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1.
Reile M. Slattery Amanda E. Stahl Kelsey R. Brereton Arnold L. Rheingold David B. Green Joseph M. Fritsch 《Journal of polymer science. Part A, Polymer chemistry》2019,57(1):48-59
Seven magnesium complexes ( 1–7 ) were synthesized by reaction of new ( L 3 ‐H – L 5 ‐H ) and previously reported ketoimine pro‐ligands with dibutyl magnesium and were isolated in 59–70% yields. Complexes 1–7 were characterized fully and consisted of bis‐ligated homoleptic ketoiminates coordinated in distorted octahedral geometry around the magnesium centers. The complexes were investigated for their ability to initiate the ring opening polymerization (ROP) of l ‐lactide (L‐LA) to poly‐lactic acid (PLA) and ?‐caprolactone (?CL) to poly‐caprolactone in the presence of 4‐fluorophenol co‐catalyst. For L‐LA polymerization, complexes containing ligand electron‐donating groups ( 1–5 ) achieved >90% conversion in 2 h at 100 °C, while the presence of CF3 groups in 6 and 7 slowed or resulted in no PLA detected. With ?CL, ROP initiated with 1–7 resulted in lower percentage conversion with similar electronic effects. Moderate molecular weight PLA polymeric material (14.3–21.3 kDa) with low polydispersity index values (1.23–1.56) was obtained, and ROP appeared to be living in nature. Copolymerization of L‐LA and ?CL yielded block copolymers only from the sequential polymerization of ?CL followed by L‐LA and not the reverse sequence of monomers or the simultaneous presence of both monomers. Polymers and copolymers were characterized with NMR, gel permeation chromatography, and differential scanning calorimetry. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 48–59 相似文献
2.
Controlled ring‐opening polymerization of l‐lactide and ε‐caprolactone catalyzed by aluminum‐based Lewis pairs or Lewis acid alone
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Yuushou Nakayama Shunsuke Kosaka Kentaro Yamaguchi Gentaro Yamazaki Ryo Tanaka Takeshi Shiono 《Journal of polymer science. Part A, Polymer chemistry》2017,55(2):297-303
Ring‐opening polymerization of cyclic esters was studied using catalysts composed of bulky Lewis acids (LA) and Lewis bases (LB). Controlled polymerization of l ‐lactide (l ‐Lac) was proceeded by Al(C6F5)3·THF in combination with trimesitylphosphine (Mes3P) or triphenylphosphine (Ph3P) using BnOH as an initiator to produce poly(l ‐Lac) with narrow molecular weight distribution (MWD; Mw/Mn = 1.1). Both the LA and the LB were indispensable to promote the polymerization. The molecular weights of the resulting poly(l ‐Lac)s were controlled by the feed monomer to initiator ratio. ε‐Caprolactone (CL) was rapidly polymerized by Al(C6F5)3·THF with or without Mes3P, although the resulting polymer had rather broad MWD (Mw/Mn = 1.7). The CL polymerization by Al(C6F5)3·THF alone at r.t. gave poly(CL) with relatively narrow MWD (Mw/Mn = 1.2). © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 297–303 相似文献
3.
Deivasagayam Dakshinamoorthy Frédéric Peruch 《Journal of polymer science. Part A, Polymer chemistry》2011,49(24):5176-5185
Several titanium complexes based on aminodiol ligands were tested as initiators for the ring‐opening polymerization (ROP) of ε‐caprolactone under solution and bulk conditions. All complexes were found to be efficient under both conditions. For bulk polymerization at 70 °C, high activities were observed (113.3–156.2 gpoly mmolcat?1 h?1) together with controlled molar mass distribution. Kinetic studies revealed controlled polymerization, and the chain propagation was first order with respect to monomer conversion. One complex was also tested for the ROP of rac‐β‐butyrolactone and the end‐group analysis suggested that ring opening occurs through acyl‐oxygen bond cleavage via coordination–insertion mechanism. The microstructure analysis of polymer by 13C NMR indicates atactic polymer. Another complex was also found to be efficient initiator for the ROP of trimethylene carbonate under solution and bulk conditions. Again, end‐group analysis suggests coordination–insertion mechanism. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
4.
