ABSTRACT
In recent years, there has been considerable interest in understanding the details of the molecular ordering in polyimides, methods of controlling the ordering, and the influence of the ordering on various properties of the polymer. Previous studies have demonstrated that the ordering is quite sensitive to process conditions. For example, even though imidization of the poly(amic acid) is generally completed by 250°C, the polymer is often “cured” at higher temperatures during which the polymer can undergo various forms of “volume relaxation” or “physical aging.” With higher temperatures, chain ordering can be enhanced [1–7], and the thermal, mechanical, and dielectric properties of the polymer can be affected [8]. The degree of ordering in polyimides can also be increased for thinner films [9–12] and films geometrically constrained by, for example, drawing or Langmuir-Blodgett techniques [13–17].
