Copolymerization Of Carbon Dioxide Research Articles

Plasticizing while toughening and reinforcing poly(propylene carbonate) using low molecular weight urethane: Role of hydrogen-bonding interaction

Poly(propylene carbonate) (PPC), a biodegradable plastic produced by alternating copolymerization of carbon dioxide and propylene oxide, is amorphous at glass-transition temperature of ∼35 °C; therefore, it becomes brittle at temperatures <20 °C. This article reports on the synthesis of low molecular weight urethanes, such as 1,6-bis(hydroxyethyl urethane)hexane (BEU), 1,6-bis(hydroxyisopropyl urethane)hexane (BPU), and 1,6-bis(methyl urethane)hexane (HDU) bearing rich NH and CO bonds, by a non-isocyannate method and their use as plasticizers for PPC. The hydrogen-bonding interaction between BPU and PPC was found to be significantly more effective as compared with BEU and HDU, and the highest hydrogen-bonding interaction fraction reached 5.2% in a PPC/BPU blend with 15 wt% BPU loading. Solubility parameters calculated from Hoy’s method, in combination with differential scanning calorimetric analysis, indicated that HDU and BPU were miscible with PPC at a molecular scale, while BEU was immiscible with PPC. Usually, plasticizing is generally accompanied by sacrificing of tensile strength; however, it was encouraging to observe that the elongation at break for PPC/HDU blend with 10 wt% of HDU loading reached 727% – an increase 53 times that of pure PPC – while the tensile strength was maintained at 30 MPa, which was comparable with that of linear low-density polyethylene. The hydrogen-bonding interaction generated a remarkable improvement in the mechanical performance of PPC; it not only confined the migration of the plasticizer to the surface and thus ensured stability of the blending material over time, but it also maintained the mechanical strength of the plasticized PPC.

Copolymerization of carbon dioxide and propylene oxide under inorganic oxide supported rare earth ternary catalyst

AbstractRecently, rare earth ternary coordination catalyst represented as Y(CCl3OO)3‐Glycerin‐ZnEt2 has been used for producing poly(propylene carbonate) (PPC, an alternating copolymer of carbon dioxide and propylene oxide) in industry scale, but its catalytic activity needs further improvement. One reason for the relatively low catalytic activity lied in that only 11.7% of active center was efficient due to possible embedding of active center in the heterogeneous catalyst. In this report, supporting strategy was developed, where Y(CCl3OO)3‐Glycerin‐ZnEt2 was supported on various inorganic oxides. Two supporting methods were carried out. One way was to mix Y(CCl3OO)3‐Glycerin with inorganic oxide first and then ZnEt2 was dropped to form the supported catalyst, and the other was to make Y(CCl3OO)3‐Glycerin‐ZnEt2 at first and then mixing with inorganic oxides. The former showed decreasing catalytic activity compared with corresponding unsupported rare earth ternary catalyst, while an improvement of 16–36% in catalytic activity was realized in the latter. PPC with an average number molecular weight (Mn) of over 100 kg/mol and carbonate unit (CU) content of higher than 96% was prepared by both supported catalysts. The catalytic activity of the supported catalyst depended significantly on the supports, which increased in the following order: α‐Al2O3 &lt; MgO &lt; ZnO ≈ SiO2 &lt;γ‐Al2O3. γ‐Al2O3 was the best support for rare earth ternary catalyst, which showed a remarkable 36% increase in catalytic activity, corresponding to the utilization of 17% of active center. Although MgO supported catalyst gave only an 8% increase in catalytic activity, the Mn and CU content of PPC were raised to about 143 kg/mol and 99%, whereas the PPC from common rare earth ternary catalyst was about 108 kg/mol and 97%, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Synthesis of biodegradable polycarbonate by alternating copolymerization of carbon dioxide and propylene oxide using a cobalt/Schiff base catalyst

A series of cobalt/Schiff base complexes, ( R, R)-SalenCo IIIX [Salen = N, N′-bis(3,5-di-tert-butylsalicylidene)-1,2-di-phenylethylenediimine; X = OOCCF 3 ( 1), OOCCCl 3 ( 2), and OOCCH 3 ( 3)], were investigated for the alternating copolymerization of carbon dioxide with racemic propylene oxide in the presence of [PPN]Cl ([PPN] = bis(triphenylphosphine)iminium). The effect of the axial group X of the complexes and the reaction conditions on the yield, the selectivity for poly(propylene carbonate) over propylene carbonate, and the polymer molecular weight for this transformation were investigated. A high molecular weight of 72.5 kg mol −1 (Mn/Mw = 1.27, yield 76%) for the copolymer was achieved.

