AFM nanoscale thermal analysis
Atomic force microscopy (AFM) was performed on a Bruker
Nanoscope IIIa atomic force microscope. The modification of the
degradation temperature at the surface of the cellulose acetate
substrates was monitored using an AFM nanoscale thermal analysis
module (Vita). This technique allows the determination of the local
degradation temperature of polymers with nanoscale spatial resolution.
The increase in temperature causes a progressive thermal
expansion of the polymer, which leads to a cantilever deflection.
When the probe temperature reaches a transition temperature of
the polymer (such as the glass transition temperature), the probe
penetrates into the sample. This penetration causes an opposite
deflection that can be detected by the microscope. The deflection
depends on the temperature of the probe. By plotting the variation
of the deflection as a function of temperature, the Tg can be
determined, which corresponds to the maximum of the curve.
Measurements were performed on irradiated and non-irradiated
CA samples to investigate potential changes in the thermal properties
of the samples during irradiation. Each measurement was