Dynamic holographic recording under linear polarized writing beams at 632.8 nm was performed oil two different new spirooxazine doped PMMA matrices assisted by UV light. Thermal rate constants of the two holographic storage medium were determined. It was found that diffraction efficiency and erasure dynamics of the holographic gratings in the two polymer films; were dependent oil the thermal stability and aggregation of spirooxazine molecules in PMMA matrices. During erasure of the holographic gratings, only, in the polymer film with a lower thermal rate constant, a nearly instantaneous increase of diffraction efficiency was observed, resulting from the formation of a transient orientation grating. A theoretical description of the transient orientation grating, competing with isomerization grating's, agrees well with experimental results. The interaction between the chromophores and matrices was also discussed. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 2157-2162, 2009