Synergetic Organocatalysis for Eliminating Epimerization in Ring-Opening Polymerizations Enables Synthesis of Stereoregular Isotactic Polyester

Journal of the American Chemical Society, Год журнала: 2018, Номер 141(1), С. 281 - 289

Опубликована: Дек. 4, 2018

Ring-opening polymerization of O-carboxyanhydrides (OCAs) can furnish polyesters with a diversity functional groups that are traditionally hard to harvest by lactones. Typical ring-opening catalysts subject unavoidable racemization most OCA monomers, which hampers the synthesis highly isotactic crystalline polymers. Here, we describe an effective bifunctional single-molecule organocatalysis for selective OCAs without epimerization. The close vicinity both activating in same molecule engenders amplified synergetic effect and thus allows use mild bases, thereby leading minimal epimerization polymerization. manOCA monomer (OCA from mandelic acid) mediated organocatalyst yields poly(mandelic (PMA) controlled molecular weights (up 19.8 kg mol–1). Mixing two enantiomers PMA generates first example stereocomplex this area, displayed distinct Tm values around 150 °C. Remarkably, moisture-stable, recyclable, easy use, allowing sustainable scalable stereoregular polyester.

Язык: Английский

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Phosphazene Bases as Organocatalysts for Ring‐Opening Polymerization of Cyclic Esters

Macromolecular Rapid Communications, Год журнала: 2018, Номер 39(24)

Опубликована: Окт. 1, 2018

Abstract Over the past several years, organocatalyzed polymerization reactions have attracted considerable attention, and these efforts led to major advances. A large number of organic compounds been proven active for a variety monomers. In particular, phosphazene bases (PBs) are family extremely strong, non‐nucleophilic, uncharged auxiliary bases, shown their remarkable potential as organocatalysts ring‐opening (ROP) cyclic By deprotonation weak acids or in combination with lithium cation, PBs significantly enhance nucleophilicity initiator/chain‐end, thus allowing fast usually controlled anionic polymerization. this feature article, recent advances phosphazene‐catalyzed ROP esters summarized. This review is divided into three sections, including general features, design synthesis, catalytic applications. It aims provide critical analysis PB‐mediated systems useful guide further applied polymer synthesis. An outlook given at end.

Язык: Английский

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Programmable High-Throughput Platform for the Rapid and Scalable Synthesis of Polyester and Polycarbonate Libraries

Journal of the American Chemical Society, Год журнала: 2019, Номер 141(22), С. 8921 - 8927

Опубликована: Май 22, 2019

The critical role of composition, architecture, molecular weight, and weight distribution on the functional properties macromolecular materials underscores need for reproducible, robust, scalable, programmable synthetic methods to generate macromolecules that span a systematic wide range structure–property space. Herein, we describe marriage tunable highly active organic catalysts with programmed continuous-flow reactors rapidly libraries polyester polycarbonate homopolymers block copolymers exquisite efficiency control. Under conditions, controlled polymerizations occur residence times as low 6 ms (TOF = 24 000 h–1) can be readily scaled-up polymers at rate tens grams per minute. We an in-flow catalyst switch strategy enable rapid generation copolymer (100 distinct in 9 min) from monomers drastically different reactivity profiles.

Язык: Английский

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A facile method to prepare high molecular weight bio-renewable poly(γ-butyrolactone) using a strong base/urea binary synergistic catalytic system

Polymer Chemistry, Год журнала: 2019, Номер 10(10), С. 1231 - 1237

Опубликована: Янв. 1, 2019

Biorenewable poly(γ-butyrolactone) with a high molecular weight was prepared base/urea binary synergistic catalyst.

