Drastically different morphological anisotropy was induced by linear photopolymerization in thin amorphous films of poly(vinyl 4-methoxy-cinnamate) (PVMC) and Langmuir-Blodgett films of 12-8(poly)diacetylene (PDA) deposited on glass substrates. Examination of these films by xray reflectivity reveals that the PVMC films became rough while PDA thin films became smooth along the direction of polarization of uv light. The elongated x-ray coherence area inherent to the reflectivity technique allowed quantitative determination of changes in the film morphology and structure.