The measurement of the contact angle between pure water and the graft copolymer surface was one of the easiest ways to characterize the hydrophilicity of the graft copolymer surface. A hydrophobic surface with a low free energy produces a high contact angle with water, whereas a wet high-energy surface allows the drop to spread, i.e., produces a low contact angle.Fig. 6 shows the variant dependence of the static contact
angle (SCA) of the CG, the PVA and the CG-g-PVA at 1:9 and 3:7
CG:PVA. The plot indicates that the SCA of the samples underwent
a significant change. For the original PVA, the surface was
very hydrophobic, and the measured water contact angle was 93.6◦,
while the measured water contact angle of the CG was 11.55◦. After
the CG was grafted with the PVA, the water contact angle declined
gradually to 43–58◦. This behavior is likely to be associated with the
graft copolymer of the polymer molecule in the polymer matrix. In
addition, this behavior is primarily caused by the reorientation of the polar function groups toward the outer surface of the sample
film.