DISTRIBUTION OF COMPOSITIONAL DEFECTS IN SOLVENT CAST POLYVINYL-ALCOHOL FILMS - ANGULAR DEPENDENT XPS AND REACTIVITY STUDY

Polyvinyl alcohol polymer [-(CH2-HCOH)n-] generally contains carboxylates and carbonyl groups as compositional defects along the chain. The depth profile of these defects in solvent cast films was investigated by angular dependent XPS. Acetate and carboxylate groups were preferentially segregated in the topmost layer ( ∼ 3 Å) of the film. A six-fold enhancement over the bulk concentration was observed with accompanying depletion of all other carbon species from the surface. Carbonyl groups did not show any tendency to segregate. Annealing at 100 ° C resulted in rapid loss of carboxylate -COO- intensity followed by a slow steady decline. Angular dependent XPS indicated that the loss of -COO- groups was not due to migration into the bulk but most likely due to decomposition or volatilization. These observations are consistent with segregation of low surface free energy components. Surface acetate and carboxylate groups reacted readily with trimethyl aluminum at room temperature resulting in the formation of Al-polymer complexes. The observed segregation of acetate and carboxylate groups is the first example of such a process driven by isolated pendent groups. © 1990.