Ring-opening metathesis polymerization of a modified linseed oil with varying levels of crosslinking

Cationic Copolymers of Norbornylized Seed Oils for Fiber-Reinforced Composite Applications

Norbornylized seed oils, i.e., norbornylized linseed oil (NLO), norbornylized soybean oil (NSO), and norbornylized high oleic soybean oil (NHOSO), were synthesized via the Diels-Alder reaction of seed oil and dicyclopentadiene (DCPD) at high temperature (∼235 °C) and high pressure (∼80 psi), followed by cationic copolymerization using DCPD with boron trifluoride diethyl etherate catalyst. Norbornylized seed oils were characterized using H1 nuclear magnetic resonance (NMR), attenuated total reflectance-Fourier transform infrared, and gel permeation chromatography (GPC). Copolymers were formulated with four different DCPD contents, and curing was investigated using dynamic differential scanning calorimetry (DSC) measurements. It was found that the curing followed NLO > NSO > NHOSO with NLO having the highest exotherm, lowest activation energy, and lowest onset temperature. Furthermore, the gelation times were the least for NLO-DCPD copolymers. As anticipated, the degree of unsaturation and norbornene moieties strongly influenced the curing of copolymer thermosets. The copolymer products were compression-molded into thermosets and characterized by DSC, Soxhlet extraction, thermogravimetric analysis (TGA), H1 NMR, solid-state C13 NMR, and GPC. NLO-DCPD thermosets demonstrated high cure, higher thermal stability, glass transition temperature, and cross-linking capability compared to the other seed oil-DCPD counterparts. NMR and GPC results further suggested that bis-allylic and norbornene units concomitantly participated very actively during the cationic curing reaction. Moreover, scanning electron microscopy images of glass fiber-reinforced NLO-DCPD copolymer composites demonstrated good interfacial adhesion between the polymer matrix and fiber phases, imparting enhanced thermo-mechanical properties. This research opens a new venue for higher biobased greener polymer constituent for composite applications.

Norbornene-Functionalized Plant Oils for Biobased Thermoset Films and Binders of Silicon-Graphite Composite Electrodes

We herein report the functionalization of plant oil with norbornene (NB) and subsequent polymerization to prepare biobased thermoset films and biobased binders for silicon/mesocarbon microbead (MCMB) composite electrodes for use in lithium-ion batteries. A series of NB-functionalized plant oils were prepared as biobased thermoset films via ring-opening metathesis polymerization (ROMP) in the presence of a second-generation Grubbs catalyst with tunable thermomechanical properties. Increasing the catalyst loading and cross-linking agent increased cross-link density, storage modulus (E'), and glass transition temperature (T _g), while the numbers of unreacted or oligomeric components in the films were reduced. High number of NB rings per triglyceride in the plant oil encouraged monomer incorporation to form a polymer network, therefore accounting for the high T _g and E' values. Furthermore, the NB-functionalized plant oil and 2,5-norbornadiene (NBD) were copolymerized as bioderived binders for silicone/MCMB composite electrodes of lithium-ion batteries via ROMP during electrode preparation. Cell performance investigation showed that the silicone/MCMB composite electrode bearing the NBD-cross-linked NB-functionalized plant oil binder exhibited a higher C-rate and cycle-life performance than that using a conventional poly(vinylidene fluoride) (PVDF) binder. Finally, the electrode based on the bioderived binder exhibited a high specific charge capacity of 620 mA h g^-1 at 0.5 C.

Influence of molecular weight between crosslinks on the mechanical properties of polymers formed via ring-opening metathesis

