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Arrangement of Nanoparticles in Phase Separated Systems

Final Activity Report Summary - ANAPHASES (Arrangement of nanoparticles in phase separated systems)

The general objective of this project was to develop new advanced materials through the control in the distribution of nanoparticles (NPs) in polymer networks.

Final properties of materials composed by NPs and polymers (nanocomposites) strongly rely on the way in which NPs are spatially distributed. Materials with completely different performance can be obtained by distributing the same amount of NPs in different ways (for example, inducing the formation of clusters formed by many NPs instead of distributing them homogeneously).

To control the arrangement of NPs in the polymer we used special modifiers (polymers, crystalline solids, micelles, etc.) which can form phases with a special affinity by the nanostructures. In the course of the project, several strategies were used and analysed with the final objective of improving our ability as 'designers' of nanocomposites with special properties. We tested non-conventional strategies of compatibilisation and control of the aggregation level that enabled the synthesis of materials with interesting optical and magnetic properties. We also worked on new and simple synthetic procedures to obtain metal NPs with different morphologies and sizes.

The most important achievements of the work performed are summarised below:
-Different arrangements of magnetic iron oxide NPs were obtained using different polymers as matrices. Using a polymer with a high affinity by the coating of the NPs, homogeneous systems could be obtained. On the other hand, by using a less compatible and semicrystalline polymer, small clusters of NPs were formed in the continuous matrix. Both systems showed a completely different magnetic behaviour at room temperature, which demonstrated the importance of aggregation on the final properties of nanocomposites. The well dispersed nanocomposites were used as model systems for the study of the variation of the magnetic properties with the concentration and to contrast theoretical predictions with real experiments. A clear understanding of these aspects is fundamental for prediction and tuning of final magnetic properties and for the design of new magnetic materials.
-A new method to obtain gold and silver NPs was developed based on simple mixing and heating of a water soluble, non-toxic polymer, (polyvinylpyrrolidone, PVP) a metal salt and water. The origin of the NPs formation was elucidated by careful analysis of the synthesis process. This enabled us to design new strategies to conduct the process towards the formation of different structures (polyhedral NPs and polygonal and branched plates) which present characteristic properties with potential applications in different fields (sensing, optics, electronic, etc.).
-Monoliths and films consisting of an epoxy network modified with metal NPs could be prepared using a simple strategy based on the high compatibility between PVP and an epoxy monomer (DGEBA). Changing the type of NPs, materials with different colours and high optical quality could be obtained, with interesting potential applications in optical devices.
-A new multifunctional amphiphilic copolymer was synthesised and used to obtain metal nanocomposites with different morphologies. This copolymer could be used to homogeneously distribute hydrophobic NPs in hydrophilic matrices, to segregate the NPs to hydrophobic domains dispersed in a continuous matrix and to form thermoreversible networks modified by 'crystalline' arrangements of NPs. The versatility of this modifier makes them very promising as a tool for the development of new advanced materials.
-Metal NPs were included in silicon elastomers using a novel approach based on the modification of this type of polymer with micelles. These micelles acted as nanoreactors in which NPs could be synthesised previously to the formation of the network. The obtained materials showed a high optical quality and an optical response that could be tuned by simple changes in the composition of the initial system.