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

Abstract

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 molecularweights and narrow polydispersity index. The resulting polymers showed highly extended conformations both in solution and in the solid state, even with relatively small thirdgeneration 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.

Poly(oxanorbornenedicarboximide)s dendronized with amphiphilic poly(alkyl ether) dendrons

“…The distance between branch points in the amphiphilic poly(alkyl ether) dendrons is much smaller than the distance between branch points in the Percec‐type dendrons, and this is likely why the amphiphilic poly(alky ether) dendrons appear to impose a greater steric burden on the polymerization than the Percec‐type dendrons. Poly(norbornene)s dendronized with one polyester dendron on each repeat unit exhibit features characteristic of a linear polymer backbone fully encapsulated by a dendritic sheath . Because the branching unit structure of the polyester dendrons is similar to the branching unit of the poly(alkyl ether) dendrons, we chose to attach a single dendron to the polymerizable group.…”

“…The molecular weight characteristics in Table and Figure are also expected for living ROMP. The group of Fréchet and coworkers have shown through chain extension experiments that polymerizations of dendritic norbornene macromonomers and of bis‐dendritic 7‐oxanorbornene macromonomers initiated by Grubbs‐type catalysts are indeed living. We infer from our results that the polymerizations reported herein are also examples of living ROMP.…”

Synthesis of novel cyclic olefin polymers with excellent transparency and high glass-transition temperature via gradient copolymerization of bulky cyclic olefin andcis-cyclooctene

“…Gradient copolymers are a unique class of polymer materials that have gradual changes in monomer composition along their backbones . The common and easy method to prepare gradient copolymers is using two monomers having large differences in reactivity in one pot (batch) . However, If the reactivity differences of these two monomers are too large, block or qusi‐block copolymers are often obtained.…”

Cationic Bottlebrush Polymers from Quaternary Ammonium Macromonomers by Grafting‐Through Ring‐Opening Metathesis Polymerization

“…ROMP also has demonstrated a wide functional group tolerance to produce well‐defined bottlebrush block copolymers with MMs carrying heteroatom functional groups through sequential ROMP 43–46. Well‐controlled MMs are needed for well‐defined bottlebrush polymers and they have been synthesized from a variety of techniques, which suppress side reactions of norbornene incorporation, such as reversible addition‐fragmentation chain transfer (RAFT) polymerization,47–49 atom transfer radical polymerization (ATRP),50–52 living anionic polymerization (LAP),53,54 ring‐opening polymerization (ROP),55 and other types of polymerizations 56,57. Thus, a wide library of potential MMs exist to create new bottlebrush block copolymers.…”