Acyclic dienemetathesis: a versatile tool for the construction of defined polymer architectures

Opper K.L., Markova D., Klapper M., Müllen K., Wagener K.B.

Polyethylene structures containing precisely placed phosphonic acids were synthesized varying both the frequency of acid appearance along the backbone and the architecture associated with each position. Single, geminal, and benzyl attachment schemes are described with symmetry of placement being an important feature. Altering these precision primary structures has a direct effect on secondary structure where changes in thermal behavior become obvious, particularly in terms of crystallization behavior. It is evident that strong interactions between polymer chains exist, effecting polymer crystallization and solubility depending upon both the length of methylene run-lengths between symmetrically placed acids and whether or not the acid group is protected as the ester or free to participate in hydrogen bonding, which directly influences interchain interaction.

Matloka P.P., Kean Z., Wagener K.B.

The combination of both chain-internal/chain-end latent crosslinking in a single thermoset polymer system is the subject of this study. A series of linear carbosiloxane/hydrocarbon homopolymers were synthesized by metathesis polycondensation, polymers which serve as the soft phase in the target chain-internal/chain-end latent crosslinked materials. These carbosiloxane/hydrocarbon “soft phase” homopolymers exhibited excellent performance parameters, displaying purely amorphous character with glass transition temperatures ranging between −104 °C and −90 °C depending on the run length of siloxane or hydrocarbon methylene units within the carbosiloxane/hydrocarbon monomer. These soft phase monomers were then copolymerized with latent chain-internal crosslinking carbosilane monomers in the presence of latent chain-end crosslinking molecules thereby generating a new class linear copolymers capable of being moisture cured to produce a new class of silicon-based thermoset systems. Mechanical properties of these thermosets, show breaking strengths up to 0.5 MPa and elongations up to 100%. Both elastic and plastic behavior can be observed in such systems, depending upon the molar ratio of carbosiloxane/hydrocarbon co-monomer and the carbosilane co-monomer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1866–1877, 2010

Biermann U., Metzger J.O., Meier M.A.

High oleic sunflower oil, a renewable raw material consisting of triglycerides with internal CC-double bonds, was polymerized via acyclic triene metathesis (ATMET) to highly branched and functionalized polyesters. If the Hoveyda–Grubbs second generation catalyst was used and methyl acrylate was introduced as a chain stopper, the molecular weight of the obtained polymers could be tuned by varying the ratio of the triglyceride and methyl acrylate. Using the first generation Grubbs catalyst for the polymerization of high oleic sunflower oil, no cross-linking was observed, even without the use of a chain stopper. The resulting branched materials were characterized by GPC, 1H and 13C NMR, and ESI-MS.

de Espinosa L.M., Meier M.A., Ronda J.C., Galià M., Cádiz V.

An α,ω-diene containing hydroxyl groups was prepared from plant oil-derived platform chemicals. The acyclic diene metathesis copolymerization (ADMET) of this monomer with a phosphorus-containing α,ω-diene (DOPO II), also plant oil derived, afforded a series of phosphorus containing linear polyesters, which have been fully characterized. The backbone hydroxyls of these polyesters have been acrylated and radically polymerized to produce crosslinked polymers. The thermomechanical and mechanical properties, the thermal stability, and the flame retardancy of these phosphorus-based thermosets have been studied. Moreover, methyl 10-undecenoate has been used as chain stopper in selected ADMET polymerizations to study the effect of the prepolymers' molecular weights on the different properties of the final materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1649–1660, 2010

Mutlu H., Meier M.A.

Castor oil is, as many other plant oils, a very valuable renewable resource for the chemical industry. This review article provides an overview on this specialty oil, covering its production and properties. More importantly, the preparation, properties and major application possibilities of chemical derivatives of castor oil are highlighted. Our discussion focuses on application possibilities of castor oil and its derivatives for the synthesis of renewable monomers and polymers. An overview of recent developments in this field is provided and selected examples are discussed in detail, including the preparation and characterization of castor oil-derived polyurethanes, polyesters and polyamides.

Aitken B.S., Lee M., Hunley M.T., Gibson H.W., Wagener K.B.

