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While depolymerizable polymers have been intensely pursued as a potential solution to address the challenges in polymer sustainability, most depolymerization systems are characterized by a low driving force in polymerization, which poses difficulties for accessing diverse functionalities and architectures of polymers. Here, we address this challenge by using a cyclooctene-based depolymerization system, in which the cis -to- trans alkene isomerization significantly increases the ring strain energy to enable living ring-opening metathesis polymerization at monomer concentrations ≥ 0.025 M. An additional trans -cyclobutane fused at the 5,6-position of the cyclooctene reduces the ring strain energy of cyclooctene, enabling the corresponding polymers to depolymerize into the cis -cyclooctene monomers. The use of excess triphenylphosphine was found to be essential to suppress secondary metathesis and depolymerization. The high-driving-force living polymerization of the trans -cyclobutane fused trans -cyclooctene system holds promise for developing chemically recyclable polymers of a wide variety of polymer architectures.

Materials capable of degradation upon exposure to light hold promise in a diverse range of applications including biomedical devices and smart coatings. Despite the rapid access to macromolecules with diverse compositions and architectures enabled by ring-opening metathesis polymerization (ROMP), a general strategy to introduce facile photodegradability into these polymers is lacking. Here, we report copolymers synthesized via ROMP that can be degraded by cleaving the backbone in both solution and solid states under irradiation with a 52 W, 390 nm Kessil LED to generate heterotelechelic low-molecular-weight fragments. To the best of our knowledge, this work represents the first instance of the incorporation of acylsilanes into a polymer backbone. Mechanistic investigation of the degradation process supports the intermediacy of an α-siloxy carbene, formed via a 1,2-photo Brook rearrangement, which undergoes insertion into water followed by cleavage of the resulting hemiacetal.

This research was focused on the synthesis of core-shell bottlebrush polymer poly(PCL-b-PEG) (PCL: polycaprolactone; PEG: polyethylene glycol) through a combination of ring-opening polymerization (...

Summary Conjugated polymers possess unique optoelectrical properties. Characterizing their synthesis and mechanical processability is crucial for tailored applications. Their poor solubility presents a universal challenge, however. Here, we report a single-molecule study, which circumvents the solubility challenge, of the polymerization kinetics and conformational mechanics of polyacetylene, a prototypical conjugated polymer. We monitor the growth of individual long-chain polyacetylenes during ring-opening metathesis polymerization of cyclooctatetraene. We discover that polyacetylene forms nonequilibrium conformational entanglements, whose kinetic instability and structural looseness appear to render its polymerization more facile than that of polycyclooctene, a nonconjugated analog. This relative kinetics is contrary to monomer reactivity predictions. Moreover, even under identical solvent conditions, individual polyacetylenes show diverse extension-versus-force scaling behaviors; many span multiple scaling regimes predicted previously but never observed. The extracted persistence and Kuhn length of polyacetylene are also significantly shorter than its wavefunction delocalization length, indicating that polyacetylene can maintain backbone conjugation while staying flexible.

There is growing interest in the detection of bacteria in consumables, for example, in the food and water sectors. In this study, the aim was to produce a polymer-based bacteria biosensor via ROMP (ring opening metathesis polymerization). In the first part of the study, block and random copolymers were synthesized, and their biocidal activities were tested on the glass surface. Interdigitated electrode arrays coated with the polymers possessing the highest activity were used to screen the affinity towards different bacterial strains by monitoring impedance variations in real-time. The polymer-coated electrode could detect gram-positive and gram-negative bacteria strains at a concentration of 10(7) cfu/mL. The results show that ROMP-based polymer offers bacterial detection and can be used in developing biosensor devices for efficiently detecting pathogenic bacteria.

