Intramolecular photodimerization of the photochromic molecule tetraethyl [3,3](1,4)-naphthalene-(9,10)-anthracenophane-2,2,15,15-tetracarboxylate (abbreviated hereafter as cyclophane) was induced by irradiation with linearly polarized Light in the glassy state of,poly(methyl : methacrylate) (PMMA). Compared to its homolog, 9-(hydroxymethyl)-10-[(naphthylmethoxy)methyl]anthracene (HNMA), which is known to undergo intramolecular photodimerization via conformational rearrangements, the reaction of cyclophane is more selective. These results were attributed to the specific cagelike structure of the cyclophane. The time evolution of the induction efficiency eta(t) obtained from the two dichroic I absorbance components of cyclophane shows a rise-and-decay behavior, indicating that irradiation interferes with the selectivity of the reaction. In order to separate this effect from the reorientational; relaxation process of cyclophane in the polymer matrix; the optical anisotropy created by linear polarized light was allowed to relax to the equilibrium state by annealing the irradiated samples over different : time intervals. The decay of eta(t) can be well expressed by the sum of exponential functions of annealing time. From the curve-fitting process, it was found that the temperature dependence of the reorientational relaxation rates of cyclophane follows the Arrhenius type with the activation energy comparable to the beta-process of the PMMA matrix. The activation energy of HNMA obtained under the same conditions is, on the other hand, similar to the gamma-relaxation process of PMMA, These results imply that the reorientational relaxation of molecular dopants might be affected by the local-relaxation processes of the matrix, and dopants with different sizes reflect the rotational motions of different segments of polymer chains. The experimental method described in this work not only provides an intriguing means to design polymer materials with controllable refractive index distribution but also gives a molecular basis for the understanding of the destabilization mechanism of dyes/polymer systems. used in optoelectronic applications.