Engineered Nanocomposites Through Embedding of Smaller “Organic Inorganic” Nanoparticles in Thermoplastic Poly(2-Vinylpyridine) Polymer Matrix

Polymer nanocomposites (PNCs) are significant for modern and future applications owing to their multifunctionality promoted by morphology and tailored interfaces between the constituents. However, ‘forward’ engineered polymer (host) composites with smaller size nanoparticles (guest) providing desired properties remain challenging as they depend upon nanoparticle aggregation, size, shape, and loading (volume or weight) fraction. This study strategically designs and develops PNCs comprising thermoplastic poly(2-vinyl pyridine) (P2VP) polymer matrix impregnated with spherical polyhedral oligomeric silsesquioxane (N-POSS) nanoparticles (diameter ~2-5 nm) and anisotropic planar nitrogenated graphene nanoribbons (GNR, strip width ~5-10 nm) commensurate with polymer chain radius of gyration, R_g, (or segment length ~1.5 nm) and comparable energy scales of electrostatic interaction and attractive hydrogen bonding. We investigated the static and dynamic structure and thermophysical properties to correlate with interfacial regions and the results are compared with larger graphene oxide (GO, lateral dimension ~100-200 nm) nanosheets and silica (SiO₂, ~25-50 nm) particles. While electron microscopy revealed nanoparticle distribution, the lattice bonding, conjugation length, and mechanical properties were determined from micro-Raman spectroscopy and atomic force microscopy, respectively. The differential scanning calorimetry provided a measure of the glass transition temperature, T_g, with a positive shift of ~10-18 ^oC with nanoparticles loading indicating the strength of structural relaxation/chain rigidity behavior and thermogravimetric analysis displayed increased thermal stability and conductivity (decreased interfacial resistance). We also measured temperature-dependent dc electrical conductivity and dielectric relaxation spectroscopy gaining insights into percolation and dynamic interfacial layer. This study signified an understanding of interactions and interfacial regions, key elements to demystify the microscopic structure-property relationships.