This paper describes a novel synthetic approach for three- and four-armed cage-shaped polymers based on the topological conversion of the corresponding trefoil- and quatrefoil-shaped precursors. The trefoil- and quatrefoil-shaped polymers were synthesized by the following three reaction steps: (1) the t-Bu-P4-catalyzed ring-opening polymerization of butylene oxide using multiple hydroxy- and azido-functionalized initiators to produce the three- or four-armed star-shaped polymers possessing three or four azido groups at the focal point, respectively, (2) the ω-end modification to install a propargyl group at each chain end, and (3) the intramolecular multiple click cyclization of the clickable star-shaped precursors. The topological conversion from the trefoil- and quatrefoil-shaped polymers to the cage-shaped polymers was achieved by the catalytic hydrogenolysis of the benzyl ether linkages that had been installed at the focal point. The amphiphilic cage-shaped block copolymers together with the corresponding trefoil- and quatrefoil-shaped counterparts were synthesized in a similar way using 2-(2-(2-methoxyethoxy)­ethoxy)­ethyl glycidyl ether as a hydrophilic monomer and decyl glycidyl ether as a hydrophobic monomer. Interestingly, significant changes in the critical micelle concentration and micellar morphology were observed for the amphiphilic block copolymers upon the topological conversion from the trefoil- and quatrefoil-shaped to cage-shaped architectures.

A comprehensive set of amphiphilic star-shaped block copolyethers with a fixed molecular weight and composition was synthesized via the t-Bu-P 4 -catalyzed ringopening polymerization (ROP) of 2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether as a hydrophilic monomer and decyl glycidyl ether as a hydrophobic monomer. The threeand four-armed star-block copolyethers, i.e., the (AB) 3 -, (BA) 3 -, (AB) 4 -, and (BA) 4 -type star-block copolyethers, where A and B represent hydrophilic and hydrophobic blocks, respectively, were synthesized by the sequential t-Bu-P 4catalyzed block copolymerization using tri-and tetra-alcohol initiators, respectively, according to the core-first method. The homogeneous growth of each arm was confirmed by cleaving the linkages between the initiator residue and polyether arms. The synthesis of the A 2 B 2 -, AB 2 -, and A 2 B-type miktoarm star copolyethers was achieved by the combination of the t-Bu-P 4 -catalyzed ROP and azido-alkyne click chemistry. The azido-and ethynyl-functionalized precursor polyethers with the predicted molecular weights were separately prepared by the t-Bu-P 4 -catalyzed ROP with the aid of functional initiators as well as a terminator. The intermolecular click reaction of the precursors provided the desired miktoarm star copolyethers. All the obtained star-shaped block copolyethers had a comparable monomer composition (degree of polymerization = 50:50) and total molecular weight (ca. 22 200 g mol −1 ) with a narrow dispersity (<1.05). The hydrodynamic diameter and the cloud point analyses for the aqueous micellar solution of the amphiphilic star-shaped block copolyethers revealed that the self-assembly properties were affected by the block arrangements and branched architectures of the amphiphilic polymers.