Photon Factory Activity Report 2017 #35 (2018)

BL-6A/2017G123

Effect of solvents of perfluorosulfonic acid dispersions on polymer nanostructure of
their recasting membranes

Chan-Ho Song and Jin-Soo Park*
Department of Green Chemical Engineering, College of Engineering, Sangmyung University, C-411,
Main Building, 31 Sangmyungdae-gil, Dongnam-gu, Cheonan, Chungman Province, 31066,
Republic of Korea

2 Experiment
SAXS was used to investigate micro-phase separationof cation conductive ionomer dispersed in varioussolvents. The SAXS measurements were performed atintervals during the drying stage of the film forming
process at BL-6A in Photon Factory.
The X-raywavelength was 0.15 nm, the sample-to-detector distancewas 2 m and the scattering intensity was measured using
Pilatus 3. Nafion D521 dispersions were prepared bydispersing Nafion D521 in different solvent media such as
N-methyl-2-pyrrolidone (NMP). Membrane recasting
was carried out to completely evaporate the solvent at80︒C for 24 hours under vacuum.
3 Results and Discussion
Figure 1 shows the SAXS spectra of cation-conductive
recast membranes dispersed in various solvents at room
temperature. We have confirmed the relationship of ion
transport behavior, membrane fundamental characteristic,

and change of bulk-phase morphology of radiationgrafted membranes as represented in Figure 2. The Nafion
D521 membrane prepared by Nafion D521 dispersion
which is based on alcohol solvents show that its iondomain distance was measured as 4.83 nm(wet) and 3.88nm(dry). It results in an increase in distance between theionic domains, compared to the NMP used membrane to
6.52 nm(wet) and 4.27 nm(dry). Ion-domain distance wascalculated by Bragg’s Law (d = 2 π/q). These results showthat ion-domain distance is highly dependent on solventsused in dispersions.
1Intensity (a.u.)

1 Introduction
In the solvent-swollen Nafion membrane, the resulting
cluster structure is formed of water pools with the ionicgroups located at the polymer-solvent interface, which isembedded in the perfluorinated sulfonic acid polymermatrix. These solvent-swollen clusters are closely related
to the ionic conductivity. The modification of the proton
exchange membranes (PEMs) with solvent effects has
been recently reported. It is important to note that theionic clusters are formed in the nano-size of theaggregates. Small-angle X-ray (SAXS) spectroscopy is
one of the most efficient techniques to study thenanostructure of the phase-separated polymer materials
with the unique advantages of a nondestructive way andeasy sample preparation. [1] In this report, SAXS
techniques are used to investigate the effect of solvents ofdispersions on the nanostructure of perfluorinatedsulfonic acid polymer based membranes, which is closelyrelated to its proton conductivity. In addition, SAXS
spectra are quantitatively analyzed to investigate thenanostructure of the phase separated clusters (oraggregates) with solvents, which are very important fordeveloping high-performing and high-durable PEMs forfuel cells.

Nafion D521 (Wet)Nafion D521 (Dry)
NMP (Wet)
NMP (Dry)

0.1

0.01

1E-3

0.1

q (A-1)

Fig. 1: SAXS profile of the wet and dry Nafion D521
membranes and the wet and dry recast Nafion membrane
in NMP.
Table. 1: Summary of q maximum values and domain
distance of the samples
Samplename

Nafion D521(Wet)Nafion D521(Dry)

NMP(Wet)NMP(Dry)q max (A-1)

0.13020.16184

0.09644

0.1471

Domaindistance(nm)

4.83

3.88

6.52

4.27

Photon Factory Activity Report 2017 #35 (2018)

Fig. 2: A log-log representation of a typical SAXS
spectrum from a swollen Nafion 117 film.
Acknowledgement
This work was supported by part by the New andRenewable Energy of the Korea Institute of Energy
Technology Evaluation and Planning (KETEP) granted
financial resource form the Ministry of Trade, Industryand Energy, Republic of Korea (No. 20153010031920).
References[1] C.-S. Tsao et al., Polymer 46, 8430-8437 (2005)* energy@smu.ac.kr