Stefano Stefano   39-08-02 00:00 이는 분석화학에 관한 용어이고 분자량의 크기에 따라 분석할때 동일 분석 column을 빠져나오는데 소요되는 retention time이 같은 곳에 여러 물질이 섞여 나오는 현상을 말하는 것 같습니다. 만일 그렇다면 그 값이 클수록 분리성능이 떨어지는 것을 의미하겠습니다. 다음 자료와 참고문헌을 참고하세요 Local polydispersity is the term describing the variety of molecules present at the same retention volume in size exclusion chromatography (SEC) analysis. In the analysis of a linear homopolymer, local polydispersity is generally attributed to the effect of axial dispersion: it can cause molecular size variety (i.e., imperfect resolution) at each retention volume and thus local polydispersity in the molecular weight. In the analysis of polymer blends (copolymers and branched polymers), it is possible to have local polydispersity, even when the resolution is perfect, because molecules of different compositions (or degrees of branching) can have the same molecular size in solution. Conventional SEC interpretation assumes no local polydispersity if the axial dispersion effects are negligible. Three methods are currently available for detecting local polydispersity by using a combination of differential refractive index, light scattering, and viscometer detectors: the chromatogram comparison method, the conventional calibration curve comparison method, and the universal calibration comparison method. Here we experimentally assess these three methods using polymer blends and emphasize the chromatogram comparison method. All three are shown to be useful for assessing triple detector systems, but they are capable of detecting local polydispersity due to molecular heterogeneity only for very large differences in specific refractive index increments in the blend components. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 370-383, 2001 REF: http://www3.interscience.wiley.com/cgi-bin/abstract/80002802/ABSTRACT 이는 분석화학에 관한 용어이고 분자량의 크기에 따라 분석할때 동일 분석 column을 빠져나오는데 소요되는 retention time이 같은 곳에 여러 물질이 섞여 나오는 현상을 말하는 것 같습니다. 만일 그렇다면 그 값이 클수록 분리성능이 떨어지는 것을 의미하겠습니다. 다음 자료와 참고문헌을 참고하세요 Local polydispersity is the term describing the variety of molecules present at the same retention volume in size exclusion chromatography (SEC) analysis. In the analysis of a linear homopolymer, local polydispersity is generally attributed to the effect of axial dispersion: it can cause molecular size variety (i.e., imperfect resolution) at each retention volume and thus local polydispersity in the molecular weight. In the analysis of polymer blends (copolymers and branched polymers), it is possible to have local polydispersity, even when the resolution is perfect, because molecules of different compositions (or degrees of branching) can have the same molecular size in solution. Conventional SEC interpretation assumes no local polydispersity if the axial dispersion effects are negligible. Three methods are currently available for detecting local polydispersity by using a combination of differential refractive index, light scattering, and viscometer detectors: the chromatogram comparison method, the conventional calibration curve comparison method, and the universal calibration comparison method. Here we experimentally assess these three methods using polymer blends and emphasize the chromatogram comparison method. All three are shown to be useful for assessing triple detector systems, but they are capable of detecting local polydispersity due to molecular heterogeneity only for very large differences in specific refractive index increments in the blend components. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 370-383, 2001 REF: http://www3.interscience.wiley.com/cgi-bin/abstract/80002802/ABSTRACT