Aliphatic Long-Chain C20 Polyesters from Olefin Metathesis

Synthesis of Network Biobased Aliphatic Polyesters Exhibiting Better Tensile Properties than the Linear Polymers by ADMET Polymerization in the Presence of Glycerol Tris(undec-10-enoate)

Development of biobased aliphatic polyesters with better mechanical (tensile) properties in film has attracted considerable attention. This report presents the synthesis of soluble network biobased aliphatic polyesters by acyclic diene metathesis (ADMET) polymerization of bis(undec-10-enyl)isosorbide diester [M1, dianhydro-D-glucityl bis(undec-10-enoate)] in the presence of a tri-arm crosslinker [CL, glycerol tris(undec-10-enoate)] using a ruthenium-carbene catalyst, and subsequent olefin hydrogenation using RhCl(PPh3)3. The resultant polymers, after hydrogenation (expressed as HCP1) and prepared in the presence of 1.0 mol% CL, showed better tensile properties than the linear polymer (HP1) with similar molecular weight [tensile strength (elongation at break): 20.8 MPa (282%) in HP1 vs. 35.4 MPa (572%) in HCP1]. It turned out that the polymer films prepared by the addition of CL during the polymerization (expressed as a 2-step approach) showed better tensile properties. The resultant polymer film also shows better tensile properties than the conventional polyolefins such as linear high density polyethylene, polypropylene, and low density polyethylene.

Thermally Robust yet Deconstructable and Chemically Recyclable High-Density Polyethylene (HDPE)-Like Materials Based on Si-O Bonds

Polyethylene (PE) is the most widely produced synthetic polymer. By installing chemically cleavable bonds into the backbone of PE, it is possible to produce chemically deconstructable PE derivatives; to date, however, such designs have primarily relied on carbonyl- and olefin-related functional groups. Bifunctional silyl ethers (BSEs; SiR2 (OR'2 )) could expand the functional scope of PE mimics as they possess strong Si-O bonds and facile chemical tunability. Here, we report BSE-containing high-density polyethylene (HDPE)-like materials synthesized through a one-pot catalytic ring-opening metathesis polymerization (ROMP) and hydrogenation sequence. The crystallinity of these materials can be adjusted by varying the BSE concentration or the steric bulk of the Si-substituents, providing handles to control thermomechanical properties. Two methods for chemical recycling of HDPE mimics are introduced, including a circular approach that leverages acid-catalyzed Si-O bond exchange with 1-propanol. Additionally, despite the fact that the starting HDPE mimics were synthesized by chain-growth polymerization (ROMP), we show that it is possible to recover the molar mass and dispersity of recycled HDPE products using step-growth Si-O bond formation or exchange, generating high molecular weight recycled HDPE products with mechanical properties similar to commercial HDPE.

Design and Synthesis of Novel Bio-Based Polyester Elastomer with Tunable Oil Resistance

Polarity determines the oil resistance property of elastomers. In this work, three bio-based polyester elastomers (BPEs) with different mass fraction of ester groups (E) are designed and synthesized aiming to study the relationship of E and oil resistance performance, and to obtain bio-based elastomer materials with tunable oil resistance. Through adjusting the chain length of monomers, E of poly(ethylene glycol/1,3-propanediol/succinate/adipate/itaconate)(PEPSAI), poly(1,3-propanediol/1,4-butanediol/succinate/adipate/itaconate)(PPBSAI), and poly(1,3-propanediol/1,4-butanediol/sebacate/adipate/itaconate)(PPBSeAI) are ≈50.39%, 48.55%, and 39.68%, respectively. Results show that E has great influence on the oil resistance of BPEs. After being immersed in IRM-903# oil for 72 h at room temperature, the changes in mass and volume of BPEs decrease along with the increasing mass fraction of ester groups, indicating improved oil resistance performance. PEPSAI with the highest mass fraction of ester groups presents better oil resistance and lower Tg (better low-temperature resistance) than one of the most used commercial oil-resistant rubber nitrile rubber (N230S). Thus, this work provides a promising strategy to obtain bio-based oil resistant elastomers with practical value.

Chemically Recyclable Ester-Linked Polypropylene

Polyolefins represent the largest class of commodity materials due to their excellent material properties; however, they have limited pathways to chemical recycling and are often difficult to mechanically recycle. Here we demonstrate a new catalyst for the isoselective copolymerization of propylene and butadiene capable of favoring 1,4-insertion over 1,2-insertion while maintaining good molecular weights and turnover frequencies. This isotactic propylene copolymer with main-chain unsaturation was depolymerized to a telechelic macromonomer using an olefin metathesis catalyst and 2-hydroxyethyl acrylate. After hydrogenation, the telechelic macromonomer was repolymerized to form an ester-linked polypropylene material. This polymer shows thermal and mechanical properties comparable to linear low-density polyethylene. Finally, the telechelic macromonomer could be regenerated through the depolymerization of the ester-linked polypropylene material, which allows for the chemical recycling to macromonomer. This process provides a route to transform partially unsaturated polyolefins to chemically recyclable materials with similar properties to their parent polymers.

Cysteine-Targeted Insecticides against A. gambiae Acetylcholinesterase Are Neither Selective nor Reversible Inhibitors

Acetylcholinesterase cysteine-targeted insecticides against malaria vector Anopheles gambia and other mosquitos have already been introduced. We have applied the olefin metathesis for the preparation of cysteine-targeted insecticides in high yields. The prepared compounds with either a succinimide or maleimide moiety were evaluated on Anopheles gambiae and human acetylcholinesterase with relatively high irreversible inhibition of both enzymes but poor selectivity. The concept of cysteine binding was not proved by several methods, and poor stability was observed of the chosen most potent/selective compounds in a water/buffer environment. Thus, our findings do not support the proposed concept of cysteine-targeted selective insecticides for the prepared series of succinimide or maleimide compounds.

