Branched Polymers via ROMP of Termimers

Abstract

the desired chemical moiety. In the living ring-opening metathesis polymerization employing Grubbs' ruthenium carbene complexes the reactive site is the propagating catalyst species, i.e., the ruthenium alkylidene complex. However, when utilizing ruthenium carbene complexes, their high tolerance towards oxygen, water and many polar functional groups impede the desired transformation into a functional end group since the number of potential reactants other than olefi ns is limited. Thus, what is generally considered one of the great advantages of ruthenium catalyzed olefi n metathesis is a slight disadvantage in this particular case.Nonetheless, several methods have been recently reported by our group that allow the mono end-functionalization of ROMP polymers with specifi c functional groups such as alcohols, [ 10,11 ] aldehydes and carboxylic acids, [ 12 ] thiols, [ 13 ] and amines. [ 14 ] By end-functionalizing living ROMP polymers using a cyclohexene derivative, a catalytic living ring opening metathesis process could even be achieved. [ 15 ] Synthesizing these end-functional polymers becomes especially useful when using them as macroinitiators for multiblock copolymer syntheses, building blocks for model networks or as macromonomers or prepolymers to reach very high molecular weights in subsequent polymerizations.Here, we describe the synthesis of a functionalizable cis -vinyl ether end-capping reagent that allows the Today's olefi n metathesis catalysts show high reactivity, selectivity, and functional group tolerance and allow the design of new syntheses of precisely functionalized polymers. Here the synthesis of a new end-capping reagent is investigated allowing the introduction of a highly reactive activated ester end-group at the polymer chain end as well as its prefunctionalization to directly introduce functional moieties. The versatility of this new end-capping reagent is demonstrated by utilizing it to synthesize a so-called termimer (a monomer with termination capabilities). Copolymerization of a norbornene derivative with the termimer leads to hyperbranched ring-opening metathesis polymerization polymers as proven by gel permeation chromatography and MALDI-ToF-(matrix-assisted laser desorption/ ionization time of fl ight) mass spectrometry.

Enolesters as chain end‐functionalizing agents for the living ring opening metathesis polymerization

“…A cis-selective synthesis of a functionalizable chain terminating agent based on vinyl ethers was recently reported. 24 Considering our previous findings that vinyl lactones reacted rapidly and regioselectively with ruthenium carbene complexes 11 we hypothesized that acyclic enolesters and in particular functional enolesters could be suitable and readily accessible terminating agents for living ROMP. Here, we report the synthesis of enolester derivatives and their use as functional chain termination agents in living ROMP.…”

“…A high cis ‐content in these vinyl ethers is, however, crucial to achieve rapid termination as the cis ‐vinyl ethers react significantly faster with the ruthenium alkylidene than the trans ‐vinyl ethers. A cis‐selective synthesis of a functionalizable chain terminating agent based on vinyl ethers was recently reported …”

Convergent Synthesis of Branched Metathesis Polymers with Enyne Reagents

“…The considerable success of ROMP to synthesize highmolecular-weight bottlebrush polymers via grafting-through methods presents a promising opportunity to utilize Knauss' convergent synthesis concept to metathesis-derived materials. Recognizing this potential, Kilbinger and co-workers 35 first explored the convergent branching strategy with ROMP in 2016 through the use of an exo-norbornene imide monomer linked to an enol ether terminator. Unfortunately, the internal olefin of enol ether displayed slow rates of termination relative to the propagation of the norbornene monomer, resulting in an inseparable mixture of low-molecular-weight linear, three-arm star, and semidendritic branched polymers.…”

ROMP of supramolecular norbornene monomers containing β-cyclodextrin–ferrocene (/adamantane) inclusion complexes

“…Thus, using this technique, various well-defined homopolymers and copolymers, whose polydispersity indexes (PDIs) are normally less than 1.2, can be prepared for all kinds of functional applications, such as their use in drug delivery [7], bioimaging [8], and catalysis [9], along with their preparation as nanoparticles [10] and hydrogels [11]. Through the use of norbornene-based monomers, polynorbornenes with various types of configurations can be synthesized, such as brush polymers [12], dendronized polymers [13], branched polymers [14], star polymers [15], ladderphanes [16], and multicyclic polymers [17][18][19]. The extensive application of ROMP is attributed to the high group tolerance of Grubbs' catalyst [1,20].…”