Dynamic birefringence and rigidity of poly- p-benzamide molecules in solutions

Abstract

Flow birefringence (FB) in solutions of a number of samples of poly- p-benzamide (PPBA) in sulphuric acid has been investigated; intrinsic viscosities [η] of the same solutions have been measured. Characteristic values of FB, [ n], and orientation angles [ χ/ g] of the solutions were determined. Molecular weights of all the PPBA samples were calculated by using the values of [ χ/ g] and [η]. The dependence [ η] = 1.6 × 10 −5 M 1.7 shows that the conformation of PPBA molecules in solution is close to that of a straight rod. The use of characteristic values of [ n] and [ χ/ g] and the theory of optical anisotropy of persistent chains gives quantitative data on the equilibrium rigidity of PPBA molecules. It was shown that the number of molecular units in a statistical segment of the PPBA chain is 320 and the corresponding length of the segment is 2000 Å.