Chain extension of center-functionalized polystyrene via radical-radical coupling: Periodic introduction of complementary hydrogen bonding interaction site on polymer chain

In this work, our purpose was directed to syntheses of unique polystyrene (PSt) periodically carrying complementary hydrogen-bonded interaction sites in the chain. First, a bifunctional (bi-headed) initiator carrying three-point complementary hydrogen bonding sites (Cl-DAD-Cl: D = hydrogen donor; A = hydrogen acceptor) was employed for ruthenium-catalyzed living radical polymerization of styrene. Precise control of the polymerization allowed quantitative introduction of the DAD unit at the center and Cl capping group at the terminals for the resultant PSt chain as well as narrow molecular weight distribution. Generation of concentrated radical species from the C-Cl bonds at the both terminals in the absence of monomer induced radical-radical coupling reaction between the styryl radical species for "chain extension". Since molecular weight distribution of the precursor was enough narrow (M-w/M-n < 1.10) and the DAD unit was quantitatively incorporated at the central position, the resultant polymer chains carried the complementary interaction site at regular interval corresponding to the chain length (molecular weight) of the precursor. The position-controlled polystyrene chain interacted with poly(methyl methacrylate) having the complementary interaction unit (ADA) at the center to give supramolecular graft copolymer. (C) 2014 Elsevier Ltd. All rights reserved.