Copolymerization Of Cyclohexene Oxide Research Articles

Cd(ii) and Zn(ii) coordination polymer-assisted CO2/cyclohexene oxide copolymerization with a double metal cyanide catalyst

Three new coordination polymers with Zn(ii) and Cd(ii) metal centers were synthesized and applied to cocatalyze CO2/CHO polymerization with DMC.

Synthesis of Heterometallic Rare Earth(III)–Cobalt(II) Complexes and Their Application in Alternating Copolymerization of Cyclohexene Oxide and Carbon Dioxide

Comprehensive SummaryFour heterometallic rare earth(III)‐cobalt(II) complexes (rare earth = Y (1), Sm (2), Nd (3), La (4)) stabilized by an o‐phenylenediamine‐bridged tris(phenolato) ligand (L) have been synthesized and characterized. In these tetranuclear complexes, one polydentate L coordinates to one rare earth(III) ion, and one cobalt(II) ion, respectively, while two rare earth ions are bridged by four acetate groups. These complexes were applied in the copolymerization of cyclohexene oxide and CO2, which showed good activity (TON up to 440) and high poly(cyclohexene carbonate) selectivity (>99%). Kinetic studies determined the equation as rate = k[CHO]1[CO2]0[initiator]1, which proves a first‐order dependence on initiator concentrations and implies a synergistic mechanism with rare earth and cobalt ions cooperating in epoxide ring‐opening and chain propagation.

Dynamics of Poly(cyclohexene carbonate) as a Function of Molar Mass

Stereoregular poly(cyclohexene carbonate) (PCHC) homopolymers were prepared via copolymerization of cyclohexene oxide and carbon dioxide (CO2) using (R,R)-(salcy)-CoCl and bis(triphenylphosphine)iminium chloride as a catalyst. The homopolymers had molar masses in the range of 4800–33,000 g mol–1 and relatively narrow dispersity after careful fractionation, as required for the molecular dynamics investigation. We employed differential scanning calorimetry and dielectric spectroscopy, the latter as a function of temperature and pressure, for investigating the thermal properties and the molecular dynamics, respectively. The segmental dynamics in the vicinity of the liquid-to-glass temperature was very complex. The dual segmental processes were inseparable by decreasing the temperature or by increasing the pressure. Based on DFT calculations of the dipole moment, they were ascribed to different stereo sequences of the PCHC backbone. The limiting glass temperature, Tg, for very high molar masses was ∼125 °C. The high Tg value obtained herein well justifies its application as a CO2-based alternative for polystyrene (PS) in a variety of materials based on block copolymers. Moreover, fragility increased with increasing molar mass with values intermediate to poly(styrene) and poly(cyclohexyl methacrylate). The flexible cyclohexyl group in PCHC undergoing intramolecular chair-to-chair conversion increases the packing ability and consequently decreases the fragility. PCHC is a brittle material because it lacks entanglements even for the higher molar masses investigated herein, which is relevant for application as a PS substitute. Within the investigated range of molar masses, the dependences of the terminal relaxation times, τΝΜ, and of the zero-shear viscosity, ηο, on the molar mass, M, are τΝΜ/τSM ∼ M3.2 and ηο ∼ M1.4, revealing an intermediate behavior between Rouse and entangled chains.

Synthesis of Diverse Polycarbonates by Organocatalytic Copolymerization of CO2 and Epoxides: From High Pressure and Temperature to Ambient Conditions.

Organophosphazenes combined with triethylborane (TEB) were selected as binary organocatalyts for the copolymerization of CO2 and epoxides. Both the activity and selectivity were highly dependent on the nature of phosphazenes. 2,4,6-Tris[tri(1-pyrrolidinyl)-iminophosphorane]-1,3,5-triazine (C3 N3 -Py-P3 ) with a relatively low basicity (pKa =26.5 in CD3 CN) and a bulky molecular size (φ=1.3 nm) exhibited an unprecedented efficiency (TON up to 12240) and selectivity (>99 % polymer selectivity and >99 % carbonate linkages) toward copolymerization of CO2 and cyclohexene oxide (CHO), and produced CO2 -based polycarbonates (CO2 -PCs) with high molar masses (Mn up to 275.5 kDa) at 1 MPa of CO2 and 80 °C. Surprisingly, this binary catalytic system achieved efficient CO2 /CHO copolymerization with TOF up to 95 h-1 at 1 atm pressure and room temperature.