Highly Active Di- and Trimetallic Cobalt Catalysts for the Copolymerization of CHO and CO2 at Atmospheric Pressure

The synthesis and characterization of three new cobalt catalysts for the copolymerization of carbon dioxide and cyclohexene oxide are reported. All the complexes are extremely active at just 1 atm pressure of carbon dioxide, with very high selectivity for copolymerization and carbonate formation. The catalysts are dicobalt(II/II and II/III) and tricobalt(II/II/II) complexes coordinated by a macrocyclic, reduced “Robson” type ancillary ligand and by acetate groups. The complexes are significantly more active than their direct zinc analogues, which we attribute to the increased nucleophilicity of the cobalt−oxygen bond in the cobalt−carbonate propagating species. All three complexes are characterized using mass spectrometry, infrared and ultraviolet−visible spectroscopies, elemental analysis, and, for the tricobalt complex and mixed valence dicobalt species, single-crystal X-ray crystallography.

Alternating copolymerization of carbon dioxide and propylene oxide under bifunctional cobalt salen complexes: Role of Lewis base substituent covalent bonded on salen ligand

Alternating copolymerization of propylene oxide (PO) and carbon dioxide (CO2) was realized under mild conditions with a moderate turnover frequency (TOF), employing sole bifunctional cobalt salen complexes containing Lewis acid metal center and covalent bonded Lewis base on the ligand. Variation of the covalent bonded Lewis base substituents on the salen ligands could tailor the catalytic activity with TOF changing from 19.3 to 34.9 h−1, polymeric/cyclic carbonate selectivity from 95.3 to 72.8%, and the head-to-tail structure in the polymer from 72.2 to 86.0%. The IR analysis confirmed that the Lewis base moiety on one molecule could coordinate with cobalt center of adjacent molecule, playing similar role to the Salen metal complex/Lewis base binary catalytic system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 359–365, 2010

Alternating copolymerization of carbon dioxide and propylene oxide by single-component cobalt salen complexes with various axial group

Abstract A series of single-component cobalt salen complexes, N,N′-bis(salicylidene)-1,2phenylenediamino cobaltIII X (X = Cl (1a), Br (1b), NO3 (1c), CF3COO (1d), BF4 (1e), and N3 (1f)) (SalphCoX), were prepared for alternating copolymerization of carbon dioxide and propylene oxide(PO) under mild condition. The axial anion X group of the SalenphCoX played important role in tailoring the catalytic activity, polymeric/cyclic carbonate selectivity, as well as stereochemistry of carbonate unit sequence in the polymer chain. SalenphCoX with an electron-withdrawing axial X group (complex 1c) was an ideal catalyst for the copolymerization of CO2 and PO to selectively produce polycarbonate with ∼99% carbonate linkage and over 81% head-to-tail structure.

Alternating Copolymerization of Carbon Dioxide and Propylene Oxide Catalyzed by Cobalt Schiff Base Complex

AbstractCobalt 2,4‐dinitrophenolate (complex 1) based upon a N,N,O,O‐tetradentate Schiff base ligand framework was prepared. X‐ray diffraction analysis confirmed that complex 1 was triclinic species with a six‐coordinated central cobalt octahedron in the solid. Asymmetric alternating copolymerization of carbon dioxide (CO2) with racemic propylene oxide (rac‐PO) proceeded effectively by complex 1 in conjunction with (4‐dimethylamino)pyridine (DMAP), yielding a perfectly alternating and bimodal molecular weight distribution PO/CO2 poly(propylene carbonate) (PPC) with a small amount of cyclic carbonate byproducts.magnified image

Highly Active Dizinc Catalyst for the Copolymerization of Carbon Dioxide and Cyclohexene Oxide at One Atmosphere Pressure

Zink statt Druck: Der neuartige Dizinkkomplex 1 eines makrocyclischen Liganden vermittelt die Copolymerisation von Kohlendioxid und Cyclohexenoxid mit erstaunlicher Aktivität – selbst wenn der CO2-Druck nur 1 atm beträgt. (TON und TOF sind die Umsatzzahl bzw. -frequenz.) Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Highly Active Dizinc Catalyst for the Copolymerization of Carbon Dioxide and Cyclohexene Oxide at One Atmosphere Pressure

Low-pressure catalyst: A novel dizinc complex (1) having a macrocyclic ancillary ligand shows remarkable activity for the copolymerization of carbon dioxide and cyclohexene oxide, at only one atmosphere of CO2. TON=turnover number; TOF=turnover frequency. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Carbon dioxide/propylene oxide coupling reaction catalyzed by chromium salen complexes

