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`UF.1133P
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`DESCRIPTION
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`SULONATED POLYETHYLENE
`
`This invention was made with government support under W911NF-09-1-0290 awarded
`by the Army Research Office. The governmenthascertain rights in the invention.
`
`BACKGROUNDOF INVENTION
`
`Sulfonated polymers that include very strong acid groups or salts of the strong acid
`within a solid matrix have been used in applications as resins or membranes. Generally these
`sulfonated polymers are random copolymers, where a non-sulfonated homopolymer is converted
`by a random reaction into the desired sulfonated copolymer. Sulfonated polystyrene (SPS) has
`been used for more than seventy years and is widely used for ion-exchange resins and as a
`polymer
`bound
`catalyst.
`Other
`common
`sulfonated
`polymers
`are
`sulfonated
`polyetheretherketones (SPEEK),
`sulfonated polyphenylenesulfides (SPPS), and sulfonated
`polysulfones (SPSU). Commonsulfinated aliphatic polymers include Nafion and Hypaln, which
`are perflurinated and partially chlorinated polymers. Often the randomly placed highly polar
`functional groups aggregate in one portion of the structure, and remain aggregated in the
`
`environments that they are used.
`As the sophistication of applications for polymers evolves, the need for well-defined
`polymer microstructures ensues. For these applications, the methods of polymer synthesis must
`extend beyond the random placement of repeating units common to most chain growth
`copolymerizations of vinyl monomers, condensation copolymerization, or random polymer
`reactions. Vinyl copolymerizations, even whenperfectly alternating, have significantrestrictions
`to the number of covalently bonded carbon atoms between specific functionalized carbons,
`almost always three carbon atoms. The homopolymerization of functionalized dienes can also
`lead the structures equivalent to the alternating copolymerization of vinyl monomersbut results
`with separation of functional groups by only five carbon atoms.
`Ring-opening polymerizationsof specifically functionalized cycloalkene monomersalso
`give limited possibilities to the placementof specific units on the resulting chainsas the ability to
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`prepare a cyclic monomer becomesvery difficult and usually prohibitively expensive when the
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`size of the ring exceeds seven or eight atoms.
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`The ring opening metathesis copolymerization, ROMP, for example, of a carboxylic acid
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`functionalized cyclooctene with cyclooctene and subsequent hydrogenation of the double bounds
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`of the polymer formed upon olefin metathesis to yield polyethylene copolymers with between 2-
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`10 mol % acid groups was achieved by the copolymerization and subsequent hydrogenation of
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`an acid functionalized polymer. These materials were isolated as high-melting, semicrystalline
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`solids, as expected, affording strictly linear materials exhibiting varying levels of crystallinity
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`dependent on comonomerincorporation.
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`The acyclic diene metathesis polymerization, ADMET,of free acid dienes and protected
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`free acid dienes has been reported, for example, in Schwendeman ef al. Macromolecules 2004,
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`37, 4031-37 for ultimate formation of carboxylic acids directly substituted to polyethylene at
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`regular placements and Opperet al. Macromolecules 2009, 42, 4407-9 for ultimate formation of
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`phosphoric acids situated regularly along a polyethylene backbone via a phosphoric ester
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`intermediate.
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`The preparation of a polyethylene substituted with regularly spaced sulfonic acid groups
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`has not been achieved, even though the preparation of the sulfonic ester equivalent of the
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`phosphoric ester that permitted the formation of the regularly substituted phosphoric acid
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`polyethylene has been achieved. A methodto prepare a periodic or quasiperiodic sulfonic acid
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`substituted polyethylene would be of value for proton conducting membranes and other devices
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`where the regularity of substitution can allow specific organization without the uncontrolled acid
`
`aggregation common of random copolymersystems.