Living Cationic Ring-Opening Homo- and Copolymerization of Cyclohexene Oxide by “Dormant” Species Generation Using Cyclic Ethers as Lewis Basic Additives

The living cationic ring-opening polymerization of cyclohexene oxide (CHO) was demonstrated to proceed using cyclic ethers as Lewis basic additives that potentially form “dormant” species through a reaction with the CHO-derived propagating species. The polymers obtained under suitable conditions had molecular weights close to the theoretical values and narrow molecular weight distributions. The formation of the dormant species was strongly supported by the generation of chain ends consisting of a cyclic ether additive and a quencher fragment, which was confirmed by 1H NMR and ESI-MS analysis of the product polymers. The use of additives with appropriate basicity, such as hexamethylene oxide and tetrahydropyran, is of considerable importance for living polymerization. In addition, the living copolymerization of CHO and 1,4-epoxycyclohexene and the synthesis of alternating-like acid-degradable polymers with aliphatic aldehydes were also achieved.

Rare-Earth Metal Complexes Supported by Polydentate Phenoxy-Type Ligand Platforms: C-H Activation Reactivity and CO2/Epoxide Copolymerization Catalysis.

Mono- and dinuclear group 3 metal complexes incorporating polydentate bis(imino)phenoxy {N2O}- and bis(amido)phenoxy {N2O}3- ligands were synthesized by alkane elimination reactions from the tris(alkyl) M(CH2SiMe3)3(THF)2 and M(CH2C6H4-o-NMe2)3 (M = Sc, Y) precursors. Complex 1a-Y was used for the selective C-H activation of 2-phenylpyridine at the 2'-phenyl position affording the corresponding bis(aryl) product 3a-Y, which was found to be reacted reluctantly with weak electrophiles (styrene, imines, hydrosilanes). The mechanism of formation of 3a-Y was established by DFT calculations, which also corroborated high stability of the complex toward insertion of styrene, apparently stemming from the inability to form the corresponding adduct. Copolymerization of cyclohexene oxide and CO2 promoted by 1a-Y (0.1-0.5 mol %) was demonstrated to proceed under mild conditions (toluene, 70 °C, PCO2 = 12 bar) giving polycarbonates with high efficiency (maximal TON of 460) and selectivity (97-99% of carbonate units).

Understanding metal synergy in heterodinuclear catalysts for the copolymerization of CO2 and epoxides.

Carbon dioxide and epoxide copolymerization is an industrially relevant means to valorize waste and improve sustainability in polymer manufacturing. Given the value of the polymer products-polycarbonates or polyether carbonates-it could provide an economic stimulus to capture and storage technologies. The process efficiency depends upon the catalyst, and previously Zn(II)Mg(II) heterodinuclear catalysts showed good performances at low carbon dioxide pressures, attributed to synergic interactions between the metals. Now, a Mg(II)Co(II) catalyst is reported that exhibits significantly better activity (turnover frequency > 12,000 h-1) and high selectivity (>99% CO2 utilization and polycarbonate selectivity) for carbon dioxide and cyclohexene oxide copolymerization. Detailed kinetic investigations show a second-order rate law, independent of CO2 pressure from 1-40 bar, to produce polyols. Kinetic data also reveal that synergy arises from differentiated roles for the metals in the mechanism: epoxide coordination occurs at Mg(II), with reduced transition state entropy, while the Co(II) centre accelerates carbonate attack by lowering the transition state enthalpy. This rare insight into intermetallic synergy rationalizes the outstanding catalytic performance and provides a new feature to exploit in other homogeneous catalyses.

Synthesis of Homo- and Heteronuclear Rare-Earth Metal Complexes Stabilized by Ethanolamine-Bridged Bis(phenolato) Ligands and Their Application in Catalyzing Reactions of CO2 and Epoxides.

