Controlled Random Terpolymerization of β -Propiolactone, Epoxides, and CO 2 via Regioselective Lactone Ring Opening

Open AccessCCS ChemistryRESEARCH ARTICLE1 Jan 2022Controlled Random Terpolymerization of β-Propiolactone, Epoxides, and CO2 via Regioselective Lactone Ring Opening Wen-Bing Li, Bai-Hao Ren, Ge-Ge Gu and Xiao-Bing Lu Wen-Bing Li State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, Liaoning 116024 , Bai-Hao Ren State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, Liaoning 116024 , Ge-Ge Gu State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, Liaoning 116024 and Xiao-Bing Lu *Corresponding author: E-mail Address: [email protected] State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, Liaoning 116024 https://doi.org/10.31635/ccschem.021.202000728 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail The random ring-opening terpolymerization of CO2, epoxides, and lactones remains challenging, mainly because CO2/epoxide copolymerization and lactone ring-opening polymerization typically proceed at very different rates. Herein, we report the preparation of novel statistical terpolymers with random distributions of carbonate and ester units (up to 40% junction units) via the one-pot reaction of β-propiolactone (BPL), epoxides, and CO2 under mild conditions using a binary catalyst system consisting of SalcyCo(III)OTs (Salcy = N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexane; OTs = p-toluenesulfonate) and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene. Since this catalytic system could yield similar reaction rates for alternating epoxide/CO2 copolymerization and BPL polymerization, terpolymers with nearly identical compositions were produced at various time points. CO2 played an important role in preventing intra- and/or intermolecular transesterification side reactions. Thereby, the terpolymerization proceeded in a controlled manner, allowing for the fine-tuning of molecular weight and composition. Two-dimensional nuclear magnetic resonance (NMR) analysis and density functional theory (DFT) calculations suggested that the nucleophilic attack of the coordinated BPL by carbonate ions cleaved the alkyl C–O bond predominantly rather than the acyl C(=O)–O bond, typically observable during the nucleophilic ring-opening polymerization of BPL. These findings have opened up a new avenue for preparing a broad family of biodegradable polymers with adjustable properties. Download figure Download PowerPoint Introduction The growing concerns over the global accumulation of tremendous amounts of polymer waste with no or very low degradability have motivated the development of degradable polymers with labile linkages, including ester and carbonate units.1–5 Poly(β-hydroxyalkanoate)s are a class of aliphatic polyesters produced naturally by bacteria.6 The most studied poly(β-hydroxyalkanoate) is isotactic poly(3-hydroxybutyrate) (PHB), a highly crystalline thermoplastic material. As an alternative to fermentative synthesis, PHB can also be produced by the catalytic ring-opening polymerization of β-butyrolactone, a low-cost and readily available feedstock-generated carbonylation of epoxides.7–10 Commonly, the nucleophilic ring opening of lactones occurs at the ester group through the cleavage of an acyl C(=O)–O bond, leading to the formation of alkoxy chain ends.11–14 However, alkoxy chain ends can react not only with the ester groups of lactone monomers but also the ester groups of the resulting polyester backbone via intra- and/or intermolecular transesterification, especially at high conversions and temperatures. These side reactions result in products with uncontrolled molecular weights and molecular weight distributions. In contrast to ring opening at acyl C(=O)–O bonds, ring opening at alkyl C–O bonds of lactones affords carboxy chain ends, thereby avoiding the aforementioned side reactions.15–19 Despite the advantages of poly(β-hydroxyalkanoate)s, their industrial applications have been limited by high stiffness and low impact strength. A feasible path for improving the mechanical properties of these materials is the incorporation of other monomers by copolymerization. Polycarbonates, derived from copolymerization of epoxides and greenhouse gas, CO2, deliver both economic and environmental benefits.20–27 