PERMEABILITY AND PARTITIONING OF FERROCENE ETHYLENE-OXIDE AND PROPYLENE-OXIDE OLIGOMERS INTO ELECTROPOLYMERIZED FILMS FROM ACETONITRILE ANDPOLYETHER SOLUTIONS

We report the first electrochemically-based measurements of the rates of small polymer permeation into another polymer. The small polymer pe rmeants are ferrocene ethylene oxide oligomers containing 2, 7, and 16 units and a propylene oxide oligomer containing 3 units. Their permea tion into ultrathin microelectrode-supported films of the metal comple x polymer poly[Ru(vbpy)(3)](ClO4)(2) was measured from acetonitrile so lutions and from solutions in a methyl-endcapped ethylene oxide oligom er, MPEG-400 (MW = 400). Permeations of other ferrocenes with bulky su bstituents were also measured from acetonitrile solutions. In ah cases the permeability, PDPOL, into poly[Ru(vbpy)(3)](ClO4)(2) films is str ongly dependent on the permeant molecular volume. Direct measurement o f the partition coefficient, P, in acetonitrile shows that permeabilit y variations among a series of related permeants are controlled more b y variations in P than by diffusivity in the poly[Ru(vbpy)(3)](ClO4)(2 ) phase. Permeation of ferrocene polyether oligomers is much slower fr om MPEG-400 solutions than from acetonitrile; this appears to arise mo re from a decrease in D-POL than from one in P.