Catalytic Ring-opening Polymerization Research Articles

Highly chemoselective lipase from Candida sp. 99-125 catalyzed ring-opening polymerization for direct synthesis of thiol-terminated poly(ɛ-caprolactone)

Abstract Lipase from Candida sp. 99-125 catalyzed ring-opening polymerization of ɛ-caprolactone in the presence of 6-mercapto-1-hexanol was presented as a new metal-free approach for direct synthesis of well-defined thiol-terminated poly(ɛ-caprolactone). Remarkably, high chemoselectivity of lipase from Candida sp. 99-125 toward hydroxyl and thiol was exhibited and quantitative thiol fidelity over 90% was achieved. The tedious protecting/deprotecting steps for thiol and metal residue were avoided. The polymerizations with around 70% monomer conversion were conducted in bulk and toluene at relative low temperature of 40 °C. Number–average molecular weight of resulted polymers ranged from 3000 to 4700 Da by changing the feed ratio between monomer and initiator. The structures of obtained thiol-terminated poly(ɛ-caprolactone) were demonstrated by combining NMR and SEC analyses.

Effect of Poly(l-lactide-co-ε-caprolactone) Macromonomer Composition on the Properties of Hot-Melt Adhesives with High Biomass Contents

Recently, an approach was introduced for incorporating renewable biomass into existing commercial acrylic thermoplastic pressure-sensitive adhesive (PSA) polymers in the form of acrylated macromonomers (MM). This was achieved without sacrificing adhesive performance. Here a study is reviewed on the influence of N-hydroxyethyl acrylamide capped poly(l-lactide-co-e-caprolactone) MM composition on the properties of acrylic hot-melt adhesive. A series of MMs containing a broad range of lactic acid and caprolactone repeat units were synthesized using catalyzed ring-opening polymerization. These MMs were substituted for 2-ethylhexyl acrylate in a commercial formulation to generate adhesive polymers via solution polymerization. Results indicate that the properties and performance of adhesive polymers are strongly dependent on the lactide content in MMs. In general, increasing lactide relative to caprolactone increases polymer hardness enhancing cohesive strength, while reducing it softens the polymer. Optimal ad...

Theoretical and Experimental Approach to Accurately Predict the Complex Molecular Weight Distribution in the Polymerization of Strainless Cyclic Esters

Polyesters obtained by the catalytic ring-opening polymerization of macrolactones in many aspects resemble the properties of polyethylene. However, the molecular weight distribution is intrinsically different and equals the molecular weight distribution observed for a step-growth process even though macrolactone ring-opening polymerization follows a chain-growth mechanism. The concurrent occurrence of transesterification reactions leading to the formation of cyclic polymers is responsible for the deviation from the molecular weight distribution characteristic for chain-growth polymerization. To explain and extent on the theoretical principles forming the basis of this peculiar molecular weight distribution, in this work the cyclization process during the polymerization of the 17-membered macrolactone ambrettolide has been analyzed. Liquid chromatography under critical conditions has been applied to semiquantitatively analyze the fractions of cyclic and linear products. In addition, low molecular weight si...

A study on ZnO nanoparticles catalyzed ring opening polymerization of L-lactide

Facile synthesis of multifunctional organic/inorganic materials is gaining importance. Present study deals with single step synthesis of PLLA/ZnO nanocomposite by ZnO nanoparticles catalyzed ring opening polymerization of L-lactide. The PLLA/ZnO nanocomposites with different ZnO concentrations were prepared and characterized by FT-IR, XRD, TEM, SEM, DSC, TGA, GPC, 13C NMR and 1H NMR etc. Uniform dispersion of ZnO nanoparticles of size 2–10 nm was achieved without any surface modification of the nanoparticles. The results showed that the as-synthesized PLLA/ZnO nanocomposites possessed thermal properties different from PLLA/ZnO nanocomposites synthesized by other techniques. The synthesized nanocomposite also showed excellent photochemical properties which were analyzed by studying decomposition of methylene blue dye.

