Polylactones. 13. Transesterification of Poly(L-Lactide) with Poly(Glycoude), Poly(β-Propio-Lactone), and Poly[ε -Caprolactone)

Homogeneous blends of poly(L-lactide) (M _n = 30 000 to 40 000) and poly(β-propiolactone) or poly(ε-caprolactone) were prepared in solution. The solvent-free blends were subjected to transesterification catalyzed by means of methyl triflate, triflic acid, boron trifluoride, or tributyltin methoxide at 100 or 150°C. At 100°C, transesterification was barely detectable even after 96 h. When poly(β-propiolactone) was used as the reactant at 150°C, degradation was faster than transesterification regardless of the catalyst. The same negative result was obtained for heterogeneous blends of poly(L-lactide) and poly(glycolide). In the case of poly(ε-caprolactone), copolyesters with slightly blocky sequences were obtained with tributyltin methoxide as catalyst, whereas the acidic catalysts caused rapid degradation. The copolyesters were characterized by means of ¹H-NMR spectroscopy with regard to their molar composition, by means of ¹³C-NMR spectroscopy with regard to their sequences, and by means of differential scanning calorimetry with regard to crystallinity.     

Thermal Degradation of Poly(ε-caprolactone), Poly(L-lactic acid) and their Blends with Poly(3-hydroxy-butyrate) Studied by TGA/FT-IR Spectroscopy

Summary: The thermal degradation behavior of poly(ε-caprolactone) (PCL) and poly(L-lactic acid) (PLA) have been studied in different environment. It was found that these polymers undergo completely different degradation processes in nitrogen and oxygen atmosphere. In oxygen environment PCL and PLA mainly decompose to CO₂, CO, water and short-chain acids. In nitrogen atmosphere PCL releases 5-hexenioc acid, CO₂, CO and ε-caprolactone, whereas PLA decomposes to acetaldehyde, CO₂, CO and lactide. The polymer blends of poly(3-hydroxybutyrate) (PHB) with PCL and PLA decompose similar to the individual homopolymers with crotonic acid as the initial decomposition product of PHB.     

Thermal Decomposition of Polyisoprene,Poly(p-isopropyl α-Methylstyrene), and Poly(isoprene/p-isopropyl α-Methylstyrene)

Thermal decompositions of polyisoprene, poly(p-isopropyl α-methylstyrene) (PPIPαMS), and poly(isoprene/p-isopropyl α-methylstyrene) (sample M-32) were carried out at various temperatures in the range 200–340° C in a differential thermo-gravimetric apparatus. The undecomposed polymers as well as their decomposed residues were analyzed by gel-permeation chromatography (GPC), infrared spectroscopy (IR), and nuclear magnetic resonance (NMR). Based on the changes observed in the distribution of molecular weights, depolymerization is the predominant step in the decomposition of PPIPAMS and polymer M-32, whereas random scissions predominate in the case of polyisoprene. The combined data of GPC, IR, and NMR indicate that only interchain reactions leading to the formation of cyclized products are present in the decomposition of polyisoprene while interchain as well as intrachain reactions are operative in the case of polymer M-32.     

Synthesis of Poly[（3-octanoylpyrrole-2,5-diyl）-p-nitrobenzylidene] and Its Third-order Nonlinear Optical Property

Introduction Nonlinearoptical(NLO)organicpolymers havereceivedincreasingattentionbecauseoftheir excellentbehaviorandgoodprospectsforapplica- tiontohightechnologiessuchasopticalcommuni- cation,highdensityopticalstorageandall-optical informationprocess[1_4].Thepoly[heteroarylene- methines]andtheirderivativesareregardedaspo- tentiallyapplicativeNLOmaterials[5_8],buttheir solubilityandfilm-formingperformancearenot goodwhichisabottleneckproblemfortheapplica- tionofthesepolymers.Inthisstudy,anovel…     

