Method of producing a curable composition containing 4,4'-bis(methacryloylthio)diphenylsulfide

A method of producing a curable composition containing a prepolymer having a polythioether skeleton comprising addition reacting (A) 4,4'-bis (methacryloylthio)diphenylsulfide having the formula (I):

• ##STR28## and (B) (ii) a polythiol having the formula (II):
• R--(SH).sub.n (II)
• wherein R is a polyvalent organic group comprising an aliphatic or aromatic hydrocarbon and n represents an integer of 2 or more, with the functional group equivalent ratio of the mercapto groups of the component (B) (ii) to the methacryloyl groups of the component (A) being from 0.02 to 1.01, with at least one other vinyl monomer selected from the group consisting of aromatic vinyl compounds, unsaturated fatty acids and derivatives thereof, unsaturated dibasic acids and derivatives thereof, and vinyl cyanide compounds, said at least one other vinyl monomer being copolymerizable with said 4,4'-bis (methacryloylthio)diphenylsulfide in the presence of a base catalyst.