In this section, the model developed in the current paper will be used to characterize and explain the experimental results recently reported in Ref. [25]. As a brief description of the experiment, spiropyrans were covalently linked to the center of polymethacrylate (PMA) linear chains, and the viscous behavior of this elastomer was studied at room temperature, above the glass transition temperature of 12 °C. The elastomer was subjected to uniaxial tension with various profiles of loading rates, and the stress and fluorescence intensity in the elastomer were recorded simultaneously. The activation efficiency was then assumed to be proportional to the captured fluorescence intensity, where the efficiency of a fully activated elastomer after a longtime exposure to UV irradiation was regarded as 100%. For uniaxial tension, we have $\lambda 1=\lambda $, $\lambda 2=\lambda 3=1/\lambda $ in the elastomer, where $\lambda $ is the applied stretch, and thus, the applied true strain is $\epsilon =ln\lambda $. Correspondingly, the principal Cauchy stress in the elastomer can be calculated with Eq. (17) as $\sigma 2=\sigma 3=0$ and $\sigma 1=\sigma $, where
Display Formula

(35)$\sigma =(\lambda 2\u22121\lambda )3\Lambda (NAnAkT1nA\beta A+NBnBkT1\Lambda \nu nB\beta B)$