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1.
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.  相似文献   

2.
The bulk ring-opening polymerization (ROP) of ?-caprolactone (?-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°C. The overall conversion to poly(?-caprolactone) was more than 96% and poly(?-caprolactone) with M w of 8400 and polydispersity index of 1.13 was obtained. 1H 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.  相似文献   

3.
In this work, by a combination of controlled ring-opening polymerization (CROP) and click chemistry, we report a facile and useful method to synthesize linear poly(ε-caprolactone)@attapulgite nanocomposites with well-defined structures. For this, first, the chlorine-terminated attapulgite was prepared by the self-assembly of 3-chloropropyltrimethoxysilane 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 of ε-CL monomer in toluene with stannous octoate as a catalyst and propargyl alcohol as an initiator. The structural characteristics of the obtained linear PCLs have been determined by 1H NMR and gel permeation chromatography analysis. Finally, the azido-terminated attapulgite was reacted with propargyl-terminated PCLs via the click reaction.  相似文献   

4.
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.  相似文献   

5.
6.
Zinc alkyl cations supported by N,N-BIAN-type bidentate ligands were found to be highly active in the immortal ROP of ε-caprolactone to yield narrowly disperse and chain length-controlled poly(ε-caprolactone), whether in solution or bulk polymerization conditions.  相似文献   

7.
8.
<正>Polyolefins are an indispensable class of materials that have become the most widely produced and utilized polymers today. They are readily synthesized from cheap and abundant monomer feedstocks, such as ethylene and propylene, and are capable of achieving a vast array of thermal and mechanical properties based upon their composition and to-  相似文献   

9.
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: 2ml, poly(ε-caprolactone) (PCL) with Mw=11,2782 and PDI=1.96 was achieved.  相似文献   

10.
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.  相似文献   

11.
A series of homoleptic lanthanide guanidinate (guan)3Ln · ((C2H5)2O)n (Ln=Yb, n=1 guan=(CyN)2CNiPr2, (1); Ln=Nd, n=0, guan=(CyN)2CNiPr2, (2); (iPrN)2CNiPr2, (3); (iPrN)2CN(CH2)5, (4)); (iPr=isopropyl, Cy=Cyclohexyl) were synthesized by the reaction of THF solution of lithium guanidinate with anhydrous lanthanide trichlorides in THF in 3:1 molar ratio. The molecular structures of 2 and 3 were determined to be monomeric in solid state with a six coordinate lanthanide metal ligated by six nitrogens of three guanidinate groups. All the complexes exhibited extremely high activity for the ring-opening polymerization of ε-caprolactone and the polymerization gave the polymers with high molecular weights. The different substituents at guanidino ligands have great effect on the catalytic activity. The mechanism of the polymerization was presented.  相似文献   

12.
Design and synthesis of biodegradable stimuli-responsive polypeptides are important areas considering their promising applications in biomedical fields. This article summarizes the most recent progresses in the development of stimuli-responsive polypeptide materials prepared via ring-opening polymerization of α-amino acid N-carboxyanhydrides. We discuss the design, synthesis and structure-property correlation of emerging materials including thermo-responsive, redox-responsive, photo-responsive and biomolecule responsive polypeptides. Considering the unique structural features of amino acids, we try to emphasize that the thermo-responsive properties not only depend on the amino acid structure but also rely on the secondary structures of polypeptides. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013  相似文献   

13.
This study examined the production of protein hydrolysates with controlled composition from cheese whey proteins. Cheese whey was characterized and several hydrolysis experiments were made using whey proteins and purified β-lactoglobulin, assubstrates, and trypsin and α-chymotrypsin, as catalysts, at two tem peratures and several enzyme concentrations. Maximum degrees of hydrolysis obtained experimentally were compared to the theoretical values and peptide compositions were calculated. For trypsin, 100% of yield was achieved; for α-chymotrypsin, hydrolysis seemed to be dependent on the oligopeptide size. The results showed that the two proteases could hydrolyze β-lactoglobulin. Trypsin and α-chymotrypsin were stable at 40°C, but a sharp decrease in the protease activity was observed at 55°C.  相似文献   

14.
The stoichiometric reactions of 2-(2,6-R-phenylimino)quinolin-8-ol (L1-L5, L1: R = Me, L2: R = Et, L3: R = (i)Pr, L4: R = Cl, L5: R = F) with Me(3)Al afforded the dimeric aluminium complexes [Me(2)AlL](2) (1-5) in good yields. By contrast, stoichiometric reactions of 2-(1-(2,6-R-phenylimino)propyl) quinolin-8-ol (L6-L10, L6: R = Me, L7: R = Et, L8: R = (i)Pr, L9: R = Cl, L10: R = F)) with Me(3)Al gave the mononuclear aluminium complexes Me(2)AlL (6-10) accompanied with by-products of the form Me(2)AlL·Me(3)Al (11-15). All methylaluminium complexes were characterized by NMR spectroscopy, elemental analysis, and the molecular structures of complexes 3, 6 and 8 were determined by single-crystal X-ray diffraction. Aluminium compounds 1-5 possessed negligible activity towards the ring-opening polymerization of ε-caprolactone either in the presence or absence of BnOH. In contrast, in the presence of BnOH, the mononuclear aluminium compounds 6-10 could efficiently initiate the ring-opening polymerization of ε-caprolactone; the polymerization proceeded in a living manner.  相似文献   

