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Mohanty, Aruna Kumar,Devaraju, Subramani,Kim, Nowon,Paik, Hyun-jong Elsevier 2018 Solid state ionics Vol.314 No.-
<P><B>Abstract</B></P> <P>A class of poly(ether sulfone) (FPES) block copolymers containing pendent quaternary ammonium (QA) and imidazolium (IM) groups were prepared as anion exchange membranes by reaction involving nucleophilic substitution, benzylic bromination, quaternization and anion exchange with hydroxide ions. Highly reactive hexafluorobenzene (HFB) was utilized as a linkage group for relatively low temperature (e.g., 105°C) coupling between hydrophobic and precursor hydrophilic oligomer blocks. The phase separated morphology, water uptake, swelling ratio, conductivity, and chemical stability of the resultant copolymer membranes were also investigated. The hydroxide conductivity of the ionomer membranes (IEC~2.0 mequiv./g) was 21–22mS/cm and 56–63mS/cm at 30°C and 80°C respectively. The FPES-IM membrane showed relatively very good dimensional integrity in high pH solution, whereas under the similar condition the FPES-QA membrane broke into pieces. However, the degradation of the imidazolium cations in FPES-IM was relatively faster in comparison to the ammonium cations in FPES-QA.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Anion exchange membranes were prepared using hexafluorobenzene as a linkage group. </LI> <LI> Quaternary ammonium has better alkaline stability than imidazolium cations. </LI> <LI> Block copolymer anion exchange membranes exhibited nano-phase separation in AFM. </LI> <LI> Good hydroxide ion conductivity up to 63mS/cm at 80°C was observed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Mohanty, Aruna Kumar,Ye, Jihwa,Ahn, Junyoung,Yun, Taeil,Lee, Taeheon,Kim, Kyung-su,Jeon, Heung Bae,Chang, Taihyun,Paik, Hyun-jong American Chemical Society 2018 Macromolecules Vol.51 No.14
<P>A polyring capable of reversible growth and dissociation is synthesized from a tricyclic polystyrene (PS) prepared by combining atom transfer radical polymerization of a 4-arm star-shaped PS and azide-alkyne click reactions. In the preparation of the tricyclic PS, a coupling agent containing a disulfide linkage is used in the click cyclization reaction. The reduction of the disulfide linkage in the tricyclic PS results in an 8-shaped PS with thiol groups which on oxidation leads to a high molecular weight polyring. The topology transformation between the polymers occurs via reversible redox reaction of disulfide/thiol. The high molecular weight of the polyring is realized due to the formation of flexible S-S linkage between the 8-shaped PSs. Their structures are confirmed by FT-IR, <SUP>1</SUP>H NMR, SEC, and MALDI-TOF MS analyses. In addition, molecular weight control of the polyring according to polymer concentration has been confirmed through SEC analysis.</P> [FIG OMISSION]</BR>