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In this study, we investigate the chemical, physical and optical properties of cellulose paper irradiated by an electron beam for disinfection. Cellulose chain scission and oxidation induced by radiation increased considerably at 25 kGy irradiation, whereas folding endurance, morphology, and crystallinity did not undergo significant changes. The cellulose chain scission rate of paper irradiated under air-dried and wet conditions showed no difference; however, cellulose oxidation increased to a higher degree in paper irradiated under wet conditions than under air-dried conditions. Electron beam irradiation did not significantly affect changes in paper color, which is associated with oxidation. However, when irradiated papers were aged, the color difference increased according to the irradiation dose, as the oxidized functional groups of cellulose can act as a trigger for color change. A linear relationship between the cellulose chain scission rate and irradiation dose was found; thus, the cellulose chain scission rate can be predicted for a specific dose. The degree of polymerization was calculated from the predicted cellulose chain scission rate using the Ekenstam equation. According to the prediction, the degree of polymerization decreased to 74% at a dose of 5 kGy, a suitable dose for paper disinfection. In the low-dose range, electron beam irradiation did not adversely affect the physical properties of paper, but significant changes occurred in both the chemical and optical properties of paper. Thus, electron beam irradiation may be of use in disinfecting severely degraded paper due to biological factors; however, the irradiation process diminishes paper permanence.Graphic abstract

This study investigates the degradation characteristics of gamma-irradiated aluminum-filled epoxy nanocomposites through the integration of Laser-Induced Breakdown Spectroscopy (LIBS) and supervised machine learning techniques. To simulate prolonged aging in high-voltage insulation settings, epoxy-based composites containing 0 wt% and 5 wt% aluminum nanofillers were subjected to gamma radiation. The LIBS spectra exhibited distinct alterations in the elements of gamma-aged samples, including shifts in the emission lines of carbon and oxygen. This indicates that radiation induced chain scission and oxidation. Principal Component Analysis was employed to reduce spectral dimensionality and reveal underlying trends across four unique material states: unaged and aged, both with and without nanofillers. Principal Component Analysis (PCA) successfully reduced the spectral dimensionality, with the first three principal components (capturing 85.43% of variance) clearly separating the four material states of unaged/aged, with/without nanofillers. Seven machine learning classifiers were evaluated on the PCA-transformed data using a rigorous 5-fold cross-validation protocol. Linear Discriminant Analysis (LDA) and Support Vector Machine (SVM) achieved perfect classification accuracy, while K-Nearest Neighbors (KNN) also performed exceptionally (98.3% ± 3.7%). The results underscore the profound effectiveness of combining LIBS with ML for the non-destructive evaluation of insulation degradation and provide quantitative evidence for the stabilizing role of core–shell structured Al nanofillers. This methodological pipeline demonstrates significant potential for real-time, ML-enhanced condition monitoring of polymeric insulating materials in radiation-prone environments.

This study focuses on the degradation of a silane cross-linked polyethylene (Si-XLPE) matrix filled with three different contents of aluminum tri-hydrate (ATH): 0, 25, and 50 phr. These three materials were subjected to radiochemical ageing at three different dose rates (8.5, 77.8, and 400 Gy·h−1) in air at low temperatures close to ambient (47, 47, and 21 °C, respectively). Changes due to radio-thermal ageing were investigated according to both a multi-scale and a multi-technique approach. In particular, the changes in the chemical composition, the macromolecular network structure, and the crystallinity of the Si-XLPE matrix were monitored by FTIR spectroscopy, swelling measurements in xylene, differential scanning calorimetry, and density measurements. A more pronounced degradation of the Si-XLPE matrix located in the immediate vicinity of the ATH fillers was clearly highlighted by the swelling measurements. A very fast radiolytic decomposition of the covalent bonds initially formed at the ATH/Si-XLPE interface was proposed to explain the higher concentration of chain scissions. If, as expected, the changes in the elastic properties of the three materials under study are mainly driven by the crystallinity of the Si-XLPE matrix, in contrast, the changes in their fracture properties are also significantly impacted by the degradation of the interfacial region. As an example, the lifetime was found to be approximately halved for the two composite materials compared to the unfilled Si-XLPE matrix under the harshest ageing conditions (i.e., under 400 Gy·h−1 at 21 °C). The radio-thermal oxidation kinetic model previously developed for the unfilled Si-XLPE matrix was extended to the two composite materials by taking into account both the diluting effect of the ATH fillers (i.e., the ATH content) and the interfacial degradation.

