Laser light scattering of PBLG in DMF

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Abstract
We report measurements of static and dynamic properties of poly(γ‐benzyl‐L‐glutamate) (PBLG) in dimethyl formamide at 25 °C using laser light scattering. Correlation‐function profile analyses were performed using the histogram method. The resultant average linewidth and dispersion were reconfirmed using the cumulants method. We were able to determine the molecular‐weight distribution of PBLG using the histogram method and to confirm the polydispersity for rod polymers in solution to be roughly Mw/Mn ∼ 1 + μ2/Γ2. In our analysis of the Rayleigh linewidth, we used both the rigid‐rod model and the Fujime approach involving rod flexibility. We obtained very reasonable agreement between the Fujime theory and our experiments and concluded that for most stiff polymers of interest, it would be more appropriate to use the Fujime approach, which could also yield a rod‐flexibility parameter. In semidilute solutions, we observed two effects, namely, a maximum in the diffusion coefficient and a broadening of the linewidth distribution function at both low and high frequencies, which were not predicted by the Doi‐Edwards theory.