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Controlling the Order of Functional Polymers and Their Corresponding Blends

Final Report Summary - CONDPOLYBLENDORD (Controlling the Order of Functional Polymers and Their Corresponding Blends.)

Products made of polymers – “plastics” – are ubiquitous in our daily lives. Polymers such as polyethylene (PE), polypropylene (PP), or poly(ethylene terephthalate) (PET) have developed into multi-billion dollar markets since their discovery some 60 years ago. Surprisingly, however, a number of important aspects of these interesting and versatile materials are not well understood. For example, it is essentially impossible to control the crystallization of the simplest “plastic” – PE (made of linear chains of carbon) – and is considered a holy grail for the polymer community because it would allow, one to control the physical appearance of this material from white/opaque to fully transparent. In this example, controlling the molecular ordering of polyethylene is of great interest because objects could be fabricated at low cost that are both transparent and mechanically tough, which is more attractive than using alternate 
materials such as the clear, but very brittle amorphous polystyrene (PS).

Throughout history, the concept of adding small quantities of “additives” has been exploited to manipulate the solid-state structure and properties of materials (e.g. steel). More recently, the topic of organic semiconductors has garnered significant popular and scientific interested due to their potential for improved device performance (e.g. improved color saturation in organic light-emitting diodes) with reduced manufacturing costs (e.g. through solution processing). CONDPOLYBLENDORD utilized the well-known concept of additives to address one of the grand challenges in the organic semiconductors - controlling the physical organization of organic semiconductors. With this project, we wanted to relate molecular order and conformational arrangements to organic conjugate matter with electronic, magnetic and optical phenomena, and aim at developing understanding similar to the polymer mechanics field, where such knowledge led to the development of ultra-high strength polymer fibres, for use in bullet-proof gear as well as superb medical instruments.

The approach advanced by CONDPOLYBLENDORD applies a strategy widely exploited in classical polymer systems to new material systems, i.e. organic semiconductors. This approach involves the addition of a high surface area additives, which increase the volume of nucleation sites within the host material, and, as a result, control the host material’s crystallite size. Thus, due to its simplicity and versatility, our findings have begun to catalyze further studies in organic semiconductors by device engineers (e.g. developing processing protocols) and to physicists (e.g. understanding microstructure/charge transport relationships). Other potential applications within this area include the use of nucleation agents to control the phase morphologies of active layers in organic photovoltaic cells, where a fine distribution of the active components is believed to be beneficial. In principle, nucleation agents control the size of the crystalline domains in such materials, which enable exploitation of these additives for the production of photonics structures, and also more fundamental studies including elucidation of the influence of grain boundaries on charge transport in organic semiconductors.

CONDPOLYBLENDORD has truly underlined the importance of converging research, technology, and innovation to further assist in the transformation of the polymer industry from commodities towards life-changing products and actively integrate them in the EU’s PV sector. I aimed to contribute to the fundamental knowledge of semiconducting polymers and their corresponding blends by controlling the morphology within these systems using nucleating agents – an approach that had not be investigated and utilized in semiconducting polymers and their corresponding blends before the start of CONDPOLYBLENDORD. Controlling the nano-morphology of conducting polymers and their blends is still essential for the further development in the field of organic electronics. Thus CONDPOLYBLENDORD was designed to significantly contribute to the European organic electronic research and industry sector by advancing the understanding of how to control the morphology of polymer-fullerene blends. I also attempted with the project to harness the rich, interdisciplinary expertise in chemistry, engineering and physics, which has permitted me to gain a better understanding of the requirements for nucleation and allowed me to design new materials that, eventually, may lead to the development of new opportunities that make straight- forward, large-area specialty products possible and, thus, will strengthen Europe’s long-standing position in manufacturing.