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.
Highlights
Aggregation and gelation of macromolecules are universal and crucial critical phenomena
The chemical structures of ABAB and AABB have been drawn and the chemical shifts of the protons in the polymers have been predicted with ChemDraw and MestReNova, the predicted data has been shown in the supplementary information
The structures have been defined via FTIR, 1H NMR and analytical ultracentrifuge (AUC)
Summary
The chemical structures of ABAB and AABB have been drawn and the chemical shifts of the protons in the polymers have been predicted with ChemDraw and MestReNova, the predicted data has been shown in the supplementary information. The analytical ultracentrifuge (AUC) has been used to study the sedimentation velocity (SV) of the two polymers in THF with the concentration of 1.0 mg/ml, to determine the molecular weight of the prepared ABAB and AABB. The sedimentation velocity distribution calculated from a SV experiment and Lamm equation analyzed by the c(s) model, for ABAB and AABB in THF
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