New amphiphilic copolymers of N‐phenylmaleimides and vinyl ethers: thermal properties, Langmuir and Langmuir‐Blodgett films, gas permeation

Abstract

AbstractAmphiphilic copolymers 1 a–1d were prepared by radical copolymerization of hydrophilic N‐phenylmaleimide 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 104 and 9 · 104. The copolymers prepared from ethyl 4‐maleimidobenzoate (2a) and isobutyl vinyl ether (3a) (copolymer 1a), and 2a and isooctyl vinyl ether (3b) (copolymer 1b) 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 1c), and 4‐maleimidobenzoic acid (2b) and 3c (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 1a with the isobutyl group showed higher permeabilities than copolymer 1c with the octadecyl group, but no selectivity. The copolymer with the small alkyl group showed no selectivity of oxygen over nitrogen (α = )PO2/PN2 while for the copolymer with the long alkyl chain the α‐value was 1,3.