The thermomechanical behavior of several rigid-rod polymeric fibers has been investigated. Up to 300 degreesC, all fibers exhibited the expected axial shrinkage on heating (CTE approximate to -6 x 10(-6) degreesC(-1)). However, a pronounced increase in thermal contraction was observed at temperatures where polymer degradation cr cleaving of the pendant group occurred. A degradation mechanism has been proposed that accounts for the evolved gases in PBZT and MePBZT. The accelerated shrinkage in these rigid-rod polymers is a result of decrease in the c-axis lattice parameter as measured via WAXD. The enhanced axial shrinkage and accompanying decrease in lattice parameter are attributed to chemical changes, and consequent cross-linking taking place within these systems which, in turn, serves to perturb the crystalline structure. The implications of this phenomenon of accelerated axial contraction, with, regards to morphology, are discussed.