《Journal of polymer science. Part A, Polymer chemistry》2018,56(6):611-617
The random copolymers poly(LA‐ran‐CL) have improved properties of degradability, mechanical strength, elasticity, and permeability over the PLA and PCL homopolymers. However, the synthesis of such copolymers is still a great challenge in polymer chemistry. In this contribution, we develop a simple but well‐designed phenoxyimine Al complex ( 4 ) with bulky Ph2CH groups, which achieves controlled random copolymerization of rac‐LA and ɛ‐CL in a living manner (Ð = 1.06–1.09). The reactivity ratios of rac‐LA and ɛ‐CL (rLA and rCL) are 1.09 and 1.05 and the average sequence lengths of the lactidyl unit (LLA) and the caproyl unit (LCL) are in the range of 1.9–2.0 at different stages of conversion. In marked contrast, Al complexes ( 1–3 ) having less bulky substituents on the ligands only produce gradient copolymers. Furthermore, this strategy of catalyst design would be readily extended to other catalytic systems including β‐ketiminato Al complex ( 5 ). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 611–617 相似文献
5.
Anna Finne Reema Ann‐Christine Albertsson 《Journal of polymer science. Part A, Polymer chemistry》2003,41(19):3074-3082
Three different, new germanium initiators were used for ring‐opening polymerization of L ‐lactide. Chlorobenzene and 120 °C was a usable polymerization system for solution polymerization, and the results from the polymerizations depended on the initiator structure and bulkiness around the insertion site. The average molecular weights as measured by size exclusion chromatography increased linearly with the monomer conversion, and the molecular weight dispersity was around 1.2 for initiators 1 and 2 , whereas it was around 1.4 for initiator 3 . The average molecular weight of poly(L ‐lactide) could be controlled with all three initiators by adding different ratios of monomer and initiator. The reaction rate for the solution polymerization was, however, overall extremely slow. With an initial monomer concentration of 1 M and a monomer‐to‐initiator ratio of 50, the conversion was 93% after 161 h for the fastest initiator. In bulk polymerization, 160 °C, the conversion was 90% after 10 h. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3074–3082, 2003 相似文献
6.
Daisuke Nagai Masaki Nishida Bungo Ochiai Koji Miyazaki Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2006,44(10):3233-3241
Pseudo block and triblock copolymers were synthesized by the cationic ring‐opening copolymerization of 1,5,7,11‐tetraoxaspiro[5.5]undecane (SOC1) with trimethylene oxide (OX) via one‐shot and two‐shot procedures, respectively. When SOC1 and OX were copolymerized cationically with boron trifluoride etherate (BF3OEt2) as an initiator in CH2Cl2 at 25 °C, OX was consumed faster than SOC1. SOC1 was polymerized from the OX‐rich gradient copolymer produced in the initial stage of the copolymerization to afford the corresponding pseudo block copolymer, poly [(OX‐grad‐SOC1)‐b‐SOC1]. We also succeeded in the synthesis of a pseudo triblock copolymer by the addition of OX during the course of the polymerization of SOC1 before its complete consumption, which provided the corresponding pseudo triblock copolymer, poly[SOC1‐b‐(OX‐grad‐SOC1)‐b‐SOC1]. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3233–3241, 2006 相似文献
7.
Hsuan‐Ying Chen Wei‐Yi Lu Yen‐Jen Chen Sodio C. N. Hsu Siou‐Wei Ou Wei‐Te Peng Nai‐Yuan Jheng Yi‐Chun Lai Bo‐Sheng Wu Hsuan Chung Yun Chen Ta‐Chou Huang 《Journal of polymer science. Part A, Polymer chemistry》2013,51(2):327-333
This study synthesized a series of titanium iminophenoxide complexes and investigated their suitability as catalysts for the ring‐opening polymerization of L ‐lactide (L ‐LA) and ε‐caprolactone (CL). Complexes with bidentate ligands demonstrate higher catalytic activity than their tridentate counterparts since the third coordination atom needs to contend with L ‐LA and CL. Differences in the geometric framework of bidentate ligands also influence the catalytic activity. Type II ligands (N, N‐trans form of Ti complex) prevent the coordination of monomers to Ti thereby decreasing the initiation rate. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
8.
