ADMET Polymerization Research Articles

Convenient divergent synthesis of linear-dendron block polyphosphoesters via acyclic diene metathesis polymerization

ADMET polymerization was successfully applied for the synthesis of linear-dendritic polyphosphoester structures by using macromolecular chain stoppers.

Bio‐Based Aliphatic Polyurethanes Through ADMET Polymerization in Bulk and Green Solvent

A new route to α,ω-diene urethane monomer is proposed by converting 10-undecenoic acid into the corresponding acyl azide, followed by urethanization with 10-undecenol. ADMET polymerizations of this α,ω-diene urethane monomer as well as other bio-based α,ω-dienes bearing various organic functions (ester, carbonate, ether, amide) were carried out in bulk and solution conditions. A screening of the most commonly used metathesis catalysts allows to evaluate their tolerance toward the urethane function as well as toward Polarclean, a "green" and nontoxic high boiling point solvent. The influence of the nature of the central organic function in these α,ω-diene monomers on the thermomechanical properties is investigated.

Immobilization of antioxidants via ADMET polymerization for enhanced long-term stabilization of polyolefins

Novel macromolecular antioxidants with multiple hindered phenolic antioxidant moieties along a linear, unsaturated olefinic backbone are prepared and their antioxidative ability in polypropylene (PP) blends is investigated. Firstly, α,ω-diene monomers bearing one alcohol functionality are prepared from 10-undecenoic acid, sourced from the renewable resource castor oil, and are subsequently coupled to hindered phenolic antioxidants to prepare antioxidant bearing α,ω-diene monomers. The preparation of macromolecular antioxidants is then described, via ADMET polymerization of the hindered phenol bearing monomers. Upon blending with polypropylene, the resultant blends show excellent antioxidative stabilization in comparison to commercially available antioxidants and thus represent promising additives for the long-term stabilization of polyolefins in extreme environments, for example in the construction of solar water heating systems.

Renewable co-polymers derived from vanillin and fatty acid derivatives

Renewable monomers derived from vanillin and fatty acids have been studied as monomers in ADMET, thiol-ene addition, and polycondensation type polymerization reactions. Both synthesized monomers and polymers were adequately characterized by NMR, DSC, and GPC. The synthesis of polymers via ADMET was optimized with regard to the applied catalyst and catalyst loading. Remarkably, it turned out that ADMET polymerizations led to high molecular weights (up to 50kDa), whereas thiol-ene polyaddition and polycondensation led to polymers with molecular weight up to 15 and 17kDa, respectively. Thermoplastic materials with melting points in the range from 15.8 to 77.8°C and Tgs in the range from −37.0 to −13.6°C were thus obtained.

Synthesis of Poly(3-dodecyl-2,5-thienylene vinylene) by Solid-State Metathesis Polycondensation

The synthesis of poly(thienylene vinylenes) (PTV) has been attracting attention due to the low band gaps and high electrical conductivities of these materials, making them applicable for charge storage devices, transparent conductive coatings, and electrochromic devices. Unsubstituted PTV is an intractable polymer that is usually synthesized via a processable precursor. This article reports the synthesis of conjugated polymers using solid-state metathesis conditions, demonstrating the efficiency of this methodology for preparation of a processable polymer, such a 3-dodecyl PTV (P3DDTV). The 3-dodecyl-2,5-dipropenylthiophene was synthesized and subsequently polymerized using ADMET conditions with Grubbs’ second-generation catalyst. The prepolymer film (Mn = 4000 g/mol) was further polymerized in the solid state to give a final product with Mn = 14 000 g/mol (a 3.5-fold increase while in the solid state). The polymer obtained by this methodology exhibited thermal (Tg = 43 °C and Tm = 115 °C) and electrochemical (optical band gap of 1.65 eV and HOMO energy level of 5.35 eV) properties similar to those of PTV polymers synthesized by ADMET polymerization using a high boiling solvent or by cross-coupling reactions.

One-Pot Synthesis of Polyrotaxanes via Acyclic Diene Metathesis Polymerization of Supramolecular Monomers

A one-pot synthesis of polyrotaxanes has been developed. The method employs a supramolecular monomer comprising a polymerizable ammonium salt and crown ether, in combination with dynamic ADMet polymerization. Ultimately, highly efficient complexation, polymerization, and end-capping were accomplished in a single operation to yield polyrotaxanes with M(w) up to 19.3 kDa and >80% of the repeat units being complexed.

