Inorganic nanoparticle/polymer composites present an interesting class of materials that pair the beneficial mechanical characteristics of organic polymers with the unique optical, electrical, magnetic, and chemical behaviors of inorganic nanocrystals. Management of the physical properties of these composites, however, requires control over both the composition of the two phases, as well as their relative positions in three dimensions. While top-down processing techniques currently present limited ability to regulate nanoscale geometry in these composites, supramolecular chemistry driven self-assembly is potentially a powerful new means to achieve ordering across different length scales, as it uses individual molecular interactions to direct the formation of hierarchical structures. Here, we introduce a unique class of nanocomposite building blocks dubbed “nanocomposite tectons” (NCTs), which use supramolecular chemistry to dictate nanoscale ordering in polymer-nanoparticle composites. NCTs consist of nanoparticles with densely grafted polymer brushes, where each brush terminates in a simple biomimetic hydrogen bonding motif. In this initial work, these programmed molecular interactions create reversible bonds between individual NCTs, where the strength of these bonds can be easily tuned as a function of the larger scale geometry of the particles (e.g. particle size, polymer length). Ordered arrays of particles can therefore be generated by modulating the sample temperature to allow for NCT crystallization into superlattice architectures. As a result, NCTs exhibit hierarchical structuring, where collective molecular interactions enable the formation of ordered nanoscale particle arrays, and the nanoscale geometry of individual particles manipulate the thermodynamic strength of these molecular interactions. As a result, NCTs can be used to precisely manipulate nanocomposite structure across multiple length scales by design, introducing new opportunities for both the development of functional materials and fundamental explorations of supramolecular chemistry driven assembly behaviors.

Using nanoscale geometry to dictate molecular behavior in inorganic nanoparticle composites

255th National Meeting (2018)

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