Zhan X., Zhu D.

In this review we summarize the most recent developments in conjugated polymers for high-efficiency organic photovoltaic devices. We focus on correlations of polymer chemical structures with properties, which may guide rational structural design and evaluation of photovoltaic materials.

Leonard J.K., Turek D., Sloan K.B., Wagener K.B.

Fokou P.A., Meier M.A.

Rojas G., Inci B., Wei Y., Wagener K.B.

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.

Schwendeman J.E., Wagener K.B.

Amorphous, hydrophobic telechelic hydrocarbon diols were synthesized using acyclic diene metathesis (ADMET) polymerization. These diols can be used in hydrolysis and UV resistant polyurethanes. The hydrocarbon backbone is based on a mimic of an ethylene/isobutylene polymer, made by the ADMET polymerization of a gem-dimethyl substituted α,ω-diene followed by hydrogenation of the polymer's repeat unit unsaturation. Chain termination reactants (CTR's) having one, three, and nine methylene spacers, respectively, between their olefin and alcohol precursor group were used to cap the polymer chain ends to yield 2.0 functional telechelics. Use of the medium length CTR in a polymerization-depolymerization scheme, resulted in amorphous (Tg = -56°C) telechelic diols with good molecular weight control.

De Espinosa L.M., Ronda J.C., Galià M., Cádiz V., Meier M.A.

The acyclic diene metathesis (ADMET) polymerization of a phosphorus-containing α,ω-diene prepared from a plant oil derived building block is reported. Different ruthenium based metathesis catalysts and conditions were tested to optimize the ADMET polymerization of this monomer. Undecylenyl undecenoate was used as fully renewable comonomer to obtain polyesters with different phosphorus contents and to increase the renewable content of the final polymers. Copolymerization caused marked variations in the molecular weights leading to polyesters from 6 to 38 KDa. The effect of the ADMET polymerization temperature in the thermal properties of the copolymers was studied and their thermal degradation and flame retardant properties were evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5760–5771, 2009

Voit B.I., Lederer A.

“Life is branched” was the motto of a special issue of Macromolecular Chemistry and Physics1 on “Branched Polymers”, indicating that branching is of similar importance in the world of synthetic macromolecules as it is in nature. The significance of branched macromolecules has evolved over the last 30 years from just being considered as a side reaction in polymerization or as a precursor step in the formation of networks. Important to this change in perception of branching was the concept of “polymer architectures”, which formed on new starand graft-branched structures in the 1980s and then in the early 1990s on dendrimers and dendritic polymers. Today, clearly, controlled branching is considered to be a major aspect in the design of macromolecules and functional material. Hyperbranched (hb) polymers are a special type of dendritic polymers and have as a common feature a very high branching density with the potential of branching in each repeating unit. They are usually prepared in a one-pot synthesis, which limits the control on molar mass and branching accuracy and leads to “heterogeneous” products with a distribution in molar mass and branching. This distinguishes hyperbranched polymers from perfectly branched and monodisperse dendrimers. In the last 20 years, both classes of dendritic polymers, dendrimers as well as hb polymers, have attracted major attention because of their interesting properties resulting from the branched architecture as well as the high number of functional groups.2 The challenging synthesis of the dendrimers attracted especially scientists with a strong organic chemistry background and led to beautifully designed macromolecules, which allowed a deeper insight into the effect of branching and functionality. Dendrimers have been considered as perfect “nano-objects” where one can control perfectly size and functionality, which is of high interest in nanotechnology and biomedicine. hb polymers, however, were considered from the beginning as products suitable for larger-scale application in typical polymer fields like coatings and resins, where a perfect structure is sacrificed for an easy and affordable synthetic route. Thus, the first structures that were reported paralleled the chemistry used for linear polymers like typical polycondensation for polyester synthesis. More recently, unconventional synthetic methods have been adopted also for hb polymers and related structures. Presently, a vast variety of highly branched structures have been realized and studied regarding their properties and potential application fields. Excellent reviews appeared covering synthesis strategies, properties, and applications, like the very recent tutorial by Carlmark et al.,3 the comprehensive book on hyperbranched polymers covering extensively synthesis and application * E-mail: voit@ipfdd.de; lederer@ipfdd.de. Chem. Rev. 2009, 109, 5924–5973 5924

Delgado P.A., Zuluaga F., Matloka P., Wagener K.B.

