Fluoro-substituted polymers

Fluoro-substituted Polymers. The fluoropolymers were between the first to be studied by the XPS technique because the substitution of F atom(s) in the -CH.-CH - unit induced very large modifications in the XPS core level spectra (shifts up to 8eV) that were easy to detect and interpret. The XPS valence band spectra of similar compounds, namely poly(vinyl fluoride) (PVF), poly(vinylidene fluoride) (PVF2), poly(trifluoroethylene) (PVF3), and poly(tetrafluoroethylene) (PTFE) (26, 27, 28) are also expected to reflect the induction of such strong electronic effects at the valence molecular level. 

The first phosphazene polymers containing carbon (79), sulfur (80,81), and even metal atoms (82) in the backbone have been reported. These were all prepared by the ring-opening polymerization of partially or fully chloro-substituted (or fluoro-substituted) trimers containing one hetero atom substituting for a ring-phosphoms atom in a cyclotriphosphazene-type ring. 

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. 

Substituted-PPVs and a number of PPV copolymers have been synthesized, illustrated in Scheme 46, using the Heck reaction shown above [178-180]. Of these polymers both the phenyl-substituted PPV and the biphenylene vinylenes are soluble in organic solvents while the methyl-, trifluoromethyl-, nitro- and fluoro-substituted analogs displayed poor solubility. 

With other substitutes group instead of alkyl side chains, the energy levels of acceptor polymer can be modified to match that of donor materials. Fluoro-substituted n-type conjugated polymers were introduced for all-polymer solar cells with the highest reported energy conversion efficiency of 6.71% at the state of art (Jung et al, 2015). 

On the other hand, cis or trans and cyclic 1,2-disubstituted ethylenes have been well-known till 1980 to be not homopolymerized with a radical initiator owing to the much more increased steric effect of the substituents except for a few exceptions, e.g., fluoro-substituted ethylenes and cyclic derivatives, vinylene carbonate (VCa), maleic anhydride (MAn), yV-substituted maleimides (RMI), and acenaphthylene. However, if 1,2-disubstituted and tri- or tetra-substituted ethylenes can homopolymerize, the polymers with a substituted polymethylene structure, which is different from the above polyethylenes, would be obtained (eqs. 1 and 2), i.e., the polymers would be less flexible (more rigid), and have higher glass transition temperatures than those for the polyethylenes, although their processabilities would decrease. 

J. G. Killiam, Y. Gofer, H. Sarker, T. O. Poehler and P. C. Searson, Electrochemical synthesis and characterization of a series of fluoro-substituted phenylene-2-thienyl polymers, Chem. Mater., 11, 1075-1082 (1999). 

Fluoro-substituted silole-containing polymers were recently prepared by Suzuki polycondensation reaction using 2,5-dihydroxyboryl-l,l-dimethyl-3,4-bis(3-fluorophenyl)-silole or l,3-dibromo-5-fluoro-benzene as fluoro-containing monomers and 2,7-dibromo-9,9-dioctyl-fluorene or 2,5-dihydroxyboryl-l,l-dimethyl-3,4-bis(phenyl)-silole as co-monomers [221]. With a polymerization... 

Horst S, Evans NR, Bronstein HA, Williams CK (2009) Synthesis of fluoro-substituted sUole-containing conjugated materials. J Polym Sci A Polym Chem 47 5116-5125... 

Pees B., Sindt M., Paul J.M. Mieloszynski J.L. (2002). Synthese et caracteiisation physico-chimiques de polyaaylates d (0-p>erfluorooctyl-atkyle effet p ir- impair. Eur. Polym. Jour, vol.38, n°5, p>p. 921-931 (May 2002), ISSN 0014-3057 Pees B., Paul J.M., Oget N, Sindt M., Mieloszynski J.L. (2003). Synthesis of fluoro-substituted monomers bearing a functionalised lateral chain. Part 2 Preparation of sulfoxides and sulfones containing monomers, J. Fluor.Chem., voLl24, n°2, pp.l39-146 (December 2003) ISSN 0022-1139... 