Язык: Английский

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Chemoselective Polymerization of Fully Biorenewable α-Methylene-γ-Butyrolactone Using Organophosphazene/Urea Binary Catalysts Toward Sustainable Polyesters

CCS Chemistry, Год журнала: 2020, Номер 3(1), С. 620 - 630

Опубликована: Май 14, 2020

Open AccessCCS ChemistryRESEARCH ARTICLE1 Jan 2021Chemoselective Polymerization of Fully Biorenewable α-Methylene-γ-Butyrolactone Using Organophosphazene/Urea Binary Catalysts Toward Sustainable Polyesters Yong Shen, Wei Xiong, Yongzheng Li, Zhichao Zhao, Hua Lu and Zhibo Li Shen State Key Laboratory Base Eco-Chemical Engineering, College Chemical Qingdao University Science Technology, 266042 Google Scholar More articles by this author , Xiong Beijing National for Molecular Sciences, Center Soft Matter Polymer Chemistry Physics Ministry Education, Peking University, 100871. Biobased Materials, Shandong Provincial Education Department, Zhao *Corresponding author(s): E-mail Address: [email protected] https://doi.org/10.31635/ccschem.020.202000232 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Despite the great potential biorenewable α-methylene-γ-butyrolactone (MBL) produce functional, recyclable polyester, ring-opening polymerization (ROP) MBL remains a challenge due competing highly reactive exocyclic double bond low-strained five-membered ring. In contribution, we present first organocatalytic chemoselective ROP exclusively functional unsaturated polyester utilizing phosphazene base/urea binary catalyst. We show that delicate chemoselectivity can be realized controlling temperature using selected urea catalysts. The obtained completely recycled back its monomer chemolysis under mild conditions. Experimental theoretical calculations provide mechanistic insights indicate pathway is kinetically favored with stronger acidity at low temperatures. Download figure PowerPoint Introduction polymers derived from renewable feedstocks have attracted increasing attention growing concerns over eventual consumption finite fossil fuels concomitant environmental pollution caused production disposal petroleum-based polymeric materials.1–4 Aliphatic polyesters are probably most intensively investigated sustainable polymers, such as poly(ɛ-caprolactone) (PCL), poly(glycolic acid) (PGA), poly(l-lactide) (PLLA).5 Although these aliphatic readily degraded CO2 water in nature, recycling challenge. For example, thermal or chemical depolymerization PLLA produces mixture lactide stereoisomers, cyclic oligomers, other impurities, which require tedious purification before L-LA reused.6–8 An approach address end-of-use issue materials develop closed-loop life cycles depolymerized their monomers energy efficient conditions.9,10 One emerging frontier design preparation lactones rings building blocks.11–18 Hong Chen11 γ-butyrolactone (γBL) accessible conditions La- Y-based organometallic Organophosphazene superbases, tert-Bu-P4 new trimetric superbase (CTPB; Figure 1), were later demonstrated effective organocatalysts γBL.12,13 Significantly, resultant PγBL, selectively quantitatively γBL simply heating bulk material A trans-cyclohexyl-ring-fused (3,4-T6GBL) α β positions increased ring strain relative was recently developed, polymerized into high molecular weight polymer room solvent-free conditions.14,15 also successfully establish circular cycle. same group presented similar six–five bicyclic lactone (4,5-T6GBL) organobase/(thio)urea catalysts.19 1 | (a) Two different pathways (b) structures CTPB ureas used study. success achieved past several years, fully still limited, especially those groups. et al.20 developed polythioesters biomass-sourced bridged thiolactones side chain allyl groups, further modified opportunities adjust polythioesters’ properties. Another functionalizable recyclability MBL, simplest derivative bearing an bond. naturally found tulips produced biosourced feedstocks.21 has been alternative methyl methacrylate (MMA) higher glass transition