High Dimensional Stability and Alcohol Resistance Aromatic Poly(aryl

Subscriber access provided by Macquarie University

Article

High Dimensional Stability and Alcohol Resistance Aromatic Poly(aryl ether ketone) Polyelectrolyte Membrane Synthesis and Characterization Di Liu, Yunji Xie, Su Li, Xiaocui Han, Haibo Zhang, Zheng Chen, Jinhui Pang, and Zhenhua Jiang ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.8b01557 • Publication Date (Web): 13 Feb 2019 Downloaded from http://pubs.acs.org on February 14, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Energy Materials

High Dimensional Stability and Alcohol Resistance Aromatic Poly(aryl ether ketone) Polyelectrolyte Membrane Synthesis and Characterization Di Liu, Yunji Xie, Su Li, Xiaocui Han, Haibo Zhang, Zheng Chen, Jinhui Pang,* and Zhenhua Jiang

Laboratory of High Performance Plastics (Jilin University), Ministry of Education. National & Local Joint Engineering Laboratory for Synthesis Technology of High Performance Polymer. College of Chemistry, Jilin University, Changchun, 130012, P. R. China.

ABSTRACT: Crystallized sulfonated poly(arylene ether ketone)s (Cr-SPAEKs) materials constructed from dense sulfonated hydrophilic

segments and crystalline poly(ether ketone) (PEK) hydrophobic backbone were designed. The membrane exhibited considerable proton

conductivity and superb solvent resistance owing to its special phase morphology, the presence of a wide hydrophilic proton transport channel,

and a crystalline hydrophobic matrix. The dense sulfonated hydrophilic segment provides excellent proton conductivity; the Cr-SPAEK-20 membrane exhibits higher proton conducting ability than Nafion 117 in the temperature range of 20-100 oC, the proton conductivity of Cr-SPAEK-20 reaches about 168 mS cm-1 at 100 oC. The crystalline PEK hydrophobic segment ensures superior solvent resistance and

dimensional stability, guaranteeing the durability of the membrane in practical applications. The methanol permeability of Cr-SPAEK-20 is only

one-eighth that of Nafion 117 when the test conditions are the same. The direct methanol fuel cell (DMFC) which assembled by Cr-SPAEK-20

exhibited satisfactory open circuit voltage and maximum power density during the testing process. The Cr-SPAEK membranes have shown

potential for DMFCs as polymer electrolyte materials.

KEYWORDS: poly(aryl ether ketone), alcohol resistance, proton exchange membranes, crystalline PEK backbone, direct methanol fuel cell

■ INTRODUCTION As the continuous consumption of fossil fuel and emission of greenhouse gas, the fuel cell has been brought into focus as a means of

1

ACS Paragon Plus Environment

ACS Applied Energy Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 28

production for clean energy. 1-3 Among many kinds of fuel cell, the proton exchange membrane fuel cells (PEMFCs) have been seen as a promising device and have been extensively researched in these years. 4-5 Proton exchange membranes (PEMs), as an important component of PEMFCs, not only function to transfer protons, but also prevent fuel penetration.6 At present, the most widely used

polyelectrolyte membrane is the perfluorosulfonic acid (PFSA) membrane, which has advantages such as high proton conducting ability, superior chemical and mechanical stability. 7-9 However, PFSA membrane also has some defects, for example: poor alcohol

resistance, rapid decrease of proton conducting ability at relative high operating temperature, and most importantly-high cost, these all limit the large-scale practical applications of PFSA membrane.7

In order to find alternative materials for high cost PFSA polymers, many kinds of sulfonated hydrocarbon polymers have emerged, such as sulfonated poly(ether ketone)s, 10-14 sulfonated poly(ether sulfone)s, 15-17 sulfonated poly(phenylene)s, 18-19 and sulfonated polyimides.20-22 Such materials have received widespread attention due to their advantages, such as outstanding mechanical properties, good stability, low fuel permeability and low cost.23-24 However, the problem with the majority of these polymers is that high proton

conductivities usually depends on the high ion exchange capacities (IECs), which is different form PFSAs, resulting in lager water absorption and dimensional change, poor mechanical properties and alcohol resistance. 25-26 From the molecular design perspective, arbitrary distribution of SO 3- groups usually hinders the backbone from forming a connected hydrophobic phase. 27-29 Therefore, in order to make the PEMs have excellent proton conductivity, proper water uptake and swelling, more and more research has been

conducted from the viewpoint of microscopic phase morphology.

At present, there are many ways to improve the microscopic phase separation morphology of proton exchange membranes. One strategy is to synthesize the multi-block polymers.30-33 Sulfonated multi-block polymers, due to their structural advantages of

alternating sulfonated hydrophilic segments and hydrophobic backbones, have excellent proton conductivity even in relatively low

relative humidity environments. This is due to the unique structure that allows the membrane to exhibit well-defined microscopic phase

separation morphology. Nonetheless, synthesis of different molecular weight and control of sequence of hydrophilic and hydrophobic

2


Page 3 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


segments are relatively complicated. Hence, the disadvantages described above result in an increase in the cost of the sulfonated

multi-block polymer, thereby limiting its extensive development to some extent. Another strategy is to synthesize the densely sulfonated polymers.16, 34-36 Each repeating unit of this type of sulfonated polymer comprises at least two ion-conducting groups. The concentrated distribution of SO3- groups facilitates the formation of large ion clusters, which provides favorable conditions for the formation of distinct hydrophilic-hydrophobic phase morphology. This good microscopic morphology is very beneficial for improving

proton conductivity. However, when IEC is high, dense sulfonated polymers tend to form large-sized ion clusters, causing excessive

water absorption to reduce dimensional stability.

23, 37

Moreover, when the membrane is applied to a DMFC, its large hydrophilic

domain will also reduce the alcohol resistance.

In order to overcome these problems and improve the overall performance of the dense sulfonated polymer membranes, improving the

strength of hydrophobic backbone could be an effective way. An effective method is to introduce a cross-linked structure, but the cross-linked membranes have the solubility problem. 38-39 Another strategy is to introduce a crystal structure into the polymer system.40-41

Holdcroft

et

al.42-43

prepared

a

series

of

crystalline

polymers,

such

as

sulfonated

poly(vinylidene

difluoride-co-chlorotrifluoroethylene)-g- polystyrene. The results show that the dimensional stability is effectively improved with the crystallization domains increase.42-43 Winey et al.44 developed a sulfonated polyethylene with well-controlled chain folding. The

folding of the controllable polyethylene chains can produce a regular crystalline structure and form the desired ion transpor t channels, thereby providing favorable conditions for the proton transport in the polymer. 44 As a crystalline material, poly(ether ketones) (PEKs)

has been seen a kind of special engineering thermoplastics, which possess multiple excellent performances, such as excellent

mechanical properties, highly thermal and chemical stability.

