Miscibility and Crystallization in Binary Crystalline Blends of Poly(butylene terephthalate) with Poly(butylene terephthalate-e-caprolactone)

Poly(butylene terephthalate)/poly(butylene terephthalate-e-caprolactone) is a new A/AxB1-x binary crystalline blend with intra-molecular repulsion interaction. Using the mean-field binary interaction model, the value of interaction parameter between the butylene terephthalate and caprolactone structural unit was first reported to be 0.305. This blend exhibited different crystallization behavior from a typical homopolymer/copolymer blend, which was carefully investigated by di?erential scanning calorimetry. It was found that poly(butylene terephthalate-e-caprolactone) copolymers have a great effect on the pure poly(butylene terephthalate) chain mobility and poly(butylene terephthalate) crystalline lattice packing. In the meantime, the crystallization of butylene terephthalate segments in copolymers was restricted by the previously formed poly(butylene terephthalate) crystallites. The two constituents for blending can not form a co-crystal in the range of composition even if they have the same butylene terephthalate unit. It can be concluded that longersegments in a copolymer would be beneficial for the formation of a co-crystal in blends.     

Sequential analysis of polyesters by stepwise chemical degradation: Application to oligo and poly(alkylene terephthalate)s

A specifically tailored reagent was used to label the hydroxyl end groups of poly(ethylene/butylene terephthalate), which is synthesized by transesterification of the corresponding homopolymers. The terminal monomeric unit was then eliminated, together with the attached label, as a low molecular-weight cyclic compound. Specially synthesized reference compounds containing ethylene terephthalate and butylene terephthalate units enabled the terminal monomeric unit to be identified as butylene terephthalate, although the copolymer showed an otherwise random distribution. Despite the practical and theoretical reasons that restrict this sequential degradation to the last monomeric unit for polymers, the principle can be used in a wider range of applications if combined with selective degradation and separation by means of HPLC, which results in chemically uniform oligomers. The ultimate and penultimate monomeric units of ethylene/butylene terephthalate type oligomers can be identified using the cyclodegradation procedure described here. © 1993 John Wiley & Sons, Inc.     

Transition metal-directed self-assembly of calix[4]arene based dithiocarbamate ligands

The transition metal-directed self-assembly of dithiocarbamate ligand functionalized upper and lower rim calix[4]arenes affords novel dimeric bimetallic bis(calix[4]arene) species as determined by a combination of analytical methods including X-ray crystallography. An exception is a zinc(II) dithiocarbamate upper rim calix[4]arene assembly which is monomeric in nature. Electrochemical investigations reveal the bimetallic copper(II) bis(calix[4]arene) systems can electrochemically sense dihydrogen phosphate and carboxylate anions via significant cathodic perturbations of the respective copper(II)/(III) dithiocarbamate oxidation wave.     

Electrochemical study of triphenyltin piperidyl dithiocarbamate

The reduction of triphenyltin piperidyl dithiocarbamate in acetone has been investigated using d.c. polarography and cyclic voltammetry. Polarographic reduction yielded four well-defined waves, two of which were diffusion-controlled and two of which appear to represent adsorption processes. The cyclic voltammetric study yielded results in close agreement with the polarographic data. Results appear to indicate the release of the dithiocarbamate moiety, followed by reduction to form the triphenyltin radical, which undergoes dimerization, as well as reduction to the triphenyltin anion. For comparison, the polarographic reduction of triphenyltinchloride was investigated. A mechanism similar to that proposed by earlier authors for the polarographic behaviour of tributyltin oxide was found. For convenience, the more commonly used terminology of piperidyl dithiocarbamate is used throughout the paper, in place of (piperidine-1-carbodithioato) triphenyltin (IV).     

