Dynamically Cross-Linked Polyolefin Elastomers with Highly Improved Mechanical and Thermal Performance

Abstract

The controllable introduction of dynamical chemical cross-linking into polymers permits the development of recyclable polymer products with high performance. However, challenges lie in chemically inert polyolefins, which are the largest polymer product in the world to date. Here, we demonstrate the preparation of polyolefin elastomers (POEs) with tunable dynamic chemical cross-linking, compatible with their industrial production. Boronic ester bond cross-linked POEs (BPOEs) present high mechanical performances with tensile strength (σ) up to 23.8 MPa, Young's modulus (E) up to 29.0 MPa, and toughness (U T ) up to 69.6 MJ•m −3 , far superior to those reported elastomers. BPOEs also demonstrate good thermal stability maintaining a steady storage modulus plateau of 2.9 MPa above 100 °C, instead of 0.2 MPa for pristine POEs. After reprocessing three times, BPOEs show a good reprocessability with a σ recovery of 85.6%, an E of 108.5%, a U T of 95.7%, and an elongation at break (ε) of 97.1%, even higher than that of commercial POEs such as POE-8150 of Dow Company. Our method thus permits the future development of higher-performance POEs and other polyolefins with good reprocessability and recyclability.

Preparation of Styrene–Butadiene Rubber Vitrimers with High Strength and Toughness through Imine and Hydrogen Bonds

“…Vitrimers are a type of dynamic covalently cross-linked polymers that can rearrange their topology via associative bond-exchange reactions. , The exchangeable covalent cross-linking makes vitrimers a combination of fascinating characteristics of thermoplastics and thermosets. Since the concept of vitrimers was described in 2011, a variety of reversible covalent bonds based on transesterification, − transcarbamoylation, − boronic ester exchange, − olefin metathesis, , disulfide exchange, − and imine exchange − have been explored in the design of elastomer vitrimers, demonstrating that a reprocessable rubber with strong elasticity could be obtained via vitrimer chemistry. Imine bonds are a class of catalyst-free and readily available exchangeable bonds. , Bui et al reported a Schiff-base silicone elastomer with self-healing and recycling abilities and demonstrated the catalyst-free dynamic exchange of imine bonds.…”

Molecularly Defined Polyolefin Vitrimers from Catalytic Insertion Polymerization

“…This yields a strongly heterogeneous polymer in terms of functionalization of the chains, which also reflects in the vitrimer properties . Following this seminal work, further approaches to such polyethylene vitrimers by post-polymerization modification of the hydrocarbon polymer were reported. ,− …”

Vitrimeric Polylactide by Two-step Alcoholysis and Transesterification during Reactive Processing for Enhanced Melt Strength

“…Vitrimers, designed and named by Leibler and co-workers in 2011, − are a new class of chemically cross-linked polymers that are capable of network topology alternation through the associative dynamic bond-exchange mechanism, which is hopeful to solve the problem of conventional cross-linked materials, such as poor recyclability. − Thus far, the concept of vitrimers has been applied to various commercial polymers, giving thermoplastic materials high mechanical robustness, − creep resistance, solvent resistance, , stress cracking resistance, and self-adhesion, which provide useful hints for the practical applications of the vitrimer concept in thermoplastics. Zhou et al prepared poly­(butylene terephthalate) (PBT) vitrimers and proposed that it is another method to increase the melt strength via introducing dynamic cross-links.…”