Room temperature polymerization of norbornene with a hydride-bridged dinuclear ruthenium complex system

A two-component system, [Ru(p-cymene)Cl2]2 (C1)/BH3•NMe3, allows for the catalytic ring-opening metathesis polymerization (ROMP) of norbornene at 60°C. A hydride-bridged complex isolated from the two-component system, [RuCl(p-cymene)]2(μ-H)(μ-Cl) (C2), is also active in the ROMP reaction, albeit at a reduced rate. Abstraction of one chloride ligand from C2, by the reaction with 1equiv of either AgPF6 or AgSbF6, leads to the generation of either [{Ru(p-cymene)}2(μ-H)(μ-Cl)2]PF6 (C3) or [{Ru(p-cymene)}2(μ-H)(μ-Cl)2]SbF6 (C4) and further reduction of ROMP activity. Importantly, a reaction of C2 with 2equiv each of AgSbF6 and BH3•NMe3 provides the ability to achieve room temperature ROMP of norbornene. Various hydride-bridged dinuclear ruthenium complexes have been observed in the room temperature system based on 1H NMR analysis. An independent synthesis of a complex mixture containing [{Ru(p-cymene)}2(μ-H)3]PF6 (C5) and a single-component complex [{Ru(η6-C6Me6)}2(μ-H)3]PF6 (C6) rules out the catalytic capacity of this tri-μ-hydrido species. A di-μ-hydrido complex, [{Ru(p-cymene)}2(μ-H)2(μ-Cl)]PF6 (C7), is therefore postulated to act as the ROMP reaction center at room temperature.

Ring-opening polymerization by N-heterocyclic carbenes as catalysts: Characteristics and kinetics

In this work catalytic ring-opening polymerization of cyclic esters in THF in the presence of benzyl alcohol is described. The polymerization is catalyzed by 1,3-bis(4-methoxyphenyl)imidazolium carbene, N-heterocyclic carbene (NHC). The ability of two different monomers, ɛ-caprolactone and L-lactide, to enter into the polymerization via ring-opening polymerization with NHCs as catalysts was evaluated. The plot of ln([M]0/[M]t) versus reaction time yielded a straight line indicating that the kinetics of polymerization of ɛ-caprolactone and L-lactide was first-order in monomer concentration. Moreover, a direct relation between the rate of ring-opening polymerization of ɛ-caprolactone and the catalyst concentration suggested a first-order dependence of the rate of polymerization on the catalyst concentration.

ChemInform Abstract: Metrology as a Tool to Understand Immobilized Enzyme Catalyzed Ring‐Opening Polymerization.

ChemInformVolume 45, Issue 24 Reviews ChemInform Abstract: Metrology as a Tool to Understand Immobilized Enzyme Catalyzed Ring-Opening Polymerization. Matthew T. Hunley, Matthew T. Hunley Mater. Sci. Eng. Lab., Natl. Inst. Stand. Technol., Gaithersburg, MD 20899, USASearch for more papers by this authorSara V. Orski, Sara V. Orski Mater. Sci. Eng. Lab., Natl. Inst. Stand. Technol., Gaithersburg, MD 20899, USASearch for more papers by this authorKathryn L. Beers, Kathryn L. Beers Mater. Sci. Eng. Lab., Natl. Inst. Stand. Technol., Gaithersburg, MD 20899, USASearch for more papers by this author Matthew T. Hunley, Matthew T. Hunley Mater. Sci. Eng. Lab., Natl. Inst. Stand. Technol., Gaithersburg, MD 20899, USASearch for more papers by this authorSara V. Orski, Sara V. Orski Mater. Sci. Eng. Lab., Natl. Inst. Stand. Technol., Gaithersburg, MD 20899, USASearch for more papers by this authorKathryn L. Beers, Kathryn L. Beers Mater. Sci. Eng. Lab., Natl. Inst. Stand. Technol., Gaithersburg, MD 20899, USASearch for more papers by this author First published: 02 June 2014 https://doi.org/10.1002/chin.201424295AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume45, Issue24June 17, 2014 RelatedInformation

Group 4 Metal Complexes Bearing Thioetherphenolate Ligands. Coordination Chemistry and Ring-Opening Polymerization Catalysis

