Microscopic Characterization of Polymers

Most of the methods used for the microscopic characterization of emulsion polymers in terms of their macromolecular composition, molecular weight and crosslinking require the removal of water. For this reason the investigaHons are performed on the dry polymer film or on freeze-dried samples. The methods employed are the standard techniques of polymer characterizaHon (34-36). 

Some of the measurements are performed on soluHons of the polymer in organic solvents such as tetrahydrofuran or dimethylformamide. Because of their high molecular weight and their partial crossHnking, complete dissolution of an emulsion polymer is often difficult (see Sect 3.3.2), and the information that can be provided by these methods is in such cases rather limited. 

The chemical composition of an emulsion polymer sample can for instance be determined by Fourier transform infrared (FTIR) spectroscopy [37]. The measurement is performed on a polymer film. QuantitaHve analysis involves comparison of the spectra obtained with those of standard calibraHon substances. 

An alternative or complementary method is pyrolysis gas chromatography. In this technique the polymer is rapidly heated causing depolymerization or decomposition and the products are separated and detected gas chromatographically [34]. 

Polymer composition can also be determined by H and NMR [38] on dilute samples of the polymer in an organic solvent NMR analysis also enables end group analysis and to a Hmited extent monomer sequence studies (for example in terms of triad distributions). 

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