number of papers and citations on ”fuel cell membranes” · introduction and background...
TRANSCRIPT
1
Ionomers and membrane chemistry
Patric Jannasch Department of Chemistry Polymer & Materials ChemistryDepartment of Chemistry, Polymer & Materials Chemistry
Lund University, Sweden
The membrane-electrode assembly (MEA) in PEMFC,Utö conference center, 21-22 June 2010.
Number of papers and citations on ”fuel cell membranes”
Web of Science® – with Conference Proceedings Citation Report Topic = (fuel cell* and membrane*)Timespan = All Years. Databases = SCI-EXPANDED, SSCI, A&HCI, CPCI-S, CPCI-SSH.
2
Outline
Scope of the presentation:“to give selected examples of approaches to
prepare proton-conducting ionomer membranesbased on aromatic polymers”
Introduction and background
Sulfonation of polymers
Macromolecular designs for nanostructured ionomers
H hl h f d ff h d
based on aromatic polymers
Highlight of different approaches to proton conducting aromatic ionomers
A glimpse at the efforts on ionomers in Lund
Polymer and monomer synthesis: molecular design, synthesis and characterisation of polymers
Molecular structures: ionomers, copolymers (block, graft, comb), ladder polymers, networks…
Functional materials: polymer electrolyte membranes, polymers with intrinsic microporosity…
Polymers and membranes -research activities and focus in Lund
Application areas: energy-related electrochemical devices (fuel cells, batteries, EC windows), membrane separations (reverse osmosis, gas separations)
Properties: thermal, mobility (diffusion, etc.), mechanical, optical, self-assembly, solubility…
p y y p y p y
3
The structure of the perfluorinated NafionTM polymer (ionomer)
side chain
main-chain
The membrane of today - NafionTM
CF2
CF2
CF2
CF
O CF2
CF O CF2
SO3
H
x y
CF2
sulfonic acid
side-chain
Membrane morphology at increasing water contents
2CF
3
2 32
AFM image ofhydrated Nafion
domain size: 5-10 nm
The challenge from industry:increasing the operating temperature and humidity range
- 40 0 90 130 oC
NafionTMNafionTM
expansion of operating temperature
Commercial membranes
AutomotiveYou want tostart from here...
40 0 90 130 C
StationaryCo-generation ofpower and heat…
Great need for new membrane materials based on tailor-made ionomers or other alternative systems
...and get out of there
For excellent overviews, see Adv. Polym. Sci., Vol. 215 and 216, 2008.
4
Strategy for a successful membrane design
50 nmmolecular structure
membrane morphology transport properties
water sorption stability
ExcellentPEMFC
performance !
High performance engineering polymers Generally characterised by excellent thermal, chemical, and mechanical stabilityWide range of commercially available monomers and polymers
O O
Alternative sulfonated aromatic polymer membranes
O S
O
On O O C
O
n
C O S
OCH3
CH3 O
O n
Polyethersulfone, PES Polyetheretherketone, PEEK
Polysulfone, PSU
S n
Poly(phenylene sulfide), PPSn
Poly(p-phenylene), PPP
Poly(phenylene oxide), PPO
O
CH3
CH3
n
5
Sulfonated aromatic polymers for new membrane materials
H2SO4 or
ClSO3H
Preparation by:
Direct (post) sulfonation:
Important molecular parameters include:- Degree of sulfonation (IEC : mmol H+ / g dry membrane)
** *
condensation
Metallation-sulfonation:
Direct copolymerisation using sulfonated monomers:
activation reaction
- Polymer structure, architecture and molecular weight (Tg and viscoelastic properties)- Location and distribution of the sulfonic acid units (blocks, side chains)
X Y Z n
SO3HR
Mechanism of sulfonation and desulfonation (simplified)
Sulfonation of aromatics with SO3:
SO3HSO3-
+
SO3-
+
H
SO3+
-
H++
Sulfonation of aromatics with sulfonic cation:
SO3H-
+ +
H
SO3+ H+++ SO3H
H
SO3H HIn dilute acid solutions
Desulfonation of aromatics:
3
+ H O2 H S O4+ 2
In dilute acid solutionsor water
Rule of thumb: easy to sulfonate = easy to desulfonate
O
SO3H
C
SO3H
O
Activated fordesulfonation:
Deactivated fordesulfonation:
6
O S
O
OnO
Polyphenylsulfone (Radel)
(Tg=210 oC)
Molecular chain characteristics of poly(arylene ether sulfone)s
Arylene ether parts:- unpolar- flexible - electron-rich
Arylene sulfone parts:- polar- rigid- electron-poor
O(Tg 210 C)
Electrophilic Nucleophilic
Inherently difficultto chemically modify
chemically stable polymers
Harsh, yet specific methodsProspects formodification:
aromaticsubstitution
reactions
paromatic
substitutionreactions
Meier-Haack et al. Adv. Polym. Sci., 2008.Guiver et al., ACS Symp. Ser., 2000.
