Axial orientation of poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) films is achieved by stretching in a narrow temperature range (220-230 degrees C) close to the polymer glass-transition temperature (T-g). Stretching at high draw ratios of PPO films exhibiting the nanoporous-crystalline (NC) alpha and beta forms leads to the formation of a new crystalline form (thereafter named gamma), which reaches a very high degree of axial orientation (up to 0.98). This transition from alpha and beta forms toward the. form occurs with a partial loss of crystallinity, as pointed out by DSC and FTIR measurements. Wide-angle X-ray diffraction (WAXD) patterns of the. form show only two intense and broad peaks: an equatorial peak, suggesting the presence of short-range pseudohexagonal packing of conformationally disordered parallel PPO chains, and a layer line peak, indicating a coarse chain axis periodicity of c = 1.62 +/- 0.02 nm. FTIR and polarized FTIR spectra clearly show vibrational peaks associated with the new gamma crystalline phase. Density measurements and sorption tests of low-molecular-mass guest molecules suggest that the gamma form, differently from the starting NC alpha and beta forms, does not exhibit crystalline cavities. This hypothesis is confirmed by the absence of dichroism of infrared peaks of benzene molecules absorbed by gamma form films, which indicates that guest sorption occurs only in the amorphous phase.