Characterization of Heterogeneous Regions in Polymer Systems Using Tapping Mode and Force Mode Atomic Force Microscopy.
Characterization of Heterogeneous Regions in Polymer
Systems Using Tapping Mode and Force Mode Atomic Force
Microscopy.
(720 K)
Raghavan, D.; VanLandingham, M. R.; Gu, X.; Nguyen, T.
Langmuir, Vol. 16, No. 24, 9448-9459, 2000.
Keywords:
microscopy; polymethyl methacrylate; blends; coatings;
chemical properties; mechanical properties;
microstructure; nanoindentation; phase contrast
Abstract:
Characterization of polymer coating surfaces is crucial
to understanding and predicting the long-term
performance of coatings in aggressive environments. The
exposed polymer surface and near-surface regions can
differ from the bulk polymer film both chemically and
mechanically, which can effect the durability of the
coating and its ability to protect the underlying
substrate. In this study, atomic force microscopy (AFM)
is used to investigate the heterogeneity of blended
films of poly (methylmethacrylate) (PMMA) and
polybutadiene (PB) on silicon substrates before and
after annealing. The blended films with different ratios
of PMMA to PB are prepared by spin casting onto silicon
substrates from solution. The surface morphology and
composition of these cast films are investigated using
tapping mode and force mode AFM. Annealing the samples
in air at 75 C + 5 deg C causes changes in the relative
chemical and mechanical differences between PMMA and PB,
so the phase image contrast is studied as a function of
annealing time. The effect of tapping force level on
phase image contrast is also explored. To identify the
different components in polymer blends and to understand
the influence of relative surface stiffness on the phase
images, nanoscale indentation measurements. A loss in
phase contrast between PB-rich and PMMA-rich regions is
observed as a function of heating time. This observation
correlates well with the increases in glass transition
temperature, modulus, and polarity of pure PB with
respect to pure PMMA.
