An Evaluation
of Local Thermal Analysis of Polymers
on the Sub-Micrometer Scale Using Heated Scanning Probe Microscopy
Cantilevers
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Abstract
A basic understanding of thermal
properties of polymers is of fundamental
importance for the development of advanced polymers. However, up to
now, mainly bulk properties have been investigated. To characterize
local softening processes in polymers, a local thermal analysis (LTA)
technique is applied as an add-on to a scanning probe microscope.
The development of a new generation of heatable cantilever probes
enables thermal analysis in the sub-μm range. This method is
based on an appropriate temperature calibration, which provides a
reliable correlation of the applied voltage heating the tip and the
actual temperature at the tip–sample interface. As the presented
technique is more susceptible to environmental changes than comparable
macroscopic methods, different parameters that might influence its
performance are evaluated like a strong dependence on sample temperature.
It is shown that the measured softening temperature on a polystyrene
(PS) sample decreases from 102.2 to 66.4 °C as the temperature
of the substrate is increased by 50 °C. The interaction between
heat from the cantilever and the substrate is the reason for local
sample softening, which opens new perspectives to understand the temperature
calibration process using the melting standard method. A stepwise
guideline for a suitable temperature calibration is provided