Ring-opening Polymerization of ε-Caprolactone Using Lanthanide Tris（4-tert-butylphenolate）s as a Single-component Initiator

The ring-opening polymerization of ε-caprolactone (CL) initiated by novel singlelanthanide tris(4-tert-butylphenolate)s [Ln(OTBP)3] is reported. Single-component La(OTBP)3can effectively prepare polycaprolactone (PCL) with over 90% yield and viscosity averagemolecular weight about 60 × 103 under quite mild conditions: molar ratio of CL to initiator is 1000,60 ℃, 2 h in toluene. Mechanism study indicates that the monomer inserts into the growing chainvia the break of acyl-oxygen bond of CL.     

Ring-opening Polymerization of ε-Caprolactone by Lanthanide Tris(2,6-dimethylphenolate)s

Ring openingpolymerizationofCLisamainrouteofpreparingbiodegradableandbiocompatiblePCL ,forwhichtherehasbeengrowinginterestinthedevelopmentofeffi cientinitiatorsforthering openingpolymerizationofCL .Recently ,rareearthcompoundsasinitiatorshavebeenat tractingincreasingattentionbecauseoftheirlowtoxicityandhighefficiency .Ourgroupreportedaseriesofrareearthcatalystsforthering openingpolymerizationandcopolymerizationofCL .1 5Thispaperdealswiththering openingpolymerizationofCLinitiatedwithLn(OD…     

Novel Single－component Rare Earth Phenolate Catalyst for Ring－opening Polymerization of ε－Caprolactone

Polycaprolactone( PCL) is important as abiodegradable and biocompatible material.It iscommonly prepared by the ring- opening polymer-ization ofε- caprolactone( CL) .Various catalystssuch as alkali- metal alkoxides[1] ,alkali- metalalkyls[2 ] ,aluminium alkoxide and transition metalalkoxides[3 ] have been exploited for the polymeriza-tion of CL.Nevertheless,these initiators exhibitasomewhatlower reactivity than the anionic ones[4] .In recent years,the increasing attention has beenpaid to th…     

Polymerization of n-Hexyl Isocyanate Initiated by Novel Rare Earth Tris （2,6-di-tert-butyl-4-methylphenolate）

The polymerization of n-hexyl isocyanate (HNCO) was carried out in the presence of a novel single initiator, rare earth tris (2,6-di-tert-butyl-4-methylphenolate) [Ln(OAr)3]. The influences of reaction conditions such as the monomer concentration, the polymerization temperature and time, and the types of solvents on the polymerization of HNCO were studied. Polymerizations of phenyl, i-propyl, p-tolyl, n-butyl and n-octyl isocyanates with La(OAr)3 were also examined.     

RING-OPENING POLYMERIZATION OF 1,4-DIOXAN-2-ONE INITIATED BY LANTHANUM TRIS（ 2,6-DI-TERT-BUTYL-4-METHYLPHENOLATE）

The ring-opening polymerization of 1,4-dioxan-2-one （PDO） was carried out by lanthanum tris（2,6-di-tert-butyl-4- methylphenolate） （La（OAr）3） as novel single component initiaLor. The influences of polymerization reaction temperature and the molar ratio of monomer to initiator on the monomer conversion and molecular weight of poly（1,4-dioxan-2-one） （PPDO） were explored. PPDO with high viscosity average molecular weight of 1.95×10^5 can be prepared at 40℃ when [PDO]/ [La（OAr）3] molar ratio was 800. Mechanism investigation shows that the polymerization proceeds through a ＂coordination- insertion＂ mechanism with selective rupture of acyl-oxygen be,nd of PDO.     

