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.     

Controlled/living ring-opening polymerization of ε-caprolactone catalyzed by phosphoric acid

The bulk ring-opening polymerization(ROP) of ε-caprolactone(ε-CL) by various phosphoric acids using phenylmethanol as the initiator was conducted.1,1’-bi-2-Naphthol(BINOL)-based phosphoric acid was found to be an effective organocatalyst for ROP leading to polyesters at 90℃.The overall conversion to poly(ε-caprolactone) was more than 96% and poly(ε-caprolactone) with M w of 8400 and polydispersity index of 1.13 was obtained.1 H NMR spectra of oligomers demonstrated the quantitative incorporation of the protic initiator in the polymer chains and showed that transesterification reactions did not occur to a significant extent.The controlled polymerization was indicated by the linear relationships between the number-average molar mass and monomer conversion or monomer-to-initiator ratio.In addition,the present protocol provided an easy-to-handle,inexpensive and environmentally benign entry for the synthesis of biodegradable materials as well as polyesters for biomedical applications.     

Homopolymerization and Copolymerization of Adipic Anhydride with ε-Caprolactone Catalyzed by Rare Earth Trisphenolate

The ring-opening polymerization of adipic anhydride and the ring-opening copolymerization of adipic anhydride with ε-caprolactone catalyzed by single component rare earth trisphenolate have been reported. The structure of the copolymer poly（CL-b-AA） has been characterized by SEC, ^1H NMR and DSC.     

Copolymer of lactide and ε-caprolactone catalyzed by bimetallic Schiff base aluminum complexes

A series of copolymers of lactide(LA) and e-caprolactone(ε-CL) with different monomer feed ratios were achieved using three kinds of bimetallic Schiff aluminum complexes as catalysts. The ratios of LA and ε-CL units in different copolymers and the average segments length were determined by NMR analysis. The comparative kinetic study of L-LA/ε-CL and rac-LA/ε-CL copolymerization systems showed that the polymerization rate of LA was faster than ε-CL, and L-LA showed polymerization rate slightly faster than rac-LA. It was inferred that the copolymers achieved by these complexes were gradient copolymers with gradual change in distribution of LA and e-CL units. The thermal properties of these copolymers were characterized by DSC analysis, which showed that the glass transition temperature(Tg) of these copolymers changed regularly according to the pro-portion change of two structural units.     

Synthesis and Characterization of ABBA Block Copolymer of Glycolide and ε-Caprolactone

A biodegradable ABBA block copolymer was synthesized via the ring-opening co-polymerization of ε-Scaprolactone (CL, B) and glycolide (A) by means of step polymerization in the presence of ethylene glycol as an initiator and stannous octanoate as a catalyst at 110 ℃ for 48 h. The molecular length of the PCL prepolymer(BB) could be adjusted by controlling the molar ratio of the ethylene glycol initiator to ε-caprolactone monomer. The structure and the composition of the block copolymer were determined by the weight ratio of the monomer glycolide (A) to PCL pre-polymer(BB). The block copolymers were characterized by ^1H NMR, GPC, DSC and X-ray. The results confirm the successful synthesis of an ABBA block copolymer.     

A convenient method to prepare random LA/CL copolymers from poly(L-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.     

L-Lactide Homopolymerization and Copolymerization with ε-Caprolactone by Tetrahydrosalen Stabilized Yttrium Borohydride Complex

L-lactide（LLA） homopolymerization and copolymerization with ε-caprolactone（CL） in toluene initiated by tetrahydrosalen-supported yttrium borohydride complex were systematically investigated. A possible mechanism of LLA homopolymerization was proposed according to the 1H-NMR result. In addition, PCL-b-PLLA copolymers were synthesized by sequential addition of monomers and their structure was characterized by GPC, 1H-NMR and 13C-NMR.     

