ELECTRIC-FIELD-INDUCED PERMEABILITY MODULATION IN PURE AND MIXED LANGMUIR-BLODGETT MULTILAYERS OF HEMICYANINE DYES AND OCTADECANOIC ACID ONNANOPOROUS SOLID SUPPORTS
Jk. Steehler et al., ELECTRIC-FIELD-INDUCED PERMEABILITY MODULATION IN PURE AND MIXED LANGMUIR-BLODGETT MULTILAYERS OF HEMICYANINE DYES AND OCTADECANOIC ACID ONNANOPOROUS SOLID SUPPORTS, Journal of membrane science, 139(2), 1998, pp. 243-257
Composite structures have been prepared, in which nanoporous (nuclear
track-etched) membranes are coated with supported Langmuir-Blodgett (L
B) barrier layers. Permeability in these structures is a strong functi
on of membrane composition and applied rte and ac electric fields. Abs
olute permeabilities fall in the range 3x10(-11) cm(2) s(-1) less than
or equal to P less than or equal to 3x10(-9) cm(2) s(-1), depending o
n composition of the barrier layer, identity (charge state) of the pro
be, and presence of a supporting electrolyte. Zero-field permeabilitie
s showed a definite dependence on composition, with membranes possessi
ng barrier layers on both sides performing better than single-sided me
mbranes, barrier layers with LB multilayers performing better than tho
se with just the support layer, and LB layers composed of mixed stilba
zolium amphiphiles and octadecanoic acid performing better than those
composed purely of stilbazolium amphiphile. All types of barrier layer
s studied exhibit permeability changes in the presence of applied elec
tric fields. The magnitude of the effect is a strong function of compo
sition of the barrier layer and the presence of supporting electrolyte
. The results support electroporation over iontophoresis as the domina
nt mechanism for field-mediated increases in permeability. Details of
the field-induced permeability changes in phosphate buffer and deioniz
ed water suggest that at least two effects are important in determinin
g the transport behavior in these structures: a field-induced structur
al change in the barrier layer which mediates the electroporation and
a field-mediated alteration in transport through nanopores of the nucl
ear track-etched membrane. (C) 1998 Elsevier Science B.V.