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International audience; The diaminophenolate and β-diketiminate zinc complexes [(NNO)ZnEt] ((NNO)− = 2,4-di-tert-butyl-6-{[(2′-dimethylaminoethyl)-methylamino]methyl}phenolate)) and [(BDIiPr)Zn{N(SiMe3)2}] (BDIiPr = CH(CMeNC6H3-2,6-iPr2)2), respectively, the Lewis acidic triflate salt Al(OTf)3, and the guanidine TBD (= 1,5,7-triazabicyclo[4.4.0]dec-5-ene), combined to a protic source as initiator, typically benzyl alcohol (BnOH), enabled the successful copolymerization of ethylene carbonate (EC) with various cyclic esters such as β-butyrolactone (BL), δ-valerolactone (VL), ε-caprolactone (CL) or L-lactide (LLA). The random copolymerizations proceeded smoothly under mild operating conditions, preferentially from [(NNO)ZnEt]/BnOH at 60 °C in toluene within a few hours, affording the corresponding copolymers void of ether units, with Mn,SEC values in the range ca. 6000–93 350 g mol−1 and with unimodal, moderately broad dispersity values (ĐM = 1.3–2.1). Under the same experimental conditions, the homopolymerization of EC did not proceed. The first EC/BL random copolymers were thus synthesized with up to 26 mol% of EC inserted within the polyester, while the second example of P(EC-co-VL) was isolated. P(EC-co-VL), P(EC-co-CL), and P(EC-co-LLA) copolymers were prepared with higher than previously reported EC content, namely 23, 37, and 17 mol% vs. 10, 31, and 4 mol%, respectively. In contrast to other catalyst systems, the Al(OTf)3/BnOH system promoted CO2 elimination from the copolymers, thereby leading to ether defects. Microstructural analysis of the copolymers by 13C{1H} NMR spectroscopy revealed the presence of signals previously never described and possibly arising from consecutive EC units within the random copolymers. Thermal transition temperatures measured by DSC further supported the random nature of these copolymers.

α,ω-Dihydroxy-telechelic poly(trimethylenecarbonate), HO-PTMC-OH, is synthesized from the controlled "immortal" ring-opening polymerization (ROP) of trimethylene carbonate under mild conditions (bulk, 60 °C), using ZnEt(2) or, more efficiently, [(BDI)Zn(N(SiMe(3) )(2) )] (BDI = CH(CMeNC(6) H(3) -2,6-iPr(2) )(2) ) as catalyst precursor, in the presence of a diol HO-R-OH (R = (CH(2) )(2) or CH(2) C(6) H(4) CH(2) ; 0.5-10 equiv. vs Zn) acting both as co-initiator and chain transfer agent. Alternatively, HO-PTMC-OH is prepared upon hydrogenolysis of HO-PTMC-OCH(2) Ph, initially prepared from the ROP of TMC using the [(BDI)Zn(N(SiMe(3) )(2) )]/PhCH(2) OH system, under smooth operating conditions using Pd/charcoal. Well-defined dihydroxy-functionalized PTMCs of molar mass ranging from $\overline M _{\rm n}$ = 2 000 to 109 500 g · mol(-1) were thus quantitatively obtained and fully characterized by NMR, MALDI-TOF-MS and SEC analyses. The versatility of this "immortal" ROP allows the preparation of alike α,ω-functional polyester such as linear HO-poly(lactide)-OH, as well as star polymers such as the glycerol-based PTM-OH(3) .

