A key challenge during the design of hybrid materials is the development of chemical tools to control the organization of inorganic nanoobjects at low scales, from mesoscopic (~µm) to nanometric (~nm). So far, the most efficient strategy to align assemblies of nanoparticles consists in a bottom-up approach: decorating block copolymer lamellas with nanoobjects. This well accomplished procedure is nonetheless limited by the thermodynamic constraints that govern copolymer assembly: the entropy of mixing as described by the Flory–Huggins solution theory, supplemented by the critical influence of the volume fraction of the block components. Here, we show that a completely different approach can lead to tunable 2D lamellar organization of nanoparticles with solely homopolymers, on condition that few elementary rules are respected: 1) the polymer spontaneously allows a structural preorganization, 2) the polymer owns functional groups that interact with the nanoparticle surface, 3) the nanoparticles show a surface accessible for coordination. Specifically, the results of the present study show that it is possible 1) to generate anisotropic ordering of ultrasmall platinum nanoparticles in lamellar assemblies by simple mixing them with a-helical peptidic homopolymers and 2) to easily tune the dimension of these lamellar assemblies by simply varying the molar mass of the polypeptide. Our result is tentatively explained by the fact that the polymer adopts ordered secondary conformation and that NP/polymer association drives a small amount of polypeptide to adopt a coil disordered state inducing polypeptide demixing with itsef and an anisotropic ordering of NPs. Interestingly, a comprehensive study of the dynamical conductivity of the polypeptide-nanoparticle nanocomposite showed that the physical responses are comparable to the ones of inorganic compounds, but with the flexibility afforded by the polymer and nanoparticle chemistries.

Nanocomposites through self-organized layers of polypeptides coupled to platinum nanoparticles

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