In order to introduce a crystalline structure into the sulfonated polymer, a crystalline polymer is initially constructed, then introducing

the sulfonic acid groups through a selective functionalization process. In general, previously prepared crystalline PEK generally require

relatively high temperatures to overcome the solubility problem of the oligomer. However, various side reactions caused by high

3



Page 4 of 28

reaction temperatures can cause the molecular weight distribution of the polymer to become uneven even cross-linked. Another

possible method is to first prepare an amorphous polymer precursor at a lower temperature and then carry out a simple reaction to

obtain the desired crystalline polymer. N-phenyl (4,4'-difluorodiphenyl) ketimine is determined to be a monomer in the synthetic route of amorphous polymer precursors. 40, 45-47 The synthesis of the polymer using ketimine instead of benzophenone can not only lower the

reaction temperature but also avoid the formation of the crystalline structure. The amorphous polymer precursor synthesized by

ketimine can be hydrolyzed in an acidic environment to obtain a sulfonated polymer containing a crystalline hydrophobic backbone.

This synthetic process makes it easier to obtain the crystallized SPAEKs. In combination with the previous study of sulfonated poly(arylene ether ketone)s,26, 36, 48-50 we hereby propose a series of crystallized

sulfonated poly(arylene ether ketone)s (Cr-SPAEKs), which not only contain dense sulfonated hydrophilic segments but also contain

crystallized PEK hydrophobic segments. The dense sulfonated hydrophilic segment provides a guarantee for the membrane to have

proper proton conductivity; the crystalline PEK hydrophobic backbone ensures that the membranes exhibit excellent solvent resistance.

Its special phase morphology effectively improved the overall performance of the Cr-SPAEK-x membrane. The performance was also

improved by operating DMFC with synthesized Cr-SPAEK-20 polymer membranes.

■ RESULTS AND DISCUSSION Synthesis of PAEKt-x precursor.

PAEKt-x was synthesized of 4,4'-dihydroxybenzophenone, N-phenyl(4,4′-difluorodiphenyl) ketimine (monomer a) (Scheme S1), and

4,4'-bis(4-(4-((4-phenol)diphenylmethyl)phenoxyl)phenyl)ketone (monomer b) (Scheme S2) by a nucleophilic polycondensation

reaction, while x is the molar ratio of monomer b contrast to all of the bisphenol repeating units (Scheme 1). PAEKt-x could be

dissolved in common organic reagents, e.g., DMAc, CHCl3, NMP (Table S1). The molecular weights of the copolymer precursors were tested by gel permeation chromatography (GPC). Table 1 exhibited the Mn, Mw, and PDI of PAEKt-x precursors. Mn ranged

4


Page 5 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


from 52000 to 67000 and Mw from 74000 to 104000, demonstrating that this series of polymers were successfully synthesized. 1H

NMR spectroscopy was used to characterize the chemical structure of PAEKt-15 (Figure 1a) and all protons of it could be accurately assigned compared with the 1H NMR spectrum of monomer a and monomer b (Figure S1 and S5). Due to the effect of electron

withdrawing by some specific groups (-C=N- or -C=O), H2, H2’, H9, H16 were considered to be at the highest chemical shift (7.75― 7.90 ppm). H3 and H3' were observed at 6.72―6.79 ppm. Scheme 1. Synthesis of the PAEKt-x precursors and Cr-SPAEK-x Polymers.

Table 1. Molecular weights of the PAEKt-x polymers.

Polymer

Mn (104 g mol-1)

Mw (104 g mol-1)

PDI

PAEKt-10

6.2

10.4

1.68

PAEKt-15

6.7

9.8

1.47

PAEKt-20

5.2

7.4

1.41

5



a)

Page 6 of 28

b)

c)

d)

Figure 1. a) 1H NMR spectrum of PAEKt-15. b) FT-IR spectrum of PAEKt-15 and Cr-SPAEK-x polymers. c) XRD patterns of Cr-SPAEK-x

polymers in dry state. d) TGA results of PAEKt-15 and Cr-SPAEK-x polymers obtained in a N2 atmosphere.

Sulfonation of PAEKt-x.

We chose chlorosulfonic acid as the sulfonation reagent and a series of crystalline polymers (Cr-SPAEK-x) (Scheme 1) with high

6


Page 7 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


degree of sulfonation were prepared. The densely packed activated phenyl groups could be easily sulfonated by chlorosulfonic acid. The carbonyl group could prevent the attack of benzene by chlorosulfonic acid. 26,

51-52

After being washed with water, we were

pleasantly surprised to find that the obtained sulfonated polymers were insoluble in conventional polar reagents (such as DMAc,

CHCl3, DMF), indicating that a hydrolysis process took place and the ketimine was converted to ketone, forming crystalline PEK hydrophobic moieties. We choose DCA as a solvent for membrane casting and acidified it with a sulfuric acid solution (the hydrolysis

process also occurred) to finally obtain membranes of uniform thickness (Table 2). To verify that the hydrolysis process has been

carried out, we validated our conclusions using the FT-IR and the XRD tests. Figure 1b shows the FT-IR spectrum of PAEKt-15 precursor and Cr-SPAEK-x polymers. There was a C=O vibration peak at 1654 cm -1 for the polymer before and after sulfonation. Due to the introduction of SO3- groups, all sulfonated polymers had strong characteristic peaks at 1038 and 1095 cm-1, which are corresponded to S=O stretch and symmetric O=S=O stretch, respectively. Consistent with the expectation, no significant decrease was observed in the C=N peak intensity because the peak of C=C in benzene overlapped with the peak of C=N at ~ 1590 cm-1. However,

the C=O signal peaks of all sulfonated polymers were enhanced, reflecting the success of the hydrolysis reaction. The IEC is a

parameter representing the ion exchange capacity of the membranes. The theoretical and experimental IEC values for Cr-SPAEK-x are

listed in Table 2. After sulfonation, since the Cr-SPAEK-x polymers contained crystals and were insoluble in conventional organic solvents, 1H NMR characterization could not be performed. Therefore, to investigate the degree of sulfonation of Cr-SPAEK-x

polymers, 4,4'-bis(4-(4-(4-methoxyphenyl)diphenylmethyl)phenoxy)benzophenone was selected as a model compound and subjected to sulfonation (Scheme S3). 1H NMR spectroscopy (Figure S6) exhibited that all of the reactive phenyl were introduced with sulfonic

acid groups. This also indicated that the Cr-SPAEKt-x polymers would have a high degree of sulfonation.

