Schneider, A., Wünsch, M.and Wolf, B. A.

"An apparatus for automated turbidity titrations and its application to copolymer analysis and to the determination of phase diagrams"

Abstract: We present an apparatus for quick and reliable determinations of transmission curves speci-fying the dependence of the light intensity (normalized to that of the primary beam) passing a test solution on the amount of standard solution added. This device is used for two different purposes, namely for the analysis of copolymers (here: polyvinyl alcohol, which is a copoly-mer since it is produced via incomplete hydrolysis of polyvinyl acetate) and for the determi-nation of phase diagrams (here: toluene/ethanol/polydimethylsiloxane). The most important observation in the field of copolymer analysis consists in the possibility to obtain information on the widths of the chemical distribution. Adequate turbidimetric titrations reveal pro-nounced differences between samples that should according to their standard characterization with respect to average chain length and average chemical composition be identical. The cen-tral message regarding phase diagrams is that the evaluation of transmission curves with re-spect to macroscopic demixing is greatly simplified by the fact that the phase separation of a given system takes place within a small band of transmission values, independent of the com-position of the mixture.

Macromolecular Chemistry and Physics 2002, 4, 203, 705-711.

preprint number: 221