Furthermore, polycarbonates and polyesters have been combined in block copolymers to improve the thermal and mechanical properties. Block copolymers can be synthesized by the terpolymerization of CO2, epoxides, and lactones or lactides through multiple steps28–30 or chemoselective operations.31–34 Polycarbonates with one –OH end group, synthesized by copolymerization of epoxides and CO2, have been used as initiators for the ring-opening polymerization of lactones/lactides to obtain AB diblock terpolymers.28 Alternatively, trace water has been used as a chain-transfer agent to obtain polycarbonate initiators with two –OH end groups that produce ABA triblock terpolymers.29 CO2 acts as a switching agent in the terpolymerization of cyclohexene oxide (CHO), CO2, and ε-caprolactone. For example, in a one-pot reaction, ring-opening polymerization of ε-caprolactone and the copolymerization of CHO and CO2 could be tuned by incorporating and removing CO2.31 The polymerization of multiple components in one pot, or a single step provides an opportunity to produce multiblock/statistical copolymers containing carbonate and ester components. Nevertheless, when a single catalyst system is used, the activities of the different monomers vary, and competitive reactions occur, resulting in difficulties in achieving controllable copolymerization. To produce multiblock copolymers in one pot, catalysts with distinct selectivities have been used.35–39 In such systems, chain-transfer reactions can form bridges between the independent chains selectively generated by different catalysts.40,41 Although considerable efforts have been made to balance the reactivities of the various monomers in lactone/CO2/epoxide terpolymerization, hybrid copolymers with randomly distributed ester and carbonate units have rarely been reported. Compared with the case of lactide or ε-caprolactone, terpolymerization of β-butyrolactone with CO2 and epoxides lead to a large difference in monomer reactivity. In 2017, Rieger et al.42 realized the terpolymerization of β-butyrolactone, CHO, and CO2 in a one-pot reaction utilizing a Lewis acid BDI-Zn-N(SiMe3)2 catalyst, in which CO2 reacted as a switching agent for polymerization control. Applying 40 bar CO2 to the three-component system led to exclusive copolymerization of CO2/CHO, whereas the use of 3 bar CO2 resulted in a significant decrease in the reaction rate for CO2/CHO coupling, affording a terpolymer with approximately 16% junction units. Trivalent cobalt complexes of salicylaldimine have been shown to be highly efficient catalysts for alternating copolymerization of CO2 and epoxides.43,44 Therefore, we investigated the one-pot terpolymerization of β-propiolactone (BPL), epoxides, and CO2 using a SalcyCo(III)-based catalyst system. In addition, junction units were characterized in detail, and density functional theory (DFT) calculations were performed to clarify the mechanistic aspects of forming terpolymers with random distributions of carbonate and ester units. Experimental Methods Representative procedure of terpolymerization of BPL, epoxides and CO2 All manipulations involving air- and/or water-sensitive compounds were carried out in a glovebox or with the standard Schlenk techniques under dry nitrogen. In a pre-dried 20 mL autoclave equipped with a magnetic stirrer, SalcyCo(III)OTs (0.02 mmol, 1 equiv) was dissolved in colorless racemic terminal epoxide (10 mmol, 500 equiv) to form a reddish-brown solution. Then 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD; 0.02 mmol, 1 equiv) was added under a nitrogen atmosphere. The mixture solution was stirred for about 10 min, followed by the addition of BPL (10 mmol, 500 equiv). Next, the autoclaved mixture was put into a water bath at 25 °C, and then pressurized to appropriate pressure with CO2. After the allotted reaction time, the autoclave solution was put into a water bath at 0 °C for 10 min, carefully releasing the CO2. A small amount of the product was removed for proton nuclear magnetic resonance (1H NMR) analysis. The crude terpolymer product was dissolved in CH2Cl2 and transferred to a flask. The solution was precipitated with excess methanol. This process was repeated three to five times to rid of the catalyst, and the white polymer was obtained by vacuum-drying. Results and Discussion CO2-controlled