Bis-maleimide compounds of the formula: ##STR1## where R' is an alkenylene or alkylene group; the R" groups are independently hydrocarbon or halohydrocarbon groups; and n is an integer, are hydrolytically stable compounds which may be thermally cured, or co-cured with other radically cureable monomers, to provide crosslinked polymer with good thermal properties. Compounds of the formula where n is above about 9 can be used as additives for radically cureable silicone formulations.