Kosuke Makiguchi Seiya Kikuchi Toshifumi Satoh Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2013,51(11):2455-2463
The ring‐opening polymerization (ROP) of cyclic esters, such as ε‐caprolactone, 1,5‐dioxepan‐2‐one, and racemic lactide using the combination of 3‐phenyl‐1‐propanol as the initiator and triflimide (HNTf2) as the catalyst at room temperature with the [monomer]0/[initiator]0 ratio of 50/1 was investigated. The polymerizations homogeneously proceeded to afford poly(ε‐caprolactone) (PCL), poly(1,5‐dioxepan‐2‐one) (PDXO), and polylactide (PLA) with controlled molecular weights and narrow polydispersity indices. The molecular weight determined from an 1H NMR analysis (PCL, Mn,NMR = 5380; PDXO, Mn,NMR = 5820; PLA, Mn,NMR = 6490) showed good agreement with the calculated values. The 1H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry analyses strongly indicated that the obtained compounds were the desired polyesters. The kinetic measurements confirmed the controlled/living nature for the HNTf2‐catalyzed ROP of cyclic esters. A series of functional alcohols, such as propargyl alcohol, 6‐azido‐1‐hexanol, N‐(2‐hydroxyethyl)maleimide, 5‐hexen‐1‐ol, and 2‐hydroxyethyl methacrylate, successfully produced end‐functionalized polyesters. In addition, poly(ethylene glycol)‐block‐polyester, poly(δ‐valerolactone)‐block‐poly(ε‐caprolactone), and poly(ε‐caprolactone)‐block‐polylactide were synthesized using the HNTf2‐catalyzed ROP. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2455–2463 相似文献
9.
Jinbao Xu Junzhe Song Stergios Pispas Guangzhao Zhang 《Journal of polymer science. Part A, Polymer chemistry》2014,52(8):1185-1192
Ring‐opening polymerization (ROP) of ε‐caprolactone (CL) using salicylic acid (SAA) as the organocatalyst and benzyl alcohol as the initiator in bulk at 80 °C successfully proceeded to give a narrowly distributed poly(ε‐caprolactone) (PCL). In addition, 2‐hydroxyethyl methacrylate, propargyl alcohol, 6‐azido‐1‐hexanol, and methoxy poly(ethylene glycol) were also used as functional initiators. The 1H NMR, SEC, and MALDI‐TOF MS measurements of the PCL clearly indicate the presence of the initiator residue at the chain end, implying that the SAA‐catalyzed ROP of CL was through the activated monomer mechanism. The kinetic experiments confirmed the controlled/living nature of the SAA‐catalyzed ROP of CL. Furthermore, the block copolymerization of CL and δ‐valerolactone successfully proceeded to give poly(ε‐caprolactone)‐block‐poly(δ‐valerolactone). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1185–1192 相似文献
10.
Yueh‐Hsuan Tsai Chia‐Her Lin Chu‐Chieh Lin Bao‐Tsan Ko 《Journal of polymer science. Part A, Polymer chemistry》2009,47(19):4927-4936
A novel tridentate anilido‐aldimine ligand, [o‐C6H4(NHAr)? HC?NCH2CH2NMe2] (Ar = 2,6‐iPr2C6H3, L ‐H, 1 ), has been prepared by the condensation of N, N‐dimethylethylenediamine with one molar equivalent of 2‐fluoro‐benzaldehyde in hexane, followed by the addition of the lithium salt of diisopropylaniline in THF. Magnesium (Mg) and zinc (Zn) complexes supported by the tridentate anilido‐aldimine ligand have been synthesized and structurally characterized. Reaction of L ‐H ( 1 ) with an equivalent amount of MgnBu2 or ZnEt2 produces the monomeric complex [ L MgnBu] ( 2 ) or [ L ZnEt] ( 3 ), respectively. Experimental results show that complexes 2 and 3 are efficient catalysts for ring‐opening polymerization of ε‐caprolactone (CL) and L ‐lactide (LA) in the presence of benzyl alcohol and catalyze the polymerization of ε‐CL and L ‐LA in a controlled fashion yielding polymers with a narrow polydispersity index. In both polymerizations, the activity of Mg complex 2 is higher than that of Zn complex 3 , which is probably due to the higher Lewis acidity and better oxophilic nature of Mg2+ metal. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4927–4936, 2009 相似文献
11.
