Chapter 3: Determination of Functional Groups in Polymers

A variety of instrumental techniques have been used to determine functional groups in polymers and to elucidate the detail of polymer structure. These include infrared spectroscopy, near-infrared spectroscopy including Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and proton magnetic resonance (PMR) spectroscopy, chemical reaction gas chromatography, pyrolysis gas chromatography (PyGC), pyrolysis gas chromatography mass spectrometry, pyrolysis NMR spectroscopy, X-ray fluorescence spectroscopy (XRFS), and also newer techniques such as time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), tandem mass spectrometry (MS-MS), matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS), microthermal analysis, atomic force microscopy (AFM), and various X-ray methods including scanning electron microscopy (SEM) and energy dispersive analysis using X-rays (EDAX).

Functional groups that may have to be determined include unsaturation, hydroxy, carbonyl, carboxyl, alkyl, aryl, alkoxy, oxyalkylene, nitrile, ester, amino, nitro, amide, amido, imino, and epoxy groups. Comonomer ratios, isomers, and short-chain branching are all structural features of polymers that may have to be elucidated in order to obtain a complete picture of polymer structure.

3.1 Hydroxy Groups

3.1.1 Acetylation and Phthalation Procedures

Chemical methods for the determination of hydroxyl groups in polymers are based on acetylation [1-12], phthalation [2], perchloric acid catalysed acetylation [2, 4, 5], reaction with beta-nitro phthalic, anhydride [5, 8], pyromellitic anhydride [6] and reaction with phenyl isocyanate [2, 5] or when two adjacent hydroxyl groups are present in the polymers, by reaction with potassium periodate [1].

The reactions on which these methods are based are as follows:

Acetylation:

Phthalation:

Reaction with phenyl isocyanate: