42069-15-8Relevant articles and documents
Supramolecular X-shaped homopolymers and block polymers by midsegment complementary hydrogen bonds: Design of bifunctional initiators with interactive sites for metal-catalyzed living radical polymerization
Lee, Sang-Ho,Ouchi, Makoto,Sawamoto, Mitsuo
experimental part, p. 3702 - 3710 (2012/08/13)
Two polymer chains, each carrying a complementary multiple hydrogen-bonding site at the center, led to supramolecular block copolymers where two segments are connected in an X-shaped configuration. For the precision synthesis of the pairing precursor polymers, a set of bifunctional initiators were designed, X-DAD-X and Y-ADA-Y, that consist of three hydrogen bond-forming sites in series (DAD or ADA; D = hydrogen donor; A = hydrogen acceptor) and two initiating sites (X or Y) for ruthenium-catalyzed living radical polymerization; thereby, DAD and ADA units are complementary to each other upon supramolecular association. Typically, DAD is of an -NH-C-N-C-NH- unit derived from 2,6-diaminopyridine, and ADA is of a -CO-NH-CO- unit from 2′-deoxyuridine. These functionalized initiators initiated living radical polymerizations of methyl methacrylate and styrene to give homopolymers (PMMA and PS, respectively) with a DAD or an ADA unit at the backbone center. Upon mixing in CDCl 3, for example, a pair of complementary polymers, such as PMMA-DAD-PMMA and PS-ADA-PS, formed supramolecular X-shaped block polymers via the multiple hydrogen bond association between their midchain DAD and ADA sites, as demonstrated by in situ 1H NMR (association constant ～102). 1H DOSY analysis also supported the interaction: the association products gave a single diffusion constant, thus behaving as one polymer chain, while each component chain had different diffusion constants.
