Ladder-type aromatic block copolymers containing sulfonated triphenylphosphine oxide moieties as proton conductive membranes

Accepted Manuscript Ladder-type aromatic block copolymers containing sulfonated triphenylphosphine oxide moieties as proton conductive membranes Yaojian Zhang, Junpei Miyake, Ryo Akiyama, Kenji Miyatake PII:

S0032-3861(15)30239-1

DOI:

10.1016/j.polymer.2015.09.034

Reference:

JPOL 18120

To appear in:

Polymer

Received Date: 31 July 2015 Revised Date:

7 September 2015

Accepted Date: 15 September 2015

Please cite this article as: Zhang Y, Miyake J, Akiyama R, Miyatake K, Ladder-type aromatic block copolymers containing sulfonated triphenylphosphine oxide moieties as proton conductive membranes, Polymer (2015), doi: 10.1016/j.polymer.2015.09.034. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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for the Table of Contents

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LadderLadder-type aromatic block copolymers containing sulfonated

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triphenylphosphine oxide moieties as proton conductive membranes

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Yaojian Zhang, Junpei Miyake, Ryo Akiyama, Kenji Miyatake*

*Corresponding author. Tel.: +81 552208707; fax: +81 552208707. E-mail address: [email protected] (K. Miyatake).

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Polymer communication

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LadderLadder-type aromatic block copolymers containing sulfonated

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triphenylphosphine oxide moieties as proton conductive membranes

a

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Yaojian Zhang a, Junpei Miyake b, Ryo Akiyama c, Kenji Miyatake b, c, *

Interdisciplinary Graduate School of Medicine and Engineering, University

of Yamanashi, 4 Takeda, Kofu, Yamanashi 400-8510, Japan Clean Energy Research Center, University of Yamanashi, 4 Takeda, Kofu,

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b

Yamanashi 400-8510, Japan

Fuel Cell Nanomaterials Center, University of Yamanashi, 6-43 Miyamae,

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c

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Kofu, Yamanashi 400-0021, Japan

* Corresponding author. Tel.: +81 552208707; fax: +81 552208707. E-mail address: [email protected] (K. Miyatake).

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ABSTRACT The synthesis and characterization of ladder-type aromatic block containing

sulfonated

triphenylphosphine

oxide

moieties

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copolymers

(LadP LadPLadP-SPE) SPE are reported. Through aromatic nucleophilic substitution

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polycondensation and Pd-catalyzed intrapolymer Heck reaction, the target copolymers LadPLadP-SPE with high molecular weight (Mn = 47 – 50 kDa, Mw =

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289 – 579 kDa) and different ion exchange capacity (IEC) values (1.04, 1.84 and 2.22 meq g-1, by titration) were prepared. By solution casting method, all the copolymers gave transparent and bendable membranes. The membrane

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with IEC = 2.22 meq g-1 exhibited high proton conductivity in wide range of relative humidity (RH) at 80 °C (ca. 1.6 mS cm-1 at 20% RH and 351.2 mS

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cm-1 at 95% RH). Moreover, the stiff ladder structure strengthened the

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molecular chain which contributed to the membrane with high IEC value and water uptake to have desirable mechanical stability up to 90% RH at 80 °C.

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1. Introduction Polymer electrolyte membranes (PEMs) have gained extensive

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attention for full cell applications. While perfluorinated ionomers such as Nafion (du Pont) have been most used as state-of-the-art PEM, fluorine-free

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aromatic PEMs have been developed extensively as alternative PEMs in terms of better environmental compatibility and lower cost [1-7]. It has been

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demonstrated that multiblock copolymers containing sulfonated hydrophilic segments and unsulfonated hydrophobic segments show improved properties (e.g., higher proton conductivity than that of the random copolymer due

to

the

well-developed

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equivalent)

hydrophilic-hydrophobic

phase-separated morphology with interconnected ionic channels [8-17].

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Recently, our group has developed multiblock copolymers containing

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sulfonated triphenylphosphine oxide moiety in the hydrophilic segments (SPEKP SPEKP, SPEKP Scheme 1b) [18]. The SPEKP membrane exhibited high proton conductivity (216 mS cm-1) despite its low ion exchange capacity (IEC) value (1.09 meq g-1) at 80 °C and 95% relative humidity (RH), which is 1.3 times higher than that of Nafion. However, similar to most aromatic-type PEMs, the SPEKP membrane suffered from mechanical instability under wet

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conditions. In addition, higher IEC membrane for higher proton conductivity was not available due to dissolution in water.

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More recently, we have achieved a novel polymeric structural conversion (i.e., intrapolymer Heck reaction) to form ladder structure on

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diphenyl ether moieties in aromatic PEMs [19]. The advantage of the polymer reaction is that higher density of the ladder structure can be

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achieved than using the monomeric ladder compounds [20]. The dense ladder structure provided the PEM with improved mechanical stability under wet conditions, probably due to the enhancement of interpolymer interactions

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derived from the rigid and planar dibenzofuran (ladder) moieties and/or reduction in polarity caused by the aromatic nature of dibenzofuran moieties.

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The results prompted us to further examine whether the ladderization of the

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sulfonated triphenylphosphine oxide moieties might enable the increase in IEC, resulting in the improvement of proton conductivity without compromising the mechanical stability. In this paper, we report synthesis and properties of ladder-type aromatic multiblock copolymers containing sulfonated triphenylphosphine oxide moiety as hydrophilic segments and oligo(arylene ether) as hydrophobic segments (LadP LadPLadP-SPE, SPE Scheme 1a).

