Fluorinated acrylic

Four fluorinated acrylates are presented in Table 4 [66, 67, 68, 69] to supplement the vmyl fluoride data Perfluoroacrylic acid [70] and methyl per-fluoroaciylate [69, 70] are both reported m the literature. The cts and trans isomers of fluoroethylenes are readily distinguished by the magnitude of their couphng constants, with trans typically more than 3 times the magnitude of cis... 

Macromolecules have also been specifically designed and synthesized for use as emulsifiers for lipophilic materials and as stabilizers in the colloidal dispersion of lipophilic, hydrocarbon polymers in C02. We have demonstrated the amphiphilicity of fluorinated acrylate homopolymers, such as PFOA, which contain a lipophilic, acrylate like backbone and C02-philic, fluorinated side chains (see Fig. 3) [103]. It has been demonstrated that a homopolymer which physically adsorbs to the surface of a polymer colloid prevents agglomeration by the presence of loops and tails (see Fig. 4) [113]. The synthesis of this type of... 

Herein we present the synthesis of two series of fluorinated acrylate polymers and copolymers derived from commercially available hexafluoro-2-hydroxy-2(4-fluorophenyl)propane. The solubility, film-forming ability, thermal stability, and water absorption in these polymers have been studied. 

Four new fluorinated acrylic or methacrylic monomers were readily accessible using the commercially available HFAF as a means of introducing 6F groups into the monomers. Its reaction with acryloyl or metacryloyl chloride, as shown in Figure 1.1, gave the new monomers I. 

Very recently we8 reported on a class of processable heavily fluorinated acrylic resins that exhibit dielectric constants as low as 2.10, very close to the minimum known values. In this chapter we report on the preparation of a series of processable heavily fluorinated acrylic and methacrylic homo- and copolymers that exhibit dielectric constants as low as 2.06, and the factors that affect the reduction of dielectric constant from structure-property relationships is elucidated.9... 

In this work we have demonstrated that a new class of heavily fluorinated acrylic and methacrylic resins can be efficiently synthesized and then cured to solid form with radical initiator at elevated temperatures. These cured resins were found to have low dielectric constants, which are close to the minimum known values for Teflon and Teflon AF. In contrast to tetrafluoroethylene, our monomers are processable owing to the fact that they are liquids or low-melting solids, and moreover are soluble in common organic solvents. Lower dielectric constants are obtained as fluorine contents on the polymer backbone or side chain increase, when acrylate is replaced by methacrylate, when ether linkages are present in the fluorocarbon, and when aromatic structure is symmetrically meta-substituted. 

Historically the widespread use of liquid and supercritical C02 has been limited by the low solubility of most nonvolatile materials at reasonably low pressures. However, studies carried out over a decade ago established the solubility of oligometric perfluoropolyethers and poly(chlorotrifluoroethylene) in liquid C02,12 and a few years later it was discovered that other highly fluorinated polymers such as fluorinated acrylates were also quite soluble in liquefied C02 at relatively low pressures.13... 

Among all remaining monomers, those containing (per)fluorinated side chains such as fluorinated acrylates, vinyl ethers or esters, maleimides and styrenic monomers are also very interesting and have been studied in (co)telo-merisation. Most of them have been previously reviewed [15]. However, they are not mentioned in this chapter. 

The advantage of these monoacrylates about the classical fluorinated acrylates [117] concerns the gem trifluoromethyl groups which are water repellant umbrella . 

Although CO2 dissolves many small molecules readily, it is a very poor solvent for most high molecular weight polymers. Currently, only amorphous or low melting fluoropolymers and silicone polymers are known to be very soluble in CO2 (T < 100 °C, P < 400 bar), or C02-philic, while many industrially important polymers are relatively insoluble. In 1992, we reported the successful homogenous free radical polymerization of a C02-philic fluorinated acrylate, 1,1-dihydroperfluorooctyl acrylate (FOA)2. Homogenous polymer synthesis in CO2 is fundamentally limited however, by the extremely low solubility of most polymers at readily accessible conditions. 

Here, we describe the use of vibrational spectroscopy to monitor the progress of polymerisation reactions in situ. Figure 1 shows the results of monitoring the polymerisation of an fluorinated acrylate ester similar to that used by DeSimone [1 la]. The reaction was carried out in scC02 (200 bar) with AIBN, a common radical initiator. Under these conditions both the monomer and the final polymer are soluble in scC02 so the mixture remains as a single phase throughout the reaction. 

Figure 1 FTIR spectra recorded over a period of 24 hr, showing the polymerisation of a fluorinated acrylate in scC02. X indicates the decay of a characteristic band of the monomer and T marks the growth of a band of the polymer.

Of a large number of possible fluorinated acrylates, the homopolymers and copolymers of fluoroalkyl acrylates and methacrylates are the most suitable for practical applications. They are used in the manufacture of plastic lightguides (optical fibers) resists water-, oil-, and dirt-repellent coatings and other advanced applications [14]. Several rather complex methods to prepare the a-fluoroalkyl monomers (e.g., a-phenyl fluoroacrylates, a-(trifluoromethyl) acrylic and its esters, esters of perfluoromethacrylic acid) exist and are discussed in some detail in [14]. Generally, a-fluoroacrylates polymerize more readily than corresponding nonfluorinated acrylates and methacrylates, mostly by free radical mechanism [15], Copolymerization of fluoroacrylates has been carried out in bulk, solution, or emulsion initiated with peroxides, azobisisobutyronitrile, or y-irradiation [16]. Fluoroalkyl methacrylates and acrylates also polymerize by anionic mechanism, but the polymerization rates are considerably slower than those of radical polymerization [17]. 

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