Article
Chemistry, Multidisciplinary
Yuma Goto, Shun Omagari, Ryuma Sato, Takuya Yamakado, Ryo Achiwa, Nilanjan Dey, Kensuke Suga, Martin Vacha, Shohei Saito
Summary: The study utilized a dual fluorescent molecular probe to monitor nanoscale dynamics in polystyrenes, revealing that planarization of the molecule in the excited state only occurs when a large polymer free volume is available nearby, lasting on average 1.2 seconds. This investigation provides insights into the dynamics of molecular environments through statistical analysis and computational simulations.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2021)
Article
Polymer Science
Mohammed Al Otmi, Frank Willmore, Janani Sampath
Summary: Polymers are attractive materials for membranes due to their mechanical robustness and cost-effective fabrication. The performance of membranes is influenced by free volume elements (FVEs), which tend to degrade over time. Understanding the relationship between chain dynamics and FVE distribution can lead to more efficient regulation of penetrant transport in amorphous polymer membranes.
Article
Chemistry, Multidisciplinary
Halyna Klym, Ivan Karbovnyk, Sergei Piskunov, Anatoli I. Popov
Summary: This study demonstrates the use of positron annihilation lifetime spectroscopy (PALS) method for investigating free volume changes in functional ceramic materials, using nanostructured MgAl2O4 spinel as a case study. The analysis shows that technological modifications can lead to volume shrinking and decrease in defect-related voids in ceramics with well-developed porosity. The approach presented here can be applied to a wide range of functional nanomaterials with pronounced porosity.
Article
Biochemistry & Molecular Biology
Giovanni Consolati, Eros Mossini, Dario Nichetti, Fiorenza Quasso, Giuseppe Maria Viola, Erkin Yaynik
Summary: The study compared the free volume fraction obtained from experiments with the lattice-hole model, revealing that a cylindrical flattened geometry of the cavities provided better agreement than a spherical shape. Additionally, the best fit was found for holes that expanded preferentially in the radial direction, with a decrease in aspect ratio as temperature decreased.
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
(2021)
Article
Materials Science, Multidisciplinary
Yalin Zhao, Rongjin Huang, Zhixiong Wu, Hua Zhang, Zhengrong Zhou, Laifeng Li, Yun Dong, Mi Luo, Bangjiao Ye, Hongjun Zhang
Summary: The study successfully fabricated a high-strength hyperbranched epoxy composite and found that composites with smaller free volume holes exhibited better impact and compression properties. The impact and tensile properties of the composites were positively correlated with the fraction of free volume holes at 77 K, providing valuable information for regulating the cryogenic mechanical properties of thermosetting materials in the future.
MATERIALS & DESIGN
(2021)
Article
Polymer Science
Shinian Cheng, Zaneta Wojnarowska, Malgorzata Musial, Slawomir Kolodziej, Eric Drockenmuller, Marian Paluch
Summary: The study investigates the volume effects in a specific 1,2,3-triazolium-based poly(ionic liquid) at both the macro and nano scales. The experimental determination of a relatively large free volume (V-f) suggests it as the main factor controlling the superionic properties of the material. The analysis of specific volume and relaxation dynamics in terms of different models did not work for the studied system.
Article
Chemistry, Physical
Giovanni Consolati, Fiorenza Quasso, Erkin Yaynik, Francesco Briatico Vangosa, Ondrej Sausa, Katharina Ehrmann, Helena Svajdlenkova
Summary: In this study, the temperature dependence of free volume in dimethacrylates cured by different methods and a thiol-based 2M sample was investigated. The results showed systematic differences between the free volume fraction determined using the spherical approach and the lattice-hole theory. Cylindrical holes expanded differently in different samples. The near infrared spectroscopy also revealed the influence of hydrogen bond changes and monomer conversion on the final cured thermosets.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Review
Polymer Science
Giovanni Consolati, Dario Nichetti, Fiorenza Quasso
Summary: Positron annihilation lifetime spectroscopy (PALS) is a valuable technique used to investigate defects in solids with a sensitivity of 10(-7). It can reveal the size, structure, and concentration of vacancies in metals, alloys, semiconductors, porous systems, and polymers. PALS provides quantitative measurements of the free volume, which is correlated to important properties of polymers and can be deduced theoretically.