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`BRIEF DESCRIPTION OF DRAWINGS
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`Figure 1 shows an ADMETpolymerization of mono 1-alkoxysulfonyl ester substituted
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`a,@-diene or a ROMPpolymerization of a mono 1-alkoxysulfonyl ester substituted cycloalkene
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`to an unsaturated ester polymer and the subsequent hydrogenation and deprotection to a periodic
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`sulfonic acid polyethylene, according to an embodimentofthe invention.
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`Figure 2 shows polymerization of a mono alkoxysulfonyl ester substituted a,@-diene
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`monomerto a poly(alkoxysulfonyl ester substituted a,@-diene).
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`Figure 3 shows reduction of a poly(alkoxysulfonyl ester substituted a,@-diene) to a
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`sulfonated ester substituted polyethylene.
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`Figure 4 shows saponification of a sulfonated ester substituted polyethylene to a sulfonic
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`acid salt substituted polyethylene, according to an embodimentof the invention.
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`Figure 5 shows an idealized proton conducting membrane having a to a sulfonic acid
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`substituted polyethylene, according to an embodimentof the invention.
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`DETAILED DISCLOSURE
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`Embodiments of the invention are directed to periodic, quasiperiodic, and quasirandom
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`sulfonic acid or sulfonic acid salt substituted polyethylenes, their preparation, and membranesor
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`other devices therefrom. The preparation of periodic sulfonic acid substituted polyethylenes,
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`according to an embodimentof the invention, is shown in Figure 1. The sulfonic acid substituted
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`polyethylenes can be prepared by the acyclic diene metathesis (ADMET) polymerization of one
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`or more sulfonic ester substituted a,@-alkyldienes, where at least one methylene unit separates
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`the terminal ene groups from the sulfonic ester substituted methylene unit, subsequent
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`hydrogenation of the ene units in the resulting polymer, and subsequently the hydrolysis of the
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`sulfonic ester to the sulfonic acid. The ester may be a methyl, ethyl or propyl ester or the ester of
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`any other alcohol or phenol. The polymerization of the monomercan be carried out using any
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`known metathesis catalyst, for example, Schrock's catalyst (Mo(=CHCMe,Ph)(N-2,6-C6H3-i-
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`Pr2.)(OCMe(CF3)2)2), Grubbs'
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`first generation catalyst
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`(RuCl(=CHPh)(PCy3)2), or Grubbs’
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`second
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`generation
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`catalyst
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`(1,3-bis-(2,4,6-trimethylpheny])-2-imidazolidinylidene]
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`
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`dichloro(phenylmethylene)(tricyclohexyl-phosphine)ruthenium. Alternately,—ring-opening
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`metathesis polymerization (ROMP) can be performed using one or more sulfonic ester
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`substituted cycloalkenes where at least one methylene unit separates the ene from the methylene
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`with the sulfonic ester substituent. Generally, the cycloalkene is smaller than an eight membered
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`ring, which limits the separation of functional substituents along the chain. With even-numbered
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`ring sizes, the functional group cannot be placed with equi-sized methylene sequences along the
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`chain.
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`Hence,
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`for practical purposes,
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`the seven-membered ring is about
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`the largest
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`functionalized cycloalkene that can result in a periodic placement of functional groups, which
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`leads to a maximum of only six memthylene units separating the carbons containing the
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`functional group(s).
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`The preparation of the sulfonic ester substituted a,@-alkyldiene monomercan be carried
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`out as shown in Figure 2, and taught in Opper, K. Polyethylene Functionalized with Highly Polar
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`Groups. Ph.D. Dissertation, University of Florida, 2010, which is incorporated by referencein its
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`entirety. The monomer can be prepared, as shown in Figure 2, where x is the number of
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`methylene groups in the monoene reagent is the same or different, and is 1 to 20 or more. When
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`x is the same value, the resulting symmetric monomercan be used to prepare a polymerthatis
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`periodic.
