Electric Moments of Polar Polymers in Relation to Their Structure

摘要

From the observed angular dissymmetry of the light scattered by polymer solutions it has been possible to draw conclusions on the average size of the polymer coil. In general, the actual coil diameter found in this way is much larger than that calculated from a model with free rotation. (For polystyrene in benzene the factor is about 3.5.) This increase in size can satisfactorily be attributed to hindering of rotation around the chemical bonds. In order to obtain information about structural details of this hindered rotation, however, the size determination will have to be combined with evidence derived from other sources than light scattering. As such, the dipole moment, as derived from measurements of the dielectric constant of polymer solutions, obviously is a good choice. If a number of units are connected to each other in a chain, the contribution of the whole chain may be larger or smaller than would be the case if the units were free, depending on whether positions of parallelism or antiparallelism of the elementary electric moments are preponderant, taking the average over all the possible forms the coiling molecule can assume. A theory of this effect has been worked out, and experiments have been carried out. One of the examples is polyparachlorostyrene, for which the average contribution to the polarization of one chain element is substantially smaller in the polymer than that of the corresponding monomer.