PTFE-based core-shell nanoparticles: a possible way towards the assembly of ordered soft-matter layers with tuneable (photonic) properties

The assembly of ordered arrangements of nanoparticles can represent a route towards the preparation of materials with innovative physical properties stemming from the characteristics of the nanoparticles themselves and from the controlled interactions amongst them. Composite materials could exhibit interesting photonic properties if different components are spaced regularly in its bulk: the controlled 2D or 3D assembly of core-shell polymer nanoparticles results in such a regular spacing of the core material. The possibility of controlling the size of the core and the thickness of the shell represents a viable route towards the design of photonic properties towards the realization of nanostructured polymer opals. PTFE latexes can be obtained with a narrow nanoparticle size distribution. Around such seeds, we could grow shells made of different types of polymers or copolymers that will quantitatively coat the dispersed PTFE seeds. A control of the shell thickness can be obtained by varying the ratio between seed and shell monomer(s). A careful choice of monomers can lead to water-soluble core-shell nanoparticles with markedly different properties. For instance the shell can swell in water (and respond to pH changes) or, alternatively be quite rigid and insensitive to the environment. The comonomers mix will lead to shells with markedly different thermal properties. In this communication, we report our success in preparing and characterizing a variety of different PTFE-based core-shell systems with shells made with comonomers mixtures such as methylacrylate, ethylacrylate and methacrilic acid, or butylacrylate and methacrilic acid, or simply with methylmethacrylate [1,2]. Such core-shell nanoparticles have been then used to make ordered layers that have been characterized by atomic force microscopy [3]. The success in the preparation of these core-shell systems might lead to materials that could exhibit the valuable properties of PTFE while reducing some of its disadvantages, such as its compatibility with other materials (adhesion and wettability). In the near future we will be investigating the possible applications and photonic properties of such regularly arrange nanoparticulate systems.