Table 2. IEC values, membrane thicknesses, crystallinity and TGA results of Cr-SPAEK-x.

Polymer

Thickness (m)a

IECb (meq. g-1)

IECc (meq. g-1)

7


Crystallinity (%)

Td5% (°C)


a

Page 8 of 28

Cr-SPAEK-10

61 (65)

1.53

1.32

15.5

315.6

Cr-SPAEK-15

70 (74)

2.04

1.76

11.2

302.5

Cr-SPAEK-20

68 (73)

2.44

2.10

-

285.7

The values inside and outside the parentheses represent the thickness of the wet and dry membranes, respectively. b Theoretical IEC value. c Calculated from

acid-base titration.

Crystallinity analysis with XRD.

In order to investigate the crystalline nature of Cr-SPAEK-x polymers, analysis was carried out using wide-angle XRD (Figure 1c). It is well known that PEK has characteristic peaks at 19.1, 21.1, 23.5, and 29.5°.53 The hydrolyzed Cr-SPAEK-10 and Cr-SPAEK-15

polymer membranes exhibited characteristic peaks of PEK, indicating that the C=N bond was successfully hydrolyzed to C=O bond,

forming a PEK backbone. As shown in Table 2, the degrees of crystallization of Cr-SPAEK-x were calculated. It can be seen that as

the IEC value increases, the characteristic peak of PEK gradually became smooth, indicating that the amorphous domain gradually

increased and the crystallinity decreased. Due to the lowest content of PEK segment, the Cr-SPAEK-20 membrane did not show

obvious characteristic peaks. However, all membranes were insoluble in the conventional organic solvent, indicating that a small

amount of crystal structure remained inside Cr-SPAEK-20 (Table S1).

Thermal properties.

Excellent thermal performance is an important assurance for the application of membrane in the real operating environment, so we

used TGA to characterize the thermal properties of PAEKt-15 and Cr-SPAEK-x membranes. As seen in Table 2, all Cr-SPAEK-x

polymers exhibited satisfactory 5% weight loss temperatures (＞285°C). With the increase of IEC, the acid content of the sulfonated

8


Page 9 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


polymers increase, and their stability decrease, resulting in a gradual decrease in T d5%. Figure 1d shows the TGA results of PAEKt-15 and Cr-SPAEK-x. PAEKt-15 only has a thermal decomposition temperature around 500°C, whereas the TGA curve of the sulfonated Cr-SPAEK-x polymers exhibited two weight loss temperatures at lower temperatures: The decomposition of the SO3- group results in the first weight loss stage which was around 250°C; and the second weight loss at about 500°C was caused by the degradation of the

aromatic polymer backbone. The test results prove that Cr-SPAEK-x exhibits satisfactory thermal-resistance performance and have

high potential value for long-term application in fuel cells.

Water uptake and swelling ratios.

Water management has an important impact on the overall performance of polymer membranes. Since the amount of SO3- groups directly affects the IEC, IEC plays a key role in the hydration behavior. In addition, the difference in the hydrophilic regions and

hydrophobic backbone of polymer membranes can have a large impact on the hydration behavior of the membranes. The hydrophobic

backbone acts as a mechanical support for the membrane, so the formation of a dense and continuous hydrophobic region is very

advantageous to control dimensional. Hence, it is necessary to select a suitable hydrophobic backbone so that the membrane has good

hydrophilic and hydrophobic phase-separation morphology. The densely packed crystalline domains reinforce the hydrophobic

framework, improving the stability of the membrane while avoiding excessive absorption of water molecules. Therefore, Cr-SPAEK-x

membranes maintain the hydration behavior at an appropriate level. The water uptakes and swelling ratios data of Cr-SPAEK-x

membranes were plotted as a line graph shown in Figure 2 and summarized in detail in Table S2. The water uptake values of all

Cr-SPAEK-x polymer membranes show a tendency to increase with temperature and IEC (Figure 2a). Due to the higher IECs, the WUs of Cr-SPAEK-15 and Cr-SPAEK-20 were higher than Nafion 117, which was also caused by a higher number of SO3- groups. The WUs of Cr-SPAEK-10 was lower than that of Nafion 117 because of its greater degree of crystallization (Figure 1c), which

effectively restricted the absorption of water.

9



Page 10 of 28

The swelling ratios in length and thickness of Cr-SPAEK-x membranes were depicted in Figure 2b and Figure 2c, respectively. As can

be seen, the Cr-SPAEK-20 membrane exhibited isotropic swelling behavior, ranging from 13.4 to 46.4% and from 9.5 to 35.7% in

length and thickness, respectively. In contrast, Cr-SPAEK-10 and Cr-SPAEK-15 membranes showed anisotropic swelling behavior. For example, Cr-SPAEK-15 exhibited 15.8% swelling in length at 80 oC, whereas its thickness swelling was 21.0%, which is almost 1.5

times than former. Another sample Cr-SPAEK-10 showed stronger anisotropic swelling behavior. Compared with 2.0-3.6% change in

length, the swelling ratios in thickness of the membrane were from 2.3 to 9.3%. The difference in swelling behavior between

Cr-SPAEK-x membranes might due to more crystalline structure in the Cr-SPAEK-10 and Cr-SPAEK-15 than that of Cr-SPAEK-20.

By combine the omnidirectional swelling changes, we produced the volume swelling ratios of Cr-SPAEK-x, as depicted in Figure 2d

with Nafion 117 as comparison. Consistent with the behavior of swelling in length and thickness, the Cr-SPAEK-15 membrane

exhibited lower volume swelling than Nafion 117 at 20-80°C. Although the Cr-SPAEK-15 membrane possessed higher WU (49.3%)

which was almost twice than that of Nafion 117 (29.4%) at 80°C, its volume swelling (62.5%) is still lower than later (70.37%),

demonstrating that the crystalline backbone limited the swelling behavior to some extent. Due to the low degree of crystallization, the

Cr-SPAEK-20 membrane has poor water management and high volume swelling ratio, especially at high temperature. However, due to

the most crystalline structure in the series of copolymers, Cr-SPAEK-10 exhibited excellent dimensional stability in the whole range of

temperature. Its swelling change is far below the Nafion 117 no matter which orientation. As a result, the crystalline domain of

Cr-SPAEK-x membranes effectively suppressed the excessive swelling, and maintained their dimensional stability.

