I have made a thin hydrophobic polymeric film of Polycaprolactone on a metallic stage, by solving 1g of PCL 80000 in 10cc of Chloroform as solvent. As the film exposed to atmospheric pressure argon plasma jet, it changed its state to liquid, by removing the film out of the plasma exposure it returned to film state again. Does anyone know what is the reason?
Note 1. The melting point of PCL is about 59-64 degrees of centigrade, and our low temperature plasma does not reach that warmth.
Note 2. I have tried electrospun nanofibers of PCL by the mentiond plasma, although they did not change to liquid state.
Dear Ataollah,
Interesting results. I can suggest you the following:
- identify an estimate of crystallinity/amorphous percentage in the film. Simple way could be to observe your film under polarised optical microscope.
- also estimate the thickness of your film.
- metallic or underlying substrate wettability drastically influences the melting temperature of the film. PCL chain movement will be restrained on hydrophobic substrate compared to hydrophilic one. You can check substrate wettability by water contact angle measurement.
Depending on film thickness, crystallinity and underlying substrate wettability, you can correlate why your film 'melts' by the argon plasma jet.
Less crystalline film on a hydrophilic substrate may be susceptible to melt (liquify) easily.
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