A series of group 4 metal complexes 1–4 (1 = (t-BuOS)2Ti(O-i-Pr)2; 2 = (t-BuOS)2Zr(O-t-Bu)2; 3 = (t-BuOS)2Hf(O-t-Bu)2; 4 = (CumOS)2Zr(O-t-Bu)2) supported by two phenolate bidentate ligands (t-BuOS–H = 4,6-di-tert-butyl-2-phenylsulfanylphenol and CumOS–H = 4,6-dicumyl-2-phenylsulfanylphenol) were synthesized by the reaction of appropriate metal tetra(alkoxide)s with 2 equiv of the ligands. The X-ray structure of 2 revealed that the two ligands were κ2-chelated to the metal center with two phenoxy groups in trans positions and the two thioether moieties in cis positions. VT NMR analysis revealed a fast inversion of configuration at the metal center. Complexes 1–4 promoted the ring-opening polymerization (ROP) of lactide and e-caprolactone. Complex 4 exhibited the highest activity with a pseudo-first-order rate constant of 0.061 ± 0.003 min–1 at 100 °C, which compares favorably with those reported for the most active group 4 complexes. Polymerizations were well-controlled, giving predictable molecular weight...

Synthesis of Linear, Cyclic, Figure-Eight-Shaped, and Tadpole-Shaped Amphiphilic Block Copolyethers via t-Bu-P4-Catalyzed Ring-Opening Polymerization of Hydrophilic and Hydrophobic Glycidyl Ethers

This paper describes the synthesis of systematic sets of figure-eight- and tadpole-shaped amphiphilic block copolyethers (BCPs) consisting of poly(decyl glycidyl ether) and poly[2-(2-(2-methoxyethoxy)ethoxy)ethyl glycidyl ether], together with the corresponding cyclic counterparts, via combination of the t-Bu-P4-catalyzed ring-opening polymerization (ROP) and click cyclization. The clickable linear BCP precursors, with precisely controlled azido and ethynyl group placements as well as a fixed molecular weight and monomer composition (degree of polymerization for each block was adjusted to be around 50), were prepared by the t-Bu-P4-catalyzed ROP with the aid of functional initiators and terminators. The click cyclization of the precursors under highly diluted conditions produced a series of cyclic, figure-eight-, and tadpole-shaped BCPs with narrow molecular weight distributions of less than 1.06. Preliminary studies of the BCPs self-assembly in water revealed the significant variation in their cloud poin...

Methods for Synthesizing the Macromolecular Constituents of Smart Nanosized Carriers for Controlled Drug Delivery

Smart multifunctional polymeric nanocarriers able to respond to physicochemical changes in their environment or to external stimuli represent a new paradigm in the field of pharmaceutical formulations for controlled drug delivery. The introductory part of the present review deals with this new concept and presents the main advantages resulting from the use of such nanovehicles instead of conventional, much larger drug delivery systems. The access to drug nanocarriers based on smart supramolecular polymeric materials is primarily limited by the available polymerization methods capable to produce polymers with low polydispersity index, as well as much more complex macromolecular architectures with strictly controlled chemical composition, such as block copolymers and star or graft polymers or copolymers. This article reviews the state-of-the art in controlled/"living" free radical polymerization techniques as well as ring opening polymerization methods. Nitroxide mediated free radical polymerization (NMP), atom transfer radical polymerization (ATRP), reversible addition-fragmentation chain-transfer polymerization (RAFT), single electron transfer-living radical polymerization (SET-LRP), single electron transfer-nitroxide radical coupling reaction (SET-NRC), cationic ring opening polymerization (CROP), anionic ring opening polymerization (AROP), and metal catalyzed ring opening polymerization are described, highlighting their mechanistic details and their synthetic potential as well as their limitations. The final part of the article is dedicated to a special type of unimolecular, monodisperse nanocarriers - the dendrimers. Both divergent and convergent approaches to dendrimer synthesis are described along with the therapeutic applications taking advantage of the unique branched tree-like globular structure of dendrimers to treat cancer.

A green route to synthesize poly(lactic acid)-based macromonomers in scCO2 for biodegradable nanoparticle production

Poly(lactic acid)-based macromonomers, aimed at biomedical applications and with well-defined average chain length, are produced through catalytic ring-opening polymerization of L,L-lactide co-initiated by a co-monomer bearing a double bond. Reactions have been carried out in supercritical carbon dioxide (scCO2) at different temperatures, ranging from 90 to 130 °C. The resulting oligomers have been characterized by different techniques (1H-NMR, 13CNMR, MALDI-TOF, ESI, GPC, FT-IR, TGA), which show that oligomers with narrower molecular weight distribution are produced at the lowest temperature. In addition, a significant reduction of the impact of the secondary reactions has been found at this same temperature (90 °C), leading to a crude product with enhanced purity. Finally, the synthesized macromonomers have been used to produce NPs whose degradation behaviour has been investigated. An improved control of the degradation rate is observed for the NPs synthesized using the macromonomer produced in scCO2 at 90 °C.

