Polymer nanocomposites (PNCs) hold great promise as future lightweight functional materials processable by additive manufacturing technologies. However, their rapid deployment is hindered by their performance depending strongly on the nanoparticle (NP) spatial organization. Therefore, the ability to control nanoparticle dispersion in the process of PNC preparation is a crucial prerequisite for utilizing their potential in functional composites. We report on the bulk processing technique of tailored NP spatial organization in a model glass forming polymer matrix controlled by structural and kinetic variables of the preparation protocol. Namely, we studied the impact of solvent on the NP arrangement, which was already known as a tuning parameter of the solid-state structure. We emphasized the qualitative differences between "poorly dispersed" NP arrays, which, by combination of rheological assessment and structural analysis (TEM, USAXS), we identified as chain bound clusters and aggregates of either thermodynamic or kinetical origin. They are characterized by substantially distinct formation kinetics and mismatched properties compared to each other and individually dispersed NPs. We quantitatively linked all the currently observed types of NP dispersion with their rheological properties during the solution blending step and the amount of polymer adsorption and depletion attraction. We propose the ratio of NP-polymer and NP-solvent enthalpy of adsorption as a parameter capable of the quantitative prediction of NP arrangement in systems similar to our current model PNC. Finally, we bring forth the comparison of glass transition temperatures to further demonstrate the importance of NP spatial organization in PNCs.

Influence of nanoparticle (NP) spatial organization on relaxation and mechanical properties of polymer nanocomposites (PNCs) was investigated. For the first time, the properties of PNCs with various nanostructures at the constant chemical composition were related to their experimentally determined structural parameterseffective interfacial surface and interparticle distance. Segmental scale reinforcement active below and above glass transition was attributed to the immobilization and frustration of polymer segments caused by attractive polymer−particle interactions. A novel reinforcing mechanism of chain bound clusters related to their internal structure was revealed while negligible reinforcement from NP−NP interactions of contact aggregates was found. The mechanical response of PNCs was correlated with appropriate relaxation properties. It provided the first experimental proof that deformation yielding dynamics of PNCs is controlled by glass transition segmental mobility. Main features of various NP spatial organizations were characterized. Chain bound clusters showed the most significant reinforcement above the glass transition temperature (T g ). Moreover, the hierarchical nature of chain bound clusters caused broadening of the ductile response compared to other nanostructures and also to the neat matrix. The most pronounced enhancement of elastic modulus, yield stress, and creep durability was found for individually dispersed NPs. The acquired nanostructure−property relationships will provide a foundation for the future design of hierarchic and multidomain nanocomposites.

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