Self-Assembly Modulation of Stereocomplexes of Chiral 2-Hydroxy-2-Phenylacetic Acids in Poly(ethylene oxide)

2-Hydroxy-2-phenylacetic acids or mandelic acids (MA) are chiral molecules with enantiomers of S- and R-forms, and their racemic mixture is known as para-mandelic acid. With poly(ethylene oxide) (PEO) as a morphology tailor, a novel ring-banded spherulite with a ginger-root-like structure is formed in nonracemic (S)-MA/(R)-MA mixtures, where addition of diluent PEO was to modulate the crystallization kinetics of (S)-MA/(R)-MA structure. The novel crystal assembly was analyzed to determine the formation mechanisms of the ring-banded spherulites. Top-surface and interior-dissection microscopy techniques and X-ray characterization are performed on novel periodically banded rings assembled on separate lobs of ginger-root-like crystal aggregates in nonracemic mixtures of chiral mandelic acids. Detailed 3D assembly and mechanisms of growth and manipulated self-assembly are proved by microscopy and X-ray analysis and supported by direct morphology dissection evidence, and the complexed architecture of the periodic assembly on individual cactus-like arms is investigated, whose growth and optimized morphology design are probed.