Premix‐Driven Interfacial Assembly and Morphological Inheritance in Cs x WO 3 /Polymer Nanocomposites for NIR Blocking and High Visible Transparency

The construction of high‐quality inorganic/organic functional premixes is a critical prerequisite for fabricating high‐performance spectrally selective films. In this study, Cs x WO 3 nanoparticle premixes were constructed using high‐speed shear and planetary medium‐low speed stirring processes across three matrices with gradient polarities, non‐polar PE, weakly polar EVA, and strongly polar PET. Quantitative spectral analysis revealed a distinct “Polarity‐Matching” dispersion mechanism. In the PE system, the high‐speed shear processes a film with an optimal near‐infrared (NIR) blocking rate of ~73% but a limited visible light transmittance (T vis ) of ~52% due to “island‐like” agglomeration, whereas the medium‐low speed process failed to achieve effective dispersion, indicating a reliance on high‐intensity mechanical shear. In the EVA system, high‐speed shearing achieved a T vis of ~61% with an NIR blocking rate of ~64%; notably, the optimized medium‐low speed planetary stirring (at 45°C) significantly improved T vis to ~73% (with ~60% NIR blocking). Most notably, the PET system utilizing ethyl acetate‐based slurry established a robust “chemical anchoring” effect, endowing the premix with thermodynamic stability and allowing the PET film to maintain superior performance under both high‐speed (T vis ~82%, NIR blocking ~78%) and low‐energy ambient planetary stirring (T vis ~79%, NIR blocking ~84%) processes. This work reveals that the dependence on mechanical shear force decreases significantly as matrix polarity increases. This insight validates the feasibility of replacing energy‐intensive shear with thermodynamic regulation in polar systems, thereby providing critical guidelines for the low‐cost, scalable manufacturing of transparent heat‐insulating materials.