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2. Experimental section

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available in the Supporting Information.

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Detailed experimental on the synthesis and characterization are

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3. Results and discussion

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Scheme 1. (a) Synthesis of title block copolymers (LadP LadPSPE and (b) LadP-SPE) chemical structure of reference polymers (SPEKP SPEKP and SPESK). SPESK

Scheme 1a shows the overall synthetic route for the title block copolymers (LadP LadPSPEs (i) Synthesis of hydrophobic (unsulfonated) LadP-SPEs); telechelic oligomers 1 and hydrophilic (sulfonated) telechelic oligomers 3, 6

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separately, (ii) block copolymerization of the oligomers 1 and 3 to give precursor

multiblock

copolymers

(Br BrP BrP-SPEs), SPEs

and

(iii) Pd-catalyzed

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intrapolymer Heck reaction of BrPBrP-SPEs to give the title block copolymers (LadP LadPLadP-SPEs). SPEs First of all, oligomers 1 were prepared by the typical aromatic

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nucleophilic substitution polycondensation of 4,4'-biphenol (BP) and bis(4-fluorophenyl)sulfone (FPS) with K2CO3 as base and DMAc as solvent.

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The chain lengths (X) and terminal groups (OH) were controlled by the feed comonomer ratios. The 1H and

19F

NMR spectra (Fig. S1 in Supporting

information) supported the formation of the targeted oligomers 1 with

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controlled X and OH-terminals (Table S1 in Supporting information). The chain lengths obtained by the 1H NMR spectra were similar to those by the

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feed comonomer ratios, while those by GPC were larger probably because the

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oligomers 1 are composed of rigid molecular structure and eluted fast in our GPC system.

The preparation of oligomers 2 were carried out in a similar manner

as described for the oligomers 1. It should be noted that the high reactivity of FPS with Br-substituents allowed milder reaction conditions (lower reaction temperature such as 110 °C) for the preparation of the oligomers 2 as well as

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for the following the preparation of multiblock copolymers BrPBrP-SPEs compared to those of the oligomers 1 [20]. The chemical structure of the 19F

and

31P

NMR spectra, in which all

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oligomers 2 was characterized by 1H,

signals were well-assigned (Fig. S4 in Supporting information). For example, 31P

NMR spectra of the oligomers 2, a singlet peak was observed at

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in the

24.8 ppm which was different from that of the BHPPO monomer (26.1 ppm),

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suggesting the complete consumption of the BHPPO monomer. Although the

Y values obtained by 1H NMR spectra were in fair agreement with those calculated from the feed comonomer ratios, the ones obtained by GPC

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analyses were much lower (Table S1 in Supporting information). This result is consistent with our previous result, in which phosphine oxide-containing

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oligomers had some interactions with our GPC columns resulting in the

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underestimation of Mn (i.e., lower Y values) [18]. Oligomers 3 were prepared by sulfonation reaction of the oligomers 2

with 30% oleum at room temperature for 24 h. The chemical structure of the oligomers 3 were characterized by 1H,

19F

and

31P

NMR spectra (Fig. S5 in

Supporting information). The 19F NMR chemical shift of the oligomer 3 (-99.2 ppm) was similar to that of the oligomer 2 (-98.9 ppm), suggesting that no

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sulfonation reaction occurred at the terminal phenylene groups. This result may come from the steric hindrance and/or the low electron density of the

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terminal phenylene rings containing electron-withdrawing sulfone, bromine, and fluorine groups.

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Block copolymerization of the oligomers 1 and 3 was carried out in the similar manner as described for the oligomers. Slightly higher reaction

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temperature (130 °C) was necessary to obtain high molecular weight BrPBrP-SPEs. SPEs The chemical structure was characterized by NMR spectra (Fig. S6 and S8 in Supporting information). The progress of the block

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copolymerization was confirmed by the absence of the terminal-related signals of the starting oligomers 1 (proton a) and 3 (fluorine) in the NMR

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spectra of BrPBrP-SPEs SPEs. GPC analyses supported the formation of high

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molecular weight BrPBrP-SPEs SPEs (Mw = 161 - 507 kDa) (Table S2 in Supporting information).

The

IEC

values

of

BrPBrP-SPEs

calculated

from

the

hydrophilic/hydrophobic integral ratios in the 1H NMR spectra were similar to or only slightly smaller than expected. The ladder-type block copolymers, LadPLadP-SPEs SPEs, were synthesized via Pd-catalyzed intrapolymer Heck reaction [19] of BrPBrP-SPEs. SPEs Among several

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organic solvents often used for this type of reaction, NMP was found to be the appropriate solvent in terms of the reactivity and the solubility. The

31P

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chemical structure of the obtained copolymers was characterized by 1H and NMR spectra (Fig. S7 and S8 in Supporting information). Comparison of

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the 1H NMR spectra between BrPBrP-SPEs and LadP LadP-SPEs revealed that the ladderization reaction caused changes in the protons of the hydrophilic

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segments, but not in the hydrophobic segments. For example, the absence of proton 14 and the shift to a lower magnetic field of protons 5, 6, 8, 9, 13 suggested the complete ladderization reaction in the hydrophilic blocks of

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BrPBrP-SPEs. SPEs In particular, the newly appeared 1H NMR signals at around 8.5 9.5 ppm (protons 6 and 9) were a solid evidence for the formation of the

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targeted ladder (dibenzofuran rings) structure in the hydrophilic segments.