regioselective ring-opening polymerization of BPL Typically, the nucleophilic ring opening of lactones occurs through the acyl C(=O)–O bond cleavage, leading to the formation of alkoxy chain ends. This process can give rise to uncontrolled molecular weight distributions via intra- and/or intermolecular transesterification side reactions. Although MTBD is a highly active catalyst for the ring-opening polymerization of BPL, the resultant polymers had a very low molecular weight (Mn) of 1100 Da and a broad dispersity (Ð) of 2.19 (Scheme 1, (a)). [(BPL)n + Na+] and [(BPL)n + K+] were observed in the electrospray ionization-quadrupole-time of flight (ESI-Q-TOF) mass spectrum in the positive ion mode ( Supporting Information Figure S1), indicating the formation of cyclic polymers. This was ascribed to the nucleophilic intramolecular back-biting of the alkoxy chain end at the C(=O)–N bond leading to chain termination due to the good leaving ability of the sterically hindered MTBD. Interestingly, the addition of 2 equiv of benzoic alcohol (BnOH) produced predominantly the linear polyester, with the enhanced Mn of 11,800 Da and a Ð of 1.44 (Scheme 1, (b)). Notably, when the experiment was performed under a CO2 atmosphere, the resulting polymer possessed a high Mn of 18,000 Da and a low Ð of 1.20 (Scheme 1, (c)). In the ESI-Q-TOF mass spectrum in the negative ion mode, a series of molecular ion peaks based on m/z = 151 (BnO− + CO2) at an interval of 72 (the unit of BPL), corresponding to the linear PBPL chains capped with BnO/COOH chain ends, were visible, indicating that CO2 participated in the initiation of the polymer chain (Figure 1). The presence of CO2 changed the initiator from benzyloxy anion into benzyl carbonate group, thereby resulting in variations in the ring-opening mode of BPL from the acyl C(=O)–O bond cleavage to alkyl C–O bond cleavage to afford a polymer carboxylate group end. The latter cleavage mode avoided inter- and/or intramolecular transesterification side reactions. Moreover, with the use of SalcyCo(III)OTs/MTBD/BnOH/CO2 (Salcy = N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminocyclohexane; OTs = p-toluenesulfonate) system for BPL polymerization even at 50 °C (Scheme 1, (d)), the resulting polyesters exhibited narrow distribution of Р= 1.18. Further increasing substrate feed ratio, up to 97,000 Da and a low Ð of 1.19 were observed in the resultant polyesters ( Supporting Information Figure S2 and Table S1, entry 7). Scheme 1 | Ring-opening polymerization of BPL mediated by various catalyst systems: (a) MTBD, (b) MTBD/BnOH, (c) MTBD/BnOH/CO2, and (d) SalcyCo(III)OTs/MTBD/BnOH/CO2. Download figure Download PowerPoint Terpolymerization of BPL, epoxides, and CO2 Previously, a binary catalyst system consisting of a trivalent cobalt complex of salicylaldimine as an electrophile and a sterically hindered strong organic base as a nucleophile performed well for CO2/propylene oxide (PO) copolymerization to selectively produce poly(propylene carbonate) (PPC) with <95% head-to-tail connectivity and <99% carbonate linkages.43 Inspired by the experiments regarding the regioselective ring-opening polymerization of BPL mediated by various catalyst systems mentioned earlier, we developed a great interest in the design of terpolymerization employing BPL, epoxides, and CO2 in which CO2 acted as both the reactant and the regioselective lactone ring-opening controlling reagent. In this terpolymerization, the initiation reaction was expected to be triggered through the ring opening of the epoxide bound to the Co(III) center attack by MTBD, affording the alkoxy chain end. This process was followed by a fast insertion of CO2 to Co–O bond provided by the carbonate chain end, which attacked BPL at the alkyl C–O bond, just like the benzyl carbonate group in the MTBD/BnOH/CO2-mediated BPL polymerization. Figure 1 | ESI-Q-TOF mass spectrum of reaction mixtures obtained by the polymerization of MTBD/BnOH/BPL/CH2Cl2 (1/2/1000/2000, molar ratio) at 25 °C and 2.0 MPa CO2 for 60 min. Download figure Download PowerPoint First, a SalcyCo(III)OTs/MTBD/BPL/PO (1/1/500/500, molar ratio) mixture was placed in an autoclave at 25 °C under 2.0 MPa CO2 pressure. Noted that to avoid BPL homopolymerization, SalcyCo(III)OTs and MTBD were first dissolved in PO and stirred for 10 min