Rotational Relaxation of Chlorobenzene in Poly(methyl methacrylate). 2. Theoretical Interpretation

The depolarized Fabry-Perot spectrum of chlorobenzene (CB) in poly(methyl methacrylate) (PMMA), which exhibits fast (picosecond time scale) and slow, broad-distribution (nanosecond to millisecond) relaxation times, is interpreted in terms of two theories, the “diffusion in two environments” (DITE) theory and the restricted rotational diffusion (RRD) theory. The DITE theory along with the free-volume theory was used to estimate the critical void volume per CB molecule, which allows fast relaxation, as 203 Á3. The RRD theory was used to calculate the cone angle of rotation as well as the rotational diffusion coefficient over a range of temperature and CB concentrations. © 1980, American Chemical Society. All rights reserved.