Branched Polytetrahydrofuran and Poly(tetrahydrofuran‐co‐ε‐caprolactone) Synthesized by Janus Polymerization: A Novel Self‐Healing Material

The Janus polymerization combines cationic and anionic polymerizations into growing chains with two different chain ends. This provides a novel pathway to produce topologically interesting polymers. Here this polymerization is applied to allow the synthesis of branched polytetrahydrofuran (bPTHF) and poly(tetrahydrofuran‐co‐ε‐caprolactone) (bPTC). Rare earth triflates RE(OTf)₃] (RE = Lu, Sc, and Y) are used as catalyst, and small amounts (0.10–0.15 mol%) of ethylene glycol diglycidyl ether act as both initiator and comonomer due to the different reactivities of the two epoxide groups. The poly(ε‐caprolactone) block in bPTC provides crystalline domains and potential degradation under acidic conditions. The products of bPTHF show unusual tensile properties with a high strain at break of 1070% differing greatly from linear PTHF. Due to the large number of terminal hydroxyl groups and their strong hydrogen bonding, bPTHF has self‐healing properties with potentially promising applications.