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The IEC values of LadPLadP-SPEs calculated from the hydrophilic/hydrophobic integral ratios in the 1H NMR spectra were similar to or slightly lower than expected (Table 1). In the 31P NMR spectra of LadPLadP-SPEs, SPEs the signals (26 - 27 ppm) were observed at a lower magnetic field than those of BrPBrP-SPEs (25 26 ppm), suggesting the structural changes in the hydrophilic blocks. Multiple

31P

NMR signals indicated the existence of

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31P

species having

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various structural and electronic situations, e.g.,

31P

in the hydrophilic

blocks and at the hydrophilic/hydrophobic connecting parts. The molecular

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weight of the LadPLadP-SPEs SPEs should become lower than that of the corresponding precursor BrPBrP-SPEs SPEs due to the loss of an HBr for each

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dibenzofuran moiety. The GPC analyses, however, did not show such relationship between LadPLadP-SPEs SPEs and BrPBrP-SPEs SPEs in their molecular weights

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(Tables 1 and S2 in Supporting information). The contradictory effects of intrapolymer Heck reaction, i.e., the loss in the mass but the increase in the rigidity of polymers, as well as the chain length differences in each samples

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might be responsible for the results. The obtained LadPLadP-SPEs SPEs retained high molecular weight (Mw = 289 - 579 kDa) and gave self-standing membranes by

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solution casting. The obtained membranes showed comparable IEC values to

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those calculated from the 1H NMR spectra. LadPLadP-SPEs with high IEC values (1.84 and 2.22 meq g-1) were insoluble in water indicating that the ladder structure introduced in the hydrophilic block improved the water stability of the membranes compared to our previous block copolymers (SPEKP SPEKP, SPEKP Scheme 1b).

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Table 1

Mna

Mwa

IECb

IECc

IECd

(kDa)

(kDa)

(meq g-1)

(meq g-1)

(meq g-1)

X10Y5

50

579

1.34

X5Y5

48

353

X5Y10

47

289

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Molecular weight and IEC of LadPLadP-SPEs SPEs.

a

Determined by GPC;

b

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Composition

1.00

1.04

2.03

1.96

1.84

2.43

2.07

2.22

Calculated from the feed chemical composition;

c

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Obtained by 1H NMR spectra; d Obtained by titration.

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Water uptake and proton conductivity of the membranes were

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measured at 80 °C and plotted as a function of relative humidity (RH) in Fig. 1. For comparison, the data of SPEKP (the same hydrophobic blocks and sulfonated triphenylphosphine oxide but no ladder moieties) and SPESK [21] (the same hydrophobic blocks but no sulfonated triphenylphosphine oxide and ladder moieties) are included (Scheme 1b). The water uptake approximately followed the order of the IEC values. However, the water

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uptake of LadPLadP-SPESPE X5Y10 showed similar values with those of X5Y5 despite the former’s higher IEC, probably due to the well-developed

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phase-separated morphology of LadPLadP-SPESPE X5Y10 (Fig. S9 in Supporting information). As expected, LadPLadP-SPE membranes showed higher proton

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conductivity with increasing IEC and RH. The highest proton conductivity of LadPLadP-SPESPE X5Y10 (IEC = 2.22 meq g-1) reached 351.2 mS cm-1 at 95% RH,

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which was ca. 2.1 times higher than that of Nafion (170 mS cm-1). The proton conductivity of LadPLadP-SPESPE X5Y10 decreased with decreasing humidity (1.6 mS cm-1 at 20% RH). The proton conductivity of SPESK (1.69 meq/g) was

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similar to those of LadPLadP-SPEs (1.84 and 2.22 meq/g) in spite of its former’s lower IEC value, probably due to the higher ionic concentration of SPESK

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(local IEC = 5.34 meq/g) than that of LadPLadP-SPE (local IEC = 3.94 meq/g).

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Compared with SPEKPSPEKP X30Y4, LadPLadP-SPESPE X5Y5 and X5Y10 with higher IECs showed much higher proton conductivity at wide range of humidity. It should be noted that SPEKP with IEC values higher than ca. 1.2 meq g-1 could not be obtained because of the high water solubility. In this work, we have

succeeded

in

the

synthesis

of

sulfonated

triphenylphosphine

oxide-based aromatic ionomer membranes having much higher IEC values

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(up to 2.22 meq g-1) by introducing the ladder structure in the hydrophilic

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blocks.

a

LadP-SPE-X10Y5 (1.04 meq/g) LadP-SPE-X5Y5 (1.84 meq/g) LadP-SPE-X5Y10 (2.22 meq/g) SPEKP-X30Y4 (0.92 meq/g) SPESK-X15Y8 (1.69 meq/g)

40

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60

20 0 b

10-2 10-3

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10

-1

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Proton conductivity (S cm -1)

Water uptake (%)

80

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10-4

0

20 40 60 80 Relative humidity (%)

100

Fig. 1. (a) Water uptake and (b) proton conductivity of LadPLadP-SPE, SPE SPEKP and SPESK membranes (IEC values obtained by titration in parentheses) at 80 °C as a function of RH.