Redox-Responsive Block Copolymers: Poly(vinylferrocene)-b-poly(lactide) Diblock and Miktoarm Star Polymers and Their Behavior in Solution

The synthesis of diblock and miktoarm star polymers containing poly(vinylferrocene) (PVFc) and poly(l-lactide) (PLA) blocks is introduced. End functionalization of PVFc was carried out via end capping of living carbanionic PVFc chains with benzyl glycidyl ether (BGE). By hydrogenolysis of the benzyl protecting group a dihydroxyl end-functionalized PVFc was obtained. Both monohydroxyl- and dihydroxyl-functionalized PVFcs have been utilized as macroinitiators for the subsequent polymerization of l-lactide via catalytic ring-opening polymerization. A series of block copolymers and AB2 miktoarm star polymers was synthesized with varied PLA chain lengths. All polymers were characterized in detail, using 1H NMR spectroscopy, size exclusion chromatography (SEC), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF). The molecular weight of the block copolymers and AB2 miktoarm star polymers are in the range of 8000–15000, containing a PVFc block of weight 7800. In addition, the self-assembly behavior of the polymers in dichloromethane (CH2Cl2) was investigated by using dynamic light scattering (DLS) and transmission electron microscopy (TEM). In a selective solvent for PLA the block copolymers and miktoarm star polymers formed vesicle-like structures with different diameters.

Thermodynamics and kinetics of Novozym 435 catalyzed ring-opening polymerization of 1,4-dioxan-2-one

Abstract In this paper thermodynamics and kinetics of bulk ring-opening polymerization (ROP) of 1,4-dioxan-2-one (PDO) catalyzed by Novozym 435 were investigated. Results showed that the polymerization reached equilibrium after 12 h at 60 °C in the presence of 5 wt% Novozym 435 (based on PDO). The calculated thermodynamic parameters, enthalpy and standard entropy of the polymerization, are −19 kJ mol−1 and −66 J K−1 mol−1, respectively. The kinetic plot of ln{([M]0 − [M]e)/([M]t − [M]e)} vs time is linear, indicating that the polymerization is first order with respect to the monomer concentration. The calculated apparent activation energy (Eapp) is 45.3 kJ mol−1, which is lower than that using Sn(Oct)2 and La(OiPr)3 as catalysts. According to 1H NMR and GPC analysis, the ROP of PDO with Novozym 435 catalyzed follows monomer activated mechanism.

Mild and Efficient Preparation of Block and Gradient Copolymers by Methanesulfonic Acid Catalyzed Ring-Opening Polymerization of Caprolactone and Trimethylene Carbonate

Polycaprolactone/polytrimethylene carbonate copolymers of different microstructures have been prepared in toluene solution under mild conditions by controlled ring-opening polymerization of ε-caprolactone and trimethylene carbonate with methanesulfonic acid as catalyst. Sequential addition of the monomers led to the formation of well-defined di- and tri-block copolymers, demonstrating the ability of the catalytic system to cross-propagate. Simultaneous copolymerization yielded gradient copolymers as a result of the different copolymerization reactivity ratios and absence of undesirable redistribution reactions. DSC analyses showed a noticeable impact of the copolymer microstructure on the thermal properties.

Kinetic Investigation on the Catalytic Ring-Opening (Co)Polymerization of (Macro)Lactones Using Aluminum Salen Catalysts

The kinetic behavior of the catalytic ring-opening polymerization (cROP) of a range of macrolactones, including ω-pentadecalaconte (PDL), ambrettolide (Amb), and butylene adipate (BA), and small-ring lactones, including l-lactide (LLA), e-caprolactone (e-CL), e-decalactone (e-DL), and β-butyrolactone (B-BL), using various aluminum salen complexes was investigated. The cROP rates were shown to be first order both in catalyst and in monomer. The activation energies of the polymerization of PDL and LLA in combination with aluminum salen complexes, with and without tert-butyl groups, were determined, showing that the increase in steric hindrance is negatively affecting the polymerization rate of LLA more than of PDL. Interestingly, an increase of the salen diimine bridge from ethylene to 2,2-dimethyl propylene leads to a dramatic increase in rate for the polymerization of small-ring lactones, while it leaves the rate of polymerization of macrolactones practically unchanged. In order to exploit this difference...