10


Page 11 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


a)

b)

c)

d)

Figure 2. a) The water uptake, b) Swelling of length, c) Swelling of thickness, and d) Volume swelling of Cr-SPAEK-x and Nafion 117

membrane with temperature as a variable, respectively.

Proton conductivity.

11



Page 12 of 28

For polymer electrolyte membranes, conductivity is a key physical quantity that is greatly affected by water management. Sufficient

water uptake facilitates the construction of hydrophilic domains within the polymers. However, dilution of the ion-conducting groups

caused by excessive swelling will reduce proton conductivity and destroy the integrity of hydrophobic region, resulting in poor

membrane durability. The introduction of a crystalline PEK backbone can effectively control the swelling of polymer membranes and

avoid ion dilution.

The data for Cr-SPAEK-x membranes and Nafion 117 measured under full hydration condition are plotted as a line graph shown in

Figure 3a and summarized in detail in Table S2. The proton conductivities of all Cr-SPAEK-x membranes showed a gradual increase

with IEC due to the large amount of ion-conducting groups. Since high temperatures can promote membrane hydration and proton

diffusion, proton conductivity gradually increases as the temperature increases. The Cr-SPAEK-20 membrane exhibited higher proton conducting ability than that of Nafion 117 in the temperature range of 20-100 oC, and the highest proton conductivity of Cr-SPAEK-20 reached about 168 mS cm-1 at 100 oC. However, although the Cr-SPAEK-15 membrane has a higher water absorption capacity, the

proton conductivity was lower than Nafion 117, which might due to the crystalline structure caused a negative influence on proton conducting, since it could hinder ion transport through the amorphous phase. 54-55

The relationship between proton conductivity and relative humidity of Cr-SPAEK-x and Nafion 117 was depicted in Figure 3b. This

figure clearly shows that Cr-SPAEK-20 has relatively prominent proton conductivity within the relative humidity range of the test.

Especially when RH surpassed 80%, the proton conductivity of Cr-SPAEK-20 exceeded that of Nafion 117. Even if the RH was reduced to 50%, the proton conductivity of Cr-SPARK-20 (0.017 S cm-1) could be at the same level as Nafion 117 (0.028 S cm-1). Thus,

Cr-SPAEK-20 showed high proton conduction at RH condition. This might due to the strong ability of water uptake (as depicted in

Figure 2a) and well-defined microscopic phase separation morphology.

In summary, the Cr-SPAEK-x membranes possess relatively high ability of proton conduction, especially for Cr-SPAEK-20. Its proton

conductivity exceeds Nafion 117 when placed in the fully hydrated condition, and comparable with Nafion 117 under relative humidity

12


Page 13 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


environment.

a)

b)

Figure 3. Proton conductivities of Cr-SPAEK-x and Nafion 117 a) in deionized water with temperature as a variable, and b) under relative

humidity conditions at 80 °C.

Methanol permeability, methanol uptake, methanol swelling ratios, and proton conductivity in methanol solution.

An important advantage of the crystalline PEMs developed in this study is their excellent alcohol resistance. As a proton exchange

membrane applied to DMFCs, methanol permeation, methanol uptake, and methanol swelling behavior are parameters that need to be

evaluated. All Cr-SPAEK-x membranes exhibited excellent methanol uptake (Figure 4a) and swelling behavior (Figure 4b). As the

range of IEC values and methanol concentration increased, the methanol uptakes and swelling ratios of membranes increased.

Although Cr-SPAEK-15 and Cr-SPAEK-20 membranes had higher methanol uptake than Nafion 117, their methanol swelling ratios

13



Page 14 of 28

were still well controlled. This further proved that the existence of the PEK crystal backbone plays an important role in controlling

swelling behavior.

Methanol permeability (Table 3) and water behavior exhibit the same pattern because a wide ion domain is more conducive to the

transport of methanol. However, the presentation of the crystalline backbone simultaneously effectively enhanced the alcohol

resistance of the Cr-SPAEK-x membranes. The methanol permeation of Cr-SPAEK-x membranes showed a tendency to increase with the increase of IEC. Even at the highest IEC (2.10 meq. g-1), Cr-SPAEK-20 still has a moderate methanol permeability of only 2.2× 10-7 cm2 s-1. However, under the same test conditions, Nafion 117 had a methanol permeability of up to 16.8×10-7 cm2 s-1. Overall, the

alcohol resistance of the Cr-SPAEK-x membranes is excellent, indicating that the densely packed crystalline domains effectively block

the diffusion of methanol.

The proton conductivities of Cr-SPAEK-x membranes in different concentrations of methanol solution were shown in Figure 4c. As

the IEC increased, the proton conductivities of all Cr-SPAEK-x membranes in the methanol solution gradually increased, exhibiting the

same trend of conductivity in deionized water. However, the proton conductivities of Cr-SPAEK-x membranes exhibited an opposite

trend compared with the change of methanol concentration. This was because as the methanol concentration increased, the protons of

water ionization gradually decreased. In addition, compared to Nafion 117, it can be seen clearly that the proton conductivity of

Cr-SPAEK-20 in methanol solution was higher than that of Nafion 117, further reflecting the good proton conductivity of

Cr-SPAEK-20. In summary, the various properties of Cr-SPAEK-x membranes in methanol solutions have shown satisfactory results,

suggesting their potential for use in DMFCs.

14


Page 15 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


b)

a)

c)

d)

Figure 4. a) The methanol uptakes, b) Methanol swelling, and c) Conductivities in methanol solution of Cr-SPAEK-x and Nafion 117,

respectively. d) SAXS results of Cr-SPAEK-x membranes.

15



Page 16 of 28

Morphology.