are desired
Direct sulfonation of poly(arylene ether sulfone)s
Electrophilic substitution reactions, i.e., electron-rich arylene rings strongly favoured SO3H
Sulfonatingagent
C O S
OCH3
CH3
OnO C O S
OCH3
CH3
OnO
p y g g y
Sulfonating agents include:SO3 / H2SO4 (Rose, US Pat. 4,273,903 [1981])SO3 in CH2Cl2 (Coplan et al., US Pat.4,413,106 [1983])SO3 complexes with triethylphosphate (Buck, US Pat. 430,513 [1982]) Chlorosulfonic acid, ClSO3H (Bell et al., US Pat. 5,401,410 [1995])Trimethylsilyl chlorosulfonate, (CH3)3SiSO3Cl (Chao et al., US Pat. 4,625,000 [1982])
The methods of direct sulfonation differ in their: Ease and cost of applicationHomogeneity of the reaction medium Levels of reactivity (degradation) and hazard
Iojoiu et al., Fuel Cells, 2005
7
Metallation-sulfonation of poly(arylene ether sulfone)s
OO S
O
On
butyllithium, -70 deg. C
Sulfonic acid units ortho-to-sulfone in the PSU main-chain: less activated for desulfonation than the sulfonic acid units obtained after electrophilic sulfonation
OO S
O
On
Li
OO S
O
On
SO2Li
SO2
y , g
Kerres et al., J. Membr. Sci., 2001.
O
H2O2
OO S
O
On
SO3H
Morphological features of hydrated membranes
NafionTM Sulfonated PEEKK
CF2
CF2
CF2
CF
O CF2
CF
CF3
O CF2
SO3H
x y
CF2
O O C
O
SO H3
SO HSO H
C
O
n
- wide channels - separated - less branched- good connectivity- small separationbetween sulfonicacid units
- pKa ~ -6
- narrow channels- less separated- highly branched- dead-end channels- large separationbetween sulfonicacid units
- pKa ~ -1
- excessive watert k b
Schematic representations suggested by K.D. Kreuer (J. Membr. Sci., 2001)
uptake above acriticaltemperature
1 nm
8
Concentration of ionic sites in the membrane by separation into highly sulfonated hydrophilic segments and non-sulfonated hydrophobic segments
Concentrating the acid groups for morphological controland enhanced performance
Statistical ionomer
Segmented ionomer
“Structural and Morphological Features of Acid-Bearing Polymers for PEM Fuel Cells”,Holdcroft et al., Adv. Polym. Sci., 2008
Ionic aggregation
Ionic aggregationand self-assembly
(ideally)
Macromolecular designs for nanostructured membranes
Statistical copolymer
Graft copolymer
Alternating multiblock copolymer
Random multiblock copolymerSide-chain modified copolymer
Microblock copolymer
Triblock copolymer Starblock copolymer
9
Tailoring side-chain sulfonated polymers
flexible side chains…
tiff
sulfonation
Aromatic polymer
…stiffer…
…longer…
…di-sulfonated...
