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

Abstract

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

Unprecedented Efficiency Increase in a Ternary Polymer Solar Cell Exhibiting Polymer-Mediated Polymorphism of a Non-Fullerene Acceptor

“…As an additional signature of the nucleation effect, a higher crystallization temperature tail is usually observed, along with an overall shift in the peak toward higher temperature, which is also observed in our study (77.2 °C versus 80.0 °C, Figure S7). Therefore, we propose that the host donor PTQ10 nucleates IDID to form a distinct polymorph as assisted by processing in o -DCB.…”

Cross‐nucleation of polybutene‐1 Form II on Form I seeds with different morphology

“…All the samples were crystallized isothermally at 105°C, after melting the original Form II/Form I crystals at 124°C. The thermal treatment at relatively high temperature ensures that the remaining seeds are composed of Form I only, while any crystalline memory of possible residual Form II crystals (ie, self‐nucleation) is erased . In all the three morphologies, a clear transcrystalline layer (TCL), indicative of a very high “linear density” of nucleation sites, develops with time.…”

“…Then the samples were quickly cooled down to room temperature and aged for more than 1 month in order to completely transform the original Form II crystals into Form I. It should be noted that, according to previously adopted procedures for cross‐nucleation studies in PB‐1, a dual morphology is produced . Indeed, low melting temperature crystals of Form I, formed during quenching to room temperature, are essential for having molten PB‐1 in contact with crystalline Form I seeds (with higher melting temperature) …”