Spherulitic Characterization and Hierarchical Structural Evaluation of Azacalixarene-Polyethylene Glycol Copolymers Containing s-Triazine Rings

This study investigates the solid-state structure of a copolymer composed of polyethylene glycol (PEG) and azacalixarene, which has two s-triazine rings and two phenyl rings alternately crosslinked by amino groups. Azacalixarene derivatives containing a low-molecular-weight linker moiety and exhibiting an amorphous structure have been synthesized in previous studies; however, in this study, they are crystallized by the substitution of the linker moiety with PEG. The spherulites formed by the corresponding copolymer possess the ability to form higher-order structures, growing up to a diameter of 1.7 mm depending on the crystallization conditions. The azacalixarene-PEG copolymer forms negative spherulites via homogeneous nucleation and exhibits a lamellar period at 13.8 nm. The lamellar crystalline part itself is 5.8 nm in thickness; bulky amorphous regions are also observed in the copolymer structure. Reciprocal lattice analysis results reveal that the crystal parts form a packing structure similar to the crystal lattice of PEG. The promotion of spherulite growth is predicted to reflect the characteristics of the corresponding copolymer, which crystallizes while universally containing many amorphous regions.