Why use solvent method to prepare polymer film is always uneven and curled （dried in a blast drying oven） and what is the relationship between the transparency of the polymer film and the degree of crystallinity?
Of course, you get these results for many reasons, including the type of solvent used, as well as the humidity during the evaporation of the solvent in addition to the fact that there are some polymers that have a high sensitivity to moisture such as polylactic acid (PLA) .... With regards
Depending on the speed of evaporation and the choice of solvent, the film can become more or less curled. Moreover, the constant air flow in your oven might be responsible for the tendency of the polymer film to curl.
In my opinion, you could try to get a polymer film with lower surface roughness by changing to a solvent with a low vapor pressure and consequently a very slow removal from the polymer film. Also consider using a vacuum drying method instead of blast ovens.
On the other hand post-treatment including heated calendering could be much more convenient in your case, depending on the properties of the polymer film you want to investigate.
I don't want to give a general answer to your question regarding the correlation of film transparency and degree of crystallinity, because I've experienced varying results depending on the film composition so far. However, often the turbidity of the film is caused by light scattering on grain boundaries between the crystalline and amorphous parts of semicrystalline polymer films. Consequently a turbid film has a higher number of those grain boundaries, which correlate to a higher number of crystalline regions. In any case, it is much better to investigate the crystallinity of your film by other techniques like DSC, XRD or FTIR.
@Xie Linfang Following the above researchers suggestion, the transparency and the degree of crystalinity of polymer films very much depend on many factors.
For sure, a solvent is a major role to determine the properties of thin films if solutions processed films are involved. Even for the same polymer using different solvents to processed its films, the surface roughness and crystalinity of its films are very different.
Although other factors also play the roles for its properties of polymer thin films such as anealing temperatures, heating and cooling rates and etc.
Bear in mind that the properties of polymer thin films are for sure to depend on its polymer itself too such as molecular weight and transition temperatures.
You raised a very complicated question. The properties of polymer thin films varies from one polymer to another polymer and even for the same polymer.
would a solvent that evaporates faster mean less curling/warping of the film? Or is it polymer dependent?
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