Terpolymerization of Carbon Dioxide with Propylene Oxide and ε-Caprolactone: Synthesis, Characterization and Biodegradability

Summary An aliphatic polycarbonate, terpolymer of carbon dioxide, propylene oxide and ε-caprolactone(PPC-CL-PPO-CL),was synthesized by using a polymer supported bimetallic complex as a catalyst.The terpolymers prepared were characterized by FTIR, ¹H NMR, ¹³C NMR, DSC and WAXD measurements. The influences of various reaction conditions such as molar ratio of the monomers, reaction time and reaction temperature on the terpolymerization progress were investigated. The results showed that ε-caprolactone (ε-CL) was inserted into the backbone of poly(propylene carbonate)-poly(propylene oxide) (PPC-PPO) successfully. The viscosity and glass transition temperature of the terpolymers were much higher than PPC-PPO. ε-Caprolactone offered an ester structural unit that gave the terpolymers remarkable degradability. And the degradation rate of the backbone increased with the ε-CL inserted into the terpolymers.     

Synthesis of poly(propylene-<Emphasis Type="Italic">co</Emphasis>-lactide carbonate) and hydrolysis of the terpolymer

A new aliphatic polycarbonate, terpolymer of carbon dioxide, propylene oxide, and dl-lactide, was synthesized by using a polymer-supported bimetallic complex as a catalyst. The terpolymer prepared was characterized by FT-IR, ¹H NMR, ¹³C NMR, ¹H–¹H COSY, DSC, and WAXD measurements. The influence of molar ratio on the terpolymerization progress was investigated. The results showed that lactide unit was inserted into the backbone of CO₂–PO successfully. Because of the existence of the lactide ester unit, the terpolymers had stronger degradability than poly(propylene carbonate).     

Synthesis and properties of aliphatic polycarbonates derived from carbon dioxide,propylene oxide and maleic anhydride

Terpolymerization of carbon dioxide (CO₂) with propylene oxide (PO) and maleic anhydride (MA) was successfully carried out using supported zinc glutarate catalyst. Consequently giving high molecular weight poly(propylene carbonate maleate) (PPCMA) in a very high yield (72.5 g polymer/g catalyst). The resulting terpolymers were fully characterized by FTIR, ¹H NMR, ¹³C NMR, and wide‐angle X‐ray diffraction (WAXD) techniques. NMR measurements showed that PPCMA had an almost alternating structure for the components of carbon dioxide and PO. The influence of molecular weight and MA content on the properties of PPCMA was also investigated. Differential scanning calorimetry (DSC) measurements revealed that the glass transition temperature (T_g) of PPCMA increased with increasing molecular weight. Thermogravimetric analysis (TGA) indicated that PPCMA51 exhibited a very high decomposition temperature (263°C) due to the introduction of the double bond of MA into the backbone of terpolymer. The terpolymers with double bonds can be readily subjected to crosslinking reaction in high temperature to give a slightly crosslinked PPCMA, which exhibit superior thermal stability. Tensile tests also showed that the mechanical properties of PPCMA increased with increasing molecular weight. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

New findings in the catalytic activity of zinc glutarate and its application in the chemical fixation of CO2 into polycarbonates and their derivatives

