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

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.     

Synthesis,structure and catalytic activity of complexes [Ln(EDBP)_2(DME)Na(DME)_3](Ln=Er,Yb,Sm) for ring-opening polymerization of ε-caprolactone

Discrete ion-pair complexes [Ln(EDBP)2(DME)Na(DME)3] [Ln=Er (1), Yb (2), Sm (3)] have been synthesized by the reaction between sodium salt of 2,2'-ethylidene-bis(4,6-di-tert-butylphenol)(EDBPH2) and Ln(BH4)3·3THF (Ln=Er, Yb, Sm) followed by centrifugation and recrystalization. The complexes were characterized by elemental analysis and FT-IR, and the bonding model of these compounds was confirmed by X-ray single crystal diffraction for complex 1. It was found that four O atoms in two biphenol ligands as well...     

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 Highly Branched Poly（ε-caprolactone） by Self-condensing Atom Transfer Radical Polymerization of Macroinimers

Fréchet et al.1 in 1995 prepared hyperbranched vinyl polymers by the technique named self-condensing vinyl polymerization (SCVP) of initiator-monomers (“inimers”) having the general structure AB*, where A stands for a double bond and B* for an initiati…     

Synthesis,characterization of neodymium chloride complex of amine-bis(phenolate) ligand and its reactivity in the ring-opening polymerization of ε-caprolactone

The neodymium chloride complex[Nd(ONN'O)Cl(THF)]_2 supported by amine-bis(phenolate) ligand was synthesized by the metathesis reaction of anhydrous NdCl_3 with Li_2(ONN'O)[H_2ONN'O = Me_2NCH_2CH_2N(CH_2-3-Bu_2~t-5-Me-C_6H_2OH)_2]in high yield.X-ray structural determination shows[Nd(ONN'O)Cl(THF)]_2 complex consists of two seven-coordinate neodymium centers linked throughμ-Cl bridges.And this complex was successfully used to initiate the ring-opening polymerization(ROP) ofε-caprolactone.     

In situ evaluation of cell cultivation on dynamically changed poly(ε-caprolactone) film caused by enzymatic degradation

In situ evaluation of cell cultivation on degrading poly(ε-caprolactone) (PCL) films was studied.New culture surroundings were constructed for cell growth by using PCL films as substrates and adding Pseudomonas cepacia lipase to accelerate biodegradation of PCL films.MTT experiments for 10 h indicated the low cytotoxicity of lipase solution with concentration up to 0.2 mg/mL for MG-63 cells growth on PCL films.With the optimized lipase concentration and degradation time,we studied cell growth behavior on dy...     

Aluminum and zinc complexes supported by functionalized phenolate ligands: Synthesis, characterization and catalysis in the ring-opening polymerization of ε-caprolactone and rac-lactide

A series of aluminum and zinc complexes supported by functionalized phenolate ligands were synthesized and characterized. Reaction of 2-(3,5-R₂C₃N₂)C₆H₄NH₂ (R = Me, Ph) with salicylaldehyde or 3,5-di-tert-butylsalicylaldehyde afforded 2-((2-(1H-pyrazol-1-yl)phenylimino)methyl)phenol derivatives 2a-2d. Treatment of 2a-2d with an equiv. of AlR²₃ (R² = Me, Et) gave corresponding aluminum aryloxides 3a-3e, while reaction with an equiv. of ZnEt₂ afforded zinc aryloxides 4a-4d. Treatment of 2c with 0.5 equiv. of ZnEt₂ formed diphenolato zinc complex 5. All new compounds were characterized by ¹H and ¹³C NMR spectroscopy and elemental analyses. The structures of complexes 3a, 4a and 5 were further characterized by single crystal X-ray diffraction techniques. The catalytic activity of complexes 3-5 toward the ring-opening polymerization of ε-caprolactone was studied. The zinc complexes (4a-4d) exhibited higher catalytic activity than the aluminum complexes (3a-3e). The diphenolato zinc complex 5 showed lower catalytic activity than the ethylzinc complexes 4a-4d. The aluminum complex (3b) is inactive to initiate the ROP of rac-lactide, while the zinc complex (4d) is active initiator for the ROP of rac-lactide, giving atactic polylactide.     

Resolution of α-cyclohexyl-mandelic acid enantiomers by two-phase (O/W) recognition chiral extraction

This paper presents a new chiral separation technology: two-phase (O/W) recognition chiral extraction. Distribution behavior of α-cyclohexyl-mandelic acid enantiomers was studied in the extraction system with D(L)-isobutyl tartrate in 1,2-dichloroethane organic phase and β-CD derivatives in aqueous phase, and the influence of the kind and concentration of extractant and pH on extraction performance was investigated. The experimental results indicate that two-phase (O/W) recognition chiral extraction is of strong chiral separation ability. HP-β-CD, HE-β-CD and Me-β-CD have higher recognition ability for S-CHMA than that for R-CHMA, among which HP-β-CD has the strongest ability; whereas, D-isobutyl tartrate has reversed recognition ability for them. In the extraction system containing HP-β-CD and D-isobutyl tartrate, e.e.% of S-CHMA in aqueous phase reached 27.6% by one stage extraction, and the distribution ratio for R-CHMA(kR) and for S-CHMA(kS) and separation factor (α) are 2.44, 0.89 and 2.49, respectively. Meanwhile, pH and concentration of extractant have great effects on chiral separation ability. Two-phase (O/W) recognition chiral extraction has great significance for preparative separation of racemic compounds.     

The preparation of terephthalic acid by solvent-free oxidation of p-xylene with air over T（p-C1）PPMnC1 and Co（OAc）2

An attempt has been made to prepare terephthalic acid（TPA） by solvent-free oxidation of p-xylene（PX） with air over tetra（pchlorophenylporphinato） manganese chloride（T（p-Cl）PPMnCl） and cobalt acetate.The co-catalysis between T（p-Cl）PPMnCl and Co（OAc）₂ has been discovered under solvent-free conditions.TPA yield could be increased significantly when T（p-Cl）PPMnCl and Co（OAc）₂ were used together.The addition of T（p-Cl）PPMnCl into the reaction mixture over Co（OAc）₂ significantly accelerated the rate-determining step of the oxidation process of PX to TPA.The effect of temperature on reaction was also investigated.