Gel permeation chromatographic analysis of polyurethane prepolymer synthesis kinetics. I. The effect of catalyst

Polyurethane prepolymers are a complex mixture of oligomers. The proportion of the various species in this mixture determines the handling properties of the prepolymer as well as the physical properties of the final polyurethane. An analytical method has been developed that gives a clear and sensitive picture of both the reaction kinetics and the concentrations of the oligomeric species in the prepolymer mixture. The analytical method is applied to the polypropylene glycol/tolylene diisocyanate/catalyst system. The expected changes in reaction rates and in the formation of higher oligomers in the prepolymer were observed when catalyst was added at three different polyol molecular weights. An alternative equation for predicting the number average degree of polymerization is developed for the cases where reactant ratios are significantly less than one. An empirical equation is derived that permits expressing the reaction kinetic data in a linear plot. This equation is used to express the results of this work.     

Gel permeation chromatographic characterization of sodium hyaluronate and its fractions prepared by ultrasonic degradation

Summary High-molecular-weight sodium hyaluronate isolated from rooster combs was degraded by ultrasonication. The molecular weight of hyaluronate and its polydispersity was determined by gel-permeation chromatography. During 75-min treatment the molecular weight value decreased from 1.39×10⁶ Da to 2.25×10⁵ Da while the polydispersity of the molecular weight increased from 1.29 to 2.36. The reciprocal value of the square of the hyaluronate's molecular weight was linearly proportional to the time of ultrasonication.     

凝胶渗透色谱净化-高效液相色谱法测定油脂食品中的邻苯二甲酸酯类增塑剂

建立了油脂食品(方便面、油炸糕点、沙琪玛、食用油等)中5种主要邻苯二甲酸酯类增塑剂的凝胶渗透色谱（GPC）净化-高效液相色谱(HPLC)分析方法。食品样品用石油醚超声提取,经GPC净化后,采用反相HPLC进行分析。所用的分离柱为Labtech C18(250 mm×4.6 mm, 5 μm),以乙腈和水为流动相,梯度洗脱。方法的相关系数皆在0.997以上,目标物的检出限(信噪比为3计)为3.25～13.4 μg/L。在50 mg/L添加水平时,目标物的加标回收率为70.4%～113.6%,相对标准偏差为0.3%～5.8%(n=3)。该方法简便、快捷、实用,可用于油脂食品中邻苯二甲酸酯类增塑剂的分析测定。     

Gel permeation chromatographic studies of the degradation of polyethylene with fuming nitric acid. II. Bulk polyethylene

Preliminary results are reported on the use of gel permeation chromatography in morphological studies of bulk polymers and fibres. Several samples of bulk isotropic and drawn polyethylene were analyzed by gel permeation chromatography following nitric acid oxidation. In all cases suitable samples showed two peaks in the molecular weight distribution, suggesting a qualitative similarity with results for single crystals. It is concluded that the present data are consistent with chain folding in bulk polymers, both in the isotropic and oriented states, with a less degree of regularity than exists in single crystals.     

凝胶渗透色谱净化-高效液相色谱法测定鱼肉中的5种激素类药物残留

建立了凝胶渗透色谱净化-高效液相色谱法测定鱼肉中己烯雌酚、雌二醇、炔雌醇、炔诺酮、炔诺孕酮5种激素类药物残留的方法。样品用乙酸乙酯-甲醇(8:2, v/v)溶液提取,提取液经Pharmadex LH-20凝胶柱(450 mm×15 mm)净化,并用甲醇-乙酸乙酯-乙酸(800:200:2, v/v/v)溶液洗脱。采用Agilent TC-C18柱(250 mm×4.6 mm, 5 μm)分离净化后的样品,用乙腈-水(45:55, v/v)溶液洗脱,流速为1.2 mL/min,双检测波长为245 nm和222 nm。5种激素类药物在0.05～2.5 mg/L范围内有良好的线性关系(r ＞0.999),检出限为10～24 μg/kg,平均加标回收率为60.1%～89.0%,相对标准偏差为2.0%～7.4%。该方法快速、简单,可应用于鱼肉中激素类药物残留量的检测。     

Interpenetrating polymer networks of polyurethane and graft vinyl ester resin–polyurethane formed with diphenylmethane diisocyanate

