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Crystallization kinetics and crystal morphology in thin poly(ethylene oxide) films
M V Massa1, K Dalnoki-Veress, J A Forrest
1Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON, L8S 4M1, Canada.
The European Physical Journal. E, Soft Matter
|March 11, 2004
Summary
Thin film crystallization of poly(ethylene oxide) (PEO) shows a significant slowdown in crystal growth for films under 400 nm. Morphology changes to diffusion-controlled growth in thinner films, impacting crystallization kinetics.
Area of Science:
- Materials Science
- Polymer Science
- Physical Chemistry
Background:
- Crystallization kinetics are crucial for polymer properties.
- Thin film behavior can differ significantly from bulk due to surface and confinement effects.
- Understanding poly(ethylene oxide) (PEO) crystallization is important for its applications.
Purpose of the Study:
- To investigate the crystallization kinetics of poly(ethylene oxide) (PEO) thin films.
- To determine how film thickness affects PEO crystal growth rate and morphology.
- To explore the transition from bulk-like to thin-film specific crystallization behaviors.
Main Methods:
- Isothermal crystallization of monodisperse PEO films (13 nm to 2 µm) below the melting point.
- Optical microscopy to measure crystal growth rates.
- Atomic force microscopy (AFM) to analyze film morphology.
Main Results:
- A non-monotonic decrease in crystal growth rate observed for films thinner than approximately 400 nm.
- Growth rate reduction by a factor of 40 in the thinnest films compared to bulk.
- Diffusion-controlled growth morphologies (dendritic, densely branched) observed for films < 150 nm.
- Morphological changes correlate with observed changes in growth rate as a function of thickness.
Conclusions:
- Film thickness strongly influences PEO crystallization kinetics and morphology.
- Confinement effects lead to significant deviations from bulk crystallization behavior in thin PEO films.
- The observed morphological transitions are consistent with the changes in growth rate, highlighting the interplay between kinetics and structure in thin films.