Melt block copolymerization of ϵ-caprolactone and L-lactide

AB block copolymers of ϵ-caprolactone and (L )-lactide could be prepared by ring-opening polymerization in the melt at 110°C using stannous octoate as a catalyst and ethanol as an initiator provided ϵ-caprolactone was polymerized first. Ethanol initiated the polymerization of ϵ-caprolactone producing a polymer with ϵ-caprolactone derived hydroxyl end groups which after addition of L -lactide in the second step of the polymerization initiated the ring-opening copolymerization of L -lactide. The number-average molecular weights of the poly(ϵ-caprolactone) blocks varied from 1.5 to 5.2 × 10³, while those of the poly(L -lactide) blocks ranged from 17.4 to 49.7 × 10³. The polydispersities of the block copolymers varied from 1.16 to 1.27. The number-average molecular weights of the polymers were controlled by the monomer/hydroxyl group ratio, and were independent on the monomer/stannous octoate ratio within the range of experimental conditions studied. When L -lactide was polymerized first, followed by copolymerization of ϵ-caprolactone, random copolymers were obtained. The formation of random copolymers was attributed to the occurrence of transesterification reactions. These side reactions were caused by the ϵ-caprolactone derived hydroxyl end groups generated during the copolymerization of ϵ-caprolactone with pre-polymers of L -lactide. The polymerization proceeds through an ester alcoholysis reaction mechanism, in which the stannous octoate activated ester groups of the monomers react with hydroxyl groups. © 1997 John Wiley & Sons, Inc.     

Zinc Glutarate Catalyzed Synthesis and Biodegradability of Poly(carbonate-co-ester)s from CO2, Propylene Oxide,and ϵ-Caprolactone

A zinc glutarate (ZnGA) catalyst was prepared from the reaction of zinc oxide and glutaric acid in dry toluene. ZnGA was found to exhibit a catalytic activity for the copolymerization of carbon dioxide (CO₂) and propylene oxide (PO) and the homopolymerization of PO but to reveal no catalytic activity for the homopolymerization of ϵ-caprolactone (CL). The ZnGA-catalyzed polymerization was extended for the terpolymerization of CO₂ with PO and CL, producing poly(propylene carbonate-co-ϵ-caprolactone)s (PPCCLs) with a reasonably high molecular weight in high yields. In the terpolymerization, PO and CL were used as both co-monomers and reaction media, after the reaction completed, the excess co-monomers were easily recovered and reused in the next terpolymerization batch. For the synthesized polymers, enzymatic and biological degradability were investigated.     

Synthesis and characterization of biodegradable block copolymers of ϵ-caprolactone and D,L-lactide initiated by potassium poly(ethylene glycol)ate

Poly(D ,L -lactide)–poly(ϵ-caprolactone)–poly(ethylene glycol)–poly(ϵ-caprolactone)–poly(D ,L -lactide) block copolymer (PLA–PCL–PEG–PCL–PLA) was prepared by copolymerization of ϵ-caprolactone (ϵ-CL) and D ,L -lactide (D ,L -LA) initiated by potassium poly(ethylene glycol)ate in THF at 25°C. The copolymers with different composition were synthesized by adjusting the mole ratio of reaction mixture. The resulted copolymers were characterized by ¹H-NMR, ¹³C-NMR, IR, DSC, and GPC. Efforts to prepare copolymers with the corresponding structure of PCL–PLA–PEG–PLA–PCL and D ,L -lactide/ϵ-caprolactone random copolymers were not successful. © 1997 John Wiley & Sons, Inc.     

