title: Aggregation and Gelation of Aromatic Polyamides with Parallel and Anti-parallel Alignment of Molecular Dipole Along the Backbone.
abstract: The understanding of macromolecular structures and interactions is important but difficult, due to the facts that a macromolecules are of versatile conformations and aggregate states, which vary with environmental conditions and histories. In this work two polyamides with parallel or anti-parallel dipoles along the linear backbone, named as ABAB (parallel) and AABB (anti-parallel) have been studied. By using a combination of methods, the phase behaviors of the polymers during the aggregate and gelation, i.e., the forming or dissociation processes of nuclei and fibril, cluster of fibrils, and cluster-cluster aggregation have been revealed. Such abundant phase behaviors are dominated by the inter-chain interactions, including dispersion, polarity and hydrogen bonding, and correlatd with the solubility parameters of solvents, the temperature, and the polymer concentration. The results of X-ray diffraction and fast-mode dielectric relaxation indicate that AABB possesses more rigid conformation than ABAB, and because of that AABB aggregates are of long fibers while ABAB is of hairy fibril clusters, the gelation concentration in toluene is 1 w/v% for AABB, lower than the 3 w/v% for ABAB.
authors.affiliation: Jiangsu Key Laboratory and Bio-functional Materials, School of Chemistry and Materials Sciences, Nanjing Normal University, Nanjing, Jiangsu 210023, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Zhu
authors.affiliation: Jiangsu Key Laboratory and Bio-functional Materials, School of Chemistry and Materials Sciences, Nanjing Normal University, Nanjing, Jiangsu 210023, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Shang
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Ye
authors.affiliation: Jiangsu Key Laboratory and Bio-functional Materials, School of Chemistry and Materials Sciences, Nanjing Normal University, Nanjing, Jiangsu 210023, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Shen