Poly correlation peaks

Figure 1.25 (a) The broadband decoupled COSY spectrum of poly(vinyl alcohol) under the same conditions as Figure 1.24 (b) expansions of the CH diagonal peaks and the CH/CH2 correlation peaks (c) schematic representation of the correlation peaks, with assignments given in Table 1.5. Reprinted with permission from [64]. 

Table 1.5 Assignment of the correlation peaks in the broadband decoupled COSY spectrum of poly(vinyl alcohol) in Figure 1.25 (from [64])...

Another recent example of the use of DQ MAS NMR spectroscopy is given hy the study of molecular scale miscibility of poly(butylenes terephtalate)-6Zoc -poly(tetramethylene oxide) multiblock (PBT-6Zoc -PTMO) copol5miers (123) by looking for correlation peaks between signals from the hard and soft blocks. 

Figure 4.3 Correlation between UV peak intensity (e), full width at half maximum (FWHM), and a of various poly(dialkylsilane)s and poly(alkyl(aryl)silane)s in THF at 30°C.

Figures 13.7 and 13.8 are two examples of two-dimensional NMR spectroscopy applied to polymers. Figure 13.7 is the proton homonuclear correlated spectroscopy (COSY) contour plot of Allied 8207A poly(amide) 6 [29]. In this experiment, the normal NMR spectrum is along the diagonal. Whenever a cross peak occurs, it is indicative of protons that are three bonds apart. Consequently, the backbone methylenes of this particular polymer can be traced through their J-coupling. Figure 13.8 is the proton-carbon correlated (HETCOR) contour plot of Nylon 6 [29]. This experiment permits the mapping of the proton resonances into the carbon-13 resonances.

In contrast, in the case of poly(cyclohexyl methacrylate), the calculated correlation time is much longer. Its value agrees nicely with a strong line broadening of the ring carbon NMR peaks. 

Morphological changes, which are classified into four groups, have been correlated to the degree of topotactic control. Thermal analysis has been studied on DSP poly-DSP in some detail. Two main endothermic peaks of as-polymerized poly-DSP crystals are characterized as thermal depolymerization in the crystalline state and crystal melting point followed by thermal depolymerization in the molten state. From the results of the studies on the heat treatment of as-polymerized polymer crystals, a reversible topochemical processe has been established. 

Fig. 14 3D- H, C, F correlation of poly(l-chloro-l-fluoroethylene) with slices at 5( F) = -98.2 (a), -99.4 (b), -100.7 (c) (d) schematic illustration of the 3D spectrum with relative positions of the shoes. Each shce in (a)-(c) displays two correlation signals representing the two CHj groups adjacent to a CF moiety. The polymer tacticity can be determined as follows the splitting of each signal reveals the stereochemistry of individual CFCI-CH2-CFCI diads, the two protons at a methylene carbon being chemically inequivalent in meso (m) and chemically equivalent in racemic (r) diads. Consequently, the fluorine atoms can be assigned to rr (a), rm (b) or mm triads (c). The possible tetrad structures can be determined by looking for identical C-H cross-peaks in different F slices e.g. the A cross-peaks in (a) do not occur in the other two sUces therefore, the methylene group A shows only correlations with F atoms in mm triads and must be centred in an mmm tetrad, etc. Reproduced, with permission, from ret 100. Copyright 1996 American Chemical Society.

Diffusion of materials out of a PSi sensor was monitored by Koh and coworkers in a proof-of-concept device for monitored drug delivery applications [29], Poly-methyl methacrylate (PMMA) containing 0.25 mg/ml caffeine was first cast onto a freestanding PSi thin film. Exposure of this composite material to a pH 7 buffer caused a time-dependent decrease in the intensity of reflection at a fixed wavelength, or alternatively a time-dependent blue shift of the peak, corresponding to diffusion of the small molecule out of the PMMA-PSi composite. These data correlated well with appearance of caffeine in the buffer solution, as measured by UV-Vis spectrophotometry. 

A sample of poly(vinyl bromide) in tetrahydrofuran was injected into the same GPC column used in Exercise 4.26. The refractive index difference between the eluted solution and pure solvent was measured and plotted against the elution volume. The result was a broad peak the maximum of which occurred at an elution volume of 180 cm . Calculate the average molecular weight of the polymer both according to (a) correlation derived in the preceding exercise and (b) Eq. (4.144) that correlates M , with the peak maxima. 

Two-dimensional (2D) NMR spectroscopy has recently been used to make absolute tacticity assignments without any other supports.195-208 An early successful example is H COSY analysis of poly(vinyl alcohol).198,199 Figure 17 shows a broad-band decoupled H COSY spectrum of poly (vinyl alcohol)199 and illustrative assignments for the correlations between triad peaks of methine proton and tetrad peaks of methylene protons. Expected connectivities between triad and tetrad are as follows ... 

D INADEQUATE (incredible natural abundance double-quantum transfer experiment) enables direct observation of neighbouring l3C-l3C correlation and has been applied to poly(vinyl alcohol)199 and polypropylene.206 For example, the CH carbon in the rrrr pentad has two cross-peaks with hexad methylenes of rrrrr and rrrrm. 

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