A heterogeneous zinc glutarate (ZnGA) catalyst and its derivatives were prepared from various zinc and glutarate sources. The hydrothermal reaction between zinc perchlorate hexahydrate and glutaronitrile afforded ZnGA single crystals (sc-ZnGA), with a monoclinic lattice unit cell and a P2/c space group, as determined by X-ray single-crystal structural analysis. The structural details of the ZnGA catalyst are crucial in helping to elucidate its activity in the copolymerization reactions between carbon dioxide (CO₂) and alkylene oxides. X-ray absorption studies provided direct evidence that CO₂ and propylene oxide (PO) are reversibly adsorbed onto the Zn ion centers on the ZnGA surface. Compared to CO₂, PO was found to insert more easily into the Zn–O bond of the ZnGA catalyst, suggesting that the ZnGA-catalyzed copolymerization is initiated by PO rather than CO₂. The activity of the ZnGA catalyst in the copolymerization of CO₂ and PO was found to depend on the zinc source used, and its ability to produce a catalyst of large surface area and high crystallinity (≥77%). Modification of the glutarate ligand with electron-donating or withdrawing substituents failed to enhance the ZnGA catalyst activity further, indicating that glutarate is the best ligand for the Zn metal ion to achieve a high catalytic activity in the CO₂ copolymerization with PO. The ZnGA-catalyzed copolymerization was further optimized to maximize the yield of alternating poly(propylene carbonate), and also extended to the terpolymerization of CO₂ and PO with δ-valerolactone (VL). Terpolymers with high molecular weights and yields could be obtained by adjusting the PO/VL feed ratios. In addition, the terpolymers were found to exhibit excellent enzymatic and biological degradability.     

Thermally stable poly(propylene carbonate) synthesized by copolymerizing with bulky naphthalene containing monomer

To enhance the thermal and mechanical properties of poly(propylene carbonate) (PPC), the terpolymers were synthesized from carbon dioxide, propylene oxide, and a third monomer, [(2‐naphthyloxy)methyl]oxirane (NMO) using supported zinc glutarate as catalyst. The structure of these terpolymers was confirmed by ¹H NMR spectroscopy. The catalytic activity, molecular weight, carbonate unit content, as well as thermal and mechanical properties were investigated extensively. The experimental results showed that the catalytic activity, molecular weight, and carbonate unit content decreased with the incorporation of NMO. DSC measurements indicated that the introduction of NMO increased the glass transition temperature from 38 to 42°C. TGA tests revealed that the thermal decomposition temperature (T_g?5%) of the synthesized terpolymer increased significantly, being 34°C higher than that of pure PPC. Accordingly, the mechanical properties proved also to be enhanced greatly as evidenced by tensile tests. These thermal and mechanical improvements are of importance for the practical process and application of PPC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Sustainable and biodegradable poly(butylene succinate-co-terephthalate)/poly(propylene carbonate) blown films with enhanced compatibility,mechanical, and barrier properties

In this study, a novel environment-friendly PBST/PPC-based blown film was prepared using maleic anhydride (MA) as a reactive compatibilizer to enhance the compatibility between poly(butylene succinate-co-terephthalate) (PBST) and poly(propylene carbonate) (PPC). Results of rheological testing and gel permeation chromatography (GPC) indicated that MA reacted with PBST/PPC during melt-blending extrusion. Morphological analysis of the cryo-fractured surfaces of PBST/PPC blend showed significantly improved compatibility between PBST and PPC with the addition of MA. Moreover, the Young's modulus, tensile strength, breaking strain, and tear strength of PBST/PPC/MA blown films increased with an increase in MA content. In comparison to PBST/MA blown film without PPC, the barrier property of PBST/PPC/MA blown films was improved. In addition, in vitro cell experiments showed that the PBST/PPC/MA blown film was suitable for the growth of mouse fibroblast (L929) cells. In vitro ecotoxicity testing on mung bean plant showed that the extracts from the PBST/PPC/MA blown film had no negative effects on the development of mung bean plant. Furthermore, degradability testing in soil also proved that the PBST/PPC/MA blown film had good biodegradability. Thus, the PBST/PPC/MA blown film can be used in fields, such as food packaging and agricultural mulch film.     

Thermally stable aliphatic polycarbonate containing bulky carbazole pendants

To improve the thermal and mechanical properties of poly(propylene carbonate) (PPC), the terpolymers were synthesized by the terpolymerization of CO₂ with PO and a third monomer, N-(2,3-epoxylpropyl)carbazole (NEC) using supported zinc glutarate as catalyst. The catalytic activity, molecular weight, carbonate unit content, as well as the thermal and mechanical properties were investigated extensively. The experimental results showed that the catalytic activity, molecular weight, and carbonate unit content decreased with the incorporation of NEC. The introduction of NEC increased the glass transition temperature from 38.0 to 44.1°C. Moreover, the thermal decomposition temperature (T_g-5%) of the terpolymer (278°C) was much higher than that of pure PPC (238°C). Accordingly, the mechanical properties proved to be enhanced greatly as evidenced by tensile tests due to the incorporation of bulky carbazole moieties. These improvements in thermal and mechanical properties are of very importance for the process of PPC. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