Construction of photoresponsive supramolecular micelles based on ethyl cellulose graft copolymer

In this work, a UV-Visible light controlled supramolecular system based on ethyl cellulose(EC) was constructed, combining the host-guest interaction of β-cyclodextrin(β-CD) group and trans-isomer of azobenzene(tAzo) group. To link β-CD to the hydrophobic section, renewable EC was used as macroinitiator to initiate the polymerization of ε-caprolactone(ε-CL) to form biocompatible and biodegradable comb copolymer EC-g-PCL, and β-CD was attached to the end of PCL side chain via click reaction. Meanwhile, hydrophilic PEG-tAzo was obtained by N,N'-dicyclohexylcarbodiimide(DCC) coupling. Then, the structures of the products were characterized by nuclear magnetic resonance(NMR) and gel permeation chromatography(GPC). Subsequently, with the formation of inclusion complexes by β-CD and tAzo groups, the obtained EC-g-PCL-β-CD/PEG-tAzo supramolecular system self-assembled in water with hydrophobic EC-g-PCL-β-CD as core and hydrophilic PEG-tAzo as shell. Furthermore, dynamic light scattering(DLS) and transmission electron microscopy(TEM) were utilized to investigate the particle size and size distribution, while NMR and UV-Vis spectra were applied to explore the UV-Visible light stimuli-responsiveness of the micelles.     

Dihydroxy Capped Triblock DTC and CL Oligomers Prepared by an Alkyl Glycol／Yttrium Phenolate System

Dihydroxy capped triblock oligomers of 2, 2-dimethyltrimethylene carbonate (DTC) and ε-caprolactone (CL) with number-average molecular weight from 3,000 to 12,000 g/mol have been synthesized by alkyl glycol initiator in the presence of yttrium tri(2, 6-di-tert-butyl-4-methylphenolate)s (Y(OAr)3) catalyst. They are expected to be used as macroinitiators for the design of new polymeric materials.     

Lanthanum heterocyclic Schiff-base complex initiated ring-opening polymerization of ε-caprolactone

Lanthanum complex supported by the heterocyclic Schiff-base ligand of N-(2-pyridyl)-3,5-di-tert-butyl-salicylaldimine was prepared and employed for the ring-opening polymerization(ROP)ofε-caprolactone(ε-CL).The polymers obtained with this initiator showed a unimodal molecular weight distribution implied that only one active species was present.Mechanism study revealed that the polymerization proceeds via acyl-oxygen bond cleavage.     

SYNTHESIS OF POLY(ETHYLENE TEREPHTHALATE)-POLYCAPROLACTONE BLOCK COPOLYMER BY DIRECT COPOLYMERIZATION*

Poly(ethylene terephthalate) -polycaprolactone block copolymer (PCL- b-PET) is a polyester withimproved biodegradability. In the present paper, a new direct copolymerization method of ε-caprolactone (ε-CL) and bishydroxyethylene terephthalate (BHET) in the presence of Ti(OBu)_4 was proposed for thesynthesis of PCL-b-PET. The PCL-b-PET copolymer was characterized by IR, GPC and ~1H-NMRtechniques, and the effects of synthesis conditions, such as temperature, reaction time and concentration ofcatalyst on the copolymerization were discussed.     

Binuclear Aluminum Complexes Supported by Linked Bis(β-diketiminate) Ligands for Ring-Opening Polymerization of Cyclic Esters

Binuclear aluminum alkyl complexes 2a–4g supported by linked bis(β-diketiminate) ligands were synthesized via the reaction of AlEt_3 or AlMe_3 and the corresponding proligand in a 2:1 molar ratio with moderate yields. The isolated complexes were well-characterized by ~1H-NMR, ~(13)C-NMR and elemental analysis. The binuclear nature of aluminum complex 2b was further confirmed by an X-ray diffraction study. All complexes 2a–4g could efficiently initiate the ring-opening polymerization(ROP) of ε-caprolactone in toluene. The substituents at the aromatic rings and the linker unit in the auxiliary ligands exerted significant influence on the catalytic behavior of the investigated aluminum complexes. Complex 4g(R~1 = R~2 = Cl) containing propylenyl bridging unit exhibited the highest catalytic activity among these complexes, which might be attributed to the increased electrophilicity of the metal center as well as more opened coordination sphere. The molecular weights of obtained poly(ε-caprolactone)s deviating considerably from the theoretical values indicated that the ROP of ε-caprolactone by complexes 2a–4g was not well-controlled, which was also judged from the broad molecular weight distributions(MWD = 1.47-2.47) of produced poly(ε-caprolactone)s. These complexes proved to be inactive toward the polymerization of rac-lactide alone. In the presence of alcohol the polymerization occurred, which was actually initiated by the decomposition species of the aluminum complex upon the treatment with isopropanol.     

