DIELECTRIC PERMITTIVITY OF DIACETYLENE SINGLE-CRYSTALS IN THE CHAIN DIRECTION AND ITS DEPENDENCE ON THE POLYMER CONTENT DURING SOLID-STATE POLYMERIZATION IN EXPERIMENT AND THEORY

The increase of the electric permittivity in the chain direction, epsilon(r, parallel-to), during in situ solid-state polymerization of diacetylene crystals depends linearly on the polymer content within experimental error. This linearity is understood to be independent of the distribution of chain lengths due to a saturation effect of the linear polarizability in the chain direction. The increase of epsilon(r, parallel-to) by typically 1.8 from the monomer to the polymer value can be explained within a simple theory which takes into account a modified Genkin-Mednis approach for the monomer. Furthermore, the linearity is fulfilled for diacetylenes which show no structural phase transition during the polymerization process. By measuring epsilon(r, parallel-to) the conversion curve can be determined with a very low consumption of substance and time compared with the point-to-point gravimetrical analysis.