As an on-going project to synthesise the copolymers of epoxides with carbon dioxide, the ternary polymerisation of propylene oxide and ethylene oxide with carbon dioxide was investigated using an anaerobic system. The terpolymerisation of propylene oxide and ethylene oxide with carbon dioxide was carried out with supported zinc glutarate catalyst, consequently producing high molecular weight poly(propylene-ethylene carbonate) (PPEC). The structure and properties of PPEC were studied by means of gel permeation chromatographic (GPC) analysis, Fourier Transform infrared (FTIR), nuclear magnetic resonance (NMR) spectroscopy, different scanning calorimetry (DSC), and thermogravimetric analysis (TGA) techniques. NMR and FTIR results showed that the terpolymer PPEC was a polycarbonate consisting of propylene carbonate and ethylene carbonate together with random ether linkages. The glass transition temperature (Tg) of the terpolymers decreased with increasing ethylene oxide (EO) content. TGA analysis indicated high thermal stability for the synthesised terpolymer.
Lake geo-engineering such as submerged macrophyte restoration
is
generally applied to re-establish the biological components of aquatic
systems and recover the ecological functions of eutrophic shallow
lakes. Research on the long-term spatiotemporal variations in plankton
and their correlations with environmental variables after submerged
macrophyte restoration is limited. Plankton in the West Lake, Hangzhou,
Zhejiang Province, China, was monitored on a monthly basis, and the
main factors and relative contributions of environmental variables
to phytoplankton were determined using quantitative analyses after
lake geo-engineering. Dominant phytoplankton phyla exhibited a gradual
decline along with submerged macrophyte restoration, and the composition
changed to a more evenly distributed status on a long-term scale.
Zooplankton populations sustainably increased during the initial period
of submerged macrophyte restoration, and then gradually decreased
until the composition sustained a stable status. Owing to lake geo-engineering,
significant spatiotemporal variations in phytoplankton were attributed
to the large submerged macrophyte distribution, water diversion project,
and seasonal change. Spearman correlation analysis results illustrated
that submerged macrophyte characteristics, especially Vallisneria natans, which was the species with the
highest distribution in the West Lake, strongly affected the dominant
phytoplankton. Comparison of ecological indices including abiotic
and biotic factors in the monitoring survey revealed that submerged
macrophytes were responsible for re-establishing a preferable aquatic
system. The core effect of submerged macrophytes in the aquatic system
could be explained by the interactions between environmental variables,
whereby submerged macrophytes affected phytoplankton growth by releasing
allelochemicals and altering water nutrient levels, sediment, and
zooplankton communities. Therefore, our findings offer new evidence
on the vital ecological functions of submerged macrophytes in a typical
subtropical shallow urban lake under increasing anthropogenic pressure.
The Original article has been corrected.Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.