The ring-opening polymerization (ROP) of trimethylene carbonate (TMC) was evaluated in bulk at 60―110°C using various catalyst systems based on bio-friendly metals, including the metal bis(trimethylsilylamides) Mg[N(SiMe 3 ) 2 ] 2 , Ca[N-(SiMe 3 ) 2 ] 2 (THF) 2 , Y[N(SiMe 3 ) 2 ] 3 , (BDI)Fe[N-(SiMe 3 ) 2 ] [BDI=CH(CMeNC 6 H 3 -2,6-i-Pr 2 ) 2 ], Fe[N-(SiMe 3 ) 2 ] 2 , Fe[N(SiMe 3 ) 2 ] 3 , Zn[N(SiMe 3 ) 2 ] 2 , (BDI)Zn[N(SiMe 3 ) 2 ] and ZnEt 2 , associated with an alcohol such as isopropyl or benzyl alcohol. The actual metal alkoxide initiating species has been formed in situ prior to the addition of TMC. Introduction of the alcohol component in excess leads to the "immortal" ring-opening polymerization (ROP) of TMC. According to such an "immortal" ROP process of TMC, whichever the metal species, as many as 200 polycarbonate chains could be successfully grown from a unique metal center in a well controlled ROP process. The best performances were obtained using the discrete (BDI)Zn[N(SiMe 3 ) 2 ] precursor. Under optimized conditions, as many as 50,000 equivalents of TMC could be fully converted from as little as 20 ppm of this metallic precursor, allowing the preparation of a polytrimethylene carbonate (PTMC) with a molar mass as high as 185,200 g mol ―1 with a relatively narrow molar mass distribution (M w /M n = 1.68). A double monomer feed experiment carried out with the (BDI)Zn[N-(SiMe 3 ) 2 ]/BnOH initiating system proved the "living" character of the polymerization. Characterization of the PTMCs by NMR and size exclusion chromatography (SEC) showed well-defined α-hydroxy-ω-alkoxycarbonate telechelic polymers, highlighting the controlled character of this "living and immortal" ROP process. Using the (BDI)Zn[N-(SiMe 3 ) 2 ] precursor, varying the alcohol (ROH) to 2-butanol, 3-buten-2-ol or 4-(trifluoromethyl)benzyl alcohol, revealed the versatility of this approach, allowing the preparation of accordingly end-functionalized HO-PTMC-OR polymers. The very low initial loading of metal catalyst considerably limits the potential toxicity and thus allows such polycarbonates to be used in the biomedical field.

International audience; The ring-opening polymerization (ROP) of racemic trans-cyclohexene carbonate (rac-CHC) and enantiopure trans-(R,R)-CHC is successfully carried out with various catalyst systems. Poly(cyclohexene carbonate) (PCHC) with a slight isotactic bias (Pm = ca. 60–76%) is obtained by ROP of rac-CHC catalyzed by zinc diaminophenolate, zinc β-diketiminate, yttrium bis(phenolate), or 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in combination with an alcohol as a co-initiator. Purely isotactic PCHC is synthesized for the first time via ROP of enantiopure (R,R)-CHC with a zinc/benzyl alcohol catalyst system. All reactions proceed without decarboxylation, affording well-defined PCHCs with Mn,NMR up to 17 000 g mol–1 and ĐM = ca. 1.2. Purely isotactic PCHC is semicrystalline, with Tg = 130 °C, Tc = 162 °C, and Tm = 248 °C. DFT computations further highlight the significant favorable impact of the trans-cyclohexane ring-strain to enable the ROP of CHC, as opposed to meso-CHC which is unreactive.

International audience; Linear trimethylene carbonate (1,3-dioxane-2-one, TMC) thermoplastic copolymers derived from glycerol have been synthesized upon sequential copolymerization. The “immortal” ring-opening polymerization (iROP) of the benzyloxy-substituted TMC, 3-benzyloxytrimethylene carbonate (BTMC), with systems composed of the β-diketiminate discrete zinc complex [(BDIiPr)Zn(N(SiMe3)2)] or the phosphazene base 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) as a catalyst, and benzyl alcohol (BnOH) as an initiator/chain transfer agent is first described. Next, diblock and triblock copolycarbonates featuring a TMC segment along with one or two adjacent BTMC, or 2,2-dimethoxypropane-1,3-diol carbonate (TMC(OMe)2), or racemic β-butyrolactone (BL) chains have been prepared. The copolymerization under “immortal” operating conditions was carried out in bulk or toluene solution and promoted by [(BDIiPr)Zn(N(SiMe3)2)] as a catalyst, and either BnOH, 1,3-propanediol, or the poly(trimethylene carbonate) (PTMC) derived macro-ols, H-PTMC-OBn or H-PTMC-H, as an initiator/chain transfer agent. In particular, the PTMC-b-[poly(TMC(OMe)2)]1,2 couple of copolymers provide a basis for the assessment of thermal and mechanical property differentiation in close relationship with the co-monomers content. Unlike PTMC which is elastomeric and P(TMC(OMe)2) which is rather rigid and brittle much like semi-crystalline poly(L-lactide), the diblock and triblock copolymers show characteristics lying in between those of each homopolymer, without any significant influence of the topology. Thus PTMC/PTMC(OMe)2 block copolymers mechanically behave similarly to PTMC/PLLA block copolymers.