Modified poly(ϵ-caprolactone)s and their use for drug-encapsulating nanoparticles

Poly(ϵ-caprolactone) (PCL)-polydimethylsiloxane diblock and triblock copolymers and poly(ϵ-caprolactone-co-4-ethylcaprolactone) random copolymers were prepared through the homogeneously catalyzed coordination anionic polymerization of ϵ-caprolactone (CL) and the copolymerization of CL with 4-ethyl-ϵ-caprolactone (EtCL) in the presence of hydroxy-terminated polysiloxanes or allyl alcohol as chain-transfer agents, respectively. Polysiloxane precursors with hydroxypropyl or hydroxyethyl propyl ether end groups were obtained by the hydrosilation of the appropriate unsaturated alcohol with monofunctional or difunctional hydro-terminated polysiloxanes of different molecular weights. As proven by differential scanning calorimetry analysis, the presence of siloxane blocks and EtCL units determined the diminished copolymer crystallinity, which was shown by the reduced melting temperatures and enthalpy of fusion with respect to those of pure PCL. Both types of copolymers were found to form, in the presence of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) emulsifier, monodisperse and stable nanoparticles able to encapsulate different types of bioactive compounds (Vitamin E and indomethacin). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 689–700, 2004     

马来酸酐─环氧丙烷共聚物的合成及结构表征

本文将稀土络合物Ｎｄ（Ｐ２０４）３、Ｎｄ（Ｐ５０７）３、Ｎｄ（ｎａＰｈ）３、Ｎｄ（ａｃａｃ）３．３Ｈ２Ｏ与烷基铝组成的二元体系催化剂用于共聚马来酸酐（ＭＡｎ）与环氧丙烷（ＰＯ）获得成功．并采用１Ｈ—ＮＭＲ研究了共聚物三元组序列分布．结果表明，稀土络合催化剂为ＭＡｎ与ＰＯ共聚的优良催化刑，可得到高转化率、高交替度共聚物．共聚物数均分子量Ｍｎ和分子量分布分别为２０００—３０００、１．３—１．７，共聚物中ＭＡｎ的摩尔含量４０％以上．共聚物组成及序列分布与投料比、催化剂种类、溶剂性质等有关．理论计算表明，序列分布符合三级马尔可夫（Ｍａｒｋｏｆｆｉａｎ）过程．     

Catalysts as Key Enablers for the Synthesis of Bioplastics with Sophisticated Architectures

Bioplastics are one of the answers to environmental pollution and linear material flows. The most promising bioplastic polylactide (PLA) is already replacing conventional plastics in a number of applications. The properties of PLA, however, do not fit for all potential application areas, but they can be altered by the introduction of comonomers. The copolymerization of lactide (LA) with other lactones like ϵ-caprolactone (CL) has been established for several years. Nevertheless, controlling copolymerizations remains a challenge due to the high complexity of the system. Copolymerization of LA with other monomer classes is much less investigated, but has the chance to overcome the limitations in material properties that occur when only lactones are used. The crucial factor for all copolymerizations is the catalyst. It dominates the reaction kinetics and determines the resulting microstructure. In this review, copolymerization catalysts for LA are presented divided into catalysts for the synthesis of lactone block copolymers, lactone random copolymers, and multimechanistically synthesized copolymers. The selected catalysts are highlighted either owing to their industrially applicable polymerization conditions or their non-standard mechanism.     

Benzo-12-crown-4 modified N-heterocyclic carbene for organocatalyst: Synthesis,characterization and degradation of block copolymers of ϵ-caprolactone with L-lactide

A set of poly(L-lactide)-poly(?-caprolactone) diblock copolymers (AB) and poly(L-lactide)-poly(?-caprolactone)-poly(L-lactide) triblock copolymers (ABA) with predictable molecular weights and relatively narrow distributions were synthesized by ring-opening polymerization of successively added ?-caprolactone (?-CL) and L-lactide (LLA) using 4-methyl benzo-12-crown-4 imidazol-2-ylidene as catalyst. The effects of polymerization conditions, such as reaction time, temperature, monomer/catalyst molar ratio and monomer concentration on the copolymerization have been discussed in detail. The resulting copolymers were characterized by ¹H-NMR, ¹³C-NMR, IR, GPC and DSC methods which confirmed the successful synthesis of block copolymers of LLA and ?-CL. Hydrolytic degradation of the polymers showed that the PLLA-PCL-PLLA copolymer exhibited faster degradation as compared with the PCL homopolymer in alkaline medium at 37°C.     

