Hydrodynamic properties and equilibrium rigidity of polyamidobenzimidazole molecules in dimethylacetamide and sulphuric acid |
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Authors: | MG Vitovskaya PN Lavrenko OV Okatova EP Astapenko VB Novakovsky SV Bushin VN Tsvetkov |
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Institution: | Institute of Macromolecular Compounds of the Academy of Sciences U.S.S.R., Bolshoi, 31, Leningrad 199 004, U.S.S.R. |
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Abstract: | Translational diffusion, velocity sedimentation and viscometry of polyamidobenzimidazole (PABI) solutions in the range of M = (1–61) · 103 have been investigated in N,N-dimethylacetamide (DMA) and 98% H2SO4. The dependences of D0, S0 and η] on M were obtained. Tsvetkov-Klenin's hydrodynamic invariant was found to be . The equilibrium rigidity of PABI molecules was characterized by the length of the Kuhn segment . The chain diameter was . The values of A in 98% H2SO4 and in an aprotic solvent, DMA, were virtually identical, implying that the rigid-chain conformation of PABI molecules in 98% H2SO4 is due to their geometrical structure rather than to the protonization of amide bonds. The significance of the latter evidently increases in PABI solutions in 100% H2SO4 in which A is 1.5 times as high. The decrease in rigidity of PABI as compared to that of poly-p-phenylene terephthalamide () is in reasonable agreement with the presence of imidazole rings in PABI molecules. The presence of these rings results in kinks in the PABI chain with angles of about 30° and hence, in the depature from parallelism of rotating bonds. |
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