better solvent durability MBL-derived compared poly(methyl methacrylate) (PMMA).22 However, studies reported vinyl-addition (VAP) through Michael-type addition across P(MBL)VAP (Figure 1a, a) not degradable recyclable.22–27 selective even more challenging between To best our knowledge, only performed Chen al. La[N(SiMe3)2]3 yttrium-based Intriguingly, product P(MBL)ROP b), shown presence simple catalyst, LaCl3.28 Considering tolerance, metal-free facile removal catalyst residues will desirable MBL.29 Herein, organophosphazene base combination cocatalysts, makes (PMBL)ROP polyester. Methods General procedure typical (Table 1, run 5) described follows. flame-dried Schlenk tube charged (0.05 mmol, 5.2 μL) benzyl alcohol (BnOH), 59.9 mg) CTPB, (0.15 42.95 U4, 0.187 mL tetrahydrofuran (THF) glove box. sealed septum immersed cooling bath set −50 °C. After equilibrium °C 10 min, (5 0.44 mL), injected via gastight syringe begin polymerization. conducted 4 h quenching few drops acetic acid. About 3 dichloromethane (DCM) dissolve product. aliquot solution withdrawn conversion determination 1H NMR measurement. remaining poured excess cold methanol (−20 °C). precipitate washed once then dried vacuum give PMBL white powder 41.2% (202 yield. Table Results CTPB/Urea Catalystsa Run Initiator Urea [M]/[B]/[U]/[I] Sol. Temperature (°C) Time (h) C(ROP) (%)b C(VAP) Mn (kDa)c Ðc BnOH 100/1/0/1 THF 0 20 n.d. 2 U1 100/1/3/1 100 U2 54 24 U3 51 1.57 5 U4 50 5.9 1.29 6 U5 18 2.3 1.25 7d 12 n.a. 8 35 4.0 1.19 9 62 6.1 1.46 TOL 16 11 DMF −20 13 25 37 14 100/1/2/1 65 1.34 15e 100/1/1/1 100/1/3/5 47 3.2 1.31 17 100/1/3/2 52 4.4 1.33 100/1/3/0.67 45 6.7 19 200/2/6/1 43 6.4 1.56 iPrOH 49 5.4 1.28 21 Ph2CHOH 5.8 1.32 22f – 100/1/3 32 6.0 1.35 aConditions: 490 used. base. [MBL] = M THF. n.d.= determined (Mn Ð poor solubility THF). available (no precipitation occurred). bDetermined NMR. cDetermined SEC PS standards. dThe concentration M. eThe conversions cross-linking. fNo initiator added. (DMSO-d6, 400 MHz): δ (ppm): 6.10 (s, 1H, =CH2), 5.71 4.20(t, 2H, J 6.2 Hz, –OCH2–), 2.58 (t, –CH2–). 13C 165.69, 136.32, 127.41, 62.66, 30.76. Depolymerization (0.005 (0.015 7.2 U6, mg (produced MBL/KOMe/U4 100/1/3, 6.5 kDa, 1.49) added aforementioned solution. oil 48 h. Postfunctionalization 39.2 prepared CTPB/U4), equiv., 174 mercaptan, 0.02 2.8 triethylamine dissolved 0.4 dimethyl sulfoxide (DMSO). reaction 40 determine twice temperature. (CDCl3, 7.27 (br, 5H, Ph–), 4.05 3.66 PhCH2–), 2.65 –SCH2–), 2.53 –CH<), 1.90 173.51, 137.97, 128.99, 128.67, 127.27, 62.53, 42.42, 36.68, 33.05, 30.38. Discussion Chemoselective realize one should activate while inhibiting VAP simultaneously. Waymouth coworkers rapid lactones, lactides, carbonates alkoxides (thio)ureas catalysts.30,31 Interestingly, (thio)urea anions generated deprotonation activation linear open-chain esters.30,31 Very recently, others PγBL strong base/(thio)urea catalytic system, effectively ring.32–34 catalysts showed activity toward monomers.35,36 According previous studies, believe promote On hand, proposed proceed generation carbanion intermediate, requires considerably basicity than suitable pathway. As such, speculate may undergo judicious selection combinations organobases ureas. proof concept, series cyclohexyl substituted phenyl designed screened since asymmetric proven 1b, see Supporting Information Figures S1–S5).34 It gave enthalpy change ΔH −5.9 kJ mol−1 entropy ΔS −40.1 K−1, corresponded ceiling −14 [MBL]0 −52 M.28 achieve meet thermodynamic requirements. consequence, experiments (−50 °C) (8 M) favor initiator. control experiment, absence 20%, producing 1). 4-methoxyphenyl (U1) attempted feeding molar ratio MBL/CTPB/U1/BnOH 100/1/3/1. 100% within but proceeded 2). By changing substituent para-position methoxy hydrogen chloro, obtained, accompanying decreased 24% 4% (runs 4), respectively. exclusive cocatalyst, features 4-trifluoromethylphenyl group. 