Viscosity-Dependent Nanoparticle Diffusion in PEEK Matrices: How Preparation Route Determines Thermal Property Outcomes and Manufacturing Scalability

Engineering polymer nanocomposites for high-temperature and high-power applications requires a rigorous understanding of how processing-induced rheological conditions govern nanoparticle diffusion, dispersion kinetics, and ultimately thermal performance in semi-crystalline matrices such as polyether ether ketone (PEEK). At a broader scale, viscosity-controlled transport phenomena dictate the formation of percolative thermal pathways, interfacial phonon coupling, and crystallization behavior, all of which are critical for applications in semiconductor packaging and energy systems operating under extreme conditions. This study provides a mechanistic evaluation of viscosity-dependent nanoparticle diffusion in PEEK matrices, emphasizing how preparation routes including melt compounding, solution casting, and in situ polymerization modulate particle mobility, shear-induced alignment, and agglomeration dynamics. The analysis integrates diffusion theory with non-Newtonian rheology, demonstrating that elevated melt viscosity restricts Brownian motion while promoting shear-driven dispersion, leading to anisotropic microstructures with direction-dependent thermal conductivity. Furthermore, interfacial interactions between nanoparticles and PEEK chains are shown to influence crystallization kinetics, altering lamellar thickness and thermal stability. By correlating diffusion regimes with processing conditions, this work establishes a predictive framework linking manufacturing scalability to thermal property optimization, enabling rational design of high-performance PEEK nanocomposites.