The ultrasound-assisted depolymerization of κ-carrageenan has been studied at various temperatures and times. The κ-carrageenan with initial molecular weight of 545 kDa was dispersed in water to form a 5 g/L solution, which was then depolymerized in an ultrasound device at various temperatures and times. The viscosity of the solution was measured using Brookfield viscometer, which was then used to find the number-average molecular weight by Mark-Houwink equation. To obtain the kinetics of κ-carrageenan depolymerization, the number-average molecular weight data was treated using midpoint-chain scission kinetics model. The pre-exponential factor and activation energies for the reaction are 2.683×10-7 mol g-1 min-1 and 6.43 kJ mol-1, respectively. The limiting molecular weight varies from 160 kDa to 240 kDa, and it is linearly correlated to temperature. The results are compared to the result of thermal depolymerization by calculating the half life. It is revealed that ultrasound assisted depolymerization of κ-carrageenan is faster than thermal depolymerization at temperatures below 72.2°C. Compared to thermal depolymerization, the ultrasound-assisted process has lower values of Ea, ΔG‡, ΔH‡, and ΔS‡, which can be attributed to the ultrasonically induced breakage of non-covalent bonds in κ-carrageenan molecules. 

Isolated Majorana modes (MMs) are highly non-local quantum states with non-Abelian exchange statistics, which localize at the two ends of finite-size 1D topological superconductors of sufficient length. Experimental evidence for MMs is so far based on the detection of several key signatures: for example, a conductance peak pinned to the Fermi energy or an oscillatory peak splitting in short 1D systems when the MMs overlap. However, most of these key signatures were probed only on one of the ends of the 1D system, and firm evidence for an MM requires the simultaneous detection of all the key signatures on both ends. Here we construct short atomic spin chains on a superconductor—also known as Shiba chains—up to a chain length of 45 atoms using tip-assisted atom manipulation in scanning tunnelling microscopy experiments. We observe zero-energy conductance peaks localized at both ends of the chain that simultaneously split off from the Fermi energy in an oscillatory fashion after altering the chain length. By fitting the parameters of a low-energy model to the data, we find that the peaks are consistent with precursors of MMs that evolve into isolated MMs protected by an estimated topological gap of 50 μeV in chains of at least 35 nm length, corresponding to 70 atoms.Majorana modes are highly non-local quantum states with non-Abelian exchange statistics, which localize at the two ends of finite-size 1D topological superconductors of sufficient length. By precisely positioning magnetic atoms on a superconducting surface, their interaction is tailored such that the precursors of Majorana modes are simultaneously observed on both ends of linear atomic chains.

High-performance membranes exceeding the conventional permeability-selectivity upper bound are attractive for advanced gas separations. In the context microporous polymers have gained increasing attention owing to their exceptional permeability, which, however, demonstrate a moderate selectivity unfavorable for separating similarly sized gas mixtures. Here we report an approach to designing polymeric molecular sieve membranes via multi-covalent-crosslinking of blended bromomethyl polymer of intrinsic microporosity and Tröger’s base, enabling simultaneously high permeability and selectivity. Ultra-selective gas separation is achieved via adjusting reaction temperature, reaction time and the oxygen concentration with occurrences of polymer chain scission, rearrangement and thermal oxidative crosslinking reaction. Upon a thermal treatment at 300 °C for 5 h, membranes exhibit an O 2 /N 2 , CO 2 /CH 4 and H 2 /CH 4 selectivity as high as 11.1, 154.5 and 813.6, respectively, transcending the state-of-art upper bounds. The design strategy represents a generalizable approach to creating molecular-sieving polymer membranes with enormous potentials for high-performance separation processes. Microporous polymers become increasingly attractive as materials for the fabrication of permeable and selective gas separation membranes but separation performance is often limited by broad pore size distribution. Here, the authors design a porous polymer membrane via multi-crosslinking of miscible blends of microporous polymers enabling simultaneous high permeability and selectivity.

