Jr. Isasi et al., HYDROGEN-BONDING AND SEQUENCE DISTRIBUTION IN POLY(VINYL ACETATE-CO-VINYL ALCOHOL) COPOLYMERS, Macromolecules, 27(8), 1994, pp. 2200-2205
The correlation between hydrogen-bonding self-association and sequence
distribution in different poly(vinyl acetate-co-vinyl alcohol) copoly
mers (ACA) of different degrees of hydrolysis and sequence distributio
ns has been studied by infrared and NMR spectroscopy. For ACA copolyme
rs, quasi-random distributions are obtained by acid alcoholysis, block
ier distributions by saponification, and intermediate distributions by
a combined method, as shown by C-13 NMR. FTIR spectroscopy has pointe
d out that hydrogen-bonding distribution in ACA copolymers strongly de
pends on sequence distribution. For block copolymers, hydroxyl-hydroxy
l self-association is preferred, However, in random copolymers, a stro
ng competition between hydroxyl-hydroxyl and hydroxyl-carbonyl associa
tion is observed. Hydroxyl-carbonyl association seems to occur between
adjacent repeat units, leading to cyclic structures with a high therm
al stability.