Poly , tactic polymer conversion

The poly(propylene oxide) obtained at low conversion has an enantiomeric purity of around 30%, is not homogeneous from the point of view of stereoregularity (or stereoselectivity), and can be separated into fractions of different tacticity and optical activity, the latter being greater for polymers of higher stereoregularity. 

Despite these obstacles, LC-NMR systems are increasingly available and increasingly applicable to real problems. SEC-NMR canbe used to establish accurate MMDs for relatively low-Mr polymers by online measurement of the number-average molar mass (Hatade etal, 1988 Ute et al, 1998). However, SEC//MALDI seems to be a more attractive option for this application. Determination of the chain regularity is a strong aspect of NMR (see also Section 7.4.2.1) and in combination with LC or SEC, tacticity distributions can be determined (Kitayama et al, 2000 Ute et al, 2001). The chemical heterogeneity of high-conversion poly[styrene-co-ethyl acrylate] (Kramer etal, 1999) and the functionality-type distribution of low-molar-mass polyethylene oxide (Pasch 8c Hiller, 1999) were studied by online SEC-NMR. 

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