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The storage modulus (E’), loss modulus (E’’), and tan δ were measured at 80 °C and plotted as a function of RH in Fig. 2. It is considered

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that the sulfonic acid groups in the hydrophilic segments absorb water with increasing humidity, resulting in plasticization of the membranes [22]. For

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example, SPEKP and SPESK showed clear peaks in E’’ and tan δ, possibly a glass transition, at ca. 55% RH. Although the LadPLadP-SPEs and SPEKP shared

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the similar chemical structure except for the ladder moiety, LadPLadP-SPEs showed more stable mechanical properties (no peaks in E’’ and tan δ) under the humidified conditions despite much higher water uptake of LadPLadP-SPEs

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than that of SPEKP. SPEKP The ladder moieties (dibenzofuran rings) in the hydrophilic blocks would strengthen the molecular chains and limit the

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rotation of phenyl ether moieties in hydrophilic segments. The high

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mechanical stability of the LadPLadP-SPE membrane was further confirmed by the tensile test at 80 °C and 60% RH (Fig. S10 in Supporting information). LadPLadP-SPESPE X10Y5 membrane showed high initial Young's modulus (0.45 GPa), high yield stress (32 MPa) and strain (100%). Fenton’s test (80 °C for 1 h) of the LadPLadP-SPESPE X10Y5 membrane showed moderate oxidative stability (residual weight = 67%), suggesting that

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the sulfonated triphenylphosphine oxide moieties in the hydrophilic block

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might contribute to the improvement of the oxidative stability.

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1010

LadP-SPE-X10Y5 (1.04 meq/g) LadP-SPE-X5Y5 (1.84 meq/g) LadP-SPE-X5Y10 (2.22 meq/g) SPEKP-X30Y4 (0.92 meq/g) SPESK-X15Y8 (1.69 meq/g)

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E' (Pa)

a

109

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108

108

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E'' (Pa)

b

107

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106

tan δ

c

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10-1

10-2

0

20 40 60 80 Relative humidity (%)

Fig. Fig. 2. DMA analyses of LadPLadP-SPE, SPE SPEKP and SPESK membranes; (a) E’ (storage modulus), (b) E’’ (loss modulus) and (c) tan δ at 80 °C as a function of RH. 17

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4. Conclusions In summary, we have developed a novel series of aromatic ionomers

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containing sulfonated triphenylphosphine oxide and ladder moieties in the hydrophilic blocks. The obtained LadPLadP-SPEs had high molecular weight and

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good solubility in polar organic solvents, resulting in the formation of self-standing membranes by solution casting. Comparison with the reference

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polymer, sharing the similar chemical structure except for ladder structure, revealed that the combination of sulfonated triphenylphosphine oxide and ladder moiety was effective in improving the proton conducting and

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Acknowledgments

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mechanical properties under the heated and humidified conditions.

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This work was partly supported by the New Energy and Industrial Technology Development Organization (NEDO) through the HiPer-FC Project, and the Ministry of Education, Culture, Sports, Science and Technology (MEXT) Japan through a Grant-in-Aid for Scientific Research (26289254).

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Appendix Appendix A. Supplementary data

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Supplementary data related to this article can be found at http://

Keywords

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Block copolymers, Conducting polymers, Membranes

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[9] Hoshi T, Bae B, Watanabe M, Miyatake K. Bull Chem Soc Jpn 2012;85:389.

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[10] Akiyama R, Hirayama D, Saito M, Miyake J, Watanabe M, Miyatake K.

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[11] Miyake J, Sakai M, Sakamoto M, Watanabe M, Miyatake K. J Membr

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[18] Miyake J, Watanabe M, Miyatake K. ACS Appl Mater Interfaces 2013;5:5903.

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[19] Miyake J, Watanabe M, Miyatake K. RSC Adv 2014;4:21049.

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[22] Miyake J, Mochizuki T, Miyatake K. ACS Macro Lett 2015;4:750.

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ACCEPTED MANUSCRIPT Highlights (1) Ladder-type ionomers with sulfonated triphenylphosphine oxide moiety were prepared.

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(2) The ionomers had high molecular weights, leading to tough and flexible membranes.

(3) The ionomer membranes showed high proton conductivity with good

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mechanical stability.

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Supporting Information for

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LadderLadder-type aromatic block copolymers containing sulfonated

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triphenylphosphine oxide moieties as proton conductive membranes

a

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Yaojian Zhang a, Junpei Miyake b, Ryo Akiyama c, Kenji Miyatake b, c, *

Interdisciplinary Graduate School of Medicine and Engineering, University

of Yamanashi, 4 Takeda, Kofu, Yamanashi 400-8510, Japan Clean Energy Research Center, University of Yamanashi, 4 Takeda, Kofu,

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b

Yamanashi 400-8510, Japan

Fuel Cell Nanomaterials Center, University of Yamanashi, 6-43 Miyamae,

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c

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Kofu, Yamanashi 400-0021, Japan

* Corresponding author. Tel.: +81 552208707; fax: +81 552208707. E-mail address: [email protected] (K. Miyatake).

S1

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Materials

N,N-Dimethylacetamide

(DMAc),

dimethyl

sulfoxide

(DMSO),

toluene

(dehydrated), 30% oleum, sulfuric acid (96%), nitric acid (60%), hydrochloric acid (35%), potassium carbonate (K2CO3), calcium carbonate (CaCO3), lead(II) acetate (Pb(OAc)2) used

as

received.

