Behavior of an Aromatic Heterocyclic Polymer in Salt Solution.
Special interim rept. Jun 72-Sep 73,
AIR FORCE WRIGHT AERONAUTICAL LABS WRIGHT-PATTERSON AFB OH
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The addition of lithium chloride LiCl to solutions of poly5,5bibenzimidaole-2,2diyl-1,3 phenylene PBI and N,N dimethylacetamide DMAC resulted in the expansion of the PBI molecule in solution. This expansion was owing to the association of lithium andor chloride ions in the region of the nitrogen atoms on the polymer chain. The presence of these ions expanded the polymer chain by means of electrostatic repulsion. This effect was reflected in the results of conductivity and viscosity studies. In general, LiCl can be used for both increased solubility and increased viscosity for this polymer-solvent system. A ratio of 0.125 gram of LiCl per of PBI was determined to be the optimum amount of LiCl to be added. This amount corresponds to one mole of LiCl for every mole of PBI repeat unit. The PBI molecule was determined to have entanglements in concentrated solution at every 27 or 28 molecules along the polymer chain. This length between the entanglements is very low in comparison to other polymers, indicating a strongly interacting system. The chain length between entanglements was approximately the same for both PBI-DMAC and PBI-LiCl-DMAC solutions.
- Polymer Chemistry