Isolated acid groups on side-chains to- increase amphiphilicity- increase local acid unit mobility
…tri-sulfonated...Minimized local inter-acid distances to- concentrate acid units- further increase the amphiphilicity
Side-chain sulfonated polysulfones
O O S
O
On
S
O
O
O
SO3H
HO3S
SO3H
O
S
O
O
O
OS
O
O
O
O
S
O
OO
SO3H
S
O
OSO
3H
S
O
O
O
O
SO3H
ds
sbtspb
HO3S
SO3H
HO3S6snb
7snb
dsnb
Jutemar et al., J. Membrane Sci., 2010.
10
Polysulfones with sulfoaryloxybenzoyl side chains
1. butyl lithiumO SO2
OC
Cl
F
O
2.
precursor
O O SO n2
F
O
O
SO3H
O
O
SO3H
HO3S
O
O
HO3S
SO H
O
O
HO S
Synthesised derivatives:
80-90 °CDMSO
K2CO3
O SO2
O
HO-Aryl—SO K3 x
Puchner et al., Macromol. Rapid Commun., 2005. Lafitte et al., Adv. Funct. Mater., 2007.
SO3H HO
3S
SO3H
Highly activated and reactive fluorine Low temperature necessary in the SNAr reactions Complete displacement of fluorine Close to 100% yield reached with pre-made potassium salt
O
Aryl—SO K3 x
SAXS profiles of dry membranes
The q-values of the ”ionomer peaks”relate to characteristic separationlengths between the ionic domains.
Braggs spacing, d = 2/qd= 71 Å
624544
Proton conductivity of fully immersed membraneswith similar IEC valuesd= 44 Å
4140
d= 44 Å3737
Jutemar et al., J. Membrane Sci., 2010.
(d= 22 Å)( 27 )
d= 25 Å24
d= 35 Å
11
F F F F
Li
F F
O
SO3LiO
S
O
OO
n-BuLi
THF, -70 oC THF, -70 oC
Sulfonated aromatic polymers by direct polycondensation
2,6-difluoro-2’-sulfobenzophenone
O O
O
SO3K
n
OH
OH
F F
O
SO3Li
DFSBP
+1. 160 oC, 3 h2. 175 oC, 21 h
K2CO3
DMAc / toluene
PAE
(DFSBP)
S S
S
O
SO3K
mF F
O
SO3Li
SH
S
SH
+1. 110 oC, 3 h2. 175 oC, 15 h
K2CO3
DMAc / cyclohexane
PAS
Jutemar et al., Macromol. Rapid Commun., in press 2010
Sulfonated aromatic polymers by direct polycondensation
PAS membrane
PAS
Various aromatic polysulfones, polysulfides, polyketones, and polyethersare currently under investigation.
PAE
12
1.
Amphoteric compounds capable of acting as both proton source and solvent in the membrane at high temperatures
Immobilised alternative proton conducting units
H+
H+
H+
2.
3.
No need for water All-polymeric
monomeric oligomeric
H+
H+
Conduction by structure diffusion Requirements for the immobilisation
depend on the nature of the amphotericcompound
H+polymeric
Tg = -30 °C
benzimidazole aggregation
Intrinsically conducting polymers tethered with benzimidazole
N
NH
N
NH
-10
-8
-6
-4
-2
log
(/
Sc
m-1
)
g
Tg = 57 °C
160 oC
30 oC
60 oC
Low molecular mobility and degree ofautoprotolysis limit the conductivity
1000/T (K-1
)
2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6-14
-12
Tg = 24 °C
Persson et al., Macromolecules, 2005. Persson, Chem. Mater., 2007.