One‐pot regioselective and stereoselective terpolymerization of rac‐lactide,CO2 and rac‐propylene oxide with TPPMCl (M = Cr,Co, Al)/PPNCl binary catalyst

Tetraphenyl porphyrin metal compound (TPPMCl) (where the TPPMCl was TPPCrCl, TPPCoCl, TPPAlCl), in combination with cocatalyst PPNCl (bis(triphenylphosphine)iminium chloride, the molar ratio of TPPMCl to PPNCl was 1:0.5), was used to catalyze the polymerization of racemic lactide (rac‐LA) in racemic propylene oxide (rac‐PO) medium and the terpolymerization of rac‐LA, CO₂ and rac‐PO. It was found that these TPPMCl/PPNCl binary catalysts could initiate the stereoselective polymerization of rac‐LA in rac‐PO medium to form enriched isotactic polylactide (PLA) (P_i ≥ 68.0%) and terpolymerization of CO₂, rac‐LA, rac‐PO to form PPC‐PLA‐PPO (PPC, poly(propylene carbonate); PPO, poly(propylene oxide)) multiblock copolymer. In particular the PPC‐PLA‐PPO multiblock copolymer thus formed displayed high regioregularity and stereoregularity, and has high head‐to‐tail structure content in the PPC block (H‐T% ≥ 63.6%) and high isotacticity in the PLA block (P_i ≥ 64.0%). The influence of catalyst formula, the monomer feeding ratio, reaction temperature, carbon dioxide pressure and reaction time on the terpolymerization was investigated by ¹H NMR, ¹³C NMR, gel permeation chromatography, DSC and TGA. © 2018 Society of Chemical Industry     

Catalytic synthesis and characterization of an alternating copolymer from carbon dioxide and propylene oxide using zinc pimelate

New zinc pimelate catalysts used for copolymerization of carbon dioxide and propylene oxide have been synthesized in high yield by a magnetic stirring method. The regular molecular structure of the zinc pimelate was confirmed by Fourier‐transform infrared spectroscopy and wide‐angle X‐ray diffraction techniques. Accordingly, poly(propylene carbonate) (PPC) can be synthesized from carbon dioxide and propylene oxide using these zinc pimelate catalysts. High catalytic efficiency (95.2 gram polymer per gram catalyst or 21 300 g of polymer per mole of zinc) was achieved by optimizing the PO/catalyst ratio. NMR measurement revealed that the PPC synthesized had an alternating copolymer structure. The thermal properties of PPC were determined by modulated differential scanning calorimetry and thermogravimetric analysis. The results demonstrated that the PPC copolymer exhibited an extremely high glass transition temperature of 44.27 °C and decomposition temperature of 257 °C, comparable with values reported in literature. Copyright © 2003 Society of Chemical Industry     

Acid- and base-catalyzed hydrolyses of aliphatic polycarbonates and polyesters

Poly(propylene carbonate) (PPC) was synthesized by the zinc glutarate catalyzed copolymerization of carbon dioxide and propylene oxide (PO). Hydrolytic degradability of the PPC polymer was examined in tetrahydrofuran solutions containing 10 wt.% acidic or basic aqueous solutions of varying pH using viscometry and GPC analysis. Further, the hydrolysis behaviors of all PPC solutions were compared with those of poly(-caprolactone) (PCL) and poly(d,l-lactic acid) (PLA). All polymers studied show higher degradability in strong basic conditions than in strong acidic conditions, but very low degradability in moderate acidic, basic and neutral conditions. Moreover, PPC is degraded less in strong acidic conditions than the polyesters, while in strong basic conditions, the polycarbonate is more easily degraded. The difference in degradabilities of these polymers in acidic conditions is associated with the different nucleophilicities of their carbonyl oxygen atoms, while in basic conditions the differences are associated with the different electrophilicities of the corresponding carbonyl carbon atoms. With regard to the hydrolysis results and the structural and chemical nature of the polymer backbones, degradation mechanisms are proposed for the acid- and base-catalyzed hydrolyses of PPC, PCL and PLA.     