The understanding and control of stereoselectivity is a central aspect in ring-opening metathesis polymerization (ROMP). Herein, we report detailed quantum chemical studies on the reaction mechanism of E-selective ROMP of norborn-2-ene (NBE) with Mo(N-2,6-Me2-C6H3)(CHCMe3)(IMes)(OTf)2 (1, IMes = 1,3-dimesitylimidazol-2-ylidene) as a first step to stereoselective polymerization. Four different reaction pathways based on an ene syn or ene anti approach of NBE to either the syn- or anti-isomer of the neutral precatalyst have been studied. In contrast to the recently established associative mechanism with a terminal alkene, where a neutral olefin adduct is formed, NBE reacts directly with the catalyst via [2 + 2] cycloaddition to form molybdacyclobutane with a reaction barrier about 30 kJ mol-1 lower in free energy than via the formation of a catalyst-monomer adduct. However, the direct cycloaddition of NBE was only found for one out of four stereoisomers. Our findings strongly suggest that this stereoselective approach is responsible for E-selectivity and point toward a substrate-specific reaction mechanism in olefin metathesis with neutral Mo imido alkylidene N-heterocyclic carbene bistriflate complexes.

Frontal ring-opening metathesis polymerization was used to in situ prepare polydicyclopentadiene (PDCPD)/carbon nanotubes (CNTs) and PDCPD/CNT-NH2 composites with high glass transition temperature. Compared with PDCPD/CNT composites, PDCPD/CNT-NH2 composites have similar dielectric constants, but their loss tangent significantly reduces. The uniform dispersion of CNT-NH2 leads to the formation of dielectric interfacial polarization. The results of dynamic mechanical analysis (DMA) showed that the glass transition temperature (Tg) of the composites increased with the increase of filler. With the increase of the filler, the elongation at break of the PDCPD/CNT composites decreased, while the elongation at break of PDCPD/CNT-NH2 composites increased, reaching up to 17% because of the stronger interfacial affinity. The PDCPD/CNT-NH2 composites exhibited high dielectric permittivity (47.5 at a frequency of 100 Hz) that originates from the interfacial polarization between PDCPD and CNT-NH2, and the nonconducting –NH2 groups can prevent the conductive path of CNTs and support a low loss tangent (0.096). High Tg PDCPD/CNT-NH2 composite with enhanced dielectric properties was prepared by a simple and quick one-step reaction method of FROMP. Keywords: Polydicyclopentadiene; Composites; Carbon nanotubes; Dielectric properties, Interfacial polarization

Ring-opening metathesis polymerization (ROMP) of buckybowl corannulene-based oxa-norbornadiene monomer is shown to give rise to polymeric nanomaterials with an average pore size of about 1.4 nm and a surface area of 49.2 m2/g. Application in supercapacitor devices show that the corannulene-based nanomaterials exhibit a specific capacitance of 134 F·g–1 (1.0 V voltage window) in a three-electrode cell configuration. Moreover, the electrode assembled from these materials in a symmetric configuration (1.6 V voltage window) exhibits long-term cyclability of 90% capacitance retention after undergoing 10000 cycles. This work demonstrates that ROMP is a valuable method in synthesizing nanostructured corannulene polymers, and that materials based on the nonplanar polycyclic aromatic motif represents an attractive active component for fabrication of devices targeted at electrochemical energy storage applications. Accepted version

A series of hydroxyl-terminated polyethylenes (HTPE) bearing various functional side groups (e.g. carboxyl, ester and butane groups) were synthesized by the combination of ring-opening metathesis polymerization (ROMP) and visible light photocatalytic thiol-ene reaction. The products are named as α, ω-dihydroxyl-poly[(propionyloxythio)methinetrimethylene] (HTPEcarboxyl), α, ω-dihydroxyl-poly[(methylpropionatethio) methinetrimethylene] (HTPEester) and α, ω-dihydroxyl-poly[(butylthio) methinetrimethylene] (HTPEbutane), respectively. The investigation of ROMP indicated that the molecular weight of resultant hydroxyl-terminated polybutadiene (HTPB) can be tailored by varying the feed ratios of monomer to chain transfer agent (CTA). The exploration of the photocatalytic thiol-ene reaction between HTPB precursor and methyl 3-mercaptopropionate revealed that blue light as well as oxygen accelerated the reaction. 1H-NMR and 13C-NMR results verified all the double bonds in HTPB can be modified, and the main chain of resultant polymer can be considered as polyethylene. Subsequently, relationship between the structure of side groups and the thermal properties of functional PEs was studied. And the results suggested that the Tg was in the order of HTPEbutane

