Surface free energy of poly(vinyl alcohol) modified with alkyl groups

Abstract

The dispersive component of surface free energy γ S d and the nondispersive interactions with polar liquids I SW were determined for poly(vinyl alcohol) (PVA) copolymers having various types of alkyl groups, i.e., four kinds of partly alkyl acetalized PVA's (AIPVA), butyl vinyl ether — vinyl alcohol copolymers (BuVA), ethylene — vinyl alcohol copolymers (EtVA) and BuPVAPVA mixtures. γ S d and I SW were estimated from the measurements of contact angles by means of a two-liquid method proposed by Matsunaga and Ikada. γ S d and I SW for AIPVA, which were smaller than those for PVA itself, decreased with increases in either content or chain-length of the alkyl side group, while γ S d for EtVA was virtually independent of ethylene content. The dependences of γ S d and I SW on the alkyl side chain content per vinyl repeating unit for BuPVA were smaller than those for BuVA. The result for the polymer blends of PVA and BuPVA showed that both γ S d and I SW fell rapidly even at very small addition of BuPVA. The surface free energy γ S (= γ post|staggered|S d + γ S d) was found to decrease with increasing alkyl group content except for EtVA.