General synthetic route to cell-permeable block copolymers via ROMP

The applications of block copolymers are myriad, ranging from electronics to functionalized resins to therapeutics. The ring-opening metathesis polymerization (ROMP) is an especially valuable reaction for block copolymer assembly because each block can be generated with length control. We sought to use this polymerization to expand the repertoire of block copolymers by implementing a strategy that involves postpolymerization modification of a backbone bearing selectively reactive groups. To this end, we demonstrate that ROMP can be used to synthesize a block copolymer scaffold that possesses three types of functional groups-a succinimidyl ester, an alpha-chloroacetamide group, and a ketone-each of which can be modified independently. Thus, a single scaffold can be elaborated to afford a wide range of block copolymers. Exploiting this synthetic approach and the length control offered by ROMP, we assemble block copolymers capable of traversing the membrane and entering mammalian cells.