Polyethylene-Based Block Copolymers for Anion Exchange
Membranes
Yifan Li
Ye Liu
Alice
M. Savage
Frederick L. Beyer
Soenke Seifert
Andrew M. Herring
Daniel M. Knauss
10.1021/acs.macromol.5b01457.s001
https://acs.figshare.com/articles/journal_contribution/Polyethylene_Based_Block_Copolymers_for_Anion_Exchange_Membranes/2129278
Block copolymer membranes with a
semicrystalline polyethylene component
were prepared by anionic polymerization and postpolymerization functionalization
reactions. Polybutadiene-<i>b</i>-poly(4-methylstyrene)
(PB-<i>b</i>-P4MS) precursors with four different block
compositions and 92–95% 1,4-content in the polybutadiene block
were produced by living anionic polymerization in a nonpolar solvent.
The polybutadiene block was subsequently hydrogenated to prepare a
polyethylene block, and the hydrogenated block copolymers were then
brominated at the arylmethyl group of the P4MS block. Subsequent quaternization
reaction with trimethylamine led to the anion exchange membranes.
The degree of crystallinity in the polyethylene block was determined
by differential scanning calorimetry to be approximately 24–27%.
The postpolymerization modification reactions were examined by <sup>1</sup>H NMR and IR spectroscopy. The amount of quaternary ammonium
groups was quantified by ion exchange capacity (IEC) measurements.
Membranes with IEC’s ranging from 1.17 to 1.92 mmol/g were
prepared. The IEC was varied by changing the relative amount of P4MS
in the precursor block copolymer, and water uptake and ionic conductivity
were found to increase with increasing IEC. Small-angle X-ray scattering
(SAXS) experiments and transmission electron microscopy (TEM) showed
phase-separated, bicontinuous structures at all compositions. Materials
with higher IEC show improved ionic conductivity as well as lower
activation energy of ion conduction compared to less functionalized
membranes. The hydroxide conductivity of the block copolymer membrane
with an IEC of 1.92 mmol/g reached 73 mS/cm at 60 °C in water.
Tensile measurements indicated excellent mechanical properties of
the semicrystalline membranes for potential use as alkaline fuel cell
membrane materials.
2015-09-22 00:00:00
P 4MS block
polyethylene block
Subsequent quaternization reaction
postpolymerization modification reactions
SAXS
1 H NMR
Anion Exchange MembranesBlock copolymer membranes
ion exchange capacity
postpolymerization functionalization reactions
quaternary ammonium groups
fuel cell membrane materials
TEM
precursor block copolymer
IEC
transmission electron microscopy
block copolymer membrane
anion exchange membranes
semicrystalline polyethylene component
IR
polybutadiene block
hydrogenated block copolymers