No abstract

Degradable polyester elastomers are highly desirable for biomedical applications.Here, highly transparent and degradable aliphatic polyester elastomers were prepared using the ring-opening copolymerization (ROCP) of commercial monomers, followed by a photo-crosslinking process. A series of the semi-crystalline copolyester (PMBL-co-PBL-co-PCL) precursors with different molecular weights and pendent vinyl contents were synthesized by one-pot ROCP of α-methylene-γ-butyrolactone (MBL), ε-caprolactone (ε-CL) and γ-butyrolactone (γ-BL). Then, UV irradiation was applied to photo-crosslink the precursors to obtain several elastomers. The obtained aliphatic polyester elastomers (CPEs) displayed excellent mechanical properties with high tensile strength (11.3 MPa), high elongation at break (1300%) and high elastic recovery (about 99% after 10 hysteresis cycles). In addition, the elastomer showed much better stability than uncrosslinked (co)polyesters, but maintained degradability in the basic aqueous solution, with $30% of the mass loss in 1 M NaOH solution after 30 days. Through efficient ROCP, we demonstrated a strategy to prepare degradable CPEs bearing high strength, good elasticity, excellent resilience and degradation capability, which can serve as sustainable elastomers for various applications.

The commercially available 1,2-polybutadiene (1,2-PB) contains highly reactive CC bonds and has excellent machinability, which is an ideal raw material for preparing thermoplastic elastomers. The preparation of supramolecular cross-linked 1,2-PB thermoplastic elastomer with good recyclability and excellent mechanical properties has promising applications. Here, the 1,2-PB elastomers (UPB elastomers) were prepared by conjugating a few percent 2-ureido-4­[1H]-pyrimidinone (UPy) self-complementary quadruple hydrogen bonding units onto the high molecular weight (M n) 1,2-PB chains via the thiol-ene click reaction. The used 2-(mercaptoethyl-ureido)-pyrimidinone derivative (UPy-SH) with a branched alkyl group had good compatibility with 1,2-PB in organic solvent contributing to a high transparency of recyclable UPB elastomers. The cross-linking density of UPB elastomers can be conveniently adjusted by varying the UPy content, which ultimately determined the mechanical properties of resulting supramolecular elastomers. Abundant chain entanglements formed by 1,2-PB chains with a high M n of 455 kDa and strong quadruple hydrogen bonding networks formed by side UPy units endowed UPB elastomers with excellent mechanical properties and damping properties. It was found that sample UPB-2 containing 2 mol % UPy units showed a tensile strength of 13.4 MPa, a high elongation at break of 1167%, a high elastic recovery of 89% (under large tensile deformation of 400%), a high peak tan δ value (tan δmax) of 1.4, and an effective damping temperature range width of 30.6 °C. Moreover, UPB elastomers have good recyclability given the noncovalent cross-linking networks. This effective and universal strategy provides some insights into the design of physically cross-linked high-performance 1,2-polybutadiene elastomers.