Synthesis and characteristics of a novel aliphatic polycarbonate,poly[(propylene oxide)‐co‐(carbon dioxide)‐co‐(γ‐butyrolactone)]

A novel aliphatic polycarbonate, poly[(propylene oxide)‐co‐(carbon dioxide)‐co‐(γ‐butyrolactone)] [P(PO? CO₂? GBL)], was synthesized by the copolymerization of carbon dioxide, propylene oxide (PO) and γ‐butyrolactone (GBL). The resulting copolymers were determined by FTIR and NMR spectral analysis with viscosity‐average molecular weights (M_v) from 50 000 to 120 000 g mol^?1. According to elemental analysis, the calculated data of elemental contents in P(PO? CO₂? GBL)44 were close to the found data. The result showed that GBL was inserted into the backbone of poly[(propylene oxide)‐co‐(carbon dioxide)] successfully. GBL offered an ester structural unit that gave the copolymer better degradability. The correlations between reaction conditions and properties were studied. When GBL content increased, the M_v and the glass transition temperature (T_g) of the copolymers improved relative to an identical copolymer without GBL. Prolonging the reaction time of the copolymerization resulted in increases in M_v and T_g. P(PO? CO₂? GBL) exhibited a high T_g above 40 °C. The rate of backbone degradation increased with increasing GBL content. Copyright © 2005 Society of Chemical Industry     

Block copolymerization of carbon dioxide with cyclohexene oxide and 4-vinyl-1-cyclohexene-1,2-epoxide in based poly(propylene carbonate) by yttrium-metal coordination catalyst

The coordination system, Y(CF₃CO₂)₃ (I)-Zn(Et)₂ (II)-m-hydroxybenzoic acid (III), was found to be the most active catalyst to generate poly(propylene carbonate) (PPC) from carbon dioxide and propylene oxide (PO) in 1,3-dioxolane. A high yield and a high molecular weight could be obtained at the conditions of a II/I molar ratio of 20, a III/II molar ratio of 1.0, a temperature of 60 °C, and a pressure of 2.76 MPa. The carbonate content in the resultant PPC was found to be nearly 100%.The block copolymerization in the based PPC was carried out by in situ introducing an epoxide other than PO right after the copolymerization of carbon dioxide with PO using the same catalyst system. The IR and ¹H NMR spectra as well as the measured molecular weights verified the resulting copolymers were block copolymers. For the block copolymerization of CO₂ with cyclohexene oxide and CO₂ with 4-vinyl-1-cyclohexene-1,2-epoxide in the based PPC, the yield as well as the cyclohexene carbonate and the 4-vinyl-1-cyclohexene carbonate contents were found to increase with increasing temperature. The most appropriate temperature was around at 80 °C. The weight-average molecular weights of the block copolymers lay in a range from 2.44×10⁵ to 3.16×10⁵, the polydispersity in a range from 5.0 to 6.3, and the 10% weight loss temperature in a range from 226 to 253 °C. The thermal and mechanical properties of the resultant block copolymers lay between those of PPC, poly(cyclohexene carbonate), and poly(4-vinyl-1-cyclohexene carbonate), indicating the desired properties of a polymer can be achieved via block copolymerization.     