Tetrahydrosalen backboned gadolinium complex as initiator for the ring-opening polymerization of ε-caprolactone

Tetrahydrosalen ligand was employed in the synthesis of gadolinium complex. The ligand was deprotoned by LiBu, and the afforded lithium salt was reacted with anhydrous GdCl3 to produce the gadolinium complex through salt metathesis. This complex was successfully used to initiate the ring-opening polymerization of ε-caprolactone. The initiation conditions in different temperature, monomer-to-initiator ratio and time were investigated. Under the condition： [ε-caprolactone]：[catalyst] = 600, 56 ℃, toluene： 2 ml, poly（ε-caprolactone） （PCL） with Mw = 11,2782 and PDI = 1.96 was achieved.     

In situ generated,tetrahydrosalen stabilized yttrium borohydride complex:Efficient initiator for the ring-opening polymerization of ε-caprolactone

In this paper,we report the preparation of a new tertrahydrosalen-stabilized yttrium complex which was employed as an initiator-precursor for the polymerization ofε-caprolactone(ε-CL) in the presence of NaBH_4 to give interesting hydroxytelechelic poly(ε-caprolactone)(PCL).The effect of[monomer]/[initiator]([CL]/[I]),temperature and time on the polymerization was investigated.It was found that under the condition:[CL]/[I]= 1200,55℃,toluene:0.5 mL,ε-CL:0.5 mL,PCL with M_w = 32,600 and PDI = 1.47 was obtai...     

Preparation of polymer brushes on attapulgite surfaces via a combination of CROP and click reaction

<正>In this work,by a combination of controlled ring-opening polymerization(CROP) and click reaction,we reported a facile and useful method to synthesize linear poly(ε-caprolactone) at attapulgite nanocomposites with well-defined structures.For this,first, the chlorine terminated attapulgite was prepared by the self-assembly of 3-chloropropyltrimethoxysiIane from the surfaces of attapulgite.And then,the terminal chlorines of modified attapulgite were substituted with azido groups.As the second step,linear propargyl-terminated poly(ε-caprolactone)(PCLs) with different molecular weights were synthesized by the CROP ofε-CL monomer in toluene with Sn(Oct)_2 as a catalyst and propargyl alcohol as an initiator.Finally,the azido-terminated attapulgites were reacted with propargyl-terminated PCLs via the click reactions.     

The copolymerization of L-lactide and ε-caprolactone using magnesium octoate as a catalyst

Copolymerizations of L-lactide （L-LA） and ε-caprolactone （ε-CL） were conducted in bulk using magnesium octoate as a catalyst. The reactivity ratios of L-LA and ε-CL were determined to be rL=23 and rc=0.22, respectively. The sequence analyses of the copolymers were performed on ^13C NMR. An increase in the reaction temperature enhances the role of transesterification and the extent of randomness.     

Block Copolymer Networks Composed of Poly(ε-caprolactone) and Polyethylene with Triple Shape Memory Properties

In this contribution, we reported a novel synthesis of block copolymer networks composed of poly(ε-caprolactone)(PCL) and polyethylene(PE) via the co-hydrolysis and condensation of α,ω-ditriethoxylsilane-terminated PCL and PE telechelics. First, α,ω-dihydroxylterminated PCL and PE telechelics were synthesized via the ring-opening polymerization of ε-caprolactone and the ring-opening metathesis polymerization of cyclooctene followed by hydrogenation of polycyclooctene. Both α,ω-ditriethoxylsilane-terminated PCL and PE telechelics were obtained via in situ reaction of α,ω-dihydroxyl-terminated PCL and PE telechelics with 3-isocyanatopropyltriethoxysilane. The formation of networks was evidenced by the solubility and rheological tests. It was found that the block copolymer networks were microphase-separated. The PCL and PE blocks still preserved the crystallinity. Owing to the formation of crosslinked networks, the materials displayed shape memory properties. More importantly, the combination of PCL with PE resulted that the block copolymer networks had the triple shape memory properties, which can be triggered with the melting and crystallization of PCL and PE blocks. The results reported in this work demonstrated that triple shape memory polymers could be prepared via the formation of block copolymer networks.     

