To Reveal the Importance of the Crystallization Sequence on Micro-Morphological Structures of All-Crystalline Polymer Blends by In Situ Investigation

In crystalline/crystalline polymer blend systems, complex competition and coupling of crystallization and morphology usually happen due to the different crystal nucleation and growth processes of polymers, making the morphology and crystallization behavior difficult to control. Herein, we probe the crystallization sequence during the film formation process (crystallize simultaneously, component A crystallizes prior to B or inverse) to illustrate the micro-morphology evolution process in poly(3-hexylthiophene) (P3HT) and poly[[N,N-bis(2-octyldodecyl)-napthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]- alt-5, 5'-(2,2'-bithiophene)] (N2200) blend using in situ UV-vis absorption spectra and in situ two-dimensional grazing incidence X-ray diffraction (2D GIXRD). When P3HT and N2200 crystallize simultaneously, a large-sized morphology structure is formed. When strengthening the solution aggregation of P3HT by increasing the solvent-polymer interaction, P3HT crystallizes prior to N2200. A P3HT-based micro-morphology structure is obtained. As the molecular weight of N2200 increases to a critical value (72.0 kDa), the crystallization of N2200 dominates the film formation process. A N2200-based micro-morphology is formed guided by N2200 domains. The results confirm that the crystallization sequence is one of the most important factors to determine the micromorphology structure in all-crystalline polymer blends.

Automated summary

In crystalline/crystalline polymer blend systems, the complex competition and coupling of crystallization and morphology are influenced by the different crystal nucleation and growth processes of polymers, making it challenging to control the morphology and crystallization behavior. By studying the crystallization sequence in P3HT and N2200 blends, it was found that the crystallization process plays a crucial role in determining the micro-morphology structure, with simultaneous crystallization leading to large-sized morphology structures and changes in solvent-polymer interaction affecting the crystallization order between P3HT and N2200. The results highlight the importance of crystallization sequence in shaping the micro-morphology structure in all-crystalline polymer blends.