摘要:

AbstractThe effect of concentration of sodium polystyrene sulphonate on the elution volume in exclusion chromatography has been investigated using salt‐free water as eluent. A non‐linear increase in the elution volume has been observed with increasing injected sample concentration. Concentration‐dependent calibrations have been obtained which approach the universal calibration for uncharged polymers (dextrans) as polyelectrolyte concentration increases. The separation mechanisms are interpreted in terms of electrostatic and hydrodynamic interactions. A semi‐empirical model is proposed to predict concentration effects of linear polyions in exclusion chromatography and good agreement has been found between experimental and calculated elution

ISSN:0007-1641    

DOI:10.1002/pi.4980190601

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe elution behaviour of charged water‐soluble polymers (sodium polystyrene sulphonate) in both salt‐free and NaCl‐containing aqueous mobile phases has been investigated by size‐exclusion chromatography. A comparative analysis has been established between the results as a function of polyion and salt concentrations, which demonstrates that the chromatographic behaviour is similar in both cases. The variation of the slopes of the different concentration‐dependent calibration curves is discussed in terms of polyelectrolyte conformational changes. Finally, a semi‐empirical model has been developed to predict the dependence of the elution volume in either polyion or salt concentration, and its validity has been checked in a range from very dilute to moderate con

ISSN:0007-1641    

DOI:10.1002/pi.4980190602

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractTetraethylene glycol (TEG) or polyethylene glycol 200 (PEG200) was reacted with CH2Br2in a modified Williamson synthesis to form oxymethylene‐linked chains. Analytical and preparative gel permeation chromatography plus nuclear magnetic resonance spectroscopy were used to show that the product of reaction consisted of rings with degree of condensationn= 1−15 or more (i.e. 14 to 210 or more atoms in the rings formed from TEG) and chains with molecular weights up to 106and a wide molecular weight distribut

ISSN:0007-1641    

DOI:10.1002/pi.4980190603

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe properties of the fibrous clay sepiolite as a support for enzyme immobilization have been studied using urease. Simple adsorption does not result in enzyme inactivation and appears to be a valuable method of immobilizing the enzyme at high ionic strength. This behaviour has been related to the existence of protein‐clay hydrophobic interactions. The sepiolite‐supported urease has been characterized in terms of pH and ionic strength dependencies, thermal and storage stability, reusability, and kinetic parameters. These studies indicate that sepiolite is a valuable support for simple adsorption of enzy

ISSN:0007-1641    

DOI:10.1002/pi.4980190604

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractKinetic schemes proposed by three groups of workers for polymer pyrolysis have been critically examined, in order to resolve apparent anomalies, especially in the way in which the overall first‐order rate constant for volatile evolution by depropagation mechanisms, involving different modes of initiation and termination, have been interpreted. In one scheme, the treatment of rate was found to be inappropriate for changing‐volume systems, and the resulting rate expressions therefore cannot be recommended. When choice of units, conventions, and symbols was taken into account, the other schemes were found to be totally compatible. These schemes lead to identical expressions for the initial rate of evolution of a volatile product, provided the symbols are defined specifically according to the conventions chosen. These expressions are to be recommended for studies of this k

ISSN:0007-1641    

DOI:10.1002/pi.4980190605

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractBulk and surface properties of crosslinked and non‐crosslinked blends of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPOX) were studied for the elucidation of the behaviour of these materials in contact with blood. In the crosslinked blends the hydrophilic character increased with increasing PEO content, as concluded from swelling experiments and contact angle determinations. D.s.c. and dynamic mechanical measurements indicated the occurrence of phase separation in the blends and d.s.c. showed that on equilibration with water the PEO phase loses its crystallinity. F.t.‐i.r.‐a.t.r. analysis of the surface of crosslinked PPOX‐PEO films showed an enrichment of the surface with PEO.These observations indicate that the good blood‐compatibility of PPOX‐PEO blends might be explained by the presence of an amorphous, PEO‐enriched, hydrop

ISSN:0007-1641    

DOI:10.1002/pi.4980190606

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

摘要:

AbstractThe diffusion of cesium and chloride ions through epoxide membranes was studied under a variety of conditions including self‐diffusion, the presence of other salts in the aqueous solution, an excess of either reagent used in the manufacture of the membrane, the addition of various fillers in the epoxide network and two temperatures. At 23°C, the diffusion coefficientDwas (2–6) × 10‐13cm2s−1for most systems, except when the epoxide was prepared with an excess of the dioxirane component or when untreated glass beads were added to the network. In the latter instanceDincreased and most notably with glass beads. On the contrary, addition of sand to the epoxide resulted in a more effective barrier against diffusion as shown by a decrease inD.It is concluded that most of these materials should be suitable for the confinement of low and medium activity nucle

ISSN:0007-1641    

DOI:10.1002/pi.4980190607

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980190609

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980190613

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980190616

出版商:John Wiley&Sons, Ltd    

年代:1987

数据来源: WILEY