CHARACTERIZATION OF COMPOSITIONAL HETEROGENEITY OF SEGMENTED COPOLYMERS BY GPC TECHNIQUE

The GPC technique wth two detectors has been used to study the heterogeneity in compositionthard segment content) of a series of polyethylene terephthalate/polycaprolactone segmented copoly-mers. Improvement in data treatment has been made to avoid the difficulty resulted from the lake oflow molecular weight hard segment homopolymers. Results show that for each sample the moleculesof larger coil size in CHCI_3 usually have higher hard segment content. A parameter, the averagedeviation of hard segment content, has been proposed to characterize the heterogeneity in compositionof the samples. It is found that the heterogeneity of the samples increases with increasing theiraverage hard segment content.     

Deformation behavior and mechanical properties of hard elastic and porous films of polyethylene

Hard elastic samples of linear polyethylene were prepared by melt extrusion at a high velocity of the melt flow and by subsequent annealing of crystallized samples. The deformation behavior of hard elastic samples obtained by annealing of as-spun samples at different temperatures has been analyzed at uniaxial extension resulting in formation of porous structure. Mechanical properties of microporous films in the longitudinal and transverse directions have been investigated. Composite systems consisting of a microporous polyethylene film and a thin layer of an electroconducting polymer have been prepared. Mechanical properties of composite systems, such as elastic modulus, tensile strength, and break elongation, have been compared with the properties of polyethylene substrates.     

长软链段对苯二甲酸乙二酯-环氧乙烷多嵌段共聚物的组成不均一性研究

合成了不同软链段长度和不同硬链段含量的系列对苯二甲酸乙二酯－环氧乙烷(PET-PEO)多嵌段共聚物,用NMR质子港测定了硬链段含量,对部分溶于氯仿的PET－PEO多嵌段共聚物进行了分离,并分别测定其氯仿可溶物和不溶物的硬链段含量、熔融热谱和热结晶谱.揭示了PET－PEO多嵌段共聚物的组成不均一性及其对软镇段长度和硬链段含量的依赖性,进而用DSC热谱证明了软链段和硬链段的结晶能力与PET－PEO多嵌段共聚物组成不均一性密切相关.     

Synthesis and microstructure-mechanical property relationships of segmented polyurethanes based on a PCL-PTHF-PCL block copolymer as soft segment

The goal of this work has been the synthesis of novel materials based on a biodegradable polycaprolactone-block-polytetrahydrofurane-block-polycaprolactone diol (PCL-b-PTHF-b-PCL). The segmented thermoplastic polyurethanes (STPU) have been synthesised in bulk without catalyst at different molar ratios and their characterization has been performed by different techniques. The physic-chemical interactions, responsible for the unique polyurethane properties, have been evaluated by total attenuated Fourier transform infrared spectroscopy (ATR-IR) in the amide I region using a Gaussian deconvolution technique and, on the other hand, atomic force microscopy (AFM) has been employed to determine the phase microstructures. The effect of increase the hard segment content (HS) has been discussed from the viewpoint of the miscibility of hard and soft segments, analyzed by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The influence of HS content on the microstructure-mechanical property relationships has also been investigated. Special attention has been focused on the wettability of the samples, measured through water contact angle measurements (WCA), to determine the tendency for biocompatibility of the samples.     

Structural investigation of lac resin—II

The three fractions of lac rein viz., hard resin I, hard resin II and soft resin have been cleaved with hydriodic acid followed by deiodination. The products were separated into fatty acids and terpene acids. The former have been studied by GLC and data on the nature and distribution of the chain lengths and their relative amounts were thus obtained. Cleavage of the different fractions of the resin with hydrogen chloride followed by alkaline hydrolysis gave the total aleuritic acid quantitatively. Based on the above results, the possibility of the presence of alkali stable linkages in lac resin and the amount of aleuritic acid liberated only by acid cleavage have been determined.     

色氨酸及其主要代谢产物的分离和在生物样品中的测定

建立以乙酸缓冲系统和甲醇作流动相、电化学和紫外检测器联用的高效液相色谱法,分离和测定了色氨酸经5-羟色胺和犬尿酸原两条主要代谢途径的8种代谢物。使用三氯乙酸作离子对试剂以延长3-羟犬尿酸原的保留时间,分析了流动相pH值和三氯乙酸浓度对各物质分离的影响及检测条件。结果表明,pH值及三氯乙酸浓度对各物质保留时间有明显影响,可作为控制分离的主要因素。此外,对生物样品中各物质分离和检测条件进行了讨论。     

近红外光谱快速分析青贮饲料pH值和发酵产物

采用近红外光谱技术,结合偏最小二乘回归法,研究了142个不同种类的秸秆青贮饲料样品的pH值和发酵产物(乳酸、乙酸、丙酸、丁酸和氨态氮),建立了干燥粉碎和新鲜样品的近红外漫反射光谱定量分析模型以及浸提液样品的近红外透射光谱定量分析模型。研究发现,pH值的近红外漫反射光谱和透射光谱的分析效果均较好,校正模型决定系数R2和验证集样品预测值与化学值的相关关系决定系数r2都大于0.80,并且干燥粉碎、新鲜和浸提液样品的RPD值分别为3.44、2.50和2.27;3种状态样品的乳酸、乙酸、丁酸和氨态氮的定量分析模型精度需进一步提高;R2在0.64~0.85之间;RPD值在1.38~1.93之间;丙酸含量的测定结果较差。方差分析显示,3种状态样品的测定结果之间均无显著性差异(P>0.05)。     

