Abstract: Novel ultrathin unit layers and built-up multilayers are obtained when a spreadable polyfunctional aldehyde or its precursor, particularly the alkyl Schiff base formed by its condensation with an alkyl amine, is spread on the surface of an aqueous subphase containing a diamine. The resulting polymeric imine unit layers were transferred and built up on substrates which included quartz, aluminum and chrome-plated glass, and semiconductors.

Abstract: A urea adsorbent and a method for its production are disclosed, the adsorbent comprising hollow microspheres each having an outer layer formed of a urea-permeable polymer and an inner layer formed of a polymer containing a polyoxyalkylene glycol derivative expressed by the following formula:--(CH.sub.2).sub.n -O--.sub.m Rwherein R stands for hydrogen or a methyl group and n is an integer of 2-5 and m is an integer of at least 3. The adsorbent can selectively adsorb urea with a high adsorbing activity and does not interact with other substances than urea and, therefore, is useful as a artificial kidney. The adsorbent may be prepared by subjecting a w/o/w type emulsion to polymerization wherein a radical polymerizable polyoxyalkylene glycol derivative is dissolved in the inner aqueous phase of the emulsion and an oil-soluble radical polymerizable monomer is used as the outer oil phase.