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51.
Aquatic humic-type solutes were separated in parallel from the same fresh water source by four different procedures: non-ionic polymethyl methacrylate (DAX-8) and functional cross-linked polyvinylpyrrolidone (PVP) resins, functional diethylaminoethyl cellulose (DEAE) and tangential ultrafiltration completed with a weakly basic anion exchange resin (IRA-67). The similarity-dissimilarity between the quantities and qualities of the different humic samples is discussed, especially in the light of the original dissolved organic matter (DOM). During the past two decades, a significant progress has occurred in the aquatic humic research due to the so-called hydrophobic-hydrophilic properties possessed by certain non-ionic sorbing solids. As a result of many coincidences, it may be justifiable to examine critically the prevailing isolation techniques of aquatic humic solutes and to try to update their complicated definitions. For that reason, it is reasonable to summarize the leading principles of different isolation techniques in Section 1 of this article. The results of the present study strongly support the applicability of the PVP resin, alone or completed in sequence with a suitable non-ionic sorbing solid, for isolation of aquatic humic-type solutes from both quantitative and qualitative points of view. In certain cases, the DEAE cellulose gives a useful alternative for conventional sorbing solids in the isolation of the bulk of aquatic humic solutes. The base-catalyzed ester hydrolysis of the HM during the chromatographic isolation of the DOM seems to be relative minor. 相似文献
52.
研究了聚乙烯吡咯烷酮对桑色素和铅(Ⅱ)络合反应的增敏作用,发现PH3.43时Pb-morin-PVP三元体系在435nm激发下,444nm处有强荧光发射,提出了荧光光度法测定痕量Pb的新方法,其线性范围为0-240μg/L,对空白11次测定RSD为3.5%,检出限为2.1*10^-2mg/L。 相似文献
53.
《Journal of Polymer Science.Polymer Physics》2018,56(3):248-254
This paper outlines the shrinkage of electrospun polyvinylpyrrolidone (PVP) fiber mats during thermal treatment. The thermal behavior and phase changes within the fibers were investigated by DSC and TGA/DTA. Five precursors with different PVP loading in ethanol were electrospun. The mats shrinkage as function of temperature was measured in the RT–200 °C range. Shrinkage rate drastically increased above the polymer glass transition point, Tg (150–180 °C), due to increase in polymer chain mobility. Mats shrinkage at 200 °C as function of PVP concentration showed a minimum at ∼10%wt. Below 10% PVP the mats morphology is non‐uniform, consisting of beads and fibers. Above 10% PVP, only flat and uniform fibers were observed. This paper outlines the dominant mechanism governing the mats shrinkage during heating. In addition, the effect of PVP concentration on the expansion of fibers diameter was investigated and found to be consistent with the linear shrinkage observing a minimum at ∼10% PVP. The effect of applied voltage on mat shrinkage was investigated, and showed a minimum at 12 kV. Understanding the interplay between fibers morphology and thermal shrinkage allows precursor composition and system optimization needed for minimizing shrinkage negative effects on the structure and properties of electrospun fiber mats. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 248–254 相似文献
54.
Irene Bartolozzi 《European Polymer Journal》2007,43(11):4628-4638
Telechelic N-vinyl-2-pyrrolidinone (NVP) oligomers terminated by hydroxyl groups were prepared by radical polymerization in the presence of functional chain transfer agents. Then hydroxy-terminated poly(NVP) was used as initiator in the ring opening polymerization of ε-caprolactone (ε-CL). Experiments were performed either under basic conditions or by using SnOct2 or ZnEt2 as catalyst. The resulting amphiphilic AB-type block copolymers were thoroughly characterized by spectroscopic and thermal techniques. These data and fractionation in protic solvents indicated that the copolymerization products are constituted by a mixture of copolymers with a wide composition range. The water-soluble copolymer fractions formed micelles and nanoaggregates that showed an appreciable capacity of loading piroxicam, a hydrophobic non-steroidal anti-inflammatory drug. Contact angle measurements, atomic force microscopy, and surface plasmon resonance measurements indicated that the surface of films prepared from the insoluble fractions does not have antiopsonizing properties in spite of their high hydrophilicity. 相似文献
55.
56.
