Abstract
The presence of free hydroxyls in polyvinyl alcohol presents a multitude of opportunities for changing the properties of this polymer, a fact which is of considerable theoretical and practical interest. The results are presented of a study of the incorporation of nitrile and amino groups in polyvinyl alcohol. Despite the fact that the cyanoethylation reaction has been described in the literature it is still insufficiently elucidated. The reaction was carried out in an organic medium. The present investigation is concerned with the effect on the extend of cyanoethylation of the chemical nature of the substance used as reaction medium, of the preliminary swelling of the polymer, of the molar ratio of the reactants, and of the reaction time. The relation between the degree of crystallinity of polyvinyl alcohol and its reactivity in the cyanoethylation reaction has been determined. It was found that with growth in crystallinity there is a fall in reactivity and in exent of cyanoethylation. It follows from this that the reaction takes place predominately in amorphous regions. Depending upon the degree of cyanoethylation, polyinyl alcohol changes its structure, being transformed into a rubberlike mass. The solubility of polyvinyl alcohol in water also falls with increasing cyanoethylation. Polyvinyl alcohol with 35โ40% cyanoethylated hydroxyl groups is insoluble in water even on heating. On reducing the cyanoethylated Polymer, the polyaminopropyl vinyl ether is obtained.
The effect of the reaction medium, pressure, temperature, concentration, type of catalyst, etc. on the degree of reduction has been investigated. The greatest influence is exerted by the degree of cyanoethylation of the initial polymer. Polyvinyl alcohol having 30โ35% of the hydroxyl group sin ether linkage with propanolamine has been synthesized. The polymer is insoluble in water and methanol, is partially soluble in acetone, benzene, and dimethylformamide and has the appearance of a rubbery mass.