Stereochemistry can have a profound impact on polymer and materials properties. Unfortunately, straightforward methods for realizing high levels of stereocontrolled polymerizations are often challenging to achieve. In a departure from traditional metal-mediated ring-opening metathesis polymerization (ROMP), we discovered a remarkably simple method for controlling alkene stereochemistry in photoredox mediated metal-free ROMP. Ion-pairing, initiator sterics, and solvation effects each had profound impact on the stereochemistry of polynorbornene (PNB). Simple modifications to the reaction conditions produced PNB with trans alkene content of 25 to >98 %. High cis content was obtained from relatively larger counterions, toluene as solvent, low temperatures (-78 °C), and initiators with low Charton values. Conversely, smaller counterions, dichloromethane as solvent, and enol ethers with higher Charton values enabled production of PNB with high trans content. Data from a combined experimental and computational investigation are consistent with the stereocontrolling step of the radical cationic mechanism proceeding under thermodynamic control.

A series of biomass-derived levoglucosenyl alkyl ethers (alkyl = methyl, ethyl, n-propyl, isopropyl, and n-butyl) were synthesized and polymerized by ring-opening olefin metathesis polymerization using the Grubbs catalyst C793 at room temperature. Polymerizations were successfully performed in conventional solvents such as 1,4-dioxane and dichloromethane as well as in polar aprotic “green” solvents such as 2-methyltetrahydrofuran, dihydrolevoglucosenone (Cyrene), and ethyl acetate. The prepared polyacetals with degrees of polymerization of ∼100 exhibit Schulz–Flory-type molar mass distributions and are thermoplastic materials with rather low glass transition temperatures in the range of 43–0 °C depending on the length of the alkyl substituent. Kinetic studies revealed that the polymerization proceeded rapidly to a steady state with a certain minimum monomer concentration threshold. When the steady state was reached, just about half of the [Ru] catalyst had been effective to initiate the polymerization, indicating that the initiation step was a slow process. The remaining catalyst was still active and did no longer react with monomers but with in-chain double bonds, cutting the formed polymer chains into shorter fragments. In the long term, all catalyst was consumed and propagating [Ru] chain ends were deactivated by the elimination of [Ru] from the chain ends to form inactive chains with terminal aldehyde groups.

Polymeric materials modified with tertiary amino groups exhibit attractive properties for use in aqueous environments. Ring-opening metathesis polymerization (ROMP) is one of the versatile tools to...

With very fast polymerization in mild reaction conditions and unique characteristic of double bonds in its synthesized polymer skeleton for further modification and functionalization, ring opening ...

Surface-Initiated Ring-Opening Metathesis Polymerization (SI-ROMP) has attracted great attention in the past two decades because of its high efficiency in decorating material surfaces with functional polymer brushes. To fill the vacancy of review articles in SI-ROMP, this article is aimed at giving an overview of the history, the general features and procedures, and applications of SI-ROMP, guiding future researchers in this field. In general, SI-ROMP consists of three main steps: surface functionalization with olefin anchors, attachment of catalyst to the surface, and polymerization from the surface. Several metal-based catalysts for ROMP in solution have been developed, but most SI-ROMP reactions use the ruthenium-based Grubbs catalysts. SI-ROMP enables the rapid growth of polymer films on a large variety of substrates such as silica, gold, graphene oxides, carbon nanotubes, metal oxide nanowires, and composite polymer membranes. There are many methods to characterize these polymer brushes. In addition, some novel techniques have been developed to precisely control the surface polymer growth and lead to polymer films with unique structures and functions. Up to this day, SI-ROMP can be applied to the surface engineering of many novel materials, including ultrahydrophobic surfaces, microfluidic channels, electric devices, ion exchange media, and responsive surfaces.

Novel bio-derivable tricyclic oxanorbornene polymers, based upon secondary furfurylamine and maleic anhydride derived monomers, prepared via ring opening metathesis polymerization (ROMP) are reported. The tricyclic oxanorbornenes with fused lactam ring are exo Diels–Alder adducts. DFT calculations support the cycloaddition is the first step, followed by lactamization. The polymerizations are rapid and deliver polymers with targeted molar mass and low dispersity (Đ). The prepared polymers with furanyl pendant groups have reactivity towards maleimide-bearing compounds to form thermally induced crosslinked networks through thermoreversible Diels–Alder reactions. The thermoreversible (self-healing) behavior is confirmed by sol gel transition. This new class of bio-derived polymer could be further modified with different active moieties as pendant groups and hence be tailored for more applications in the future.

