Synthesis and Star/Linear Topology Transformation of a Mechanically Linked ABC Terpolymer.

The synthesis of an ABC star terpolymer containing one polymer chain connected mechanically through a rotaxane linkage and its topology transformation to a linear structure are reported. Pseudo[2]rotaxane, which was designed as the key trifunctional species for the star polymer synthesis, comprised a -ammonium axle with ethynyl and hydroxy groups and a crown ether wheel with a trithiocarbonate group. Stepwise polymer connections to the pseudo[2]rotaxane using the three groups afforded a rotaxane-linked ABC star terpolymer. The topology transformation from star to linear by the removal of the attractive interaction between the axle and wheel components yielded a linear ABC terpolymer via the wheel shifting to the axle end. The spectroscopic and solution property changes clearly indicated the occurrence of the polymer topology change.