Abstract:
Provided is a polymerizable composition of (a) a monomer composition including ethylenically unsaturated monomer having a β-epithiopropyl functional group; (b) optionally, a compound having two or more β-epithiopropyl functional groups but no polymerizable ethylenically unsaturated groups; (c) an isourea functional polymerization initiator; and (d) a catalyst for reaction between the β-epithiopropyl functional groups. Also provided is a method of reducing the yellowness index of a sulfur-containing polymerizate prepared by addition polymerization, the method including reacting in the presence of an isourea functional polymerization initiator and a catalyst for reaction between β-epithiopropyl functional groups, a polymerizable composition of: (a) a monomer composition including ethylenically unsaturated monomer having a β-epithiopropyl functional group; and, optionally, (b) a compound having two or more β-epithiopropyl functional groups but no polymerizable ethylenically unsaturated groups.