Surface free‐energy analysis of poly(N‐vinyl‐2‐pyrrolidone–crotonic acid) copolymers prepared by γ‐ray‐induced polymerization technique

Pure poly(N‐vinyl‐2‐pyrrolidone) (PVP) and P(VP–crotonic acid) [P(VP/CrA)] copolymers with different CrA contents were prepared by the γ‐ray‐induced polymerization technique. The change in the surface free energy of the copolymers was investigated using the Van Oss–Good contact angle evaluation methodology in order to estimate their wettability properties. The apolar Lifshitz–van der Waals component (γ ) and the electron donor component (γ ) of the PVP network were calculated as 27.6 and 56.5 mN m−1, respectively. In this case, the surface of the PVP network had a basic character (electron donor). By contrast, the γ component of P(VP/CrA) copolymers increased and then remained almost constant with increasing CrA content. In addition, the surface of these copolymers changed from a basic character (γ = 56.5 mN m−1) to an acidic character (γ = 0.07 mN m−1) with increasing CrA contents in the copolymer.