2.5.3. Transparency

The light transmission spectrum was determined by measuring the light absorption in the wavelength range of 200–800 nm using the spectrophotometer (model UV/Vis 4000, Dinko instruments, Barcelona, Spain). Triplicates of the film specimens of 20 mm × 50 mm were fixed to a test cell perpendicularly to the light beam. The transparency (T) was calculated following the Equation (2):

$$\mathrm{T}\left(\mathrm{mm}^{-1}\right) = \frac{\mathrm{A}\_{600}}{\mathrm{L}}\tag{2}$$

where A600 is the absorbance measured at 600 nm and L is the film thickness (mm).

#### 2.5.4. Water Contact Angle

The contact angle of water on the film surface was measured using an optical tensiometer (Theta Lite, Staffordshire, UK). Five droplets (5 μL) of ultrapure water were placed on different positions of three species (20 mm × 50 mm) of each sample and the mean values of the contact angle were calculated.
