Determining Phase Transformation Route

Table of Contents

Introduction
Measurements and Results
Conclusions

Introduction

Polymers generally undergo various thermal transformations all through the manufacturing process – right from their synthesis in a reactor, to product shaping processes like injection molding or film formation.

Quenching can also be a significant step in processing – for instance, to preserve a particular nanostructure orientation, or an out-of-equilibrium phase.

Since polymers may self-organize into structures over a broad size range, from the atomic scale to several tens of nanometers, simultaneous Small-Angle/Wide-Angle X-ray Scattering (SAXS/WAXS) is an indispensable tool for analyzing these materials.

During thermal processing, simultaneous data collection can be particularly informative as it enables dynamic in-situ multi-scale examination of the nanostructure as well as the crystalline phase, allowing the route of phase transformation to be investigated.

Measurements and Results

A 20 µm solvent cast thick film of fluoropolymer was measured on the Xeuss 2.0 SAXS/ WAXS system in simultaneous SAXS/WAXS mode.

Using an integrated temperature control stage (Linkam HFSX350), the system was heated from room temperature to 130 °C at 1 °C/minute. The sample had not been heated before. SAXS and WAXS data was collected side-by-side with a dual detector set-up.

It is known that this particular fluoropolymer undergoes a ferroelectric to paraelectric transition during thermal processing, called the Curie transition. This is a reversible transition, but the sample has to be stabilized only once.

The resulting 1D SAXS and WAXS curves as a function of temperature is shown in Figure 1. These results provide data on the lamellar phase nanostructure as well as the crystalline phase evolution as a function of temperature.

SAXS and WAXS study of a fluoropolymer film

Figure 1. Simultaneous SAXS (left) and WAXS (right) study of a fluoropolymer film during first heating and cooling. Ramp at 1 °C/min (far left). 2D representation of SAXS and WAXS 1D curves as a function of temperature. Each horizontal pixel line corresponds to a 1D curve.

As the crystalline peaks remain at the same position, the reversible nature of the transition is clearly demonstrated by the WAXS data. It is observed from the SAXS data that the long period moves from 14 nm to 32 nm after the Curie temperature is exceeded the first time.

No further shift of the long period is observed in the following thermal cycles. It is thus inferred that stabilization was achieved after the first thermal cycle, after which the phase transition becomes entirely reversible.

Conclusions

With the help of the Xeuss 2.0 or the Nano-inXider SAXS/WAXS systems, in-situ experiments of polymer films as a function of thermal treatments, which could previously only be conducted on synchrotron beamlines1,2, can now be performed in the laboratory.

Xenocs SAXS/WAXS systems enable a wide range of dynamic and kinetic in-situ multi-scale studies using specific environmental control stages, such as a stretching cell or a humidity control stage.

References

  1. P. Panine et al., Polymer, 2008, 49, 676-680
  2. Wang et al., Macromolecules, 2000, 33, 978-989

Xenocs

This information has been sourced, reviewed and adapted from materials provided by Xenocs.

For more information on this source, please visit Xenocs.

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