Sacrificial Synthesis of Hydroxy-Telechelic Metathesis Polymers via Multiblock-Copolymers

The synthesis of well-defined telechelic ring-opening metathesis polymers has been achieved by Sacrificial Synthesis. With the formation of cleavable triblock-copolymers, precise control over the molecular weight and the degree of functionalization was achieved. Introducing cleavable monomers that can be addressed separately, sequential deprotection was accomplished which opened the path to more sophisticated polymeric materials bearing different substituents at their respective chain ends. Sacrificial penta- and heptablock-copolymers are also presented which allow the synthesis of well-defined telechelic polymers in good yields and significantly improved initiator efficiency.

Thiol-functionalized ROMP polymers via Sacrificial Synthesis

The synthesis of well-defined and highly functionalized thiol-functionalized polymers has been accomplished via the ring-opening metathesis polymerization (ROMP). A sacrificial synthesis-based approach was chosen for this interesting functional group since it has proven to give precise control over molecular weight and selective placement of end-groups on a different functionality before. Thiol-functionalized ROMP-polymers were successfully synthesized employing thioacetal monomers, which can be cleaved by hydrogenation leaving the desired thiol group behind. The placement of this highly reactive functional group at one chain end of a poly(norborneneimide) is demonstrated by analytical meth…

Monofunctional metathesis polymers via sacrificial diblock copolymers.

End Capping Ring-Opening Olefin Metathesis Polymerization Polymers with Vinyl Lactones

The selective placement of a functional group at the chain end of a ring-opening metathesis polymer using ruthenium carbene initiators has been a significant limitation. Here we demonstrate a highly effective and facile end-capping technique for ROMP with living ruthenium carbene chain ends using single-turnover olefin metathesis substrates. Vinylene carbonate and 3H-furanone are introduced as functionalization and termination agents for the ruthenium-initiated ring-opening metathesis polymerization. This leads directly to the formation of functional polymer end groups without further chemical transformation steps. Aldehyde and carboxylic acid end groups can be introduced by this new method…

Heterotelechelic Ring-Opening Metathesis Polymers

By combining sacrificial synthesis with the vinyl lactone termination technique, heterotelechelic polymers were synthesized. The nonterminating nature of sacrificial synthesis was utilized to introduce a hydroxyl group at the start of the polymer chain. Lactone termination was used to functionalize the chain ends with aldehydes or carboxylic acids. The synthesis of well-defined heterotelechelic polymers was thus accomplished employing the Grubbs’ first generation catalyst as the initiator. The living nature of this polymerization allowed for precise control over the molecular weight and guaranteed full functionalization of both polymer chain ends. The presence of the functional groups is sh…

An All-ROMP Route to Graft Copolymers

A new versatile synthesis strategy for macromonomers has been developed that uses the living ring-opening metathesis polymerization (ROMP) with commercial Grubbs first generation ruthenium initiators. Homopolymers as well as diblock copolymers were end-functionalized with norbornene derivatives to serve as macromonomers. The graft copolymerization of the macromonomers was also carried out employing ROMP. Well-defined and highly functional graft copolymers are accessible by this new synthetic route.

A “click” approach to ROMP block copolymers

Amphiphilic block copolymers can be conveniently prepared via convergent syntheses, allowing each individual polymer block to be prepared via the polymerization technique that gives the best architectural control. The convergent “click-chemistry” route presented here, gives access to amphiphilic diblock copolymers prepared from a ring opening metathesis polymer and polyethylene glycol. Because of the high functional group tolerance of ruthenium carbene initiators, highly functional ring opening metathesis polymerization (ROMP) polymer blocks can be prepared. The described synthetic route allows the conjugation of these polymer blocks with other end-functional polymers to give well-defined a…

Monofunktionalisierte Metathesepolymere durch Abbau von Diblockcopolymeren

Functional end groups for polymers prepared using ring-opening metathesis polymerization.

The precise placement of functional groups on the chain-ends of macromolecules is a major focus of polymer research. Most common living polymerization techniques offer specific methods of end-functionalization governed by the active propagating species and the kinetics of the polymerization reaction. Ring-opening metathesis polymerization has established itself as one of the most functional-group-tolerant living polymerization techniques known, but this tolerance has limited the number of available functionalization reactions. Metathesis chemists have therefore been required to develop a variety of end-functionalizations, adapting each of them to the reactivity scheme of the particular cata…

Janus Micelles Induced by Olefin Metathesis

A facile one-step procedure for hydrophobic modification and simultaneous TEM contrast enhancement via a regioselective olefin metathesis reaction using Grubbs' catalyst is presented. Polyether diblock copolymers were investigated, and both the chain ends of the hydrophilic and the hydrophobic block were hydrophobically modified. Modification of the hydrophilic block results in nonsymmetric supramolecular structures (Janus micelles) which self-assemble into larger hierarchically organized super-micelles.

Polymerizable Well-Defined Oligo(thiophene amide)s and their ROMP Block Copolymers

We report the synthesis of conjugated thiophene amide oligomers that constitute a new class of chromophores with potential for optoelectronic applications. The synthesis of defined norbornene-substituted oligothiophene amides using conventional coupling chemistry is described. Their electronic properties depend on the degree of oligomerization as UV/Vis and fluorescence spectroscopy demonstrate. A significant red shift in the spectra upon an increase in the oligomer length evidences conjugation of the thiophene rings via the amide linkages. ROMP of the norbornene-substituted oligomers gives homopolymers and block-copolymers with a solubilizing second block. The amphiphilic character of the …

Long-chain branched ROMP polymers

This article describes the construction of branched ROMP-polymer architectures via polycondensation of ABn-type macromonomers. For this convergent strategy, a polymer was synthesized that carries several hydroxyl-groups along the polymer chain and one carboxylic acid group at the chain end. An esterification reaction between these functional groups yielded long-chain branched polymers. The polymers were analyzed by NMR and SEC to monitor the condensation reaction. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009

Electroactive linear-hyperbranched block copolymers based on linear poly(ferrocenylsilane)s and hyperbranched poly(carbosilane)s.

A convenient two-step protocol is presented for synthesis of linear-hyperbranched diblock copolymers consisting of a linear, organometallic poly(ferrocenylsilane) (PFS) block and hyperbranched poly(carbosilane) (hbPCS) segments. Linear PFS diblock copolymers were synthesized through photolytic ring-opening polymerization of dimethyl[1]silaferrocenophane as the first block and methylvinyl[1]sila-ferrocenophane as the second. These block copolymers served as polyfunctional cores in a subsequent hydrosilylation polyaddition of different silane-based AB 2 monomers. Three AB 2 monomers (methyldiallylsilane; methyldiundecenylsilane, and ferrocenyldiallylsilane) were investigated; they introduced …