Supramolecular Helix–Helix Block Copolymers
2016-09-28T19:07:55Z (GMT) by
Two chemically distinct monotelechelic helical polymers were synthesized using anionic and reversible addition–fragmentation chain-transfer (RAFT) polymerizations. A chiral poly(isocyanide) block was obtained using a palladium–ethynyl complex modified with the N1,N3-bis(6-butyramidopyridin-2-yl)-5-hydroxyisophthalamide (Hamilton wedge) moiety as a catalyst employing anionic polymerization. A complementary barbiturate-functionalized chain-transfer agent was used to polymerize chiral N-(1-(naphthalen-2-yl)ethyl)methacrylamides by RAFT polymerization. The assembly into helix–helix supramolecular block copolymers in chloroform via hydrogen bonding was analyzed by 1H NMR spectroscopy, resulting in an average measured association constant of (9.5 ± 0.5) × 103 M–1. After block copolymer formation, the secondary structures of both helical polymers were maintained within the block copolymer, as evidenced by circular dichroism and infrared spectroscopies. Films were prepared from a 1:1 mixture of polymers in solution and were analyzed by WAXS and DSC to evaluate organization in the solid state. While diblock formation in the solution phase is readily obtainable, there was little evidence supporting a self-assembly assisted microstructure in the solid state. This work demonstrates a synthetic methodology for obtaining two telechelic helical polymers capable of supramolecular assembly in solution toward the goals of developing multifunctional polymeric ensembles.