Bis(4-fluorophenyl)sulfone

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trihydrate, and sodium chloride (NaCl) were purchased from Kanto Chemical Co. and (FPS),

4,4'-biphenol

(BP),

N-bromosuccinimide (NBS), cesium carbonate (Cs2CO3), sodium diphenylphosphino benzene-3-sulfonate (sPPh3), and palladium(II) acetate (Pd(OAc)2) were obtained from TCI Inc. and used as received. Methanol was purchased from Wako and used as received.

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Methyl sulfoxide-d6 (DMSO-d6, for NMR, with 0.03% tetramethylsilane (TMS), 99.9 atom% D) was purchased from Acros Organics and used as received. Spectra/Por 6 dialysis tubing (1,000 Da MWCO) was purchased from Spectrum Laboratories, Inc. and

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used as received. 4,4'-Sulfonylbis(2-bromo-1-fluorobenzene) (BrFPS) was prepared by the bromination of FPS using NBS according to the literature method.[S1] Measurements 1H

(500 MHz),

19F

(471 MHz), and

31P

(202 MHz) NMR spectra were recorded

on a JEOL JNM-ECA 500 at 80 °C using DMSO-d6 as solvent and TMS as an internal reference. Apparent molecular weights were measured at 50 °C with gel permeation chromatography (GPC) with a Jasco 805 UV detector. N,N-Dimethylformide (DMF)

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containing 0.01 M LiBr was used as eluent. A Shodex K-805L column was used for sulfonated compounds and a Shodex SB-803HQ column was used for unsulfonated compounds, respectively. Molecular weights were calibrated with standard polystyrene samples. Ion exchange capacity (IEC) of the membranes was measured at room

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temperature via back-titration. A small piece of dry membrane (ca. 20 mg) in acid form was immersed into a large excess of ca. 2 M NaCl solution for 24 h. The H+ in the

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solution released from the membrane was titrated with 0.01 M NaOH aqueous solution. For transmission electron microscopy (TEM) observations, the membranes were stained with lead ions by ion exchange of sulfonic acid groups in ca. 0.5 M Pb(OAc)2 aqueous solution, thoroughly washed with deionized water, and dried under vaccum at 80 ° C for 24 h. The samples were sectioned into 50 nm slices with a Leica microtome Ultracut UCT, collected by copper grids, and then examined with a Hitachi H-9500 TEM. Proton conductivity (σ) and water uptake were evaluated at 80 °C by a solid electrolyte analyzer system (MSBAD-V-FC, Bel Japan Co.) equipped with a temperature and humidity controllable chamber. The weight of the membranes at a given humidity was measured by magnetic suspension balance. The water uptake was calculated by the following equation. Water uptake = ((weight of hydrated membrane) – (weight of dry S2

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membrane) / weight of dry membrane ×100). The membranes were dried at 80 °C for 3 h under vacuum to obtain the weight of dry membrane and exposed to the set humidity for at least 2 h to obtain the weight of hydrated membranes. In-plane proton conductivity (σ) of the membranes was measured by ac impedance spectroscopy

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(Solartron 1255B and 1287) simultaneously in the same chamber. Ion conducting resistances (R) were determined from the impedance plot measured over the frequency range from 1 to 105 Hz. The proton conductivity was calculated according to the following equation: σ = l / (A × R), where l is the distance between the two inner wires (l = 1 cm) and A is the conducting area, respectively. Humidity dependence of the storage

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moduli (E’), loss moduli (E’’), and tan δ of the membranes was evaluated via dynamic mechanical analyses (DMA) with an ITK DVA-225 dynamic viscoelastic analyzer. Each sample was tested over a humility range from 0 to 90% relative humidity (RH) at 80 °C

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(10 Hz). Tensile strength was investigated by a Shimadzu AGS-J 500N universal test machine attached to a Toshin Kogyo Bethel-3A temperature and humidity controllable chamber. The measurement was performed with samples cut into dumbbell shape (DIN-53504-S3, 35 mm × 6 mm (total) and 12 mm × 2 mm (test area)) at 80 °C and 60% RH at a tensile rate of 10 mm min-1. Oxidative stability was tested in Fenton’s reagent (2ppm FeSO4 in 3% H2O2). The stability was determined by recording the change of

AC C

EP

TE D

weight after soaked in Fenton’s reagent for 1 h at 80 °C.

S3

ACCEPTED MANUSCRIPT

Synthesis of the hydrophobic oligomer (1 1) Oligomers 1 were prepared via a typical aromatic nucleophilic substitution reaction. BP, FPS, K2CO3, DMAc, and toluene were added into a 100 mL three-neck flask equipped with a magnetic stirring bar, a Dean-Stark trap, a condenser, and a

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nitrogen inlet/outlet. After heated at 150 °C for 5 h, the mixture was cooled to room temperature and diluted with DMAc. The mixture was poured into a large excess of 1 M HCl to precipitate a powder. The crude was washed with 1 M HCl, methanol twice, and deionized water twice. Drying in vacuum oven at 80 °C for 12 h gave oligomers 1.

