Perfluorinated chemicals long-Chain

EPA, Long-Chain Perfluorinated Chemicals (PECs) Action Plan (Dec. 30,2009)[hereinafter Action Plan PECs], available through http //www.epa.gov/oppt/existingchemicals/pubs/ actionplans/pfcs.html. 

U.S. Environmental Protection Agency (2009). Long-Chain Perfluorinated Chemicals (LCPFCs) Action Plan, http //www.epa.gov/opptintr/existingchemicals/pubs/actionplans/ pfcs.html. Accessed 15 December 2010... 

NMR studies it has been observed that the long molecular axis is nearly parallel to the para- x s of the phenyl moiety and hence the first few fragments of the chain attached to the indazole group are not along this axis. This requires that the alkoxy chain attached to the indazole group has at least six carbon atoms to promote liquid crystalline behaviour. The order parameters of 4 -cyanophenyl 4-heptylbenzoate have been obtained by using 2D-NMR spectroscopy.Linear relationships between C-chemical shifts and order parameters have been obtained. Phase behaviour of a mixture of this liquid crystal and its chain-perfluorinated analogue has also been studied. 

The dependency of the physico-chemical properties on the chain length causes a different distribution pattern for the different PFC. The longer the perfluorinated carbon chain, the higher the bio-concentration factors and the higher the tendency to adsorb to solid matrices. Thus short chain PFC are more likely to be found in aqueous matrices whereas long chain PFC are predominantly in solid matrices. 

The characteristics of fluoropolymers are summarized in Table 1. Thermal and chemical resistance is in general with most of plastics, elastomers and perfluorinated membranes. Weather resistance with the outdoor durability for more than 20 years is specific for fluorinated paint resins. Surface properties such as water and oil repellency are provided by acrylic polymer-based textile finishes and coatings with long-chain per-fluoroalkyl groups. Electrical properties as well as a low refractive index are important for optoelectronics applications like optical fibers. 

Perfluorinated ionomer membranes have also been developed by Asahi Chemical and the Asahi Glass Company and commercialised as Aciplex S and Flemion, respectively. The general properties of the long side chain perfluorinated ionomer membranes (e.g. Nafion, Flemion, Aciplex) and the short side chain perfluorinated ionomer membranes (e.g. Dow) are shown in Table 1.2. 

The introduction of perfluorinated groups generally favors microphase separation due to the immiscibility of fluorocarbons with hydrocarbons [66]. Norbornene derivatives with perfluorinated endgroups in the side chain were prepared by Wewerka et al. [67]. Monomer XII contained a relatively long (CF2)8-chain, separated via a long spacer (11 methylene-groups) from the norbornene, whereas monomer XIII has two relatively short (CH2)2(CF2)4-side chains (Fig. 11). Homopolymers and block copolymers were synthesized with one fluorinated monomer (XII or XIII) and one non-fluorinated non-liquid crystalline monomer (NBDE or COEN) with the Schrock-type initiators 4 and 5, respectively, leading to microphase-separated block copolymers. Table 9 and Table 10 summarize the physico-chemical properties of the homopolymers and block copolymers. 

Recently, scientific literature evidenced that different companies developed per-fluorosulfonic ionomers able to sustain 120°C operating conditions for long time. In some examples the relation with linear short side chain structure is evident, most of all 3M [32] and Solvay [33,34], in other cases the polymer structure is not described, like for Asahi Glass [35] or Asahi Kasey [36], Figure 17.7 summarizes the chemical formula of the most common perfluorinated ionomers. 

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