Method for preparing polythiols

A process for controlling regioselectivity of

• prepared polythiols comprising:
• preparing a sulfhydration reaction medium comprising bringing into contact in a reactor:
• at least one polyene;
• at least one radical initiator that includes a photochemical radical initiator;
• at least one heterogeneous acid catalyst that is a resin;
• at least one sulfhydryl group donor compound;
• optionally, at least one solvent;
• simultaneously carrying out the radical sulfhydration reaction of said at least one polyene and the acid-catalyzed sulfhydration reaction of said at least one polyene which includes irradiation of the reaction medium at wavelengths sufficient to obtain radical initiation;
• and
• recovering a mixture comprising least substituted polythiols and most substituted polythiols, wherein for the least substituted polythiols, the sulhydryl group of the sulfhydryl group donor is predominantly attached to the least substituted carbon atoms of the polythiol when the sulfhydration reaction is radical initiated, and wherein for the most substituted polythiol, the sulhydryl group of the sulfhydryl group donor is predominantly attached to the most substituted carbon atoms of the polythiol when the sulfhydration reaction is acid-catalyzed, and where the ratio between the least substituted polythiol formed and the most substituted polythiol formed is controlled by adjusting the radical initiated and the acid-catalyzed reaction conditions,
• wherein said at least one sulfhydryl group donor compound is chosen from hydrogen sulfide, thiocarboxylic acids and dialkyl di- and poly-sulfides, taken alone or as a combination of two or more thereof.