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`Whenx is different, for example, an assymetric sulfonic ester substituted o,a-alkyldiene
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`monomer having an x and a y value that are different, a “quasiperiodic” polymer can be formed
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`where the separating methylene units in the substituted polyethylene can be only 2x+2, 2y+2,
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`and xt+y+2 in a 1:1:2 ratio but no other values are possible. Alternately, by employing two
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`symmetric sulfonic ester substituted a,@-alkyldiene monomers, one with two x lengthed
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`sequences and one with two y lengthed sequences, or an assymetric x and y monomerand a
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`symmetric x and x monomer, the repeating units sequences between functionalized methylenes
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`of the ultimate substituted polyethylene can be only 2x+2, 2y+2, and x+y+2, but the ratio of
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`these units can differ from a 1:1:2 ratio and the longer range order will be different from that
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`where there is a single asymmetric monomer. By tailoring the sequence lengths, for example,
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`where the values of x and y are sufficiently similar, for example, x is about 1.05y to about 1.2y,
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`or the proportion of y sequences is small, the disruption from periodicity may not prohibit a
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`desired organization of the polymerinto desired associations of the polymers. For example, in a
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`membrane similar to that using periodic polymers, by promoting defects from periodicity, the
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`processes of organization can be kinetically enhanced by the structural defects with little penalty
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`in the ultimate organized structure.
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`A “quasirandom”structure can occur where more than two x sequence lengths are
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`employed, for example, x, y and z sequences can be formed whenat least two sulfonic ester
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`substituted a,@-alkyldiene monomers, when at least one is assymetric, or when three sulfonic
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`ester substituted o,@-alkyldiene monomers of any type are employed.
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`Inherently, the method
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`employed for preparation of the polymers does not permit a sequence between functionalized
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`methylenes of less than four methylene units, a truly random copolymeris not possible with the
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`monomers described above. Alternately, di- or poly-sulfonic ester substituted a,w-alkyldiene
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`monomers could be constructed that could ultimately be combined alone or with sulfonic ester
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`substituted o,@-alkyldiene monomers to generate what approximates truly random sulfonic acid
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`units on a polyethylene chain.
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`After ADMET polymerization,
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`the poly(sulfonic ester substituted a,@-alkyldiene) is
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`reduced to the sulfonic ester substituted polyethylene. As shown in Figure 3, the hydrogenation
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`can be carried out in solution in the presence of Wilkenson’s catalyst at a high pressure of
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`hydrogen. The reduction is carried out with effectively complete conversion of the olefin. The
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`subsequent conversion of the sulfonic ester to the sulfonic acid or sulfonic salt was resistant to
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`previous efforts to cause this conversion.
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`It was discovered that by suspending the sulfonic ester substituted polyethylene in a
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`highly polar solvent in the presence of strong base, such as sodium hydroxide, the effective
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`saponification of the ester
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`to a sulfonic acid salt substituted polyethylene results. An
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`advantageouspolar solvent is dimethylsulfoxide, DMSO, which has a dipole moment of 3.96 D,
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`a dielectric constant of 47.24, and a pKa of 35. As shown in Figure 4, the saponification of the
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`ethyl ester proceeds cleanly in DMSO with the dissolving of the sulfonic acid salt substituted
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`polyethylene. This solvent does not dissolve the polyester but dissolves the poly acid.
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`In
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`contrast dimethylformamide (DMF) and dimethylacetamide (DMAc), which has a dipole
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`moment of 3.72 D, a dielectric constant of 37.78, and a pKa of 30, dissolves the ester and
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`reaction results in precipitation without complete saponification.
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`The sulfonic acid substituted polyethylene can be formed from the acid salt achieved
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`upon saponification. The salt can be the Na, Li, K, Cs, Rb or Fr. The sulfonic acid substituted
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`polyethylene can be converted into a salt upon reaction with a base, where the salt can be of a
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`monovalent, divalent or polyvalent cation. The salt can be a mixture of ions. Alternately, the
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`cations
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`can be organic cations,
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`for example,
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`tetraalkylammonium ions,
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`for example,
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`tetramethylammonium ionsor tetraethylammonium ions.