For X5, BP (1.1173 g, 6.0 mmol), FPS (1.2713 g, 5.0 mmol), K2CO3 (2.0730 g, 15.0 mmol),

SC

DMAc (12.0 mL), and toluene (0.7 mL) were used. 92% yield. Mn = 5.2 kDa, Mw = 11.1 kDa (determined by GPC).

For X10, BP (1.0242 g, 5.5 mmol), FPS (1.2713 g, 5.0 mmol), K2CO3 (2.0730 g, 15.0

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mmol), DMAc (12.0 mL), and toluene (0.7 mL) were used. 90% yield. Mn = 6.5 kDa, Mw = 16.1 kDa (determined by GPC).

1(X10)

TE D

a)

12

14 16 18 Retention time/min

AC C

10

1

H

2 c b

1(X 5)

a

1( X10) 8.5

20

3,4, d 1

1( X5)

EP

Absorbance at 270nm, a.u.

b)

8

7.5 ppm

7

6.5

c) 19

F

1( X5) 1( X10) -90

-100 ppm

-110

Figure S1. a) GPC profiles, b) 1H and c) 19F NMR spectra of oligomers 1 in DMSO-d6 at 80 °C. S4

ACCEPTED MANUSCRIPT

Synthesis of the hydrophilic oligomer (3 3) [BHPPO BHPPO monomer] Bis(4-hydroxyphenyl)phenylphosphine oxide (BHPPO BHPPO) BHPPO was prepared as shown in Scheme S1. The first step is the synthesis of bis(4-methoxyphenyl)phenylphosphine

RI PT

oxide (BMPPO BMPPO). BMPPO A 300 mL three-neck round-bottomed flask equipped with condenser, magnetic stirrer bar, and nitrogen purge was charged with magnesium (4.86 g, 200 mmol) and THF (65 mL). To this mixture, 4-bromoanisole (25.1 mL, 200 mmol) was added dropwise over 10 min and then the whole mixture was heated to 95 °C for 4 h, stirred at room temperature for about 24 h and then cooled to 0 °C. Subsequently,

SC

phenylphosphonic dichloride (13.9 mL, 100 mmol) was added dropwise over 30 min. The mixture was allowed to warm to room temperature and diluted with additional THF (30 mL) to decrease the viscosity. After stirring for 44 h, the reaction mixture was poured

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into 0.1 M sulfuric acid (300 mL). The aqueous solution was extracted with ethyl acetate and the combined organic layers were washed with saturated aqueous sodium hydrogen carbonate and deionized water, and concentrated in vacuo. The resulting light orange viscous oil was used in the next reaction without further purification. The structure was confirmed by 1H and 31P NMR for the crude sample (Figure S2). The second step is demethylation of BMPPO. BMPPO A 500 mL one-neck round-bottomed flask equipped with condenser, magnetic stirrer bar, and nitrogen

TE D

purge was charged with crude BMPPO (ca. 100 mmol), glacial acetic acid (100 mL) and 48% hydrobromic acid (100 mL), and the mixture was stirred at 125 °C. After 75 h, the 1H

NMR spectrum of the crude product indicated that monomethoxy intermediate still

remained in the reaction mixture. Therefore, additional 48% hydrobromic acid (50 mL)

EP

was added to the reaction mixture, and the reaction was continued. After further 20 h, the complete reaction was confirmed. The reaction mixture was cooled to room

AC C

temperature and poured into deionized water (600 mL), and the resulting precipitate was collected by filtration. The pure BHPPO was obtained by treatment with activated carbon and reprecipitation from ethanol/water in 81% yield (25.1 g). The obtained product was characterized by 1H, 13C and 31P NMR spectra, respectively (Figure S3).

S5

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ACCEPTED MANUSCRIPT

AC C

EP

TE D

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SC

Scheme S1. Synthesis of BHPPO monomer.

Figure S2. a) 1H and b) 31P NMR spectra of BMPPO in CDCl3.

S6

EP

TE D

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SC

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ACCEPTED MANUSCRIPT

AC C

Figure S3. a) 1H, b) 13C and c) 31P NMR spectra of BHPPO in DMSO-d6.

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ACCEPTED MANUSCRIPT

[Hydrophilic oligomer precursor (2 2)] A general procedure is as follows. BHPPO, BrFPS, K2CO3, DMAc, and toluene were added into a 100 mL three-neck flask equipped with a magnetic stirring bar, a Dean-Stark trap, a condenser, and a nitrogen inlet/outlet. After heated at 110 °C for 4 h,

RI PT

the mixture was cooled to room temperature and diluted with DMAc. The resulting mixture was poured into a large excess of 1 M HCl to precipitate a white powder. The crude powder was washed with 1 M HCl solution, methanol and deionized water twice. Drying in vacuum oven at 80 °C for 12 h gave oligomers 2.

For Y5, BHPPO (0.7757 g, 2.5 mmol), BrFPS (1.2362 g, 3.0 mmol), K2CO3 (1.2093 g, 8.75

SC

mmol), DMAc (5.0 mL), and toluene (0.2 mL) were used. 83% yield. Mn = 2.4 kDa, Mw = 5.4 kDa (determined by GPC).

For Y10, BHPPO (0.8462 g, 2.73 mmol), BrFPS (1.2362 g, 3.0 mmol), K2CO3 (1.3198 g,

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9.6 mmol), DMAc (5.0 mL), and toluene (0.2 mL) were used. 86% yield. Mn = 3.6 kDa,

Absorbance at 270nm, a.u.