Antonella Silvestri Fabia Grisi Stefano Milione 《Journal of polymer science. Part A, Polymer chemistry》2010,48(16):3632-3639
The alcoholysis of the heteroscorpionate methyl aluminum complex (bpzmp)AlMe2 ( 1 ) (bpzmp = 2,4‐di‐tert‐butyl‐6‐(bis‐(3,5‐dimethylpyrazol‐1‐yl)methyl)phenoxo), promoted both by phenol and isopropanol, has been investigated. The reaction of 1 with phenol afforded the dimeric mono(phenoxo) derivative 2 , whereas the alcoholysis of 1 with the less acidic isopropanol involved the coordinated heteroscorpionate ligand and led to the tetrahedral complex 3 in which the aluminum atom is surrounded by one κ2‐N,O? coordinated bpzmp ligand and one η1‐O? coordinated ppzmp ligand (ppzmp = 2,4‐di‐tert‐butyl‐6‐(i‐propoxy‐(3,5‐dimethylpyrazol‐1‐yl)methyl)phenoxo). Complexes 1 – 3 have been tested in the ring opening polymerization (ROP) of L ‐lactide. The dimeric mono(phenoxo) derivative 2 was inactive in the ROP of L ‐lactide. Quite surprisingly, complex 3 was found to be active in ROP of L ‐ and rac‐lactide, showing a good molar‐mass control. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3632–3639, 2010 相似文献
12.
Experimental and computational studies of ring‐opening polymerization of ethylene brassylate macrolactone and copolymerization with ε‐caprolactone and TBD‐guanidine organic catalyst
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Ana Pascual Haritz Sardón Fernando Ruipérez Raquel Gracia Pallavi Sudam Antonio Veloso David Mecerreyes 《Journal of polymer science. Part A, Polymer chemistry》2015,53(4):552-561
The ring‐opening polymerization (ROP) of ethylene brassylate, catalyzed by the cyclic guanidine 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) is reported. Several experimental parameters were evaluated for bulk ROP process and polyesters, resulting in molecular weights between 3 and 15 kg mol?1. End‐group analysis by 1H nuclear magnetic resonnance (NMR) and matrix assisted laser desorption ionization time of flight computational studies supports the dual behavior of TBD, which can act as both a catalyst and initiator of the polymerization process. Under optimum conditions, semicrystalline poly(ethylene brassylate‐co‐ε‐caprolactone) random copolymers were synthesized. Depending on the comonomer content, our results showed a range of melting temperatures between 39 and 69 °C. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 552–561 相似文献
13.
Noureddine Ajellal Christophe M. Thomas Jean‐François Carpentier 《Journal of polymer science. Part A, Polymer chemistry》2009,47(12):3177-3189
The copolymerization of racemic β‐butyrolactone (rac‐BLMe) with racemic “allyl‐β‐butyrolactone” (rac‐BLallyl) in toluene, catalyzed by the discrete amino‐alkoxy‐bis(phenolate) yttrium‐amido complex 1 , gave new poly(β‐hydroxyalkanoate)s with unsaturated side chains. The poly(BLMe‐co‐BLallyl) copolymers produced have a highly syndiotactic backbone structure (Pr = 0.80–0.84) with a random enchainment of monomer units, as evidenced by 13C NMR, and high molecular weight (Mn up to 58,000 g mol?1) with a narrow polydispersity (Mw/Mn = 1.07–1.37), as determined by GPC. The comonomer incorporation (5–50 mol % rac‐BLallyl) was a linear function of the feed ratio. The pendant vinyl bond of the side‐chains in those poly(BLMe‐co‐BLallyl) copolymers allowed the effective introduction of hydroxy or epoxy groups via dihydroxylation, hydroboration‐oxidation or epoxidation reactions. NMR studies indicated that all of these transformations proceed in an essentially quantitative conversion and do not affect the macromolecular architecture. Some thermal properties (Tm, ΔHm, Tg) of the prepared polymers have been also evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3177–3189, 2009 相似文献
14.
