Recent developments in the synthesis of functional poly(olefin)s

Recent Advances in Living Cationic Polymerization with Emerging Initiation/Controlling Systems

While the conventional living cationic polymerization (LCP) provided opportunities to synthesizing well-defined polymers with predetermined molecular weights, desirable chemical structures and narrow dispersity, it is still important to continuously innovate new synthetic methods to meet the increasing requirements in advanced material engineering. Consequently, a variety of novel initiation/controlling systems have be demonstrated recently, which have enabled LCP with spatiotemporal control, broadened scopes of monomers and terminals, more user-friendly operations and reaction conditions, as well as improved thermomechanical properties for obtained polymers. In this work, recent advances in LCP is summarized with emerging initiation/controlling systems, including chemical-initiated/controlled cationic reversible addition-fragmentation chain transfer (RAFT) polymerization, photoinitiated/controlled LCP, electrochemical-controlled LCP, thionyl/selenium halide-initiated LCP, organic acid-assisted LCP, and stereoselective LCP. It is hoped that this summary will provide useful knowledge to people in related fields and stimulate new ideas to promote the development and application of LCP in both academia and industry.

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.

Preparation of functionalized poly(1-butene) from 1,2-polybutadiene via sequential thiol-ene click reaction and ring-opening polymerization

Poly(1-butene) is a kind of unique poly(α-olefin) material that displays exceptional creep resistance and environmental stress cracking resistance, and therefore currently finds wide application in the fields of packaging, films, pipes, etc. However, very few current researchers are paying attention to functional poly(1-butene) despite its great research significance, perhaps due to the general paucity of catalytic systems for synthesizing this material. Therefore, in the present study, we set out to develop an alternative method to prepare polar poly(1-butene)s. Specifically, 1,2-enriched poly(1,3-butadiene), used as a starting material, was partially hydrogenated to afford a quasi-poly(1-butene) polymer containing C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C double bonds. These double bonds were further modified by subjecting the quasi-poly(1-butene) polymer to a thiol-ene reaction in the presence of thiol compounds, and a series of polar poly(1-butene)s that bore significantly improved surface properties were obtained. By using hydroxyl-containing thiol compounds, ring-opening polymerization (ROP) of ε-caprolactone was further implemented. Here, polar poly(ε-caprolactone) was incorporated as side chains, and we were able to control the chain length by adjusting the feeding ratio. The water contact angles of the resultant polymers, i.e., those containing the poly(ε-caprolactone) side chains, were as low as 59.4°, indicating a greater hydrophilicity resulting from the incorporation of these side chains.

An alternative method for preparing functionalized poly(1-butene) from 1,2-polybutadiene via sequential thiol-ene click reaction and ring-opening polymerization is reported.

Facile functionalization of isotactic polypropylene via click chemistry

Alkynyl functionalized iPP, with 1–4 mol% comonomer incorporation, can be efficiently synthesized and conveniently converted into various functional iPPs and graft copolymers via alkynyl/N₃ reaction.

Titanium complex with an [OSSO]-type bis(phenolate) ligand for ethylene copolymerization with vinyl polar monomer based on group protection

The [OSSO]-type bis(phenolate) titanium complex 1 activated by methylaluminoxane (MAO) was tested as a homogeneous catalyst for ethylene coordination copolymerization with protected vinyl polar monomer of p-tert-butyl-dimethylsilyloxystyrene (p-TBDMSOS). The results showed that the active species were almost not poisonous to the catalyst by the protected vinyl polar monomer. Moreover, the composition and sequence length as well as sequence distribution in the copolymers were investigated by theoretical calculation and ¹³C nuclear magnetic resonance (¹³C NMR) characterization. Especially, the incorporation ratio of p-TBDMSOS into the polyethylene chain could be controlled by changing p-TBDMSOS concentration in the feed. Interestingly, an approximate alternating copolymer of poly(E-alt-(p-TBDMSOS)) could be formed when the p-TBDMSOS feed concentration increased to 1.0 mol L⁻¹. Subsequently, the poly(ethylene-co-(p-hydroxystyrene)) (poly(E-co-(p-HOS))) could be prepared by a facile deprotection in terms of desilylation of tert-butyldimethylsilyl ether. The hydrophilicity of poly(E-co-(p-HOS)) films were investigated by water contact angle measurements.

The [OSSO]-type bis(phenolate) titanium complex 1 activated by methylaluminoxane was used for the copolymerization of ethylene and protected vinyl polar monomer.