Fluoro-substituted di lacetylenes can be readily prepared by this method and they undergo nucleophilic substitution with displacement of the fluoride, in the presence of excess potassium t-butoxide, to give the t-butyl ethers." The ethers can be readily converted to the phenols by removal of the t-butyl groups. On reaction of 4,4 -difluorodiphenyl acetylene with bisphenates, such as that from BPA 9, high molecular weight linear polymers are formed. ... 

Imid azolin-2-ones polymers, 1, 296 synthesis, 5, 466, 491 Imidazolium cations, 2-fluoro-nucleophilic substitution, 5, 413 Imidazolium chloride, 4-amino-l-methyl-2,3-diphenyl-... 

The feasibility of bonding pyridinyl groups to silicon which contains a hydrolytically sensitive functional group has recently been demonstrated 15-71. 2-Fluoro-3-(dimethylchlorosilyl)pyridine and 3-fluoro-4-(dimethylchloiosilyl)pyridine as well as 2-, 3-, and 4-(dimethylchlorosilyl)pyridine were prepared by the reaction of the corresponding lithiopyridines with excess Me2SiCl2- Hydrolysis of the pyridinyl substituted chlorosilanes gave disiloxanes which were insoluble in water. In the present report we will describe extension of this work to include pyridinyl dichlorosilanes which can be hydrolyzed to polysiloxanes. These polymers can be N-oxidized and the resultant derivatives have been shown to be effective hydrophobic transacylation catalysts. 

A variation of this method led to the generation of bis-benzimidazoles [81, 82], The versatile immobilized ortho-phenylenediamine template was prepared as described above in several microwave-mediated steps. Additional N-acylation exclusively at the primary aromatic amine moiety was achieved utilizing the initially used 4-fluoro-3-nitrobenzoic acid at room temperature (Scheme 7.72). Various amines were used to introduce diversity through nucleophilic aromatic substitution. Cyclization to the polymer-bound benzimidazole was achieved by refluxing for several hours in a mixture of trifluoroacetic acid and chloroform. Individual steps at ambient temperature for selective reduction, cyclization with several aldehydes, and final detachment from the polymer support were necessary in order to obtain the desired bis-benzimidazoles. A set of 13 examples was prepared in high yields and good purities [81]. 

Three poly(aryl ethers) were prepared and used as coblocks in imide copolymerizations. The first coblock prepared was poly(aryl ether phenylquinoxaline), since this material has the requisite high Tg ( 280 °C) and thermal stability, and the polymer can be processed from solution or the melt. The synthesis of po-ly(aryl ether phenylquinoxalines) involves a fluoro-displacement polymerization of appropriately substituted fluorophenylquinoxalines with bisphenols, us-... 

The selective electrophilic aromatic substitution carried out by displacement of a metallic substituent (Hg, Sn) ( F-fluorodemetallation) using [ F]p2 or [ F]AcOF remains a method of choice to introduce a fluorine atom on a specific position. In the early preparations of [6- F]fluoro-L-DOPA, the reaction of a 6-substituted mercuric derivative with [ F]acetyl hypofluorite yielded the expected compound in 11 % yield [73,74]. Reaction of a mercuric precursor, free or on a modified polystyrene support P-CH2-COOHg(DOPA precursor) allows the preparation of [ F]fluoro-L-DOPA in an overall yield up to 23 %. The polymer supports are easily prepared, require no special treatment for storage and are convenient to use in automated production [75]. 

Further research on the substitution of the thiophene 3-position with phenyl groups containing electron-withdrawing or electron-donating groups (such as methyl, methoxy, fluoro, chloro, bromo, trifluoromethyl, sulfoxy) in the para position have lead to polymers with unique features [57]. The electron-withdraw-ing groups allow the formation of a radical anion and thus stabilize the n-doped state. As a result, such conducting polymers can be reversibly oxidized and reduced and electrochromic devices can be built with identical anode and cathode materials [58]. 

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