Abstract

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.

Highlights

  • The sequential layer-by-layer (LbL) assembly is one of the most facile and versatile techniques for thin-film fabrication.[1−3]It is normally based on electrostatic interactions between the components but, for example, hydrogen bonding, coordination or covalent bonding, host−guest, charge transfer, and biological interactions have been used

  • A widely used technique is based on the measurement of the energy dissipation of a quartz crystal resonators (QCRs) microbalance covered with a film (QCM-D).[30−32] On the other hand, we have shown that the measurement of the local acoustic impedance on the film/resonator interface (ζ0) is an excellent model-independent method for the characterization of the viscoelastic properties of growing films.[9,10,33−35] The local acoustic impedance is a complex quantity (ζ0 = ζ0′ + jζ0′′), which is given in units of Rayls (1 Rayl = 1 kg m−2 s−1)

  • We show that replacing every second PP layer in a (PP/Ce) multilayer with Graphene oxide (GO) sheets enhances the film growth in dip-LbL

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Summary

Introduction

The sequential layer-by-layer (LbL) assembly is one of the most facile and versatile techniques for thin-film fabrication.[1−3]It is normally based on electrostatic interactions between the components but, for example, hydrogen bonding, coordination or covalent bonding, host−guest, charge transfer, and biological interactions have been used.

Results
Conclusion

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