The Role of Intimate Dipole Carbonyl–Carbonyl and Hydrogen–Carbonyl Interactions in the Stereocomplexation and Crystallization: The Case of Poly(Cyclohexene Carbonate)

Abstract

Abstract Enantiopure isotactic poly(cyclohexene carbonate) (PCHC) has been synthesized with chiral Zn‐β‐diiminate catalyst. PCHC crystallizes both as enantiopure polymer ( R )‐PCHC and ( S )‐PCHC and upon stereocomplexation of the two enantiomers. We report the crystal structures of the enantiopure polymer and of the stereocomplex ( R / S )‐PCHC and explain their crystallization based on the establishment of multiple attractive H‐‐‐O═C interactions between oxygen atoms of carbonyl groups and the hydrogen atoms of the cyclohexyl rings and C═O‐‐‐C═O intimate dipole interactions between carbonyl groups of chains of opposite chirality in the stereocomplex. The crystal structure of the enantiopure polymer is characterized by chains in 2/1 helical conformation packed in the orthorhombic unit cell with axes a  = 11.55 Å , b  = 9.42 Å, and c  = 7.36 Å, according to the space group P 2 1 2 1 2 1 , with steric interdigitation between chains of similar chirality favored by multiple attractive H‐‐‐O═C interactions. The stereocomplex crystallizes in an orthorhombic unit cell with axes a  = 10.40 Å, b  = 8.41 Å, and c  = 7.36 Å, according to the space group Pbc 2 1 , driven by establishment of additional C═O‐‐‐C═O dipole interactions between carbonyl groups of chains of opposite chirality, besides of the multiple attractive H‐‐‐O═C interactions.