A series of homonuclear rare-earth (RE) metal complexes (1Y, 2Yb, 3Nd, and 4La) and heteronuclear RE-Zn complexes (1Y-Zn, 3Nd-Zn, and 5Sm-Zn) stabilized by ethanolamine-bridged bis(phenolato) ligands was prepared and structurally characterized. Heteronuclear complexes are assembled through bridging acetate ligands, and their formation and characterization add to the diversity of 3d-4f complexes. Their activities in mediating reactions of CO2 and epoxides were evaluated and compared. Heteronuclear RE-Zn complexes found application in the copolymerization of cyclohexene oxide and CO2, giving rise to acetate-group-capped copolymers. Homonuclear complexes showed good activity in catalyzing the cycloaddition of variously monosubstituted epoxides and CO2 (1 bar), generating cyclic carbonates in 65-96% yield. For sterically hindered disubstituted epoxides, good yields of 60-91% were achieved in the presence of 10 bar CO2.

Air-stable di-nuclear yttrium complexes as versatile catalysts for lactide polymerization and copolymerization of epoxides with carbon dioxide or phthalic anhydride

Four novel di-nuclear yttrium catalysts coordinated by bis(benzotriazole iminophenolate) (BiIBTP) ligands have been synthesized and structurally characterized. The one-pot procedure of BiIBTP pro-ligand with [Y(NO3)3.6H2O] (1.0 equiv.) and 2-nitrophenol derivative (1.0 equiv.) in the presence of triethylamine (5.0 equiv.) under refluxing MeOH solution gave bimetallic yttrium nitrophenolate complexes 1–4, [(μ-BiIBTP)Y(L)]2 (BiIBTP = C13CBiIBTP or C83CBiIBTP; L = 2-nitrophenolate or 2,4-dinitrophenolate) with good to high yields. The solid-state structure of 1 and 3–4 exhibits a di-yttrium(III) di-nitrophenolate species with the pentadentate BiIBTP ligand chelating two metal atoms. Versatile catalysis towards ring-opening polymerization of cyclic ester and copolymerization of internal epoxides with carbon dioxide (CO2) or phthalic anhydride (PA) catalyzed by these di-yttrium nitrophenolate complexes was systematically studied. Experimental results revealed that air-stable complexes 3 and 4 were shown to effectively catalyze not only lactide polymerization but also copolymerization of cyclohexene oxide (CHO) with CO2 or PA. Among these compounds, di-Y complex 4 was the most active catalyst for the ring-opening polymerization of l-lactide in combination with 9-anthracenemethanol, providing poly(l-lactide)s having the expected molecular weight and narrow molecular weight distribution. Furthermore, catalyst 3 was capable of copolymerizing CO2 and CHO in the presence of co-catalysts under mild conditions, producing perfectly alternating poly(cyclohexene carbonate)s with the controllable character. In addition, the molecular weight controllable poly(PA-co-CHO)s with high ester linkage contents could be afforded on copolymerizing PA and CHO utilizing di-yttrium complex 3 as the catalyst. This work provides the facilely synthesized di-nuclear yttrium complexes as versatile catalysts for three different types of polymerization catalysis.

Polynuclear alkoxy-zinc complexes of bowl-shaped macrocycles and their use in the copolymerisation of cyclohexene oxide and CO2.

The reactions between alcohols and the tetranuclear ethyl-Zn complexes of an ortho-phenylene-bridged polypyrrole macrocycle, Zn4Et4(L1) 1 and the related anthracenyl-bridged macrocyclic complex, Zn4Et4(THF)4(L2) 2 have been studied. With long-chain alcohols such as n-hexanol, the clean formation of the tetranuclear hexoxide complex Zn4(OC6H13)4(L1) 3 occurs. In contrast, the use of shorter-chain alcohols such as i-propanol results in the trinuclear complex Zn3(μ2-OiPr)2(μ3-OiPr)(HL1) 4 that arises from demetalation; this complex was characterised by X-ray crystallography. The clean formation of these polynuclear zinc clusters allowed a study of their use as catalysts in the ring-opening copolymerisation (ROCOP) reaction between cyclohexene oxide and CO2. In situ reactions involving the pre-catalyst 1 and n-hexanol formed the desired polymer with the best selectivity for polycarbonate (90%) at 30 atm CO2, whilst the activity and performance of pre-catalyst 2 was poor in comparison.