Adsorptive Stripping Voltammetric Study of the Enhancement of Copper(Ⅱ) by Poly(vinyl alcohol), Starch and Polyallylamine

l.IntroductionAsalatelydeveloPedsensihveandsimPleelectroanalghcalmethod,adsorptivedrippingvoltanUneto'(AdSV)receivesincreasingattenhonIl,2a].lnorgamcionscanbedetetrinedincomPlexformb}'AdSV,andmoStligandsusedaresmal1orgtricmoleculeswhichcanbeadsoIbedonthesdriceofelectrodereadily[2b]fforinStance,beryllonIIIisfitforthedetenTiltalonofboron[31.AJthoughwater-solublePOlyInerssuchasPOly(vinylalcohol)WVA)areusedasenhancingreagentSinvoltaInInetryformetalcomPlexesofotherligands[4],therearenor…     

Microwave-assisted Solvothermal Synthesis of YF_3∶Yb~(3 ),Tm~(3 ) Nanobundles

Recently,considerable attention has been paid to the synthesis and research of various rare-earth(RE) doped fluoride nanomaterials because of their high refractive index and appropriate phonon energy,which have potential applications in optics,optoelectronics,microelectronics,and tribology[1].     

Raman Spectroscopic Study of the Conformation and Melting of Poly(dG) · Poly(dC) and Poly(dG-dC) · Poly(dG-dC) in Aqueous Solution

Raman spectroscopic measurements on aqueous solutions of poly(dG) · poly(dC)indicate that the conformation of the polynucleotides in this double helicalcomplex are distributed between the A and B types at room temperature, the Aform being predominant at –15°C and decreasing progressively upon raising thetemperature to 65°C. A reversible pretransition has been found in this complexnear 70°C. Modifications in the spectra at this temperature indicate no majorconformational changes, but rather suggest altered base pairing and hydration ofthe carbonyl groups, accompanied by a slight distortion of the double helix,resulting in a slightly reduced stacking of the cytosine bases. Measurements inself-pressurized solutions of the complex at high temperature show that it meltsat 103°C in 0.1M NaCl solution (107°C in 0.5M NaCl). These values are somewhatlower than those we have determined in the same manner for the complexpoly(dG-dC) · poly(dG-dC): 117°C in 0.1M MgCl₂ and 113°C or higher in 0.1MNaCl solution.     

Crystallization Behavior of Poly(3-hydroxybutyrate) (PHB), Poly(ε-caprolactone) (PCL) and Their Blend (50:50 wt.%) Studied by 2D FT-IR Correlation Spectroscopy

Variable-temperature FT-IR spectra of poly(3-hydroxybutyrate) (PHB), poly(ε-caprolactone) (PCL) and a PHB/PCL (50:50 wt.%) blend were analyzed by two-dimensional correlation spectroscopy (2DCOS). For this purpose the ν(CO) region was employed to characterize in some detail the crystallization behavior of the investigated polymer systems during cooling from the melt. The asynchronous 2D correlation spectra clearly captured the existence of three components in the crystallinity-sensitive region of the CO stretching mode for PHB and PCL, respectively: a well-ordered, an inter-mediate and a less ordered crystalline state. Furthermore, by 2DCOS application a sequential order of the observed structural changes could be proposed for the whole temperature range during the crystallization of both polymers. In the case of the PHB/PCL (50:50 wt.%) polymer blend, we have split up the spectral data set in the sub-sets between 200–120 °C and 70–30 °C for a more detailed 2DCOS analysis. In this way we could separate the crystallization process of PHB and PCL in the polymer blend.     

