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Abstract

Natural materials are composed of a limited number of molecular building blocks, e.g. amino acids, carbohydrates), and their exceptional properties are governed by their intricate hierarchical structure on multiple length scales. While 3D printing has emerged as the standard method for the precise fabrication of minute devices, this level of precision is unattainable with current state-of-the-art materials for 3D printing. A common method of obtaining such nanoscale structure in systematic systems exploits the potential for polymers to self-assemble under certain conditions. One important class of polymers which has the ability to form self-assembled structures at a scale of 5- 50 nm are amphiphilic block copolymers. They are tunable over a broad variety of morphologies, ranging from micelles and vesicles to continuous network structures, which can form in both undiluted melt or solution. While these properties have been extensively investigated in 2D films, they have not yet been exploited to generate 3D structures entailing high resolution features, complex geometries and a controlled nanostructure. To that end, in the current PhD thesis, new self-assembled printable materials based on block copolymers (BCPs) that enable precise control of the nanostructure in 3D are investigated. In particular, well-defined BCPs consisting of a poly(styrene) block and a poly(methacrylate)-based copolymer decorated with printable units are selected as suitable self-assembling materials. A broad library of BCPs with different compositions and molecular weight is synthesized using controlled radical polymerization. A subsequent extensive investigation of the phase behavior before and after the functionalization is performed using SAXS, SEM, and SNOM. Lamellar, cylindrical and gyroid morphologies are observed dependent on the composition as well as the molecular weight, allowing the phase diagram of the system to be generated. The dependency of the domain spacing d on the molecular weight of the polymer is found to be described by a power law, which is in accordance with that published for other systems both experimentally as well as in theory. The synthesized library of BCPs is then utilized to create printable formulations for the fabrication of complex 3D microstructures using two-photon laser printing. By fine-tuning the BCP composition and solvent in the formulations, the fabrication of precise 3D nano-ordered structures is demonstrated for the first time. Hereby, the key achievement is a controlled nano-order within the entirety of the 3D structures. To show this, imaging of the cross-sections of the 3D printed samples is performed, enabling visualization also from the inside. A detailed view of both lamellar as well as cylindrical morphology, dependent on the polymer design, is presented. The morphologies are fitting well with those found in the respective bulk polymer analysis, as well as SAXS measurements of the printing ink formulation.