For enhancing the compatibility and/or the interpenetration of the simultaneous interpenetrating networks (SINs) composed of polyurethane (PU) formed with uretonimine modified 4,4′‐diphenylmethane diisocyanate and vinyl ester resin (VER), a series of graft VERs consisting of different lengths of side chains were synthesized and characterized. It was found that there exists some limited short‐range order due to the strong hydrogen bonding in the graft VER network composed of butanol side chains (BO‐g‐VER). The graft VER network composed of poly(oxypropylene) (PPO) side chains (M_n: 200, 200‐g‐VER) showed compatible system, while the VER network consisting of longer PPO grafts (M_n: 390, 390‐g‐VER) exhibited microphase separated morphology. Based upon the DSC and FTIR measurements as well as the SEM and TEM observation, the lengths of side chains existing in graft VER network have great effect on the morphologies of PU/graft VER SINs. For PU/BO‐g‐VER SINs, there has been some interpenetration between the two networks because of the miscibility between the BO‐g‐VER network and the hard segments existing in the PU network. For PU/200‐g‐VER SINs, the good compatibility and/or the interpenetration between the two phases was observed, since the long‐range ordered structure of hard segments in PU phase was greatly suppressed, resulting from the excellent miscibility between the urethane groups as well as the PPO side chains existing in the 200‐g‐VER network and those in the PU network, respectively. Thus, the strong reinforcement effect of these two graft networks on the PU network and the excellent mechanical properties of the SIN systems were observed. However, the PU/390‐g‐VER SINs showed the complicated morphologies because of existing microphase‐ separated morphology of 390‐g‐VER network in itself. In this case, the enhancement effect of such a graft VER network on the PU network is limited. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 136–144, 2000     

Gel permeation chromatographic study of the molecular weight distribution of tannins in the wood,bark and leaves ofEucalyptus spp.

Summary The molecular weight distribution of tannins from the wood, bark and leaves ofEucalyptus camaldulensis, E. globulus andE. rudis from two different Spanish provenances has been studied by high performance gel permeation chromatography, using the compounds' acetylated derivatives. The MW distribution profiles showed important variability depending on the type of vegetal tissue, the species and, in some cases, on the geographical provenance of the samples. Bark was the vegetal tissue that yielded tannins with the highest molecular weight, followed by wood and leaves. Tannins from wood and bark ofE. camaldulensis were of higher molecular size than those fromE. globulus andE. rudis; those in the leaves ofE. globulus andE. camaldulensis were similar in molecular size and larger than those in the leaves ofE. rudis.     

加速溶剂萃取-凝胶渗透色谱净化-气相色谱快速分析动物源性食品中残留的多种有机磷农药

建立了动物源性食品猪肉、牛肉、鸡肉及鱼肉中36种有机磷农药残留的快速分析方法。以乙腈作为溶剂,对试样采用加速溶剂萃取仪萃取,自动凝胶渗透色谱仪净化预处理,N-丙基乙二胺(PSA)填料再净化,毛细管气相色谱法分离,火焰光度检测器(磷型)检测,内标法定量。该方法分离效果良好,重现性好,灵敏度、精密度高,杂质干扰少。36种有机磷农药的检测限(LOD)为0.0012 mg/kg(乙拌磷)～0.014 mg/kg(吡唑硫磷),定量限(LOQ)为0.004 mg/kg(乙拌磷)～0.047 mg/kg(吡唑硫磷)。当试样中有机磷农药的添加浓度分别为0.05,0.1,0.2 mg/kg时,回收率为58.2%～106.3%。方法的最低检测限和添加回收率均符合农药残留分析的要求。     

Gel permeation chromatography and cellulose. II. Application of universal calibration

In previously reported work concerning the chain-length distributions obtained by gel permeation chromatography (GPC) in celluloses, degrees of polymerization (DP) of unusually high magnitude were reported. Later work in GPC has shown that the concept of relating extended nolecular chain length of different polymers to elution volume for obtaining molecular weight is not theoretically sound. Correlation of molecular hydrodynamic volume (indicated by the product of intrinsic viscosity and molecular weight) with elution volume has been found to place polymers of vastly different natures on a single curve, such is now designated universal calibration. Application of universal calibration to the determination of DP distributions in celluloses required a different method of converting counts to DP. This new procedure is described in detail. Weight-average DP's given by the procedure for samples of cellulose I, II, III, and IV were 5190, 4520, 4795, and 3390, respectively. These are decreases of 74–75% from the results obtained by the extended-chain procedure. The results compare favorably with the viscosity-DP's of the samples. Number-average DP's were 1580, 1040, 1140, and 490 for the four samples, respectively, these being decreases of 87–93% from the values formerly reported. The polymolecularity ratios for the samples are now unusually large, being 3.4, 4.7, 4.2, and 7.1, respectively.     

