Switchable catalysis improves the properties of CO2-derived polymers: poly(cyclohexene carbonate-b-ε-decalactone-b-cyclohexene carbonate) adhesives, elastomers, and toughened plastics

Carbon dioxide/epoxide copolymerization is an efficient way to add value to waste CO2 and to reduce pollution in polymer manufacturing. Using this process to make low molar mass polycarbonate polyols is a commercially relevant route to new thermosets and polyurethanes. In contrast, high molar mass polycarbonates, produced from CO2, generally under-deliver in terms of properties, and one of the most widely investigated, poly(cyclohexene carbonate), is limited by its low elongation at break and high brittleness. Here, a new catalytic polymerization process is reported that selectively and efficiently yields degradable ABA-block polymers, incorporating 6–23 wt % CO2. The polymers are synthesized using a new, highly active organometallic heterodinuclear Zn(II)/Mg(II) catalyst applied in a one-pot procedure together with biobased ε-decalactone, cyclohexene oxide, and carbon dioxide to make a series of poly(cyclohexene carbonate-b-decalactone-b-cyclohexene carbonate) [PCHC-PDL-PCHC]. The process is highly selective (CO2 selectivity >99% of theoretical value), allows for high monomer conversions (>90%), and yields polymers with predictable compositions, molar mass (from 38–71 kg mol–1), and forms dihydroxyl telechelic chains. These new materials improve upon the properties of poly(cyclohexene carbonate) and, specifically, they show good thermal stability (Td,5 ∼ 280 °C), high toughness (112 MJ m–3), and very high elongation at break (>900%). Materials properties are improved by precisely controlling both the quantity and location of carbon dioxide in the polymer chain. Preliminary studies show that polymers are stable in aqueous environments at room temperature over months, but they are rapidly degraded upon gentle heating in an acidic environment (60 °C, toluene, p-toluene sulfonic acid). The process is likely generally applicable to many other lactones, lactides, anhydrides, epoxides, and heterocumulenes and sets the scene for a host of new applications for CO2-derived polymers

Assessment of Shoreline Changes using Historical Satellite Images and Geospatial Analysis along the Lake Salda in Turkey

WOS: 000527535700001This study was performed along the shorelines of Lake Salda in Turkey during the elapsed period from 1975 to 2019 in order to detect shoreline changes. Within this framework, geographic information system, digital shoreline analysis system, Modified Normalized Difference Water Index, and multi-temporal satellite images were utilized. The measurement of shoreline displacement was mainly divided into six analysis regions. In digital shoreline analysis system, several statistical parameters such as end point rate, linear regression rate, shoreline change envelope, and net shoreline movement were computed to measure the rates of shoreline displacement in terms of erosion and accretion. The maximum shoreline change between 1975 and 2019 was determined as 556.45 m by shoreline change envelope parameter. The maximum shoreline change was 16.35 m/year by end point rate parameter and 12.91 m/year by linear regression rate parameter. While erosion has been observed in 3rd, 4th and 6th segments, accretion has been observed in other segments. When all the transects were taken into consideration, an accretion observed. The results indicate that there is a decrease in area of the lake. Experiment results show that integrated use of multi-temporal satellite images and statistical parameters are very effective and useful for shoreline change analysis. It is thought that the structures such as irrigation pond and dam that are built on the streams that recharge the lake and average rainfall and average temperature conditions are the main reasons of the fluctuations and changes in the shorelines