Endgroup analysis

Using IR spectroscopy and NMR, one can analyze the chemical structure of PA. The molecular weight and molecular weight distribution can be analyzed by endgroup analysis, viscometry, and high-pressure liquid chromatography (HPLC). The crystalline order can be analyzed by WAXS, small-angle X-ray spectroscopy... 

The molecular weights of PAs are often not very high (M > 20,000) in this range M can be determined by endgroup analysis or, less frequently, by osmometry, Mw can be determined by light scattering. Both M and Mw can indirectly be determined by HPLC. 

Endlinked PDMS. Linear polydimethylsiloxanes with vinyl endgroups were supplied by Dow Corning Corporation. Three different molecular weight ranges were employed. Membrane osmometry yielded values for Mj, of 16,000, 24,000, and 37,000 g/g-mole. Endgroup analysis using mercuric acetate (5) gave vinyl contents of 0.47 0.03, 0.24 0.02, and 0.15 0.02 per cent, corres-... 

When free radical initiation is because of the addition of the radical to one end of the double bond, then we may expect that the radical would be attached to the end of the Polymer chain. The presence of such end fragments of the initiator has been confirmed for radical polymerisations and with several monomers by endgroup analysis. 

Except the method of endgroup analysis all the above methods are based on the determination of properties of polymer solution. The Molecular weight of the polymer is related to its chain length or to the degree of polymerisation (DP) defined as the ratio between the Molecular weight of polymer and that of the monomer. 

The Endgroup analysis method can be carried out by using the following chemical and Physical Methods ... 

Thus the Endgroup analysis method is quite useful for the determination of the Molecular weight of the polymers that possesses endgroups which can be determined precisely by some analytical reaction. In addition to Polyamides and polyesters, where the Endgroup analysis method is commonly used, the method can also be used for polysaccharides. 

No general procedures can be outlined for endgroup analysis in addition polymers due to the variety of type and origin of the endgroups. When the polymerisation kinetics is known analysis can be done for initiator fragments containing identifiable... 

Table 3.4. Radical transfer reactions involving OH radicals and sulfonated substrates demonstrated by endgroup analysis 1401...

Fig. 12.23. Triton X-405 analyzed by positive-ion nanoESI-MS. (a) Molecular weight distribution appears trifold as [M+NH4] ", [M-i-2NH4], and [M+3NH4] ions series (b) only the triply charged ions undergo significant dissociation upon NSD to yield low-mass fragment ions (c) QD spectrum of the fragment ion at m/z 233 for endgroup analysis. Reproduced from Ref. [78] with permission. Elsevier, 2009.

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