Olefin metathesis has tremendously impacted all fields of synthetic chemistry. However, the control of the olefin stereochemistry during this process remains a grand challenge. Recent innovations in catalyst design have permitted control of the stereochemistry of the olefin product. Here, we discuss the development of stereoretentive olefin metathesis, with an emphasis on the synthesis of stereodefined polyalkenamers through ring-opening metathesis polymerization (ROMP). We then present our application of this unique reaction manifold to the preparation of all-cis poly(p-phenylene vinylene)s (PPVs). A dithiolate Ru catalyst was found to deliver perfect cis selectivity for the polymerization of a paracyclophane diene monomer. By using optimized conditions, all-cis PPVs with narrow dispersities and predictable molar masses were obtained by varying the ratio of monomer to catalyst. The high chain fidelity of the stereoretentive ROMP with a paracyclophane diene monomer enabled the preparation of well-defined diblock copolymers with a norbornene co-monomer. Photochemical isomerization of all-cis to all-trans PPVs was effected with both homopolymers and diblock copolymers. This process was shown to be selective for the PPV block, and resulted in changes in optical properties, polymer size, and solubility. Stereoretentive ROMP provides a promising platform for synthesizing polymers with unique properties, including photoresponsive all-cis PPVs with living characteristics.1 Introduction2 Synthetic Applications of Stereoretentive Olefin Metathesis3 Stereocontrol of Polyalkenamers through Stereoretentive ROMP4 Stereoretentive ROMP To Access All-cis Poly(p-phenylene vinylene)s5 Conclusion

High molar mass poly(ricinoleic acid) with a weight average molar mass over 400 kg mol−1 was synthesized via entropy-driven ring-opening metathesis polymerization of mono-, di- and mixed macrolactones of ricinoleic acid using a Grubbs second-generation catalyst and fully characterized. The high molar mass was achieved by reducing the catalyst loading, and the resultant polymer product had a very low level of ruthenium (36 ppm as Ru based on G2 feed), was colorless and exhibited a high decomposition temperature without purification steps aimed at removing ruthenium.

The stress–strain properties of polydicyclopentadiene synthesized by ring opening metathesis polymerization are studied depending on the absorbed dose and radiation type. The dependence of the ultimate strength on the absorbed dose has a complex nature. Signs of restoration of the ultimate strength of polydicyclopentadiene in the dose range from 0.4 and 0.7 MGy to the corresponding value of the unirradiated sample are revealed. The ultimate strength of the sample irradiated at a dose of 0.5 MGy is reduced by no more than 12% compared to the unirradiated sample. Other changes in the strength remain within 6.0–0.5%. Polydicyclopentadiene generally behaves as predominantly radiation-resistant. Regardless of the radiation type (electron beam or γ) and manufacturing method, polydicyclopentadiene has the ability to be crosslinked under irradiation. A hypothesis is proposed to explain processes occurring in the structure of the material.

A series of polyethylene-graft-atactic polypropylene (PE-g-aPP) graft copolymers were synthesized by grafting through copolymerization of a cyclooctene terminated aPP macromonomer and cyclooctene using ring opening metathesis polymerization (ROMP) and subsequent hydrogenation. The macromonomer was prepared by a facile alkoxycarbonylation reaction between 1,5-cycooctadiene, hydroxyl terminated aPP and carbon monoxide (CO). Near complete monomer conversion, a near random graft distribution, and relatively low dispersity (Đ < 2.0) were achieved. Thermal analysis of the graft polymers indicates decreasing melting temperatures (Tm) and glass transition temperatures (Tg) as the weight percentage of aPP (WPP) increases. The percent crystallinity (Xc) of PE decreases as aPP content increases, confirmed by differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS) charaterization. The normalized percent crystallinity (Xc,norm) indicates that changing side chain numbers and/or length of aPP do not have a significant impact on PE crystallinity. Small angle X-ray scattering (SAXS) indicates the PE lamellae crystals in the graft copolymers have similar interlamellar spacing but decreased thickness as aPP content increases. In addition, the linear viscoelastic behavior shows that the PE-g-aPP graft copolymers exhibit greatly enhanced dynamic modulus and complex viscosity compared to the linear PE, and the effect increases as side chain number and/or length increases. This work is important for further development of such graft polymers for direct recycling of ubiquitous polyolefins from mixed polyolefin waste.

