Amphiphilic copolymers 1 a-1 d were prepared by radical copolymerization of hydrophilic Nphenylmaleimide derivatives and lipophilic vinyl ethers in dichloromethane. Though the starting concentrations of the two monomers were always equimolar, none of the copolymers had a strictly alternating structure. Molecular weights were between lo4 and 9 . lo4. The copolymers prepared from ethyl 4-maleimidobenzoate (2a) and isobutyl vinyl ether (3a) (copolymer la), and 2a and isooctyl vinyl ether (3b) (copolymer 1 b) were thermally stable up to 300 "C and showed glass transitions at about 150 "C, while the copolymers prepared from 2a and octadecyl vinyl ether (3c) (copolymer 1 c), and 4-maleimidobenzoic acid (2b) and 3 c (copolymer 1 d) were considerably less stable. All copolymers formed stable, condensed monomolecular layers at the air-water interface, which could be transferred onto hydrophobic supports by the Langmuir-Blodgett (LB) technique. Up to the 20th dipping cycle, a Y-type deposition was found, while further dipping predominantly led to Z-type deposition. Nitrogen and oxygen permeabilities (P) were studied after depositing the LB films onto porous Celgard membranes. Permeability and selectivity were dependent on the nature of the alkyl substituent group of the polymer. Copolymer l a with the isobutyl group showed higher permeabilities than copolymer 1 c with the octadecyl group, but no selectivity. The copolymer with the small alkyl group showed no selectivity of oxygen over nitrogen (a = PoI/PN2), while for the copolymer with the long alkyl chain the a-value was 1,3.