| abstract |
The polymerizable compositions comprise: A) at least one polyiso(thio)cyanate monomer, and at least one polythiol monomer; or at least one episulfide compound and optionally one or more compounds having two or more functional groups capable of reacting with episulfide groups; and B) as polymerization catalyst, an effective amount of a salt of formula (MPm + Yn-), Y- is an anion such as the corresponding acid YH has a pKa fulfilling the condition 0.5 ≤ pKa ≤ 14 with the proviso that when the polymerizable compositions comprise an episulfide compound and MP+ is an ammonium group, the polymerizable composition also comprises an electro-donor compound. Application to the fabrication of optical articles, such as lenses. |