Tough and Recyclable Polybutadiene Elastomer Based on Quadruple Hydrogen Bonding

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[1 H ]-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 δ max ) 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.