Sustainable Copolymer Synthesis from Carbon Dioxide and Butadiene.

Carbon dioxide (CO2) has long been recognized as an ideal C1 feedstock comonomer for producing sustainable materials because it is renewable, abundant, and cost-effective. However, activating CO2 presents a significant challenge because it is highly oxidized and stable. A CO2/butadiene-derived δ-valerolactone (EVP), generated via palladium-catalyzed telomerization between CO2 and butadiene, has emerged as an attractive intermediate for producing sustainable copolymers from CO2 and butadiene. Owing to the presence of two active carbon-carbon double bonds and a lactone unit, EVP serves as a versatile intermediate for creating sustainable copolymers with a CO2 content of up to 29 wt % (33 mol %). In this Review, advances in the synthesis of copolymers from CO2 and butadiene with divergent structures through various polymerization protocols have been summarized. Achievements made in homo- and copolymerization of EVP or its derivatives are comprehensively reviewed, while the postmodification of the obtained copolymers to access new polymers are also discussed. Meanwhile, potential applications of the obtained copolymers are also discussed. The literature references were sorted into sections based on polymerization strategies and mechanisms, facilitating readers in gaining a comprehensive view of the present chemistry landscape and inspiring innovative approaches to synthesizing novel CO2-derived copolymers.

A Topology-Defined Polyester Elastomer from CO2 and 1,3-Butadiene: A One-Pot-One-Step "Scrambling Polymerizations" Strategy.

It is significant and challenging to use CO2 to produce polymeric materials, especially with olefins. Here, a novel strategy named "scrambling polymerizations" is designed and performed for the copolymerization of a CO2 -and-1,3-butadiene-derived valerolactone, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVL), with ϵ-caprolactone (CL) to prepare polyesters. Anionic ring-opening polymerization of CL and conjugated addition oligomerization of EVL take place individually to form PCL and EVL oligomers, respectively. Then EVL oligomers insert into PCL by transesterification resulting in polyester P(CL-co-EVL) with a tunable topology and composition. The non-cytotoxic and degradable polyester network with elongation at break of >600 % can be used as an elastomer. We propose a method to provide polyester elastomers from CO2 and olefins for the first time, and expand the potential of transformation from sustainable feedstocks to polymeric materials.

Understanding Acid-Promoted Polymerization of the N-Substituted Glycine N-Thiocarboxyanhydride in Polar Solvents.

Polymerization of N-substituted glycine N-thiocarboxyanhydrides (NNTAs) is a promising pathway to prepare functional polypeptoids benefiting from their tolerance to nucleophilic impurities. However, controlled NNTA polymerization is hard to achieve in amide polar solvents, including N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and N-methyl pyrrolidone (NMP), the only aprotic solvents for many biomacromolecules and polypeptoids. In the present work, we successfully achieve controlled NNTA polymerization in amide polar solvents by adding acetic acid as a promoter. The promotion is applied to the polymerization of sarcosine NTA, N-ethyl glycine NTA, and N-butyl glycine NTA. DMAc, DMF, and NMP are suitable solvents to prepare polypeptoids with designable molecular weights and low dispersities (1.06-1.21). The polysarcosines with high molecular weights are prepared up to 35.2 kg/mol. A kinetic investigation quantitatively reveals that the presence of acetic acid not only accelerates the polymerization, but also suppresses H2S-catalyzed decomposition of NNTAs by decreasing the concentration of H2S dissolved in polar solvents. Benzoic acid is also able to promote the polymerization, while trifluoroacetic acid, phosphoric acid, and phenol are not appropriate promoters. The moderate acidity of acids is essential. l-Methionine, l-tryptophan, and l-phenylalanine, which are dissolved in DMF, initiate the controlled polymerization of sarcosine-NTA in the presence of acetic acid and introduce functional end groups to polysarcosines quantitatively. In DMAc, hydrophilic vancomycin is grafted by poly(N-butyl glycine). The amphiphilic product dissolves in dichloromethane and stabilizes water-in-oil emulsion.