Aliphatic Long‐Chain C20 Polyesters from Olefin Metathesis

Self-metathesis of undecenoic acid with [(PCy3)2Cl2Ru=CHPh] (2), followed by exhaustive hydrogenation yielded pure 1,20-eicosanedioic acid (5) (>99%) free of side-products from isomerization. Polycondensation with eicosane-1,20-diol (6), formed by reduction of the diol, yielded polyester 20,20 (Tm = 108 °C). By comparison, the known ADMET polymerization of undec-10-enyl undec-10-enoate (7), and subsequent exhaustive polymer-analogous hydrogenation yielded a polyester (poly-8) with irregular structure of the ester groups in the polymer chain (-O(C=O)- vs. -C(=O)O-) (Tm = 103 °C). Hydrogenation of secondary dispersions of poly-7 yielded aqueous dispersions of the long-chain aliphatic polyester poly-8.

Renewable Polyethylene Mimics Derived from Castor Oil

An increasing number of reports on the syntheses of carbohydrate- and plant oil-based polymers has been published in ongoing efforts to produce plastic materials from renewable resources. Although many of these polymers are biodegradable and this is a desirable property for certain applications, in some cases non-degradable polymers are needed for long-term use purposes. Polyolefins are one of the most important classes of materials that have already taken their places in our daily life. On the other hand, their production relies on fossil resources. Therefore, within this contribution, we discuss synthetic routes toward a number of polyethylene mimics derived from fatty acids via thiol-ene and ADMET polymerization reactions in order to establish more sustainable routes toward this important class of polymers. Two different diene monomers were thus prepared from castor oil derived platform chemicals, their polymerization via the two mentioned routes was optimized and compared to each other, and their thermal properties were investigated.

4-Vinylbenzenesulfonic acid adduct of epoxidized soybean oil: Synthesis, free radical and ADMET polymerizations

In this work new radically polymerizable triglyceride based monomers were synthesized by the reaction of epoxidized methyl oleate (EMO) and epoxidized soybean oil (ESO) with 4-vinyl benzene sulfonic acid (4VBSA). The products are 1-(4-vinylbenzene sulfonyl)oxy-2-alkonols of epoxidized soybean oil (SESO) and 1-(4-vinylbenzene sulfonyl)oxy-2-alkonols of epoxidized methyl oleate (SEMO). These adducts were characterized by 1H NMR, 13C NMR, IR and CHNS elemental analysis. SESO was found to contain, on the average, 2.47 4VBSA units per triglyceride. SESO was free radically polymerized and co-polymerized with styrene and the mechanical and thermal properties of the resulting thermosets were determined by DMA, DSC and TGA. SEMO was used as a model compound to determine the efficiency of metathesis catalysts for these fatty acid derivatives. The second generation Hoveyda–Grubbs catalyst was found to give best yields. ADMET polymerization of SESO with this catalyst with and without solvent gave ∼80% yield of a thermoset polymer. Polymers obtained by free radical route swelled in water at room temperature, and hydrolyzed in water at 60 °C.

Synthesis of star- and block-copolymers using ADMET: head-to-tail selectivity during step-growth polymerization

Control over molecular architectures obtained via ADMET polymerization is limited by the step-growth nature of this technique. A new approach to this polycondensation method is described allowing for the synthesis of diblock and star-shaped polymers with molecular weight control by using the selectivity of olefin cross-metathesis between acrylates and terminal olefins.

Fats and oils as renewable feedstock for the chemical industry

The Paris UN climate conference from 30 November to 11 December 2015 has delivered a new universal climate change agreement. The aim of this new agreement is to put the world firmly on track to a low-carbon, sustainable future that keeps the global temperature rise under 2°C, as claimed by the UN Framework Convention on Climate Change. The increasing and sustainable use of renewable feedstocks on the way to this ambitious goal is of utmost importance. Thus, a few days earlier, the Global Bioeconomy Summit 2015 “Making Bioeconomy Work for Sustainable Development” held by the German Bioeconomy Council took place from 25th to 26th of November in Berlin, Germany. This event was the first community building platform to discuss bioeconomy policies globally. The UN Food and Agriculture Organisation, the EU Commission and the German Government endorsed this special event and the German Chancellor, Angela Merkel, had assumed patronage. She stated in her welcome address: “The number of people in the world is growing, whereas the earth’s natural resources are limited. This simple fact poses one of the greatest challenges we face today: how can we succeed in meeting the needs of present and future generations alike? A biobased economy offers a promising prospect. It relies on renewable resources and scientific findings. This means that renewable resources and biotechnological processes primarily help to safeguard food security and are also used to generate sustainable energy and in industrial manufacturing.” The Global Economy Summit issued a communiqu e addressing the key areas of action, inter alia: “Bioeconomy innovations are driven by research that allows for rapid progress in the life sciences and related knowledge areas. Combining knowledge in biosciences with inventions in chemistry, energy, primary industry, information technology as well as in engineering, is crucial and especially promising.” Equally important and interesting, the G7-Alliance on Resource Efficiency held the conference “Innovative Biobased Products: Opportunities for substituting non-renewable resources” two days earlier in Berlin. At the G7 summit held in Schloss Elmau on 7th and 8th of June 2015 under the German Presidency, the heads of state and government of Germany, France, Italy, the United Kingdom, Japan, Canada and the United States recognized the importance of the conservation and efficient use of natural resources, in particular for the industry’s competitive capacity and for environmental and climate protection. To support knowledge sharing and best practice, they founded the “G7 Alliance on Resource Efficiency” with the goal of conserving natural resources and of using them effectively. Sustainably produced renewable resources can substitute fossil resources and hence make an essential contribution to their conservation and climate protection. Remarkably, the sustainable use of renewable resources has become a hot topic of global politics. Fats and oils, including terpenes, are, beside carbohydrates and lignin, the most important renewable feedstock available from biomass. EJLSTpublished a yearly special issue “Fats andOils as Renewable Feedstock for the Chemical Industry” since seven years based on the respective international workshops organized in Emden andKarlsruhe/Germany. The 8th Workshop on Fats and Oils as Renewable Feedstock for the Chemical Industry took place March 29–31, 2015 inKarlsruhe, Germany, organized by abiosus e.V. in cooperation with the Agency of Renewable Resources (FNR), Germany. Thirty lectures and more than forty posters provided an update on the newest developments in the field of fats and oils as renewable feedstock for the chemical industry. 15 papers were selected for this special issue.