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`Advantageously, the periodic sulfonic acid substituted polyethylene or quasiperiodic
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`sulfonic acid substituted polyethylene can organize into a structure of lamella with acid channels,
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`as illustrated in Figure 5.
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`In this form the sulfonic acid substituted polyethylene, or a salt
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`thereof, can be employed as a membrane.
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`In the acid form, a proton conducting membrane can
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`be established where a proton can be transported across the membrane by exchange at the
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`sulfonic acid groups of the channels.
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`In the salt form, a membrane has the potential for ion
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`transport. Membranescan becast from solutions of the sulfonated polyethylene, according to an
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`embodimentof the invention.
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`The poly(sulfonic ester substituted a,@-alkyldiene) can be converted to poly(sulfonic acid
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`substituted a,w-alkyldiene) or poly(sulfonic salt substituted a,@-alkyldiene) in the manner that
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`the reduced equivalent is formed.
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`METHODS AND MATERIALS
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`All 'H NMR (300 MHz) and °C NMR (75 MHz) spectra were recorded on a Varian
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`Associates Mercury 300 spectrometer. Chemical shifts for 1H and 13C NMRwerereferenced to
`residual signals from CDCl; ('H = 7.27 ppm and °C= 77.23 ppm). Thin layer chromatography
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`(TLC) was performed on EMDsilica gel-coated (250 ym thickness) glass plates. Developed
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`TLC plates were stained with iodine adsorbed onsilica to produce a visible signature. Reaction
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`progress andrelative purity of crude products were monitored by TLC and 1H NMR.
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`High-resolution mass spectral (HRMS) data were obtained on a Finnegan 4500 gas
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`chromatograph/mass spectrometer using either the chemical
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`ionization (CI) or electrospray
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`ionization (ESI) mode.
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`Molecular weights and molecular weight distributions were determined by gel
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`permeation chromatography (GPC), performed using a Waters Associates GPCV2000 liquid
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`chromatography system equipped with a differential refractive index detector (DRI) and an
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`autosampler. These analyses were performed at 40 °C using two Waters Styragel HR-SE
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`columns (10 microns PD, 7.8 mm ID, 300 mm length) with HPLC grade THF as the mobile
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`phase at a flow rate of 1.0 mL/minute. Injections were made at 0.05-0.07 % w/v sample
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`concentration using a 220.5 wL injection volume. Retention times were calibrated versus narrow
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`molecular weight polystyrene standards (Polymer Laboratories; Amherst, MA).
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`Infrared spectroscopy was obtained using a Perkin-Elmer Spectrum One FT-IR outfitted
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`with a LiTaO3 detector. Samples were dissolved in chloroform and cast on a KBr disc by slow
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`solvent evaporation.
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`Differential scanning calorimetry (DSC) was performed using a TA Instruments Q1000
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`at a heating rate of 10°C/min under nitrogen purge. Temperature calibrations were achieved
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`using indium and freshly distilled n-octane while the enthalpy calibration was achieved using
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`indium. All samples were prepared in hermetically sealed pans (4-7 mg/sample) and were run
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`using an empty pan as a reference.
`received from Aldrich unless otherwise specified.
`All materials were used as
`Tetrahydrofuran (THF) was obtained from an MBraun solvent purification system. Lithium
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`diisopropyl amide (LDA) was prepared prior to monomer synthesis. Grubbs’ first generation
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`ruthenium catalyst,
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`bis(tricyclohexylphosphine)benzylidine
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`ruthenium(IV)dichloride, was
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`received from Materia, Inc. Wilkinson’s rhodium catalyst, RhCl(PPh3)3, was received from
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`Strem Chemical. Synthesis of synthon 11-bromoheneicosa-1,20-diene was synthesized using the
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`procedure of Boz et al., Macromolecules 2006, 39, 4437-47.