Porous organic polymers (POPs) are a class of promising materials for overcoming environmental and energy issues worldwide. However, their amorphous nature makes structural characterization in the solid state very challenging. In addition, developing facile synthesis methods and applications for POPs with novel structures remain urgent issues requiring improvement. In this work, novel porous organic polymers (named BIT-POPs) with isolated trans-alkene linkages were synthesized via cross-linking bis-norbornene via ring opening metathesis polymerization (ROMP) in an extremely mild and fast manner. Spectral editing approaches, such as 13C-CPMAS, 13C-CPPI, and 13C-CPNQS, relating to solid-state NMR were used to distinguish the overlapping NMR signals of insoluble BIT-POPs, and two-dimensional 1H–13C HETCOR spectra were used. Also, BIT-POP-5 was added to a polysulfone matrix as a porous filler to form a mixed-matrix membrane, which showed a 126% increase in CO2 permeability during gas separation.

Poly(δ-pinene), PδP, is a promising new material derived from naturally abundant α-pinene. One of the persistent by-products in the synthesis of δ-pinene is α-pinene which required intensive and non-sustainable isocyanate chemistry to fully remove. This work presents an in-depth study on the effects that varying quantities of α-pinene has on the ring opening metathesis polymerization (ROMP) of δ-pinene using Grubbs 3rd generation catalyst (G3). It is determined that G3 is tolerant of low quantities of α-pinene (∼40 equivalents) in the reaction mixture and results in high conversions of δ-pinene and well controlled ROMP. Increasingly higher quantities of α-pinene have an inhibitory effect on conversion and loss of control. 1H NMR experiments revealed complex signals within the Ru-alkylidene and, surprisingly, the ruthenacyclobutane regions of the spectrum as a result of δ-pinene oligomerization. However, no identifiable signals were produced or lost upon interaction with α-pinene suggesting it does not inhibit ROMP through a productive metathesis event.

Synthesis of sequence-controlled poly(ethylene-co-styrene) copolymers is challenging due to the limitations associated with inherent reactivity ratios for ethylene and styrene in catalytic olefin polymerizations. An alternative method to generate ethylene copolymers is ring-opening metathesis polymerization (ROMP) of cyclic olefins followed by hydrogenation, in which a substituted cycloalkene yields polymers analogous to those from copolymerizations of two distinct monomers after post-polymerization hydrogenation. In certain cases, regioregularity (and thus sequence specificity) of these “copolymers” can be realized if the approach of the metathesis catalyst to the monomer occurs regioselectively. In this work, precision polyolefin copolymers were synthesized by ROMP of phenyl-substituted cyclododecenes and subsequent hydrogenation. The effects of the chain transfer agent, monomer structure, target molar mass and reaction conditions on regioselectivity were investigated using 1H and 13C NMR spectroscopies. These investigations of the ROMP of low-strain cyclododecenes provided useful information for the fundamental understanding of mechanistic aspects of the polymerization. Hydrogenation of the polydodecenamers afforded linear low density polyethylenes with a phenyl side chain every twelve backbone carbons.

The incorporation of strained alkynes into polymers is generally achieved by employing step-growth polymerization methods or post-polymerization reactions. Here, we demonstrate that cyclopropenone-masked strained alkynes are tolerant to chain-growth ring-opening metathesis polymerization, and that, upon post-polymerization photochemical demasking with loss of CO, the strained alkyne group appended to each repeating unit can be used to prepare functional (e.g., fluorescent or redox-active) polymers from a common polymer backbone. We support our claims about polymer transformations throughout the manuscript through the inclusion of a complete set of model reactions and characterization data for analogous molecular species. The findings of this study are transferable to other polymeric systems, opening the door to the creation of libraries of multifunctional chain-growth polymers with identical polymer backbones.

