Molecular weight polymer from assignment

Figure 6. Assignment of resonances in C-13 NMR spectrum of low-molecular-weight polymer from 2,4,6-trichlorophenoxide...

There are a number of studies in the literature that describe the use of supercritical fluids to extract cyclic and low molecular weight oligomers from polymers. U.S. Patent 4,306,058 (Copelin, 1981), assigned to E. I. du Pont, describes the removal of cyclic oligomers from polyoxyalkylene. For instance, bubbling supercritical propylene at conditions of 100°C and 80 bar through the... 

The IR spectrum of 3 differs from 2 by the appearance of new bands at 845 cm V870 cm 1 which are characteristic of the end-block Si(CH3)3 group (13). The intensity of the bands decrease with increase in polymer molecular weight thus supporting the assignment. There is also a significant decrease in the OH absorption confirming an anhydrous polymer. 

The presence of hydroxyl end groups in PPG can be assigned from 13C NMR data (Figure 24), with resonances (g) observed between 65-68 ppm in the spectrum shown in Figure 24. There are two different resonances here (g) due tacticity effects in the polymer (meso/racemic (m/r) isomerisation of the terminal dyad). Estimations of the amount of these ends in the polymer, along with the average molecular weight of the PPG, can be made from the 13C NMR data. 

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