Aluminum complexes of bidentate phenoxy-amine ligands: Synthesis, characterization and catalysis in ring-opening polymerization of cyclic esters

A series of aluminum complexes 1a–5a bearing bidentate phenoxy-amine ligands were synthesized and characterized by NMR spectroscopy and elemental analyzes. The variation of the ortho-substituent of phenoxy moiety and the amino group of the ancillary ligands has crucial influence on the stoichiometric structure of the obtained aluminum complexes. Reaction of 2-(N-benzyl-N-R3-aminomethyl)-4-R2-6-R1-phenols (R1 = tBu, R2 = Me, R3 = ethyl, 1; R1 = R2 = cumyl, R3 = ethyl, 2; R1 = R2 = cumyl, R3 = tBu, 3) with either one or half equivalent of AlMe3 exclusively afforded monoligated complexes LBu,EtAlMe2 (1a), LCumyl,EtAlMe2 (2a) and LCumyl,BuAlMe2 (3a), whereas the treatment of 2-(N-benzyl-N-R3-aminomethyl)-4,6-dichlorophenols (R3 = ethyl, 4; R3 = tBu, 5) with 0.5 equivalent of AlMe3 resulted in the formation of (LCl,Et)2AlMe (4a) or (LCl,Bu)2AlMe(HLCl,Bu) (5a) respectively. All of these aluminum methyl complexes can efficiently polymerize rac-lactide to atactic polymers and actively initiate the ring-opening polymerization of ɛ-caprolactone.

Discrete Divalent Rare‐Earth Cationic ROP Catalysts: Ligand‐Dependent Redox Behavior and Discrepancies with Alkaline‐Earth Analogues in a Ligand‐Assisted Activated Monomer Mechanism

The first solvent-free cationic complexes of the divalent rare-earth metals, [{RO}RE(II) ](+) [A](-) (RE(II) =Yb(II) , 1; Eu(II) , 2) and [{LO}RE(II) ](+) [A](-) ([A](-) =[H2 N{B(C6 F5 )3 }2 ](-) ; RE(II) =Yb(II) , 3; Eu(II) , 4), have been prepared by using highly chelating monoanionic aminoether-fluoroalkoxide ({RO}(-) ) and aminoether-phenolate ({LO}(-) ) ligands. Complexes 1 and 2 are structurally related to their alkaline-earth analogues [{RO}AE](+) [A](-) (AE=Ca, 5; Sr, 6). Yet, the two families behave very differently during catalysis of the ring-opening polymerization (ROP) of L-lactide (L-LA) and trimethylene carbonate (TMC) performed under immortal conditions with excess BnOH as an exogenous chain-transfer agent. The ligand was found to strongly influence the behavior of the RE(II) complexes during ROP catalysis. The fluoroalkoxide RE(II) catalysts 1 and 2 are not oxidized under ROP conditions, and compare very favorably with their Ca and Sr congeners 5 and 6 in terms of activity (turnover frequency (TOF) in the range 200-400 molL-LA (molEu h(-1) )) and control over the parameters during the immortal ROP of L-LA (Mn,theor ≈Mn,SEC , Mw /Mn <1.05). The Eu(II) -phenolate 4 provided one of the most effective ROP cationic systems known to date for L-LA polymerization, exhibiting high activity (TOF up to 1 880 molL-LA ⋅(molEu h)(-1) ) and good control (Mw /Mn =1.05). By contrast, upon addition of L-LA the Yb(II) -phenolate 3 immediately oxidizes to inactive RE(III) species. Yet, the cyclic carbonate TMC was rapidly polymerized by combinations of 3 (or even 1) and BnOH, revealing excellent activities (TOF=5000-7000 molTMC ⋅(molEu h)(-1) ) and unusually high control (Mn,theor ≈Mn,SEC , Mw /Mn <1.09); under identical conditions, the calcium derivative 5 was entirely inert toward TMC. Based on experimental and kinetic data, a new ligand-assisted activated monomer ROP mechanism is suggested, in which the so-called ancillary ligand plays a crucial role in the catalytic cycle. A coherent reaction pathway computed by DFT, compatible with the experimental data, supports the proposed scenario.