15.
A series of aryloxy compounds and benzyloxy derivatives of Zr(IV) were synthesized in good yields and purity, employing the alcoholysis route. They were completely characterized with different spectroscopic techniques and single crystal X-ray diffraction. A high degree of fluxional behavior of these compounds was understood through variable-temperature NMR studies. X-ray diffraction studies prove that these compounds exist as dimers in the solid state. They are potent catalysts for the ring-opening polymerization of ?-caprolactone (CL) and δ-valerolactone (VL) resulting in high polymers with good number average molecular weights (Mn) and molecular weight distributions (MWDs). The degree of control in these polymerizations was found to be superior with the zirconium compounds when compared with the titanium analogues. The rate of polymerization was found to be slower for the zirconium compounds, as realized from kinetic studies. Analysis of the MALDI-TOF and 1H NMR spectra of low molecular weight oligomers of CL synthesized using these compounds reflect that these polymerizations proceed by the activated monomer mechanism.  相似文献   

16.
Reaction of quinolin-8-amine with 1H-pyrrole-2-carbaldehyde or 5-tert-butyl-1H-pyrrole-2-carbaldehyde catalyzed by HCO2H forms N-((1H-pyrrol-2-yl)methylene)quinolin-8-amine (≡ HL, 3a) or N-((5-tert-butyl-1H-pyrrol-2-yl)methylene)quinolin-8-amine (≡ HL′, 3b). Treatment of 3a and 3b respectively with AlMe3 or AlEt3 in toluene affords corresponding aluminum complexes LAlMe2 (4a), L′AlMe2 (4b) and LAlEt2 (4c). Reaction of 3a and 3b with an equivalent of ZnEt2 in toluene generates L2Zn and L′2Zn, respectively. A related compound N-((1H-pyrrol-2-yl)methylene)-2-(3,5-dimethyl-1H-pyrazol-1-yl)benzenamine (≡ HL″, 7) was prepared by reaction of 2-(3,5-dimethyl-1H-pyrazol-1-yl)benzenamine with 1H-pyrrole-2-carbaldehyde in the presence of HCO2H. Reaction of 7 with AlMe3 gives L″2AlMe (8), and with ZnEt2 yields L″2Zn (9). All new compounds were characterized by NMR spectroscopy and elemental analysis. The structures of complexes 4b, 5b and 8 were additionally characterized by single crystal X-ray diffraction analyses. Complexes 4a-4c, and 8 were proved to be active catalysts for the ring-opening polymerization (ROP) of ?-caprolactone (?-CL) in the presence of BnOH. The kinetic study of the polymerization reactions catalyzed by 4a and 8 was performed.  相似文献   

17.
The synthesis of α,β-difunctionalized dehydropiperidines has been accomplished using α-halo-β-sulfonyl eneformamides. This outcome is achieved through sequential regioselective Cβ-alkylative desulfonation and Cα-palladium-catalyzed cross-coupling. In most cases, high yields of the vicinally functionalized eneformamides are obtained.  相似文献   

18.
α-Chloro-1,2-diones and α-fluoro-1,2-diones were prepared from the corresponding α-chloroaldimines by a sequence of reactions involving cyanation to α-cyanoenamines, α-halogenation to form α-chloro- or α-fluoroimidoyl cyanides and addition of organolithium reagents across the nitrile moiety, followed by acidic hydrolysis. All steps are straightforward and occur without side reactions finally leading to regiospecifically chlorinated and fluorinated 1,2-diones in good yields.  相似文献   

19.
Two types of hybrid acrylic nanoparticles based on biodegradable and biocompatible polymers, cellulose ester and poly(ε-caprolactone), were produced via miniemulsification through high-pressure homogenization. An efficient emulsification procedure was first devised to yield high-solids-content polymer–monomer waterborne miniemulsions, and the fundamental parameters governing the stability of these composite miniemulsions were assessed. In addition, strategies to control the droplet size were investigated upon varying several experimental parameters such as the interfacial tension between the organic and the aqueous phase, the organic phase viscosity and the nature/concentration of surfactant. A series of thermally initiated polymerizations were then performed to produce nanosized hybrid particles.  相似文献   

20.
Two dinuclear aluminum alkyl complexes supported by a piperazidine-bridged bis(phenolato) group were prepared, and both complexes exhibited extremely high activity for the ring-opening polymerization of ε-caprolactone. In the presence of benzyl alcohol (BnOH), the polymerization accelerated dramatically.  相似文献   

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