Studying and Suppressing Olefin Isomerization Side Reactions During ADMET Polymerizations

Olefin isomerization side reactions that occur during ADMET polymerizations were studied by preparing polyesters via ADMET and subsequently degrading these polyesters via transesterification with methanol. The resulting diesters, representing the repeating units of the previously prepared polyesters, were then analyzed by GC-MS. This strategy allowed quantification of the amount of olefin isomerization that took place during ADMET polymerization with second generation ruthenium metathesis catalysts. In a second step, it was shown that the addition of benzoquinone to the polymerization mixture prevented the olefin isomerization. Therefore, second generation ruthenium metathesis catalysts may now be used for the preparation of well-defined polymers via ADMET with very little isomerization, which was not possible before.

Precision Polyethylene: Changes in Morphology as a Function of Alkyl Branch Size

Metathesis polycondensation chemistry has been employed to control the crystalline morphology of a series of 11 precision-branched polyethylene structures, the branch being placed on each 21st carbon and ranging in size from a methyl group to an adamantyl group. The crystalline unit cell is shifted from orthorhombic to triclinic, depending upon the nature of the precision branch. Further, the branch can be positioned either in the crystalline phase or in the amorphous phase of polyethylene, a morphology change dictated by the size of the precision branch. This level of morphology control is accomplished using step polymerization chemistry to produce polyethylene rather than conventional chain polymerization techniques. Doing so requires the synthesis of a series of unique symmetrical diene monomers incorporating the branch in question, followed by ADMET polymerization and hydrogenation to yield the precision-branched polyethylene under study. Exhaustive structure characterization of all reaction intermediates as well as the precision polymers themselves is presented. A clear change in morphology was observed for such polymers, where small branches (methyl and ethyl) are included in the unit cell, while branches equal to or greater in mass than propyl are excluded from the crystal. When the branch is excluded from the unit cell, all such polyethylene polymers possess essentially the same melting temperature, regardless of the size of the branch, even for the adamantyl branch.

Unsaturated PA X,20 from Renewable Resources via Metathesis and Catalytic Amidation

AbstractThe synthesis of unsaturated polyamides that can be obtained from plant oil derivatives via two different approaches is described. First, long chain aliphatic α,ω‐dienes with two symmetrically spaced amide segments were polymerized via ADMET polymerization. Secondly, dimethyl(E)‐icos‐10‐enedioate, a bio‐based unsaturated monomer that was obtained via metathesis, was polymerized with different aliphatic diamines using strong organic bases, such as TBD, as catalysts. Both reaction pathways led to unsaturated PA X,20 and the two different routes were investigated, optimized and compared. Moreover, the polymers were characterized by 1H NMR analysis and SEC, and the properties of the resulting polyamides were investigated by DSC and TGA.magnified image

Use of a Renewable and Degradable Monomer to Study the Temperature-Dependent Olefin Isomerization during ADMET Polymerizations

A detailed study of temperature, catalyst, and polymerization condition dependent isomerization side reactions occurring during ADMET polymerizations revealed important parameters for the design of defined polymers via this technique.

