Molecular architecture and physicochemical properties of some vinyl alcohol‐vinyl acetate copolymers

• Published in: Journal of polymer science. Polymer physics edition 1979-10, Vol.17 (10), p.1771-1787
• Main Authors: Scholtens, B. J. R., Bijsterbosch, B. H.
• Format: Article
• Language: English
• Subjects: Laboratorium voor Fysische chemie en Kolloïdkunde; Physical Chemistry and Colloid Science
• ISSN: 0098-1273; 1542-9385
• DOI: 10.1002/pol.1979.180171012

Two series of vinyl alcohol‐vinyl acetate copolymers were prepared by homogeneous and heterogeneous acetylation of the same precursor poly(vinyl alcohol). Their intramolecular monomer distributions were analyzed by IR spectrometry, calorimetry, and differential thermal analysis. The results show a more blocky distribution for the heterogeneously prepared copolymers. The properties of these (co)polymers in dilute aqueous solution were determined by means of viscometry. Whereas the copolymer‐solvent interaction parameter of the homogeneously acetylated, random copolymers hardly varied with acetate content, a definite minimum was found for the blocky copolymers at about 7 mole% vinyl acetate. These findings were attributed to the incompatibility of dissimilar sequences, which sharply decreases with decreasing vinyl acetate sequence length. Up to about 17 mole% vinyl acetate content, the solvent quality for the copolymers is at least as good as for poly(vinyl alcohol). In addition, the dilute solution properties of the samples were established in water saturated with 1‐butanol. For copolymers with up to about 17 mole% vinyl acetate, at 25°C this mixture is a better solvent than water. The highest increase in solvent quality was found for the homopolymer, whereas the increase diminished with acetate content, irrespective of the intramolecular vinyl acetate distribution. These findings are explained in terms of preferential adsorption of 1‐butanol onto the (co)polymer backbone due to hydrophobic interactions and prevention of this process by the bulky acetate groups.