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The development of new chemically recyclable polymers via monomer design would provide a transformative strategy to address the energy crisis and plastic pollution problem. Biaryl‐fused cyclic esters were targeted to generate axially chiral polymers, which would impart new material performance. To overcome the non‐polymerizability of the biaryl‐fused monomer DBO, a cyclic ester Me‐DBO installed with dimethyl substitution was prepared to enable its polymerizability via enhancing torsional strain. Impressively, Me‐DBO readily went through well‐controlled ring‐opening polymerization, producing polymer P(Me‐DBO) with high glass transition temperature (Tg >100 °C). Intriguingly, mixing these complementary enantiopure polymers containing axial chirality promoted a transformation from amorphous to crystalline material, affording a semicrystalline stereocomplex with a melting transition temperature more than 300 °C. P(Me‐DBO) were capable of depolymerizing back to Me‐DBO in high efficiency, highlighting an excellent recyclability. [ABSTRACT FROM AUTHOR]

The development of new chemically recyclable polymers via monomer design would provide a transformative strategy to address the energy crisis and plastic pollution problem. Biaryl‐fused cyclic esters were targeted to generate axially chiral polymers, which would impart new material performance. To overcome the non‐polymerizability of the biaryl‐fused monomer DBO, a cyclic ester Me‐DBO installed with dimethyl substitution was prepared to enable its polymerizability via enhancing torsional strain. Impressively, Me‐DBO readily went through well‐controlled ring‐opening polymerization, producing polymer P(Me‐DBO) with high glass transition temperature (Tg >100 °C). Intriguingly, mixing these complementary enantiopure polymers containing axial chirality promoted a transformation from amorphous to crystalline material, affording a semicrystalline stereocomplex with a melting transition temperature more than 300 °C. P(Me‐DBO) were capable of depolymerizing back to Me‐DBO in high efficiency, highlighting an excellent recyclability. [ABSTRACT FROM AUTHOR]

The development of chemically recyclable polymers serves as an attractive approach to address the global plastic pollution crisis. Monomer design principle is the key to achieving chemical recycling to monomer. Herein, we provide a systematic investigation to evaluate a range of substitution effects and structure−property relationships in the ɛ-caprolactone (CL) system. Thermodynamic and recyclability studies reveal that the substituent size and position could regulate their ceiling temperatures (Tc). Impressively, M4 equipped with a tert-butyl group displays a Tc of 241 °C. A series of spirocyclic acetal-functionalized CLs prepared by a facile two-step reaction undergo efficient ring-opening polymerization and subsequent depolymerization. The resulting polymers demonstrate various thermal properties and a transformation of the mechanical performance from brittleness to ductility. Notably, the toughness and ductility of P(M13) is comparable to the commodity plastic isotactic polypropylene. This comprehensive study is aimed to provide a guideline to the future monomer design towards chemically recyclable polymers. The global plastic pollution crisis can be mitigated by developing chemically recyclable polymers following the monomer design principle. Here, the authors evaluate substitution effects and structure−property relationships in the ɛ-caprolactone system to guide the design of monomers for the preparation of chemically recyclable polymers. [ABSTRACT FROM AUTHOR]

The development of innovative synthetic polymer systems to overcome the trade‐offs between the polymer's depolymerizability and performance properties is in high demand for advanced material applications and sustainable development. In this contribution, we prepared a class of aromatic cyclic esters (M1–M5) from thiosalicylic acid and epoxides by facile one‐pot synthesis. Ring‐opening polymerization of Ms afforded aromatic polyesters P(M)s with high molecular weights and narrow dispersities. The physical and mechanical properties of P(M)s can be modulated by stereocomplexation and regulation of the side‐chain flexibility of the polymers, ultimately achieving high‐performance properties such as high thermal stability and crystallinity (Tm up to 209 °C), as well as polyolefin‐like high mechanical strength, ductility, and toughness. Furthermore, the functionalizable moieties of P(M)s have driven a wide array of post‐polymerization modifications toward access to value‐added materials. More importantly, the P(M)s were able to selectively depolymerize into monomers in excellent yields, thus establishing its circular life cycle. [ABSTRACT FROM AUTHOR]

The development of innovative synthetic polymer systems to overcome the trade‐offs between the polymer's depolymerizability and performance properties is in high demand for advanced material applications and sustainable development. In this contribution, we prepared a class of aromatic cyclic esters (M1–M5) from thiosalicylic acid and epoxides by facile one‐pot synthesis. Ring‐opening polymerization of Ms afforded aromatic polyesters P(M)s with high molecular weights and narrow dispersities. The physical and mechanical properties of P(M)s can be modulated by stereocomplexation and regulation of the side‐chain flexibility of the polymers, ultimately achieving high‐performance properties such as high thermal stability and crystallinity (Tm up to 209 °C), as well as polyolefin‐like high mechanical strength, ductility, and toughness. Furthermore, the functionalizable moieties of P(M)s have driven a wide array of post‐polymerization modifications toward access to value‐added materials. More importantly, the P(M)s were able to selectively depolymerize into monomers in excellent yields, thus establishing its circular life cycle. [ABSTRACT FROM AUTHOR]

From August 21, 2000 to October 20, 2000 a fluid injection-induced seismicity experiment has been carried out in the KTB (German Continental Deep Drilling Program). The KTB seismic network recorded more than 2 700 events. Among them 237 events were of high signal-to-noise ratio, and were processed and accurately located. When the events were located, non KTB events were weeded out by Wadati’s method. The standard deviation, mean and median were obtained by Jackknife’s technique, and finally the events were accurately located by Geiger’s method so that the mean error is about 0.1 km. No earthquakes with focal depth greater than 9.3 km, which is nearly at the bottom of the hole, were detected. One of the explanation is that at such depths the stress levels may not close to the rock’s frictional strength so that failure could not be induced by the relatively small perturbation in pore pressure. Or at these depths there may be no permeable, well-oriented faults. This depth may be in close proximity to the bottom of the hole to the brittle-ductile transition, even in this relatively stable interior of the interaplate. This phenomenon is explained by the experimental results and geothermal data from the superdeep borehole. [ABSTRACT FROM AUTHOR]

Using the technique of seismic moment tensor inversion, the source mechanisms of 10 earthquakes with M s≥5,2 that occurred in China from November 1996 to January 1998 were determined rapidly. The determined results were sent as “Bulletins of Source Mechanism Parameters of Earthquakes” to the Seismic Regime Guards’ Office, China Seismological Bureau, and the relevant provincial seismological bureaus. These bulletins have played role in the fast response to large earthquakes. [ABSTRACT FROM AUTHOR]