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Liquid epoxy resins have received much attention from both academia and the chemical industry as eco-friendly volatile organic compound (VOC)-free alternatives for applications in coatings and adhesives, especially in those used in households. Epoxy resins show high chemical resistance and high creep resistance. However, due to their brittleness and lack of thermal stability, additional fillers are needed for improving the mechanical and thermal properties. Halloysite nanotubes (HNTs) are naturally abundant, inexpensive, and eco-friendly clay minerals that are known to improve the mechanical and thermal properties of epoxy composites after suitable surface modification. Zirconium is well known for its high resistance to heat and wear. In this work, zirconium oxide-impregnated HNTs (Zr/HNTs) were added to epoxy resins to obtain epoxy composites with improved mechanical and thermal properties. Zr/HNTs were characterized by field-emission transmission electron microscopy, transmission electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Changes in the thermal properties of the epoxy composites were characterized by thermo mechanical analysis and differential scanning calorimetry. Furthermore, flexural properties of the composites were analyzed using a universal testing machine.

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.

A vinyl-containing macroinimer was prepared in situ by utilizing sulfoxide chemistry in an unprecedented manner and allowed for the one-pot synthesis of hyperbranched polymers. Sulfoxide-protected haloalkanes were prepared, and their transformation into vinyl-functionalized haloalkanes through sulfoxide elimination under various reaction conditions was investigated. The protected haloalkanes were employed as an initiator for supplemental activator and reducing agent atom transfer radical polymerization (SARA ATRP) in a diluted catalytic system to prepare polymers with a high chain-end functionality at a relatively low temperature. Subsequent thermal treatment yielded the macroinimers while preserving the high chain-end functionalities. When the temperature was elevated during the linear polymerization, hyperbranched polymers were afforded in a one-pot process via the in situ generations of the macroinimers. A detailed investigation revealed that the sulfoxide-modified ATRP initiator to protect the vinyl functionality on the polymer chain was successfully utilized for the synthesis of the hyperbranched polymer. This strategy is expected to aid in the synthesis of hyperbranched polymers with a tunable distance between the branch points.

Introduction of an additional donor, by tethering substituted pyridine, in the alkylidene ligand of a NHC-based ruthenium complex initiates latent olefin metathesis polymerization.

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