Structural Characterization of Poly(α-Fluoroacrylonitrile) and Poly(Ethyl α-Fluoroacrylate)

Abstract

Monomers α-fluoroacrylonitrile (FAN) and ethyl α-fluoroacrylate (EFA) and homopolymers poly(α-fluoroacrylonitrile) (PFAN) and poly-(ethyl α-fluoroacrylate) (PEFA) have been synthesized and spectroscopi-cally characterized in detail for the first time. The ¹³C- and ¹⁹F-NMR spectroscopic results are reported, and the results are correlated to the tacticity and microstructure of both homopolymers. The major portion of the polymers is atactic. TGA analysis of PFAN indicates that the polymer is stable to about 200°C with subsequent loss of HF. PEFA is stable to 300 °C. Molecular weights determined by intrinsic viscosity (M_v ) are found to be about 130,000 for PFAN, and GPC analysis of PEFA indicates a molecular weight (M_n ) of about 36,000. Dielectric permittivities (ε) for PFAN and PEFA were determined to be 8.9 and 4.0, respectively, at 50 Hz.     

Über die Identifizierung der Lokalanaesthetica (L-A) Butacain (1), Butethamin (2), Chloroprocain (3), Dyclonin (4), Äthylaminobenzoat (5), Lidocain (6), Meprylcain (7), Metalbutethamin (8), Metabutoxycain (9), Naepain (10), Parethoxycain (11), Piperocain (12), Procain (13), Proparacain (14), Propoxycain (15) und Tetracain (16)

Analytical and Bioanalytical Chemistry -     

Crystallization of Poly(ethylene adipate) within γ-Phase Poly(vinylidene fluoride) Matrix

The effects of PEA on the γ-phase PVDF crystal structure and the crystallization of PEA within the pre-existing γ-phase PVDF spherulites have been investigated by optical microscopy(OM), infrared spectroscopy(IR) and scanning electron microscopy(SEM). The results demonstrate that the γ-phase PVDF spherulites consist of the lamellae exhibiting a highly curved scroll-like morphology and develop preferentially in PEA-rich blend. With increasing PEA concentration, the scroll diameter increases and the scrolls are better separated from each other. PEA crystallizes first in the interspherulitic region and transcrystalline layer develops. Subsequently, the transcrystalline layer of PEA continues to grow within the γ-phase PVDF spherulites, e.g., in the region between the scrolls, until impinging on other PEA transcrystalline layers or spherulites. The crystallization kinetics results indicate that the growth rate of PEA crystals in the intraspherulitic region of γ-phase PVDF shows a positive correlation with content of PEA, but a negative one with the crystallization temperature of γ-phase PVDF.     

二-(2,4,4-三甲基戊基)膦酸浸渍树脂分离Tb~(3 ),Dy~(3 ),Ho~(3 ),Er~(3 )的研究

研究了大孔网状树脂XAD 4 ,XAD 7,XAD 1 1 80对二 -( 2 ,4 ,4 三甲基戊基 )膦酸 (Cyanex 571 )浸渍树脂的吸附及制备方法 ,并对Cyanex571浸渍树脂分离稀土的性能进行了研究 ,发现在盐酸介质中Cyanex 571 /XAD 7具有最强的萃取能力 ,树脂中的萃取剂含量在 0 35～ 0 4 5g·g- 1时 ,其萃取性能最好。将上述浸渍树脂装入色层柱对稀土元素 (Tb3 ,Dy3 ,Ho3 ,Er3 )进行了分离 ,且降低负载量和流速分离效果更好。     

Crystallizability of Poly(ε-caprolactone) Blends with Poly(vinylphenol) under Different Conditions

The intermolecular interaction between poly（vinylphenol） （PVPh） and polycaprolactone （PCL） and the crystallization behavior of PCL in PCL/PVPh blends with different compositions and under different conditions were investigated by Fourier transform infrared spectra （FTIR） and differential scanning calorimetry （DSC）. It has been shown that the PCL in the blends with different blend ratios all exists in crystalline state after solution casting, even though the crystallinity decreases with increasing PVPh content. For the melt crystallized samples, PCL in its 80/20 PCL/PVPh sample can still crystallize. The crystallinity is, however, lower than that of the solution cast sample. For blends containing 50% or 20% PCL, the as-cast samples are semicrystalline and can change to compatible amorphous state after heat treatment process. FTIR analysis shows the existence of hydrogen bonding between PCL and PVPh and the fraction of hydrogen bonds increases remarkably after heat treatment process.     

