TY - JOUR
T1 - Direct observation of ionic aggregates in sulphonated polystyrene ionomers
AU - Li, Chi
AU - Register, Richard A.
AU - Cooper, Stuart L.
N1 - Funding Information:
The authors thank the staff of the NIH Integrated MicroscopyR esourcea t the Universityo f Wisconsina t Madison for microscopea ccessand training. In this regards, peciatl hanksa re dueto Drs James B. Pawleya nd Peter H. Cooke. This work was supportedin part by the Office of Naval Researchth roughG rantN00014-83-K0423 and the Division of MaterialsR esearcho f the National Science Foundation through Grant DMR-86-03839. R.A.R. wishes to thank the Fannie and John Hertz Foundationfo r supportw hile thisw ork was performed.
PY - 1989/7
Y1 - 1989/7
N2 - Applications of electron microscopy to ionomers have not generally been successful in the past, due to the small size of the ionic aggregates and their irregular distribution throughout the polymer matrix. Ionic domains were observed in samples of Zn2+ and Ni2+ neutralized sulphonated polystyrene (SPS), at sulphonation levels of 1.68 mol% and 3.37 mol%, using high-voltage (1.0 MeV) electron microscopy (HVEM). The specimens were solvent-cast films which contained suitable 'thin spots' only a few interaggregate dimensions thick. The observed contrast is not due to phase grain artifact, as demonstrated by a through-focus series of micrographs of the Zn2+ ionomer and polystyrene homopolymer. Contrast was observed only in the former case. The aggregates are approximately spherical and roughly 3 nm in diameter, and appear identical for both Ni2+ and Zn2+ materials. However, Cs+ neutralized SPS exhibited no ionic aggregates. This is probably due to the rapid rate of solvent evaporation coupled with the weaker coulombic forces in the Cs+ neutralized material, both of which hinder the formation of ionic aggregates.
AB - Applications of electron microscopy to ionomers have not generally been successful in the past, due to the small size of the ionic aggregates and their irregular distribution throughout the polymer matrix. Ionic domains were observed in samples of Zn2+ and Ni2+ neutralized sulphonated polystyrene (SPS), at sulphonation levels of 1.68 mol% and 3.37 mol%, using high-voltage (1.0 MeV) electron microscopy (HVEM). The specimens were solvent-cast films which contained suitable 'thin spots' only a few interaggregate dimensions thick. The observed contrast is not due to phase grain artifact, as demonstrated by a through-focus series of micrographs of the Zn2+ ionomer and polystyrene homopolymer. Contrast was observed only in the former case. The aggregates are approximately spherical and roughly 3 nm in diameter, and appear identical for both Ni2+ and Zn2+ materials. However, Cs+ neutralized SPS exhibited no ionic aggregates. This is probably due to the rapid rate of solvent evaporation coupled with the weaker coulombic forces in the Cs+ neutralized material, both of which hinder the formation of ionic aggregates.
KW - high-voltage electron microscopy (HVEM)
KW - ionic aggregate
KW - ionomer
KW - lightly sulphonated polystyrene
KW - transmission electron microscopy (TEM)
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U2 - 10.1016/0032-3861(89)90040-2
DO - 10.1016/0032-3861(89)90040-2
M3 - Article
AN - SCOPUS:0024698018
SN - 0032-3861
VL - 30
SP - 1227
EP - 1233
JO - Polymer
JF - Polymer
IS - 7
ER -