Aluminum Complexes of Tridentate Amine Biphenolate Ligands Containing Distinct N‐alkyls: Synthesis and Catalytic Ring‐opening Polymerization

AbstractA series of aluminum complexes of amine biphenolate ligands that contain distinct N‐alkyl substituents have been prepared and employed for ring‐opening polymerization (ROP) of ϵ‐caprolactone (ϵ‐CL). Alkane elimination of trimethylaluminum with H2[R‐ONO] ([R‐ONO]2− = [RN(CH2‐2‐O‐3,5‐C6H2(tBu)2)2]2−; R = tBu (1a), iPr (1b), nPr (1c)) in toluene solutions at 25 °C produces colorless crystalline [R‐ONO]AlMe (2a‐c). X‐ray diffraction studies of these organoaluminum complexes showed them to be four‐coordinate species having a distorted tetrahedral coordination core. In the presence of benzyl alcohol, complexes 2a‐c are all active catalyst precursors for ROP of ϵ‐CL. The ROP rates of ϵ‐CL are clearly a function of the steric sizes of the N‐alkyl substituents, following an increasing order 2a &lt; 2b &lt; 2c. Interestingly, both 2b and 2c exhibit controlled ROP catalysis whereas 2a gives low molecular weight oligomers under identical conditions. In ROP catalyzed with 2b or 2c, the ϵ‐CL disappearance rates follow pseudofirst order kinetics, with the latter being about 2.86(2) times faster than the former. Complex 2b outperforms 2c in view of maintaining controlled ROP catalysis in reactions with extremely high monomerto‐catalyst ratios. The complex constitution‐reactivity relationship is discussed.

One-pot synthesis of poly(norbornene)-block-poly(lactide) copolymers using a bifunctional initiator

Block copolymers of poly(norbornene) and poly(lactide) were synthesized in one-pot using a bifunctional initiator bearing a ruthenium complex for the Ring-Opening Metathesis Polymerization (ROMP) of norbornenes and an alcohol to initiate the 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) catalyzed Ring-Opening Polymerization (ROP) of L-lactide.

Synthesis, characterization and reactivity of single-site aluminium amides bearing benzotriazole phenoxide ligands: catalysis for ring-opening polymerization of lactide and carbon dioxide/propylene oxide coupling

New aluminium complexes containing bis-BTP ligands (BTP = N,O-bidentate benzotriazole phenoxide) were synthesized and structurally characterized. Amine elimination of Al(NMe2)3 with (R)BTP-H ligands ((CMe2Ph)BTP-H = 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, (t-Bu)BTP-H = 2-(2H-benzotriazol-2-yl)-4,6-di-tert-butylphenol and (TMCl)BTP-H = 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol) (2.0 mol equiv.) in toluene or hexane afforded the penta-coordinated single-site amidoaluminium complexes [((R)BTP)2Al(NMe2)] (R = CMe2Ph for 1; R = t-Bu for 2; R = TMCl for 3) in satisfactory yields. With the addition of H2O (0.5 molar equiv.), the hydrolysis of Al amides 2 and 3 in a mixed solvent of THF/toluene at 25 °C produced oxo-bridged bimetallic aluminium complexes [{((R)BTP)2Al}2(μ-O)] (R = t-Bu for 4 and R = TMCl for 5) in ≥70% yield. According to single crystal X-ray diffraction studies, complex 2 shows a monomeric Al(iii) amide with bis((t-Bu)BTP) ligands and one -NMe2 group, whereas alumoxane 4 is a dinuclear species, in which the bonding mode of the Al-O-Al moiety from μ2-oxo assumes a linear type. Catalysis for ring-opening polymerization of lactide (LA) and CO2/propylene oxide (PO) coupling was systematically studied. Single-site Al amide 3 is an efficient initiator for LA polymerizations with a living character; the polymerization displays a first-order dependence on the concentration of l-LA. Bimetallic BTP-ligated alumoxane 5 is an active catalyst (TOF: 120 h(-1)) for the coupling of CO2 with PO in the presence of n-Bu4NBr to give propylene carbonate under mild conditions.