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The dynamics of semistiff polymers in solution is a subject that has attracted great interest over the past two decades but has made only slow progress due to the difficulty of the mathematical treatment. Harris and Hearst were the first to attempt to solve the dynamics using the wormlike chain model of Kratky and Porod, while Soda pointed out the internal inconsistencies of their model a few years later. The model has nevertheless been used by several authors such as Moro and Pecora and Maeda and Fujime to describe dynamic light scattering from semiflexible molecules and by Schmidt and Stockmayer to study the first cumulant in dynamic light scattering. Soda has used a Harris-Hearst-like model to describe the dynamic light scattering from circular wormlike chains by generalizing tile work of Berg. Yamakawa and Yoshisaki have also presented a theory of the more general helical wormlike chain, but no calculations of dynamic light scattering have been done with this theory to date. The first theory of the dynamics of the wormlike chain shown to be free of the inconsistencies of the Harris-Hearst theory was presented by Aragón and Pecora (hereafter referred to as AP). The important advance made in this theory was the introduction of the pure bending equation of motion and the procedures for calculating correlation functions for nonstretching chains. The constraint of constant length can be handled exactly by using the proper tangent vector orientational distribution function. This theory was used by Aragón to calculate the electric field correlation functions for forward depolarized light scattering. An important feature of this theoretical framework is that the rigid-rod limits are always correctly obtained, while this is not the case in all the alternate theories presented to date. In the work of Aragón, however, hydrodynamic interactions and dynamical couplings between degrees of freedom have been ignored.
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