Polyacetal and polyketal compositions

A new water-insoluble polymeric composition having polythiaacetal-ketal linkages therein, of the formula:

• ##STR21## wherein:
• R.sub.1 and R.sub.4 are independently selected from the group consisting of hydrogen and a monovalent residue of monomercaptans and monoalcohols, said monovalent residue that forms terminal groups being present in the statistical average polymer chain at least to about 50 mole percent of the terminal groups, and R.sub.1 and R.sub.4 are not both hydrogen in the statistical average polymer chain;
• R.sub.2 and R.sub.3 are independently selected from the group consisting of hydrogen and perchlorocarbyl and chlorohydrocarbyl radicals each having from 1 to 10 carbon atoms. X.sub.1, X.sub.2, X.sub.3 and X.sub.4 being independently selected from the group consisting of sulphur and oxygen with at least 30 mole percent of sulfur present in the total selection;
• A is the divalent residue of the compounds selected from the group consisting of dimercaptans, monomercapto alcohols and diols;
• and n is an integer from 2 to 50;
• said monovalent residue selected from the group consisting of primary alkyl, thia-alkyl, oxa-alkyl, aralkyl, alkenyl and mixtures thereof;
• and said divalent residue selected from the group consisting of primary alkylene, thia-alkylene, oxa-alkylene, aralkylene, and mixtures thereof.