Hard–soft–hard
triblock copolymers based on poly(ethylene
oxide) (PEO), poly(2-naphthyl glycidyl ether)-block-poly[2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether]-block-poly(2-naphthyl glycidyl ether)s (PNG-PTG-PNGs), were
synthesized by sequential ring-opening polymerization of 2-(2-(2-methoxyethoxy)ethoxy)ethyl
glycidyl ether and 2-naphthyl glycidyl ether using a bidirectional
initiator catalyzed by a phosphazene base. Four PNG-PTG-PNGs had different
block compositions (f
wt,PNG = 9.2–28.6
wt %), controlled molecular weights (M
n = 23.9–30.9 kDa), and narrow dispersities (Đ = 1.11–1.14). Most of the PNG-PTG-PNG electrolytes had much
higher Li+ conductivities than that of a PEO electrolyte
(6.54 × 10–7 S cm–1) at room
temperature. Eespecially, the Li+ conductivity of PNG18-PTG107-PNG18 electrolyte (9.5 ×
10–5 S cm–1 for f
wt,PNG = 28.6 wt %) was comparable to one of a PTG electrolyte
(1.11 × 10–4 S cm–1). The
Li+ conductivities of PNG-PTG-PNG electrolytes were closely
correlated to efficient Li+ transport channels formed by
the microphase separation into soft PTG and hard PNG domains.
Microplastics have recently been identified as one of the major contributors to environmental pollution. To design and control the biodegradability of polymer materials, it is crucial to obtain a better understanding of the aggregation states and thermal molecular motion of polymer chains in aqueous environments. Here, we focus on melt-spun microfibers of a promising biodegradable plastic, polyamide 4 (PA4), with a relatively greater number density of hydrolyzable amide groups, which is regarded as an alternative to polyamide 6. Aggregation states and thermal molecular motion of PA4 microfibers without/with a post-heating drawing treatment under dry and wet conditions were examined by attenuated total reflectance-Fourier transform infrared spectroscopy and wide-angle X-ray diffraction analysis in conjunction with dynamic mechanical analysis. Sorbed water molecules in the microfibers induced the crystal transition from a meta-stable γ-form to a thermodynamically stable α-form via activation of the molecular motion of PA4 chains. Also, the post-drawing treatment caused a partial structural change of PA4 chains, from an amorphous phase to a crystalline phase. These findings should be useful for designing PA4-based structural materials applicable for use in marine environments.
Purpose: This study aimed to examine how breathing exercise accompanied by dynamic upper extremity exercise affects pulmonary function and respiratory muscle strength in females in their 20s who were confirmed to have COVID-19. Methods: This study included female students in their 20s who passed 3-5 weeks after being diagnosed with COVID-19. The subjects were assigned to experimental and control groups according to the participation period. The experimental group performed 10 min of warm-up and cool-down exercise and 30 min of diaphragmatic breathing exercise accompanied by dynamic upper extremity exercise three times per week for 4 weeks. Pulmonary function (forced vital capacity and forced expiratory volume at one second) and respiratory muscle strength (maximal expiratory pressure and maximal inspiratory pressure) were assessed using a spirometer. Cough capacity (peak expiratory flow) was assessed using a peak flow meter. Data analysis was performed using independent and paired t-tests. Results: No significant increase in pulmonary function and respiratory muscle strength was observed in both groups. However, the experimental group showed a significant increase in cough capacity and grip strength (p<.05). Conclusion: Breathing exercise accompanied by dynamic upper extremity exercise may be effective in improving cough capacity and grip strength in females in their 20s with confirmed COVID-19.
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