Continuous spin fractionation

A related technique for the fractionation of large amounts of polymer, continuous spin fractionation (CSF), has also been recently disclosed (59). 

Xiong X, Eckelt J, Wolf BA, Zhang Z, Zhang L (2006) Continuous spin fractionation and characterization by size-exclusion chromatography for styrene-butadiene block copolymers. J Chromatogr A 1110 53-60... 

Two patented large-scale techniques, based on liquid-liquid phase separation, are the continuous polymer fractionation (CPF) and the continuous spin fractionation (CSF)." The experimental setup of these two techniques will be presented in the next two sections (sections 2.04.2.1 and 2.04.2.2), which are followed by the description of two chromatographic methods, namely, the Baker-Williams fractionation (section 2.04.2.3) and the phase distribution chromatography (PDC) (section 2.04.2.4). 

Figure 3.32. High quality, nearly spherical powder prepared by high-pressure gas atomization from the melt and proper sample length, L. The x-ray powder diffraction data were collected from a continuously spinning sample (20 mm diameter and 1 mm deep) prepared as shown in Figure 3.22. Notations are the same as in Figure 3.29. The powder contains a small fraction of a second phase, which is identified by the series of vertical bars shifted downwards. The inset shows the scanning electron microscopy image of the powder morphology. (Powder courtesy of Dr. I.E. Anderson.)...

Dr. John Eckelt studied chemistry at the Johaimes Gutenbei -Umversttat Mainz and obtain his PhD in the field of thermodynamics of polymer solutions. During his PhD he invent, together with Prof. Wolf, the continuous spin ftactionation, a large-scale fractionation method. Since 2007 he has b n the CEO of the WEE-Solve GmbH, a service provider for polymer fractionation, rheological measurements, and contract research in the field of physical chemistry. 

It was shown that REDOR or its variants can be used when one coupling partner is a quadrupolar spin.113,114 However, there are some limitations, such as the fact that only a fraction of the spin-1, nuclei are involved in the dephasing.115 Accordingly, more specific dephasing methods have been proposed for this type of system. One is TRAPDOR (transfer of population in double resonance), which uses continuous irradiation.116 The other is REAPDOR (rotational-echo, adiabatic passage, double resonance),117,118 which is a more straightforward extension of REDOR. 

PVDF. This polymer can contain head-to-head and tail-to-tail sequences, as illustrated in Figure 7-25. Because the 19F nucleus has a spin number of 1/2 and its natural abundance is 100%. 19F NMR spectroscopy is a powerful tool for studying fluoropolymers like PVDF. The fluorine atoms are the little yellow balls and you ll notice that one of the units in Figure 7-25 has been put in backwards, giving a head-to-head and tail-to-tail sequence. The peaks marked A, B, C and D in the spectrum of PVDF (Figure 7-26) correspond to the fluorine atoms labeled in the same way in the figure. Of course, what you would really like to know is the number fraction of VDF monomers that are incorporated backwards into the chain. This information can be obtained from the relative intensities of the bands, but to extract it we have to revisit probability theory. (Oh no the nightmare continues )... 

It is straightforward to show that the special case of a spin having an axially synunetric g tensor (widely used as a tutorial example for the theory behind ESR spectroscopy ), when direct use is made of Eqs. (2.18) and (2.18 )> leads to a continued fraction of the same kind as Eq. (2.19) with the expansion parameters... 

In this section we shall detail the analytical derivation of the absorption spectrum for a magnetic species in a triplet spin state tumbling in a viscous disordered liquid. This an ytical structure consists of the sum of product of continued fractions. The standard Mori structure of Eq. (2.19) is recovered in the absence of orienting potentials. 

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