Layer-by-layer (LbL) fabricated oxidative multilayers consisting of
successive layers of inorganic polyphosphate (PP) and Ce(IV) can
electrolessly form thin conducting polymer films on their surface. We
describe the effect of substituting every second PP layer in the (PP/Ce)
multilayers for graphene oxide (GO) as a means of modifying the
structure and mechanical properties of these (GO/Ce/PP/Ce) films and
enhancing their growth. Both types of LbL films are based on reversible
coordinative bonding between the metal ions and the oxygen-bearing
groups in PP and GO, instead of purely electrostatic interactions. The
GO incorporation leads to the doubling of the areal mass density and to a
dry film thickness close to 300 nm after 4 (GO/Ce/PP/Ce) tetralayers.
The film roughness increases significantly with thickness. The (PP/Ce)
films are soft materials with approximately equal shear storage and loss
moduli, but the incorporation of GO doubles the storage modulus. PP
displays a marked terminating layer effect and practically eliminates
mechanical losses, making the (GO/Ce/PP/Ce) films almost pure soft
elastomers. The smoothness of the (PP/Ce) films and the PP-termination
effects are attributed to the reversible coordinative bonding. The
(GO/Ce/PP/Ce) films oxidize pyrrole and 3,4-ethylenedioxythiophene
(EDOT) and form polypyrrole and PEDOT films on their surfaces. These
polymer films are considerably thicker than those formed using the
(PP/Ce) multilayers with the same nominal amount of cerium layers. The
GO sheets interfere with the polymerization reaction and make its
kinetics biphasic. The (GO/Ce) multilayers without PP are brittle and
thin.