A series of chromium/Schiff base complexes N,N′-bis(salicylidene)-1,2-phenylenediamino chromiumIII X were prepared and employed for the alternating copolymerization of carbon dioxide with racemic propylene oxide in the presence of (4-dimethylamino)pyridine. The effect of the complex structure and reaction conditions on the catalytic activity, the poly(propylene carbonate)/cyclic carbonate (PPC/PC) selectivity, and the polymer head-to-tail linkages was examined. The experiments indicated that N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-phenylenediamino chromiumIII (NO3) exhibited the highest PPC/PC selectivity as well as polymer head-to-tail linkages and N,N′-bis(3,5-dichlorosalicylidene)-1,2-phenylenediimino chromiumIII (NO3) possessed the highest catalytic activity among these chromium/Schiff base complexes. The structure of the produced copolymer was characterized by the IR, 1H NMR, and 13C NMR measurements. Almost 100% carbonate content of the resulting polycarbonate were obtained with the help of these effective catalyst systems under facile conditions.

Mechanistic Insight into the Initiation Step of the Coupling Reaction of Oxetane or Epoxides and CO2 Catalyzed by (salen)CrX Complexes

The most active and robust current catalysts for the copolymerization of carbon dioxide and epoxides or oxetanes, (salen)CrX in conjunction with PPNX (PPN(+) = (Ph3P)2N(+)) or n-Bu4NX (X = Cl, N3, CN, NCO), are characterized both in solution by infrared spectroscopy and in the solid-state by X-ray crystallography. All anions (X) afford six-coordinate chromium(III) PPN(+) or n-Bu4N(+) salts composed of trans-(salen)CrX2(-) species. Of the X groups investigated in (salen)CrX, chloride is easily displaced by the others, that is, the reaction of (salen)CrCl with 2 equiv of N3(-), CN(-), or NCO(-) quantitatively provide (salen)Cr(N3)2(-), (salen)Cr(CN)2(-), and (salen)Cr(NCO)2(-), respectively. On the other hand, addition of less than 2 equiv of azide to (salen)CrCl leads to a Schlenk (ligand redistribution) equilibrium of the three possible anions both in solution and in the solid-state as shown by X-ray crystallography and electrospray ionization mass spectrometry. It was further demonstrated that all trans-(salen)CrX2(-) anions react with the epoxide or oxetane monomers in TCE (tetrachloroethane) solution to afford an equilibrium mixture containing (salen)CrX x monomer, with the oxetane adduct being thermodynamically more favored. The ring-opening steps of the bound cyclic ether monomers by X(-) were examined, revealing the rate of ring-opening of the epoxides (cyclohexene oxide and propylene oxide) to be much faster than of oxetane, with propylene oxide faster than cyclohexene oxide. Furthermore, both X anions in (salen)CrX2(-) were shown to be directly involved in monomer ring-opening.

The copolymerization of carbon dioxide and propylene oxide with Y(CCl3COO)3-diphenylzinc-glycerol catalyst

Various organometallic compounds (diphenylzinc, dibenzylzinc, dicyclohexylzinc, bis(pentafluorophenyl)zinc, diethylzinc, di(n-butyl)zinc, triethylaluminum) were used to form Y(CCl3COO)3-organometallic compound-glycerol catalyst for the copolymerization of carbon dioxide and propylene oxide. It was found that Y(CCl3COO)3-diphenylzinc-glycerol catalyst showed the highest catalytic activity, at optimum conditions the yield could be as high as 478.8 (g polymer/mol Zn h). The catalytic activity sequence of these catalysts decreased as follows: Y(CCl3COO)3-diphenylzinc-glycerol>Y(CCl3COO)3-diethylzinc-glycerol>Y(CCl3COO)3-di-(n-butyl)zinc-glycerol>Y(CCl3COO)3-dibenzylzinc-glycerol>Y(CCl3COO)3-dicyclohexylzinc-glycerol>Y(CCl3COO)3-bis(pentafluorophenyl)zinc-glycerol. 1H NMR, 13C NMR, TGA, DMA, tensile tests results indicated that microstructure and properties of the polymers varied with catalyst used. Copolymer from Y(CCl3COO)3-diphenylzinc-glycerol catalyst displayed the highest thermal properties and mechanical properties: the glass transition temperature (Tg) was 50.2 oC, the 5% weight loss temperature (T-5%) was 222 C, the tensile strength was 34.7 MPa, the Young’s modulus was 298 MPa. The difference between the properties of the polymers was explained relating to the different polycarbonate content in the polymers.