α,ω-Epoxide, Oxetane, and Dithiocarbonate Telechelic Copolyolefins: Access by Ring-Opening Metathesis/Cross-Metathesis Polymerization (ROMP/CM) of Cycloolefins in the Presence of Functional Symmetric Chain-Transfer Agents

Epoxide- and oxetane-α,ω-telechelic (co)polyolefins have been successfully synthesized by the tandem ring-opening metathesis polymerization (ROMP)/cross-metathesis (CM) of cyclic olefins using Grubbs' second-generation catalyst (G2) in the presence of a bifunctional symmetric alkene epoxide- or oxetane-functionalized chain-transfer agent (CTA). From cyclooctene (COE), trans,trans,cis-1,5,9-cyclododecatriene (CDT), norbornene (NB), and methyl 5-norbornene-2-carboxylate (NB^COOMe), with bis(oxiran-2-ylmethyl) maleate (CTA 1), bis(oxetane-2-ylmethyl) maleate (CTA 2), or bis(oxetane-2-ylmethyl) (E)-hex-3-enedioate (CTA 3), well-defined α,ω-di(epoxide or oxetane) telechelic PCOEs, P(COE-co-NB or -NB^COOMe)s, and P(NB-co-CDT)s were isolated under mild operating conditions (40 or 60 °C, 24 h). The oxetane CTA 3 and the epoxide CTA 1 were revealed to be significantly more efficient in the CM step than CTA 2, which apparently inhibits the reaction. Quantitative dithiocarbonatation (CS₂/LiBr, 40 °C, THF) of an α,ω-di(epoxide) telechelic P(NB-co-CDT) afforded a convenient approach to the analogous α,ω-bis(dithiocarbonate) telechelic P(NB-co-CDT). The nature of the end-capping function of the epoxide/oxetane/dithiocarbonate telechelic P(NB-co-CDT)s did not impact their thermal signature, as measured by DSC. These copolymers also displayed a low viscosity liquid-like behavior and a shear thinning rheological behavior.

Nickel-Catalyzed Propylene/Polar Monomer Copolymerization

Nickel complexes bearing bidentate alkylphophine-phenolate ligands were synthesized and applied to the polymerization of propylene and the copolymerization of propylene and polar monomers. Therein, the use of bulky alkyl substituents on the phosphorus atom was crucial for the formation of highly regioregular polypropylenes. Theoretical calculations suggested that the 1,2-insertion of propylene is favored over the 2,1-insertion in these nickel-catalyzed (co)polymerization reactions. The substituent at the ortho position relative to the oxido group greatly influences the polymerization activity, the molecular weight, and stereoregularity of the polypropylenes. This method delivers moderately isotactic ([mm] ≤ 68%) crystalline polypropylenes. The present system represents the first example for a nickel-catalyzed regiocontrolled copolymerization of propylene and polar monomers such as but-3-en-1-ol, but-3-en-1-yl acetate, and tert-butyl allylcarbamate.

Advances in the synthesis of silyl-modified polymers (SMPs)

Silyl-modified polymers (SMPs) are being synthesized from chemical modification and olefin metathesis strategies.

Synthesis of polymethylene-b-poly(vinyl acetate) block copolymer via visible light induced radical polymerization and its application

Polymethylene-b-poly(vinyl acetate) block copolymers were synthesized by polyhomologation of ylides and visible light-induced degenerative iodine transfer polymerization of vinyl acetate.

An efficient chain transfer reaction of the trithiocarbonate unit as a tool to prepare a functional polyolefin: a post-polymerization modification of ethylene–propylene–diene terpolymer for improved oil resistance

A novel strategy to modify polyolefins is applied to EPDM by using an efficient radical chain transfer reaction of trithiocarbonate.

Efficient copolymerization of ethylene with norbornene or its derivatives using half-metallocene zirconium(iv) catalysts

Four [O,P]ZrCpCl₂ were synthesized, and showed good performance on regioselective ethylene/cyclic dienes copolymerizations. Comonomer incorporations up to 76% (ENB) and 40.6% (VNB), respectively, with activities above 10³ kg per mol_Zr per h can be achieved.

New synthetic strategy targeting well-defined α,ω-telechelic polymethylenes with hetero bi-/tri-functionalities via polyhomologation of ylides initiated by new organic boranes based on catecholborane and post functionalization

Diverse well-defined α,ω-telechelic polymethylenes with hetero bi-/tri-functionalities were synthesized by a tandem strategy combining polyhomologation with post functionalization using end-capping reagents and esterification.

Synthesis, characterization and micellization of amphiphilic polyethylene-b-polyphosphoester block copolymers

Amphiphilic polyethylene-block-polyphosphoester (PE-b-PPE) copolymers can self-assemble into spherical micelles in aqueous solution and efficiently carry paclitaxel (PTX) drug.

Synthesis of polyethylene and polystyrene miktoarm star copolymers using an “in–out” strategy

Miktoarm star copolymers having multiple polyethylene and polystyrene arms joined at the crosslinked polydivinylbenzene core were synthesized using an “in–out” strategy with the combined Pd-catalyzed ethylene “living” polymerization and atom transfer radical polymerization.