Algorithm and application of Monte Carlo simulation for multi-dispersive copolymerization system

A Monte Carlo algorithm has been established for multi-dispersive copolymerization system, based on the experimental data of copolymer molecular weight and dispersion via GPC measurement. The program simulates the insertion of every monomer unit and records the structure and microscopical sequence of every chain in various lengths. It has been applied successfully for the ring-opening copolymerization of 2,2-dimethyltrimethylene carbonate (DTC) with δ-caprolactone (δ-CL). The simulation coincides with the experimental results and provides microscopical data of triad fractions, lengths of homopolymer segments, etc., which are difficult to obtain by experiments. The algorithm presents also a uniform frame for copolymerization studies under other complicated mechanisms.     

RELEASE OF IBUPROFEN FROM PEG-PLLA ELECTROSPUN FIBERS CONTAINING POLY(ETHYLENE GLYCOL)-b-POLY(α-HYDROXY OCTANOIC ACID) AS AN ADDITIVE

<正>Poly(α-hydroxy octanoic acid) was first used as an additive for the preparation of electrospun ultra-fine fibers of poly(ethylene glycol)-b-poly(L-lactide)(PEG-PLLA).Ibuprofen was loaded in the electrospun ultra-fine fibers.The results from environmental scanning electron microscopy(ESEM),wide angle X-ray diffraction(WAXD) and differential scanning calorimetry(DSC) demonstrated that ibuprofen could be perfectly entrapped in the fibers electrospun from PEG-PLLA usingα-hydroxy octanoic acid or PEG-b-poly(α-hydroxy octanoic acid)(PEG-PHOA) as additives.Compared with electrospun PEG-PLLA fibers which entrapped 20 wt%ibuprofen,the PEG-PLLA electrospun fibers containing PEG-PHOA exhibited integral and robust after 1 week incubated in 37℃,pH 7.4 phosphate buffer solution with 10μg/mL proteinase K.Compared with electrospun fibers without PEG-PHOA,the concentration of proteinase K in release media had less effect on the release rate of ibuprofen.An unique release profile was found from PEG-PLLA fiber after the incorporation of PEG-PHOA. Enzyme degradation experiments demonstrated that PEG-PHOA but notα-hydroxy octanoic acid monomer was the crucial factor for integrity maintenance of the electrospun fibers,which may be due to the enzyme degradation tolerance property of the PEG-PHOA polymer additive.     

Enzymatic Synthesis of a CCK-8 Tripeptide Fragment

A process for the synthesis of CCK-8 tripeptide H-Gly-Trp-Met-OH catalyzed by immobilized enzyme was reported. Enzymes were used for the formation of peptide bonds and the removal of protecting group. Starting with phenylacetyl (PhAc) glycin, N-protected dipeptide PhAc-Gly-Trp-OMe was obtained by coupling PhAc-protected glycine carboxamidomethyl ester (OCam) with Trp-OMe catalyzed by immobilized papain in buffered ethyl acetate. Then the condensation between PhAc-Gly-Trp-OMe and Met-OEtoHC1 was carried out by immobilized α-chymotrypsin catalysis in solvent free system. Basic hydrolysis was followed getting PhAc-Gly-Trp-Met-OH. The PhAc-group was removed with penicillin G amidase and H-Gly-Trp-Met-OH was obtained in an overall yield of 43.9%. The reaction conversion of tripeptide in solvent free system was strongly affected by the system of basic salts added. The influence of the support materials used to deposit enzymes and structures of acyl donor and nucleophile on the reaction was also investigated.