Role of intermolecular interactions and conformational changes in the polymorphism and vitrification process of 2,2′′-bis-substituted para-terphenyls

摘要: In the past decades, para-terphenyls have been attracting tremendous attention due to their polymorphism and conformational diversity. this work we report synthesis, crystal structure, dielectric properties of two 2,2′′-bis-substituted para-terphenyls: 2,2′′-bis(hydroxymethyl)-para-terphenyl 2,2′′-bis(acetyloxymethyl)-para-terphenyl. On basis calorimetric X-ray studies, showed that latter compound occurs in at least four polymorphic forms with melting points equal 364, 345, 341 326 K, differentiated also terms thermodynamic stability symmetry. The most stable polymorph I is characterized by P21/n space group. 2,2′′-Bis(hydroxymethyl)-para-terphenyl crystallizes monoclinic P21/c Both can undergo vitrification, which a highly exceptional feature for class chemical compounds has not reported before. Consequently, molecular dynamics changes glassy supercooled liquid states were analyzed means IR broadband spectroscopy. Two relaxation processes observed both compounds: structural α-relaxation, connected reorientational motions molecules liquid, intermolecular γ-relaxation, ascribed rotational substituents para-terphenyl skeleton. Taking into account ongoing discussion about diversity skeleton, although free rotation benzene rings suppressed, adopt twisted helical conformations, results forms.