In this study, we utilized tetra-armed polyethylene glycol (Tetra-PEG) slimes, which are model transient networks with well-controlled structures, to predict the effects of long-term degradation on the viscoelastic properties of liquids. Viscoelastic liquids, such as sodium hyaluronate, are frequently used in biomedical applications within the human body. However, precisely controlling the viscoelastic properties of these liquids in the long-term is challenging, as the main chains of the liquids undergo stochastic degradation. To establish a predictable model for studying long-term degradation effects, we employed Tetra-PEG slime, and modifications were performed to introduce specific cleavage sites in areas with connections. The Tetra-PEG slimes were characterized by single relaxation modes, and these modes were independent from the degree of degradation, which was determined by hydrolyzing the cleavage sites. Overall, this work provides a universal design for viscoelastic liquids with precisely-controllable degradation.

The mobility of sustained molecules is influenced by viscoelasticity, which is strongly correlated with the diffusional property in polymeric liquid. However, the study of transient networks formed by a reversible crosslink, which is the viscoelastic liquid, was insufficient due to the absence of a model system. We compare the viscoelastic and diffusional properties of the transient networks, using the model system with controlled network connectivity (Tetra-PEG slime). According to independent measurements of viscoelasticity and diffusion, the root-mean-square distance the polymer diffuses during the viscoelastic relaxation time shows a large deviation from the self-size of the polymer, which is contrary to the conventional understanding. This decoupling between viscoelasticity and diffusion is unique for transient networks, suggesting that the viscoelastic relaxation is not induced by the diffusion of one prepolymer, particularly in the network with low connectivity. These findings will provide a definite basis for discussion to understand the viscoelasticity in transient networks.

Research on Tohoku dialects, which is a variety of Japanese, has found that the voiceless stops /k/ and /t/ in the intervocalic position are frequently realized as voiced stops. However, the phenomenon has mainly been judged aurally in the Japanese linguistics literature and has not been confirmed by acoustic measurements. We measured the VOT of data originally collected in the survey of Tohoku dialects by [1]. The data used in this study includes two age groups from eight sites. The results demonstrate that for word medial stops, the VOT distribution of voiced and voiceless stops largely overlapped, while, the laryngeal contrast was maintained for the word initial stops. Intervocalic voicing neutralization was confirmed by quantitative acoustic measurements. The effects of neighboring vowels were also investigated to show that height, but not duration, had a significant effect on voicing neutralization. Our results shed light on the phonetic nature of Tohoku dialects as well as on their phonological structure, such as the role of voicing contrast.