Influence of Molecular Structure Changes Induced by Alkaline Stimulation on the Stretching‐Induced Crystallization Behavior of P(VDF‐CTFE)

While stretch‐induced melting and recrystallization in semi‐crystalline polymers are well characterized, how external stimuli like solvent exposure drive molecular structural changes and consequent crystal evolution remains poorly understood. Here, the work elucidates the link between molecular chain modifications and stretch‐induced crystallization in ammonia‐treated poly(vinylidene fluoride‐chlorotrifluoroethylene) [P(VDF‐CTFE)] copolymers. Alkaline treatment triggers dehydrohalogenation, generating backbone CC bonds, confirmed by FTIR and NMR spectroscopy. Mechanical testing revealed distinct tensile property shifts: increased strength yet decreased elongation at break upon modification. Critically, in situ SAXS/WAXS showed that ammonia treatment suppresses oriented fibrillar crystal formation during stretching, thereby disrupting the original lamellar structure and micro‐phase domains. WAXS analysis further demonstrated reduced intensities for the (101), (102), and (103) crystal planes with prolonged modification time, attributable to alterations to the molecular chain. These findings establish that alkaline‐induced molecular structural changes critically regulate stretch‐induced crystallization, paving the way for predicting environmental effects on polymer structure–property relationships.