uctural Studies of Proton-Conducti orous Block Copolymer Membranes Barbara Frisken – SFU Physics Laurant Rubatat - University of Fribourg Ken Shi – NRC IFCI Steven Holdcroft – SFU Chemistry and NRC IFCI Olivier Diat – CEA Grenoble
Mar 19, 2016
Structural Studies of Proton-Conducting Fluorous Block Copolymer Membranes
Barbara Frisken – SFU PhysicsLaurant Rubatat - University of FribourgKen Shi – NRC IFCISteven Holdcroft – SFU Chemistry and NRC IFCIOlivier Diat – CEA Grenoble
Two Series of Diblock CopolymersSeries #1 – Variable Sulfonation
22%
32%
40%
Sulfonation Rate
1B
1A
1C
A BPoly(Vinylidene DiFluoride-co-Hexafluoropropylene)
P(VDF-co-HFP)Sulfonated PolyStyrenesPS
17,900 g/mol 8,000 g/mol
9
12.5
18
2B
2A
2C
25,000 g/mol
Degree of polymerization
A BPoly(Vinylidene DiFluoride-co-Hexafluoropropylene)
P(VDF-co-HFP)Sulfonated PolyStyrenesPS
1000-2000 g/mol
Two Series of Diblock CopolymersSeries #2 – Variable sPS Length
Conductivity and TEM Z. Ken Shi
(2A)(2B)
(1B)
(1A)
(2C)
(1C)Nafion
Conductivity and TEM Z. Ken Shi
(2A)(2B)
(1B)
(1A)
(2C)
(1C)Nafion
1A
1B
1C
2B
2C
SANS Studies
The scattered intensity is proportional to the product of a structure factor S(q) and a form factor P(q):
where P(q) describes the shape of the scattering objects and S(q) describes the spatial distribution of these objects.
I(q) K S(q) P(q)
Neutron Beam
Sample Detector
Peak #1
Peak #2
Series #1 – Two PeaksPeak #1 400 ÅPeak #2 40 Å
Slight shift of the peaks to small angles size increasing with IEC.
Neutron Scattering Spectra – in D2O
Series #2 – Two PeaksPeak #1 400 ÅPeak #2 40 Å
Peak #1 is less sharp less ordered
Peak #2
Peak #1
Series #1 – Partially Sulfonated Series #2 – Variable Length
Contrast Variation
Peak #1
Peak #2
Membrane 2B
Peak #1
Membrane 1C
Peak #2
Series #1 – Partially Sulfonated Series #2 – Variable Length
ContrastVariationSeries #1
Peak #1
Peak #2
Binary System
Structure enhanced or diminished
Ternary System
Match core
Match corona
Membrane 1C
Spectra Divisions
2
2
D O
divH O
I (q) K S(q)I (q)
I (q) 2D O
P (q)
K S(q)
2
2 2
D O
H O H O
P (q)
P (q) P (q)
Membrane 1C
ts
r
Core-shell diskform factorR >> t + 2s
=> Lamellar
Series #1 – Partially sulfonated PVDF PSHydrated sPS
25 Å 165 Å280 Å
180 Å
220 Å
30 Å 170 Å
28 Å 180 Å
Solvent pool
1B
1A
1C
p = 56 %
p = 30 %
p = 25 %
Series #2 – Fully sulfonatedContrast Variation
Peak #1
Peak #2
Membrane 2B
Binary System
Structure enhanced or diminished
Small Length Scale Structure
Modified hard-sphere model Yarusso and Cooper, Macromolecules 1983Spherical ionic aggregates within PS matrix
Hydrated sPS domain
Increasing sulfonation from 22-100% leads to a decrease in the size of the barrier between ionic groups – consistent with improved conductivity.
Series #1
Series #2
40 Å400 Å
Fluorous domains and
Hydrated sPS domains
Solvent poolsin a
PS matrix
f Volume fraction of A block (from data)N Interaction between blocks (not known)
Series #1Series #2
Series #1 shows lamellar structureSeries #2 shows phase separation, but no long range order
Compare to diblock copolymer theory Matsen and Bates, Macromolecules 1996
QIm3m
spheresH cylinders
QIa3d
bi-continuous L lamellar
Conductivity and SANS
(2A)(2B)
(1B)
(1A)
(2C)
(1C)Nafion
Large scale structure is more ordered in Series #1sPS domains are similarLarge scale structure affects the integrity of the membrane, but not the conductivity
1A
2C