backbone by the incorporation of trifluoropropyl groups leads to substantial decreases in swelling. In vulcanized systems reinforced with hydrophilic silica (30 phr) the swelling decreased with increasing CH2CH2CF3 content as shown in Table III. 

The /V-methylacetamide is a readily removable, neutral species which causes no subsequent polymer attack. The fluorine atom is easily detectable by XPS and is not present in most silicone surfaces. The trifluoropropyl group is the smallest fluorine-containing nonreactive group on Si that is chemically stable and provides a stoichiometric enhancement factor of three. 

Replacement of a propyl group by a 1,1,1-trifluoropropyl group increases the Tg (polymers la and le). 

The existence of TFPS on the sample surface generates hydrophobicity due to the presence of CF3 from the trifluoropropyl groups (-Si-(CH2)3CF3). Indeed, the fluorine content is an indicator of surface hydrophobicity. The fluorine content of the surface can be quantified using EDS as shown in Fig. 1 Table 1 gives the atomic fluorine percentage. When the ratio of TFPS to TEOS increases, the fluorine content increases and water droplet contact angle on the surface increases concomitantly. 

Y. Cui, W. Jiang, D. Li, C. Niu, S. Feng, Preparation and properties of fluorosilicone and fluorosilicone elastomer with various contents of trifluoropropyl groups, e-Polymers 11 (1) (2011)302-314. 

Trifluoropropyl groups are added to improve solvent resistance. Low molecular weight polydimethylsiloxanes with 50 to 2,000 repeat units are used to make systems which cure at room temperature. 

The effect of replacing one methyl group with a trifluoropropyl group in PDMS is quite considerable. Compared to PDMS, PMTFPS exhibits... 

Some of these changes, such as increased glass transition temperature and reduced gas diffusion are the expected consequence of the bulkier trifluoropropyl group detracting from the marked flexibility of the siloxane backbone. In what follows, the emphasis is on the surface properties of PMTFPS, as these are not so predictable. 

It is a straightforward concept that the relative bulkiness of the trifluoropropyl group can impede siloxane backbone flexibility and influence the physical properties of the PMTFPS polymer when we substitute one of the methyl groups in the Me2SiO repeat... 

Concerning the refractive index, sihcones may have an extremely wide range that goes from 1.38 to 1.60. Polydimethylsiloxane has a refractive index of 1.40 at 25 °C (598 nm). Substitution of trifluoropropyl groups for the methyl groups reduces the refractive index to 1.38, while the... 

The surface tension of fluorosiloxanes in the liquid state is measured directly and usually the values obtained are not affected by the measurement technique. The equilibrium surface tension in water is related to the liquid surface tension value. Siloxanes with trifluoropropyl groups are less effective in lowering the surface tension of water than the nonfluorinated poly(dimethyl) siloxanes. The surface tension of poly(3,3,3, trifluoropropylmethylsiloxane) is higher than that of the lower-cost dimethicones [poly(dimethylsiloxane)] [134,135]. Because of the high affinity of fluorine to silicon [136], fluorine atoms may be inclined to coordinate with silicone atoms. The distorted orientation may partially expose the hydrocarbon link of the pendant side chain. 

The solid-surface tension, indicated by a contact angle of a liquid drop (e.g., n-hexadecane, water, and methylene iodide) on the fluorosiloxane film on glass is different from the liquid-surface tensions. Siloxanes containing trifluoropropyl groups have a lower surface tension than the nonfluorinated siloxane [poly(dimethylsiloxane)] [152]. 

The cmc values of nonionic fluorosilicone surfactants having two trifluoropropyl groups are similar to those of methylsiloxane surfactants with a branched trisiloxane hydrophobe. However, surfactants containing three trifluoropropyl groups and those containing nonafluorohexyl radicals have higher cmc values, attributed to the bulkiness of the hydrophobe [142]. 

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