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Published on: June 7, 2018
Morphological changes during annealing of polyethylene nanocrystals
1Physikalisches Institut, Albert-Ludwigs Universität Freiburg, Germany. nandita.basu@physik.uni-freiburg.de
The European Physical Journal. E, Soft Matter
|March 21, 2012
Summary
Polymer nanocrystals coarsen and thicken upon annealing below their melting point. These morphological changes, driven by chain unfolding and diffusion, occur even at lower temperatures due to their high surface area.
Area of Science:
- Materials Science
- Polymer Science
- Nanotechnology
Background:
- Polymer crystals are metastable and prone to morphological changes during annealing.
- Understanding these changes at the molecular level is crucial for controlling material properties.
Purpose of the Study:
- To investigate the morphological evolution of polymer nanocrystals during annealing.
- To observe changes in topography and viscoelastic properties at the molecular scale.
Main Methods:
- Generated polyethylene nanocrystal stripes via evaporative dewetting.
- Utilized atomic force microscopy to monitor topography and viscoelasticity.
- Annealed samples at progressively higher temperatures below the melting point.
Main Results:
- Nanocrystal coarsening observed at 75°C (60°C below melting point) without fold reduction.
- Chain folds removed and crystal thickening initiated around 110°C.
- Surface diffusion of molten polymers led to crystal disappearance at higher temperatures.
Conclusions:
- The small size and high surface-to-volume ratio of nanocrystals accelerate morphological changes.
- Annealing-induced transformations, including coarsening and thickening, occur significantly below the bulk melting point.
- These findings provide insights into polymer crystal stability and transformation mechanisms.
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