This work aims to convert diols into thermosets with tunable properties. A series of diol-derived monomers have been synthesized and characterized. After mixing with second-generation Grubbs’ catalyst, these liquid monomers polymerize completely in two minutes to form cross-linked structures, which benefits rapid manufacture of composites. These diol homolog-based thermosets have good thermal properties and mechanical properties, and their performance can be greatly enhanced by fabricating woven flax fiber composites. We believe these may help researchers design and explore novel promising sustainable diol-based polymers and materials with excellent properties.

the stereospecific ring-opening metathesis polymerization (romp) of endo,exo-2,3-dimethoxymethylnorborn-5-ene (dmmnbe) was accomplished using cationic tungsten imido alkylidene n-heterocyclic carbene (nhc) complexes as initiators. these even outperform a cationic molybdenum imido alkylidene nhc reference initiator and allow for high trans-isospecifity of up to 95%. furthermore, tuning the steric demand of the ligands of the metal complexes allowed for a change in stereoselectivity. thus, for the first time, cis-syndiotactic polymers were synthesized by the action of non-chelating cationic group 6 metal alkylidene nhc complexes. both selectivities were not limited to dmmnbe, but also found for other monomers, namely endo,exo-2,3-dicarbomethoxynorborn-5-ene (dcmnbe), methyl-n-(s)-(−)-α-methylbenzyl-2-azabicyclo[2.2.1]hept-5-ene-3-carboxylate and 2,3-bis[(menthyloxy)carbonyl]norbornadiene.

We report the synthesis of degradable polyacetals and polyketals with controlled molecular weights and low dispersities using alternating ring-opening metathesis polymerization (AROMP) of 1,1-disubstituted cyclopropenes and dioxepins. Under optimized conditions, high degrees of alternation and controlled polymerization were achieved between nonpropagating cyclopropenes and low-strain dioxepins. The high degrees of alternation allowed the resulting polymers to fully degrade into small molecules under acidic conditions at variable rates depending on the acetal/ketal structures. This synthetic strategy illustrates the use of AROMP to incorporate functionalities into both the polymer backbone as well as the side chains.

Polydicyclopentadiene (PDCPD) is a polymer of growing importance in industrial applications. Frontal ring-opening metathesis polymerization (FROMP) offers a means to rapidly cure PDCPD with minimal input energy owing to a propagating reaction wave sustained by the exothermic polymerization. Previous examples of FROMP have required the use of relatively high concentrations of costly ruthenium catalyst, negating many of the benefits of FROMP synthesis. In this contribution, we demonstrate that by using the highly reactive exo-dicyclopentadiene isomer for FROMP the concentration of catalyst is reduced over 3-fold, while maintaining a high frontal velocity. Reducing the amount of ruthenium required for FROMP makes this technique attractive for the production of large PDCPD structural components.

The approach developed here offers distinct and well-defined glycopolymers for deciphering the biological roles of natural bioactive polysaccharides. Fucose monomers were chemically synthesized and decorated with specific sulfation patterns including unsulfate, monosulfate, disulfate, and trisulfate groups. The six fucoidan-mimetic glycopolymers (18–23) were successfully fabricated through microwave-assisted ring-opening metathesis polymerization (ROMP) in an emulsion system. The molecular weight (Mw), polydispersity index (PDI), and multiple functional groups were fully characterized by SEC-MALLS-RI and NMR spectroscopy. Three glycopolymers (19, 21, 23) associated with 2-O-sulfation exhibited better inhibitory effects on the H1N1 virus, while glycopolymers (19, 20) with monosulfate groups were more effective against the H3N2 virus. These findings would promote the development of novel anti-influenza A virus (IAV) drugs based on natural fucoidans.

We report aqueous-phase Ring-Opening Metathesis Polymerization-Induced Self-Assembly (ROMPISA) for forming well-defined micellar polymer nanoparticles at room temperature and high solids concentration (20 w/w%). This is achieved with a new polymerization initiator, in the form of a water-soluble cationic Hoveyda-Grubbs second generation catalyst. This reaction was used in water to produce diblock copolymers from norbornenyl monomers, which then self-assemble into myriad nanostructure morphologies for which a phase diagram was constructed. Additionally, the living nature of the polymerization initiated by the aqueous initiator was confirmed, as shown by kinetic evaluation under mild conditions in water.