Mw = 10.2 kDa (determined by GPC).

b)

a)

10

H

2(Y5)

EP

2( Y10)

TE D

1

15

20

6

AC C

11

2(Y10) 9

8.5

8 ppm

7.5

7

d)

c)

31

F

P

2(Y5)

2(Y5)

2(Y10)

2(Y10)

-90

7,8

c

2(Y5)

Retention time/min

19

b,9, 10,12

a,5

-100 ppm

Figure S4. a) GPC profiles, b) 1H, c)

40

-110

30

20

10

ppm

19F

and d)

DMSO-d6 at 80 °C. S8

31P

NMR spectra of oligomers 2 in

ACCEPTED MANUSCRIPT

[Hydrophilic oligomer (3 3)] A general procedure is as follows. Oligomer 2 and 30% oleum were added into a 100 mL three-neck flask equipped with a magnetic stirring bar. After stirred at room temperature for 24 h, the mixture was poured into a large excess of cold water. The

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solution was basified with NaOH aqueous solution, dialyzed, evaporated, and dried in a vacuum oven at 80 °C for 12 h to obtain oligomers 3.

For Y5, Oligomer 2 (1.61 g) and 30% oleum (8.5 mL) were used. 74% yield. Mn = 8.1 kDa,

Mw = 11.7 kDa (determined by GPC).

For Y10, Oligomer 2 (1.7100 g) and 30% oleum (9.0 mL) were used. 65% yield. Mn = 14.9

b)

a)

1

3(Y10)

3(Y5)

H

5,6

TE D

7,f

c)

12

3(Y10) 9

8.5

8

7.5

7

6.5

ppm

P

3(Y5) 3(Y10)

3(Y10)

-100 ppm

13 14

e

3(Y5)

31

3(Y5)

-90

8,11 9,10, 12,g

d)

AC C

F

8 10 Retention time/min

EP

6

19

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Absorbance at 270nm, a.u.

SC

kDa, Mw = 30.8 kDa (determined by GPC).

40

-110

Figure S5. a) GPC profiles, b) 1H, c)

30

20

10

ppm

19F

and d)

DMSO-d6 at 80 °C.

S9

31P

NMR spectra of oligomers 3 in

ACCEPTED MANUSCRIPT

Synthesis of the multiblock copolymer (BrP BrPBrP-SPE) SPE A general procedure is as follows. Oligomer 1, oligomer 3, K2CO3, CaCO3, DMSO (or DMSO/NMP), and toluene were added into a 100 mL three-neck flask equipped with a magnetic stirring bar, a Dean-Stark trap, a condenser, and a nitrogen

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inlet/outlet. After heated at 130 °C for 24 h, the mixture was cooled to room temperature and diluted with DMSO. The resulting mixture was poured into a large excess of 1 M HCl to precipitate a solid product. The crude product was washed with 1 M HCl, 20 wt% NaCl aqueous solution, and deionized water twice. Drying in vacuum oven at 80 °C for 12 h gave BrPBrP-SPEs. SPEs

SC

For X10Y5, Oligomer 1 (0.4391 g, 0.100 mmol, X10), oligomer 3 (0.5849 g, 0.100 mmol,

Y5), K2CO3 (0.0346 g, 0.250 mmol), CaCO3 (0.1001 g, 1.00 mmol), DMSO (4.0 mL), and toluene (0.5 mL) were used. 71% yield. Mn = 41 kDa, Mw = 161 kDa (determined by

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GPC).

For X5Y5, Oligomer 1 (0.1618 g, 0.0512 mmol, X5), oligomer 3 (0.3300 g, 0.0512 mmol,

Y5), K2CO3 (0.0177 g, 0.1281 mmol), CaCO3 (0.0513 g, 0.5124 mmol), DMSO (2.0 mL), and toluene (0.4 mL) were used. 74% yield. Mn = 48 kDa, Mw = 506 kDa (determined by GPC).

For X5Y10, Oligomer 1 (0.1105 g, 0.035 mmol, X5), oligomer 3 (0.3559 g, 0.035 mmol,

Y10), K2CO3 (0.0121 g, 0.0875 mmol), CaCO3 (0.0350 g, 0.35 mmol), DMSO (1.2 mL),

AC C

EP

(determined by GPC).

TE D

NMP (0.8 mL), and toluene (0.4 mL) were used. 73% yield. Mn = 106 kDa, Mw = 496 kDa

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b) Absorbance at 270nm, a.u.

1

BrP-SPE- X 5Y 10 BrP-SPE- X 5Y 5 BrP-SPE- X 10Y5

a)

H

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ACCEPTED MANUSCRIPT

3,4,14

1,8, 11 2

5,6

9,10, 12

13

6

8 10 Retention time (min)

c)

8.5

12

8

7.5 ppm

7

6.5

d) 31

F

TE D

19

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SC

7

-100 ppm

EP

-90

40

-110

Figure S6. a) GPC profiles, b) 1H, c)

19F

P

30

20

10

ppm

and d)

AC C

DMSO-d6 at 80 °C.

