Cationically polymerizable compositions containing group VIa onium salts

Cationically polymerizable compositions consisting essentially of

• A. a monomeric or prepolymeric cationically polymerizable organic material free of oxirane oxygen selected from vinyl organic monomers, vinyl organic propolymers, cyclic organic ethers, cyclic organic esters, cyclic organic sulfides, cyclic amines and organosilicon cyclics, and
• B. an effective amount of photodecomposable armoatic onium salt of a GRoup VIa element capable of effecting the cationic polymerization of (A) when exposed to radiant energy where said photodecomposable aromatic onium salt of a Group VIa element has the formula,
• [(R).sub. (R.sup.1).sub.b (R.sup.2).sub.c X] .sub.d.sup.+ [MQ.sub.e) .sup.-(e-f)
• where R is a monovalent aromatic orgnic radical, R.sup.1 is a monovalent organic aliphatic radical selected from alkyl, cycloalkyl and substituted alkyl, R.sup.2 is a polyvalent organic radical forming a heterocyclic or fused ring structure selected from aliphatic radicals and aromatic radicals, X is a Group VIa element selected from sulfur, selenium and tellurium, M is a metal or metalloid, Q is a halogen radical, a is a whole number equal to 0 to 3 inclusive, b is a whole number equal to 0 to 2 inclusive, c is a whole number equal to 0 or 1, where the sum of a + b + c is a value equal to 3 or the valence of X,
• d=e-f
• f=valence of M and is an integer
• equal to from 2-7 inclusive
• e is >f and is an integer having a value up to 8.