WETTABILITIES OF AN HOMOPOLYMER AND AN COPOLYMER

Abstract

Investigation was made on wettabilities of polymer surface. In this study polyacrylonitrile (PAN), copolymer of acrylonitrile and p-styrenesulfonate (P (AN-SSS)), copolymer of acrylonitrile and styrene (P (AN-St)) were adopted as samples. An attempt has been made to elucidate the influence of both the terminal group and the molecular weight of PAN, and SSS or St content of copolymer, on the wetting properties.
Wetting properties of polymer films were estimated in terms of the surface tension (γ_s) of polymer which were calculated by the Extended Fowkes' Equation (1).
(1)
The equation was based on the following assumption; Surface tension of usual organic substances was divided into three components, which were dispersion forces (non-polar γ^a), interaction forces of polar characters (γ^b), and hydrogen bonding forces (γ^c). Substituting the values of contact angle (θ) which were measured with various liquids, and the values of these liquids' surface tension (γ_L) into Eq. (1), calculation was able to be made on γ_s.
The results were as follows:
(1) Wettability of film surface of PAN was not affected at all by the difference of molecular weight or difference of terminal group which was changed with a kind of catalyst. γ_s value of PAN was 55.4 dyne/cm.
(2) In regard to P (AN-SSS), γ_s value of polymer increased in proportion to the SSS content. This increasing behaviour was observed clearly in the region of 4 mole % content of SSS. SSS 9.3 mole % content polymer gave a surface which had highly wettability.
(3) In regard to P (AN-St), γ_s value of polymer decreased with St content increase. The effect of St on copolymer's γ_s value showed itself at the lower region of St content than with the case of SSS. This was caused because St component of copolymer was localized upon surface region.