JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

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Radiation-Induced Graft Polymerization of Styrene into
a Poly(ether ether ketone) Film for Polymer Electrolyte
Membranes
S. Hasegawa a) , K. Sato b) , T. Narita b) , Y. Suzuki a) , S. Takahashi a) ,
N. Morishita a) and Y. Maekawa a)
a) Environment and Industrial Materials Research Division, QuBS, JAEA,
b) Graduate School of Engineering, Saitama Institute of Technology
Radiation-induced graft polymerization is a unique
technique for direct grafting of a new functional polymer
phase (grafts) into polymer films (substrate), in which
functional polymers keep their characteristics such as
thermal stability, mechanical strength, electronic properties,
and crystallinity 1) . There have been many attempts for
basic researches to reveal graft polymerization mechanisms
and for making new grafts into various polymer substrates
including chemical transformation of grafts 2) to be applied
for battery separators, absorber resins, and polymer
3)
electrolyte membranes (PEMs) . Recently, we reported
that the grafting of styrene into PEEK film pre-irradiated
with 30 kGy was accelerated by using 1-propanol as a
grafting solvent at 80 °C to obtain styrene-grafted PEEK
4)
with a grafting degree of more than 60% . Thus, we
investigated the changes in morphology of PEEK films such
as crystallinity and phase separation caused by grafting of
styrene and subsequent sulfonation using differential
scanning calorimetry (DSC), thermogravimetry (TGA),
X-rays diffraction analysis (XRD), and electron spin
resonance spectroscopy (ESR).
Judging from the similar endothermic heat of melting of
the original and styrene-grafted PEEK (grafted PEEK) films,
there was no change in crystallinity during the graft
polymerization of styrene up to a grafting degree of 51%.
Furthermore, lower glass transition temperature (Tg) than the
original PEEK film in the DSC profile (Fig. 1) and no extra
halo originating from amorphous polystyrene grafts being
found in XRD strongly indicate that the grafting of
crystalline region. These results indicate that styrene to
have crystalline PEEK films proceeds in the amorphous
heat flow, endothermic (mW)
10
5
0
-5
-10
(c) Sulfonated PEEK
(b) Grafted PEEK
(a) Crystalline PEEK
-15
50 150 250 350
Temperature (ºC)
Fig. 1 DSC profiles of original PEEK (a), grafted PEEK
with 51% GD (b), and PEEK-based PEM (sulfonated
form of film b) with 93% SD (c).
JAEA-Review 2010-065
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region of PEEK without destroying the crystalline region.
This is because polystyrene grafts have similar
hydrocarbon structures to a base PEEK polymer, so that
these grafts are compatible to the amorphous phase of the
PEEK films.
The ESR spectra of the original PEEK film and the film
irradiated with 200 kGy in vacuo at room temperature were
measured at room temperature (Fig. 2). The ESR signal in
the irradiated film was observed at a g-value of 2.0074 with
density of 5.23 × 10 16 /g, which was 12 times larger than that
of the original film.
325 330 335 340 345 350
Magnetic Field(mT)
Fig. 2 ESR spectra of the original PEEK film (a) and the
film irradiated with 200 kGy in vacuo at room
temperature (b) were measured at room temperature.
The grafted PEEK films can be converted to PEEK-based
PEM by subsequent sulfonation of the polystyrene grafts.
By changing the sulfonation time in the sulfonation of
polystyrene grafts at 0 ◦ C in 0.05 M of chlorosulfonic acid in
dichloroethane, the ion exchange capacity of the PEM can be
controlled to a relatively low value. However, PEM with
conductivity of more than 0.01 S/cm exhibited higher water
content, above 100%. The degree of crystallinity of the
grafted PEEK was found to drastically decrease with the
sulfonation reaction of the grafts. The DSC and XRD
observations indicated that the sulfonation reaction
proceeded not only at the graft layers but also at the
crystalline and amorphous phases of PEEK.
References
1) A. Chapiro, Radiation Chemistry of Polymeric System,
Interscience Publishers, John Wiley & Sons, New York,
1962, Chap. XII.
2) M. M. Nasef et al., Prog. Polym. Sci. 29 (2004) 499.
3) K. Saito et al., Radiat. Chem.: Present Status and Future
Trends, Elsevier, 439(2001) 671.
4) S. Hasegawa et al., Radiat. Phys. Chem. 77 (2008) 617.
(a)
(b)