Functionality fractions

As a typical application, the separation of an octylphenoxy-terminated PEO with respect to the terminal groups by LCCC is presented in Fig. 17.6. Similar to previous investigations on RP-18 stationary phases (Gorshkov et al., 1990 Pasch and Zammert, 1994), the critical eluent composition was achieved with methanol-water 86 14% by volume. Five well-separated peaks appeared in the chromatogram, which could be identified by MALDI-TOF mass spectrometry as being different functionality fractions. Accordingly, separation took place strictly with respect to the chemical structure of the end groups. 

In agreement with the expected composition of the sample, the most intense elution peak can be assigned to the a-octylphenoxy-co-hydroxy functionality fraction 2. The other elution peaks can be assigned to the following structures ... 

The contour plot clearly shows five spots corresponding to the five functionality fractions, compared to Fig. 17.6, with fraction 2 being the main fraction containing the a-octylphenoxy-co-hydroxy oligomers. In addition, a,CO-di(octylphenoxy) oligomer fractions and fractions having butylphenoxy end groups are obtained. It is obvious that the fractions have very similar molar masses. 

The 2D experiment yielded separation with respect to functionality and molar mass, and FTD and MMD could be determined quantitatively. For calculating FTD, the relative concentration of each functionality fraction must be determined. These concentrations are equivalent to the volume of each peak in the contour plot. With the... 

Using the same chromatographic system as given in Fig. 17.19 we were able to investigate modified polyamide 6.6 by 2DLC. The samples were modified by amidation with propionic acid, introducing additional functionality fractions to the system. In total, seven different species were expected to be present in the samples (see Table 17.1). 

Although seven different functionality fractions are expected to be present in the sample, the contour plot in Fig. 17.21 reveals only two different elution areas. The fraction that elutes at about 3 mL in the first dimension (ordinate direction) can be assigned tentatively to a PA 6.6 having an acid and an amine end group by comparing the results with the plot in Fig. 17.19. Accordingly, the later eluting fractions are due to the other different linear functionality fractions, as shown in Table 17.1. 

Table 17.1 Functionality Fractions in PA 66 Modified with Propionic Acid...

If the polyester synthesis is performed with equimolar amounts of diol and diacid, then, in addition to hydroxy, carboxy-terminated oligomers, dihydroxy- and dicarboxy-terminated oligomers are formed, as shown below. In a thermodynamic equilibrium, the molar ratios of the three functionality fractions should be 2 1 1, respectively. 

FIGURE 17.25 LCCC separation of a poly(l,6-hexanediol adipate) (a) and SEC analysis of the functionality fractions (b) from Kriiger et al., 1994 (Copyright 1994 from Journal of Liquid Chromatography, 1994, p. 17 by Kruger et al. Reproduced by permission of Taylor Francis Group, LLC., http //www.taylorandfrancis.com). 

TABLE 17.2 Functionality Fractions in Poly-Hexanediol Adipinate Found in Fig. 17.25... 

The C3 family of materials [11-13] exhibits this chemical stability due to a highly functionalized fraction of sp2 carbon [14-17], but in addition contains a carbon fiber backbone in its second bulk component. Carbon fibers [18-21] are the ordered variant of interlaced ribbons in fibers the anisotropic sp2 basic structural units are oriented in one direction [20] by various mechanisms during synthesis. The result is a high... 

Figure 4. Typical surface functions—fractions of sites covered...

The fraction (3 arises from the simultaneous probability that one functionality has reacted and the other two remain unreacted. The factor 3 takes into account the three undistinguishable possible elections of the reacted functionality. Fractions y and 8 were obtained using similar arguments. It may be verified that... 

Using appropriate analytical methods, the type and concentration of the different functionality fractions must be determined and, within each functionality, the molar mass distribution has to be obtained. To do this, two different methods must be combined, each of which is preferably selective towards one type of heterogeneity. For example, a chromatographic method separating solely with respect to functionality could be combined with a molar-mass-selective method. Another approach would be the separation of the sample into different molar mass fractions which are then analyzed with respect to functionality. 

For copolymers, in particular random copolymers, instead of discrete functionality fractions a continuous drift in composition is present (see Fig. 3). To determine this chemical composition drift in interrelation with the molar mass distribution, a number of classical methods have been used, including precipitation, partition, and cross-fractionation [2]. The aim of these very laborious techniques is to obtain fractions of narrow composition and/or molar mass distribution which are then analyzed by spectroscopy and SEC. 

For the separation of the polyesters with respect to functionality, LC-CC was used the critical point of adsorption of the polymer chain corresponding to an eluent composition of acetone/hexane 51 49 (v/v) on silica gel. The critical chromatogram of a polyester sample together with the functionality fraction assignment is given in Fig. 22 and Table 4. The ether peaks are obtained due to the formation of ether structures in the polyester samples. 

The molar mass distributions of the functionality fractions were determined by preparatively separating the fractions and subjecting them to SEC. The SEC chromatograms of fractions 1-9 are summarized in Fig. 23. For a number of fractions oligomer separations were obtained, which could be used to calibrate the SEC system. 

The best way of fingerprinting the present very complex sample was a coupled 2D experiment in the coordinates LC-CC and SEC. As can be seen from the contour plot in Fig. 24, all structural features including the functionality fractions... 

The analysis of a technical poly(ethylene oxide) with respect to chemical composition and degree of polymerization has been performed by Pasch and Hiller [210]. This investigation was conducted under conditions which are common for HPLC separations, i.e. sufficiently high flow rate, moderate sample com-centration, and on-flow detection. Using an octadecyl-modified silica gel as the stationary phase and an eluent of acetonitrile/deuterium oxide 50 50 (v/v), the sample was separated into different functionality fractions (see Fig. 38). The major fraction of the sample eluting between 14 and 25 min exhibited a partial oligomer separation. 

Matrix design/ Molecular Functionality - Fractionation, Synthesis... 

Rouquier S, Blancher A, Giorgi D (2000) The olfactory receptor gene repertoire in primates and mouse evidence for reduction of the functional fraction in primates. Proc Natl Acad Sci USA 97 2870-2874... 

The energy shift of the main line [by definition, the main line corresponds to the eigenfunction that has the largest perturbed basis function fractional character and is usually more intense than extra lines (see Section 6.2.1)] switches sign as one passes through this J-value. 

AB u Breakage function, fraction of particles of size D that are broken to size D ... 

The application of thermal techniques to study the nature of the volatile thermal fragments from petroleum asphaltenes has produced some interesting data relating to the polynuclear aromatic systems (18-22). These thermal techniques have produced strong evidence for the presence of small polynuclear aromatic systems (one to four rings) (14), and application of the techniques to the various functional fractions has confirmed the general, but unequal, distribution of these systems throughout asphaltenes. 

Figure 4. HPLC chromatograms of asphaltene fractions. HPLC emphasizes the complexity of the functional fractions.

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