The hydrophilic-hydrophobic microscopic phase morphology of proton exchange membranes can have a large impact on macroscopic properties.56 Therefore, it is important to develop a well-defined microscopic phase-separation structure for proton exchange

membranes. Here, Small-angle X-ray scattering (SAXS) was used to investigate the internal structure and the aggregation of

hydrophilic ion clusters of the Cr-SPAEK-x membranes. Prior to testing, using lead acetate solution to selectively stain the sulfonated

ion clusters of membranes, resulting in a strong contrast between the hydrophilic and the hydrophobic domains, which could enhance

scattering intensity. As shown in Figure 4d, the test curves for all Cr-SPAEK-x membranes displayed distinct peaks, which were

similar with the curve of Nafion 117, reflecting that the nano-phase separation between the hydrophilic and hydrophobic domains has been formed.57 However, the ionomer peaks of Cr-SPAEK-x were the same or a little broader compared with Nafion 117, indicating a

little wider distribution of ionic clusters in Cr-SPAEK-x membranes. Besides, the characteristic separation length (d) were also listed in Figure 4d, which represent the distances between the centers of ion clusters. 58 It is apparent that IEC has an effect on these d values. Consistent with the research results of Jannasch,59 the characteristic separation length decreases with the ratio of IEC increases. It can

be seen that the d values of this series of membranes decreased from 9.8 nm for Cr-SPAEK-10 to 7.6 nm for Cr-SPAEK-20. This trend

may be attributable to the increase ionic content forming more intensive ion clusters, reducing the characteristic separation length. In

addition, the higher ion content of these polymer membranes also makes distribution of ion clusters closer. Such well-defined

microscopic phase separation morphology greatly influences the macroscopic properties of Cr-SPAEK-x membranes.

Mechanical properties and oxidative stability.

Mechanical property is also a parameter which cannot be negligible to ensure the long-term effective use of membranes in PEMFC

applications. As shown in Table 3, the dry membrane exhibited satisfactory mechanical properties. Before beginning the mechanical

test of dry membranes, the samples were dried at 120 °C and then placed in the specific environment (room temperature and 30% 16


Page 17 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


relative humidity) to balance and test. Whether it is tensile strength or elongation at break, the test results were related to the IEC.

Among them, the tensile strength of the Cr-SPAEK-15 membrane is large due to the relatively high molecular weight. In general, all

Cr-SPAEK-x membranes exhibited proper mechanical property to meet the requirements of PEM materials used in DMFCs.

Table 3. Methanol permeabilities, selectivity, oxidative stabilities, and mechanical properties of Cr-SPAEK-x.

IEC (meq. Polymer g-1)

a

Methanol permeabilitya (10-7 cm2 s-1)

Selectivity (105 S s

Tensile strength

Elongation at break

cm-3)

(MPa)

(%)

RW (%)b

τ (h)c

Cr-SPAEK-10

1.32

0.7

2.0

46.0±3.5

6.10±0.8

99.9

6.0

Cr-SPAEK-15

1.76

1.7

2.2

60.3±4.1

18.4±1.6

99.2

5.75

Cr-SPAEK-20

2.10

2.2

2.6

44.3±2.8

23.3±2.1

95.4

5.5

6F-SPAEK-10d

1.26

-

-

-

-

98.4

3.75

6F-SPAEK-15d

1.68

-

-

-

-

97.4

2.75

6F-SPAEK-20d

2.06

-

-

-

-

90.5

0.83

Nafion 117

0.91

16.8

0.3

-

-

98.4

>24

Measured in 10M methanol solution at room temperature. b Residual weight after immersion in Fenton's reagent at 80°C for 1 h. c The time of the membranes to

begin disintegrating. d Data from ref. 23, the structure of the polymer in this article is shown in Figure S8.

During the practical working process of fuel cells, the fuel of cathode generates HO• and HOO• free radicals which will attack the

proton exchange membrane, resulting in degradation and decrease in durability. In order to visually reflect the state of all Cr-SPAEK-x

membranes after stability test, Figure S9 shown the images of the membranes after 1 hour of oxidation stability test. Table 3 shown

that all Cr-SPAEK-x membranes exhibited excellent stability, which might due to their densely stacked crystalline structure. The

residual weights (RWs) of all Cr-SPAEK-x samples after experiencing oxidative stability test were above 95.4% in 1 h, while 17



Page 18 of 28

flexibility and transparency of membranes were still remained. All membranes did not show degradation within 5.5 h, indicating that they have good oxidative stability. Our group has previously prepared polymers with similar structures to the polymers in this article. 26

They have the same hydrophilic structure and different hydrophobic structure. It can be found from the data in Table 3 that the

oxidation stability of crystallized Cr-SPAEK-x membranes was much better than that of amorphous 6F-SPAEK-x membranes. It has

further been demonstrated that the crystalline hydrophobic backbone provides the possibility of improving the stability of th e

membrane and provides a guarantee for the stable operation of the PEMs materials used in DMFCs.

Selectivity and Fuel cell performance.

When evaluating the performance of PEMs in DMFCs, proton conductivity and alcohol resistance are usually evaluated

comprehensively, introducing the concept of selectivity. Selectivity is the ratio of proton conductivity to methanol permeability.

Obviously, when the membrane has both high conductivity and excellent alcohol resistance, that is, the higher selectivity, it can exhibit

excellent fuel cell performance in practical DMFC applications. As listed in Table 3, when IEC value increased, the selectivity of the

Cr-SPAEK-x membrane gradually increased, thanks to their good proton conductivity and low methanol penetration. In summary, this

series of membranes had a much higher selectivity than that of Nafion 117, which guarantees its application in DMFCs.

Considering their good overall performance, Cr-SPAEK-x polymer membranes show great potential in practical application for

DMFCs. Therefore, the Cr-SPAEK-20 membrane was subjected to membrane electrode assembly and tested for DMFC performance.

Figure 5 shown the single-cell polarization curves of Cr-SPAEK-20 and Nafion 117 membrane-assembled DMFCs using 2 M or 4 M

methanol solutions as anode fuel. When membranes are used in direct methanol fuel cell testing, their performance is related to many

factors. Therefore, optimization of conditions is necessary to achieve excellent cell performance. As a well-known material, the

optimization of Nafion 117 in cell performance testing was quite good. However, as a new material, the conditions of the

Cr-SPAEK-20 membrane were not optimized enough, resulting in no excellent test results. However, in view of the good proton

18


Page 19 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


conduction and excellent alcohol resistance of the Cr-SPAEK-20 membrane, the membrane will exhibit better cell performance when

the test conditions of the membrane are optimized. In addition, it is worth mentioning that when the concentration of the methanol

solution was increased from 2M to 4M, the OCV of the Cr-SPAEK-20 membrane was maintained at a certain level and the maximum

power density was flat or even better. This may be due to its dense crystalline hydrophobic structure, which greatly reduces the

penetration of methanol. In comparison, the overall performance of Nafion 117 was significantly weakened, which was directly related

to its poor alcohol resistance. Overall, the performance indicates the potential application of Cr-SPAEK-x polymer membranes in

DMFCs.

a)

b)

19



c)

Page 20 of 28

d)

Figure 5. Single-cell performance of Cr-SPAEK-20 (a, b) and Nafion 117 (c, d) using 2 M or 4 M methanol and O2 as fuel and oxidant at 25°C and 60°C, respectively.