Effect of Azide and Chloride Binding to Diamino-bis(phenolate) Chromium Complexes on CO2/Cyclohexene Oxide Copolymerization

The affinity for nucleophile (azide, N3–, and chloride, Cl–) binding significantly influences the catalytic activity of chromium complexes for the copolymerization of cyclohexene oxide (CHO) and CO2. The binding of N3– and Cl– to two amino-bis(phenolate) Cr(III) chloride complexes [L1Cr(μ-Cl)]2 (1) and [L2CrCl(THF)] (2·THF), where L1 = methoxyethylamino-N,N-bis(2-methylene-4,6-di-tert-butylphenolate) and L2 = dimethylaminoethylamino-N,N-bis(2-methylene-4,6-di-tert-butylphenolate), were studied by both matrix assisted laser desorption/ionization time-of-flight and electrospray ionization mass spectrometry (MALDI-TOF-MS and ESI-MS, respectively). Upon reaction with [PPN][N3] ([PPN] = bis(triphenylphosphine)iminium), 1 exhibited greater ability to form six-coordinate bis-azide ions [L1Cr(N3)2]− and produced fewer five-coordinate species detected by MS than 2·THF. This corresponded to 2·THF having a significantly faster rate of polymerization with anionic nucleophile cocatalysts than 1. In the presence of 1 e...

Bifunctional Aminotriphenolate Complexes as One‐Component Catalysts for the Ring‐Opening Copolymerization of Cyclic Anhydrides and Epoxides

Bifunctional aminotriphenolate complexes derived from trivalent metals (M = Co, Mn, Cr) have been prepared and structurally characterized. These complexes are octahedral in the solid state but infer dynamic behavior of the ligated dimethylaminopyridine (DMAP) ligands that can function as initiators in the ring‐opening copolymerization of cyclic anhydrides and epoxides. More specifically, the ring‐opening copolymerization of cyclohexene oxide and phthalic anhydride was studied in detail, and the bifunctional CrIII complex gave overall the best results in terms of overall activity and polyester quality.

Cellulosic Cr(salen) complex as an efficient and recyclable catalyst for copolymerization of SO2 with epoxide

The search for green catalytic processes for the synthesis of useful polymers and incorporating the waste SO2 in highly-selective pathways become extremely important in the coming years. Herein, cellulose was modified by ethylenediamine, and then synthesized Schiff base with 3,5-di-tert-butyl-2-hydroxybenzaldehyde to immobilize chromium chloride and formed a novel heterogeneous cellulosic Cr(salen)-type catalyst for the first time. The cellulosic Cr(salen)-type catalyst shows high efficiency and recyclability in copolymerization of cyclohexene oxide with SO2. The influence factors such as the molar ratio of the catalyst and cyclohexene oxide, reaction temperature, and reaction time were researched in detail to study the optimal conditions. The copolymer product was characterized by FTIR and 1H NMR for confirming the structure. The possible copolymer mechanism is given, and we believed that the novel cellulosic Cr(salen)-type complex will be used as an efficient catalyst in other chemical reactions.

Ring‐Opening Copolymerization of Epoxides with Cyclic Anhydrides Promoted by Bimetallic and Monometallic Phenoxy–Imine Aluminum complexes

AbstractTwo dinuclear aluminum alkyl complexes bearing a salen ligand with alkyl backbone of different length between the nitrogen atoms (1,3‐propylene and 1,5‐pentylene backbone) and the related hemisalen aluminum complex were tested as catalysts in the ring‐opening copolymerization of cyclohexene oxide and limonene oxide with succinic anhydride and phthalic anhydride. The effects of different reaction conditions (co‐catalyst and solvent) on the productivity and selectivity of the reactions were evaluated. The comparison of the catalytic behavior of the dinuclear complexes bearing the aluminum reactive centers at different distances as well as of their mononuclear counterpart suggested that the copolymerization follows a monometallic pathway differently from what was observed in the homopolymerization of CHO.

