In Situ Monitoring and Tuning Multilayer Stacking of Polymer Lamellar Crystals in Solution with Aggregation-Induced Emission.

Many types of self-assembled 2D materials with fascinating morphologies and novel properties have been prepared and used in solution. However, it is still a challenge to monitor their in situ growth in solution and to control the number of layers in these materials. Here, we demonstrate that the aggregation-induced emission (AIE) effect can be applied for the in situ decoupled tracing of the lateral growth and multilayer stacking of polymer lamellar crystals in solution. Multilayer stacking considerably enhances the photoluminescence intensity of the AIE molecules sandwiched between two layers of lamellar crystals, which is 2.4 times that on the surface of monolayer crystals. Both variation of the self-seeding temperature of crystal seeds and addition of a trace amount of long polymer chains during growth can control multilayer lamellar stacking, which are applied to produce tunable fluorescent patterns for functional applications.

Improvement of Thick Coal Seam Gas Drainage Efficiency Using Highly Pressurized Multidischarge CO2 Gas Fracturing Technique.

Thick coal seam fracture stimulations were conducted to enhance pre-gas drainage efficiency through the use of a highly pressurized multidischarge carbon dioxide gas fracturing technique. This method also offers potential as a strategy for carbon dioxide sequestration, aiding in the reduction of atmospheric carbon dioxide levels and thereby contributing to the fight against climate change. This paper discusses findings from both field experiments and numerical simulations. Data from the field show that the multidischarge fracturing approach significantly improves permeability in thick coal seams, thereby boosting gas drainage effectiveness. Additionally, the impact of increasing the number of fracturing devices is more pronounced at distances of 2.5 or 7.5 m from the borehole but becomes more complex at 12.5 m or further. The numerical simulations reveal that this technique primarily enhances coal seam gas drainage by improving the seam permeability and establishing a gas pressure gradient within the seam. It is noted that the radius of failure around the borehole wall expands with higher discharge pressures, while the radius of effective drainage narrows as the gap between discharge heads increases. Moreover, adding more discharge sets significantly influences the deformation and permeability of the coal seam within a 5 m radius of the fracturing borehole, but the influence is not obvious after 10 m from the fracturing borehole.

Synthesis and Structure-Property Relationships of Novel High Molecular Weight Fully Biobased 2,5-Thiophenedicarboxylic Acid-Based Polyesters.

High molecular weight fully biobased poly(propylene succinate-co-2,5-thiophenedicarboxylate) (PPSTF) random copolyesters based on the emerging biobased aromatic diacid, 2,5-thiophenedicarboxylic acid (TFDCA), in full composition range were synthesized via melt polycondensation. Their crystallization behavior, thermal-mechanical, gas barrier, and biodegradable properties were systematically investigated. A certain level of comonomer cocrystallization was evidenced by XRD, and PTF units had stronger crystallization competitive capability compared to PS units due to the higher stiffness of TFDCA units. These copolyesters exhibited excellent thermal stability, and mechanical properties can be easily controlled by tuning the varied ratio of flexible to rigid segments. Gas barrier properties were studied from both theoretically calculated and experimental perspectives, and the copolyesters even with 50 mol % PS units still showed superior gas permeation resistance. The selected lipase from Aspergillus oryzae can degrade the copolyesters with up to 60 mol % PTF units. The nonbiodegradable-biodegradable transition was found to occur at the number-average sequence length of aromatic PTF units as low as about 3. Interestingly, when compared with their terephthalic acid-based (TA-based) and 2,5-furandicarboxylic acid-based (FDCA-based) analogues with the same content of aromatic units, the apparent degradation rate constant (k) and half period (t1/2) of PPSTF60 were actually between them. These findings offer much promise for the application of polyesters containing odd-carbon diol monomers in green packaging and other fields.

Preparation of Titania-Silica Composite Aerogel at Atmospheric Pressure and Its Catalytic Performance in the Synthesis of Poly (Butylene Succinate).

