Fluorophilic interaction-directed crystallization control in PVDF via ultralow fluorinated organic molecule

Poly(vinylidene fluoride) (PVDF) is a prominent fluoropolymer whose functional properties are governed by its polymorphic crystal structure. Conventional strategies for controlling PVDF crystallization face challenges in achieving precise, multi-scale control over molecular chain conformation, segment orientation, crystal phase, and crystallinity, hindering the simultaneous optimization of high polar β-phase content, low dielectric loss, and mechanical toughness. Here we introduce a crystallization control strategy utilizing trace fluorinated organic molecules (FOM) as additives. This approach exploits strong C-F···H-C intermolecular interactions between FOM and PVDF chains to both induce the formation of all-trans (TTTT) chain conformation and directionally guide crystalline architecture through fluorine-induced dipole alignment. At an ultralow FOM loading of 0.5 wt%, this strategy significantly enhances crystallinity and boosts the β-phase fraction from 27 % to 77 %. The resulting molecular-scale dipole orientation enables a maximum polarization (P_max) exceeding 9.1 μC·cm^-2. Crucially, the FOM suppresses excessive crystal growth while preserving polymer chain mobility and mechanical flexibility. This molecular-level design strategy facilitates unprecedented multi-level control over chain conformation, crystal alignment, and additive dispersion, thereby overcoming the traditional trade-offs among β-phase content, dielectric loss, and toughness while offering a versatile approach to polymer crystallization control.