13
Phosphonated polymers and membranes
Represent a viable alternative to sulfonated PEMFC membranes
phosphoric acid methylphosphonic acid
Some possibilities and challenges:
Intrinsic conductivity Lower water uptake Enhanced stability Anhydride formation More challenging
POH
OH
O
POH
O
O
POH
OH
O
POH
OH
O
POH
OH
OP OH
O
OHPOH
O
OH
POH OH
OHP
OH
O
OH
+
OO P
OH
O
Overall aim of the research:
Develop and investigate various synthetic strategies to promoteconductivity at high temperatures and low humidification
B. Lafitte, P. Jannasch, Advances in Fuel Cells, 2007.M. Schuster, K.D. Kreuer, et al., Solid State Ionics, 2008.
PO
OH
OH
OH
H
Phosphonated polymers and membranes
0
H PO
200 150 100 75125175 50oC
-4
-3
-2
-1
log
/ S
cm
-1)
n = 2
n = 6
O Si
CH3
x
H3PO
3H3PO4
n = 4
PO
OH
OH
P
OH
OH
O
P
OH
OH
O
-7
-6
-5
1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4
1000/T / K-1
CH2 n
x
P OHOH
O
Nominally dry conductivityKreuer et al., Fuel Cells, 2005.
14
Synthetic approaches to new phosphonatedpolymer membrane materials at Lund
Commercially availablearomatic polysulfones :
S
O
O
O* O *n
O S
O
O O
Arylphosphonic acid(J. Polym. Sci., Polym. Chem., 2005)
Poly(vinylphosphonic acid)(Macromolecules, 2008)
S
O
O O
P
OOH OH
S
O
O
O O
C O S
O
O
O O
S
O
O
O O
C
C
O
F
P
F
O
OHOH
O
*
P
m
OOH
OH
Difluoromethylphosphonic acid(J. Polym. Sci., Polym. Chem., 2007)
Alkylphosphonic acid(J. Mater. Chem., 2008) AlkylBis(phosphonic acid)
(J. Mater. Chem., 2008)
Block copolymers : Poly(styrene-b-vinylphosphonic acid)(Macromolecules, 2009)
POHO
OH
O
P
P
O
O
OHOH
OH
OH
OH
**
P
x y
O OH
OH
Why polysulfones grafted with poly(vinylphosphonic acid)?
Immobilisation of proton source and solvent Formation of very high local concentrations of interacting phosphonic acid Phase separation for membrane stability under humidified conditions High thermal and chemical stability
Poly(vinyl phosphonic acid) grafts:- Acidic and hydrophilic- Hydrogen bonding- ”Flexible” chain
Polysulfone main chain:- Hydrophobic- Rigid chain
15
Controlled grafting of poly(vinylphosphonic acid) from polysulfonesthrough anionic polymerisations
m
OOn
S
O
O
O On
S
O
O
lithiation butyl lithium
P
O
OEt
OEt
P
m
OO
OH
nS
O
O
hydrolysis aq. HCl, reflux
Designation:PVPA IEC DS
OOn
Li
S
O
O
activation
P
O
OEt
OEtgrafting
P
O
OH
OHgPVPA_IEC_DS
Achievements: Well-defined samples prepared with DS: 1-4 side chains/10 PSU units,
IEC: 0.4 – 6.0 mmol/g MW of PVPA side chains: 500 - 6000 g/mol Structure confirmed by FTIR, TGA and 13C, 31P, 1H NMR Quantitative hydrolysis of ester
J. Parvole, P. Jannasch, Macromolecules 2008.
Copolymers and membranes
More than 30 different copolymers prepared
All the polymers nicely soluble in organic solvents
Selected copolymer and membrane data
Flexible and robust membranes cast from DMAc,NMP and DMSO solutions.