In this work, a simple method is reported for control over initiation in frontal ring-opening metathesis polymerization (FROMP). This noncontact approach uses 375 nm light to excite Grubbs' second-generation catalyst in the presence of a phosphite inhibitor. Photoinitiated FROMP of dicylcopentadiene (DCPD) displays a similar cure profile to that of its thermally initiated counterpart, yielding a robust polymer with high glass transition temperature. Furthermore, this system is applied to enhance reaction rates in conventional ring-closing metathesis reactions.

A new general synthetic approach to sequenced macromolecules was developed and applied to the synthesis of polymers comprising lactic acid (L), glycolic acid (G), and e-caprolactone (C)-derived monomer units. The new method employs entropy-driven ring-opening metathesis polymerization (ED-ROMP) to prepare copolymers with embedded sequences and controlled molecular weights. Cyclic macromonomer precursors were prepared by ring-closing metathesis of ethylene glycol (Eg)-linked sequenced oligomers bearing terminal olefins. ED-ROMP of the resulting macrocycles using Grubbs’ second generation catalyst yielded poly(CL-Eg-LC-Oed), poly(CLL-Eg-LLC-Oed), poly(LGL-Eg-LGL-Oed), and poly(LGL-Eg-LGL-Hed) (Oed = octenedioc acid; Hed = hexenedioc acid). Hydrogenation produced the saturated sequenced copolymers. Molecular weight was well-controlled and could be adjusted by varying the monomer-to-catalyst ratio. Mns of 26–60 kDa were obtained (dispersities = 1.1–1.3). The methodology proved general for three different sequ...

Structural evolution from poly(lactide) (PLA) macromonomer to resultant PLA molecular bottlebrush during ring opening metathesis polymerization (ROMP) was investigated for the first time by combining size exclusion chromatography (SEC), small-angle neutron scattering (SANS), and coarse-grained molecular dynamics (CG-MD) simulations. Multiple aliquots were collected at various reaction times during ROMP and subsequently analyzed by SEC and SANS. These complementary techniques enable the understanding of systematic changes in conversion, molecular weight and dispersity as well as structural details of PLA molecular bottlebrushes. CG-MD simulation not only predicts the experimental observations, but it also provides further insight into the analysis and interpretation of data obtained in SEC and SANS experiments. We find that PLA molecular bottlebrushes undergo three conformational transitions with increasing conversion (i.e., increasing the backbone length): (1) from an elongated to a globular shape due to longer side chain at low conversion, (2) from a globular to an elongated shape at intermediate conversion caused by excluded volume of PLA side chain, and (3) the saturation of contour length at high conversion due to chain transfer reactions.

Trimethylated cyclodextrins with a phosphine ligand and ruthenium (PCy2Ru-CDs) realize supramolecular polymerization catalysts for ring-opening metathesis polymerization (ROMP). Although PCy2Ru-βCD shows a low polymerization activity for 7-oxanorbornene dimethanol (7-ONorOH2) in organic solvents, it exhibits a high ROMP activity for 7-ONorOH2 in aqueous solutions. The ROMP activity of PCy2Ru-βCD is higher than that of PCy2Ru-αCD. The addition of competitive guest molecules decreases the polymer yield, indicating that complexation between PCy2Ru-CD and 7-ONorOH2 in water plays an important role in the increased polymer yield.

The controlled synthesis of polymers containing densely grafted cyclodextrin units has proven challenging due to the steric hindrance of these cyclic oligosaccharides. In this study, we report the controlled synthesis of poly(β-cyclodextrin) [poly(β-CD)] through ring-opening metathesis polymerization (ROMP) using Grubbs third-generation catalyst. Molecular weights of10

Well-controlled ring-opening metathesis polymerization (ROMP) of δ-pinene is reported. The monomer is produced through a facile, metal-free, three-step synthesis from highly abundant and sustainable α-pinene. Using Grubbs third-generation catalyst, δ-pinene undergoes ROMP to high conversion (95%) with molar mass up to 70 kg mol