50% h, kDa relatively narrow distribution (run 5). deprotonated expected sequentially decrease considering gradual increase electron-withdrawing effect substitution on aromatic Thus, results appear agree well initial hypothesis weaker basic inhibit meantime. Nevertheless, although cocatalyst 3,5-bis(trifluoromethyl)phenyl exclusively, dropped 18% resulting 6). This result indicated less anion generally improve selectivity, it activity.30,37 Next, focused optimization because appeared balanced selectivity activity. CTPB/U4 lower resulted much conversions, no 7). extended time led slightly 62% comparable broader polydispersity 1.46, likely intra- intermolecular transesterification 9). Switching toluene (TOL) N,N-dimethylformamide (DMF) good 11). TOL. Of note, polymerizations exceed limit out system. contrast, remained homogeneous temperatures investigate chemoselectivity. No observed either 12). Further elevating formation 13). These suggested necessary negative Gibbs free energies thermodynamically drive discussed earlier.11 CTPB/urea plays critical role 65% 1/2 14), amount 1/1 cross-linked networks coexistence 15). propagating end bonding.30 neutral might reduce chains forming bonding anions.30 Here, U4-/U4 pair subtly adjusted served acid donor participating polymerization.30,37 Overall, prefer varied weights adjusting BnOH. MBL/BnOH 100/5 100/2 100/0.67 (see S7), initiators, isopropanol (iPrOH) diphenylmethanol (Ph2CHOH), P(MBL)ROP. BnOH, whereas bulkier groups 21). 22). common inorganic bases KOMe NaOMe S1). worth pointing herein turnover frequency (TOF) previously lanthanum complex La[N(SiMe3)2]3.28 19%, 2.2 S2). exhibited so far ability up 21.0 kDa.28 laboratory, effort being devoted improving current well-defined structure examined collaboratively matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MS). 2, spectra clearly displays characteristic resonances ppm without any contamination, two broad peaks 4.34 2.10 ppm. Moreover, clear assignments suggest samples dominantly initiated iPrOH, Ph2CHOH, designed. representative spectrum S8 agreement ring-opened rather structure. MALDI-TOF confirm ends, consistent analyses S9–S11). ion peaks, major assigned BnO/H ends minor P(MBL-co-γBL)ROP copolymers S9). Notably, trace P(MBL-co-γBL) confirmed S12), ascribed small impurity existing purchased reagent S13). Stacked (1) (2) (3) (4) measured DMSO-d6 (the residual peak marked *). Thermal properties postfunctionalization thermogravimetric analysis (TGA) differential scanning calorimetry (DSC) analyses. S14 compares TGA DTG curves sample Information). Both displayed multistep degradation profile, report.28 5% loss (Td, 5%) improved 229 261 kg mol−1. both maximum rate max) near 340 one-step profile Td,5% 338 Td,max 406 subjected DSC analyses, related summarized S3. semicrystalline there melting transitions °C/min slow crystallization 3). All Tg range −42 −46 rate. Tcc Tm 20.8 27.9 39.0 44.1 °C, respectively, increased, Tg, Tcc, increased. second scans variable rates: °C/min. S1: 16; S2: 17; S3: 5; S4: 18. pendent functionalized UV-triggered cross-linking photo-catalyzed thiol–ene click before.28 thiol–Michael reaction. Benzyl mercaptan thiol react DMSO disappearance signals, spectrum, suggests complete thiolated P(MBL)ROP-SR 4). Overlay CDCl3 CTPB/U4) (residual Similar La Y metal-based catalysts, starting MBL. metal LaCl3, P(MBL)ROP,28 interest focuses mediated Initial attempts CTPB/U5 failed recycle P(MBL)VAP. pathway, substituents, ( S6). Quantitative clean 0.5 CTPB/U6 1/3 (0.01 equiv. repeating units) evidenced occurring optimize KOMe/U4); after h; original comparison Mechanistic considerations details regarding catalyst-mediated interactions urea, gives stacked 1/1, CTPB/U4/BnOH 1/1/1, 1/3/1, THF-d8 generate half protons S15) shift proton (d, e, g, h) upfield, reports.34,38 Upon BnO− downfield methylene resonance 4.55 4.65 broadening hydroxyl (c) signal S16). reduced deshielding upfield 4.62 interactions, 1/3/1 case 1/1/1. comparison, CTPB/U1/BnOH 1/1/1 shifted 4.81 S17), suggesting anion. surprising if cons

