Anisotropy of hole structures in oriented polycarbonate probed by two-dimensional angular correlation of annihilation radiation

Two-dimensional angular correlation of annihilation radiation (2D-ACAR) experiments have been performed on a uniaxially oriented polymer, bisphenol-A polycarbonate. The two-dimensional hole structures of unoriented and oriented polymers, determined from the momentum distributions, are found to be spherical and ellipsoidal, respectively. The average hole radii are determined to be 2.9 A in the unoriented sample and between 2.3 and 3.8 A in the oriented sample. Applications of the 2D-ACAR method to image the three-dimensional hole structures of polymeric materials are discussed.