A comparison of polymerization characteristics and mechanisms of ε-caprolactone and trimethylene-carbonate with rare earth halides

Characteristics and mechanisms of the ring opening-polymerizations of ε-caprolactone (CL) and trimethylene carbonate (TMC) with rare earth halides have been compared for the first time. It has been found that rare earth halides show high catalytic activities for the polymerization of TMC, but very low activities for that of CL polymerization. The copolymerization of CL and TMC can proceed only in the presence of high contents of TMC in the comonomer feed. The copolymerization rate decreases rapidly with increasing molar fraction of CL in the feed. The mechanism study by IR, ¹H-, ¹³C-, and ³¹P-NMR spectra shows that the first step reaction of the polymerization of TMC or CL with rare earth halide is the complexation of monomer to the rare earth ion. The strong coordination of TMC to rare earth ion induces the ring-cleavage of TMC and generation of the cationic species, which initiate the polymerization of TMC via a cationic process. However, the polymerization of CL with rare earth halide is an “activated-hydrolysis” process, in which rare earth catalyst does not initiate the polymerization but serves as an activator of CL. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1339–1352, 1997     

Tri-component diblock copolymers of poly(ethylene glycol)–poly(ε-caprolactone-<Emphasis Type="Italic">co</Emphasis>-lactide): synthesis,characterization and loading camptothecin

Biodegradable tri-component diblock copolymer was synthesized by bulk copolymerization of ε-caprolactone (CL) and D, L-lactide (LA) in the presence of methoxy poly(ethylene glycol) (MePEG), using stannous octoate as catalyst. Their chemical structure and physical properties were investigated by GPC, NMR, DSC, TGAand XRD. The increase of CL/LA ratio in the diblock copolymer leads to lower T _g, higher decomposition temperature and crystallinity. Nanoparticles formulated from MePEG–poly(CL-co-LA) (PCAE) possess spherical structure, which was characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The DLS results indicate that the particle size increased with the increase of CL/LA ratio and the hydrophobic fragment length in the copolymer. The drug encapsulation efficiency and the drug release behavior in vitro conditions of camptothecin were measured by high performance liquid chromatography (HPLC). The encapsulation efficiency can be achieved as high as 84.4% and the release behavior can be made well-controlled. MePEG–poly(CL-co-LA) nanoparticles might have a great potential as carriers for hydrophobic drugs.     

马来酸酐─环氧丙烷共聚物的合成及结构表征

本文将稀土络合物Ｎｄ（Ｐ２０４）３，Ｎｄ（Ｐ５０７），Ｎｄ（ｎａｐｈ）３，Ｎｄ（ａｃａｃ）３．３Ｈ２Ｏ与烷基铝组成的二元体系催化剂用于共聚马来酸酐（ＭＡｎ）与环氧丙烷（ＰＯ）获得成功，并采用１Ｈ－ＮＭＲ研究了共聚的优良催化剂，可得到高转化率，高交替度共聚物，共聚物数均分子量Ｍｎ和分子量分布分别为２０００－３０００，１．３－１．７，共聚物中ＭＡｎ的摩尔含量４０％以上。共聚物组成及序列分布与投料比，催     

Effect of polymerization catalysts on the microstructure of P(LLA-co-εCL)

The copolymerization of L ,L -lactide and ε-caprolactone was carried out using antimony trioxide and stannous octoate as catalysts. The effect of polymerization catalysts on the physical and the chemical microstructures of this copolymer was investigated by ¹³C NMR and DSC analysis. Antimony trioxide causes more random sequence distribution within the copolymer chain due to its higher transesterification characteristic than stannous octoate. The copolymer samples made with the antimony trioxide catalyst seem to have more amorphous phase structure, than those prepared using stannous octoate which are semicrystalline for the entire compositional range due to blocky copolymer sequences. © 1994 John Wiley & Sons, Inc.     