before the addition of BPL and CO2 injection. After 2 h, a statistical terpolymer with carbonate and 3-hydroxypropionate components in a 1:1 ratio was produced. This polymer had a molecular weight of 2.6 kDa and a relatively narrow molecular weight distribution of 1.13 (Table 1, entry 1). Notably, the polymers obtained at various time points had nearly identical compositions, as confirmed by 1H NMR analysis (Table 1, entries 1–4). The number-average molecular weight increased linearly with reaction time. The resultant terpolymers exhibited only one elution peak with a low dispersity of <1.20 and produced a glass transition temperature (Tg) of 10.2–17.4 °C. Moreover, no cyclic carbonate or ether units were observed in the 1H NMR spectra of the crude products, indicating that the binary catalyst system retained good terpolymerization selectivity. Table 1 | Terpolymerization of BPL, Epoxides, and CO2a Entry Epoxide Time (h) Epoxide Conversion (%)b BPL Conversion (%)b [Carbonate]/[Ester] (mol/mol)b Mn (Ð) (kg/mol)c Tg (°C) 1 PO 2 11 11 1.0 2.6 (1.13) 10.2 2 PO 4 31 31 1.0 7.4 (1.15) 11.6 3 PO 6 58 56 1.0 13.6 (1.17) 14.4 4 PO 8 77 75 1.0 16.2 (1.19) 17.4 5 FurGE 3 23 23 1.0 5.0 (1.25) -5.3 6 FurGE 4 47 46 1.0 12.7 (1.24) 6.6 7d PGE 6 51 25 2.0 11.4 (1.21) 42.4 8 TBGE 9 18 73 0.2 7.8 (1.24) -6.0 aReaction conditions: 25 °C, 2.0 MPa CO2, SalcyCo(III)OTs/MTBD/BPL/epoxide = 1/1/500/500, 10 mmol BPL. bDetermined by 1H NMR spectroscopy of the crude polymer sample. PO conversion was calculated based on the ratio of propylene carbonate to ester units, compared with the amount of reacted BPL. cDetermined by gel permeation chromatography in tetrahydrofuran (THF), calibrated with polystyrene. d2% cyclic carbonate was formed. Previously, we demonstrated that in CO2/epoxide copolymerization mediated by a Co(III) complex-based catalyst system, the insertion of CO2 into the Co–O bond was not a rate-determining step but a fast process.45 Therefore, similar reactivities of PO and BPL during terpolymerization with CO2 allowed the terpolymer composition to be adjusted easily by altering the PO/BPL feed ratios. The thermal performance of the terpolymers varied depending on the carbonate/ester unit ratio (Figure 2 and Supporting Information Table S2). For the CO2/PO/BPL terpolymers with a carbonate unit content of <20%, the Tg value was low (≤0 °C), and the Tm value was decreased relative to that of poly(3-hydroxypropionate) (Tm = 69.7 °C) (Figure 2, curves A–C). In contrast, when the carbonate content in the terpolymer was <28%, the Tg value increased to more than 0 °C but remained significantly lower than that of PPC (Tg ∼ 40 °C) (Figure 2, curves D–F). Figure 2 | Differential scanning calorimetry (DSC) profiles of PO/CO2/BPL terpolymers: (curve A) poly(3-hydroxypropionate) ( Supporting Information Table S2, entry 1), (curve B) terpolymer with a carbonate content of 11.2% ( Supporting Information Table S2, entry 2), (curve C) terpolymer with a carbonate content of 19.3% ( Supporting Information Table S2, entry 3), (curve D) terpolymer with a carbonate content of 28.0% ( Supporting Information Table S2, entry 4), (curve E) terpolymer with a carbonate content of 76.3% ( Supporting Information Table S2, entry 5), and (curve F) PPC ( Supporting Information Table S2, entry 6). Conditions of DSC analysis are described in the Supporting Information. Download figure Download PowerPoint Several terminal epoxides were terpolymerized with CO2 and BPL using SalcyCo(III)OTs/MTBD binary catalyst system. Furfuryl glycidyl ether (FurGE) and BPL showed similar reactivities during terpolymerization with CO2 to afford statistical terpolymers with nearly identical carbonate contents and ester units (Table 1, entries 5 and 6). In contrast, during terpolymerization with CO2, phenyl glycidyl ether (PGE) exhibited higher reactivity than BPL, whereas tert-butyl glycidyl ether (TBGE) showed lower reactivity than BPL (Table 1, entries 7 and 8). Therefore, the contents of carbonate and ester units in the resulting terpolymers varied with reaction time. 1H NMR spectra, GPC spectra, and DSC spectra of the resulted terpolymers are provided in Supporting Information Figures S3–S9. BPL ring-opening modes in the terpolymerization The ring opening of β-lactones proceeded via either acyl C(=O)–O bond cleavage, leading