Janus Polymerization: A One‐Shot Approach towards Amphiphilic Multiblock Poly(ester‐acetal)s Directly from 1,3‐Dioxolane with ε‐Caprolactone

Comprehensive Summary Janus polymerization consists of anionic and cationic ring opening polymerizations (AROP and CROP) at the two ends of a single propagating polymer chain, followed by a self‐triggered chain extension generating multiblock copolymers (MBCPs) in one step. In the contribution, Janus polymerization by Tm(OTf) 3 or Er(OTf) 3 catalyst with an epoxy initiator is applied to synthesize MBCPs of semi‐crystalline poly( ε ‐caprolactone) (PCL) blocks from coordinated AROP and poly(1,3‐dioxolane‐ co ‐ ε ‐caprolactone) (P(DO‐ co ‐CL)) blocks from CROP of DO with CL. Meanwhile, amorphous random copolymers [P(DO‐ r ‐CL)] are synthesized as control by employing other rare earth triflates [RE(OTf) 3 , RE = Y, Nd, Gd and Lu] as catalysts or in the absence of an initiator via CROP. On account of the distinguishable chemical structures and thermal properties between Janus MBCPs and cationic random copolymers, Janus features are confirmed including the CROP and AROP at a single propagating chain. The resultant amphiphilic copolymers self‐assemble to nanoparticles in aqueous solution with designable diameters with the corresponding ratios of hydrophilic and hydrophobic segments. MBCPs exhibit good shape memory properties with appropriate deformation temperature close to human body's, providing a prospect on the applications in biomedical devices.