Choi H.J., Jeong K., Chien L., Lee M.

A chemically programmed photochromic liquid crystal (LC) polymer was newly synthesized and used to fabricate an actuator exhibiting reversible photo-activated bending behavior at ambient temperature. Due to the lack of chemical crosslinking in this photochromic LC elastomer, it was possible to fabricate an actuator in the form of fiber or film by melt or solution processing, respectively. The three-dimensional (3D) bending of the film actuator can be precisely controlled in various directions by polarized ultraviolet (UV) light. The novel photochromic LC elastomer, exhibiting reversible photomechanical bending with controlled directions at room temperature, is beneficial for the realization of wireless remote-controlled 3D actuators.

McCleary-Petersen K.C., Wiegand K.R., Taleff M.T., Guironnet D.

Guo Y., Yang C., Zhang L., Hu Y., Hao J., Jia C., Yang Y., Xu Y., Li X., Mo F., Li Y., Houk K.N., Guo X.

Olefin metathesis, as a powerful metal-catalysed carbon–carbon bond-forming method, has achieved considerable progress in recent years. However, the complexity originating from multicomponent interactions has long impeded a complete mechanistic understanding of olefin metathesis, which hampers further optimization of the reaction. Here, we clarify both productive and hidden degenerate pathways of ring-closing metathesis by focusing on one individual catalyst, using a sensitive single-molecule electrical detection platform. In addition to visualizing the full pathway, we found that the conventionally unwanted degenerate pathways have an unexpected constructive coupling effect on the productive pathway, and both types of pathway can be regulated by an external electric field. We then pushed forward this ability to ring-opening metathesis polymerization involving more interactive components. With single-monomer-insertion-event resolution, precise on-device synthesis of a single polymer was achieved by online manipulation of monomer insertion dynamics, intramolecular chain transfer, stereoregularity, degree of polymerization and block copolymerization. These results offer a comprehensive mechanistic understanding of olefin metathesis, exemplifying infinite opportunities for practical precise manufacturing. Single-molecule electrical detections clarify both productive and hidden degenerate pathways of ring-closing metathesis, and enable precise on-device synthesis of a single polymer with single-monomer-insertion-event resolution.

Thai L.D., Kammerer J.A., Golberg D., Mutlu H., Barner-Kowollik C.

Mandal I., Kilbinger A.F.

AbstractMost metathesis polymers based on norbornene derivatives carry a vinyl end group. Here we show that these vinyl end groups readily undergo a degenerative exchange of the terminal methylene unit in the presence of sub‐stoichiometric amounts of a propagating metathesis polymer carrying a Grubbs ruthenium complex. We show that this degenerative exchange can be exploited in synthesizing ROMP polymers in a catalytic living fashion. Chain transfer agents based on styrene, or monosubstituted conjugated 1,3 diene derivatives are used as initiating sites for the catalytic living polymerization. Suitable derivatives of these chain transfer agents not only allow the linear living growth of polymers but also the synthesis of block copolymers from macro‐initiators or star polymers from multi‐functional chain transfer agents. This reversible exchange mechanism offers a cheaper, greener, and more sustainable alternative for the synthesis of living ROMP polymers compared to the classical synthetic route.

Mandal I., Kilbinger A.F.

AbstractMost metathesis polymers based on norbornene derivatives carry a vinyl end group. Here we show that these vinyl end groups readily undergo a degenerative exchange of the terminal methylene unit in the presence of sub‐stoichiometric amounts of a propagating metathesis polymer carrying a Grubbs ruthenium complex. We show that this degenerative exchange can be exploited in synthesizing ROMP polymers in a catalytic living fashion. Chain transfer agents based on styrene, or monosubstituted conjugated 1,3 diene derivatives are used as initiating sites for the catalytic living polymerization. Suitable derivatives of these chain transfer agents not only allow the linear living growth of polymers but also the synthesis of block copolymers from macro‐initiators or star polymers from multi‐functional chain transfer agents. This reversible exchange mechanism offers a cheaper, greener, and more sustainable alternative for the synthesis of living ROMP polymers compared to the classical synthetic route.

