Fluorosilicon with groups

Furthermore, important and interesting investigations have been performed by Kobayashi and Owen [397] who prepared fluorosilicones with perfluorinated lateral group ... 

Furukawa et al. [21] examined a new synthetic method for fluorosilicones with a high content of fluoroalkyl side chains based on the hydrosilylation of fluorinated olefins with PHMS. They introduced perfluoro-octyl groups into silicone polymers in one step without using the cracking process usually used in the conventional method. Employing the same methodology, Furukawa et al. [22] prepared a series of fluorosilicone homopolymers with... 

Scheme 6.7 Synthesis of fluorosilicones with long chain fluoroalkyloxypropyl group substitution. Taken from Ref. [28],...

Fluorosilicones consist of PDMS backbones with some degree of fluoro-aliphatic side chains. The fluorinated group can be trifluoropropyl, nonafluorohexylmethyl, or fluorinated ether side group [78,28,79]. These polymers differ not only in substituent group, but also in the amount of fluoro-substitution relative to PDMS, the overall molecular weight and crosslink density, and the amount of branching. In most commercially available cases, these polymers are addition cure systems and the reactions are those discussed previously for silicone networks. 

One type of R substituent that features only briefly in these reviews but which is growing in importance is the fluoroalkyl-containing group. There is renewed interest in fluorosilicone materials of all types including silanes. In line with the well-recognized low surface tension of aliphatic fluorocarbon-containing species, the prime interest is in the area of surface energy control. Examples of such silanes of all three types (n = 1, 2 and 3) have been reported and the purpose of this review is to summarize recent (last decade) developments in this topic. 

The high values for the trifiuoropropyl group are surprising but correspond with the liquid surface tension of polytrifluoropropylmethylsiloxane [13], although not in line with its critical surface tension and solid surface tension. The low values for the longer fluoroalkyl groups are comparable to the lowest surface tension fluoropolymers and correspond well with the values for related preformed fluorosilicone polymers [14-15]. 

In this context, by the term fluorosilicone are meant polymers containing C-F bonds and Si-O bonds with hydrocarbon entities between them. Thus, the repeating structure may be generally written as [RfX (CH J (CH,)vSiOz, where Rf is the fluorocarbon group.59 Commercially available fluorosilicones are based on polymethyltri-fluoropropylsiloxane (PMTFPS), or more accurately poly[methyl (3,3,3-trifluoropropyl)siloxane]. In some cases PMTFPS is copolymerized with polydim-ethyl siloxane (PDMS) for cost/benefit balance.60 The manufacture of monomers for fluorosilicones is discussed in some detail in Reference 60. Fluorosilicone elastomers... 

Thicker sections can be cross-linked by hydrosilylation addition. This is the same chemistry used to produce fluorosilicone monomers with the vinyl functionality present on silicon. The catalyst reaction occurs between a vinyl group and silicone hydride.66 The advantage of this system is that it does not produce volatile by-products. On the other hand, the disadvantage is that it is available only as a two-part system.67 Recently, however, one-part, platinum-catalyzed products have been developed.66 The reaction is very rapid and at room temperature it is completed in 10 to 30 minutes. It is accelerated with increasing temperature and at 150°C (302°F) it is completed within a few seconds. This makes the compounds ideal for fast automated injection molding operations.68 One-part systems use the chemical complexing of the catalyst, which is activated at elevated temperatures, or its encapsulation into an impermeable shell, which is solid at room temperature and melts at elevated temperatures68... 

Fluorosilicones Polymers with chains of alternating silicon and oxygen atoms and trifluoropropyl pendant groups. Most are rubbers. 

Cure depths (z) at 25°C and constant humidities have been measured for the following materials - acetate-terminated fluorosilicone, PDMS with butanone ketoxime end groups, and two isocyanate hot melt adhesives. In all cases, z was found to be linear with the square root of time. 

Patwardhan, D. V. Zimmer, H. Mark, J. E., Synthesis and Surface Properties of Polybutadiene Chains End-Capped with Two Types of Fluorosilicon Groups. J. Macromol. Set, Chem. 1998, ASS, 1941-1955. 

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