Structure of Oriented Sodium Metaphosphate Glass Fibers

Abstract

The structure of oriented sodium metaphosphate glass fibers has been investigated employing cylindrical distribution functions obtained from the x‐ray scattering pattern. Although this method has rarely been used, it is the only sound one available. The difficulties in interpreting the functions were eased somewhat by the use of difference, rather than complete, cylindrical distribution functions. The former are usually less cluttered with spurious peaks than are the latter. The results indicate that the NaPO₃ fibers are made up of long chains of PO₄ tetrahedra, and that the axes of these chains have a strong preference for lying along the fiber axis direction. Both the general appearance of the distribution functions and the results of normal distribution function calculations agree with the existence of a very high degree of orientation in the fibers. The locations of sharp peaks on the functions suggest that the individual PO₄ tetrahedra have shapes similar to that found in crystalline RbPO₃. In the latter material the average in‐chain P–O distance is 1.62 Å and the average out‐of‐chain distance is 1.46 Å. Best agreement with the experimental distribution functions is obtained with a puckered version of a planar chain, in which each tetrahedron is tilted relative to the chain axis through two mutually perpendicular angles of 20° to 30° and the intratetrahedral angles are near 110°. The high effective radial resolution obtained in the difference cylindrical distribution functions, as a result of the angular resolution, suggests that the simplified cylindrical distribution function will be a useful way to study the structures of orientated amorphous polymer fibers.