to alkoxy chain ends, or alkyl Cβ–O bond cleavage, leading to carboxy chain ends. In the terpolymerization of BPL, PO, and CO2, these two BPL ring-opening modes led to four different junction units between the carbonate and ester units (Scheme 2). Scheme 2 | Possible BPL ring-opening modes and possible junction units in the terpolymers. Download figure Download PowerPoint Recently, Rieger and co-workers reported that the Lewis acid BDICF3-Zn-N(SiMe3)2 catalyst-mediated terpolymerization of β-butyrolactone, CHO, and 3 bar CO2 afforded a terpolymer with a low junction unit content of ∼16%. In contrast, when 40 bar CO2 was used, only a polycarbonate was produced via copolymerization with the epoxide.42 For β-butyrolactone, the stereochemistry of the methine carbon was retained during acyl C(=O)–O bond cleavage, whereas alkyl C–O bond cleavage typically led to inversion. Based on polarimetry and two-dimensional NMR spectroscopy, they proposed that β-butyrolactone was ring-opened through acyl C(=O)–O bond cleavage to produce alkoxide chain ends. However, in this present case, the mechanism for BPL ring opening could not be determined using polarimetry because the β-carbon of this lactone provided no information about the stereoconfiguration. Thus, to clarify the ring-opening position in BPL during terpolymerization, enantiopure (R)-PO (ee < 99%) was polymerized with BPL and CO2 to produce an (R)-PO/CO2/BPL terpolymer. In comparison with a blend of (R)-PPC and poly(3-hydroxypropionate), the 1H and 13C NMR spectra of the (R)-PO/CO2/BPL terpolymer showed obvious splitting patterns with various chemical shifts ( Supporting Information Figures S10 and S11), indicating that the carbonate and ester components were randomly distributed in the terpolymer. Moreover, 1H–13C heteronuclear multiple bond correlation (HMBC) analysis confirmed the coupling of the Ha′ atom (4.4 ppm) with the Ca′ atom (154 ppm) of the carbonate units (Figure 3), ascribed to junction unit A or D (Scheme 2). Besides, the coupling of the Hb′ atom (4.1–4.3 ppm) with the Cb′ atom (170 ppm) of the ester units was observed, corresponding to junction unit C. However, no coupling was detected between the Hc′ atom (5.0 ppm) and the Cb′ atom (170 ppm) of the ester units, indicating that junction unit B was absent in the terpolymer. These observations indicated that BPL ring-opening selectively occurred at the alkyl C–O bond. In comparison, the HMBC-NMR spectrum of the (R)-PPC/poly(3-hydroxypropionate) blend did not show any junction units between carbonate and ester units. Notably, changing the CO2 pressure from 0.5 to 3.5 MPa did not affect the selective cleavage of the alkyl C–O bond of BPL during the terpolymerization process. Figure 3 | HMBC-NMR spectra of an (R)-PPC/poly(3-hydroxypropionate) blend and a statistical (R)-PO/CO2/BPL terpolymer in CDCl3. Download figure Download PowerPoint DFT calculations showed that the ring opening of BPL via alkyl Cβ–O bond cleavage (8.6 kcal/mol) required less energy than that via acyl C(=O)–O bond cleavage (16.9 kcal/mol), which is in agreement with the experimental results (Scheme 3). Further, the DFT-calculated Gibbs free energies for the ring opening of both BPL and PO by carboxy chain ends were very low, indicating that the reaction rates of both monomers are fast enough to produce terpolymers with random distributions. Scheme 3 | Free energies of possible transition states for BPL ring opening. Download figure Download PowerPoint Quantitative analysis of the junction units in terpolymers Supporting Information Figure S12 shows the 1H–13C heteronuclear spectra of the blend and the PO/CO2/BPL terpolymer. For the the atom ppm) and the atom ppm) in the 13C NMR spectrum were with the Ha′ atom (4.4 ppm) and the Hb′ atom (4.1–4.3 ppm) in the 1H NMR This result indicated that the and to junction units D and The 13C NMR spectrum demonstrated that the junction unit content in the PO/CO2/BPL terpolymer was up to 40% (Figure the resultant terpolymers exhibited only one Tg value between 10.2 and 17.4 °C, depending on the molecular These results that the carbonate and ester units were distributed randomly in the terpolymers. Figure 4 | Quantitative 13C NMR spectrum of a statistical PO/CO2/BPL terpolymer in CDCl3. units for 40% of the terpolymer. Download figure Download PowerPoint