Antonova Alexandra S., Zubkov Fedor I.

Catalytic olefin metathesis using Hoveyda-Grubbs type ruthenium complexes is a powerful tool for creating complex molecules possessing a variety of practically useful properties. This method is also applied for obtaining modern polymer materials from low-demand petroleum products. Among all ruthenium complexes containing five- or six-membered chelate rings, the commercially available HG-II catalyst is the most common. In addition, other Hoveyda-Grubbs type complexes, which include a Het→Ru donor–acceptor bond in the chelate ring, often exhibit metathesis activity equal to or superior to that of HG-II. This review considers second-generation N-heterocyclic ruthenium carbene Hoveyda-Grubbs type complexes with donor–acceptor bonds such as O→Ru, S→Ru, Se→Ru, N→Ru, P→Ru and Hal→Ru in the chelate ring. Methods of preparation, analysis of stability and catalytic activity of such complexes are compared, and examples of the application of these organometallic ruthenium derivatives in the synthesis of practically relevant products are provided. The literature from 2010 to 2023 is summarized, making this review useful for a broad audience of chemists working in heterocyclic and organometallic chemistry, as well as practitioners involved in the production of catalysts and polymers.The bibliography includes 174 references.

Döpping D., Kern J., Rotter N., Llevot A., Mutlu H.

Nomura K., Kuwahara S., Suthala J., Kawamoto Y., Shimoyama D., Buchmeiser M.R.

[V(N-2,6-Cl2C6H3)(CHSiMe3)(OC6X5)(NHC)] exhibited remarkable catalytic activities for ROMP of norbornene at 25 °C to afford ring-opened polymers not only with high cis-(93–98%) selectivity, but also with exclusive syndiotactic stereo-regularity.

Behtash F., Mogheri F., Aghaee A., Seyed Hajizadeh H., Kaya O.

Abstract Background Boron (B) is a micronutrient, but excessive levels can cause phytotoxicity, impaired growth, and reduced photosynthesis. B toxicity arises from over-fertilization, high soil B levels, or irrigation with B-rich water. Conversely, silicon (Si) is recognized as an element that mitigates stress and alleviates the toxic effects of certain nutrients. In this study, to evaluate the effect of different concentrations of Si on maize under boron stress conditions, a factorial experiment based on a randomized complete block design was conducted with three replications in a hydroponic system. The experiment utilized a nutrient solution for maize var. Merit that contained three different boron (B) concentrations (0.5, 2, and 4 mg L−1) and three Si concentrations (0, 28, and 56 mg L−1). Results Our findings unveiled that exogenous application of B resulted in a substantial escalation of B concentration in maize leaves. Furthermore, B exposure elicited a significant diminution in fresh and dry plant biomass, chlorophyll index, chlorophyll a (Chl a), chlorophyll b (Chl b), carotenoids, and membrane stability index (MSI). As the B concentration augmented, malondialdehyde (MDA) content and catalase (CAT) enzyme activity exhibited a concomitant increment. Conversely, the supplementation of Si facilitated an amelioration in plant fresh and dry weight, total carbohydrate, and total soluble protein. Moreover, the elevated activity of antioxidant enzymes culminated in a decrement in hydrogen peroxide (H2O2) and MDA content. In addition, the combined influence of Si and B had a statistically significant impact on the leaf chlorophyll index, total chlorophyll (a + b) content, Si and B accumulation levels, as well as the enzymatic activities of guaiacol peroxidase (GPX), ascorbate peroxidase (APX), and H2O2 levels. These unique findings indicated the detrimental impact of B toxicity on various physiological and biochemical attributes of maize, while highlighting the potential of Si supplementation in mitigating the deleterious effects through modulation of antioxidant machinery and biomolecule synthesis. Conclusions This study highlights the potential of Si supplementation in alleviating the deleterious effects of B toxicity in maize. Increased Si consumption mitigated chlorophyll degradation under B toxicity, but it also caused a significant reduction in the concentrations of essential micronutrients iron (Fe), copper (Cu), and zinc (Zn). While Si supplementation shows promise in counteracting B toxicity, the observed decrease in Fe, Cu, and Zn concentrations warrants further investigation to optimize this approach and maintain overall plant nutritional status.