Long-Chain Polyorthoesters as Degradable Polyethylene Mimics

The persistence of commodity polymers makes the research for degradable alternatives with similar properties necessary. Degradable polyethylene mimics containing orthoester groups were synthesized by olefin metathesis polymerization for the first time. Ring-opening metathesis copolymerization (ROMP) of 1,5-cyclooctadiene with four different cyclic orthoester monomers gave linear copolymers with molecular weights up to 38000 g mol-1. Hydrogenation of such copolymers produced semicrystalline polyethylene-like materials, which were only soluble in hot organic solvents. The crystallinity and melting points of the materials were controlled by the orthoester content of the copolymers. The polymers crystallized similar to polyethylene, but the relatively bulky orthoester groups were expelled from the crystal lattice. The lamellar thickness of the crystals was dependent on the amount of the orthoester groups. In addition, the orthoester substituents influenced the hydrolysis rate of the polymers in solution. Additionally, we were able to prove that non-hydrogenated copolymers with a high orthoester content were biodegraded by microorganisms from activated sludge from a local sewage plant. In general, all copolymers hydrolyzed under ambient conditions over a period of several months. This study represents the first report of hydrolysis-labile and potentially biodegradable PE mimics based on orthoester linkages. These materials may find use in applications that require the relatively rapid release of cargo, e.g., in biomedicine or nanomaterials.

New Coordination Modes for Modified Schiff Base Ti(IV) Complexes and Their Control over Lactone Ring-Opening Polymerization Activity

A series of eight new bis(alkoxy)bis(phenoxy-imine)titanium(IV) catalysts, coordinated by Schiff base ligands derived from o-vanillin (2-hydroxy-3-methoxybenzaldehyde), show good activity and control for the ring-opening polymerization of ε-caprolactone and ω-pentadecalactone. The new complexes are easily prepared in two high-yield steps from commercial reagents. The new ligands can all adopt two different coordination modes, depending on the steric bulk on the imine: a six-membered N-O chelate and/or a five-membered O-O chelate. The complexes show three different structures, depending on the ligand coordination mode: type A (N-O:N-O), type B (N-O:O-O), and type C (O-O:O-O). In all cases, the structures were confirmed in solution using variable temperature NMR spectroscopy and in the solid state using X-ray crystallography. The complex structure influences the polymerization rate, with the catalytic activities decreasing in the order: type C > type B > type A for both monomers. Overall, the work demonstrates potential to use these new ligands to access particular coordination modes, which allows enhancement of catalytic activity.

Tailored design of renewable copolymers based on poly(1,4-butylene 2,5-furandicarboxylate) and poly(ethylene glycol) with refined thermal properties

New copolymers based on renewable PBF/PEGF are tailored to show advantageous processing features as compared to PBF (enlarged working temperatures and no crystallisation at slow rates).

Bio-derived polymers for coating applications: comparing poly(limonene carbonate) and poly(cyclohexadiene carbonate)

Two fully bio-based polycarbonates, poly(limonene carbonate) and poly(cylcohexadiene carbonate), were post-functionalized via thiol–ene reactions and tested as future coating materials.

Convenient Controlled Aqueous C1 Synthesis of Long-Chain Aliphatic AB, AA, and BB Macromonomers for the Synthesis of Polyesters with Tunable Hydrocarbon Chain Segments

The insertion of long hydrocarbon chains between ester groups in polyester allows for introduction and modulation of crystallinity, which can result in enhanced performance approaching high-density polyethylene. We report a convenient synthesis of building blocks for long-chain aliphatic polyesters via an aqueous C1 polymerization. The macromonomers include ω-hydroxyacid esters, α,ω-diols and α,ω-diacids. The length of hydrocarbon chain segment (C20-C60) can be controlled by the ratio of monomer/initiator in the C1 polymerization. The obtained polyesters from condensation of the long-chain ω-hydroxyacid esters have thermal and mechanical properties indistinguishable from related materials derived from biomass.

Synthesis, properties and applications of biodegradable polymers derived from diols and dicarboxylic acids: from polyesters to poly(ester amide)s

Poly(alkylene dicarboxylate)s constitute a family of biodegradable polymers with increasing interest for both commodity and speciality applications. Most of these polymers can be prepared from biobased diols and dicarboxylic acids such as 1,4-butanediol, succinic acid and carbohydrates. This review provides a current status report concerning synthesis, biodegradation and applications of a series of polymers that cover a wide range of properties, namely, materials from elastomeric to rigid characteristics that are suitable for applications such as hydrogels, soft tissue engineering, drug delivery systems and liquid crystals. Finally, the incorporation of aromatic units and α-amino acids is considered since stiffness of molecular chains and intermolecular interactions can be drastically changed. In fact, poly(ester amide)s derived from naturally occurring amino acids offer great possibilities as biodegradable materials for biomedical applications which are also extensively discussed.

Functional films from unsaturated poly(macrolactones) by thiol–ene cross-linking and functionalisation

The synthesis of cross-linked surface-functional polyester films from natural macrolactones and their subsequent reaction with a fluorescent marker are presented.

Sustainable Polymers: Opportunities for the Next Decade

The field of sustainable polymers is growing and evolving at unprecedented rates. Researchers are increasingly concerned with the feedstock origins and the degradation behavior of, especially, large-scale commodity packaging plastics. A perspective is offered here for the design of sustainable polymers, specifically addressing opportunities for monomer development and polymer degradation. Key concepts include: water degradability instead of biodegradability; incorporation of novel main-chain functionality, such as acetals; utilization of lignin-based aromatics; and direct polymerization of biogenic C1 feedstocks.