双金属氰化络合物催化环氧丙烷和邻苯二甲酸酐共聚

采用双金属氰化络合物 (DMC)催化环氧丙烷 (PO)和邻苯二甲酸酐 (PA)共聚 ,探讨了共聚合特征 ,并用IR、1 H NMR和GPC对共聚物的结构和分子量进行了表征 .发现DMC催化剂对该共聚反应速度快 ,转化率高 ,是该反应的有效催化剂 ,催化剂浓度为 6 0mg kg时 ,90℃下 ,以THF作溶剂共聚反应 3h ,转化率可达94 0 % .聚合速度甚至比DMC催化PO均聚还快 .该共聚反应可在多种溶剂中进行 ,极性溶剂更有利于共聚合 ,溶液聚合温度比本体共聚低 ,合适的溶液共聚温度在 90～ 10 0℃之间 .共聚产物的分子量受催化剂用量、反应温度和体系中水份含量的影响 ,数均分子量在数百至数千之间 .考察该共聚体系的动力学表明 ,该共聚反应速率对单体浓度呈一级关系     

Concerning the Deactivation of Cobalt(III)‐Based Porphyrin and Salen Catalysts in Epoxide/CO2 Copolymerization

Functioning as active catalysts for propylene oxide (PO) and carbon dioxide copolymerization, cobalt(III)‐based salen and porphyrin complexes have drawn great attention owing to their readily modifiable nature and promising catalytic behavior, such as high selectivity for the copolymer formation and good regioselectivity with respect to the polymer microstructure. Both cobalt(III)–salen and porphyrin catalysts have been found to undergo reduction reactions to their corresponding catalytically inactive cobalt(II) species in the presence of propylene oxide, as evidenced by UV/Vis and NMR spectroscopies and X‐ray crystallography (for cobalt(II)–salen). Further investigations on a TPPCoCl (TPP=tetraphenylporphyrin) and NaOMe system reveal that such a catalyst reduction is attributed to the presence of alkoxide anions. Kinetic studies of the redox reaction of TPPCoCl with NaOMe suggests a pseudo‐first order in cobalt(III)–porphyrin. The addition of a co‐catalyst, namely bis(triphenylphosphine)iminium chloride (PPNCl), into the reaction system of cobalt(III)–salen/porphyrin and PO shows no direct stabilizing effect. However, the results of PO/CO₂ copolymerization by cobalt(III)–salen/porphyrin with PPNCl suggest a suppressed catalyst reduction. This phenomenon is explained by a rapid transformation of the alkoxide into the carbonate chain end in the course of the polymer formation, greatly shortening the lifetime of the autoreducible PO‐ring‐opening intermediates, cobalt(III)–salen/porphyrin alkoxides.     

Functionalization of polyethylene based on metallocene catalysis and its application to syntheses of new graft copolymers possessing polar polymer segments

The control of hydroxylated polyethylene (PE) structures was investigated in the copolymerization of ethylene with allyl alcohol or 10-undecen-1-ol with a specific metallocene, methylaluminoxane, and trialkyl aluminum catalyst system through changes in the copolymerization conditions. The incorporation of allyl alcohol into the PE backbones was controllable through changes in the trialkyl aluminum, leading to terminally hydroxylated PE or a copolymer possessing hydroxyalkyl side chains. The copolymerization of ethylene with 10-undecen-1-ol gave copolymers with hydroxyalkyl side chains of various contents with a variety of molecular weights through changes in the copolymerization conditions. The obtained copolymers were useful as macroinitiators that allowed polar polymer segments to grow on the PE backbones, leading to the creation of graft copolymers that possessed PE and polar polymer segments. In this way, polyethylene-g-poly(propylene glycol) (PE-g-PPG) and polyethylene-g-poly(ϵ-caprolactone) (PE-g-PCL) were synthesized. The ¹³C NMR analysis of PE-g-PPG suggested that all the hydroxyl groups were consumed for propylene oxide polymerization, and transmission electron microscopy demonstrated nanoorder phase separation and indistinct phase boundaries. ¹³C NMR and gel permeation chromatography analyses indicated the formation of PE-g-PCL, in which 36–80 mol % of the hydroxyl groups worked as initiators for ϵ-caprolactone polymerization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3657–3666, 2003     

乙酰丙酮钇催化环氧氯丙烷的均聚合与共聚合

用过渡金属络合催化剂聚合环氧氯丙烷能获高分子量的聚合物。稀土络合催化剂对环氧乙烷,环氧丙烷及环硫丙烷的开环聚合具有明显效果。本文选用Y(acac)_3-H_2O-Al(i-Bu)_3催化剂,考察环氧氯丙烷的均聚合及其与环氧乙烷,环氧丙烷的共聚合,并用核     