Biological affinity and biodegradability of poly(propylene carbonate) prepared from copolymerization of carbon dioxide with propylene oxide

In this study we investigated bacterial and cell adhesion to poly(propylene carbonate) (PPC) films, that had been synthesized by the copolymerization of carbon dioxide (a global warming chemical) with propylene oxide. We also assessed the biocompatibility and biodegradability of the filmsin vivo, and their oxidative degradation in vitro. The bacteria adhered to the smooth, hydrophobic PPC surface after 4 h incubation.Pseudomonas aeruginosa andEnterococcus faecalis had the highest levels of adhesion,Escherichia coli andStaphylococcus aureus had the lowest levels, andStaphylococcus epidermidis was intermediate. In contrast, there was no adhesion of human cells (cell line HEp-2) to the PPC films, due to the hydrophobicity and dimensional instability of the surface. On the other hand, the PPC films exhibited good biocompatibility in the mouse subcutaneous environment. Moreover, contrary to expectation the PPC films degraded in the mouse subcutaneous environment. This is the first experimental confirmation that PPC can undergo surface erosion biodegradationin vivo. The observed biodegradability of PPC may have resulted from enzymatic hydrolysis and oxidative degradation processes. In contrast, the PPC films showed resistance to oxidative degradationin vitro. Overall, PPC revealed high affinity to bioorganisms and also good biodegradability.

Regio‐regular structure high molecular weight poly(propylene carbonate) by rare earth ternary catalyst and Lewis base cocatalyst

AbstractLewis base modification strategy on rare earth ternary catalyst was disclosed to enhance nucleophilic ability of active center during copolymerization of carbon dioxide and propylene oxide (PO), poly(propylene carbonate) (PPC) with H‐T linkages over 83%, and number–average molecular weight (Mn) up to 100 kg/mol was synthesized at room temperature using Y(CCl3OO)3‐ZnEt2‐glycerine catalyst and 1,10‐phenanthroline (PHEN) cocatalyst. Coordination of PHEN with active Zinc center enhanced the nucleophilic ability of the metal carbonate, which became more regio‐specific in attacking carbon in PO, leading to PPC with improved H‐T linkages. Moreover, the binding of PHEN to active Zinc center also raised the carbonate content of PPC to over 99%, whereas the PPC from common rare earth ternary catalyst was about 96%. Unlike the highly regio‐regular structure PPC but with relatively low molecular weight recently reported in the literature, our high molecular weight regio‐regular PPC did show significant improvement in thermal and mechanical performances. PPC with H‐T linkages up to 83.2% showed glass transition temperature (Tg) of 43.3 °C, while Tg of PPC with H‐T linkages of 69.7% was only 36.1 °C. When H‐T connectivity was raised from 69.7 to 83.2%, the modulus of PPC showed a 78% increase. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4451–4458, 2008

Alternating copolymerization of carbon dioxide and cyclohexene oxide catalyzed by silicon dioxide/ZnCoIII double metal cyanide complex hybrid catalysts with a nanolamellar structure

AbstractAir‐stable hybrid catalysts of silicon dioxide/double metal cyanide complexes (Si‐DMCCs) based on Zn3[Co(CN)6]2 (ZHCC) were prepared by an in situ sol–gel method. The Si‐DMCCs showed low crystallinity and a nanolamellar structure with a thickness of ∼40–60 nm. In particular, a lamellar structure of regular hexagonal shape was observed for Si‐DMCCs with low SiO2 content. These catalysts had very high catalytic activity for alternating copolymerization of cyclohexene oxide (CHO) and carbon dioxide. A turnover number of 11,444, turnover frequency of 3815 h−1, and apparent efficiency of 7.5 kg polymer/g ZHCC (∼24.0 kg polymer/g Zn) were achieved at 3.8 MPa and 100 °C. The poly(cyclohexenylene carbonate) (PCHC) polymers obtained were completely atactic with a molecular weight (Mn) of ∼10 kg/mol and polydispersity of 2.0–3.0. The PCHCs had a structure of nearly alternating CHO and CO2 units, with a molar fraction of carbonate units of 0.44–0.47. Preliminary investigations of the mechanism suggest that nucleophilic attack by neighboring oxygen atoms is involved in copolymerization initiation with ZnCoIII DMCCs. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3128–3139, 2008

X-Ray crystal structures of five-coordinate (salen)MnN3 derivatives and their binding abilities towards epoxides: chemistry relevant to the epoxide–CO2 copolymerization process

The synthesis of several (salen)MnN3 complexes in good yields and purities were achieved by the reaction of manganese(III) acetate and H2salen, followed by metathesis of the remaining acetate ligand with an aqueous solution of NaN3. The X-ray structures of two derivatives, where salen=N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylenediamine and N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexenediamine respectively, were determined. The complexes were shown to be monomeric 5-coordinate derivatives displaying a distorted square pyramidal geometry, and to be d4 high-spin derivatives by solution magnetic moment measurements using the Evans method. Binding studies of the (salen)MnN3 derivatives with added azide ions or cyclohexene oxide showed these complexes to have modest affinities for binding a sixth ligand. These observations are used to rationalize the low activity exhibited by manganese(III) complexes relative to their chromium(III) and cobalt(III) analogs for serving as catalysts for the copolymerization of carbon dioxide and epoxides.