International audience; Copolymerization of L-LA and TMC has been achieved with binary systems, associating either a metal-based (pre)catalyst or an organocatalyst with benzyl alcohol (BnOH) acting as a co-initiator and a chain transfer agent. Kinetic monitoring indicated that copolymerizations mediated by the zinc-β-diketiminate system [(BDI)Zn{N(SiMe3)2}]/BnOH proceed by preferential consumption of L-LA first and then of TMC, in contrast to homopolymerizations of the individual monomers that progress roughly at the same rate. In striking contrast, systems based on metal triflates, M(OTf)3/BnOH (M = Al, Bi, Yb), copolymerize TMC faster than L-LA, as established for the first time, while these systems also homopolymerize the individual monomers at about the same rate. Eventually, the [(BDI)Zn{N(SiMe3)2}]/BnOH and M(OTf)3/BnOH systems produce P(LLA-grad-TMC) gradient copolymers featuring PLLA and PTMC blocks of significant length (ca. 10 units with Al-, Yb-; ca. 6 units with Zn-, Bi-based systems), as confirmed by 13C NMR analyses. On the other hand, copolymerizations mediated by the guanidine-based organocatalyst system TBD/BnOH (TBD = 1,5,7-triazabicyclo[4.4.0]dec-5-ene) gave P(LLA-ran-TMC) random copolymers. Optimal control of molar masses and dispersities, along with minimized transesterifications, is achieved with the zinc and ytterbium systems. While metal triflates induce partial decarboxylation of TMC units, the zinc and TBD systems are perfectly chemoselective. Kinetic and microstructural control in random copolymerization of L-LA and TMC can thus be achieved via catalytic tuning.

International audience; Poly(L-lactide) (PLLA) is often regarded as tough and brittle while poly(1,3-trimethylene carbonate) (PTMC) is rather considered as a rubbery polymer. In an effort to improve the mechanical properties - especially ductility - of PLLA and thus to widen its field of applications, PLLA-PTMC diblock and triblock copolymers were synthesized through the sequential copolymerization of both L-lactide (L-LA) and trimethylene carbonate (TMC) using several catalytic systems. This process can be effectively catalyzed by inherently different systems ranging from a simple basic organocatalyst such as an amine (i.e., 4-N,N-dimethylaminopyridine, DMAP) or a phosphazene (i.e., 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine, BEMP), a simple Lewis acidic metallic salt such as aluminum triflate, or a more sophisticated discrete metallo-organic complex derived from a biofriendly metal, namely the β-diiminate zinc complex [(BDIiPr)Zn(N(SiMe3)2)] (BDI = CH(CMeNC6H3-2,6-iPr2)2), [(BDIiPr)Zn(N(SiMe3)2)]. Well-defined diblock PLLA-b-PTMC, triblock PLLA-b-PTMC-b-PLLA and 3-arm star GLY(PTMC-b-PLLA)3 copolymers with controlled molecular features, i.e. controlled functional end-groups and molar masses, rather narrow dispersity values, were thus prepared. The thermo-mechanical properties of the resulting copolymers revealed that a minimal block size of the PTMC and of the PLLA segments within the copolymer of Mn,PTMC = ca. 10 000 g mol−1 and Mn,PLLA = ca. 23 000 g mol−1 enables significant improvement of the elongation at break (εb) of PLLA up to 328%, while maintaining the Young's modulus (E = 2781 MPa) close to that of PLLA (E = 3427 MPa).

International audience; A simple isocyanate-free method to synthesize poly(trimethylene carbonate hydroxy-urethane)s is described. The strategy first involves the synthesis of α,ω-di(cyclic carbonate) telechelic polycarbonate precursors upon ring-opening polymerization of trimethylene carbonate using a cyclic carbonate alcohol as chain transfer agent, followed by the ring-opening polyaddition of the terminal cyclic carbonate with a diamine. Such poly(carbonate-hydroxyurethane)s exhibit macromolecular carbonate segments of tunable length/molar mass.

International audience; Six-membered cyclic carbonates, namely trimethylene carbonate (TMC), 3,3-dimethoxytrimethylene carbonate (DMTMC) and 3-benzyloxytrimethylene carbonate (BTMC), undergo controlled "immortal" ring-opening polymerization (iROP) under mild conditions (bulk, 60-150 °C), by using organocatalysts, including an amine [4-N,N-dimethylaminopyridine (DMAP)], a guanidine [1,5,7-triazabicyclo-[4.4.0]dec-5-ene (TBD)], or a phosphazene [2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP)], in the presence of an alcohol [benzyl alcohol (BnOH), 1,3-propanediol (PPD), glycerol (GLY)] that acts as both a co-initiator and a chain-transfer agent. Remarkably, such organocatalysts remain highly active in the iROP of technical-grade, unpurified TMC. Under optimized conditions, as much as 100 000 equivalents of TMC were fully converted by as little as 10 ppm of BEMP with the simultaneous growth of as many as 200 polymer chains, allowing the preparation of high molar mass poly(trimethylene carbonate)s (up to 45 800 g mol−1). These catalyst systems enable among the highest activities (TOF=55 800 h−1) and productivities (TON=95 000) ever reported for the ROP of TMC.