■ CONCLUSIONS Crystallized sulfonated poly(arylene ether ketone)s constructed from crystalline poly(ether ketone) (PEK) hydrophobic segments and

dense sulfonated hydrophilic segments were developed and applied to DMFCs. XRD and solubility tests indicate that the membrane

has a crystalline structure, which causes a moderate level of water absorption and swelling. The highest proton conductivity of Cr-SPAEK-20 membrane is 168 mS cm-1 at 100°C. Furthermore, the introduction of the crystalline structure controls methanol

absorption and swelling at a very low level; the Cr-SPAEK-20 membrane has moderate methanol permeability, which is far superior to

Nafion 117. Additionally, the membrane also exhibits excellent thermal stability, oxidative stability, and mechanical properties, which

guarantee its durability in practical applications. Finally, the performance of a single cell using the Cr-SPAEK-20 membrane was

evaluated. The results demonstrate that the crystalline SPAEK polymer membranes are promising PEMs in DMFC applications.

20


Page 21 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


■ ASSOCIATED CONTENT Supporting Information

The Supporting Information is available free of charge on the ACS Publications website at DOI:

Experimental details and additional experimental data (PDF)

■ AUTHOR INFORMATION Corresponding author

Jinhui Pang (J Pang)

Email: [email protected].

Tel.: +86 431 85168199

Fax: +86 431 85168199

Notes

The authors declare no competing financial interest.

■ ACKNOWLEDGMENTS This research was financially supported by the program of China National Science Foundation (21774048).

■ REFERENCES (1) Pfeffer, M. G.; Kowacs, T.; Wachtler, M.; Guthmuller, J.; Dietzek, B.; Vos, J. G.; Rau, S. Optimization of Hydrogen-Evolving

Photochemical Molecular Devices. Angewandte Chemie 2015, 54, 6627-6631.

(2) Amstutz, V.; Toghill, K. E.; Powlesland, F.; Vrubel, H.; Comninellis, C.; Hu, X.; Girault, H. H. Renewable Hydrogen Generation

21



Page 22 of 28

from a Dual-Circuit Redox Flow Battery. Energy Environ. Sci. 2014, 7, 2350-2358.

(3) Vermaas, D. A.; Veerman, J.; Saakes, M.; Nijmeijer, K. Influence of Multivalent Ions on Renewable Energy Generation in Reverse

Electrodialysis. Energy Environ. Sci. 2014, 7, 1434-1445.

(4) Manthiram, A.; Vadivel Murugan, A.; Sarkar, A.; Muraliganth, T. Nanostructured Electrode Materials for Electrochemical Energy

Storage and Conversion. Energ Environ Sci 2008, 1, 621.

(5) Park, C. H.; Lee, C. H.; Guiver, M. D.; Lee, Y. M. Sulfonated Hydrocarbon Membranes for Medium-Temperature and

Low-Humidity Proton Exchange Membrane Fuel Cells (PEMFCs). Progress in Polymer Science 2011, 36, 1443-1498.

(6) Devanathan, R. Recent Developments in Proton Exchange Membranes for Fuel Cells. Energ Environ Sci 2008, 1, 101-119.

(7) Mauritz, K. A.; Moore, R. B. State of Understanding of Nafion. Chem Rev 2004, 104, 4535-4585.

(8) Hickner, M. A.; Ghassemi, H.; Kim, Y. S.; Einsla, B. R.; McGrath, J. E. Alternative Polymer Systems for Proton Exchange

Membranes (PEMs). Chem Rev 2004, 104, 4587-4611.

(9) Ling, X.; Bonn, M.; Parekh, S. H.; Domke, K. F. Nanoscale Distribution of Sulfonic Acid Groups Determines Structure and

Binding of Water in Nafion Membranes. Angew Chem Int Edit 2016, 55, 4011-4015.

(10) Xie, Y.; Liu, B.; Chen, Z.; Han, X.; Liu, B.; Zhang, H.; Pang, J.; Jiang, Z. Graft Fluorinated Poly(arylene ether ketone)s

Containing Highly Dense Sulfonic-Acid-Functionalized Pendants for Proton Exchange Membranes by C-N Coupling. Polymer 2017,

131, 84-94.

(11) Lin, L.; Chen, Z.; Zhang, Z.; Feng, S.; Liu, B.; Zhang, H.; Pang, J.; Jiang, Z. New Comb-Shaped Ionomers based on Hydrophobic

Poly(aryl ether ketone) Backbone Bearing Hydrophilic High Concentration Sulfonated Micro-Cluster. Polymer 2016, 96, 188-197.

(12) Pang, J.; Jin, X.; Wang, Y.; Feng, S.; Shen, K.; Wang, G. Fluorinated Poly(arylene ether ketone) Containing Pendent

Hexasulfophenyl for Proton Exchange Membrane. Journal of Membrane Science 2015, 492, 67-76.

(13) Anderson, L. J.; Yuan, X.; Fahs, G. B.; Moore, R. B. Blocky Ionomers via Sulfonation of Poly(ether ether ketone) in the

22


Page 23 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Semicrystalline Gel State. Macromolecules 2018, 51, 6226-6237.

(14) Wang C, Zhou Y, Shen B, Zhao X, Li J and Ren Q. Proton-conducting Poly(ether sulfone ketone)s containing a High Density of

Pendant Sulfonic Groups by a Convenient and Mild Post-sulfonation. Polym. Chem. 2018, 9, 4984-4993.

(15) Fu, L.; Xiao, G.; Yan, D. Sulfonated Poly(arylene ether sulfone)s with Phosphine Oxide Moieties: A Promising Material for

Proton Exchange Membranes. ACS applied materials & interfaces 2010, 2, 1601-7.

(16) Feng, S.; Shen, K.; Wang, Y.; Pang, J.; Jiang, Z. Concentrated Sulfonated Poly (ether sulfone)s as Proton Exchange Membranes. J

Power Sources 2013, 224, 42-49.

