Differential scanning calorimetry study of cross-nucleation between polymorphs in isotactic poly(1-butene)

BACKGROUND: Cross-nucleation is denoted as the heterogeneous nucleation of a ‘daughter’ polymorph on another pre-existing (‘parent’) structure of the same substance. Several examples of the phenomenon for semicrystalline polymers have recently been reported. Polarized optical microscopy is commonly used to investigate both the morphology and the kinetics aspects of cross-nucleation. Hereby, we propose a DSC approach for the quantitative investigation of cross-nucleation in seeded crystallization. This case study deals with isotactic poly(1-butene) Form II on Form I nucleation. RESULTS AND CONCLUSION: Seeds of the trigonal Form I were produced in situ in poly(1-butene) samples, their amount and characteristic size being varied by appropriate choice of the thermal protocol. DSC isothermal and non-isothermal crystallization measurements of Form I seeded samples were performed, highlighting a meaningful nucleation effect of the stable polymorph on Form II. As expected, the nucleating efficiency is highly dependent on the specific content of Form I seeds (i.e. the area of Form I spherulites per unit sample volume). Depending on the seeding and crystallization conditions, Form II crystallization is dominated by nucleation either on foreign heterogeneous surfaces or on Form I crystals. The described quantitative approach can be extended to the study of cross-nucleation in polymorphic systems in which morphological evidence is not sufficiently informative. © 2018 Society of Chemical Industry