Recent Advancements in the Synthesis of Functional Polyolefins by Non-Bridged Half-Titanocenes

Polyolefins are used widely due to their benefits such as being lightweight, chemical inertness, low cost, tunable properties, and easy processability. However, their nonpolar nature significantly limits their high-end applications. The non-bridged half-titanocenes exhibit remarkable catalytic activities with good comonomer incorporations in the olefin polymerization. The synthesis of functional polyolefins has attracted more and more attention recently. The non-bridged half-titanocenes have been used in the preparation of functional polyolefins, in particular the functional olefin copolymers. Herein, the recent advancements in the synthesis of functional polyolefins by non-bridged half-titanocenes were reviewed. The functional polyolefins have been synthesized by direct copolymerization of olefin with functional comonomers using half-titanocenes as precatalysts. In addition, polyolefins containing reactive groups could be synthesized by the olefin (co)polymerization using half-titanocenes as precatalysts. The functional polyolefins were synthesized successfully by the post-functionalization of polyolefin containing reactive groups.

Polymerization of Myrcene in Both Conventional and Renewable Solvents: Postpolymerization Modification via Regioselective Photoinduced Thiol-Ene Chemistry for Use as Carbon Renewable Dispersants

Polymeric dispersants are useful materials used in many different industries and often derived from oil-based chemicals, for example, in automotive fluids so as to prevent particulates from precipitation and causing potential damage. These are very often polyisobutene derivatives, and there is a growing need to replace these using chemicals using renewable resources such as the use of naturally occurring myrcene. Polymyrcene (PMy), with an ordered microstructure, has been successfully synthesized via both anionic and radical polymerization in different solvents and subsequently subjected to functionalization via photoinduced thiol-ene click reactions with a number of thiols, methyl thioglycolate, 3-mercaptopropionic acid, 3-mercapto-1-hexanol, 2-mercaptoethanol, and 1-thioglycerol, using 2,2-dimethoxy-2-phenylacetophenone as a photoinitiator under UV irradiation (λ = 365 nm) at ambient temperature. The polarity of the solvent has an important impact on the microstructure of the produced polymyrcene and, in particular, 1,2-unit (∼4%), 3,4-unit (∼41%), and 1,4-unit (∼51%) PMy were obtained via anionic polymerization in a polar solvent (THF) at ambient temperature, while 3,4-unit (∼6%) and 1,4-unit (∼94%, including cis and trans) PMy were obtained with cyclohexane as the solvent. Subsequently, photochemical thiol-ene reactions were carried out on the resulting PMy with different isomers exhibiting different reactivities of the double bonds. This strategy allows for the introduction of functional/polar groups (-COOH, -OH) into hydrophobic PMy in a controlled process. Hydrogenation of PMy and derivatized PMy was carried out to investigate any effects on the stabilities of the products which are desirable for many applications.

Synthesis of ultrahigh-molecular-weight ethylene/1-octene copolymers with salalen titanium(iv) complexes activated by methyaluminoxane

Two salalen titanium(iv) complexes ((H-salalen)TiCl2 and (F-salalen)TiCl2) containing hydrogen and fluorine respectively on the phenolate ring close to the imine were synthesized for the copolymerization of ethylene with 1-octene to prepare poly(ethylene-co-1-octene) in the presence of methylaluminoxane (MAO). The (F-salalen)TiCl2/MAO showed higher catalytic activity and better copolymer characteristics such as a higher molecular weight, narrower molecular weight distribution, and higher 1-octene incorporation than (H-salalen)TiCl2/MAO, which revealed that the electron-withdrawing conjugated effect introduced by fluorine substituents led to improvements on catalytic performance and thermal stability. The influences of copolymerization conditions including temperature, Al/Ti molar ratios and comonomer feed ratios on the copolymerization behavior of (F-salalen)TiCl2/MAO and the copolymer microstructure were investigated in detail. Under the activation of MAO, the (F-salalen)TiCl2 could produce ultrahigh molecular weight poly(ethylene-co-1-octene) with 1-octene incorporation ratios in the range of 0.9-3.1 mol% and exhibit relatively high activity. It could be inferred that long ethylene sequences in the copolymer were segregated by the isolated 1-octene units based on the 13C NMR characterization of the copolymer. Moreover, the thermal properties and crystallization of copolymers were determined by DSC and XRD and correlated to the ethylene sequence length distribution. The reactivity ratios calculated by the triad distribution in 13C NMR revealed the random comonomer distribution in the copolymer chain.

Stereoregular Polymerization of Acyclic Terpenes

The growing environmental pollution and the expected depleting of fossil resources have sparked interest in recent years for polymers obtained from monomers originating from renewable sources. Furthermore, nature can provide a variety of building blocks with special structural features (e. g. side groups or stereo-elements) that cannot be obtained so easily via fossil-based pathways. In this context, terpenes are widespread natural compounds coming from non-food crops, present in a large variety of structures, and ready to use as monomers with or without further modifications. The present review aims to provide an overview of how chemists can stereospecifically polymerize terpenes, particularly the acyclic ones like myrcene, ocimene, and farnesene, using different metal catalyst systems in coordination-insertion polymerization. Attention is also paid to their copolymers, which have recently been disclosed, and to the possible applications of these bio-based materials in various industrial sectors such as in the field of elastomers. © 2021 The Authors. ChemPlusChem published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

