Polymers ionomer synthesis

In order to solve this chemical stability problem, a new proprietary PFSA ionomer synthesis procedure has been developed at DuPont that results in a reduction of the reactive end groups. This approach has been referred as chemical stabilization (CS) technology. Fluoride emission from chemically stabilized polymer in a Fenton s test was found to be eight times lower than a nonchemically stabilized polymer. 

Gross-Linking. A variety of PE resins, after their synthesis, can be modified by cross-linking with peroxides, hydrolysis of silane-grafted polymers, ionic bonding of chain carboxyl groups (ionomers), chlorination, graft copolymerization, hydrolysis of vinyl acetate copolymers, and other reactions. 

Sulfonated EPDMs are formulated to form a number of rubbery products including adhesives for footwear, garden hoses, and in the formation of calendered sheets. Perfluori-nated ionomers marketed as Nation (DuPont) are used for membrane applications including chemical-processing separations, spent-acid regeneration, electrochemical fuel cells, ion-selective separations, electrodialysis, and in the production of chlorine. It is also employed as a solid -state catalyst in chemical synthesis and processing. lonomers are also used in blends with other polymers. 

Fang Z, Kennedy JP. Novel block ionomers. I. Synthesis and characterization of polyisobuty-lene-based block anionomers. J Polym Sci Part A Polym Chem 2002 40 3662-3678. 

Industrial production of perfluorinated ionomers, Nafion membranes, and all perfluorinated membranes is costly due to several factors first, the monomers used are expensive to manufacture, since the synthesis requires a large number of steps and the monomers are dangerous to handle. The precautions for safe handling are considerable and costly. Secondly, the PSEPVE monomer is not used for other applications, which limits the volume of production. The most significant cost driver is the scale of production. Today, the volume of the Nafion market for chlor-aUcali electrolysis (150,000 m year ) and fuel cells (150,000 m year ) is about 300,000 m year resulting in a production capacity of 65,000 kg year. When compared to large-scale production of polymers like Nylon (1.2 x 10 m year ), the perfluorinated ionomer membrane is a specialty polymer produced in small volumes. 

Investigations on Dow membranes can be found in Refs. [70-82]. Solvay Solexis has started a research and development project to create new ionomer membranes for fuel cells and other applications similar to the Dow concept. The development is based on Solexis s capability for producing sulfonylfluoridevinylether by a much simpler route than the original Dow synthesis [83]. The Solexis route is schematically represented in Figure 27.29 and the monomer can be produced on an industrial scale. The SSC monomer and TFE are copolymerized by free-radical polymerization to obtain the polymers in Figure 27.30 (named Hyflon Ion). 

Zhang B, Sun Q, Han M et al (2007) Synthesis and mesomorphic properties of side-chain liquid crystalline ionomers containing sulfonic acid groups. J Appl Polym Sd 104 304-309... 

A thermopolastic elastomer based on sulfonated-EPDM, S-EPDM, was developed in the 1970 s by Exxon and more recently by Uniroyal. Unlike the synthesis of the carboxylate ionomers described above, S-EPDM is prepared by a post-polymerization sulfonatlon reaction(28). Compared to the metal neutralized S-EPDM, the sulfonic acid derivative is not highly associated. The free acid materials possess low strengths and are less thermally stable. The metal salts of S-EPDM have properties comparable to crosslInked elastomers, but they do exhibit viscous flow at elevated temperatures. In the absence of a polar cosolvent, such as methanol, hydrocarbon solutions of the metal salts of S-EPDM are solid gels at polymer concentrations above several percent(31). With the addition of 1 to 5% alcohol the polymer solution becomes fluid with solution viscosities of the order of 10 to 100 poise. 

We are currently exploring new routes to the synthesis of ionomers with controlled architecture, i.e. with control over the amount and location of ionic groups in the polymer backbone. One of our main interests is the synthesis of ion containing block copolymers. The applicability of anionic polymerization in the synthesis of block copolymers and other well defined model systems is well documented (22-24) Not as well appreciated, however, is the blocky nature that certain emulsion copolymerizations may provide. Thus, we have utilized both anionic and free radical emulsion polymerization in the preparation of model ionomers of controlled architecture. In this paper, the synthesis and characteristics of sulfonated and carboxylated block ionomers by both free radical emulsion and anionic polymerization followed by hydrolysis will be discussed. 

Side chain chiral polyn rs (34, in Fig. 24) have been produced via active ester synthesis, by using soluble and crosslinked samjdes of copoly(AOTcp-styrene) (unpublished work). The resulting chiral polymers are of considerable interest in separation technology, and as auxiliary n dia for asymmetric synthesis. Fluorescent labeled polymers, polyelectrolytes and hydrophobically modified ionomers (e.g. and 36), are also readily available via active ester synthesis. 

Current membrane development focuses on perfluorinated ionomers, hydrocarbon and aromatic polymers and acid-base polymer complexes. Good recent reviews on membrane synthesis and experimental characterization can be found in this volume and for example in [23-29]. 

The second part, Chapters 2-9, is concerned with polymer blends, including mechanical blends, graft copolymers, block copolymers, ionomers, and interpenetrating polymer networks. The development of most chapters proceeds from synthesis to morphology, and then shows how morphology affects or controls the physical and mechanical behavior of the finished material. The most exciting development of the past decade, the electron microscope studies of the details of phase separation, is emphasized. 

For metal-containing polyesters of dimer acid, synthesis was carried out using various divalent metal ions. Metal-containing polyesters include diverse systems such as ionomers, polymer-bound coordinating ligands, organometallic polymers with metal as a part of polymer backbone, metal polymer composites, and metal-... 

T. Yasuda, K. Miyatake, M. Hirai, M. Nanasawa, M. Watanabe, Synthesis and properties of polyiniide ionomers containing sulfoalk-oxy and fluorenyl groups, J. Polym. Sci., Part A Polym. Chem. 43 (19) (2005) 4439-4445. 

The sol-gel synthesis of titanimn-silicon nanocomposites based on perfluorosulfonate ionomers was reported. Also the preparation of nanosized particles (10-50nm) derived from Ti(OR)4 and Zr(OR)4 within matrices of styrene/ 4-vinylphenol copolymer was performed via the sol-gel method. These approaches can also be used for the surface activation of polymers. For example, hydrofobic perfluorinated polymers such as polytetrafluoroethylene (PTFE) or copolymers of... 

Ding YS, Register RA, Yang C, Cooper SL. Synthesis and characterization of sulphonated polyurethane ionomers based on toluene diisocyanate. Polymer 1989 30(7) 1204-12. 

Wiesemann A, Zentel R, Pakula T (1992) Redox-active liquid-crystalline ionomers.l. Synthesis and rheology. Polymer 33(24) 5315-5320. doi 10.1016/0032-3861(92)90818-H... 

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