Yang Y., Cho Y., Choi T.

AbstractCascade metathesis polymerization has been developed as a promising method to synthesize complex but well‐defined polymers from monomers containing multiple reactive functional groups. However, this approach has been limited to the monomers involving simple alkene/alkyne moieties or produced mainly non‐degradable polymers. In this study, we demonstrate a complete cascade ring‐opening/ring‐closing metathesis polymerization (RORCMP) using various tricycloalkenes and two strategies for the efficient degradation. Through rational design of tricycloalkene monomers, the structure and reactivity relationship was explored. For example, tricycloalkenes with trans configuration in the central ring enabled faster and better selective cascade RORCMP than the corresponding cis isomers. Also, a 4‐substituted cyclopentene moiety in the monomers significantly enhanced the overall cascade RORCMP performance, with the maximum turnover number (TON) reaching almost 10,000 and molecular weight up to 170 kg/mol using an amide‐containing monomer. Furthermore, we achieved one‐shot cascade multiple olefin metathesis polymerization using tricycloalkenes and a diacrylate, to produce new highly A,B‐alternating copolymers with full degradability. Lastly, we successfully designed xylose‐based tricycloalkenes to give well‐defined polymers that underwent ultra‐fast and complete degradation under mild conditions.

Yang Y., Cho Y., Choi T.

AbstractCascade metathesis polymerization has been developed as a promising method to synthesize complex but well‐defined polymers from monomers containing multiple reactive functional groups. However, this approach has been limited to the monomers involving simple alkene/alkyne moieties or produced mainly non‐degradable polymers. In this study, we demonstrate a complete cascade ring‐opening/ring‐closing metathesis polymerization (RORCMP) using various tricycloalkenes and two strategies for the efficient degradation. Through rational design of tricycloalkene monomers, the structure and reactivity relationship was explored. For example, tricycloalkenes with trans configuration in the central ring enabled faster and better selective cascade RORCMP than the corresponding cis isomers. Also, a 4‐substituted cyclopentene moiety in the monomers significantly enhanced the overall cascade RORCMP performance, with the maximum turnover number (TON) reaching almost 10,000 and molecular weight up to 170 kg/mol using an amide‐containing monomer. Furthermore, we achieved one‐shot cascade multiple olefin metathesis polymerization using tricycloalkenes and a diacrylate, to produce new highly A,B‐alternating copolymers with full degradability. Lastly, we successfully designed xylose‐based tricycloalkenes to give well‐defined polymers that underwent ultra‐fast and complete degradation under mild conditions.

Jia B., Zhang B., Li J., Qin J., Huang Y., Huang M., Ming Y., Jiang J., Chen R., Xiao Y., Du J.

We highlight the recent progress and design strategies of polymeric materials with tailored functions to overcome the highly movable and wet, microbial and inflammatory environment in the oral cavity for treatment of oral diseases.

Li X., Mahadas N.A., Zhang M., DePodesta J., Stefik M., Tang C.

High-density polyethylene (HDPE) is among the most voluminous commodity plastic, which has received increasing public scrutiny about its impact on environment and climate change. There have been many efforts to recycle HDPE chemically, though significant hurdles remain. Toward a closed-loop economy, it is considered appealing to design "HDPE-like" materials, which contain built-in degradable groups and preserve thermal and mechanical properties like HDPE. This review provides a concise overview of three major areas: HDPE recycling methods, preparation of "HDPE-like" materials, and perspective towards more sustainable polymers. Each section includes a few inspiring achievements and challenges of the past decade.

Kellner-Rogers J.S., Wang R., Lambert T.H.

Cheng-Sánchez I., Moya-Utrera F., Sarabia F.