Effects of temperature and pressure on the stability and mobility of phases in rigid rod poly (p-phenylenes) -: art. no. 041802

The structure and the associated dynamics have been investigated in melts of hairy-rod macromolecules composed from a poly(p-phenylene) backbone with sulfonate ester and dodecyl side chains. For the structure investigation, polarizing optical microscopy, differential scanning calorimetry, pressure-volume-temperature, and wide-angle x-ray scattering have been employed whereas for the dynamics dielectric spectroscopy as a function of temperature and pressure was used. Based on the combined information from structure and dynamics the relaxation mechanisms were identified and the origin of the glass transition has been discussed in terms of insufficient thermal energy rather than insufficient free volume. The relevant phase diagram has been constructed and the stability and mobility of phases is discussed.