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We found that the dynamic mechanical spectra of linear high-density polyethylene (HDPE) can be controlled by swelling using liquid paraffin (LP) at 100 and 110 °C. The relaxation strength of α relaxation observed above 50 °C decreased with an increase in swelling time. Two novel peaks appeared between γ and α relaxations, denoted as β1 and β2 on the lower temperature side, respectively. These peaks are absent in pristine HDPE and are associated with the immersion of LP molecules in the amorphous phase. β1 appeared at approximately −50 °C and was almost independent of frequency; it is believed to be responsible for the glass transition of LP domains. Meanwhile, β2 appeared at approximately −20 °C, similar to the β-relaxation temperature observed in linear low-density polyethylene (PE) and ultrahigh molecular weight PE. β2 was responsible for the activation of molecular motion in the rigid amorphous chains, such as taut tie-chains in the interlamellar regions, in which the addition of LP expanded the amorphous layers and caused surface melting of the crystalline lamellae.

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We report that lithium salts in lithium-ion batteries effectively modify the physical properties of poly (methyl methacrylate) (PMMA). The glass transition temperature (Tg) is an indicator of the heat resistance of amorphous polymers. The anionic species of the salts strongly affected the glass transition behavior of PMMA. We focused on the additive effects of various lithium salts, such as LiCF3SO3, LiCOOCF3, LiClO4, and LiBr, on the Tg of PMMA. The large anions of the former three salts caused them to form macroscopic aggregates that acted as fillers in the PMMA matrix and to combine the PMMA domains, increasing Tg. On the other hand, LiBr salts dispersed microscopically in the PMMA matrix at the molecular scale, leading to the linking of the PMMA chains. Thus, the addition of LiBr to PMMA increased Tg as well as the relaxation time in the range of glass to rubber transition.