Addition of molecular cross-links to polymers increases mechanical strength and improves corrosion resistance. However, it remains challenging to install cross-links in low-functionality macromolecules in a well-controlled manner. Typically, high-energy processes are required to generate highly reactive radicals in situ, allowing only limited control over the degree and type of cross-link. We rationally designed a bis-diazirine molecule whose decomposition into carbenes under mild and controllable conditions enables the cross-linking of essentially any organic polymer through double C–H activation. The utility of this molecule as a cross-linker was demonstrated for several diverse polymer substrates (including polypropylene, a low-functionality polymer of long-standing challenge to the field) and in applications including adhesion of low–surface-energy materials and the strengthening of polyethylene fabric.

Molecular knots and entanglements form randomly and spontaneously in both biological and synthetic polymer chains. It is known that macroscopic materials, such as ropes, are substantially weakened by the presence of knots, but until now it has been unclear whether similar behaviour occurs on a molecular level. Here we show that the presence of a well-defined overhand knot in a polymer chain substantially increases the rate of scission of the polymer under tension (≥2.6× faster) in solution, because deformation of the polymer backbone induced by the tightening knot activates otherwise unreactive covalent bonds. The fragments formed upon severing of the knotted chain differ from those that arise from cleavage of a similar, but unknotted, polymer. Our solution studies provide experimental evidence that knotting can contribute to higher mechanical scission rates of polymers. It also demonstrates that entanglement design can be used to generate mechanophores that are among the most reactive described to date, providing opportunities to increase the reactivity of otherwise inert functional groups. Knots reduce the tensile strength of macroscopic threads and fibres. Now it has been shown that the presence of a well-defined overhand knot in a polymer chain can substantially increase the rate of scission of the polymer under tension, as deformation of the polymer backbone induced by the tightening knot activates otherwise unreactive covalent bonds.

The mechanical degradation of polymers is typically limited to a single chain scission per triggering chain stretching event, and the loss of stress transfer that results from the scission limits the extent of degradation that can be achieved. Here, we report that the mechanically triggered ring-opening of a [4.2.0]bicyclooctene (BCOE) mechanophore sets up a delayed, force-free cascade lactonization that results in chain scission. Delayed chain scission allows many eventual scission events to be initiated within a single polymer chain. Ultrasonication of a 120 kDa BCOE copolymer mechanically remodels the polymer backbone, and subsequent lactonization slowly (~days) degrades the molecular weight to 4.4 kDa, > 10× smaller than control polymers in which lactonization is blocked. The force-coupled kinetics of ring-opening are probed by single molecule force spectroscopy, and mechanical degradation in the bulk is demonstrated. Delayed scission offers a strategy to enhanced mechanical degradation and programmed obsolescence in structural polymeric materials. The mechanical degradation of polymers is typically limited to a single chain scission event and the loss of stress transfer during the scission process limits the extent of degradation achieved. Here, the authors report a mechanically triggered, delayed scission strategy that allows many eventual scission events to be initiated within a single polymer chain.

Advances in polymer chemistry over the last decade have enabled the synthesis of molecularly precise polymer networks that exhibit homogeneous structure. These precise polymer gels create the opportunity to establish true multiscale, molecular to macroscopic, relationships that define their elastic and failure properties. In this work, a theory of network fracture that accounts for loop defects is developed by drawing on recent advances in network elasticity. This loop-modified Lake–Thomas theory is tested against both molecular dynamics (MD) simulations and experimental fracture measurements on model gels, and good agreement between theory, which does not use an enhancement factor, and measurement is observed. Insight into the local and global contributions to energy dissipated during network failure and their relation to the bond dissociation energy is also provided. These findings enable a priori estimates of fracture energy in swollen gels where chain scission becomes an important failure mechanism.