Gel filtration and high-performance liquid chromatographic analysis of phosphotungstic acid soluble peptides from blue cheeses

Summary The nitrogen fraction from cheese, soluble in phosphotungstic acid has been analyzed by gel permeation and high performance liquid chromatography. Elution profiles of this fraction on Sephadex G-10 show that there are no peptides of molecular weight higher than 700 daltons. Six fractions have been obtained. The first one has the peptides and some amino acids. Fractions II to VI contains mostly free amino acids. Fraction I has been separated into many peaks by HPLC. Six or seven of these peaks are presumed to correspond to peptides. A part of this work has been presented in XXI Reunión Bienal de la Socieded Espa?ola de Química. Sept. 1986. Santiago de Compostela. Espa?a.     

凝胶渗透色谱净化气相色谱-质谱法检测河豚鱼、鳗鱼和对虾中191种农药残留

建立了河豚鱼、鳗鱼和对虾中191种农药多残留的气相色谱-质谱分析方法。样品用乙酸乙酯-环己烷(体积比为1:1)均质提取,凝胶渗透色谱净化,收集26～44 min的流出液并进行在线浓缩,通过气相色谱柱(DB-1701)分离后在选择离子监测(SIM)模式下进行质谱检测。分别以最低定量限和4倍最低定量限为添加浓度对河豚鱼、鳗鱼和对虾样品进行了两个水平的添加回收率实验,方法的回收率范围为50.2%～120%,其中89.5%的农药的回收率为70%～120%,相对标准偏差范围为0.6%～21.6%。方法的最小检出限和最低定量限范围分别为0.002～0.3 mg/kg和0.007～1.2 mg/kg。该方法的灵敏度、准确度和精密度均符合农药多残留检测的技术要求,适用于河豚鱼、鳗鱼和对虾等动物源性水产品中多种农药残留的检测。     

Effect of the diisocyanate on the structure and properties of polyurethane acrylate prepolymers

In this study, we investigated the role of diisocyanate on the properties of polyurethane acrylate (PUA) prepolymers based on polypropylene oxide (M̄_n = 2000 g · mol⁻¹). The diisocyanates studied were isophorone diisocyanate, 4‐4′dicyclohexylmethane diisocyanate, and toluene diisocyanate (pure 2,4‐TDI, pure 2,6‐TDI, and a TDI mixture, TDI_tech). The molecular structure of the diisocyanate had a major role on the course of the polycondensation and, more precisely, on the sequence length distribution of the final prepolymer. Moreover, the structural organization of the prepolymer also strongly depended on the nature of the diisocyanate. Two types of behaviors were particularly emphasized. On the one hand, the PUA synthesized from 2,4‐TDI displayed an enhanced intermixing between soft polyether segments and hard urethane groups, as revealed by the analysis of hydrogen bonding in Fourier transform infrared. Consecutively, the glass transition shifted to higher temperatures for these polymers. On the other hand, strong hard–hard inter‐urethane associations were observed in 2,6‐TDI‐based prepolymers; these led to microphase segregation between polyether chains and urethane groups, as revealed by optical microscopy. This inhomogeneous structure was thought to be responsible for the unusual rheological behavior of these PUA prepolymers. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2750–2768, 2000     

Total chromatographic optimization (TOCO) II. Precision and efficiency of analysis

Summary A chromatographic system set at an operating condition takes its own precision and efficiency which are numerically described by the information called FUMI and the information flow , respectively. Optimization for a variable such as mobile phase composition draws a line in the - space. This paper demonstrates that optimization of different variables displays different patterns of lines in the - space. The variables examined here are mobile phase composition, column length, flow rate (velocity) and detection wavelength (or the amount of internal standard). Clear difference in the analytical roles of the variables can be known from the - plots.     

Enhancing toughness of poly (lactic acid)/Thermoplastic polyurethane blends via increasing interface compatibility by polyurethane elastomer prepolymer and its toughening mechanism

Due to the environmental pollution caused by the petroleum-based polymer, poly (lactic acid) (PLA), a biodegradable and biocompatible polymer that obtained from natural and renewable sources, has attracted widespread attention. However, the brittleness of PLA greatly limits its application. In this study, the super toughened PLA-based blends were obtained by compatibilizing the PLA/thermoplastic polyurethane (TPU) blends with the polyurethane elastomer prepolymer (PUEP) as an active compatibilizer. The mechanical properties, thermal properties and corresponding toughening mechanism of PLA/TPU/PUEP system were studied by tensile test, instrumented impact test, dynamic mechanical analysis (DMA), scanning electronic microscope (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). All the results demonstrate that the isocyanate (−NCO) group in PUEP is successfully reacted with the –OH groups at both sides of the PLA and the obtained polyurethane (PU)~PLA copolymer (PU ~ cõ PLA) significantly improves the interfacial compatibility of PLA/TPU blends. The gradually refined dispersed phase size and fuzzy phase interface as displayed in SEM images suggest a good interfacial compatibilization in the PLA/TPU/PUEP blends, probably due to the isocyanate reaction between PLA and PUEP. And the interfacial reaction and compatibilization among the components led to the formation of super toughened PLA/TPU/PUEP blends. And the instrumented impact results indicate that most of the impact toughness is provided by the crack propagation rather than the crack initiation during the entire fracture process.     

