Mutual diffusion in blends of long and short entangled polymer chains

Infrared microdensitometry was used to study the mutual diffusion across an originally sharp interface between two saturated polybutadienes of degrees of polymerization N sub A and N sub B ( > N sub e , the entanglement length) for three different ratios N sub A /N sub B . The extent of diffusion broadening suggests that the mutual diffusion coefficient is controlled by the mobility of the faster moving (shorter) polymer chains, indicating that convective flow may be important in such mixing phenomena. 30 ref.--AA