Marc Brestaz Nicolas Desilles Guillaume Le Claude Bunel 《Journal of polymer science. Part A, Polymer chemistry》2011,49(19):4129-4138
Two ways to obtain aliphatic polyesters (PEs) from dimethylketene and acetaldehyde were investigated. On the one hand, a direct anionic copolymerization was carried out in toluene at ?60 °C. The resulting polymer was mainly composed of PE units. On the other hand, a two‐step process involving the synthesis of 3,3,4‐trimethyl‐2‐oxetanone by [2+2] cycloaddition, followed by its ring‐opening polymerization, with various initiators and solvents, led to the expected PE. Molecular weights up to 9000 g mol?1 (measured by nuclear magnetic resonance (NMR)), with narrow polydispersity around 1.2, were obtained. These polymers were found stable up to 274 °C under nitrogen and a broad and complex endothermic peak attributed to crystallinity was observed near 139 °C by differential scanning calorimetry (DSC). The crystallinity, measured by X‐ray diffraction, was close to 0.45. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
15.
Deivasagayam Dakshinamoorthy Frédéric Peruch 《Journal of polymer science. Part A, Polymer chemistry》2012,50(11):2161-2171
A series of di‐ and triblock copolymers [poly(L ‐lactide‐b‐ε‐caprolactone), poly(D,L ‐lactide‐b‐ε‐caprolactone), poly(ε‐caprolactone‐b‐L ‐lactide), and poly(ε‐caprolactone‐b‐L ‐lactide‐b‐ε‐caprolactone)] have been synthesized successfully by sequential ring‐opening polymerization of ε‐caprolactone (ε‐CL) and lactide (LA) either by initiating PCL block growth with living PLA chain end or vice versa using titanium complexes supported by aminodiol ligands as initiators. Poly(trimethylene carbonate‐b‐ε‐caprolactone) was also prepared. A series of random copolymers with different comonomer composition were also synthesized in solution and bulk of ε‐CL and D,L ‐lactide. The chemical composition and microstructure of the copolymers suggest a random distribution with short average sequence length of both the LA and ε‐CL. Transesterification reactions played a key role in the redistribution of monomer sequence and the chain microstructures. Differential scanning calorimetry analysis of the copolymer also evidenced the random structure of the copolymer with a unique Tg. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
16.
Alvaro A. A. De Queiroz cio J. Frana Gustavo A. Abraham Julio S. Romn 《Journal of Polymer Science.Polymer Physics》2002,40(8):714-722
The ring‐opening polymerization of ?‐caprolactone (?‐CL) catalyzed by iodine (I2) was studied. The formation of a charge‐transfer complex (CTC) among triiodide, I, and ?‐CL was confirmed with ultraviolet–visible spectroscopy. The monomer ?‐CL was polymerized in bulk using I2 as a catalyst to form the polyester having apparent weight‐average molecular weights of 35,900 and 45,500 at polymerization temperatures of 25 and 70 °C, respectively. The reactivity of both, ?‐CL monomer and ?‐CL:I2 CTC, was interpreted by means of the potential energy surfaces determined by semiempirical computations (MNDO‐d). The results suggest that the formation of the ?‐CL:I2 CTC leads to the ring opening of the ?‐CL structure with the lactone protonation and the formation of a highly polarized polymerization precursor (?‐CL)+. The band gaps approximated from an extrapolation of the oligomeric polycaprolactone (PCL) structures were computed. With semiempirical quantum chemical calculations, geometries and charge distributions of the protonated polymerization precursor (?‐CL)+ were obtained. The calculated band gap (highest occupied molecular orbit/lowest unoccupied molecular orbit differences) agrees with the experiment. The analysis of the oligomeric PCL isosurfaces indicate the existence of a weakly lone pair character of the C?O and C? O bonds suggesting a ?‐CL ring‐opening specificity. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 714–722, 2002 相似文献
17.