Thermal properties of poly(butylene oxalate) copolymerized with azelaic acid

Poly(butylene oxalate) (PBO) and poly(butylene oxalate/butylene azelate) random copolymers (PBOBAz) of various compositions were synthesized in bulk and characterized in terms of chemical structure and thermal properties. The thermal behavior was examined by thermogravimetric analysis and differential scanning calorimetry. All copolymers were found to be partially crystalline and thermally stable up to about 290 °C. The main effect of copolymerization was a decrease in melting and glass transition temperatures with respect to PBO homopolymer. The pure crystalline phase characteristic of PBO was evidenced by means of X-ray measurements in all the copolymers under investigation. The fusion temperatures appeared to be well correlated to composition by Baur's equation.Amorphous samples were obtained after melt quenching and showed a monotonic decrease of glass transition temperatures as the content of the flexible butylene azelate units is increased. Fox equation described well the T_g-composition data. Lastly, the overall crystallization rate of PBO was found to decrease regularly with increasing butylene azelate unit content.     

不同链结构的双酚A聚碳酸酯对脂肪族聚碳酸酯结晶行为的影响

脂肪族聚碳酸酯(APC)是一类可降解的高分子材料,因其生产工艺可固定温室气体的主要成分二氧化碳,这种可降解塑料得到了越来越多的关注.作为半结晶高分子材料,脂肪族聚碳酸酯的结晶性能和结晶结构对成型加工、力学性能和降解性能具有重要的影响.借助热分析(示差扫描量热仪DSC)和形态学观察(偏光显微镜POM)两种方法研究了不同链结构的双酚A型聚碳酸酯对半结晶脂肪族聚碳酸酯——聚碳酸1,4-丁二醇酯结晶动力学行为的影响.实验发现质量分数1%的双酚A聚碳酸酯的加入促进了聚碳酸1,4-丁二醇酯的成核,但不同链结构的双酚A聚碳酸酯对其晶体生长具有相反的作用,线形双酚A聚碳酸酯(PC-L)能够促进晶体生长,而支化双酚A聚碳酸酯(PC-B)则抑制晶体生长.用原子力显微镜在轻敲模式下研究了两种双酚A聚碳酸酯与APC共混物熔融状态下的相结构,发现熔体结构的不同是导致两种共混物与纯的APC相比,结晶速率呈现相反变化趋势的主要原因.     

Fragmentation patterns of novel dithiocarbamate derivatives with pharmaceutical activity under electrospray ionization tandem mass spectrometry conditions

The fragmentation patterns of a novel series of dithiocarbamate derivatives with pharmaceutical activity were investigated by positive ion electrospray ionization mass spectrometry in conjunction with tandem mass spectrometry (ESI-MS(n)). In the gas phase, the dithiocarbamate protonated molecules containing the piperazinium moiety undergo losses of bromide to form the piperazinium cation by ionization, followed by subsequent losses of methyl bromide, ring opening and rearrangement of piperazinium. Furthermore, the dithiocarbamate derivatives and their intermediates both undergo cleavage of the C-S bond to produce two common fragment ions. The different fragmentation observed for these compounds facilitated their identification and could be valuable in the further study of their metabolic pathways as prodrugs.     

Diorganotin(IV) dithiocarbamate complexes as chromogenic sensors of anion binding

One dinuclear chlorodiphenyltin (IV) dithiocarbamate complex (1) and four mononuclear complexes of general formula Ph₂Sn(S₂CNR)Cl (2, 3, 5, and 6) have been synthesized and characterized both in solid-state and solution. X-ray structures for complexes 1, 3 and 6 demonstrated a five-coordination geometry around of tin atoms, in which dithiocarbamate ligand chelates asymmetrically the metal center. As shown by ¹¹⁹Sn NMR spectroscopy, five-coordination geometry observed in the solid-state remains in solution. The stability of these chlorodiphenyltin(IV) dithiocarbamate complexes in the presence of biologically relevant anions such as acetate, dicarboxylates of general formula ^?OOC-(CH₂)_n-COO^? (n = 2–8), dihydrogenphosphate, hydrogensulfate, and halides has been examined in acetonitrile solutions. For all of these organotin(IV) complexes the displacement of the coordinated ligands (i.e., chloride and dithiocarbamate) from the organotin(IV) moiety occurred in the presence of monoanions like acetate, dihydrogenphosphate, hydrogensulfate and fluoride. A stepwise mechanism for ligand exchange is proposed based on UV–Vis, ¹H, ¹³C and ¹¹⁹Sn spectroscopic data, as well as mass spectrometry. From UV–Vis titration experiments it was found that dicarboxylates with small spacers like malonate and succinate, acted differently in the exchange of the dithiocarbamate group in comparison to other monoanionic O donor ligands or dicarboxylates with longer chains, perhaps by following an intramolecular displacement of the coordinated ligand.The lability of these organotin(IV) dithiocarbamate compounds in solution hampers their use as stably host for anions, however, by taking advantage of the intrinsic chromogenic properties of free dithiocarbamate anions, or by attaching dithiocarbamate groups to well-known fluorescent moieties such as antracene, these complexes can sense the presence of O-donor anions at very low concentrations by displacement of the metal-coordinated dithiocarbamate.     