T5% (°C) 5% weight loss under
PVPA content (wt%)
IEC (mmol
/g)Sample
Area (%)
H2O Uptake (%)20 °C,
98% RH
Mn(PVPA)
(kg/mol)
Mn(copol.) (kg/mol)
DS(1H NMR)
297474.3gPVPA_4.3_2
279575.2gPVPA_5.2_1
286484.4gPVPA_4.4_1
320322.9gPVPA_2.9_1
air(wt%)/g)
7430
15546
10434
4419
( )98% RH
2.0
5.8
4.0
2.0
(kg/mol)
52
62
52
40
(kg/mol)
1
( )
1
2
1
16
AFM phase images of copolymer membranes shownanophase separated morphologies
200 nm200 nm Tg (PSU)
Tg (PVPA)
Tg (PSU)
Tg (PVPA)
200 nm
gPVPA_3.0_433 wt% PVPAM = 500 g/mol DS = 0.4IEC = 3.0 meq/g
0.2
W/g
gPVPA_4.3_2
gPVPA_4.4_1
gPVPA_2.9_1
gPVPA_3.0_4
0.2
W/g
gPVPA_4.3_2
gPVPA_4.4_1
gPVPA_2.9_1
gPVPA_3.0_4
Images recorded under ambient air atmosphere by Dr. Matti Elomaaat the University of Helsinki
gPVPA_5.3_155 wt% PVPAM = 5400 g/molDS = 0.1IEC = 5.3 meq/g
50 100 150 200 250 300
Temperature (oC)
gPVPA_5.3_1
PSU
50 100 150 200 250 300
Temperature (oC)
gPVPA_5.3_1
PSU
Proton conductivity under humidified conditions
Effects of water meltin
Immersed 100% RH
-0.50-20 oC020406080100120
1 0
20 oC507090120
Immersed 100% RH
-0.50-20 oC020406080100120
1 0
20 oC507090120-0.50
-20 oC020406080100120
1 0
20 oC507090120
Effects of water meltingat sub-zero temperatures
Dilution effects of gPVPA_5.3_1 at hightemperatures
Long side chains seembeneficial for theconductivity at given IEC:
id t ti
a. b.
-2.5
-2.0
-1.5
-1.0
gPVPA_5.3_1
log
(/
S c
m-1
)
-2.0
-1.8
-1.6
-1.4
-1.2
-1.0
gPVPA 5.3 1
log
(/
S c
m-1
)
a. b.
-2.5
-2.0
-1.5
-1.0
gPVPA_5.3_1
log
(/
S c
m-1
)
-2.0
-1.8
-1.6
-1.4
-1.2
-1.0
gPVPA 5.3 1
log
(/
S c
m-1
)
a. b.
-2.5
-2.0
-1.5
-1.0
gPVPA_5.3_1
log
(/
S c
m-1
)
-2.0
-1.8
-1.6
-1.4
-1.2
-1.0
gPVPA 5.3 1
log
(/
S c
m-1
)
- acid concentration- percolation
-3.5
-3.0
2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
gPVPA_4.4_1gPVPA_2.9_1gPVPA_4.3_2gPVPA-3.0_4Nafion 115 -2.4
-2.2
2.4 2.6 2.8 3.0 3.2 3.4 3.6
gPVPA_5.3_1gPVPA_4.4_1gPVPA_2.9_1gPVPA_4.3_2gPVPA_3.0_4Nafion 115
1000/T (K-1) 1000/T (K-1)
-3.5
-3.0
2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
gPVPA_4.4_1gPVPA_2.9_1gPVPA_4.3_2gPVPA-3.0_4Nafion 115 -2.4
-2.2
2.4 2.6 2.8 3.0 3.2 3.4 3.6
gPVPA_5.3_1gPVPA_4.4_1gPVPA_2.9_1gPVPA_4.3_2gPVPA_3.0_4Nafion 115
1000/T (K-1) 1000/T (K-1)
-3.5
-3.0
2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
gPVPA_4.4_1gPVPA_2.9_1gPVPA_4.3_2gPVPA-3.0_4Nafion 115 -2.4
-2.2
2.4 2.6 2.8 3.0 3.2 3.4 3.6
gPVPA_5.3_1gPVPA_4.4_1gPVPA_2.9_1gPVPA_4.3_2gPVPA_3.0_4Nafion 115
1000/T (K-1) 1000/T (K-1)
17
c.