Understanding ring-closing and racemization to prepare α-amino acid NCA and NTA monomers: a DFT study.

Polypeptides and polypeptoids are promising materials in biomedical applications bearing α-amino acid repeating units, which are prepared from ring-opening polymerizations of α-amino acid N-carboxyanhydride (NCA) or N-thiocarboxyanydride (NTA) monomers. Detailed studies on monomer synthetic routes are essential to explore new α-amino acid NCA and NTA monomers as well as the corresponding poly(α-amino acid) materials. In this contribution, density functional theory (DFT) is applied to investigate the mechanism of the Leuchs approach including two possible pathways, precursor structure and racemization in the ring-closing reaction. According to DFT calculations, pathway 2 is preferred with lower ΔG than pathway 1, and the rate-determining step is recognized as an SN2 substitution with releasing equivalent halogenated hydrocarbon, which explains our experimental observations. Racemization results from the reaction between the NTA monomer and a strong protonic acid, which can be suppressed by low temperature and short reaction time. Racemization is inhibited by steric hindrance in those NTAs of α-amino acids containing high bulkiness at the ß-carbon, such as leucine-NTA.

Synthesis and Properties of Networks Based on Thiol-ene Chemistry Using a CO2 -Based δ-Lactone.

3-Ethylidene-6-vinyltetrahydro-2H-pyran-2-one, a divinyl δ-lactone derived from CO2 and 1,3-butadiene, is used for the synthesis of networks with various compositions through the thiol-ene click reaction with di- and tri-thiol compounds. Thermal, mechanical, and optical properties of the networks are characterized. The networks have sharp and uniform glass transitions and show good thermal stability with T d from 287 to 332 °C. Mechanical properties of the networks can be adjusted by the cross-link density; 6.18 MPa of tensile strength, 574% break elongation and 1.84 of tan δ at maximum are reached. Metal complexation makes the networks tougher due to additional cross-links. The highly homogeneous networks are transparent with average 90% transmittance of visible light, and of decent refractive indices around 1.55. Swelling-induced twist shape transformation and visible QR code under UV light is realized by pattern of the network.

Polyester Platform with High Refractive Indices and Closed-Loop Recyclability from CO2, 1,3-Butadiene, and Thiols.

α-Ethylidene-δ-vinyl-δ-valerolactone (EVL) is the only intermediate to synthesize copolymers of CO2 with 1,3-butadiene whose ring-opening polymerization (ROP), however, is obstructed by the tiglate group. In the contribution, EVL derivatives are synthesized through a Michael addition reaction to saturate the conjugated double bond as well as introduce various groups to synthesize polyesters with designable molecular weights (Mn = 6.9-12.8 kg·mol-1), narrow dispersities (D = 1.08-1.19), tunable glass-transition temperatures (Tg = -45-3 °C), and excellent refractive indices (nd = 1.64-1.79) via living and controlled ROP. The obtained polyesters are able to be recycled to the corresponding monomers, which can prepare comparable polymers with identical side groups, realizing the homorecycling. In addition, the retro-Michael addition reaction is established and employed, realizing heterorecycling, which can alter properties during recycling. We propose a strategy for EVL derivatives and establish the corresponding polyester platform with not only high refractive indices and tunable Tgs, but also the ability to tailor properties during recycling.

How to Open the Ring of a Di-ene-Substituted-δ-Valerolactone: From Carbon Dioxide and 1,3-Butadiene to Functional Polyesters.

As a substituted-δ-valerolactone, α-ethylidene-δ-vinyl-δ-valerolactone (EVL) provides a method of utilizing carbon dioxide with 1,3-butadiene to produce functional polymers. Its di-ene-substituted lactone ring was considered inactive in polymerization in the past two decades, while successful polymerization attempts of EVL have been reported very recently. Novel synthetic strategies and functional polymers from EVL have been developed. The ring-opening reactions of EVL and the corresponding polymers as well as the ring-opening (co)polymerizations of EVL and its derivatives are highlighted in this review. The obtained functional polymers with or without facile post-polymerization modification possess unique properties, such as amphipathy, elasticity, peel resistance, etc., allowing for application potential in various fields.

