Abstract:

Hydrogenated star-shaped poly(styrene-b-butadiene-b-styrene) copolymer(HSBS) was synthesized by catalytic hydrogenation at atmospheric pressure. The product was treated by sequential chloromethylation, quaternization and alkalization to fabricate two kinds of alkaline anion exchange membranes(AEMs) with good comprehensive properties. And they were HSBS4303-OH and HSBS4402-OH(the mass fraction of styrene in the raw materials were 30% and 40%, respectively). The structures and preparation process of AEMs were characterized by Fourier transform infrared(FTIR) spectroscopy. The ionic conductivity, water absorption, swelling, mechanical properties, microphase structure and alkaline resistance of the membranes were systematically studied. The results show that the characteristic melting peak corresponding to the crystalline structure of the HSBS occured at about 90 ℃ and its mechanical properties and size stability were significantly improved compared with parent SBS. In particular, HSBS4402-OH has superior performance. Its ion exchange capacity(IEC), water absorption and swelling degree at 30 ℃ were 1.99 mmol/g, 27.65% and 5.12%, respectively. Its ionic conductivity achieved 86.8 mS/cm at 80 ℃. And the loss of its ionic conductivity was only 8.3% even as the membrane was immersed in 2 mol/L NaOH solution for 432 h at 60 ℃. Apparently, this method can produce promising AEMs for anion exchange membrane fuel cells.

Key words: anion-exchange membrane, poly(styrene-b-butadiene-b-styrene) copolymer, crystalline structures, microphase separation