Synthesis and Crystal Structure of 1-（Trifluoromethyl）-1-（propioloyl）-（E）-3-oxo-（2-thienyl）-（2-naphthylamine）

1INTRODUCTIONTheSchiffbasesderivedfromb-diketonesandaliphaticamineshavebeenshowntoexistastheketo-amines.However,ifsubstituentseitherattheketooraminogrouparearomatic,itmaybeexpectedtheenoliminewillbethefavoredtautomericform[1].Recently,someSchiffbasesderivedfromTTA(4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione)andPMBPhavebeenstudiedbyWang[2]andYu[3]etal.Inordertostudytherelationshipbetweenthestructuresandperformancesofthesecompounds,thetitlecom-poundwillbereportedherein.2EXPERIMENT…     

Synthesis and Crystal Structure of Lanthanide Schiff Base Complex [2-OC6H4CHN（2,6-i-Pr2C6H3）]2ErCl（THF）

1 INTRODUCTION The Schiff base ligands have been used to provide a stereochemically rigid ligand framework in homogenous precatalysts of some metals, such as salen Cr catalysts in asymmetric ring-opening re- action of epoxide[1] and salen Al in ring-opening polymerization of lactide and related cyclic esters[2]. Recently, it was reported that the bidentate Schiff base complexes of early and late transition metals can be served as promising alternatives to metal- locene catalysts for th…     

Poly{ [4-（hydroxyl）（tosyloxyl）iodo]styrene} Promoted Halotosyloxylation Reaction of Alkynes

Halotosyloxylation reaction of alkynes with iodine or NBS or NCS was efficiently promoted by the poly { [4-(hydroxyl)(tosoyloxyl)iodo]styrene }.     

Synthesis and Crystal Structure of 4-（4-Bromophenyl）- 3,4-dihydro-6-methyl quinolin-2（1H）-one

The title compound (C16H14BrNO) has been synthesized by the reaction of p-tolylamine, Meldrum’s acid and 4-bromo-benzaldehyde, and its structure was characterized by IR, 1H NMR and X-ray single-crystal diffraction. The crystal belongs to monoclinic, space group P21/n with a = 7.6850(11), b = 8.3004(11), c = 21.301(3) , β = 95.110(2)°, V = 1353.4(3) 3, Mr = 316.19, Z = 4, Dc = 1.552 g/cm3, μ(MoKα) = 3.028 mm-1, F(000) = 640, the final R = 0.0345 and wR = 0.0768. X-ray analysis reveals that the atoms of C(1), C(2), C(3), C(4), C(5) and N(1) form a six-membered ring of boat conformation.     

Ring‐opening polymerization of ε‐caprolactone via the bismuth‐2‐mercaptoethanol complex

A complex consisting of one Bi³⁺ ion and two 2‐mercaptoethanol units (BiME₂) was used as initiator for the ring‐opening polymerization of ε‐caprolactone in bulk. A kinetic comparison showed that BiME₂ is as reactive as initiator as Sn‐octanoate and more reactive than Bi‐hexanoate. The difference to BiHex₃ decreased at higher temperatures and upon addition of an alcohol as coinitiator. When tetra(ethylene glycol) was used as coinitiator, it was completely incorporated into the poly(εCL) chain, so that telechelic polylactones having two OH‐endgroups were formed. In the absence of a coinitiator, 2‐mercaptoethanol or its disulfide were incorporated in the form of ester groups. Furthermore, it was found by MALDI‐TOF mass spectrometry that small amounts of cyclic oligolactones (detected up to a degree of polymerization of 17) were formed under all reaction conditions. Higher temperatures and longer times favored a higher content of cycles. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3175–3183, 2006     

Ring‐opening polymerization of lactide, ε‐caprolactone and their copolymerization catalyzed by β‐diketiminate zinc complexes

A series of zinc silylamido complexes bearing non‐symmetric β ‐diketiminate ligands were synthesized and structurally characterized. Ring‐opening polymerization (ROP) of rac ‐lactide catalyzed by these zinc complexes afforded heterotactic polylactides at room temperature (P _r = 0.79 ~ 0.83 in THF). The steric and electronic characteristics of the ancillary ligands showed significant influence on the polymerization performance of the corresponding zinc complexes. All these zinc complexes also showed moderate activities toward the polymerization of ε ‐caprolactone at ambient temperature in toluene, producing polycaprolactones (PCLs) with high molecular weights and moderate polydispersities. PCL‐b ‐PLLA copolymers could be obtained via three different copolymerization strategies (one‐pot polymerization, and sequential addition of the two monomers in either order) by adopting complex 6 as the initiator through the adjustment of reaction temperatures. The diblock nature of the copolymers was confirmed by ¹³C NMR spectroscopy and DSC analysis.     