Ring-Opening Polymerization of CO2-Based Disubstituted δ-Valerolactone toward Sustainable Functional Polyesters.

3-Ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVL) is a disubstituent δ-lactone derived from CO2 and 1,3-butadiene. In this contribution, we report the ring-opening polymerization (ROP) of EVL with ß-butyrolactone (BBL) as the comonomer catalyzed by scandium triflate [Sc(OTf)3]. The obtained polyester bearing active unsaturated bonds has the weight-average molecular weight (Mw) of 4.1 kg/mol, in which the EVL content is 38 mol % in accordance with the initial ratio of 40 mol %. The copolymers are characterized in detail and the cationic ROP mechanism has been confirmed by kinetic study, chain end analysis and density functional theory (DFT) calculation. The modification of the unsaturated bonds in EVL repeating units via the thio-ene click reaction with mercapto-ended polysarcosine polysarcosine yields the amphiphilic grafting polymers. It is a CO2 fixation approach toward the functional poly(EVL-r-BBL) that is promising as a degradable polyester precursor for adhesive or surface-coating materials.

Carbon bridged triphenolate lanthanide complexes: synthesis, characterization, DFT studies and catalytic activities for isoprene polymerization.

The dinuclear lanthanide complexes [Ln2(L)2(THF)n] (Ln = Nd (1) n = 4, Gd (2) n = 3, Lu (3) n = 2) supported by carbon bridged triphenolate ligands [LH3 = tris(3,5-di-tert-butyl-2-hydroxyphenyl)methane] were synthesized via a salt metathesis reaction between lanthanide trichlorides and LNa3 in THF. All complexes were characterized by elemental analysis and X-ray crystallography, and complex 3 was characterized by (1)H and (13)C NMR spectroscopy. Agostic interactions were found in these complexes and were further substantiated by DFT calculations of complex 3. These lanthanide complexes in combination with aluminum alkyls and [Ph3C](+)[B(C6F5)4](-) generated efficient homogeneous catalysts for the cis-1,4 polymerization of isoprene, with complex 1 having the best catalytic activity.

Synthesis and characterization of benzoxazine-functionalized amine bridged bis(phenolate) lanthanide complexes and their application in the ring-opening polymerization of cyclic esters.

The synthesis and structures of lanthanide complexes supported by benzoxazine-functionalized amine bridged bis(phenolate) ligand 6,6'-(2-(8-tert-butyl-6-methyl-2H-benzo[e][1,3]oxazin-3(4H)-yl)ethylazanediyl)bis(methylene)bis(2-tert-butyl-4-methylphenolato) (L(2-)) are described. Salt metathesis reaction between lanthanide trichloride and 2 eq of LNa(2) in THF at room temperature afforded the corresponding "ate" complexes [L(2)LnNa(THF)(2)] (Ln[double bond, length as m-dash]Y (1), Nd (2), Er (3), Yb (4)). Further treatment of the product with 18-crown-6 afforded discrete ion-pair complexes [L(2)Ln][(18-crown-6)Na(THF)(2)] (Ln[double bond, length as m-dash]Y (5), Yb (6)). The single-crystal structural analyses of 1 and 3-6 revealed that the lanthanide cation and the sodium cation were bridged by two phenolate oxygen atoms in complexes 1, 3 and 4, while in complexes 5 and 6, the anion comprises a lanthanide cation coordinated by two L(2-) and the cation is comprised of a sodium cation surrounded by an 18-crown-6 and two THF molecules. These complexes were found to exhibit distinct activities towards the ring-opening polymerization of ε-caprolactone and l-lactide.