线形多嵌段聚氨酯的合成与结构研究

本文用溶液二步法合成了分别以聚酸、聚酯为软段的线形多嵌段聚氨酯，经抽提证明该弹性体内没有产生交联．用核磁共振（NMR）、红外光谱（FTIR）、差示扫描量热法（DSC）等手段对其进行表征，计算得到弹性体中硬段的百分含量，并就弹性体的热塑弹性作了深入的探讨。     

Studies on thermotropic liquid crystalline polyurethanes. II. Synthesis and properties of liquid crystalline polyurethane elastomers

Three series of novel thermotropic liquid crystalline polyurethane elastomers (TLCPUEs) were studied. Hard segments were formed by using hexamethylene diisocyanate (HDI) reacted with a mesogenic unit, benzene-1,4-di(4-iminophenoxy-n-hexanol), which also acted as a chain extender. Three diols: 1,10-decanediol,poly(oxytetramethylene) glycol (PTMEG) M _n = 1000 and PTMEG M _n = 2000 were used as the soft segments. The effects of soft segments of polyurethanes on the liquid crystalline behavior were studied. Higher molecular weight TLCPUEs were obtained by adding 30?50 mol % of mesogenic segments to diisocyanates. In contrast to a conventional chain extender such as 1,2-ethylene glycol or 1,4-butyl glycol, the synthesized polyurethane elastomers exhibited a mesophase transition by using a mesogenic unit as the chain extender. Mesophase was found for all synthesized LC polyurethanes except of polymers H2-A-12 and H2-A-7. The structures and the thermal properties of all synthesized TLCPUEs were studied by using FTIR spectroscopy, wide-angle x-ray diffraction (WAXD) and DSC measurements, a polarizing microscope equipped with a heating stage, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). Mechanical properties were also examined by using a tensilemeter. © 1995 John Wiley & Sons, Inc.     

凝胶渗透色谱净化-超高效液相色谱-串联质谱法测定皮革制品中7种尼泊金酯类防腐剂

利用超高效液相色谱-串联质谱(UPLC-MS/MS)结合凝胶渗透色谱(GPC)技术,建立了一种快速分离和测定皮革制品中7种尼泊金酯类防腐剂的分析方法。样品经超声提取、浓缩、GPC净化,甲醇-水溶液(1:1, v/v)溶解,采用Acquity UPLCBEH C18柱(50 mm×2.1 mm, 1.7 μm)分离,以甲醇和水为流动相,梯度洗脱,电喷雾负离子模式电离,采用多反应监测模式检测和外标法定量。该方法在0.1～1.0 mg/L范围内线性关系良好(r＞0.99);在添加量为0.5～3.0 mg/kg时,平均回收率为(79.44±5.67)%～(98.07±9.50)%,相对标准偏差(RSD)为4.24%～14.00%;方法的检出限(LOD)为4～12 μg/kg,定量限(LOQ)为13.2～39.6 μg/kg。该方法操作简便、快捷、灵敏、准确,适合皮革中多种尼泊金酯类防腐剂的确证和定量测定。     

Gel permeation chromatographic determination of activation rate constants in nitroxide-controlled free radical polymerization, 1. Direct analysis by peak resolution

The dissociation rate constant k_d related to the homolytic cleavage of the C ON bond formed between a polystyrene (PS) and 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) is determined by adopting the gel permeation chromatography peak-resolution method to the styrene polymerization with a PS-TEMPO adduct as a probe and the radical initiator tert-butyl hydroperoxide. The result was given by the Arrhenius equation, k_d = A exp(−E/(RT)) with A = 3.0 × 10¹³ s⁻¹ and E = 124 kJ · mol⁻¹.     

聚酯的序列结构对聚氨酯弹性体形貌的影响

以己二酸(AA),1,4-丁二醇(BDO),乙二醇(EG)分别采用一步法、二步法合成分子量为3000的聚酯PAEB-R和聚酯PAEB-A.再分别与二苯基甲烷二异氰酸酯(MDI)、扩链剂1,4-丁二醇(BDO),乙二醇(EG)反应分别合成固含量30%与粘度为20000的聚氨酯(PAEB-R)-MDI-TPU和聚氨酯(PAEB-A)-MDI-TPU.SEM、AFM表明不同工艺所合成的聚氨酯均存在微相分离,且聚氨酯(PAEB-R)-MDI-TPU微相分离程度高于(PAEB-A)-MDI-TPU.