Titanates are widely used in the synthesis of polyesters, such as Poly (butylene succinate) (PBS), due to their excellent catalytic activity for polycondensation. However, the hydrolysis sensitivity of titanate and side reactions at high temperatures restrict the further improvement of the molecular weight of polyesters and lead to the high content of end carboxyl group content in the products. In this work, we prepared titania-silica composite aerogels with resistance to hydrolysis and large specific surface area, which were further explored as an efficient catalyst for polycondensation reactions. A series of titania-silica composite aerogel catalysts for PBS polycondensation were successfully prepared by the sol-gel method. The influence of a Ti/Si ratio on the surface morphology and structure of the aerogels was examined. Titania-silica composite aerogel exhibits the surface characteristics of high specific surface area and high Lewis acid content. The specific surface area of titania-silica composite aerogels can reach 524.59 m2/g, and the Lewis acid content on the surface can reach 370.29 µmol/g. Furthermore, the catalytic performance for the polycondensation reaction of PBS was investigated. The intrinsic viscosity of PBS synthesized by catalysis with the composite catalyst with a Ti/Si ratio of 9/1 reaches 1.74 dL/g, with the Mn of 7.72 × 104 g/mol. The hydrolysis resistance stability of the titania-silica composite aerogel is greatly improved compared with traditional tetrabutyl titanate (TBT), and the end carboxyl group content of PBS is effectively reduced to lower than 30 mol/ton.

Crack Evolution Behaviors and Bursting Liability of Sandstone with Different Sizes: An Experimental Study.

The size ranges of ore pillars play important roles in preventing the occurrences of rock burst phenomena. Due to the lack of research on the relationship between crack evolution behaviors and bursting liability of rocks with different sizes, uniaxial compression tests on sandstone with different height-to-diameter ratios (H/D) were conducted. The results showed that the mechanical parameters of sandstone have obvious size effects, in which both the peak strength and peak strain decrease with increases in the H/D. Moreover, the brittle index modified value (BIM) decreased, but the impact energy index increased gradually, which indicated the increase of bursting liability. With the increases in the BIM, the overall crack strain parameters increased, thereby indicating a positive correlation. With the increase in the impact energy index, the crack strain decreased and the bursting liability became higher. Although the axial crack closure stress and axial crack damage stress increased with the increases in BIM (indicating a positive correlation), the bursting liability became increasingly smaller. The crack stress decreased with the increases in the impact energy index, and the bursting liability became stronger. The findings of this study will potentially provide experimental references for furthering the current understanding of the mechanism of rock bursts in underground coal mines in China.

Thermal and UV light adaptive polyurethane elastomers for photolithography-transfer printing of flexible circuits.

Flexible polymers are widely used in the fields of wearable devices, soft robots, sensors, and other flexible electronics. Combining high strength and elasticity, electrical conductivity, self-healability, and surface tunable properties in one material becomes a challenge for designing polymeric materials for these applications, especially in flexible electronics. Herein, we propose a "two birds with one stone" strategy to synthesize thermal and UV light adaptive polyurethane elastomers with high-strength, self-healable, surface-modifiable and patternable functions for photolithography-transfer printing flexible circuits. The "stone", dihydroxybenzophenone, plays two roles in the synthesized polyurethanes as both a dynamic covalent bond and a UV-sensitive unit. On one hand, the phenolic group reacts with isocyanate to form a dynamic covalent phenol-carbamate bond, making the polymer self-healable, processable, and surface-embeddable with conductive fillers utilizing dynamic network rearrangement. On the other hand, the benzophenone group acts as a UV-sensitive unit to graft other functional groups to the polymer surface or self-crosslink on the surface under UV irradiation. Based on the dynamic covalent network and UV self-crosslinking properties, self-healable patterned flexible circuits can be obtained by photolithography-transfer printing. The flexible circuits prepared by loading silver nanowires on the dynamically crosslinked polyurethane substrate show little change of electric resistance when stretched up to 125% and can withstand thousands of stretching cycles.

Effects of Nonhydroxyl Oxygen Heteroatoms in Diethylene Glycols on the Properties of 2,5-Furandicarboxylic Acid-Based Polyesters.

With regard to polyesters based on biobased 2,5-furandicarboxylic acid (FDCA), our work presents a new strategy, heteroatom substitution, to adjust the thermal and gas barrier properties. The effects of nonhydroxyl oxygen heteroatoms in the diols on the properties of FDCA-based polyesters were first investigated by a combination of an experiment and molecular simulation. The results demonstrated that the introduction of oxygen heteroatoms significantly influenced the thermal and gas barrier properties. As for the two model polymers with a very similar skeleton structure, poly(pentylene 2,5-furandicarboxylate) (PPeF) and poly(diethylene glycol 2,5-furandicarboxylate) (PDEF), their Tg exhibited an obviously increasing order. Moreover, they showed similar thermal stability and thermal oxidative stability. Dynamic mechanical analysis, positron annihilation lifetime spectroscopy, and molecular dynamics simulation indicated that the gas barrier properties followed the sequence of PDEF > PPeF mainly due to the decreased chain mobility and smaller fractional free volume. In-depth analysis of the effects of heteroatom substitution has an important directive significance for the design and preparation of new high glass transition temperature or novel excellent gas barrier materials. Through the manipulation of different heteroatoms in the diols, the polyesters with varied properties can be expected.