Article
Polymer Science
Azusa Togo, Hideaki Hagihara
Summary: This study evaluated the relationship between the enzymatic degradation rate of biodegradable plastics and the amorphous structure of the polymer. The free-volume of the amorphous part, which refers to the cavity between the polymer chains, is known to impact various physical properties. Enzymatic degradation tests were conducted on polylactic acid (PLA) films with different free-volume hole sizes estimated by positron annihilation lifetime spectroscopy (PALS). The results showed that films with different free-volume hole sizes near the surface region degraded in different modes, and there was a positive correlation (correlation coefficient: 0.713) between the degradation rate in the initial 30 minutes and the free volume size near the surface. These findings suggest that controlling the free volume size can control the degradation rate of the amorphous region, which is significant for the future applications of biodegradable plastics in various fields.
POLYMER DEGRADATION AND STABILITY
(2023)
Article
Engineering, Chemical
Jingjing Kong, Junjie Liu, Peiyu Jia, Ning Qi, Zhiquan Chen, Shan Xu, Nanwen Li
Summary: This study investigates the effect of thermal treatment on the chain structure and gas transport performance of polyimide membranes. The results show that heating leads to the rearrangement of polyimide into rigid polybenzoxazole, increasing the size and quantity of free volume and enhancing gas permeability. Crosslinking during heating reduces the size and quantity of free volume by tightening the chain spacing. By designing the functional groups of the reaction monomer and applying appropriate thermal treatment, the microstructure of polyimide membranes can be adjusted to achieve high-performance gas separation.
JOURNAL OF MEMBRANE SCIENCE
(2022)
Article
Chemistry, Applied
Santiago Estevez-Areco, Carlos Macchi, Lucas Guz, Silvia Goyanes, Alberto Somoza
Summary: The effect of citric acid (CA) concentration and water content on the free hole volume of thermoplastic cassava starch films (TPS) was studied. The increase in CA concentration leads to wider free hole volume distributions with lower mean values. The water vapour permeability was significantly higher in films incorporating 5 % (w/w) of CA, in line with the more open network of this material that was revealed in the hole volumes distribution.
CARBOHYDRATE POLYMERS
(2023)
Article
Polymer Science
Giovanni Consolati, Dario Nichetti, Fiorenza Quasso
Summary: The dependence of free volume on temperature was investigated in copolymers and a terpolymer, with the lattice-hole model applied. Macroscopic behavior was analyzed using dilatometry, while positron annihilation lifetime spectroscopy provided insight into the microstructure of free volume. The coupling of these techniques allowed for the determination of hole density under specific assumptions about cavity geometry. The results showed that the hole shapes were more similar to discs than spheres, with aspect ratio decreasing as temperature increased. This radial growth was not influenced by the presence of acrylonitrile, unlike in butadiene-isoprene blends.
POLYMER INTERNATIONAL
(2022)
Article
Materials Science, Ceramics
O. Shpotyuk, A. Ingram, Y. Shpotyuk, V. Adamiv
Summary: This study investigates the vitrification and devitrification transitions in network oxide compounds using a revised positron annihilation lifetime analysis. It finds that volume-expanded vitrification and volume-contracted devitrification processes occur in SiO2-based network systems, while polymorphous transformations are unfavorable in B2O3-based systems. However, these transitions become possible in modified borates like lithium tetraborate Li2B4O7.
JOURNAL OF NON-CRYSTALLINE SOLIDS
(2023)
Article
Multidisciplinary Sciences
Qing Liu, Chongshan Yin, Xi Li, Chunqing He, Zhi Ding, Xuan Du
Summary: In this study, it was found that four varieties of rice cultivated under the same conditions and duration showed different lodging resistance. Three key factors influencing lodging resistance were identified: the thickness of the depressed region of the culm wall, the flexibility of the culm, and the nitrogen element content in the basal culm.
SCIENTIFIC REPORTS
(2022)
Article
Polymer Science
Fang Wei, Junheng Zhang, Cheng Wu, Mi Luo, Bangjiao Ye, Hongjun Zhang, Junsheng Wang, Menghe Miao, Tingcheng Li, Daohong Zhang
Summary: Recyclable flame-retardant epoxy resins (FREPs) have been developed using itaconic acid-derived hyperbranched epoxy resin (IA-EHBP) and (1,3,5-hexahydro-s-triazine-1,3,5-triyl)benzyl mercaptan (HT-BM). These resins can be degraded into monomers with high yield and the IA-EHBP structure improves their mechanical properties. The incorporation of IA-EHBP also enhances the flame retardancy of the resins by promoting char residue formation and preventing the generation of combustible volatiles. This method provides a convenient and closed-loop approach for efficient chemical recycling and reuse of end-of-life flame-retardant materials.