A modular synthesis of dithiocarbamate pendant unnatural α-amino acids

Unnatural α-amino acids containing dithiocarbamate side chains were synthesized by a one-pot reaction of in situ generated dithiocarbamate anions with sulfamidates. A wide range of these anions participated in the highly regio- and stereo-selective ring opening of sulfamidates to produce the corresponding dithiocarbamate pendant α-amino acids in high yields.     

Synthesis and characterization of poly([3H]-thiazole-2-thione)s

The reaction of dithiocarbamate salts with α-haloketones is extended to (i) dithiocarbamate salts with bis(α-haloketones), (ii) bis(dithiocarbamate salts) with α-haloketones, and (iii) bis(dithiocarbamate salts) with bis(α-haloketones). Both (i) and (ii) give bis([3H]-thiazole-2thiazole-2-thiones) in high yields, and (iii) gives the corresponding polymers which are described and characterized.     

Synthesis and transformations of 2,6-bis(1,1-dimethylethyl)-4-[2-(thiazolyl)ethenyl]phenols

(Thiazolylethenyl)phenols were prepared as potential antiinflammatories by reaction of thiazole 4- and 5-acetic acid derivatives with 3,5-di-tert-butyl-4-hydroxybenzaldehyde. Alternatively, an arylethenyl methyl ketone was brominated and the bromoketone product reacted with methyl dithiocarbamate, ammonium dithiocarbamate, or thiourea.     

The enzymatic degradation of commercial biodegradable polymers by some lipases and chemical degradation of them

Biodegradable polyesters, poly(butylene succinate adipate) (PBSA), poly(butylene succinate) (PBS), poly(ethylene succinate) (PES), poly(butylene succinate)/poly(caprolactone) blend (HB02B) and poly(butylene adipate terephthalate) (PBAT), were evaluated about degradability for enzymatic degradation by lipases and chemical degradation in sodium hydroxide solution. In enzymatic degradation, PBSA was the most degradable by lipase PS, on the other hand, PBAT containing aromatic ring was little degraded by eleven kinds of lipases. In 1N NaOH solution, degradation rate of PES with ethylene unit was extremely fast, in comparison with other polyesters. Interestingly the degradation rate of PBSA in enzymatic degradation by lipase PS was faster than in chemical degradation.     

Synthesis and characterization of group 12 complexes of N,N-methyl phenyl-N,N-butyl phenyl dithiocarbamate

Zn(II), Cd(II), and Hg(II) complexes of N-methyl-N-phenyl dithiocarbamate (L¹) and N-butyl-N-phenyl dithiocarbamate (L²) formulated as ML¹L² have been synthesized and characterized by elemental analysis, FT–IR, ¹H- and ¹³C-NMR spectroscopic techniques. Single-crystal X-ray structures of the Zn(II) and Hg(II) complexes are also reported. X-ray crystal structures revealed that in the zinc(II) complex, the dithiocarbamate is chelating and bridging, forming eight-member rings, while the Hg complex is monomeric with bidentate dithiocarbamate. In both complexes, the metals are in distorted tetrahedral geometry and the methyl and butyl groups of the dithiocarbamates exhibit compositional disorder between two positions.     

