TABLE OF CONTENTS Most methods for the determination of ester groups in polymers are based on the following procedures:
Saponification.
Zeisel procedures, based on hydriodic acid.
Pyrolysis - gas chromatography.
Physical methods, e.g., infrared spectroscopy and nuclear magnetic resonance spectroscopy.
Ester groups occur in a wide range of polymers (e.g., polyethylene terephthalate) and in copolymers such as, for example, ethylene vinyl acetate. The classical chemical method for the determination of ester groups, namely, saponification, can be applied to some types of polymer. For example, copolymers of vinyl esters and esters of vinyl esters and esters of acrylic acid, can be saponified in a sealed tube with 2 M sodium hydroxide. The free acids from the vinyl esters were determined by potentiometric titration or gas chromatography. The alcohols formed by the hydrolysis of the acrylate esters were determined by gas chromatography. Vinyl acetate ethylene copolymers can be determined by saponification with 1 N ethanolic potassium hydroxide at 80 C for 3 hours and back titration with standard acid or by saponification with p-toluene sulfonic acid and back titration with standard acetic acid [49, 50].
Polymethyl acrylate can be hydrolysed rapidly and completely under alkaline conditions. On the other hand, the monomer units in polymethyl methacrylate prepared and treated similarly are resistant to hydrolysis [51] although benzoate end-groups react readily [52]. Only about 9% of the ester groups in polymethyl methacrylate reacted even during prolonged hydrolysis; hydrolysis of polymethyl acrylate was complete in 0.5...