Ring‐opening polymerization of ε‐caprolactone and L‐lactide from silica nanoparticles surface

Coating of silica nanoparticles by biocompatible and biodegradable polymers of ε‐caprolactone and L ‐lactide was performed in situ by ring‐opening polymerization of the cyclic monomers with aluminum, yttrium, and tin alkoxides as catalysts. Hydroxyl groups were introduced on the silica surface by grafting of a prehydrolyzed 3‐glycidoxypropyl trimethoxysilane to initiate a catalytic polymerization in the presence of metal alkoxides. In this manner, free polymer chains were formed to grafted ones, and the graft density was controlled by the nature of the metal and the alcohol‐to‐metal ratio. The grafting reaction was extensively characterized by spectroscopic techniques and quantified. Nanocomposites containing up to 96% of polymer were obtained by this technique. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1976–1984, 2004     

稀土硫化物：e–己内酯开环聚合新催化剂

The ring-opening polymerization （ROP） of ε-caprolactone （ε-CL） using lanthanide thiolate complexes [（CH3CsH4）2Sm（μ-SPh）（THF）]2 （1） and Sm（SPh）3（HMPA）3 （2） as initiators has been investigated for the first time. Both of 1 and 2 were found to be highly efficient initiators for the ROP of ε-CL. The poly（ε-caprolactone） （PCL） with molecular weight Mn up to 1.97 ×10^5 and relatively narrow molecular weight distributions （1.20〈MW/Mn〈 2.00） have been obtained in high yield in the temperature range of 35-65℃. According to the polymer yield, 2 showed much higher activity than 1. However, the number-average molecular weight of PCL obtained with 2 was much lower than with 1. The possible polymerization mechanism of the ε-CL polymerization has been proposed based on the results of the end group analysis of the ε-CL oligomer.     

Ring opening insertion polymerization of ε‐caprolactone with hydrogen phosphonate initiators

In this work, ring opening insertion polymerization (ROIP) of ε‐caprolactone (ε‐CL) using a series of hydrogen phosphonates (H‐phosphonates) as initiators was investigated. The ROIP occurred by a coordination‐insertion mechanism containing two steps. First, the carbonyl carbon was attacked by the phosphorus atom of the H‐phosphonate tautomerization (a phosphine‐like structure) and the acyl‐oxygen bond was broken. An intermediate was formed by the coordination of the former carbonyl carbon and acyl‐oxygen of ε‐CL to phosphorus atom. Then the phosphorus‐alkoxide of H‐phosphonate was cleavaged to form acyl‐alkoxide bond. Poly(ε‐caprolactone) (PCL)‐inserted H‐phosphonates (PCL‐HPs), which was not only the product of the occurred ROIP but also the initiator for the next ROIP, were produced. After 60 min of microwave irradiation (510 W), PCL with a number‐average molar mass of 7800 g/mol and monomer conversion over 92% was obtained. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6214–6222, 2009     

Homoleptic lanthanide metallocenes and their derivates: syntheses,structural characterization and their catalysis for ring‐opening polymerization of ε‐caprolactone

Homoleptic lanthanide metallocenes Cp′₃Ln [Cp′ = methylcyclopentadienyl, Ln = Y ( 1 ), Er ( 2 ), Sm ( 3 ); Cp′ = cyclopentadienyl, Ln = Er ( 4 ) and Sm ( 5 )] have been found to be a novel type of initiators for the ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL). Among them, complex 1 shows the highest catalytic activity for ROP of ε‐CL. In addition, a novel neutral trifluoroethoxo yttrium complex [(MeC₅H₄)₂Y(µ‐OCH₂CF₃)]₂ ( 6 ) has been synthesized by the reaction of 1 with trifluoroethanol in 1:1 molar ratio in toluene and characterized by single‐crystal X‐ray structural analysis. Preliminary study shows that the catalytic activity of tris(methylcyclopentadienyl)yttrium complex 1 is higher than that of bis(methylcyclopentadienyl)yttrium complex 6 . The mechanism of the present polymerization was studied by NMR spectra. Copyright © 2006 John Wiley & Sons, Ltd.     