Well-Defined Precision Ethylene/Vinyl Fluoride Polymers: Synthesis and Crystalline Properties

Here we report the synthesis and crystalline structure of a family of three precision ethylene/vinyl fluoride (EVF) polymers with fluorine atoms on each and every 9th, 15th, and 21st carbon via ADMET polymerization, followed by exhaustive hydrogenation. The primary structure of the polymers is confirmed by NMR, TGA, IR, and elemental analysis. The crystallization pattern of these systems is analogous to that of homopolymers as evidenced by the equivalent halogen content in amorphous and crystalline regions, as obtained by solid-state NMR. This is supported by SAXS periodicities that conform with layered crystalline−amorphous structures of folded chains. While the thickness of the amorphous layer is small (∼45 A) and constant within the series, the crystallite thicknesses (∼200−100 A) decrease with increasing fluorine. The latter, and the depression of crystallinity, equilibrium melting, and heat of fusion with increasing content of F attest to the restrictions of this halogen, although of a small volume, ...

Preparation of Photodegradable Oligomers Containing Metal–Metal Bonds Using ADMET

ADMET was evaluated as a method for preparing organometallic polymers with metal–metal bonds in the main chain. The Cp2Mo2CO4(Ph2P(CH2)6CH=CH2)2 complex was synthesized, and the X-ray crystal structure is reported. The molecule did not undergo ADMET polymerization with Grubbs’ or Schrock’s catalysts. In a control experiment to test if the Ph2P(CH2)6CH=CH2 ligand was interfering with the ADMET reaction, the phosphine was reacted with Grubbs’ 2nd generation catalyst. The dimerized metathesis product Ph2P(CH2)6CH=CH(CH2)6PPh2 was obtained with no observed degradation or deactivation of the catalyst. To test the inherent ADMET reactivity of the Ph2P(CH2)6CH=CH2 ligand when it is bonded to a metal center, the mononuclear cis-Mo(CO)4(Ph2P(CH2)6CH=CH2)2 complex was synthesized and polymerized using Grubbs’ 2nd generation catalyst. These control experiments suggest that the inability of Cp2Mo2CO4(Ph2P(CH2)6CH=CH2)2 to polymerize is not due to electronic effects pertaining to the C=C unit of the Ph2P(CH2)6CH=CH2 ligand. Accordingly, steric effects are implicated in the inability of the Cp2Mo2CO4(Ph2P(CH2)6CH=CH2)2 to polymerize by ADMET.

Bifunctional [c2]Daisy-Chains and Their Incorporation into Mechanically Interlocked Polymers

A strategy for the formation of mechanically interlocked polymers is presented. Ring-closing olefin metathesis has been shown to provide a very high yielding route to [c2]daisy-chains suitably functionalized to allow their one-step conversion to bisolefins which can be used as monomers in ADMET polymerizations to afford mechanically interlocked polymers. Metathesis, in two different guises is making a hitherto unreachable goal in synthesis a reality.

Synthesis of Cyclolinear Poly(carbosilane)-g-poly(methyl methacrylate or styrene) Random Copolymers

The cyclolinear polycarbosilane, (poly(1-hexyl-1,3-ditolyl-1,3-disilacyclobutane) poly(HDTDSCB)), which has tolyl groups attached to the main chain Si atoms, was prepared by ADMET polymerization with the second-generation Grubbs catalyst, and 10%, 5%, and 2% of the tolyl groups were brominated by reactions with N-bromosuccinimide. A series of well-controlled poly(methyl methacrylate) (PMMA) anions of 2.5K, 5K, and 10K molecular weight were introduced via the “grafting onto” strategy at low temperature to the randomly 10%, 5%, and 2% brominated poly(HDTDSCB), respectively, without any lithiation or ring opening of the disilacyclobutane in the main chain. Because of side reactions initiated by the PS anion under similar conditions, a “grafting from” strategy by ATRP was employed to yield the corresponding poly(HDTDSCB)-g-PS random copolymers. The product poly(HDTDSCB)-g-(PMMA or PS) random copolymers were purified by using total adsorption−desorption interaction chromatography, which involves selective adso...

The utility of Hoveyda-type catalysts in ADMET chemistry: Sterics versus electronics

The influence of the ligand sphere's electronics/sterics on catalytic activity was investigated at various temperatures for complexes of the type (L)(Cl) 2Ru = CH( o- iPrOC 6H 3X) (L = H 2IPr or H 2IMes, X = NO 2, Cl, H, CH 3, OCH 3). Their kinetic behavior was evaluated under ADMET polymerization conditions. At all temperatures the steric hindrance brought about by the N-heterocyclic carbene H 2IPr dominates any electronic effect as initial rates remain constant regardless of the X substituent. Nevertheless, complexes bearing electron donating groups seem to be more stable and result in higher DPs than complexes bearing electron withdrawing groups. In any case, catalysts containing larger NHC ligands are more efficient in ADMET chemistry than any modified Hoveyda–Grubbs catalyst. At 60 °C, the electronic factor becomes evident and the substituted catalysts exhibit significantly higher reactivity, resulting in the fastest initial rates ever witnessed in an ADMET reaction.