(17) Yoo, T.; Aziz, M. A.; Oh, K.; Shanmugam, S. Modified Sulfonated Poly(arylene ether) Multiblock Copolymers containing Highly

Sulfonated Blocks for Polymer Electrolyte Membrane Fuel Cells. Journal of Membrane Science 2017, 542, 102-109.

(18) Zhang, X.; Sheng, L.; Higashihara, T.; Ueda, M. Polymer Electrolyte Membranes Based on Poly(m-phenylene)s with Sulfonic

Acid via Long Alkyl Side Chains. Polym. Chem. 2013, 4, 1235-1242.

(19) Adamski, M.; Skalski, T. J. G.; Britton, B.; Peckham, T. J.; Metzler, L.; Holdcroft, S. Highly Stable, Low Gas Crossover,

Proton-Conducting Phenylated Polyphenylenes. Angewandte Chemie-International Edition 2017, 56, 9058-9061.

(20) Yao, H.; Zhang, Y.; Liu, Y.; You, K.; Song, N.; Liu, B.; Guan, S. Pendant-Group Cross-Linked Highly Sulfonated Co-polyimides

for Proton Exchange Membranes. Journal of Membrane Science 2015, 480, 83-92.

(21) Chen, J.-C.; Wu, J.-A.; Lee, C.-Y.; Tsai, M.-C.; Chen, K.-H. Novel Polyimides Containing Benzimidazole for Temperature Proton

Exchange Membrane Fuel. Journal of Membrane Science 2015, 483, 144-154.

(22) Ono, Y.; Goto, R.; Hara, M.; Nagano, S.; Abe, T.; Nagao, Y. High Proton Conduction of Organized Sulfonated Polyimide Thin

Films with Planar and Bent Backbones. Macromolecules 2018, 51, 3351-3359.

(23) Li, N.; Guiver, M. D. Ion Transport by Nanochannels in Ion-Containing Aromatic Copolymers. Macromolecules 2014, 47,

2175-2198. 23



Page 24 of 28

(24) Kreuer, K.-D. Ion Conducting Membranes for Fuel Cells and other Electrochemical Devices. Chem Mater 2013, 26, 361-380.

(25) Wang, F.; Hickner, M.; Kim, Y. S.; Zawodzinski, T. A.; McGrath, J. E. Direct Polymerization of Sulfonated Poly(arylene ether

sulfone) Random (Statistical) Copolymers: Candidates for New Proton Exchange Membranes. Journal of Membrane Science 2002, 197,

231-242.

(26) Xie, Y.; Liu, D.; Li, D.; Han, X.; Li, S.; Chen, Z.; Zhang, H.; Pang, J.; Jiang, Z. Highly Proton Conducting Proton-Exchange

Membranes based on Fluorinated Poly(arylene ether ketone)s with Octasulfonated Segments. Journal of Polymer Science Part A:

Polymer Chemistry 2018, 56, 25-37.

(27) Jutemar, E. P.; Jannasch, P. Locating Sulfonic Acid Groups on Various Side Chains to Poly(arylene ether sulfone)s: Effects on the

Ionic Clustering and Properties of Proton-Exchange Membranes. Journal of Membrane Science 2010, 351, 87-95.

(28) Shin, D. W.; Guiver, M. D.; Lee, Y. M. Hydrocarbon-Based Polymer Electrolyte Membranes: Importance of Morphology on Ion

Transport and Membrane Stability. Chem Rev 2017, 117, 4759-4805.

(29) Peckham, T. J.; Schmeisser, J.; Rodgers, M.; Holdcroft, S. Main-Chain, Statistically Sulfonated Proton Exchange Membranes: The

Relationships of Acid Concentration and Proton Mobility to Water Content and Their Effect Upon Proton Conductivity. Journal of

Materials Chemistry 2007, 17, 3255–3268.

(30) Badami, A. S.; Lane, O.; Lee, H.-S.; Roy, A.; McGrath, J. E. Fundamental Investigations of The Effect of The Linkage Group on

The Behavior of Hydrophilic-Hydrophobic Poly(arylene ether sulfone) Multiblock Copolymers for Proton Exchange Membrane Fuel

Cells. Journal of Membrane Science 2009, 333, 1-11.

(31) Shin, D. W.; Lee, S. Y.; Lee, C. H.; Lee, K.-S.; Park, C. H.; McGrath, J. E.; Zhang, M.; Moore, R. B.; Lingwood, M. D.; Madsen,

L. A.; Kim, Y. T.; Hwang, I.; Lee, Y. M. Sulfonated Poly(arylene sulfide sulfone nitrile) Multiblock Copolymers with Ordered

Morphology for Proton Exchange Membranes. Macromolecules 2013, 46, 7797-7804.

(32) Li, N.; Lee, S. Y.; Liu, Y.-L.; Lee, Y. M.; Guiver, M. D. A New Class of Highly-Conducting Polymer Electrolyte Membranes:

24


Page 25 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Aromatic ABA Triblock Copolymers. Energy Environ. Sci. 2012, 5, 5346-5355.

(33) Roy, A.; Yu, X.; Dunn, S.; McGrath, J. E. Influence of Microstructure and Chemical Composition on Proton Exchange Membrane

Properties of Sulfonated-Fluorinated, Hydrophilic-Hydrophobic Multiblock Copolymers. Journal of Membrane Science 2009, 327,

118-124.

(34) Pang, J.; Shen, K.; Ren, D.; Feng, S.; Wang, Y.; Jiang, Z. Polymer Electrolyte Membranes based on Poly(arylene ether)s with

Penta-Sulfonated Pendent Groups. J. Mater. Chem. A 2013, 1, 1465-1474.

(35) Skalski, T. J.; Britton, B.; Peckham, T. J.; Holdcroft, S. Structurally-Defined, Sulfo-Phenylated, Oligophenylenes and

Polyphenylenes. J Am Chem Soc 2015, 137, 12223-6.

(36) Feng, S. N.; Wang, G. B.; Zhang, H. B.; Pang, J. H. Graft Octa-Sulfonated Poly(arylene ether) for High Performance Proton

Exchange Membrane. J Mater Chem A 2015, 3, 12698-12708.

(37) He, G.; Li, Z.; Zhao, J.; Wang, S.; Wu, H.; Guiver, M. D.; Jiang, Z. Nanostructured Ion-Exchange Membranes for Fuel Cells:

Recent Advances and Perspectives. Advanced materials 2015, 27, 5280-5295.