Effect of supercritical CO2 on the copolymerization behavior of cyclohexene oxide/CO2 and copolymer properties with DMC/Salen‐Co(III) catalyst system

ABSTRACTThe copolymerization of cyclohexene oxide (CHO) and carbon dioxide (CO2) was carried out under supercritical CO2 (scCO2) conditions to afford poly (cyclohexene carbonate) (PCHC) in high yield. The scCO2 provided not only the C1 feedstock but also proved to be a very efficient solvent and processing aid for this copolymerization system. Double metal cyanide (DMC) and salen‐Co(III) catalysts were employed, demonstrating excellent CO2/CHO copolymerization with high yield and high selectivity. Surprisingly, our use of scCO2 was found to significantly enhance the copolymerization efficiency and the quality of the final polymer product. Thermally stable and high molecular weight (MW) copolymers were successfully obtained. Optimization led to excellent catalyst yield (656 wt/wt, polymer/catalyst) and selectivity (over 96% toward polycarbonate) that were significantly beyond what could be achieved in conventional solvents. Moreover, detailed thermal analyses demonstrated that the PCHC copolymer produced in scCO2 exhibited higher glass transition temperatures (Tg ∼ 114 °C) compared to polymer formed in dense phase CO2 (Tg ∼ 77 °C), and hence good thermal stability. Additionally, residual catalyst could be removed from the final polymer using scCO2, pointing toward a green method that avoids the use of conventional volatile organic‐based solvents for both synthesis and work‐up. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2785–2793

Group 4 complexes bearing bis(salphen) ligands: Synthesis, characterization, and polymerization studies

ABSTRACTSix different complexes containing bis(salphen) [salphen = N,N'‐phenylenebis(salicylideneimine)] ligands were synthesized and characterized by various spectroscopic techniques and elemental analysis. In the presence of benzyl alcohol as an initiator, all the complexes catalyze the ring‐opening polymerization of lactide and ε‐caprolactone, generating high molecular weight (Mn) polymers in a controlled fashion. The linear relationship between the % conversion and Mn proved the control over the polymerization process. The presence of OBn group as an end group was confirmed by MALDI‐TOF and 1H NMR spectral analysis of low Mn oligomers. The polymerization followed first‐order kinetics as revealed by kinetic experiments. All the complexes were good precatalysts for the polymerization of ethylene. The effect of temperature and time on the yield and activity toward the polymerization of ethylene were widely investigated. In addition, in the presence of tetrabutylammonium bromide as cocatalyst, the formation of degradable polycarbonate with moderate Mn value and narrow molecular weight distributions was observed by the copolymerization of cyclohexene oxide with CO2. The effect of initiator structure, temperature, CO2 pressure, catalyst/cocatalyst loading on the activity, and selectivity toward copolymerization were systematically examined. The thermal properties of the copolymer synthesized were explored using differential scanning calorimetric and thermogravimetric analysis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 809–824

Magnesium complexes of the N, O polydentate scaffold: Synthesis, structural characterization and polymerization studies

A series of magnesium complexes containing the tetradentate di and tri anionic amine phenolate backbone were synthesized from the reaction of suitable ligands and diethyl magnesium. All the complexes were completely characterized by different spectroscopic techniques and single crystal X-ray diffraction studies. The single crystal X-ray structure showed that complexes 1 and 5 are dinuclear and trinuclear respectively. All these complexes (1–8) were found to be active towards the bulk the ring opening polymerization (ROP) of lactides in the presence or absence of benzyl alcohol, at 140 °C and it was found that the polymerizations were better controlled in the presence of benzyl alcohol. The kinetics and mechanistic studies associated with these polymerizations have been performed. The complexes have been shown to be highly active toward the copolymerization of cyclohexene oxide (CHO) and propylene oxide (PO) with carbon dioxide. The introduction of a bulky ortho substituent on the phenoxy units of the ligand decreases the catalytic activity of the corresponding magnesium complexes.

A MALDI-TOF MS analysis study of the binding of 4-(N,N-dimethylamino)pyridine to amine-bis(phenolate) chromium(III) chloride complexes: mechanistic insight into differences in catalytic activity for CO2/epoxide copolymerization.

