Solvent-Free Acid-Catalyzed Ring-Opening of Epoxidized Oleochemicals Using Stearates/Stearic Acid, and Its Applications

Toxic solvent and strong acid catalysts causing environmental issues have been mainly used for ring-opening of epoxidized oleochemicals. Here, we demonstrated that magnesium stearate (Mg-stearate) was a high efficient catalyst for solvent-free ring-opening of epoxidized methyl oleate, a model compound of midchain epoxide. Mg-stearate resulted in the highest yield (95%) and conversion rate (99%) toward midchain alkoxyesters under the same conditions (160 °C, 12 h) superior to other fatty acid derivatives such as a Lewis acid (lithium and sodium stearate) and Brønsted acid (stearic acid). Based on this chemical study, we synthesized biogrease and thermoplastic using epoxidized soybean oil (ESO) and Mg-stearate via one-pot, solvent-free, and purification-free process. Mg-stearate played a significant role as a reactant for epoxide ring-opening and as a thickener when excess loading rate was used; viscosity increased from 1800 to 4500 Pa·s at 25 °C when ESO:Mg-stearate increased from 1:1 equiv to 1:2, then behaved like thermoplastics (Tg = −27 °C, Tm = 90 °C) with 1:4

Eugenol-Derived Molecular Glass: A Promising Biobased Material in the Design of Self-Healing Polymeric Materials

One kind of molecular glass material was prepared via the epoxidation of eugenol and a subsequent thermochemical conversion process. This biobased molecular glass (ET-eugenol) shows high potential in the design of self-healing materials while being incorporated into a polymeric matrix to form a multiphase system. Here, an ET-eugenol/polymerized soybean oil (p-ESO) system with a mass ratio of 1:2 was investigated. Results show that the scratch damage can be healed effectively at a temperature of 90 °C within 15 min or by ultraviolet radiation within seconds. Good dimension stability even at high temperatures can be kept in the whole healing process. A mechanical tensile test shows that compared to the neat p-ESO matrix the incorporation of ET-eugenol (weight percent of 33%) led to a 2.7-fold increase in ultimate stress and a healing efficiency up to 88%. Gel permeation chromatography, nuclear magnetic resonance, and gas chromatography–mass spectrometer were carefully conducted to reveal the complex thermochemical reaction during the preparation process of ET-eugenol. Self-healing behaviors were characterized via atomic force microscope and optical images, and the corresponding healing mechanism was discussed from a multiphase structural viewpoint. The work reported here demonstrates the possibility of molecular glass as a promising candidate in the design of self-healing materials

Competitive Nucleophilic Attack Chemistry Based on Undecenoic Acid: A New Chemical Route for Plant-Oil-Based Epoxies

Plant oil is one of the world’s most abundant renewable resources; however, its derived epoxies are low in thermal resistance and mechanical strength. In this work, a new chemical route referred to “competitive nucleophilic attack (CNA)” was discovered to achieve plant-oil-based epoxy with high thermal resistance and mechanical strength as well as many other unique properties comparable to those of diglycidyl ether of bisphenol A (DGEBA), one of the most popular petroleum-based epoxies. The CNA route was realized by using 10-undecenoic acid (UA), a plant-derived monomer, as a building block reacting with alicyclic oxirane chemicals, such as 4-ethenyl-7-oxabicyclo[4.1.0]­heptanes (ECP), to achieve epoxy monomers with ether-bridged cycloaliphatic ring structure. A newly formed hydroxyl (NFH) is involved in the nucleophilic attack upon oxonium to compete with UA anion during the UA–ECP reaction. The resultant epoxy is UV-curable in a few seconds, possessing high tensile strength (∼48 MPa), high glass transition temperature (∼142 °C), high transparency (∼90%), as well as low viscosity (∼1.9 Pa s). These properties are superior to the plant-oil-based epoxies published and comparable to or better than commercial DGEBA. Structure analysis revealed that the ether-bridged cycloaliphatic ring structure via the CNA route played a key role in maximizing the network performance. With the CNA feature, chain structure can be further regulated via introducing a methyl group to hinder the NFH nucleophilic attack, achieving a conversion of epoxy resin from rigid to semiductile. This finding suggests that CNA strategy could be a new direction for the design of biobased epoxies using all possible chemicals with acid–alkene structures from various renewable resources rather than plant oils only

