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[1H]-pyrimidinone (UPy) self-complementary quadruple hydrogen bonding units onto the high molecular weight (Mn) 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 Mn 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.