Язык: Английский

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Functionalizable and Chemically Recyclable Thermoplastics from Chemoselective Ring‐Opening Polymerization of Bio‐renewable Bifunctional α‐Methylene‐δ‐valerolactone

Angewandte Chemie International Edition, Год журнала: 2022, Номер 61(32)

Опубликована: Июнь 8, 2022

It is a highly attractive strategy to develop chemically recyclable polymers establish circular plastic economy. Despite the recent advancements, still face challenges including high energy cost for polymer preparation or recycling, poor monomer recovery selectivity and efficiency as well undesired material performance. In this contribution, we present chemoselective controlled ring-opening polymerization of bio-renewable bifunctional α-methylene-δ-valerolactone (MVL) produce exclusive functionalizable polyester using strong base/urea binary catalysts. The obtained with molar mass exhibits good tensile strength comparable that some commodity plastics. Remarkably, can be depolymerized recover pristine 96 % yield by thermolysis, thus successfully establishing closed-loop life cycle.

Язык: Английский

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Ionic H-bonding organocatalysts for the ring-opening polymerization of cyclic esters and cyclic carbonates

Progress in Polymer Science, Год журнала: 2021, Номер 125, С. 101484 - 101484

Опубликована: Ноя. 10, 2021

Язык: Английский

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Chemically Recyclable Thermoplastic Polyurethane Elastomers via a Cascade Ring-Opening and Step-Growth Polymerization Strategy from Bio-renewable δ-Caprolactone

Macromolecules, Год журнала: 2022, Номер 55(10), С. 3860 - 3868

Опубликована: Май 12, 2022

It is highly desirable to develop chemically recyclable polymers address the challenge in establishing a sustainable circular polymer economy. Despite mass production and widespread applications, there are limited reported examples for polyurethanes capable of chemical recycling monomers with high efficiency purity. In this contribution, we report "living"/controlled ring-opening polymerization (ROP) bio-renewable δ-caprolactone (δCL) at room temperature bulk using an organobase combination urea as catalyst. The telechelic PδCL diol precursor well-defined terminal groups can be prepared catalyst loading low 0.05 mol %. A one-pot strategy by cascade ROP δCL step-growth precursors diisocyanate under solvent-free conditions produced thermoplastic polyurethane elastomers excellent elastic recovery, tensile strength, ultimate elongation, residue strain. Remarkably, recycled recover purity yield (∼99%) simple thermolysis.

Язык: Английский

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Synthetic pressure sensitive adhesives for biomedical applications

Progress in Polymer Science, Год журнала: 2023, Номер 142, С. 101692 - 101692

Опубликована: Май 4, 2023

Язык: Английский

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Ring-Opening Polymerization of Cyclic Esters and Carbonates with (Thio)urea/Cyclopropenimine Organocatalytic Systems

ACS Macro Letters, Год журнала: 2024, Номер unknown, С. 181 - 188

Опубликована: Янв. 22, 2024

Organocatalyzed ring-opening polymerization is a powerful tool for the synthesis of variety functional, readily degradable polyesters and polycarbonates. We report use (thio)ureas in combination with cyclopropenimine bases as unique catalyst cyclic esters carbonates large span reactivities. Methodologies exceptionally effective selective cocatalyst combinations were devised to produce polycarbonates narrow dispersities (Đ = 1.01–1.10). Correlations pKa various ureas revealed critical importance matching two cocatalysts achieve most efficient conditions. It was found that promoting strong H-bonding interactions noncompetitive organic solvent, such CH2Cl2, enabled greatly increased rates. The stereoselective rac-lactide afforded stereoblock poly(lactides) crystallize stereocomplexes, confirmed by wide-angle X-ray scattering.

Язык: Английский

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