Chapter 6: Analysis of Copolymers

6.1 Infrared Spectroscopy

This technique has been used extensively for the determination of functional groups, in polymers and copolymers (Chapter 3) and in comonomer analysis (Chapter 4). Both these aspects are concerned with the determination of polymer structure. For example: the distinction between free and combined vinyl acetate in vinyl chloride vinyl acetate copolymers (Section 3.4.4); or the elucidation of the structure of methylmethacrylate (MMA) glycidyl methacrylate copolymers (Section 3.6.1); or the elucidation of the various types of unsaturation occurring in styrene butadiene copolymers (Sections 3.9.3, 3.9.4). Typical infrared (IR) spectra of copolymers are shown in Figures 6.1 to 6.4.

Figure 6.1: Acrylonitrile-butadiene-styrene terpolymer (Novodur W - Bayer Chemicals), benzene solution evaporated on sodium chloride windows.
(Source: Author s own files)

Figure 6.2: Near infrared spectra (a) polyacrylonitrile; (b) styrene-acrylonitrile copolymer (acrylonitrile content 25.7 wt%); (c) polystyrene.
(Source: Author s own files)

Figure 6.3: Styrene butadiene (SBR 15 M - Phillips Chemical Co.), benzene solution evaporated on sodium chloride window. (Source: Author s own files)

Figure 6.4: Infrared spectrum of ethylene propylene copolymer containing 85 mole% propylene. (Source: Author s own files)

Johnson-Plaumann and co-workers [1] used infrared and nuclear magnetic resonance spectroscopy (NMR) to quantitate the composition of various ethylene propylene copolymers. Absolute concentrations were measured by IR spectroscopy. An IR calibration curve was obtained by plotting the absorbance ratio 6.82 ?m/7.26 ?m versus concentration of monomer units.

Partnov and co-workers [2], on the other hand, measured the ratio of monomer units in ethylene ...