Anionic lanthanide phenoxide complexes as novel single‐component initiators for the polymerization of ε‐caprolactone and trimethylene carbonate

The anionic lanthanide‐sodium‐2,6‐di‐tert‐butyl‐phenoxide complexes [Ln(OAr)₄][Na(DME)₃]·DME (Ln = Nd 1 (neodymium), Sm 2 (samarium), or Gd 3 (gadolium); DME = dimethoxyethane) were synthesized by the reaction of anhydrous LnCl₃ with 4 equiv of sodium‐2,6‐di‐tert‐butyl‐phenoxide NaOAr in high yields and structurally characterized. These complexes showed high catalytic activity in the ring‐opening polymerizations of ?‐caprolactone (?‐CL) and trimethylene carbonate (TMC). The catalytic activity profoundly depended on the lanthanide metals. The active order of Gd < Sm < Nd for the polymerization of ?‐CL and TMC was observed. The polymers obtained with these initiators all showed a unimodal molecular weight distribution, indicating that the [Ln(OAr)₄][Na(DME)₃]·DME anionic complexes could be used as single‐component initiators. The anionic complex was more efficient than the corresponding neutral complex, Ln(OAr)₃(THF)₂. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1210–1218, 2007     

Titanium complexes of dialkanolamine ligands as initiators for living ring‐opening polymerization of ε‐caprolactone

The titanium complexes with one ( 1a , 1b , 1c ) and two ( 2a , 2b ) dialkanolamine ligands were used as initiators in the ring‐opening polymerization (ROP) of ε‐caprolactone. Titanocanes 1a and 1b initiated living ROP of ε‐caprolactone affording polymers whose number‐average molecular weights (M_n) increased in direct proportion to monomer conversion (M_n ≤ 30,000 g mol^?1) in agreement with calculated values, and were inversely proportional to initiator concentration, while the molecular weight distribution stayed narrow throughout the polymerization (M_w/M_n ≤ 1.2 up to 80% monomer conversion). ¹H‐NMR and MALDI‐TOF‐MS studies of the obtained poly(ε‐caprolactone)s revealed the presence of an isopropoxy group originated from the initiator at the polymer termini, indicating that the polymerization takes place exclusively at the Ti–OⁱPr bond of the catalyst. The higher molecular weight polymers (M_n ≤ 70,000 g mol^?1) with reasonable MWD (M_w/M_n ≤ 1.6) were synthesized by living ROP of ε‐caprolactone using spirobititanocanes ( 2a , 2b ) and titanocane 1c as initiators. The latter catalysts, according MALDI‐TOF‐MS data, afford poly(ε‐caprolactone)s with almost equal content of α,ω‐dihydroxyl‐ and α‐hydroxyl‐ω(carboxylic acid)‐terminated chains arising due to monomer insertion into “Ti–O” bond of dialkanolamine ligand and from initiation via traces of water, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1230–1240, 2010     

Cyclic poly(ε‐caprolactone) synthesized by combination of ring‐opening polymerization with ring‐closing metathesis,ring closing enyne metathesis,or “click” reaction

This article described the synthesis of cyclic poly(ε‐caprolactone) (PCL) via ring‐closing metathesis (RCM), ring closing enyne metathesis (RCEM), and “click” reaction of different difunctional linear PCL. Linear PCL precursors were prepared by ring‐opening polymerization (ROP) of ε‐caprolactone in bulk using 10‐undecen‐1‐ol or propargyl alcohol as the initiator, followed by reacting with corresponding acyl chloride containing vinyl or azido end group. The subsequent end‐to‐end intramolecular coupling reactions were performed under high dilution conditions. The successful transformation of linear PCL precursor to cyclic PCL was confirmed by Gel permeation chromatography, ¹H NMR, and Fourier transform infrared measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3022–3033, 2009