Integration of metal-free ring-opening metathesis polymerization and organocatalyzed ring-opening polymerization through a bifunctional initiator

We have investigated the use of metal-free ring-opening metathesis polymerization (MF-ROMP) in combination with organocatalyzed ring-opening polymerization (o-ROP) to produce diblock copolymers with highly disparate block compositions via exclusively metal-free methods. Use of a bifunctional initiator bearing a vinyl ether as organic initiator for MF-ROMP and an alcohol for initiation of o-ROP allowed for investigation of three synthetic approaches: (1) sequential polymerization with isolation of the intermediate macroinitiators, (2) simultaneous bidirectional polymerizations, and (3) "one-pot" sequential monomer addition. Macroinitiators formed by first conducting o-ROP were successfully used in subsequent MF-ROMP to prepare diblock copolymers. Simultaneous MF-ROMP and o-ROP was thwarted by incompatible cross-combinations of catalysts and monomers. Finally, a straightforward "one-pot" synthesis of block copolymers, using o-ROP followed by MF-ROMP, was realized by sequential addition of each monomer-catalyst combination.