-2.0-20
oC020406080100120
c.
-2.0-20
oC020406080100120
Nominally dryProton conductivity under nominally dry conditions
C d ti it t l d d t
-8.0
-6.0
-4.0
log
(/
S c
m-1
)
-8.0
-6.0
-4.0
log
(/
S c
m-1
)
Conductivity strongly dependenton phosphonic acid concentration
Condensation at high temperatures
Membrane gPVPA_5.3_1 reached5 mS/cm at 130 oC
-12
-10
2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
gPVPA_5.3_1gPVPA4.4_1gPVPA_2.9_1gPVPA_4.3_2Nafion 115
1000/T (K-1)
-12
-10
2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
gPVPA_5.3_1gPVPA4.4_1gPVPA_2.9_1gPVPA_4.3_2Nafion 115
1000/T (K-1)
Doping phosphonated membranes with a perfluorosulfonic acid polymer
Challenge: Reduce excessive water uptakeunder high humidifications leading to dilution ff t d h i l ti
240
260
280
Blend9-2 3%)
gPVPA_5.3_1Blend9-2 3+ 2.3% N11
240
260
280
Blend9-2 3%)
gPVPA_5.3_1Blend9-2 3+ 2.3% N11
Immersed
effects and poor mechanical properties.
Strategy: Introduce ionic crosslinks by dopingwith a perfluorosulfonic acid polymer (N11).
Formation of ionic complexes100
120
140
160
180
200
220Blend9 2.3Blend9-5.0
Wa
ter
up
take
(%
Blend9 2.3Blend9-5.0
2.3% N11+ 5.0% N11
+ 18.0% N11
100
120
140
160
180
200
220Blend9 2.3Blend9-5.0
Wa
ter
up
take
(%
Blend9 2.3Blend9-5.0
2.3% N11+ 5.0% N11
+ 18.0% N11
PO OH
OH
CF2
SO
O
OH
CF2
SO
O
O POH
OHOH
+
Alkylphosphonic acid: (amphoter)
[-SO3] / [-PO3] = 1/25 to 1/250
Perfluoroalkylsulfonic acid: (strong acid)
0 20 40 60 80 100 120 1400 20 40 60 80 100 120 140
Temperature (oC)
0 20 40 60 80 100 120 1400 20 40 60 80 100 120 140
Temperature (oC)
18
Phosphonated membranes doped with perfluorosulfonic acid polymer- Proton conductivity under 100% RH and nominally dry conditions
-1.0
-0.9020
oC507090120
-1.0
-0.9020
oC507090120
100% RH Nominally dry-3.0
-2.0020406080100120 -20 oC020406080100120 C
-3.0
-2.0020406080100120 -20 oC020406080100120 C
-1.5
-1.4
- 1.3
- 1.2
-1.1
gPVPA_5.3_1
Nafion 115
log(
/ S
cm
-1)
+ 2.3% N11+ 5.0% N11
-1.5
-1.4
- 1.3
- 1.2
-1.1
+ 18% N11
-1)
-8.0
-7.0
-6.0
-5.0
-4.0
gPVPA_4.4_1
gPVPA_5.3_1
log
(/ S
cm
-1)
+ 2% N11
+ 5% N11
log
(/ S
cm
-1)
-8.0
-7.0
-6.0
-5.0
-4.0
gPVPA_4.4_1
gPVPA_5.3_1
log
(/ S
cm
-1)
+ 2% N11
+ 5% N11
log
(/ S
cm
-1)
No significant loss of conductivity afterdoping
Positive effect at low T Macrophase separation at 18% N11
-1.62.6 2.8 3.0 3.2 3.4
Nafion 115
1000/T (K-1)
-1.6
-)
Doping of gPVPA_4.4_1 enhancedconductivity. The effect less clear withgPVPA_5.3_1.
Doped membranes more influenced bycondensation reactions than undoped.
