Metal-containing ionic liquids possessing bifunctional moieties were identified as efficient catalysts for the synthesis of propylene carbonate (PC) from CO 2 and propylene oxide under moderate and solvent free conditions. Density functional theory calculations were performed to rationalize the difference in catalytic activities of the metalcontaining ionic liquid catalysts (MeIm) 2 MCl 2 , where M was Fe, Cu, or Zn. (MeIm) 2 ZnCl 2 was the most efficient catalyst for the chemical fixation of carbon dioxide in terms of efficiency and environmental benignity. Process optimization using response surface methodology was performed, and the interactions between the operational variables were elucidated. The optimum reaction conditions for maximum PC yield were 4.6 h, 124 °C, and 9 bar which were obtained by a Box−Behnken design with the minimum number of reaction tests. Under the optimum reaction conditions, the predicted and validated yields of PC were 98.37 and 97.91 ± 0.02%, respectively.
Latent olefin metathesis polymerization
catalysts have enormous
potential, as they provide access to thermoset polymers. However,
developing a novel latent catalyst is difficult because the catalyst
must be inactive at room temperature and completely convert the starting
material to the product upon activation. Herein, we report the synthesis
of a series of novel initiators 1–4 bearing an additional hydrogen donor that can form a weak hydrogen
bond with the metal-bound chloride anion of the active species of
an alkylidene-containing N-heterocyclic carbene (NHC)-Ru-based initiator,
and their latent catalytic behavior was examined in the ring-opening
olefin metathesis polymerization (ROMP) of dicyclopentadiene (DCPD)
and cyclooctadiene (COD). The presence of intramolecular hydrogen
bonds in initiators 1 and 2 facilitates
latent polymerization, whereas the absence of intramolecular hydrogen
bonds in initiators 3 and 4 allowed polymerization
of DCPD at 30 °C. The TGA and DSC results for poly-DCPD (PDCPD)
suggest that the intramolecular hydrogen bonding in initiators 1 and 2 did not alter the nature of the NHC-Ru-based
initiator at 80 °C.
Epoxy resins are widely applicable in the aircraft, automobile, coating, and adhesive industries because of their good chemical resistance and excellent mechanical and thermal properties. However, upon external impact, the crack propagation of epoxy polymers weakens the overall impact resistance of these materials. Therefore, many impact modifiers have been developed to reduce the brittleness of epoxy polymers. Polyurethanes, as impact modifiers, can improve the toughness of polymers. Although it is well known that polyurethanes (PUs) are phase-separated in the polymer matrix after curing, connecting PUs to the polymer matrix for enhancing the mechanical properties of polymers has proven to be challenging. In this study, we introduced epoxy functional groups into polyol backbones, which is different from other studies that focused on modifying capping agents to achieve a network structure between the polymer matrix and PU. We confirmed the molecular weight of the prepared PU via gel permeation chromatography. Moreover, the prepared material was added to the epoxies and the resulting mechanical and thermal properties of the materials were evaluated. Furthermore, we conducted tensile, flexural strength, and impact resistance measurements. The addition of PU to the epoxy compositions enhanced their impact strength and maintained their mechanical strength up to 10 phr of PU. Furthermore, the morphologies observed with field emission scanning electron microscopy and transmission electron microscopy proved that the PU was phase separated in the epoxy matrix.
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