Excluded volume and surface activity of block copolymers with lonizable groups: Lonene-tetrahydrofuran block copolymers

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Abstract
ABA type block polyelectrolytes were prepared by quarternization reaction of the one end of 3, 3-ionene chloride (A) with end-brominated polytetrahydrofuran (B). Intrinsic viscosities of the block copolymers were measured in KBr-methanol solution and the viscosity equations were established. The excluded volume effect of the block polyelectrolyte was examined by using the theories of Kurata, Alexandrowicz, Ptitsyn, and Fixman. The expansion factor α3 was a function of ī(N/CS)½, even for the block polyelectrolyte, where ī is the degree of ionization, N is the degree of polymerization, and Cs is the salt concentration, and Ptitsyn's excluded volume function for block polyelectrolyte did not fit the experiments. Since the block polyelectrolyte was surface-active, the surface tension of the aqueous block co-polymer solutions was also measured. The direct measurements of the surface excess and the thickness of adsorbed block co-polymer layer were carried out by ellipsometry. The observed values of surface excess were compared with those values obtained from the Gibbs equation of polyelectrolyte adsorption with an appropriate correction for non-ideality of solutions. Fair agreement was observed. From the ellipsometry, the conformation of the block copolymer adsorbed on the air-water interface was inferred as a hair-pin type conformation, in which the ionene blocks were stretched normal to the surface while the tetrahydrofuran block floated on the water surface.