into the statistical terpolymerization of BPL, PO, and CO2 the of the reaction, the polymer chain was characterized by electrospray mass (Figure In the ESI-Q-TOF mass spectrum in positive ion mode, + + PO + + + + PO + and + + + + PO + were observed, indicating that MTBD acted as an initiator for polymer chain from coupling and BPL ring opening showed similar reaction rates in the terpolymerization with CO2 to produce statistical terpolymers. The random distribution of the terpolymers was retained even when the reaction time was (Figure Figure 5 | ESI-Q-TOF mass spectra of reaction mixtures obtained by the terpolymerization of at 25 °C and 2.0 MPa CO2 for (a) min and (b) min (the spectrum is shown in Supporting Information Figure Download figure Download PowerPoint The terpolymer was also characterized by NMR spectroscopy one was indicating that the carbonate and ester components were in the terpolymer. In contrast, the blend of PPC and poly(3-hydroxypropionate) two distinct ( Supporting Information Figure These findings confirmed that the statistical terpolymer was the product of PO/CO2/BPL performed competitive polymerization experiments to the of the experimental For these which has the reaction rate as BPL, was used of FurGE and BPL at various feed were terpolymerized with CO2 at and the monomer reactivity were determined = = (Figure 6 and Supporting Information Table The results indicated that the carbonate chain end was more to attack BPL, whereas the carboxy chain end attacked epoxides However, because the reactivity of both monomers were to 1, alternating could not be random terpolymers were with the experimental As a statistical terpolymer with carbonate/ester junction units was produced by the terpolymerization of BPL, CO2, and FurGE ( Supporting Information Figures This value was significantly higher than the junction unit content in the of in the enantiopure cobalt Figure 6 | and for terpolymerization mediated by the SalcyCo(III)OTs/MTBD catalyst system. The corresponding experimental are described in the Supporting Information Table Download figure Download PowerPoint Based on the a reaction mechanism was as shown in Scheme First, the nucleophilic attack of MTBD on PO to the epoxide ring opening to form an alkoxy chain end. After the insertion of CO2, the alkoxy chain end a carbonate chain end. BPL and PO can be ring-opened by the carbonate chain end to afford carboxy or alkoxy chain ends. The latter can be into a carbonate chain end by CO2 the and ends can attack BPL or PO, and these proceed with similar reaction rates. insertion of CO2 into the Co–O bond the of PO and ring opening at the acyl C(=O)–O bond during the reaction with BPL. Therefore, the BPL monomers are ring-opened via alkyl Cβ–O bond cleavage to form carboxy chain ends. Notably, similar reactivities of the carboxy and carbonate ends with PO and BPL resulted in a random terpolymerization, affording terpolymers with high junction unit contents of up to Scheme 4 | mechanism for PO/CO2/BPL Download figure Download PowerPoint synthesized statistical terpolymers with a single glass transition temperature via a one-pot reaction of BPL, epoxides, and CO2 using a binary catalyst system consisting of SalcyCo(III)OTs and MTBD under mild Based on two-dimensional NMR analysis and DFT the nucleophilic attack of coordinated BPL by carbonate ions was determined to at the alkyl C–O bond. The insertion of CO2 into the Co–O bond various side reactions such as alkoxy chain end formation and intramolecular and/or intermolecular transesterification, as well as epoxide Quantitative 13C NMR analysis suggested that the terpolymers had junction unit contents of up to To the of this is the only of a statistical carbonate/ester terpolymer in which the two components are distributed in the backbone based on The properties were by the carbonate/ester ratio in the which could be easily controlled using the PO/BPL feed This the of on more efficient catalysts for polymerization to various novel materials with properties and Supporting Information Supporting Information is available and of new including 1H and 13C NMR spectra, GPC and DSC as well as ESI-Q-TOF mass spectrum of various compounds and ( Figures of The no Information This was by the of and and the for and in University of an C. and of and of and with