Copolymerization of Carbonyl Sulfide and Propylene Oxide via a Heterogeneous Prussian Blue Analogue Catalyst with High Productivity and Selectivity

This study demonstrates the superiority of a stable and well-defined heterogeneous cobalt hexacyanocobaltate (Co₃[Co(CN)₆]₂), a typical cobalt Prussian Blue Analogue (CoCo-PBA) that catalyzes the copolymerization of carbonyl sulfide (COS) and propylene oxide (PO) to produce poly(propylene monothiocarbonate)s (PPMTC). The number-average molecular weights of the PPMTC were 66.4 to 139.4 kg/mol, with a polydispersity of 2.0–3.9. The catalyst productivity reached 1040 g polymer/g catalyst (12.0 h). The oxygen-sulfur exchange reaction (O/S ER), which would generate random thiocarbonate and carbonate units, was effectively suppressed, and thus the selectivity of the monothiocarbonate over carbonate linkages was up to >99%. It was shown that no cyclic thiocarbonate byproduct was produced during the heterogeneous catalysis of COS/PO copolymerization using CoCo-PBA as the catalyst. The content of monothiocarbonate and ether units in the copolymer chain could be regulated by tuning the feeding amount of COS.     

A convenient method to prepare random LA/CL copolymers from poly(<Emphasis Type="Italic">L</Emphasis>-lactide) and ε-caprolactone

Sequential addition of L-lactide (LA) followed by ε-caprolactone (CL), and simultaneous addition of both monomers, afforded random LA/CL copolymers in the presence of lanthanide aryloxides under mild conditions. Transesterification was proved to play a predominant role in random copolymer formation. Moreover, treatment of poly(L-lactide) with ε-CL led to random copolymer formation, which provides a new strategy not only to prepare random LA/CL copolymers, but also to directly modify PLLA.     

High yield synthesis of biodegradable poly(propylene carbonate) from carbon dioxide and propylene oxide

A novel SalenCo^III (2,4‐dinitrophenoxy) (Salen = N,N'‐bis(3,5‐di‐tert‐butylsalicylidene)‐1,2‐cyclohexanediamino) and 1,10‐phenanthroline monohydrate catalyst system was designed and employed for the copolymerization of CO₂ and propylene oxide (PO). The perfectly alternating copolymerization of CO₂ and PO proceeds effectively under middle temperature and pressure to yield poly(propylene carbonate) with a high yield and a high number average molecular weight of polymer. The structure of polymer was characterized by the IR and NMR measurements. The perfectly alternating copolymer was confirmed. The MALDI‐TOF spectrum insinuates that the copolymerization of CO₂ and PO was initiated by H₂O. Copyright © 2016 John Wiley & Sons, Ltd.     

Copolymerization of propylene oxide and carbon disulfide with diethylzinc–electron-donor catalyst

Copolymerization of propylene oxide with carbon disulfide was studied by using a catalyst consisting of diethylzinc (ZnEt₂) and various electron donors. Tertiary amines, tertiary phosphines, and hexamethylphosphoric triamide were the effective donors for the copolymerization, but ZnEt₂–water, alcohol, and primary or secondary amines having high activities for the homopolymerization of propylene oxide were not effective for the copolymerization of propylene oxide and carbon disulfide. The copolymers obtained were of low molecular weight and had a monomer unit ratio (CS₂/PO) of 0.5–0.7. In addition, a considerable amount of 1,3-oxathioran-4-methyl-2-thion was isolated as a by-product.     

Nd(naph)3-Al(i-Bu)3催化邻苯二甲酸酐与环氧丙烷交替共聚

Ｎｄ（ｎａｐｈ）３Ａｌ（ｉＢｕ）３催化邻苯二甲酸酐与环氧丙烷交替共聚房江华黄士力（宁波师范学院化学系，宁波３１５０２０）沈之荃（浙江大学高分子科学与工程学系，杭州３１００２７）关键词环烷酸钕，交替共聚，邻苯二甲酸酐，环氧丙烷分类号Ｏ６４３／ＴＱ３...