Water contact angle (CA).
The CA of water in air on the film surface was measured using a CA analyzer
after a water drop of CA.
A total of 10 μL was placed on
the surface of film using a microsyringe
All film samples (3 × 10 cm) were glued on the movable
sample stage (black Teflon coated steel, 7 × 11 cm) leveled
horizontally before measurement. The CA on both sides
of the drop was measured to assume symmetry and horizontal
level.