Insulative composition for forming polymeric electric current regulating junctions

Electric current regulating junction comprising a normally insulative, electrically activatable composition disposed as a layer 0.1 to 2540 microns in thickness having an electric resistance greater than 10.sup.8 ohms through its thickness, said composition consisting essentially of 10 to 85 volume percent of a substantially linear, unitary polymeric binder having 15 to 90 volume percent of particles of aluminum substantially homogeneously dispersed in it, said aluminum particles having electrically conductive metallic interiors and thin electrically insulative surface coatings of aluminum oxide sufficient to impart electric resistance between two or more of said particles in contact with one another, the amounts of said binder and particles totaling 100 volume percent, the unitary polymer in said binder having a glass transition temperature of at least 100.degree. C. and being selected from aromatic polyimides, aromatic poly(amide-imides), aromatic poly(ester-imides) and aromatic polyamides, said junction being capable of being (a) activated solely by electrical means from a high to a low electric resistance state in which it will function as an ohmic conductor capable of passing a relatively low reading current, (b) activated solely by electrical means so as to be switched between low electric resistance and relatively high electric resistance states and vice versa, (c) switches from the low resistance to the high resistance state solely by application of relatively low electric currents which are at least 10 times the magnitude of said reading current and which are in the form of current-limited pulses which have a duration not exceeding 100 milliseconds and provide switch-off energy of up to 0.1 joule, said pulse being regulated so that at the end thereof the current pulse will decay rapidly, and (d) used in an alterable read-only memory system.