Amine-bis(phenolato)chromium(III) chloride complexes, [LCrCl], are capable of catalyzing the copolymerization of cyclohexene oxide with carbon dioxide to give poly(cyclohexane) carbonate. When combined with 4-(N,N-dimethylamino)pyridine (DMAP) these catalyst systems yield low molecular weight polymers with moderately narrow polydispersities. The coordination chemistry of DMAP with five amine-bis(phenolato)chromium(III) chloride complexes was studied by matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The amine-bis(phenolato) ligands were varied in the nature of their neutral pendant donor-group and include oxygen-containing tetrahydrofurfuryl and methoxyethyl moieties, or nitrogen-containing N,N-dimethylaminoethyl or 2-pyridyl moieties. The relative abundance of mono and bis(DMAP) adducts, as well as DMAP-free ions is compared under various DMAP : Cr complex ratios. The [LCr](+) cations show the ability to bind two DMAP molecules to form six-coordinate complex ions in all cases, except when the pendant group is N,N-dimethylaminoethyl (compound ). Even in the presence of a 4 : 1 ratio of DMAP to Cr, no ions corresponding to [L3Cr(DMAP)2](+) were observed for the complex containing the tertiary sp(3)-hybridized amino donor in the pendant arm. The difference in DMAP-binding ability of these compounds results in differences in catalytic activity for alternating copolymerization of CO2 and cyclohexene oxide. Kinetic investigations by infrared spectroscopy of compounds 2 and 3 show that polycarbonate formation by 3 is twice as fast as that of compound 2 and that no initiation time is observed.

Novel coating resins based on polycarbonates and poly(ester-co-carbonate)s made by catalytic chain growth polymerization of epoxides with CO2 and with anhydride/CO2

In this work we describe a possibly new generation of (powder) coating resins of the polycarbonate or poly(ester-co-carbonate) type, synthesized from epoxides like cyclohexene oxide (CHO), anhydrides like phthalic anhydride (PA) and carbon dioxide (CO2) by chain growth polymerization, catalyzed by a chromium-Salophen complex and using dimethylaminopyridine (DMAP) as a co-catalyst. The molecular structures of the polymers produced were characterized and especially MALDI-ToF-MS yielded important information on the end-groups and other functional groups which are crucial for the curing chemistry of these resins. One special type of copolycarbonate in this study carried pendent vinyl groups, introduced by copolymerization of CHO and CO2 with 4-vinylcyclohexene oxide (VCHO). This copolycarbonate was first casted from solution, after which the polymer film was successfully cured with a trithiol compound by UV- or thermally induced radical curing chemistry. These cured coatings showed a good acetone resistance (≥75 double rubs) and reversed impact toughness. A powder coating evaluation of this CHO/VCHO-based copolycarbonate showed excellent processability, high pencil hardness (6-8H), value zero in a Gitterschnitt test on aluminum, reasonable appearance in a ‘PCI-smoothness test’ (value 2–3) and good acetone resistance (≥75 double rubs). Most probably due to a too high Tg (85–104°C) of the cured coating the reverse impact resistance was poor. A similar powder coating evaluation of a poly(ester-co-carbonate) based on CHO, PA and CO2 showed less promising results due to poor flow properties and foaming above 140°C.

Hydrido and Allyl/Hydrido Complexes of Early Lanthanides Supported by an NNNN‐Type Macrocyclic Ligand

AbstractHydrogenation of the neutral bis(allyl) complexes of the early lanthanides [Ln(Me3TACD)(η3‐C3H5)2] [(Me3TACD)H = 1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane, Me3[12]aneN4] with phenylsilane gave the tetranuclear octahydrido complexes [Ln(Me3TACD)(μ‐H)2]4 [Ln = Ce (1‐Ce), Pr (2‐Pr)] or the dinuclear allyl/hydrido complexes [Ln(Me3TACD)(η3‐C3H5)(μ‐H)]2 [Ln = Nd (3‐Nd), Sm (4‐Sm)], which were isolated and characterized. The structures of 1‐Ce and 2‐Pr are constructed of a tetrahedral Ln4H8 core. Single‐crystal X‐ray diffraction analyses of 3‐Nd and 4‐Sm revealed a C2 symmetric planar Ln2H2 core. The experimental structures agreed with the results of DFT calculations, which predict that the nuclearity of the dihydrido complexes depend on the ionic radius of the metal. Compounds 1‐Ce, 2‐Pr, 3‐Nd and 4‐Sm were tested as catalysts in the copolymerization of cyclohexene oxide with CO2 to give highly carbonate‐linked copolymers with moderate activities.