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`Ethyl tricosa-1,22-diene-12-sulfonate). In a flame dried 3-necked flask equipped with a
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`magnetic stir bar, 2.5mL (20 mmol, | eq) of ethyl methane sulfonate and 4.4mL (20 mmol, | eq) of
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`11-bromoundecenewerestirred in 20 mL of dry THF under argon. After bringing the solution to -78
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`°C, 0.9 eq of LDA was added dropwise over 30 minutes and stirred for 30 additional minutes. The
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`solution was then warmed to 0 °C andstirred for 1 to 2 hours until mono-alkylation was observed
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`and alkenyl bromide disappeared by TLC. After bringing the solution back to -78 °C, 0.9 eq of 11-
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`bromoundecene was added slowly and allowed to dissolve. With the solution at -78 °C, 0.9 eq of
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`LDA was added dropwise over 30 minutes and stirred for 30 additional minutes. The solution was
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`then warmedto 0 °C andstirred for 2 to 3 hours until the conversion from mono-alkylation to diene
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`product was no longer observed. The reaction was quenched by adding ice cold water. This mixture
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`wasthen extracted (3 x 50 mL) with diethyl ether, dried over magnesium sulfate and concentrated to
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`a colorless oil. Column chromatography, using 1:19 diethyl ether:hexane as the eluent, afforded
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`dialkylation product in 30% recovered yield. Substitution of diglyme for THF resulted in a 60%
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`recovered yield.
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`‘*H NMR (CDCI3): 6 (ppm) 1.29 (br, 32H), 1.41 (t, 3H), 2.05 (q, 4H), 2.98 (p, 1H),
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`4.28 (q, 2H), 4.92-5.03 (m, 4H), 5.75-5.81 (m, 2H). °C NMR (CDC\3): 8 (ppm) 15.47, 26.83, 29.14,
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`29.15, 29.33, 29.52, 29.65, 29.70, 61.45, 65.47, 114.35, 139.41. HRMScaled for C2sH4s038 [M-
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`C2Hs]- (m/z), 399.2901; found, 399.2917. Anal. Caled for C25H4s03S: C, 70.04; H 11.29; O, 11.20; 8,
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`7.48 found: C, 69.99; H, 11.33
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`Ethyl undeca-1,10-diene-6-sulfonate. 'H NMR (CDCl,): 6 (ppm) 1.39 (t, 3H), 1.56 (m, 4H),
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`1.65 (m, 2H), 2.05 (m, 2H), 2.12 (g, 4H), 2.98 (p, 1H), 4.28 (q, 2H), 4.97-5.06 (m, 4H), 5.72-5.83 (m,
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`2H). ®C NMR (CDCI3): 6 (ppm) 15.41, 25.94, 28.52, 33.62, 61.11, 65.58, 115.49, 137.92. HRMS
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`caled for C13H2403S [M+H} (m/z), 261.1519; found, 261.1527. Anal. Caled for C13H2403S: C,
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`59.96; H 9.29; O, 18.43; S, 12.31 found: C, 59.96; H, 9.40
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`Homopolymerization
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`In a flame dried 50 mL round bottom flask, an exact amount of monomer was weighed.
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`Using a 400:1 monomer:catalyst ratio (0.25 mol%), Grubbs’ first generation catalyst was added
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`and mixed into the monomerwhile under a blanket of argon. A magnetic stir bar was placed into
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`the mixture while a schlenk adapter wasfitted to the round bottom. After sealing the flask under
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`argon it was moved to a high vacuum line. The mixture was stirred and slowly exposed to
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`vacuum over an hour at room temperature. After stirring for an hour at room temperature under
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`eventual high vacuum (10-3 torr), the flask was lowered into a pre-warmed 50 °C oil bath for an
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`appropriate number of days allowing removal of ethylene bubbling through viscous polymer.