Thermotropic liquid crystallinity,thermal decomposition behavior,and aggregated structure of poly(propylene carbonate)/ethyl cellulose blends

Maleic anhydride end capped poly(propylene carbonate) (PPC‐MA) was blended with ethyl cellulose (EC) by casting from dichloromethane solutions. The thermotropic liquid crystallinity, thermal decomposition behavior, and aggregated structure were investigated by differential scanning calorimetry (DSC), thermogravimetry (TGA), and wide angle X‐ray diffraction (WAXD). DSC exhibits thermotropic liquid crystallinity in the rich EC composition range. TGA shows that thermal decomposition temperatures were elevated upon interfusing EC into PPC‐MA. WAXD corroborates that EC and PPC‐MA/EC blend films cast from dilute dichloromethane solution possessed cholesteric liquid crystalline structure in the rich EC composition range, and that dilution of PPC‐MA with EC increased the dimension of noncrystalline region, leading to a more ordered packed structure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 584–592, 2006     

Inhibitory effect of hydrogen bonding on thermal decomposition of the nanocrystalline cellulose/poly(propylene carbonate) nanocomposite

Biodegradable poly(propylene carbonate, PPC) is a typical noncrystalline polymer from the copolymerization of carbon dioxide (CO₂) with propylene oxide (PO). But it is easy to be degraded to propylene carbonate (PC) via backbiting route during heat process (above 170°C), which limits its application. This work reports the introduction of biodegradable nanocrystalline cellulose (NCC) which was exfoliated from microcrystalline cellulose (MCC) by acid hydrolysis into PPC, affording a biodegradable PPC/NCC nanocomposite with improved thermal decomposition temperatures (the initial decomposition temperature, T_5wt% was up to 265°C). Impressively, the thermal decomposition of PPC to PC at 200°C within 4.0 h was dramatically inhibited by introducing NCC, which was evident by ¹H NMR spectra. This could be attributed to the hydrogen bonding interaction between NCC and PPC. Moreover, the film of PPC/NCC nanocomposite had not deformed when it was heated at 110°C for 4 h. In application, such biodegradable nanocomposite is a promising disposable package material. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39847.     

Kinetic study of CO2 fixation into propylene carbonate with water as efficient medium using microreaction system

Carbon dioxide (CO₂) utilization and fixation have become one of the most important research areas nowadays due to the increase of global greenhouse effect. Cyclic carbonate, which is widely used in various fields, can be synthesized by fixation of CO₂ with epoxide in industry. Moreover, the synthesis of cyclic carbonate is a 100% atom economical reaction, which makes it eco-friendly and promising. To enhance the reaction efficiency and safety, a microreaction system was used as the platform for cycloaddition reaction. In this work, tetrabutylammonium bromide (TBAB) was chosen as catalyst, and propylene oxide (PO) as a mode substrate. Interestingly, the addition of water can increase the propylene carbonate (PC) yield and decrease the activation energy considerably, proving water as catalyst promoter for PC synthesis. PC yield and selectivity could reach 91.6% and 99.8%, respectively. The Influence factors and kinetic equation for CO₂ cycloaddition were obtained as well.     

CO2催化转化制碳酸丙烯酯研究进展：催化剂设计、性能与反应机理

CO₂催化转化合成碳酸丙烯酯（PC）是CO₂资源化循环利用的典型反应，同时产物PC作为重要的极性溶剂和聚合物单体在锂离子电池和高性能聚合物等关键领域的需求激增，因此受到科研界和工业界的关注。本文简要介绍了从CO₂出发催化转化合成PC的现有反应路径，详细介绍了目前应用最广泛的CO₂-环氧丙烷（PO）羧基化反应体系，包括CO₂-PO羧基化反应涉及的各种均相和非均相催化体系及其近期研究进展，重点总结了催化剂的设计、构效关系与反应机理。最后，提出了为实现CO₂-PO羧基化合成PC工艺的可持续发展所需解决的问题，并对此提出了解决思路和未来发展方向，以期为CO₂高效转化为绿色环保化学品PC技术的发展提供参考。     

Copolymerization of propylene oxide and carbon dioxide in the presence of diphenylmethane diisoyanate