-9.02.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
1000/T (K-1
)
+ 5% N11
-1)
Nafion 115-9.0
2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
1000/T (K-1
)
+ 5% N11
-1)
Nafion 115
PO
O
O
1. DEVP
Polystyrene – poly(vinylphosphonic acid) block copolymersby sequential anionic polymerisation
P
OO
O
O
x Li
P
OOH
OH
1. n-BuLi, THF, -75 oC
2.
reflux in fuming HCl
2. MeOH
Hx y Hx y
PSxbPVPAyPSxbPDEVPy
R. Perrin, M. Elomaa, P. Jannasch, Macromolecules, 2009.
19
80
100
80
100
80
100
Thermal stability under nitrogen and air
20
40
60
80
RP045 (ester)
We
igh
t (%
)
20
40
60
80
RP045 (air)
RP047 (air)
RP046 (air)
We
igh
t (%
)
PS PVPA 34 50 b
PS PVPA 68 69 b
PS PVPA 34 71 bPS PVPAb
PS PDEVP 34 50 b20
40
60
80
We
igh
t (%
)
N2 at 10 oC/min. air at 1 oC/min.
0100 200 300 400 500 600
RP045 (acid)
Temperature / oC
00 100 200 300 400 500 600
RPLastPS PVPA 337 139 bPS PVPA 34 50 b
0100 200 300 400 500 600
Temperature / oC Temperature / oCTemperature / oC
Phase separation, condensation and glass transitions
Tg (PS)
scan sequence:
PS PVPA DSC heating thermograms of 337 139 b
0 oCTg (PVPA)
Tg (PVPA)
Tg (PVPA)
0.5
Jg
-1e
xo
0 oC
1500
2000
250
PO
OH
OH
PO
OH
OH
PO
O PO
- H2O+ H
2O
0 50 100 150 200 250 300
Temperature / oC
2500
300 oC
OOH
OOH
20
AFM images of block copolymer morphologies and structures
Spherical block copolymer aggregates forming
linear “necklace-like” chain structures
self-assemblyP
n
OO
OH
m
HP
n
OO
OH
m
H
a b ca b c
PS34bPVPA71 PS68bPVPA69 PS337bPVPA139
Thin block copolymer films withcontinuous PVPA phase domains
400 nm
chain structures
ph
as
e
50 nm 50 nm
50 nm 50 nm 50 nm
50 nm50 nm 50 nm
50 nm 50 nm 50 nm
50 nm
100 nm
PS34bPVPA71
top
og
rap
hy
Images recorded by Dr. Matti Elomaa at the University of Helsinki
10-1
Proton conductivity of PS-PVPA block copolymers
10-3
10-2
/ S
cm
-1
RP045 (air)PS PVPA 34 50 b
RP047 (air)PS PVPA 68 69 b
Conductivity data measured by EIS in a sealed cell after equilibration at 98% RH and 25 ˚C.
10-5
10-4
-20 0 20 40 60 80 100 120 140
Temperature / oC
Nafion 115
RP046 (air)PS PVPA 34 71 b
21
General conclusions
The demands on the PEMFC membrane are very severe and complex, balancingon the edge of what a polymer material can fulfill.
Progress has been made but there is still a need for new innovations and PEMFCmembranes.
Establishing systematic structure-(morphology)-property relationships is crucial inthe design of successful membrane materials.
There is a need to develop synthetic pathways to polymers which will allow for a higher degree of order and morphological control
A wide variety of different approaches for HT membranes are currently being A wide variety of different approaches for HT membranes are currently beingpursued, some based on intrinsic proton conduction.
Properly designed phosphonated membranes may show some advantages incomparison with sulfonated ones.
Dr. Lina Karlsson
Acknowledgements
Co workersin the lab:
Dr. Julien ParvoleDr. Christian PerssonDr. Benoît LafitteM.Sc. Elin Persson
Funding:
in the lab: Dr. Renaud PerrinDr. Francois PaoloniM. Sc. Shogo Takamuku