Comparison of Three Interfacial Conductive Networks Formed in Carbon Black-Filled PA6/PBT Blends.

Interfacial localization of carbon fillers in cocontinuous-structured polymer blends is well-known as a high-efficiency strategy for conductive network formation. However, a comparison with interfacial localization of carbon fillers in sea-island-structured polymer blends is lacking. Here, three types of highly efficient conductive networks formed on the basis of interfacial localization of carbon black (CB) in polyamide 6 (PA6)/poly(butylene terephthalate) (PBT) blends with different blend compositions (80/20, 50/50 and 20/80 vol/vol) were investigated and compared in terms of electrical resistivity, morphology as well as rheological and mechanical properties. The order of the electrical percolation threshold of CB in the three blends is 50/50 < 20/80 < 80/20, which can be attributed to different network structures. The rheological percolation thresholds are close to the electrical ones, confirming the formation of CB networks. The formation mechanisms for the three types of CB network structures are analyzed. All the three types of PA6/PBT-6 vol% CB composites showed improved tensile strength compared with PA6/PBT blends, being in favor for practical applications.

Deciphering extrachromosomal circular DNA in Arabidopsis.

Extrachromosomal circular DNA (eccDNA) is independent of the chromosome and exists in many eukaryotes. However, the nature and origin of eccDNA in plants remains unclear. In this study, we sequenced 12 samples from four tissues (leaf, flower, stem and root) with three biological replicates. In total, we found 743 eccDNAs found in at least two samples. Most of eccDNA have inverted repeats ranging from 4 to 12 bp in the boundaries. Interestingly, eccDNA is not only related to transposon activity, but also hosts tRNA genes, suggesting that the eccDNAs may be associated with tRNA abundance which controls protein synthesis under conditions of stress. Our results provide an unprecedented view of eccDNA, which is still naïve in scope.

Novel Trilaminar Polymeric Antiadhesion Membrane Prevents Postoperative Pericardial Adhesion.

BACKGROUND: Postoperative pericardial adhesion formation is a prominent cause of morbidity and death in cardiovascular surgery, but there is still no ideal prevention method, especially in redo cases. This study investigated a novel antiadhesion trilaminar polymeric film compared with the Gore PRECLUDE Pericardial Membrane (W. L. Gore & Associates, Flagstaff, AZ) and a negative control. METHODS: Our novel trilaminar membrane is composed of polyvinyl alcohol (PVA) and carboxymethylcellulose (CMC). An established pericardial adhesion rabbit model was used to test the property of the membrane. After sternotomy, a portion of pericardium was resected and the epicardium was abraded. Rabbits (n = 24) were randomly assigned to 3 groups: control group, no trilaminar membrane or expanded polytetrafluoroethylene (ePTFE); ePTFE group, or trilaminar membrane group (PVA-CMC group). Evaluation of adhesion formation was performed by resternotomy 4 weeks after the operation. RESULTS: The degree of tissue adhesion surrounding the heart in the PVA-CMC group was significantly less than in the control (P < .01) and ePTFE (P < .05) groups. The inflammation score in group PVA-CMC was significantly lower than that in the ePTFE (P < .01) and control (P < .01) groups. The fibrosis score was significantly lower in group PVA-CMC than that in the ePTFE (P < .05) and control (P < .01) groups. CONCLUSIONS: The novel trilaminar membrane effectively reduced postoperative pericardial adhesions. The placement of the trilaminar membrane at the time of sternal closure provides a novel combination to minimize the extent and severity of pericardial adhesions while providing a physical barrier between the sternum and the cardiac structures.

Synthesis, Properties of Biodegradable Poly(Butylene Succinate-co-Butylene 2-Methylsuccinate) and Application for Sustainable Release.

A novel biobased and biodegradable polyester, i.e., poly(butylene succinate-co-butylene 2-methylsuccinate) (P(BS-BMS)) was synthesized by succinic acid (SA), 2-methylsuccinic acid (MSA), and 1,4-butanediol (BDO) via a typically two-step esterification and polycondensation procedure. The chemical structure and macromolecular weight of obtained copolymers were characterized by 1H NMR, 13C NMR, and GPC. The melting temperature and degree of crystallinity were also studied by DSC, and it was found that the values were gradually decreased with increasing of MSA content, while the thermal stability remained almost unchanged which was tested by TGA. In addition, the biodegradation rate of the P(BS-BMS) copolymers could be controlled by adjusting the ratio of SA and MSA, and such biodegradability could make P(BS-BMS) copolymers avoid microplastic pollution which may be brought to the environment for applications in agricultural field. When we applied P(BS-BMS) copolymers as pesticide carriers which were prepared by premix membrane emulsification (PME) method for controlling Avermectin delivery, an improvement of dispersion and utilization of active ingredient was obviously witnessed. It showed a burst release process first followed by a sustained release of Avermectin for a long period, which had a great potential to be an effective and environmental friendly pesticide-release vehicle.

