Dispersion-Driven Interphase Engineering and Quantitative Stress Transfer in Chemically Inert PTFE/MWCNT Nanocomposites

Abstract

Interphase engineering in chemically inert polymer nanocomposites remains fundamentally unresolved due to the difficulty of decoupling physical confinement effects from chemical functionalization. Here, we establish a quantitative dispersion–interphase–structure framework using non-functionalized PTFE/MWCNT nanocomposites as a model inert system. By systematically varying nanotube loading (10:1–10:4 PTFE:MWCNT), we isolate dispersion-driven physical interactions in the complete absence of covalent bonding. Raman spectroscopy reveals a monotonic reduction in ID/IG (1.08–0.97) and a reproducible G-band upshift (~6 cm⁻¹), corresponding to an estimated interfacial strain of ~0.22%, providing evidence of measurable stress transfer primarily arising from physical confinement. X-ray diffraction coupled with FWHM and Scherrer analysis demonstrates crystallite enlargement at intermediate loadings, while DSC-based crystallinity calculations identify a maximum relative crystallinity at 10:2 composition. At higher nanotube loading, partial re-agglomeration and confinement-dominated restriction reduce crystalline ordering despite elevated melting temperature (328–334 °C). These results suggest that dispersion plays a significant role as a thermodynamic regulator of interphase evolution in fluoropolymer nanocomposites. This work provides insight into the underlying mechanisms of stress transfer and crystallization behavior in chemically inert CNT/polymer systems and establishes a rational strategy for interphase engineering without chemical modification.