Modification of the Optoelectronic Properties of Membranes via Insertion of Amphiphilic Phenylenevinylene Oligoelectrolytes

We report on the modification of membranes by incorporation of phenylenevinylene oligoelectrolytes with the goal of tailoring their optical and electronic properties and their applications. A water-soluble distyrylstilbene oligoelectrolyte (DSSN+), capped at each end with nitrogen bound, terminally charged pendant groups, was synthesized. The photophysical and solvatochromatic properties of DSSN+ and the shorter distyrylbenzene analogue DSBN+ were probed and found to be useful for characterizing insertion into membranes based on phospholipid vesicle systems. A combination of UV/visible absorbance and photoluminescence spectroscopies, together with confocal microscopy, were employed to confirm membrane incorporation. Examination of the emission intensity profile in stationary multilamellar vesicles obtained with a polarized excitation source provides insight into the orientation of these chromophores within lipid bilayers and indicates that these molecules are highly ordered, such that the hydrophobic electronically delocalized region positions within the inner membrane with the long molecular axis perpendicular to the bilayer plane. Cyclic voltammetry experiments provide evidence that DSSN+ and DSBN+ facilitate transmembrane electron transport across lipid bilayers supported on glassy carbon electrodes. Additionally, the interaction with living microorganisms was probed. Fluorescence imaging indicates that DSSN+ and DSBN+ preferentially accumulate within cell membranes. Furthermore, notable increases in yeast microbial fuel cell performance were observed when employing DSSN+ as the electron transport mediator.