We investigated the effects of two metal salts, lithium trifluoromethanesulfonate (LiCF3SO3) and lithium bromide (LiBr), on the glass transition temperature (Tg) of poly(methyl methacrylate) (PMMA). Both LiCF3SO3 and LiBr greatly enhanced the Tg of PMMA under dry conditions. However, once the sample films were exposed to humidity, the PMMA containing LiCF3SO3 absorbed a large amount of water, which acts as a plasticizer. As a result, the Tg shifted to a lower temperature, which limits the utility of this polymer in industrial applications. In contrast, the Tg of PMMA containing LiBr was minimally affected by the absorption of water. This phenomenon can be explained by the ion–dipole interactions with the small number of dissociated lithium cations.
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We express our sincere gratitude to Mitsubishi Chemical Holdings for their valuable suggestions and their kindness in supplying the sample employed in this study.
This work was supported by the COI program “Construction of next-generation infrastructure system using innovative materials”—Realization of safe and secure society that can coexist with the Earth for centuries—Supported by Japan Science and Technology Agency (JST).
Conflict of interest
The authors declare that they have no conflict of interest.
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Ito, A., Phulkerd, P., Ayerdurai, V. et al. Enhancement of the glass transition temperature of poly(methyl methacrylate) by salt. Polym J 50, 857–863 (2018). https://doi.org/10.1038/s41428-018-0080-4
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