To improve the thermal and mechanical properties of poly(propylene carbonate) (PPC), the copolymerization of CO₂ with PO was successfully carried out in the presence of a third monomer, 4,4′-diphenylmethane diisocyanate (MDI) using supported multi-component zinc dicarboxylate as catalyst. Chemical structure, the molecular weight, as well as thermal and mechanical properties of the resulting new copolymers were fully investigated. The experimental results show that the yield increases with increasing MDI feed content from 0 to 2 wt.%. The introduction of MDI leads to an increase in the molecular weight of PPC with light crosslinking. When the MDI feed content is lower than 3 wt.%, the PPC copolymers have number average molecular weight (Mn) ranging from 153 K to 424 K g/mol and molecular weight distribution (MWD) values ranging from 1.71 to 2.79. The resulting PPC copolymers show higher glass transition temperature (Tg) and decomposition temperature compared with poly(propylene carbonate) (PPC) without MDI. Considering the gel content of the resulting copolymers, the optimized MDI feed content should be smaller than 1.5 wt.% based on PO content. The introduction of small amount of MDI provides a very effective way to improve the mechanical properties and thermal stabilities of PPC due to the increase in its molecular weight.     

Cross-linkable and thermally stable aliphatic polycarbonates derived from CO2, propylene oxide and maleic anhydride

Poly(propylene carbonate maleate) (PPCMA) was successfully synthesized from carbon dioxide with propylene oxide and maleic anhydride using supported zinc glutarate as catalyst. The PPCMA can be readily cross-linked using dicumyl peroxide (DCP) as a cross-linking agent. The gel content, thermal performance and mechanical properties of the cross-linked PPCMA were then investigated. The results showed that the gel content increased with increasing DCP content and reaction temperature. The as-prepared PPCMA showed higher glass transition temperature (T _g) and decomposition temperature compared with uncross-linkable poly(propylene carbonate) (PPC). The introduction of small amount of cross-linkable moiety provides a very effective way to improve the thermal stability and to extend the molecular weight of PPC, consequently extending its application area.     

PPC-MA/PETG共混型生物降解材料的结构与性能研究

采用熔融共混法制备了马来酸酐(MA)封端聚碳酸亚丙酯(PPC)和聚对苯二甲酸乙二醇酯-1,4-环己烷二甲醇酯(PETG)的共混物(PPC-MA/PETG),采用套管上吹法将共混物吹塑成膜.通过差示扫描量热仪(DSC)、热失重分析(TGA)及扫描电子显微镜(SEM)等手段系统地研究了共混物的热、力学性能及形貌.结果表明:PPC-MA/PETG共混物为部分相容体系;MA封端PPC可以提高PPC的热分解温度(T-5%),PETG与PPC-MA共混进一步提高了PPC的热性能;当PETG含量低时,PETG作为岛相分散在PPC基体中,随着含量的增加,共混物将发生"海-岛"结构转变成"海-海"结构;共混物薄膜的力学性能较纯PPC大幅增强,从4.7MPa提高到16.93MPa.PPC-MA与PETG共混可以获得力学性能较好的膜材料,改善PPC材料的缺陷,在包装、生物医用材料等领域具有广阔的应用前景.     

Copolymerization of carbon dioxide and propylene oxide using zinc adipate as catalyst

Zinc adipate was synthesized from zinc oxide with adipic acid by different methods. Their chemical structure and crystalline morphology were determined by Fourier transform infrared spectroscopy (FTIR), wide‐angle X‐ray diffraction (WXRD), and scanning electron microscopy (SEM) techniques. The results showed that the zinc adipate synthesized under magnetic stirring possessed higher degree of crystallinity than that synthesized under mechanical stirring due to the different stirring strength, and therefore exhibited greater catalytic activity for the copolymerization between CO₂ and propylene oxide (PO). The optimum condition for the copolymerization of CO₂ and PO was also investigated. Very high catalytic activity of 110.4 g polymer/g catalyst was afforded under optimizing copolymerization condition. NMR spectra revealed that the synthesized poly(propylene carbonate) (PPC) had a highly alternating copolymer structure. DSC and TGA examinations showed that the glass transition temperature and decomposition temperature of the PPC with M_n = 41,900 Da were 27.7 and 248°C, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 200–206, 2006