Design and Synthesis of Triblock Copolymers for Creating Complex Secondary Structures by Orthogonal Self-Assembly

We herein report the synthesis and characterization of ABC-type triblock copolymers containing two complementary association motifs and investigate their folding into well-defined polymeric nanoparticles under diluted conditions via intramolecular orthogonal hydrogen bonding. The precursor ABC-type triblock copolymers are prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization bearing primary alkyl bromide on A, protected alkyne on B, and protected hydroxyl pendant groups on the C units. The dithioester groups of the RAFT polymers are quantitatively removed by radical-induced reduction before the side-chain functionalization. The complementary motifs, i.e., Hamilton wedge (HW, A block), benzene-1,3,5-tricarboxamide (BTA, B block), and cyanuric acid (CA, C block), are incorporated into the linear triblock copolymers side chains via postfunctionalization. The self-assembly processes of the HW and CA supramolecular motifs are followed by nuclear magnetic resonance (1H NMR) spectroscopy at ambient and elevated temperature in various solvents. The helical BTA stack formation is monitored by circular dichroism (CD) spectroscopy. In addition, the final aggregates formed by these two orthogonal forces, namely HW-CA pseudo-cross-linking and BTA stacking, are characterized by static and dynamic light scattering (SLS and DLS) as well as atomic force microscopy (AFM). © 2015 American Chemical Society