The apparent molecular weight between crosslinks (Mc,a) in a polymer network plays a fundamental role in the network mechanical response. We systematically varied Mc,a independent of strong noncovalent bonding by using ring-opening metathesis polymerization (ROMP) to co-polymerize dicyclopentadiene (DCPD) with a chain extender that increases Mc,a or a di-functional crosslinker that decreases Mc,a. We compared the ROMP series quasi-static modulus (E), tensile yield stress (σy), and fracture toughness (KIC and GIC) in the glassy regime with literature data for more polar thermosets. ROMP resins showed high KIC (>1.5 MPa m0.5), high GIC (>1000 J m-2), and 4-5 times higher high rate impact resistance than typical polar thermosets with similar Tg values (100 °C to 178 °C). The overall E values were lower for ROMP systems. The σy dependence on Mc,a and T-Tg for ROMP resins was qualitatively similar to more polar thermosets, but the overall σy values were lower. In contrast to more polar thermosets, the KIC and GIC values of the ROMP resins showed strong Mc,a and T-Tg dependence. High rate impact (∼104-105 s-1) trends were similar to the KIC and GIC behavior, but were also correlated to σy. Overall, a ductile failure mode was observed for quasi-static and high rate results for a linear ROMP polymer (Mc,a = 1506 g mol-1 due to chain entanglement), and this gradually transitioned to a fully brittle failure mode for highly crosslinked ROMP polymers (Mc,a ≤ 270 g mol-1). Molecular dynamics (MD) simulations showed that low Mc,a ROMP resins were more likely to form molecular scale nanovoids. The higher chain stiffness in low Mc,a ROMP resins inhibited stress relaxation in the vicinity of these nanovoids, which correlated with brittle mechanical responses. Overall, these differences in mechanical properties were attributed to the weak non-covalent interactions in ROMP resins.

Vegetable-oil-based polymers as future polymeric biomaterials

Vegetable oils are one of the most important classes of bio-resources for producing polymeric materials. The main components of vegetable oils are triglycerides - esters of glycerol with three fatty acids. Several highly reactive sites including double bonds, allylic positions and the ester groups are present in triglycerides from which a great variety of polymers with different structures and functionalities can be prepared. Vegetable-oil-based polyurethane, polyester, polyether and polyolefin are the four most important classes of polymers, many of which have excellent biocompatibilities and unique properties including shape memory. In view of these characteristics, vegetable-oil-based polymers play an important role in biomaterials and have attracted increasing attention from the polymer community. Here we comprehensively review recent developments in the preparation of vegetable-oil-based polyurethane, polyester, polyether and polyolefin, all of which have potential applications as biomaterials.

Homogeneous catalysis for the conversion of biomass and biomass-derived platform chemicals

This perspective highlights the importance of homogeneous catalysis in the selective and efficient transformation of various types of biomass and platform chemicals to useful chemicals.

Improving sustainability in ene-yne cross-metathesis for transformation of unsaturated fatty esters

Ruthenium-catalyzed ene-yne cross-metathesis is performed with stoichiometric proportions of terminal olefins and alkynes. This is made possible by the continuous addition of the alkyne to the reaction mixture. The protocol allows the ene-yne cross-metathesis reaction to be carried out with long-chain terminal olefins and in a one-pot fashion with internal olefins after shortening by ethenolysis. The efficient conversion of renewable unsaturated fatty esters from bioresources into valuable conjugated 1,3-dienes of interest for further transformations is performed using this technique under mild conditions in dimethyl carbonate; an ecofriendly solvent.

Novel polymeric materials from vegetable oils and vinyl monomers: preparation, properties, and applications

Veggie-based products: Vegetable-oil-based polymeric materials, prepared by free radical, cationic, and olefin metathesis polymerizations, range from soft rubbers to ductile or rigid plastics, and to high-performance biocomposites and nanocomposites. They display a wide range of thermophysical and mechanical properties and may find promising applications as alternatives to petroleum-based polymers.Vegetable oils are considered to be among the most promising renewable raw materials for polymers, because of their ready availability, inherent biodegradability, and their many versatile applications. Research on and development of vegetable oil based polymeric materials, including thermosetting resins, biocomposites, and nanocomposites, have attracted increasing attention in recent years. This Minireview focuses on the latest developments in the preparation, properties, and applications of vegetable oil based polymeric materials obtained by free radical, cationic, and olefin metathesis polymerizations. The novel vegetable oil based polymeric materials obtained range from soft rubbery materials to ductile or rigid plastics and to high-performance biocomposites and nanocomposites. These vegetable oil based polymeric materials display a wide range of thermophysical and mechanical properties and should find useful applications as alternatives to their petroleum-based counterparts.