Synthesis of Dendronized Polymers via Macromonomer Approach by Living ROMP and Their Characterization: From Rod-Like Homopolymers to Block and Gradient Copolymers

Dendronized polymers were synthesized from various endo-tricycle[4.2.2.0]deca-3,9-diene (TD) monomers, using a macromonomer approach, via ring-opening metathesis polymerization. The polymerization was achieved in a living manner to give dendronized polymers with high molecular-weights and narrow polydispersity index. The resulting polymers showed highly extended conformations both in solution and in the solid state, even with relatively small third-generation ester dendrons, because of the rigid backbone of TD monomers. Using their rigidity, block and gradient copolymers containing TD and norbornene moieties were synthesized. Diblock copolymers were produced by the sequential addition of two dendronized macromonomers, and gradient copolymers were produced in a simple batch reaction, because large differences in reactivity allowed for the simultaneous one-pot polymerization, favoring TD over norbornene. Polymer conformations were confirmed by both scattering analysis in solution and atomic force microscopy (AFM) imaging in thin films. The high-resolution AFM images of both copolymers enabled us to distinguish the structural differences between the two classes of copolymers because the block copolymer showed clear boundary for each block while the gradient copolymer showed gradual changes in height and thickness. Furthermore, a comparison of the rigidities of these two copolymers was performed by scattering analysis in solution.