The sensitized triplet–triplet annihilation-based upconversion in bicomponent systems is currently considered the most promising strategy for increasing the light-harvesting ability of solar cells. Flexible, manageable, inexpensive up-converting devices become possible by implementing this process in elastomers. Here, we report a study combining optical spectroscopy data of the light conversion process with the nano- and macroscopic viscoelastic characterization of the host material embedding the active dyes, in order to find a rationale for the fabrication of efficient solid-state upconverting systems. By using the poly­(n-alkyl acrylates) as a model of the monophasic elastomers, we demonstrate that the yield of the bimolecular interactions at the base of the upconversion process, namely, energy transfer and triplet–triplet annihilation, is mainly determined by the glass transition temperature (T g) of the polymer. By employing the polyoctyl acrylate (T g = 211 K), we achieved a conversion yield at the solid state larger than 10% at an irradiance of 1 sun, showing the potential of the elastomer-based upconverting materials for developing real-world devices.

We studied the network structure of elastomers based on polyisoprene, polybutadiene, and their blends in the narrow range of formulations compatible with actual use in the automotive tyre industry. Cross‐link density (CLD) was quantified comparatively by low‐field 1H multiple quantum time domain nuclear magnetic resonance (MQ TD‐NMR) and by equilibrium swelling technique. The robustness and agreement of the two methods was demonstrated in measuring minute alterations of unfilled vulcanizates beyond the optimum cure time. Comparison with samples where polysulfidic bonds were selectively cleaved also demonstrates that the length of the sulfur chain constituting the cross‐link does not significantly affect residual dipolar coupling. Kraus, Lorenz, and Parks correction for filler restriction on swelling is validated by MQ TD‐NMR, which also allows extracting information on cross‐link distribution not provided by swelling measurement. Cross‐link distributions in the blends were demonstrated to be significantly different from the weighted average of the pure samples, while average proton–proton residual dipolar coupling values correspond. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42700.

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