ABC Supramolecular Triblock Copolymer by ROMP and ATRP

We report the controlled polymerization of three heterotelechelic polymers from supramolecular motif-bearing initiators, their assembly into supramolecular A/B/C triblock copolymers, the morphology of the resulting block copolymers, and their disassembly. The individual blocks are synthesized in a controlled or living fashion via ring-opening metathesis polymerization (ROMP) of norbornenes (block B) or atom-transfer radical polymerization (ATRP) of styrenes (block A) and methacrylates (block C). The building blocks are assembled via metal-coordination between blocks A and B using a palladated SCS pincer complex and pyridine, and hydrogen bonding between blocks B and C using Hamilton Wedge and barbituric acid derivatives. Scanning-transmission electron microscopy and small-angle X-ray scattering reveal lamellar domains of approximately 23, 15, and 21 nm for bulk samples of the A/B and B/C diblock copolymers and A/B/C triblock copolymers, with 1:1 and 1:1:1 block feed ratios, respectively. Nanoscale features are destroyed when the materials are exposed to dimethylformamide and/or triphenylphospine, removing noncovalent linkages between individual blocks.