聚酯-聚醚多嵌段共聚物形态的电镜研究

利用透射电镜技术对低硬链段含量聚酯-聚醚多嵌段共聚物中硬段结晶的形态进行了研究。结合前一工作中SALS和偏光显微镜等的研究结果对影响结晶形态的因素进行了讨论。认为在这些共聚物体系中,结晶区域的大小取决于分相形成硬段密集微区的速率与总的结晶速率之比,而在这些区域中的形态结构则取决于晶体生长速率和成核速率之此。实验表明,以PET为硬段的试样相当于两比值均较大的情况,而以PBT为硬段的试样则相反。     

Correlations between gas permeation and free-volume hole properties of polyurethane membranes

A series of polyurethane films based on hard segments consisting of toluene diisocyanate and 1,4-butanediol and different soft segments consisting of hydroxyl terminated polybutadiene, hydroxyl terminated polybutadiene/styrene and hydroxyl terminated polybutadiene/acrylonitrile were synthesized by solution polymerization separately. Positron annihilation lifetimes were measured at room temperature for all samples studied. We found that both the free volume size and fractional free-volume decreased with the increase of hard segment content. On the other hand, direct relationship between the gas permeability and the free-volume has been established based on the free-volume parameters and gas diffusivity measured. Experimental results revealed that the free-volume plays an important role in determining the gas permeability.     

水性聚氨酯硬段含量对其氢键相互作用及性能的影响

异佛尔酮二异氰酸酯（IPDI）、二羟甲基丙酸(DMPA)作为硬段,合成了水性聚氨酯。 研究了硬段含量（质量分数）对乳液稳定性、膜耐热和力学性能等的影响。 当硬段质量分数低于26%时,乳液贮存稳定性较差。 随着硬段含量增加,聚氨酯膜拉伸强度迅速增加,断裂伸长率略有降低;红外光谱显示,自由的N-H伸缩振动峰强度减弱,氢键化N-H的振动峰强度增加;同时C=O伸缩振动峰整体向低波数方向移动,C=O伸缩振动峰峰形有明显的变化;DSC测试在50～125 ℃出现明显的氢键解离现象,吸热峰增强,证实了氢键作用力随着硬段含量的增加逐渐增强。 TG测试表明,水性聚氨酯硬段和软段分步解离,随着硬段含量的增加,硬段分解温度降低,水性聚氨酯耐热性能下降。     

Direct measurement of homovanillic, vanillylmandelic and 5-hydroxyindoleacetic acids in urine by capillary electrophoresis

Separation conditions in CE, with a neutral coated capillary and reversed polarity, have been optimised to make direct measurement of vanillylmandelic acid, homovanillic acid and 5-hydroxyindoleacetic acid possible in urine samples without pre-treatment. The method developed has been validated, presenting adequate parameters for linearity, accuracy and precision. Detection limits range from 0.03 to 2.5 microM. Finally the method has been applied to urine samples taken from patients, both adults and children, in hospital. Some of them were also measured by immunoassay and HPLC-electrochemical detection and results have been compared.     

Investigations of a series of PPDI-based polyurethane block copolymers. I. General morphology

The morphology of a series of segmented polyurethane block copolymers is characterized by x-ray scattering, differential scanning calorimetry (DSC), density measurements, and tensile studies. The materials contain hard segments formed from paraphenylene diisocyanate (PPDI) and flexible segments formed from poly(oxytetramethylene) (POTM) ranging in molecular weight from 650 to 2000. Four different molecular weight compositions were investigated, with the weight fraction of the hard segment (w_h) ranging from 0.14 to 0.33. The microphase structure has been examined using small-angle x-ray scattering, and the microphase transition zone thickness is estimated to be on the order of 1 nm. Oriented samples have been characterized with wide-angle x-ray scattering, and the flexible segment is shown to undergo stress-induced crystallization. DSC thermograms show flexible segment melting in the compositions containing the highest two molecular weights of the flexible segments. The hard segment thermal transitions were complex with a broad melting peak that varied with weight fraction and with a high temperature transition attributed to regions with hard segment lengths longer than the bulk of the hard segment component. There is an increase in tensile strength and initial modulus and decrease in elongation with increasing w_h. Density data suggest the existence of a multiphase system.     

双模板法制备具有介孔孔壁的三维有序大孔二氧化铈及其改善的低温还原性能

以聚甲基丙烯酸甲酯(PMMA)为硬模板,三嵌段共聚物F127、十六烷基三甲基溴化铵(CTAB)或聚乙二醇(PEG)为软模板剂(表面活性剂),柠檬酸为络合剂,硝酸铈为金属前驱体,采用双模板法成功地合成出具有介孔孔壁的三维有序大孔(3DOM)结构的立方相CeO2样品CeO2-F127,CeO2-CTAB和CeO2-PEG,...     

