ISSN:0935-6304    

DOI:10.1002/jhrc.1240020802

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240020803

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractGrignard and trichlorosilane coupling methods have been applied to the synthesis of surface‐modified silicas carrying alkyl chains of varying length, terminally substituted by a hydroxyl group. The new phases have been characterized chromatographically using aromatic hydrocarbons, substituted anilines and metal acetylacetonate

ISSN:0935-6304    

DOI:10.1002/jhrc.1240020804

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe glass transition temperatures, Tg, of polystyrene, poly (vinyl chloride) and poly(methyI methacrylate) have been determined from gas chromatographic measurements using n‐hexane, n‐heptane, meta‐xylene and para‐xylene solvents. The glass transition temperatures were detected on the z‐shaped retention diagrams which were produced from the plot of the logarithm of the specific retention volumes of the above‐mentioned solvents against the reciprocal of temperature, i.e. log V gºvs. 1/T. The glass transition temperature is specified by the temperature where the slope of log V gºvs. 1/T changes abruptly. The observed glass transition temperature of polystyrene produced by this technique was found to be in good agreement with those produced by other techniques such as the differential scanning colorimeter.The industrial importance of the glass transition temperature, Tg, might be due to the dramatic changes in the physical properties of the polymer, such as hardness and elasticity, which take place in the vicinity of this temperature. However, perfectly crystalline polymers do not exhibit glass transitions, because their chains are incorporated in regions of three‐dimensional order, called crystallites. Completely amorphous polymers and semi‐crystalline polymers usually exhibit both glass t

ISSN:0935-6304    

DOI:10.1002/jhrc.1240020805

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractQuantitative evaluation of TLC by direct photometric scanning is a promising method, in view of the development of cheap microprocessors: soon instruments for digital scanning will be commercialy available. In this paper we describe a multilayer model which seems to be a good approximation for solving the radiation transfer equation in the case of layer models with a gradient in an inward direction. Changes of remitted and transmitted light, in cases where a band lies in different layers, are presented. Examples shown are: the absorbance profile of a chromatographed band in the direction of scanning is approximated to that of an isosceles triangle; the concentration of the band is uniform, e.g. 0.3 A. U.; the concentration of the band is changing from 0 to 2.0 A. U. These results will serve to set up the correct algorithms for digital scanning and simultaneous determination in TLC.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240020806

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractIn the Part 1 of this series a new equation for determining the Rmvalues in TLC with mixed mobile phases was proposed and examined by using the parameter m, which is a measure of energetic heterogeneity of the adsorbent surface with regard to the adsorbing molecules (admolecules).The numerical values of m, evaluated for 13 chromatographic systems, have been compared with that of the Ościk's parameter A, which characterizes solute‐solvent interactio

ISSN:0935-6304    

DOI:10.1002/jhrc.1240020807

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240020808

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240020809

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240020810

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

ISSN:0935-6304    

DOI:10.1002/jhrc.1240020811

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY