And crystalline fractions

Figure 30 Variable-temperature solid-state NMR spectra (relative intensities distorted due to different relaxation rates) (a) 29Si (referenced to Q8M8 (Bruker) (b) 2H (isotropic peak truncated to show hem and crystalline fractions).285 Reprinted with permission from Mueller, C. Schmidt, C. Frey, H. Macromolecules 1996, 29, 3320-3322. 1996 American Chemical Society.

The apparent kinetic parameters are expressed as the summation of the terms corresponding to amorphous and crystalline fractions. 

Table 1 Coherence Lengths and Crystalline Fractions Inferred from Diffraction Results8...

No really new crystal structures have been found in these oriented PANI systems. The oriented diffiaction has been explored to obtain answers to several questions about the relationship between the amorphous and crystalline fractions in PANI (Fischer el al. 

Have the PPI component function as a flexible spacer of a terminally placed, rigid, crystallizable component derived primarily from gly-colide so as to allow for facile molecular entanglement to create pseudo-crosslinks, which in turn maximize the interfacing of the amorphous and crystalline fractions of the copolymer, leading to high compliance witiiout compromising tensile strength... 

Characterization techniques being used in the 1950s and 1960s, such as NMR, infrared spectroscopy. X-ray diffraction, microscopy etc., could only measure the average values this was also the case for the molar mass measurement. In some cases, there was a need to separate the amorphous and crystalline fractions by solvent extraction methods because no other means to measure the distributions were available. 

DETERMINATION OF THE THERMOCONDUCTIVITY OF THE AMORPHOUS AND CRYSTALLINE FRACTIONS OF POLYETHYLENE. 

Figure 38 Subspectra Si AI)-S4( AI) calculated from the Al MAS NMR of the metakaolin-based geopolymers. The signals reflecting the amorphous and crystalline fractions of the prepared geopolymers are marked as the "amorph. phase" or"cryst. phase", respectively. Reprinted with permission from [31]. Copyright, John Wiiey and Sons Ltd, 2013.

The conclusion is that one cannot in this case equate the melt entropies of the atactic (i.e. amorphous) and the isotactic (crystalline) stereo-isomers. This is borne out, to some extent, by the finding that the melt volumes of the amorphous and crystalline fractions also differ by about 1% (7). It seems therefore that the peculiar room temperature volumetric behavior is merely a reflection of the difference in stereo-isomeric properties. 

In most cases, three polymer populations are obtained a highly isotactic and crystalline fraction, ranging from 25% to 95%, whose molar masses reach lO gmoP a second one amorphous with high molar masses and a third one... 

Allen, Booth, and Jones (96) investigated the intrinsic viscosity-molecular weight behavior of amorphous and crystalline fractions, as well as whole polymers of poly(propylene oxide), and found that their combined behavior could be described by the following Mark-Houwink equations. 

Since the amorphous and crystalline fractions of a high polymer cannot be separated mechanically, e.g. by filtration as for the separation of liquid solutions from crystalline complexes, the phase behaviour of polymer-salt systems is more difficult to chart than that of liquid solvents. However, many techniques, e.g, polarized light microscopy, differential scanning calorimetry, " X-ray diffraction and NMR, have been used to study the partition of the salt and the temperature dependence of phase behaviour. 

Fig. 8.13. (a) The F REV-8 chemical shift of PTFE samples of varying crystaUinity obtained at 259°C. (b) The F REV-8 chemical shift of a PTFE sample with 68% crystallinity, showing the decomposed line shapes of the amorphous and crystalline fractions. (Reproduced from Ref. [27]. 1980 American Chemical Society.)... 

The analysis of the F spectrum was accomplished by decomposing the line shapes into the amorphous and crystalline fractions. 

For isotactic polypropylene, as shown in structure 9.2, six different placements are possible when considering triads. C-NMR spectroscopy can be used to determine isolated head-to-head and tail-to-tail units in polypropylene (PP). Polypropylenes produced using vanadyl catalysts possessed the normal head-to-tail structure [1]. More detailed examination, however shows that the amorphous fractions isolated from these PP do show (IR) absorption at 13.3 pm pointing to the presence of methylene sequences of two units, which can only mean tail-to-tail arrangement of propylene units does occur. A very small absorption peak at 13.3 pm was also found in the spectrum of the crystalline fractions. Polypropylenes prepared with catalysts based on VCI3 show only the normal head-to-tail arrangement in both amorphous and crystalline fractions, as do polymers prepared from TiClj catalyst. The amount of propylene units coupled tail-to-tail was estimated to range from 5 to 15% for the amorphous and from 1 to 5% for the crystalline fractions. 

Mobile amorphous, rigid amorphous, and crystalline fractions for iPS isothermally crystallized at 140 °C for 12 h as a function of temperature on heating at 10K min. For details see text. Reproduced with permission from Schick, C. Anal. Bioanal. Chem. 2009, 395,1589-1611... 

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