Copolymerization of carbon dioxide and epoxides with a novel effective Zn–Ni double‐metal cyanide complex

AbstractA novel double‐metal cyanide complex based on Zn[Ni(CN)4] was prepared and used as a catalyst for the copolymerizations of carbon dioxide and propylene oxide (PO) and carbon dioxide and cyclohexene oxide (CHO). The copolymers were characterized by IR and 1H‐NMR, and the effects of temperature, pressure, solvent, and preparative methods for the catalysts on catalytic activity and composition of the copolymer were investigated. The results show that this novel catalyst exhibited its highest catalytic efficiency at about 500 g/g of Zn[Ni(CN)4] for PO and CO2, whereas the catalytic efficiency for CHO and CO2 was merely between 5.6 and 22.5 g/g of Zn[Ni(CN)4]. The molar fraction of carbonate linkages for PO–CO2 and CHO–CO2 copolymers reached about 0.6 and 0.3, respectively. The results show that a lower temperature and a higher CO2 pressure were favorable for the incorporation of CO2 into the copolymer, and the nonpolar solvents were better media for copolymerization. As a complexing agent, glycol ether exhibited better promoting effects on catalytic efficiency among those investigated, but the catalysts prepared by different complexing agents showed no significant differences in the compositions of the copolymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Alternating copolymerization of carbon dioxide and propylene oxide catalyzed by (R, R)‐SalenCoIII‐ (2,4‐dinitrophenoxy) and Lewis‐basic cocatalyst

AbstractA binary catalyst system of a chiral (R,R)‐SalenCoIII(2,4‐dinitrophenoxy) (salen = N,N‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐diphenylethylenediimine) in conjunction with (4‐dimethylamino)pyridine (DMAP) was developed to generate the copolymerization of carbon dioxide (CO2) and racemic propylene oxide (rac‐PO). The influence of the molar ratio of catalyst components, the operating temperature, and reaction pressure on the yield as well as the molecular weight of polycarbonate were systematically investigated. High yield of turnover frequency (TOF) 501.2 h−1 and high molecular weight of 70,400 were achieved at an appropriate combination of all variables. The structures of as‐prepared products were characterized by the IR, 1H NMR, 13C NMR measurements. The linear carbonate linkage, highly regionselectivity and almost 100% carbonate content of the resulting polycarbonate were obtained with the help of these effective catalyst systems under facile conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5050–5056, 2007

Silica-Grafted Diethylzinc and a Silsesquioxane-Based Zinc Alkyl Complex as Catalysts for the Alternating Oxirane−Carbon Dioxide Copolymerization

A novel zinc silsesquioxane complex ([(c-C5H9)7Si7O11(OSiMePh2)]2Zn4Me4 (1)) has been used as a model compound for silica-grafted zinc catalysts in the copolymerization of cyclohexene oxide and CO2. Complex 1 exists as a dimer in the solid state and is moderately active in the copolymerization, and polycyclohexene carbonates have been obtained with a carbonate content of 79−98%. Polymerizations with ZnEt2-treated silica particles resulted in polymer particles with Mn and Mw values and carbonate contents comparable to those of the polymers obtained with 1. It was further demonstrated that CO2 consumption can be followed online by monitoring the decrease of system pressure during the reaction. CO2 consumption has been interpreted in relation to both polycarbonate and cyclic carbonate formation. These measurements represent the intrinsic kinetics of this reaction, which appear to be directly related to CO2 pressure.

Alternating copolymerization of carbon dioxide and epoxide by dinuclear zinc Schiff base complex

The successful alternating copolymerization of carbon dioxide and cyclohexene oxide was achieved by using a dinuclear zinc Schiff base complex, without forming cyclic carbonate. A remarkable effect of Lewis basic additives on the yield and selectivity of the product was demonstrated. Among the examined Lewis bases, 1,4-dioxane was the best additive, where the copolymerization with the dinuclear zinc Schiff base complex – 1,4-dioxane system produced selectively the perfectly alternating copolymer in high yield.