Monte Carlo Approach to the Analysis of the Rotational Diffusion of Wormlike Chains

A Monte Carlo analysis is presented which establishes a relationship between the rotational diffusion coefficients and the flexibility (persistence length, P ) of short, wormlike chains. The results of this analysis are presented in terms of experimentally observable quantities; namely, the rotational relaxation times for the field-free decay of optical anisotropy. The pertinent theoretical quantity is R , defined as the ratio of the longest rotational relaxation time of a wormlike chain to the transverse rotational relaxation time of a rigid cylinder having the same axial length ( L ) and segmental volume. R , so defined, is essentially independent of the axial ratio of the cylinder for any value of LIP within the range of validity of the present analysis (axial ratio > 20; 0.1 < L / P < 5). It is pointed out that P can be determined with reasonable accuracy even in the absence of a precise knowledge of the local hydrodynamic radius of the chain.