(38) Wang, L.; Li, K.; Zhu, G.; Li, J. Preparation and Properties of Highly Branched Sulfonated Poly(ether ether ketone)s Doped with

Antioxidant 1010 as Proton Exchange Membranes. Journal of Membrane Science 2011, 379, 440-448.

(39) Xie, H.; Tao, D.; Ni, J.; Xiang, X.; Gao, C.; Wang, L. Synthesis and Properties of Highly Branched Star-Shaped Sulfonated Block

Polymers with Sulfoalkyl Pendant Groups for Use As Proton Exchange Membranes. Journal of Membrane Science 2016, 497, 55-66.

(40) Chen, Y.; Lee, C. H.; Rowlett, J. R.; McGrath, J. E. Synthesis and Characterization of Multiblock Semi-Crystalline Hydrophobic

Poly(ether ether ketone)-Hydrophilic Disulfonated Poly(arylene ether sulfone) Copolymers for Proton Exchange Membranes. Polymer

2012, 53, 3143-3153.

(41) Feng, S. A.; Pang, J. H.; Yu, X. W.; Wang, G. B.; Manthiram, A. High-Performance Semicrystalline Poly(ether ketone)-Based

Proton Exchange Membrane. ACS applied materials & interfaces 2017, 9, 24527-24537.

25



Page 26 of 28

(42) Yang, A. C. C.; Narimani, R.; Zhang, Z.; Frisken, B. J.; Holdcroft, S. Controlling Crystallinity in Graft Ionomers, and Its Effect on

Morphology, Water Sorption, and Proton Conductivity of Graft Ionomer Membranes. Chem Mater 2013, 25, 1935-1946.

(43) Yang, A. C. C.; Narimani, R.; Frisken, B. J.; Holdcroft, S. Investigations of Crystallinity and Chain Entanglement on Sorption and

Conductivity of Proton Exchange Membranes. Journal of Membrane Science 2014, 469, 251-261.

(44) Trigg, E. B.; Gaines, T. W.; Marechal, M.; Moed, D. E.; Rannou, P.; Wagener, K. B.; Stevens, M. J.; Winey, K. I. Self-Assembled

Highly Ordered Acid Layers in Precisely Sulfonated Polyethylene Produce Efficient Proton Transport. Nature materials 2018, 17,

725-731.

(45) Britt E. Lindfors, R. S. M., James E. McGrath. Heterogeneous Hydrolysis of Poly(ary1 ether ketimine)s-An Alternative Synthetic

Route to Semicrystalline Poly(ary1 ether ketone)s. Makromol. Chem., Rapid Commun. 1991, 12, 337-345.

(46) A. E. Brink, S. G., T. Lin, H. Marand, K. Lyon, T. Hua, R. Davis and J. S. Riffle. Fine Polymeric Powders from Poly(arylene ether

ketone)s. Polymer 1993, 34, 825-829.

(47) Jacques Hoovers, J. David Cooney, and Paul M. Toporowski. Synthesis and Characterization of Narrow Molecular Weight

Distribution Fractions of Poly (aryl ether ether ketone). Macromolecules 1990, 23, 1611-1618.

(48) Pang, J.; Shen, K.; Feng, S.; Zhang, H.; Jiang, Z. Polymer Electrolyte Membranes based on Poly(arylene ether)s with Flexible

Disulfophenyl Pendant. J Power Sources 2014, 263, 59-65.

(49) Pang, J.; Shen, K.; Ren, D.; Feng, S.; Jiang, Z. Polyelectrolyte based on Tetra-Sulfonated Poly(arylene ether)s for Direct Methanol

Fuel Cell. J Power Sources 2013, 226, 179-185.

(50) Pang, J.; Zhang, H.; Li, X.; Ren, D.; Jiang, Z. Low Water Swelling and High Proton Conducting Sulfonated Poly(arylene ether )

with Pendant Sulfoalkyl Groups for Proton Exchange Membranes. Macromolecular Rapid Communications 2007, 28, 2332-2338.

(51) Tian, S.; Meng, Y.; Hay, A. S. Membranes from Poly(aryl ether)-Based Ionomers Containing Randomly Distributed Nanoclusters

of 6 or 12 Sulfonic Acid Groups. Macromolecules 2009, 42, 1153-1160.

26


Page 27 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(52) Tian, S.; Meng, Y.; Hay, A. S. Membranes from Poly(aryl ether)-Based Ionomers Containing Multiblock Segments of Randomly

Distributed Nanoclusters of 18 Sulfonic Acid Groups. Journal of Polymer Science Part A: Polymer Chemistry 2009, 47, 4762-4773.

(53) Dawson, P. C. and Blundell, D. J. X-Ray Data for Poly(aryl ether ketones). Polymer 1980, 21, 577-578.

(54) Inceoglu, S.; Rojas, A. A.; Devaux, D.; Chen, X. C.; Stone, G. M.; Balsara, N. P. Morphology-Conductivity Relationship of

Single-Ion-Conducting Block Copolymer Electrolytes for Lithium Batteries. Acs Macro Lett 2014, 3, 510-514. (55) Shin, D. W.; Guiver, M. D.; Lee, Y. M. Hydrocarbon-Based Polymer Electrolyte Membranes: Importance of Morphology on Ion Transport and Membrane Stability. Chem Rev 2017, 117, 4759-4805. (56) Kreuer, K. D. On the Development of Proton Conducting Polymer Membranes for Hydrogen and Methanol Fuel Cells. Journal of

Membrane Science 2001, 185, 29-39.

(57) Lafitte, B.; Jannasch, P. Proton-Conducting Aromatic Polymers Carrying Hypersulfonated Side Chains for Fuel Cell Applications.

Advanced Functional Materials 2007, 17, 2823-2834.

(58) G. Gebel, O. D. Neutron and X-Ray Scattering: Suitable Tools for Studying Ionomer Membranes. Fuel Cells 2004, 2, 261-276.

(59) Jutemar, E. P.; Jannasch, P. Influence of the Polymer Backbone Structure on the Properties of Aromatic Ionomers with Pendant

Sulfobenzoyl Side Chains for Use as Proton-Exchange Membranes. ACS applied materials & interfaces 2010, 2, 3718-25

27



TOC graphic

28


Page 28 of 28

High Dimensional Stability and Alcohol Resistance Aromatic Poly(aryl

Recommend Documents