PhD Thesis Defense | Isabel Asenjo

SUMMARY

Single-chain nanoparticles (SCNPs) are soft nano-objects obtained by the intramolecular folding of individual polymer chains, offering unique opportunities for tailoring the properties of advanced polymeric materials. This thesis combines theoretical and experimental approaches to investigate the structural and dynamical behavior of SCNPs and SCNP-based all-polymer nanocomposites. The theoretical part extends the Elastic SCNP Model to describe the structure of SCNP brushes, tadpole-shaped nanoparticles, and SCNPs under molecular crowding, establishing predictive scaling relationships for their size and morphology. Experimentally, SCNPs synthesized by copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC) and all-polymer nanocomposites were prepared from hydrogenated and deuterated precursor polymers. Their thermal, mechanical, structural, and dynamical properties were investigated using differential scanning calorimetry, rheology, wide-angle X-ray scattering, and neutron scattering techniques. The results show that intramolecular cross-linking broadens and shifts the glass transition to higher temperatures while preserving the local structural organization. Neutron spectroscopy reveals that local polymer dynamics remain essentially unchanged, whereas segmental motions at intermediate length and time scales become significantly slower and more heterogeneous. Isotopic labeling further demonstrates that SCNPs and matrix chains exhibit distinct dynamical responses in nanocomposites, although these compensate at the macroscopic level. Overall, this work provides new theoretical tools and microscopic experimental insight into the influence of molecular topology and intramolecular cross-linking on polymer structure and dynamics, contributing to the design of functional SCNP-based materials.