Effective Infiltration of Gel Polymer Electrolyte into Silicon-Coated Vertically Aligned Carbon Nanofibers as Anodes for Solid-State Lithium-Ion Batteries

This study demonstrates the full infiltration of gel polymer electrolyte into silicon-coated vertically aligned carbon nanofibers (Si-VACNFs), a high-capacity 3D nanostructured anode, and the electrochemical characterization of its properties as an effective electrolyte/separator for future all-solid-state lithium-ion batteries. Two fabrication methods have been employed to form a stable interface between the gel polymer electrolyte and the Si-VACNF anode. In the first method, the drop-casted gel polymer electrolyte is able to fully infiltrate into the open space between the vertically aligned core–shell nanofibers and encapsulate/stabilize each individual nanofiber in the polymer matrix. The 3D nanostructured Si-VACNF anode shows a very high capacity of 3450 mAh g^–1 at C/10.5 (or 0.36 A g^–1) rate and 1732 mAh g^–1 at 1C (or 3.8 A g^–1) rate. In the second method, a preformed gel electrolyte film is sandwiched between an Si-VACNF electrode and a Li foil to form a half-cell. Most of the vertical core–shell nanofibers of the Si-VACNF anode are able to penetrate into the gel polymer film while retaining their structural integrity. The slightly lower capacity of 2800 mAh g^–1 at C/11 rate and ∼1070 mAh g^–1 at C/1.5 (or 2.6 A g^–1) rate have been obtained, with almost no capacity fade for up to 100 cycles. Electrochemical impedance spectroscopy does not show noticeable changes after 110 cycles, further revealing the stable interface between the gel polymer electrolyte and the Si-VACNFs anode. These results show that the infiltrated flexible gel polymer electrolyte can effectively accommodate the stress/strain of the Si shell due to the large volume expansion/contraction during the charge–discharge processes, which is particularly useful for developing future flexible solid-state lithium-ion batteries incorporating Si-anodes

Mesoporous Hybrids of Reduced Graphene Oxide and Vanadium Pentoxide for Enhanced Performance in Lithium-Ion Batteries and Electrochemical Capacitors

Mesoporous hybrids of V₂O₅ nanoparticles anchored on reduced graphene oxide (rGO) have been synthesized by slow hydrolysis of vanadium oxytriisopropoxide using a two-step solvothermal method followed by vacuum annealing. The hybrid material possesses a hierarchical structure with 20–30 nm V₂O₅ nanoparticles uniformly grown on rGO nanosheets, leading to a high surface area with mesoscale porosity. Such hybrid materials present significantly improved electronic conductivity and fast electrolyte ion diffusion, which synergistically enhance the electrical energy storage performance. Symmetrical electrochemical capacitors with two rGO–V₂O₅ hybrid electrodes show excellent cycling stability, good rate capability, and a high specific capacitance up to ∼466 F g^–1 (regarding the total mass of V₂O₅) in a neutral aqueous electrolyte (1.0 M Na₂SO₄). When used as the cathode in lithium-ion batteries, the rGO–V₂O₅ hybrid demonstrates excellent cycling stability and power capability, able to deliver a specific capacity of 295, 220, and 132 mAh g^–1 (regarding the mass of V₂O₅) at a rate of C/9, 1C, and 10C, respectively. The value at C/9 rate matches the full theoretical capacity of V₂O₅ for reversible 2 Li⁺ insertion/extraction between 4.0 and 2.0 V (vs Li/Li⁺). It retains ∼83% of the discharge capacity after 150 cycles at 1C rate, with only 0.12% decrease per cycle. The enhanced performance in electrical energy storage reveals the effectiveness of rGO as the structure template and more conductive electron pathway in the hybrid material to overcome the intrinsic limits of single-phase V₂O₅ materials