Anagrafe della ricerca

With special respect to recent development needs in the areas of micro-electronics and electromagnetic shield-ing, which have the common feature of required complex and hardly accessible (gradient) structures, the concepts of photoresist design and frontal polymerization will be jointly implemented in this strategic project. With respect to photoresists, the project will focus on photopolymers (and the corresponding magnetic compo-sites) of the polymer classes including (i) silicones that have very low water uptake (to be crosslinked via UV-induced hydrosilylation reactions), (ii) poly(benzoxazine)s, (iii) bismaleimides, (iv) PBO/DNQ sys-tems, and (v) poly(methacrylate)s. These photoresists/composites will be designed such that, after the exposure/development step, no or at least significantly lowered solubility of the polymers and corresponding composites occurs. Frontal polymerizations/crosslinking reactions differ significantly from ‘conventional’ (thermally induced) polymerizations/crosslinking reactions, in which the reactions take place after the mixing of the reactants and heating. Polymerizations/crosslinking reactions in the course of frontal polymerizations are started by a switcha-ble stimulus, such as irradiation with UV light. During the cross-linking of the resin, heat is released, which in turn acts as a switch for the cross-linking of the reactants in adjacent areas. Thus, a polymerization front that travels through the resin can be started at a chosen point of time, resulting in uniform network formation. The frontal polymerization technique will be expanded to the curing of (magnetic) composites in this strategic project. For the curing of such composites, (significantly) enhanced thermal conductivity (in comparison to the respective unfilled resins) must be considered. The detailed investigation of this phenomenon (in par-ticular in the case of composites with high filling degrees of (inorganic) particles) is still in its infancy; the detailed compilation of fundamental data and their subsequent usage in Modelling & Simulation routines enabling the prediction of successful performance of the polymerizations is one of the priority targets in this strategic pro-ject. The experimental work will be combined with simulation and modelling in order to determine the best-suited initiators/catalysts and their combinations, as well as the minimum volume / surface ratio that enables progression of the frontal polymerization. An additional benefit of using frontal polymerizations for the manufacturing of electromagnetic shielding materi-als is the possibility to prepare gradient composites with spatial resolution of the shielding characteristics: func-tional gradient materials can be prepared in a straightforward fashion as the composition of a monomer feed-stream (e.g., varying content of particles and/or change of the filler material) can be varied in a programmable manner. In an advanced stage of this strategic project, the best-suited polymers will be used for the produc-tion of composite materials (with commercially available as well as functionalized inorganic particles) in order to fulfill the additional requirements of reduced shrinkage (negative photoresists containing oligocyclic mono-mers), thermal conductivity, and thermal expansion.