Chain Orientation and Polycrystalline Disorder as Antagonistic Descriptors of Thermal and Triboelectric Transport in 3D‐Nanoconfined PMMA, PEEK, and PET Nanowire Networks

ABSTRACT Triboelectric nanogenerators (TENGs) require polymers that dissipate frictional heat while retaining interfacial charge, yet the microstructural rules governing both functions remain unclear, including whether polymer thermal conductivity is governed primarily by crystallinity or by chain orientation and disorder. Here, interconnected 3D anodic alumina (3D‐AAO) templates provide a common nanoconfinement platform for PMMA, PEEK, and PET. 2D‐WAXS reveals amorphous PMMA, PEEK that crystallizes from a fully amorphous bulk to 67.8% crystallinity but remains azimuthally disordered, and strongly oriented PET (Hermans factor ƒ c = 0.915) with a modest crystallinity increase (69.98 → 74.10%). PET reaches the highest effective‐medium‐derived polymer thermal conductivity (1.17 W·m − 1 ·K − 1 ), whereas PEEK shows no resolved thermal enhancement despite its high crystallinity. Amorphous PMMA shows the largest relative thermal‐conductivity increase (+350%), evidencing confinement‐related contributions independent of crystallization. Triboelectricity follows a contrasting trend: polycrystalline PEEK shows the largest relative enhancement (+365%), while PMMA delivers the highest absolute power density (19.71 µW·cm − 2 ). An Efficiency–Orientation Model phenomenologically captures the role of crystalline texture, revealing distinct and potentially competing microstructural descriptors for thermal and triboelectric performance. These results suggest that crystalline texture and disorder, not crystalline fraction alone, should be considered when designing nanoconfined polymers for thermally managed TENGs.