Novel Reactive Polyhedral Oligomeric Silsesquioxane-Reinforced and Toughened Epoxy Resins for Advanced Composites.

Most toughening methods for epoxy resins are usually used at the expense of other properties. Some polyhedral oligomeric silsesquioxanes (POSSs) with both a rigid Si-O-Si structure and flexible organic chain segments could be expected to be effective toughening agents. In this study, three reactive polyhedral oligomeric silsesquioxanes with a thiol group (OMPPS), a carboxyl group (OCOPS), and an epoxy group (OGCPS) were synthesized and characterized.

High-Performance Reversible Furan-Maleimide Resins Based on Furfuryl Glycidyl Ether and Bismaleimides.

Two reversible furan-maleimide resins, in which there are rigid -Ph-CH-Ph- structures and flexible -(CH)- structures in bismaleimides, were synthesized from furfuryl glycidyl ethers (FGE), 4,4'-diaminodiphenyl ether (ODA), ,'-4,4'-diphenylmethane-bismaleimide (DBMI), and -hexamethylene-bismaleimide (HBMI). The structures of the resins were confirmed using Fourier transform infrared analysis, and the thermoreversibility was evidenced using differential scanning calorimetry (DSC) analysis, as well as the sol-gel transformation process. Mechanical properties and recyclability of the resins were preliminarily evaluated using the flexural test.

Effects of pendant side groups on the properties of the silicon-containing arylacetylene resins with 2,5-diphenyl-[1,3,4]-oxadiazole moieties.

Silicon-containing arylacetylene resins with rigid conjugated structures in the main chain often exhibit poor processability. A strategy of improving the processability by destroying the molecular structure symmetry using side aromatic groups was proposed, and the effects of the side groups was further explored. Two novel structural resins with side aromatic phenyl and phenylacetylene groups (PODSA-2P-MM and PODSA-2E-MM) were synthesized by Grignard reaction.

Effect of the Crosslinking Degree on Self-Healing Poly(1,2,3-Triazolium) Adhesive.

Dynamic covalent materials are a class of polymer that could be stress-relaxation, reprocessable, and self-healing due to dynamic crosslinks in network. Dynamic crosslinks play an important role in the typical characteristic of self-healing polymers. It is meaningful to understand the effect of crosslinking degree on the properties of poly(1,2,3-triazolium) (PTAM).

Synthesis and Characterization of Block Copolymers of Poly(silylene diethynylbenzen) and Poly(silylene dipropargyl aryl ether).

Poly(silylene diethynylbenzene)--poly(silylene dipropargyloxy diphenyl propane) copolymer (ABA-A), poly(silylene diethynylbenzene)--poly(silylene dipropargyloxy diphenyl ether) copolymer (ABA-O), and a contrast poly(silylene diethynylbenzene) with equivalent polymerization degree were synthesized through Grignard reactions. The structures and properties of the copolymers were investigated via hydrogen nuclear magnetic resonance, Fourier transform infrared spectroscopy, Haake torque rheometer, differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis and mechanical tests. The results show that the block copolymers possess comprehensive properties, especially good processability and good mechanical properties.

High impact polytriazole resins for advanced composites.

Three azido-terminated poly(ethylene glycol) macromonomers (ATPEGs) were synthesized from poly(ethylene glycol)s (PEGs) and characterized. The extended polytriazole (EPTA) resins were prepared from the macromonomers, azide and alkyne monomers. Toughening effect of PEGs on polytriazole resins was analyzed by means of mechanical, thermal and electronic microscope characterization.

Automatically Programmable Shape-Memory Polymers Based on Asymmetric Swelling of Bilayer Structures.

Shape-memory polymers (SMPs) possess the capability to change shapes upon stimulation; however, the programming process that determines the temporary shape cannot proceed without external manipulation, which may greatly affect the shape complexity, accuracy, and reproducibility. Here, an automatically programmable SMP (AP-SMP) based on asymmetric swelling of bilayer SMP structures is demonstrated without external manipulation. In the automatic programming process, the AP-SMP can be deformed by the swelling of its hydrophilic hinge film in warm water to a temporary shape, which could be fixed by the glass transition of the two SMP films through cooling and drying in air.

Novolac-based poly(1,2,3-triazolium)s with good ionic conductivity and enhanced CO permeation.

Novolac-based poly(1,2,3-triazolium)s with 1,2,3-triazolium side groups spaced by oligo(ethylene glycol), a new kind of poly(ionic liquid) membrane, was prepared the well-known Click chemistry (1,3-dipolar cycloaddition reaction). The thermal properties, ionic conductivity and gas permeation performance of these self-standing membranes were investigated. The obtained membranes exhibit glass transition temperatures ranging from -1 °C to -7.

Dynamics of soil carbon and nitrogen stocks after afforestation in arid and semi-arid regions: A meta-analysis.

Arid and semi-arid regions store approximately 27% of global soil organic carbon (SOC), thus playing an important role in the global carbon cycle. Although afforestation is widely used to achieve the goals of landscape protection and ecological restoration in these regions, its effects on the dynamics of SOC and total nitrogen (TN) stocks as well as the related controlling factors are still poorly understood. In this study, a meta-analysis was conducted by compiling results from published studies to evaluate the influences of afforestation on dynamics of SOC and TN stocks in mineral soils (0-30cm) in arid and semi-arid regions, and to examine whether the changes in SOC and TN stocks were influenced by prior land-use, planted tree species and plantation age.