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Dynamics of Soft Metallo-Supramolecular Materials from Entangled Macromolecular Precursors

Final Report Summary - SUPRA-DYN (Dynamics of Soft Metallo-Supramolecular Materials from Entangled Macromolecular Precursors)

The project SUPRA-DYN has focused on some recent research topics in soft matter science, for which 'small external stimuli yield large changes in the material' as described by P.-G. de Gennes. By using thermo-mechanical stimuli mainly as a probe and different chemical and electromagnetic stimuli, e.g. ions, light, or temperature, as external triggers the influence of changing environmental conditions on polymeric as well as 'smart materials' with supramolecular bonds and functionalised components has been investigated (cf.the schematic). Several studies on industrial or academic relevant materials and topics, e.g. for biomedical or electronic applications, were conducted by a plury-disciplinary approach involving many different disciplines like experimental physics and synthetic chemistry, materials science and engineering or molecular theory and modelling (cf. the schematic). Such overlap is important to examine and resolve processing or performance related questions, e.g. regarding stimuli-responsiveness, durability or self-healing properties.

A major focus was on new model materials from covalent polymer precursors with metallo-supramolecular telechelic groups since very little is understood so far about the influence of metal-ligand interactions on such accordingly obtained gels. Furthermore, functional and smart materials with supramolecular interactions, e.g. nanocomposites from polyethylene with carbon-nanotubes, pressure-sensitive adhesives as well as biomedically relevant polymeric or hydrogels were investigated. The systems are already comprised of complex architectures due to their composition, molecular structure, morphology, crystallinity or ionic interactions, but for reactive systems the viscoelastic response can also change relatively fast with time due to environmental conditions and hence add further to the complexity.

Main objectives were the advanced and combined experimental analysis for rheological and molecular characterisation of soft matter materials as well as their connection to molecular dynamics and modelling. The combinations of rheology and dielectric spectroscopy as well as X-ray scattering were mainly employed, but also size-exclusion chromatography, thermal analysis and calorimetry, as well as nuclear magnetic resonance methods.

Major achievements were the advanced characterisation and analysis of the material response and dynamics in the broadest possible ranges of time, temperature, or deformation rate for structural and thermo-rheological complex materials. This needed to be reliably examined in detail and at various length scales, especially for modelling efforts. Recent molecular models like the tube-theory have been able to describe the dynamics of specific and well-defined polymer systems quite well, but the properties of complex polymeric systems, e.g. biomaterials with polar groups or hydrogen bonds, highlighted the strong influence from supramolecular interactions and assemblies. Such supramolecular systems show additional and much slower relaxation mechanisms in comparison to classical polymer dynamics. They have been observed to have very wide range dynamics and to be very sensitive to external stimuli such as temperature and deformation. These effects lead to a non-trivial material behaviour with liquid to solid gel characteristics and require detailed studies on gelation kinetics regarding structure-property relations and thermo-mechanical properties for various applications, e.g. bio- and hydrogels, photo-sensitive materials, electro-rheological fluids and materials.

The involvement with other European research or training initiatives was very beneficial and has been possible due to close collabourations and international exchanges with outstanding experts or research groups in the field of materials characterisation, molecular modelling, organic synthesis and polymer engineering. The largest and most prominent examples are the SOFTCOMP Network of Excellence on softmatter composites (see http://www.eu-softcomp.net for details), the DYNACOP Initial Training Network on dynamics of architecturally complex polymers (see http://eudoxus.leeds.ac.uk/dynacop for details), and the 'Eurheo' programme as European Masters in engineering rheology (see http://eurheo.eu for details).

The results of this project are expected to have a wider impact and importance for industry and institutions working on new recyclable materials with well-designed properties. The information are beneficial in order to resolve the increasing need for environmentally friendly and energy saving solutions that Europe needs to progress using biomaterials while reducing materials consumption and increasing recycling rate to become greener.

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