(163ag) Nanoscale Morphology of Ionomer Systems

The morphology of poly(styrene-ran-styrene
sulfonate) (P(S-SS_x)) ionomers has been investigated extensively by
several research groups.[1-3]  However,
only our 2001 publication has applied the method of scanning transmission
electron microscopy (STEM) to probe the size, shape and spatial distribution of
the ionic aggregates is these ionomers.[4] 
This analytical electron microscopy method minimizes phase contrast that
can obscures nano-scale features and accentuates differences in atomic
number.  We recently reported
quantitative agreement between results obtained by STEM and by small angle
x-ray scattering (SAXS) in a Cu-neutralized poly(styrene-ran-methacrylic acid) (SMAA)
ionomer.[5]  This is the first report of
quantitative agreement regarding the size of spherical ionic aggregates as
determined by an imaging and a scattering method.  We now apply these STEM and SAXS methods to characterize the
morphologies of P(S-SS_x) random copolymers neutralized with various
cations.  Combining direct imaging and
X-ray scattering of sulfonated polystyrene systems will resolve uncertainties
in the morphologies of these materials and serve as a guide to explain its many
unique physical properties. 

[1] Yarusso, D.; Cooper, S. L., Macromolecules 1983, 16, 1871.

[2]O'Connell,
E.M.; Root; T.W.; Cooper, S.L., Macromolecules 1995, 11, 3995.

[3] Ding, S.Y.; Hubbard, S.R.;
Hodgson, K.O; Register, R.R.; Cooper, S.L., Macromolecules, 1988,
21, 1698.

[4] Kirkmeyer, B. P.; Weiss, R. A.;
Winey, K. I., Journal of Polymer Science:
Part B: Polymer Physics 2001,
39, 477.

[5] Benetatos, N.M.; Winey, K.I., Macromolecules,
submitted.