Vibrational spectroscopy polymerisation

Here, we describe the use of vibrational spectroscopy to monitor the progress of polymerisation reactions in situ. Figure 1 shows the results of monitoring the polymerisation of an fluorinated acrylate ester similar to that used by DeSimone [1 la]. The reaction was carried out in scC02 (200 bar) with AIBN, a common radical initiator. Under these conditions both the monomer and the final polymer are soluble in scC02 so the mixture remains as a single phase throughout the reaction. 

Vibrational spectroscopy The question thus arises as to the nature of occluded aniline in the ferric hydrogen sulphate and zirconium hydrogen phosphate hosts neutral, protonated, polymerised, or a mixture of these forms. 

IR spectra of PETP films were obtained, with an excellent signal-to-noise ratio, by diffuse reflectance measurements on a KBr matrix using FTIR spectroscopy. All the spectra exhibited a new band at 1684 cm/1, characteristic of the C = 0 stretching vibration of a terminal acidic function in the presence of internal hydrogen bonds. These acidic functions may be used to monitor polymerisation rate. 19 refs. 

A sample (50-60 mg) is hot-pressed at a temperature of 180 C to obtain a film of about 0.05 mm thickness, and the IR spectrum is recorded and compared with standard reference spectra. Difficulties will be encountered in distinguishing between a mixture of PVC and EVA and VC/VA copolymer. The main difference is seen in changes to the C-H stretching vibration bands of PVC in the region of 3030-2900 cm due to the presence of (CH2) units in the polymerised ethylene portion of EVA. Equally difficult to detect is CPE, where the same effect is observed. Pyrolysis/GC and NMR spectroscopy are used as confirmatory techniques, with the latter also being used to quantify some polymeric compounds. 

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