18.
Ring‐opening polymerization and block copolymerization of L‐lactide with divalent samarocene complex
Dongmei Cui Tao Tang Wuguo Bi Jianhua Cheng Wenqi Chen Baotong Huang 《Journal of polymer science. Part A, Polymer chemistry》2003,41(17):2667-2675
Divalent samarocene complex [(C5H9C5H4)2Sm(tetrahydrofuran)2] was prepared and characterized and used to catalyze the ring‐opening polymerization of L ‐lactide (L‐LA) and copolymerization of L‐LA with caprolactone (CL). Several factors affecting monomer conversion and molecular weight of polymer, such as polymerization time, temperature, monomer/catalyst ratio, and solvent, were examined. The results indicated that polymerization was rapid, with monomer conversions reaching 100% within 1 h, and the conformation of L‐LA was retained. The structure of the block copolymer of CL/L‐LA was characterized by NMR and differential scanning calorimetry. The morphological changes during crystallization of poly(caprolactone) (PCL)‐b‐P(L‐LA) copolymer were monitored with real‐time hot‐stage atomic force microscopy (AFM). The effect of temperature on the morphological change and crystallization behavior of PCL‐b‐P(L‐LA) copolymer was demonstrated through AFM observation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2667–2675, 2003 相似文献
19.
Wen‐Chou Hung Yong Huang Chu‐Chieh Lin 《Journal of polymer science. Part A, Polymer chemistry》2008,46(19):6466-6476
A series of efficient catalysts, based on zinc alkoxides coordinated with NNO‐tridentate Schiff‐base ligands (L1H‐L6H), for ring opening polymerization of L ‐lactide have been prepared. The reactions of diethyl zinc (ZnEt2) with L1H‐L6H yielded [(μ‐L)ZnEt]2 ( 1a–6a ), respectively. Further reaction of compounds 1a–6a with benzyl alcohol (BnOH) produced the corresponding compounds of [LZn(μ‐OBn)]2 ( 1b–6b), respectively. X‐ray crystal structural studies reveal that all of these compounds 1a–6a are dimeric bridging through the phenolato oxygen atoms of the Schiff‐base ligand. However, the molecular structures of 1b–6b show a dimeric character bridging through the benzylalkoxy oxygen atoms. Ring‐opening polymerization of L ‐lactide, initiated by 1b–6b , proceeds rapidly with good molecular weight control and yields polymer with a very narrow molecular weight distribution. Experimental results show that the substituents on the imine carbon of the NNO‐ligand affect the reactivity of zinc complexes dramatically. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6466–6476, 2008 相似文献
20.
Fabrice Stassin Robert Jrme 《Journal of polymer science. Part A, Polymer chemistry》2005,43(13):2777-2789
Ring‐opening polymerization (ROP) of (L,L)‐lactide (LA) has been initiated by dibutyltin dimethoxide in supercritical carbon dioxide (sc CO2). Polymerization is controlled and proceeds at quasi the same rate as in toluene, which indicates that the reactivity of the propagating species is not impaired by parasitic carbonation reaction. Random copolymerization of LA with ?‐caprolactone (CL) has also been studied in sc CO2, and the reactivity ratios have been determined as 5.8 ± 0.5 for LA and 0.7 ± 0.25 for CL. These values have to be compared to 0.7 ± 0.25 for LA and 0.15 ± 0.05 for CL in toluene. Good control on ROP of CL and LA in sc CO2 has been confirmed by the successful synthesis of diblock copolymers by sequential polymerization of CL and LA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2777‐2789, 2005 相似文献