Tough and Recyclable Polybutadiene Elastomer Based on Quadruple Hydrogen Bonding

The commercially available 1,2-polybutadiene(1,2-PB)containshighly 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 thermoplasticelastomer with good recyclability and excellent mechanical propertieshas 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 bondingunits onto the high molecular weight (M-n) 1,2-PB chains via the thiol-ene click reaction. The used 2-(mercaptoethyl-ureido)-pyrimidinonederivative (UPy-SH) with a branched alkyl group had good compatibilitywith 1,2-PB in organic solvent contributing to a high transparencyof recyclable UPB elastomers. The cross-linking density of UPB elastomerscan be conveniently adjusted by varying the UPy content, which ultimatelydetermined 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 bondingnetworks formed by side UPy units endowed UPB elastomers with excellentmechanical properties and damping properties. It was found that sampleUPB-2 containing 2 mol % UPy units showed a tensile strength of 13.4MPa, a high elongation at break of 1167%, a high elastic recoveryof 89% (under large tensile deformation of 400%), a high peak tan delta value (tan delta(max)) of 1.4, and an effectivedamping temperature range width of 30.6 degrees C. Moreover, UPB elastomershave good recyclability given the noncovalent cross-linking networks.This effective and universal strategy provides some insights intothe design of physically cross-linked high-performance 1,2-polybutadieneelastomers.