Dendrimer-like star-branched polymers: novel structurally well-defined hyperbranched polymers

The precise synthesis of dendrimer-like star-branched polymers (DSPs), a novel class of structurally well-defined hyperbranched polymers, is described. The synthesis uses stepwise iterative methodologies based on the 'arm-first' divergent approach. The first methodology involves two reaction steps: (1) a linking reaction of an alpha-multifunctionalized living polymer(s) either with a core(s) substituted plural number of benzyl bromide (BnBr) functions or a chain-end-(BnBr)(n)-functionalized polymer(s) attached to the repeating unit and (2) a transformation reaction to the BnBr function that is used as the next reaction site. The two steps are repeated to construct high-molecular-weight (1.94 x 10(6) g mol(-1), M-w/M-n = 1.02) and high-generation (seventh generation) DSPs. The second methodology is the same as the first except for the use of a functionalized living AB diblock copolymer instead of the alpha-multifunctionalized living polymer(s). With this methodology, a higher molecular weight (1.43 x 10(7) g mol(-1), M-w/M-n = 1.05) DSP was successfully synthesized, although the number of branch segments was not exactly, rather on average, defined by the living anionic polymerization of the B segment. The resulting DSPs were characterized by right angle laser light scattering (RALLS), small-angle X-ray scattering and viscosity measurements to obtain the hydrodynamic radii, radii of gyration, intrinsic viscosity values and g' values (branching factors). The relationship among such values that reveals the sizes, volumes, shapes, and generation and branched architecture is discussed. To visualize the synthesized DSPs, an atomic force microscopy measurement was attempted. Polymer Journal (2011) 43, 2-17; doi:10.1038/pj.2010.109; published online 17 November 2010