A radiation-polymerizable mixture comprising a binder which is insoluble in water, but soluble or at least swellable in aqueous alkaline solutions; a radiation-activatable polymerization initiator; and a polymerizable polypropylene glycol diester with acrylic or methacrylic acid corresponding to the formula: ##STR1## wherein R represents a hydrogen atom or a methyl group and n represents a number from 2 to 13; and a light-sensitive copying material comprising a support and a light-sensitive layer comprising a mixture of the foregoing type. The radiation-polymerizable mixture of the invention produces non-tacky layers which exhibit a low sensitivity to atmospheric oxygen and are useful as dry or liquid photoresists.