Silane coupling agents polyimide-mineral oxide composites

A composite product comprising substrates selected from the group consisting of a mineral oxide and a metal adhered to a polyimide with an adhesion promoter positioned between said substrate and said polyimide, said promoter having the formula ##STR30## wherein A is selected from the group consisting of ##STR31## wherein R is a divalent radical having more than two carbon atoms, R.sup.1 is lower alkyl from 1 to 6 carbon atoms, R.sup.11 is OR.sup.1 or lower alkyl from 1 to 6 carbon atoms, R.sup.111 is hydrogen or lower alkyl from 1 to 6 carbon atoms and Ar is an aromatic group.