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`Polymers were quenched by dissolution of polymer in an 1:10 ethyl vinyl ether:toluene solution
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`under argon. Uponprecipitation into an appropriate solvent, the polymers wereisolated.
`Polymerization of Ethyl tricosa-1,22-diene-12-sulfonate. 1H NMR (CDCI3): 8 (ppm)
`1.29 (br, 32H), 1.41 (br, 3H), 1.96 (br, 4H), 2.97 (p, 1H), 4.29 (q, 2H), 5.39 (br, 2H). °C NMR
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`(CDCI3): 6 (ppm) 15.47, 26.85, 27.46, 29.16, 29.42, 29.57, 29.65, 29.71, 29.74, 29.91, 30.01,
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`32.84, 61.46, 65.49, 130.56. GPC data (THF vs. polystyrene standards): Mw = 63900 g/mol;
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`P.D.I. (Mw/Mn) = 1.8.
`Polymerization of Ethyl undeca-1,10-diene-6-sulfonate.
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`'H NMR (CDCI3): 8 (ppm)
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`1.40 (t, 3H), 1.51 (m, 4H), 1.67 (m, 2H), 1.90 (m, 2H) 2.05 (m, 4H), 2.98 (p, 1H), 4.29 (q, 2H),
`5.41 (m, 2H). °C NMR (CDCI3): 8 (ppm) 15.47, 26.60, 26.72, 27.26, 28.62, 29.67, 32.52, 61.17,
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`65.68, 129.80, 130.33. GPC data (THF vs. polystyrene standards): Mw = 22700 g/mol; P.D.I.
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`(Mw/Mn) = 2.1.
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`Hydrogenation
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`A solution of unsaturated polymer was dissolved in toluene and degassed by bubbling a
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`nitrogen purge through thestirred solution for an hour. Wilkinson’s catalyst [RhCl(ppn3)3] was
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`added to the solution along with a magnetic stir bar, and the glass sleeve was sealed in a Parr
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`reactor equipped with a pressure gauge. The reactor was filled to 700 psi hydrogen gas and purge
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`three times while stirring, filled to 500 psi hydrogen, and stirred for an appropriate number of
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`days. After degassing the solution,
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`the crude solution was isolated, precipitated into an
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`appropriate solvent.
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`Hydrogenation to yield poly(Ethy! tricosyl-12-sulfonate):
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`1H NMR(CDC13): 8 (ppm) 1.29 (br, 41H), 1.41 (br, 3H), 2.97 (p, 1H), 4.29 (q, 2H). 13C
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`NMR(CDCI3): 6 (ppm) 15.45, 26.82, 29.13, 29.55, 29.72, 29.78, 29.85, 29.94, 61.44, 65.48
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`Hydrogenation to yield poly(Ethy! undecyl-6-sulfonate):
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`ow™
`O=S=0
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`derekn
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`1H NMR (CDCI13): 5 (ppm) 1.38 (br, 12H), 1.40 (t, 3H), 1.69 (m, 2H), 1.90 (m, 2H),
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`2.98 (p, 1H), 4.29 (q, 2H) 13C NMR (CDCI3): 8 (ppm) 15.41, 25.94, 28.52, 33.62, 61.11, 65.58
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`Saponification
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`Individually, the polymers were suspended in DMSOand solid NaOH was added with
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`stirring. Over time the polymers dissolved with the release of ethanol to form poly(sodium
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`tricosyl-12-sulfonate) or poly(sodium undecyl-6-sulfonate).
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`All publications referred to or cited herein are incorporated by reference in their entirety,
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`includingall figures and tables, to the extent they are not inconsistent with the explicit teachings
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`of this specification.
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`It should be understood that the examples and embodiments described herein are for
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`illustrative purposes only and that various modifications or changes in light thereof will be
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`suggested to personsskilled in the art and are to be included within the spirit and purview ofthis
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`application.
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