Structure and Dynamics of Supramolecular Polymers Formed by Tris-3,7-dimethyloctyl-cis-1,3,5-cyclohexanetricarboxamide in n-decane via Hydrogen Bonding

Abstract

Dynamic viscoelastic, dielectric and dynamic flow birefringence measurements were carried out in a highly viscoelastic system (DO₃CH/C₁₀), solutions of tris-3,7-dimethyloctyl-cis-1,3,5-cyclohexanetricarboxamide (DO₃CH) in n-decane (C₁₀), for a wide concentration (c) range to investigate structure and dynamics of supramolecular polymers formed in the system due to intermolecular hydrogen bonding. The DO₃CH/C₁₀ system showed pronounced viscoelastic behavior possessing two relaxation modes: a fast mode with a relaxation time (τ1) independent of c and strength G₁ ∝ c², and a slow mode with the other relaxation time (τ2) highly dependent of c and strength G₂ ∝ c^1∼1.3. In dielectric and dynamic flow birefringence behavior, singe relaxation modes were clearly observed, which corresponded to the slow relaxation mode with τ2 in viscoelastic behavior. These reveal that two kinds of supramolecular polymers are formed in the system, i.e. a rigid rodlike supramolecular polymer of ca. 45 nm length, which is formed by ∼100 DO₃CH molecules via 3-fold hydrogen bonding of amide groups and bear a macro-electric dipole moment of ca. 1100 D, and a flexible supramolecuar polymer with little optical anisotropy and electric dipole moment, which is formed by almost randomly connected DO₃CH molecules via hydrogen bonding bearing many defects responsible for a “phantom-crossing” mechanism at entanglement points.