International audience; The controlled "immortal" ring-opening polymerization of trimethylene carbonate (TMC) using a two-component catalyst system based on a metal Lewis acid, such as a metal triflate M(OTf)n(M=Ca, Sc, Zn, Al, Bi; OTf=CF3SO3−) or the metallic salt Fe(acac)3, (acac=acetylacetonate) and an alcohol (ROH) as co-initiator and chain-transfer agent, is carried out in bulk at 110-150 °C. As a result of the water-tolerance of these systems, experimental operating conditions do not require any special care. The approach, valorized both with various ROH transfer agents and with either purified or unpurified monomer sources, is highly versatile. Functional telechelic polycarbonates H[BOND]PTMC[BOND]OR, devoid of decarboxylation sequences, are obtained [PTMC=poly(trimethylene carbonate)]. The molar mass of the PTMCs can be readily predicted by a simple model, taking into account the [TMC]0/[ROH]0 ratio and the amount of transferring impurities present in the raw/unpurified reagents. Such simple, air- and moisture-robust catalytic systems, which display quite high activities (TOF up to 28 200 h−1) and productivities (TON up to 45 000) are thus extremely valuable, especially industrially. The performances of these systems are described in comparison to the previously established valuable inorganic and organometallic catalytic systems, namely metal amido complexes ([M{N(SiMe3)2}3]) and [(BDI)Zn{N(SiMe3)2}] (BDI=β-diiminate ligand) derivatives.

International audience; This Perspective article summarizes efforts paid in our group to develop efficient metal-based catalysts for the immortal ring-opening polymerization (iROP) of cyclic esters in the presence of large amounts of alcohols (ROH) as chain transfer agents. The catalyst systems reviewed include discrete organometallic complexes based on rare earths, magnesium, calcium and more specifically zinc, as well as simple systems employing metal triflate salts, notably Al(OTf)3, for the (stereo)controlled iROP of lactide (LA), β-butyrolactone (BBL) and trimethylenecarbonate (TMC). Special emphasis is given to systems that allow the use of minute amounts of metal catalysts and large loadings of both monomer and alcohol for the rapid and productive formation of functional polyesters (H-Pol-OR) with controlled molecular features.

International audience; Functionalized polycarbonates derived from 2,2-dimethoxytrimethylene carbonate (TMC(OMe)2) have been prepared with controlled molecular features by immortal ring-opening polymerization , under mild conditions (bulk, 60-90 °C), using various (metallo)organic/alcohol (diol ) binary catalyst systems: the β-diiminate zinc complex [(BDIiPr)Zn(N(SiMe3)2)] (BDI = CH(CMeNC6H3-2,6-iPr2)2), the aluminium triflate, or the organic bases 4-N,N-dimethylaminopyridine (DMAP), 1.5.7-triazabicyclo-[4.4.0]dec-5-ene (TBD) and 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP), as catalyst precursors, combined with benzyl alcohol or 1,3-propanediol acting both as a co-initiator and a chain transfer agent. For the first time, well-defined α-hydroxy-ω-alkoxyester and α,ω-dihydroxy telechelic acetal -functionalized homopolycarbonates were thus prepared with molar mass up to 70[thin space (1/6-em)]200 g mol−1. These polymers were characterized at the molecular (NMR , SEC ), thermal (DSC , TGA ) and mechanical levels, and compared to conventional PTMC. P(TMC(OMe)2) is a rigid and brittle polymer material (E = 3190 ± 70 MPa, εr = 9 ± 1%).

International audience; The "immortal" coordination-insertion ring-opening polymerization of benzyl malolactonate (MLABe) initiated by the two-component catalyst system based on the zinc amide precursor, (BDI)Zn[N(SiMe3)2] (BDI = β-diiminate ligand), and benzyl alcohol (BnOH) acting as a co-initiator and a chain transfer agent proceeds in bulk at 40 °C. Functional telechelic poly(β-benzyl malolactonate)s, H-PMLABe-OBn, are thus obtained. Sequential copolymerization with trimethylene carbonate (TMC) affords block copolymers, PTMC-b-PMLABe, which are alternatively prepared from the chemical coupling of the PMLABe-COOH and PTMC-OH homopolymers. Simultaneous copolymerization of both the lactone and the carbonate monomers offers the PTMC-co-PMLABe random copolymers. The (co)polymers have been characterized by NMR, FT-IR, SEC and DSC analyses. These represent the first examples of β-benzyl malolactonate/carbonate copolymers. More importantly, these (co)polymers could be synthesized free of metallic residues thereby making them suitable as biomedical and pharmaceutical biomaterials.