镶嵌型乳胶粒子的合成

以苯乙烯、甲基丙烯酸甲酯、丙烯腈等单体或它们的混合物为硬单体,天然胶乳为弹性组分,经多步种子乳液聚合法制得了在天然胶乳的粒子上镶嵌硬聚合物相的互穿网络型乳胶粒子.考察了十二烷基硫酸钠、十二烷基苯磺酸钠、壬基酚聚氧乙烯醚、油酸等乳化体系,过硫酸钾、过氧化苯甲酰热引发体系及异丙苯过氧化氢-四乙烯五胺、叔丁基过氧化氢-四乙烯五胺等氧化还原引发体系对聚合反应的影响.研究了交联剂用量对互穿结合率、溶胶含量的影响及溶胀时间、硬单体组成、乳化剂种类对乳胶粒子形态的影响,确定了适宜的聚合配方和工艺条件.透射电镜观察乳粒形态结果表明,单一使用极性或非极性单体,仅得到核-壳结构乳液,而采用不同极性单体复合、溶胀、互穿,得到的是镶嵌硬聚合物型乳粒结构.     

Iodometric determination of ascorbic acid by controlled potential coulometry

An iodometric method for the determination of ascorbic acid has been devised. The method is based on previously developed coulometric instrumentation. The stability of different ascorbic acid solutions has been studied and the best conditions have been established. Ascorbic acid has been determined in different kinds of samples but with the main interest on pharmaceutical preparations. Speqial regard has also been paid to the other constituents in such samples, with respect to possible interferences. The error of the coulometric method is about 0·1% and the time of an analysis is in the range 2–6 min.     

Preparation of Titania Monolith Column and Application in Determination of Benzoic Acid by HILIC

The titania monolith column has been synthesized through a template-free sol–gel route, and a simple and reliable method for the determination of benzoic acid by hydrophilic interaction liquid chromatography using the prepared titania monolith has been developed. The influences of acetonitrile, acetate buffer and buffer pH on the retention of benzoic acid were investigated. Benzoic acid in carbonated drinks and fruit beverages samples were determined within 5?min and quantitative analysis was carried out by external standard method with a correlation coefficient (R ²) of 0.9984. The relative standard deviation was 0.91?% and the recovery ranged from 92.5 to 101.3?%. The proposed method is suitable for the analysis of benzoic acid in beverage samples.     

Photometrische Bestimmung von Fluoriden im Trinkwasser mit Lanthan-Alizarin-Komplexan nach Abtrennung von Störionen mittels Kationenaustausch

The simple method described employs the direct detection as “alizarinfluorine-blue complex”. The interfering influence of high contents of sulphate and chloride can be eliminated by correction. Good reproducibility has been obtained when applying the method to very hard water samples, also in comparison with the values obtained by distillation.     

Determination of Nitrilotriacetic Acid in Waters and Waste Waters by Gas-Liquid Chromatography,Differential Pulse Polarography and a Colorimetric Method

Abstract

A comparison of gas-liquid chromatography, differential-pulse polarography and a colorimetric method for the determination of nitrilotriacetic acid in settled sewage, sewage effluent, potable water, soil extracted water and deionised water has been undertaken. Differential-pulse polarography has also been applied to the determination of nitrilotriacetic acid in saline samples. By statistical analysis of replicate determinations, accuracy and precision have been evaluated, and calibration linearity assessed. Interferences were observed for sewage samples when analysed by all three methods. Precision was generally higher for differential-pulse polarography down to 100 μgl^?1, although only gas-liquid chromatography is applicable to concentrations below 25μgl^?1 in non-saline samples. The colorimetric method was not applicable to concentrations below 500 μgl^?1 of nitrilotriacetic acid.     

Microdiffusion and spectrophotometric determination of fluoride in biological samples

Routine separation of fluoride from large numbers of biological samples (soft and hard tissues) is achieved by microdiffusion from perchloric acid and absorption by sodium hydroxide on filter paper in disposable polypropylene vials. Spectrophotometry with a modified lanthanum/alizarin complexone reagent allows rapid determination of fluoride. Up to 80 samples can be processed per day. Recoveries are in the range 88–102%. Results obtained by spectrophotometry and with the fluoride-sensitive electrode agree within 3–10% for various samples of krill and shrimp products.     

Preparation of Titania Monolith Column and Application in Determination of Benzoic Acid by HILIC

The titania monolith column has been synthesized through a template-free sol–gel route, and a simple and reliable method for the determination of benzoic acid by hydrophilic interaction liquid chromatography using the prepared titania monolith has been developed. The influences of acetonitrile, acetate buffer and buffer pH on the retention of benzoic acid were investigated. Benzoic acid in carbonated drinks and fruit beverages samples were determined within 5 min and quantitative analysis was carried out by external standard method with a correlation coefficient (R ²) of 0.9984. The relative standard deviation was 0.91 % and the recovery ranged from 92.5 to 101.3 %. The proposed method is suitable for the analysis of benzoic acid in beverage samples.