S11

31P

NMR spectra of BrPBrP-SPEs in

ACCEPTED MANUSCRIPT

Synthesis of the title ladder-type ionomer (LadP LadPLadP-SPE) SPE A general procedure is as follows. BrP-SPE and DMAc (or NMP) were added into a 100 mL three-neck flask equipped with a magnetic stirring bar, a condenser, and a nitrogen inlet/outlet. After heated at 80 °C for 1 h to give a homogeneous solution, the

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mixture was cooled to room temperature. Then, sPPh3 and Cs2CO3 were added and the mixture was stirred for 1 h. Pd(OAc)2-containing DMAc (or NMP) solution was added and the mixture was heated at 100 °C for 24 h. After cooled to room temperature, the mixture was filtered and the filtrate was dried at 70 °C to obtain a solid product. The crude product was washed with 1 M nitric acid 4 times and deionized water. Drying in a

SC

vacuum oven at 80 °C for 12 h gave a yellow solid.

For X10Y5, Polymer (0.5115 g, 0.0300 mmol), DMAc (15 mL), sPPh3 (0.0142 g, 0.0390 mmol), Cs2CO3 (0.3812 g, 1.1700 mmol), and Pd(OAc)2 (0.0044 g, 0.0195 mmol) were

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used. 19% yield. Mn = 50 kDa, Mw = 579 kDa (determined by GPC).

For X5Y5. Polymer (0.3636 g, 0.0344 mmol), NMP (49 mL), sPPh3 (0.0714 g, 0.1960 mmol), Cs2CO3 (0.4790 g, 1.4700 mmol), and Pd(OAc)2 (0.0220 g, 0.0980 mmol) were used. 71% yield. Mn = 48 kDa, Mw = 353 kDa (determined by GPC). For X5Y10, Polymer (0.3000 g, 0.0210 mmol), NMP (45 mL), sPPh3 (0.0667 g, 0.1828 mmol), Cs2CO3 (0.4467 g, 1.3710 mmol), and Pd(OAc)2 (0.0205 g, 0.0914 mmol) were

AC C

EP

TE D

used. 76% yield. Mn = 47 kDa, Mw = 289 kDa (determined by GPC).

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ACCEPTED MANUSCRIPT

1

H

1,11, 13

6

5

10 Retention time (min)

c) P

TE D

31

9.5

15

EP

40

9

9

5,7,8

3,4

2

10,12

SC

LadP-SPE-X 5Y10 LadP-SPE-X 5Y5 LadP-SPE-X 10Y5

a)

8.5

8 ppm

7.5

7

6.5

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Absorbance at 270nm, a.u.

b)

30

20

10

ppm

AC C

Figure S7. a) GPC profiles, b) 1H and c) 31P NMR spectra of LadPLadP-SPEs in DMSO-d6 at 80 °C.

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H

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1

SC

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ACCEPTED MANUSCRIPT

Oligomer 1 (X=5) Oligomer 3 (Y=5) BrP-SPE-X5Y5 LadP-SPE-X5Y 5 (Sodium form)

3,4,d

1

2

TE D

c

5,6

8,11

b

9,10, 12,g

7,f

a

13 14

AC C

EP

e

9.5

5,6

1,8, 11 2 7

1,11, 13 6

9

5,7,8

9

8.5

8 ppm

3,4,14 9,10, 12

13

3,4 2 10,12

7.5

7

6.5

Figure S8. 1H NMR spectra of oligomer 1 (X = 5), oligomer 3 (Y = 5), BrPBrP-SPESPE X5Y5 and LadPLadP-SPESPE X5Y5 in DMSO-d6 at 80 °C. S14

ACCEPTED MANUSCRIPT

Membrane preparation The polymers were dissolved in DMSO and cast on a flat and smooth glass plate. Drying the solvent at 70 °C for 48 h, at 80 °C in a vacuum oven for 6 h gave transparent and bendable membranes. The membranes were immersed in 1 M H2SO4,

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washed with deionized water several times, and dried at room temperature.

Table S1. Chain lengths of oligomers 1 and 2

Oligomers 2

Xa)

Xb)

Xc)

Ya)

Yb)

Yc)

5

7.4

12.5

5

6.1

2.9

10

13.9

15.8

10

SC

Oligomers 1

9.5

4.7

from the feed comonomer ratios.

c)Calculated

from Mn (Determined by GPC analyses, calibrated with polystyrene

standards).

b)Determined

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a)Calculated

by

1H

NMR spectra.

Table S2. Molecular weight and IEC of BrPBrP-SPEs [kDa] Mna) [kDa]

X10Y5 X5Y5 X5Y10

IECc) [meq g-1]

41

161

1.62

1.42

48

507

1.91

1.80

106

496

2.22

b)Calculated

from the feed composition.

2.12 c)Obtained

by 1H NMR

AC C

spectra.

by GPC.

IECb) [meq g-1]

EP

a)Determined

kDa] Mwa) [kDa]

TE D

Composition

Figure S9. TEM images of LadPLadP-SPE membranes in lead ion form (titration IEC values in the parentheses).

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ACCEPTED MANUSCRIPT

LadP-SPE-X10Y5 (1.04 meq/g)

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40 30 20

SC

Stress / MPa

50

10

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0 0

50 Strain / %

100

Reference

TE D

Figure S10. Stress vs strain curve of LadPLadP-SPESPE-X10Y5 at 80 °C and 60% RH.

AC C

9810.

EP

[S1] N. Li, D. W. Shin, D. S. Hwang, Y. M. Lee, M. D. Guiver, Macromolecules 2010, 2010 43,

S16