用表面张力 (γ)法研究了非电解质聚合物聚乙烯吡咯烷酮 (PVP)或聚乙二醇 (PEG)与烷基硫酸纳同系物中十四烷基硫酸钠 (SMS)、十二烷基硫酸钠 (SDS)及十烷基硫酸钠 (SDeS)间团簇化临界浓度的变化规律 .上述软物质团簇的γ lgc曲线均具有双拐点即拟双平台特征 ,表明在双拐点之间非电解质聚合物与烷基硫酸钠形成软物质团簇 .对应于双拐点有两个表面活性剂临界浓度值c1 和c2 ,且符合c1 PVP RSO4 Na团簇化体系lgc1 =1 5 8- 0 341n(R2 =0 9981) ,对PEG RSO4 Na团簇化体系lgc1 =1 38- 0 313n(R2 =0 9993) .实验结果还表明 ,在聚合物质量浓度 (或链节浓度 )相同的前提下 ,聚合物分子量变化对c2 值亦基本无影响 . 相似文献
57.
A series of hydrogels in the form of rods were prepared from kappa-carrageenan (KC) and poly (N-vinyl pyrrolidone) (PVP) by gamma radiation with 60Co γ source at room temperature. The properties of the prepared hydrogels, such as the gel strength, gel fraction and swelling behavior were investigated. Incorporation of KC into the PVP/water system increased obviously the gel strength and equilibrium degree of swelling (EDS) of PVP hydrogel. The experimental analyses showed that the crosslinking reaction of PVP was quicker than the degradation of KC at a low dose (less than 30 kGy), and the degradation of KC was inhibited in the PVP/KC mixture system. So an interpenetrating polymer network (IPN) hydrogel composed of PVP (a chemical crosslinking network) and KC (a physical crosslinking network) was proposed here. The existence of different classes of water in this IPN system was shown by water melting curves using DCS. 相似文献
58.
O. Z. Higa S. O. Rogero L. D. B. Machado M. B. Mathor A. B. Lugo 《Radiation Physics and Chemistry》1999,55(5-6):705-707
Hydrogels composed of PVP, PEG and agar, produced by simultaneous crosslinking and package sterilization by ionizing radiation, are used mainly as wound dressing. In this study, membranes prepared in different conditions were tested for their properties including in vitro biocompatibility. The results showed that the mechanical properties were in an acceptable range of values and that the membranes can be considered as non toxic and non hemolytic to the cells. 相似文献
59.
End-stage renal diseases are affecting many patients and as a result, demand to receive dialysis service is growing annually. Morbidity and mortality rates are reported to be higher in comparison with healthy humans. The reason is reported to be the hemoincompatiblity of blood purification membranes, which hinders patients’ lives. Activation of different immune systems in the body, in case of blood-membrane interaction, results in several side effects, of which cardiovascular shocks have been mentioned to be a major one. Efforts to solve this issue have resulted in different generations of dialysis membranes. Zwitterionic immobilized membranes are the latest (third) generation, which owns a higher degree of hemocompatiblity with more stability of immobilized structures. This critical review intends to cover recent efforts conducted over the zwitterionization of polymeric membrane surfaces with the goal of improving hemocompatibility. Different aspects of third-generation membranes are discussed for a better understanding of the current gap and gathering the knowledge to further develop the field. Accordingly, this critical survey provides an in-depth understanding of blood purification membranes zwitterionization for paving the way for the optimum enhancement of hemodialysis membrane hemocompatibility. 相似文献
60.
水溶性非离子大分子与烷基硫酸钠同系物团簇化的比饱和簇集量 总被引:4,自引:0,他引:4
研究了烷基硫酸钠同系物(ROSO3Na)与聚乙二醇(PEG)及聚乙烯吡咯烷酮(PVP)的γ-lgc曲线的双拐点特征,根据拟双平台现象求得烷基硫酸钠同系物对大分子的饱和簇集量Γ∞(mmol/L)和比饱和簇集量[Γ∞].由Γ∞-cP回归方程的斜率得到ROSO3Na-PEG及ROSO3Na-PVP体系的[Γ∞]reg分别为0.394和0.415m/n.[Γ∞]随表面活性剂疏水基链长、大分子分子量及浓度的变化均很小,t检验结果表明回归值[Γ∞]reg与实验值[Γ∞]exp之间无明显差异,因此超分子相互作用参数[Γ∞]可以被视为不变量.烷基硫酸钠同系物的类胶束与大分子形成软物质团簇的作用方式为静电超分子自组装. 相似文献