Mass spectral fragmentation of metal dithiocarbamate complex salts

A summary of the mass spectra of metal dithiocarbamate complex salts (ML₂ and ML₃) is presented. Only divalent metal dithiocarbamate ions without an electronic configuration containing an inert s-orbital electron pair exhibited both expulsion of a ligand radical (L) and the neutral even electron species (L–H) generated from the ligand via hydrogen transfer to the metal-containing fragment ion. Divalent metal dithiocarbamate ions can be generated either by direct electron impact ionization of gas phase ML₂ molecules or ionization of ML₃ molecules followed by loss of a ligand radical. A highly stable sp² hybridized, gas phase ion of a monobidentate lead dithiocarbamate complex is proposed.     

Preparation and Research of Butylene Fipronil Microencapsulation by Layer-by-Layer Polyelectrolyte Self-Assembly

This paper introduced the preparation of butylene fipronil-loaded microcapsules with oppositely charged chitosan and sodium lignosulfonate as shell materials. It summed up the performance, preparation methods of microcapsules and sketched the application status of layer-by-layer self-assembly. The whole progress of the preparation was controlled by measuring the change of the Zeta potential and the morphology of microcapsules was characterized by microscope and SEM. Entrapment efficiency and slow release performance of the microcapsule were determined as measurement index. The results of experiment showed that the surface of the microcapsules was rougher than the butylene fipronil particles. With the increasing layer number of assembly, the entrapment efficiency reduced while the slow release performance increased. After encapsulation, the photodegradation rate of butylene fipronil under the UV decreased obviously. Results showed that the condition of preparation was the best when NaCl with the concentration of 0.5 mol/L and PH of 5.0.     

PBS基生物降解材料的研究进展

PBS(聚丁二酸丁二醇酯 )是一种具有良好生物降解性的聚酯塑料。本文简述了PBS的基本特性、降解机理和制备方法 ,对各种PBS基生物降解材料的特性进行了分析 ,介绍了PBS基生物降解材料的研究进展     

Determination of Pd and Co as Their Dithiocarbamate Complexes by Liquid Chromatography without Solvent Extraction

Abstract

High performance reverse-phase liquid chromatography with UV-detection can be used to determine trace levels of Pd and Co as their dithiocarbamate complexes by direct injection of aqueous acetonitrile solutions of the metal containing dithiocarbamate. An excess of ligand, at least four times that required to form the neutral metal complex, was necessary for complete metal-complex formation. The presence of other metal species and the solution acidity depleted the amount of ligand available for complexation. Detection limits for Pd(II) and Co(III) from aqueous solution as their dithiocarbamate complexes were 2.7 ng/mL and 9.5 ng/mL respectively. Trace levels of Pd in Platinum powder (62 ug/g)have been determined. A solution of cobalt platonic chloride was analyzed for cobalt content.     

Preparation and characterization of aliphatic/aromatic copolyesters based on 1,4-cyclohexanedicarboxylic acid

A series of biodegradable aliphatic/aromatic copolyesters, poly(butylene terephthalate)-co-poly(butylene cyclohexanedicarboxylate)-b-poly(ethylene glycol) (PTCG), were prepared by a two-step melt polycondensation method and characterized by means of GPC, FTIR, NMR, DSC, TGA, etc. The effects of aliphatic ester content on the physical, mechanical and thermal properties, as well as in vitro and in vivo degradation behaviors were investigated. The decrease in mechanical strength was observed with an increase in poly(butylene cyclohexanedicarboxylate) (PBC) molar fraction. DSC results showed one melting point and two glass transition temperatures in all samples, and the melting temperature was found to go down gradually as more cyclohexanedicarboxylic acid (CHDA) was added. During the in vitro and in vivo degradation processes, erosion of the surface was dominant as evidenced by scanning electron microscopic observations. The copolyesters containing many CHDA units were featured by the higher water uptake and faster degradation due to much richer amorphous phase within them.     

新型成膜电解液添加剂亚硫酸丁烯酯的电化学行为

合成制备了一种新的环状亚硫酸酯类有机溶剂——亚硫酸丁烯酯(BS). 量子化学计算结果表明, 亚硫酸丁烯酯有机溶剂分子的总能、LUMO值比碳酸丙烯酯有机溶剂的低, 具有较强的得电子能力, 不易被氧化. 其作为添加剂与碳酸丙烯酯(PC)混合应用于锂离子电池中, 可有效地抑制PC在石墨电极中的共插入, 能显著改善循环性能.