The rigidity of poly-p-benzamide molecules

Depolarization ratios and rigidity of aromatic polyamides

“…[5][6][7][8][9][10][11][12][13][14][15][16] The q values are tabulated in Table I. Diffusion and sedimentation experiments appear not to be suffi- Table I Persistence Length (q) in Á, Measured in 96% Sulfuric Acid technique (ref) p-BA p-PT light scattering, Rg (5) 400 200 light-scattering depolarization ratio (6) 150 flow birefringence (7) 185 light scattering (8) 600 200 viscosity (8) 400 150 flow birefringence (9) 325 light-scattering depolarization (10) 287 electric birefringence, Kerr effect (11) 300 light scattering (12) >450 flow birefringence (13) 1000 flow birefringence (14) 650 flow birefringence (15) 1050 650 flow birefringence (16) 435 275 ciently sensitive to yield even a rough estimate of g. 15,17,18 Changes in the nature and strength of the solvent acid, manifested by variations in the protonation level of the amide groups along the chain and in the consequential changes in chain extension and rigidity, were also reported to affect the exponent o,19,20 the persistence length q,18 and the radius of gyration Bg. 19 Plots by Arpin and Strazielle5,8 of intrinsic viscosity and radius of gyration against weight-average molecular weight (Mw) show the same dependencies and the same data scatter for unfractionated as for fractionated p-PT.…”