Preparation And Characterization of a New Blend of Poly(2-hydroxyethyl methacrylate) And Poly(ethylene glycol)

Poly(2-hydroxyethylmethacrylate)(PHEMA)isahydroge1widelyusedinthefieldsofcontactlenses,atificialcorneasandsofttissuesubstitutes.However,theuseofPHEMAhydrogelisrestrictedduetoitsinsufficientlypermeablecharacterandlimitedwaterintake.Therefore,modificationsofthePHEMAhydrogelp1ayakeyroleinitspracticalaPplications'.Poly(ethyleneglycol)(PEG)isanonionicwatersolublematerialthathascomplexsolubilityproperties'.Meanwhile,PEGisnontoxic.Water-swellable,water-insolublehydrogelsmaybemadefromPEGbym…     

A Facile One-pot Synthesis of 2,5-Disubstituted Oxazoles Using Poly[styrene（iodosodiacetate）]

2,5-Disubstituted oxazoles were prepared conveniently by treatment of aromatic α-methyl ketones and nitriles with poly[styrene(iodosodiacetate)] in a one-pot manner.     

Preparation of Poly(ε-caprolactone)/Poly(ester amide) Electrospun Membranes for Vascular Repair

With adjustable amphiphilicity and anionic/cationic charge, biodegradability and biocompatibility, amino acid-based poly(ester amide)s(PEAs) have drawn attention in the research of tissue engineered vascular grafts. In this work, L-phenylalanine-based PEAs with or without L-lysine were synthesized through polycondensation, and ultrafine fibrous grafts consisted of PEAs and poly(ε-caprolactone)(PCL) in given mass ratios were further prepared via blend electrospinning. Surface characterizations by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed the chemical structure, and the wettability indicated that the prepared PCL/PEAs electrospun membranes exhibited less hydrophobic than PCL. Tensile results showed that the PCL/PEAs membranes possessed suitable mechanical properties, which could meet the requirements of artificial blood vessels. Cell culture and hemolytic tests exhibited that the PCL/PEAs electrospun membranes are biocompatible. In general, the electrospun grafts of PCL/PEAs could be applied for vascular repair.     

The Synthesis of Soluble Copolymer of Poly(p-Phenylene Vinylene)

Poly(p-phenylenevinylene)rePV)anditsderivahveshavearousedgreatinterest,'sinceBurroughes:discoveredthatPPVshowedexcellentelectrolulninescent(EL)propenies.However,PPVanditsderivativessynfllesizedbyconventionalpolylnerizationreachons3areusuallyinsolubleandidesible,whichshowsinferiormechanicalpropelles.AlthoughtheprecursorpolymerroutecancircmnventfileinsolubilityofPPV,thestrategyneedsamuhStCpreachonandlhghtemperaturewlticllaffordslowyieldandoillerdisadvantages.'So,theSynthesisofsolublePPVd…     

Determination of Poly(3‐Hydroxybutyrate) using a Combination of Enzymatic Spectrophotometry and Alkaline Hydrolysis

Abstract

A combination of enzyme‐based spectrophotometric analysis and alkaline hydrolysis was developed for the measurement of poly(3‐hydroxybutyrate) (PHB). The principle of the determination is as follows: alkaline hydrolysis decomposes PHB into its monomer product 3‐hydroxybutyrate, which is followed with enzymatic reaction catalyzed by 3‐hydroxybutyrate dehydrogenase in the presence of nicotinamide adenosine dinucleotide (NAD). The product, nicotinamide adenosine dinucleotide with hydrogen (NADH) results in a spectrophotometric signal at 340 nm. This method shows high performance characteristics with simple operations.