Lamellar thickness in semicrystalline polymers as a result of the competition between crystal growth and intracrystalline chain dynamics

Abstract The non-equilibrium thickness of lamellar crystals in semicrystalline polymers varies largely between different polymer systems and depends on the crystallization temperature Tc. There is currently no consensus on the mechanism of thickness selection. Previous work has highlighted the decisive role of intracrystalline chain dynamics (ICD) in special cases, but a systematic dependence of lamellar thickness on relevant timescales such as that of ICD and stem attachment has not yet been established. Studying the morphology by small-angle X-ray scattering and the two timescales by NMR methods and polarization microscopy, we here present data on poly(oxymethylene), a case with comparably slow ICD. It fills the gap between previously studied cases of absent and fast ICD, enabling us to establish for the first time a quantitative dependence of lamellar thickness on the competition between the noted timescales.