Artemisia pollen allergy in China: Component-resolved diagnosis reveals allergic asthma patients have significant multiple allergen sensitization.

BACKGROUND: Artemisia pollen allergy is a major cause of asthma in Northern China. Possible associations between IgE responses to Artemisia allergen components and clinical phenotypes have not yet been evaluated. This study was to establish sensitization patterns of four Artemisia allergens and possible associations with demographic characteristics and clinical phenotypes in three areas of China. METHODS: Two hundred and forty patients allergic to Artemisia pollen were examined, 178 from Shanxi and 30 from Shandong Provinces in Northern China, and 32 from Yunnan Province in Southwestern China. Allergic asthma, rhinitis, conjunctivitis, and eczema symptoms were diagnosed. All patients' sera were tested by ImmunoCAP with mugwort pollen extract and the natural components nArt v 1, nArt ar 2, nArt v 3, and nArt an 7. RESULTS: The frequency of sensitization and the IgE levels of the four components in Artemisia allergic patients from Southwestern China were significantly lower than in those from the North. Art v 1 and Art an 7 were the most frequently recognized allergens (84% and 87%, respectively), followed by Art v 3 (66%) and Art ar 2 (48%). Patients from Northern China were more likely to have allergic asthma (50%) than patients from Southwestern China (3%), and being sensitized to more than two allergens increased the risk of allergic asthma, in which co-sensitization to three major allergens Art v 1, Art v 3, and Art an 7 is prominent. CONCLUSIONS: Component-resolved diagnosis of Chinese Artemisia pollen-allergic patients helps assess the potential risk of mugwort-associated allergic asthma.

Nevirapine-polycaprolactone crystalline inclusion complex as a potential long-acting injectable solid form.

Nevirapine (NVP) is recommended by WHO as the antiretroviral treatment to prevent HIV passing from mother to child. However, the once-daily oral administration results in poor patient compliance, and a long-acting injectable form of NVP is desirable. Using single-crystal X-ray diffraction and other characterization methods, we demonstrated NVP can form crystalline inclusion complex (IC) with the biodegradable hydrophobic poly(ε-caprolactone) (PCL), and investigated the potential of the NVP-PCL IC microparticles as a long-acting injectable solid form. Compared with pure NVP crystals and NVP/polylactide microparticles, the NVP-PCL IC crystals showed significantly decreased solubility and slower dissolution rate, making it more suitable to be developed to achieve sustained-release profiles. In addition, the NVP-PCL IC microparticles with an average diameter below 10 µm can be conveniently prepared by spray drying and are found to be easily injectable through a 25G needle. These results demonstrated the possibility of using drug-polymer IC microparticles as long-acting injectable forms, providing a new approach to design sustained-release drug products.

Preparation and Characterization of Poly(butylene succinate)/Polylactide Blends for Fused Deposition Modeling 3D Printing.

To obtain a new type of biodegradable material with high toughness and strength used for fused deposition modeling (FDM) printing, a series of poly(butylene succinate) (PBS)-based polymer materials was prepared via blending with polylactide (PLA). The rheological, thermal, and mechanical properties as well as FDM printing performances of the blends, such as distortion, cross section, and the interlayer bond strength, were characterized. The results show that with increasing PLA content, the blends possess higher melt viscosity, larger tensile strength, and modulus, which are more suitable for FDM printing. Especially, when the content of PLA is more than 40%, distortion due to residual stress caused by volume shrinkage disappears during the printing process and thus products with good dimensional accuracy and pearl-like gloss are obtained. The results demonstrate that the blend compositions with moderate viscosity, low degree of crystallinity, and high modulus are more suitable for FDM printing. Compared with the low elongation upon breaking of commercially FDM-printed material, the PBS/PLA blend materials exhibit a typical ductile behavior with elongation of 90-300%. Therefore, besides biodegradability, the PBS/PLA blends present excellent mechanical properties and suitability as materials for FDM printing. In addition, our study is expected to provide methods for valuating the suitability of whether a thermoplastic polymer material is suitable for FDM printing or not.

Copolymerization with Polyether Segments Improves the Mechanical Properties of Biodegradable Polyesters.

