A study of proton diffusion across membranes of block copolymer vesicles in dilute solution is described. The vesicles were formed by the self-assembly of a diblock copolymer of @entity58231 (PS(310)-b- @entity3880 (36), where the numbers represent the degree of polymerization for individual blocks). A pH gradient was created across the vesicle membrane with the interior pH (pH(in)) of ca. 2.9 and the exterior pH (pH(out)) of ca. 8.5. The permeability of the @entity852 (PS) membrane was tuned by the addition of different amounts of @entity6246 (0-40 wt %) to the external aqueous solution. Proton concentrations in the solution outside of the vesicles were followed by monitoring the spectrum of a pH-sensitive fluorescent dye, namely @entity18855 . After the start of the experiment, the proton concentrations increase linearly with the square root of time, while the slopes of the lines increase with @entity6246 content. To calculate the diffusion coefficients of the protons across the vesicular membrane, the concentration data were fitted using a model, which describes the diffusion of species across the membrane of a reservoir. The apparent diffusion coefficient (D*, which equals the true diffusion coefficient multiplied by the partition coefficient of protons between PS and water) increases from 1.1 x 10(-18) cm(2)/s at 7 wt % @entity6246 in the external solution to 1.2 x 10(-14) cm(2)/s at 40 wt %. The increase of D* with @entity6246 content is related to its plasticization of the PS membrane, which can be used as a gating mechanism.

Proton diffusion across membranes of vesicles of XXXX diblock copolymers.

@entity852 :: ('MESH:D011137', 'Chemical') :: ['polystyrene'] @entity3880 :: ('CHEBI:51133', 'Chemical') :: ['PAA'] @entity18855 :: ('MESH:C005047', 'Chemical') :: ['8-hydroxypyrene-1,3,6-trisulfonate'] @entity6246 :: ('MESH:C025223', 'Chemical') :: ['dioxane'] @entity58231 :: ('MESH:C509855', 'Chemical') :: ['poly(styrene-b-acrylic acid)']
@entity58231 :: (MESH:C509855,Chemical) :: ['poly(styrene-b-acrylic acid)']
