Smart Optical Films: Controlling the optical properties of nanostructured oxide-based polymer films

Dr Stavros Christopoulos

Associate Professor of Physics, SUAD

The need for developing environmentally friendly materials with profound new properties is continuous. The utilization of nanoparticles in the fabrication of new materials has increased rapidly in recent years due to their unique physical and chemical properties. Nanoparticles of different size, shape and concentration have been employed to improve or even completely modify the properties of the dispersing medium. For the latter, the use of polymer matrices has been a well-established approach towards the fabrication of advanced materials with highly desirable properties. These have been widely utilized in various sectors of everyday life and industry such as agriculture, construction, screen/TV technology, photography, etc.

The project aims in the production of smart films combining a number of properties of the hosting polymer with significant improvements stemming from their mixing with nanoparticles. We here embed combinations of thermodynamically treated metal-oxide nanoparticles in various formations and stoichiometry inside a polymer matrix of choice, in order to create films, which will be specifically customized to fit a great number of industrial and everyday life applications. These include but are not limited to greenhouse covers, anti-glaring and/or anti-reflection coatings for glass surfaces, flat control displays and optical elements, etc. Furthermore, their extremely low fabrication cost is expected to become a competitive advantage.

A pool of different oxides (ZnO, SiO2, Al2O3, WO3, TiO2 and others) have been considered due to their optical properties. The nanoparticles, comprising single and mixed oxides, are initially coated with PAA and are subsequently milled, freeze-granulated and freeze-dried. The process is finalized by embedding them into a polymer matrix of choice (i.e. LDPE) through a bulk-scale extrusion process. The end-products are polymer films with advanced physical properties, virtue of the successful mixing of the incorporated materials. At the final stage, a wide-range optical characterization of the end-material allows for verifying homogeneity and an accurate parametrization tuning. The mixing with a variety of biodegradable polymer matrices such as polylactic acid (PLA), polycaprolactone (PCL), polyglycolic acid (PGA), polyhydroxybutyrate (PHB) is currently our main objective.

Furthermore, we are developing a theoretical approach, at the microscopic level, to reveal the physico-chemical aspects behind the experimental results as well as the different mechanisms involved. The model is focusing on the role of the polymer, the size of nanoparticles, their distribution and concentration over the polymer, as well as the inter-particle dynamics within the encompassing environment, aiming to optimize the samples under investigation.