To improve the properties of poly(butylene succinate) (PBS), a series of poly[(butylene succinate)-co-poly(tetramethylene glycol)]s (PBSTMGs) with different poly(tetramethylene glycol) (PTMG) contents were successfully prepared by the catalyzed melt polycondensation process. The effect of introducing flexible PTMG segments on the properties was investigated, and they were compared to those of PBS. The differential scanning calorimetry results indicated that the melting temperature, crystallization temperature, and crystallinity of PBSTMG copolymers were slightly lower than those of PBS. Furthermore, these thermal parameters decreased gradually with the increase of PTMG content. Dynamic mechanical analysis showed that there was a significant decline of storage modulus (E') in the overall temperature range of copolymers compared to that of PBS. The incorporation of PTMG did not modify the crystal lattice of PBS according to the wide-angle X-ray diffraction analysis. Because of copolymerization, the size of the spherulites was reduced at high PTMG contents. The soft domain in the copolymers might contribute to the enhanced tear strength of PBSTMG. The elongation at break and impact strength of PBSTMG copolymers were greatly improved as a result of the phase separation structure and lower degree of crystallinity. Especially, when the PTMG content was 10 mol %, the impact strength of the copolymer reached up to 4.5 times that of PBS. In addition, with more soft segments introduced, the biodegradability of the copolymers became much better than that of PBS.

An in situ-forming zwitterionic hydrogel as vitreous substitute.

Zwitterionic polymers have shown ultra-low biofouling properties at surfaces and excellent biocompatibility as implant. In this study, an in situ-forming zwitterionic hydrogel was designed and evaluated, both in vitro and in vivo, as a long-term vitreous substitute. The zwitterionic polymer poly(MPDSA-co-AC) was designed as a copolymer of the sulfobetaine methacrylamide and acryloyl cystamine monomers, providing the zwitterionic components and the thiol functional groups, respectively. The in situ gelation was via the thiol-ene Michael addition reaction with α-PEG-MA as the crosslinker. The gelation time, rheological properties, swelling profiles, and the transparency of zwitterionic hydrogels were studied in detail. Two systems with different crosslinker concentrations were tested in a rabbit model, and the one with the thiol-ene ratio of 2 : 1 showed excellent biocompatibility in vivo, formed space-filling hydrogels and remained transparent in the vitreous cavity for the 2 month implantation period. Therefore, in situ-forming zwitterionic hydrogels represent a promising material system as a vitreous substitute and possibly for other soft tissue replacements.

Novel membrane-based biotechnological alternative process for succinic acid production and chemical synthesis of bio-based poly (butylene succinate).

Succinic acid was produced in a novel membrane-based fermentation and separation integrated system. With this integrated system, product inhibition was alleviated by removing acids and replenishing fresh broth. High cell density maintain for a longer time from 75 to 130h and succinic acid concentration increased from 53 to 73g/L. In the developed separation process, succinic acid was crystallized at a recovery of 85-90%. The purity of the obtained succinic acid crystals reached 99.4% as found by HPLC and (1)H NMR analysis. A crystallization experiment indicated that among by-products glucose had a negative effect on succinic acid crystallization. Poly (butylene succinate) (PBS) was synthesized using the purified succinic acid and (1)H NMR analysis confirmed that the composition of the synthesized PBS is in agreement with that from petro-based succinic acid.

Evaluation of an in situ chemically crosslinked hydrogel as a long-term vitreous substitute material.

Currently there is no material that can be used as a long-term vitreous substitute, and this remains an unmet clinical need in ophthalmology. In this study, we developed an injectable, in situ chemically crosslinked hydrogel system and evaluated it in a rabbit model. The system consisted of two components, both based on multi-functional poly(ethylene glycol) (PEG) but with complementarily reactive end groups of thiol and active vinyl groups, respectively. The two components are mixed and injected as a solution mixture, react in vivo via the Michael addition route and form a chemically crosslinked hydrogel in situ. The linkages between the end groups and the backbone PEG chains are specially designed to ensure that the final network structure is hydrolysis-resistant. In the rabbit study and with an optimized operation protocol, we demonstrated that the hydrogel indeed formed in situ after injection, and remained transparent and stable during the study period of 9 months without significant adverse reactions. In addition, the hydrogel formed in situ showed rheological properties very similar to the natural vitreous. Therefore, our study demonstrated that this in situ chemically crosslinked PEG gel system is suitable as a potential long-term vitreous substitute.

Toward the synthesis of sequence-controlled vinyl copolymers.

An ATRA based strategy to synthesize vinyl copolymers with monomer-level sequence control is proposed. In each cycle, one allyl alcohol is added to the ATRP chain end, and then the hydroxymethyl residue is oxidized to carboxylic acid and a side group is introduced via esterification, making the new chain end active for the next cycle.