INTRODUCING BIOBASED NONPOLAR BOTTLEBRUSH β-MYRCENE SEGMENTS TO IMPROVE SILICA DISPERSION FOR SUSTAINABLE SSBR/SILICA NANOCOMPOSITES

To overcome the problem of fossil fuel depletion and associated environmental issues arising from the use of tire tread elastomers, a convenient, environmentally friendly, and highly efficient strategy was developed to prepare high-performance green solution polymerized styrene–butadiene rubber (SSBR)/silica nanocomposites by improving silica dispersion in the nonpolar polymer matrix via the introduction of a biobased nonpolar bottlebrush segment with two double bonds. Various elastomers containing biobased nonpolar bottlebrush β-myrcene segments were synthesized using an industrially robust anionic polymerization method. Results of rubber process analysis, small-angle X-ray scattering, scanning electron microscopy, and transmission electron microscopy revealed that rubber with myrcene could significantly improve silica dispersibility and inhibit the strong filler–filler interactions, which are due to the formation of hydrogen bonding between the double bonds in the myrcene block and silanol groups on the silica surface and possibly to the spreading or infiltrating of myrcene bottlebrush segments onto silica. Furthermore, for the modified rubber, rolling resistance decreased by 41.7%, tear strength increased by 20.78%, and tensile strength increased by 77.8% with the elongation at break remained practically unchanged as compared with the unmodified silica/SSBR composite. On the basis of aforementioned assessment, we believe that silica-reinforced β-myrcene–based styrene–butadiene integrated rubber is a versatile and promising candidate for future tire tread elastomers.

Sustainable Myrcene-Based Elastomers via a Convenient Anionic Polymerization

Soluble heterocomplexes consisting of sodium hydride in combination with trialkylaluminum derivatives have been used as anionic initiating systems at 100 °C in toluene for convenient homo-, co- and ter-polymerization of myrcene with styrene and isoprene. In this way it has been possible to obtain elastomeric materials in a wide range of compositions with interesting thermal profiles and different polymeric architectures by simply modulating the alimentation feed and the (monomers)/(initiator systems) ratio. Especially, a complete study of the myrcene-styrene copolymers (PMS) was carried out, highlighting their tapered microstructures with high molecular weights (up to 159.8 KDa) and a single glass transition temperature. For PMS copolymer reactivity ratios, rmyr = 0.12 ± 0.003 and rsty = 3.18 ± 0.65 and rmyr = 0.10 ± 0.004 and rsty = 3.32 ± 0.68 were determined according to the Kelen-Tudos (KT) and extended Kelen-Tudos (exKT) methods, respectively. Finally, this study showed an easy accessible approach for the production of various elastomers by anionic copolymerization of renewable terpenes, such as myrcene, with commodities.

Rigid Acridane-Based Pincer Supported Rare-Earth Complexes for cis-1,4-Polymerization of 1,3-Conjugated Dienes

A convenient synthetic route has been developed for preparing the novel rigid 4,5-(PR₂)2-2,7,9,9-tetramethylacridane-based pincer ligands (^acri-RPNP; R = ⁱPr and Ph), and the first rare-earth (Ln = Y, Lu) alkyl complexes bearing the ^acri-RPNP ligands were synthesized by a salt metathesis reaction (for the isopropyl-substituent ^acri-iPrPNP complexes, 1-Ln) or direct alkylation (for the phenyl-substituent ^acri-PhPNP complexes, 2-Ln). For both 1-Ln and 2-Ln, the NMR spectroscopy and X-ray diffraction study confirmed the successful coordination of the ^acri-RPNP ligand to the central metal ion in a tridentate manner via the two phosphine and the nitrogen donors. In contrast to 1-Ln that are solvent-free complexes, the metal centers in 2-Ln are each coordinated with one tetrahydrofuran molecule. Upon activation by [Ph₃C][B(C₆F₅)₄], 1-Y and 2-Lu could catalyze the living polymerization of isoprene and β-myrcene with high catalytic activity and high cis-1,4-selectivity (up to 92.3% for isoprene and 98.5% for β-myrcene). Moreover, the 1-Y/[Ph₃C][B(C₆F₅)₄] catalytic system also could promote the polymerization of butadiene and its copolymerization with isoprene to produce copolymers with high cis-1,4-selectivity and narrow polydispersity.

Highly efficient terpolymerizations of ethylene/propylene/ENB with a half-titanocene catalytic system

Highly efficient terpolymerization of ethylene, propylene and 5-ethylidene-2-norbornene using a half-titanocene containing iminoimidazolidine with methylaluminoxane/Al(iBu)3/2,6-ditertbutyl-4-methyl-phenol was achieved.

Epoxidized 1,4-polymyrcene

Epoxidized 1,4-polymyrcenes with different degrees of epoxidation (25–98%) were prepared and examined according to their chemical and thermal properties.

Aqueous cationic homo- and co-polymerizations of β-myrcene and styrene: a green route toward terpene-based rubbery polymers

A green and cost-efficient approach for the synthesis of bio-based poly(β-myrcene) and poly(β-myrcene-co-styrene) via emulsion cationic polymerization is developed.

Convenient synthesis of versatile syndiotactic polystyrene materials containing pendant alkenyl groups with a scandium catalyst system

The syndioselective copolymerization of styrene with five alkenyl functionalized styrenic monomers, with the use of a scandium catalyst, produced a new family of versatile syndiotactic polystyrene materials with pendant alkenyl groups.