Why are certain hot polycarbonate films stickier than others? Molecular weight? Hydrolysis?

In van der waals dry transfer, we pick up flakes of materials such as graphene using polymer films. The material is exfoliated onto an SiO2 covered wafer and picked off using the polymer film. It's obviously pretty bad if the film sticks to the SiO2 itself, otherwise you wind up tearing and distorting your film trying to get it back off.


It's often necessary to try and pick up the flakes at elevated temperatures -- around 100-120 degrees C. It's at this point that some films get extremely tenacious and will not peel off the SiO2. The films that are the best seem to be the ones made on days with high humidity. Occasionally, water steam treatment seems to help. It would therefore seem to me that the PC is being hydrolyzed and broken into lower molecular weight pieces. Just a guess -- but if so, why would this make the film less sticky? If not, I would love to know why!


