PHOTOPHYSICAL APPROACHES TO CHARACTERIZATION OF GUEST SITES AND MEASUREMENT OF DIFFUSION RATES TO AND FROM THEM IN UNSTRETCHED AND STRETCHED LOW-DENSITY POLYETHYLENE FILMS

Various luminescence and photochemical techniques have been developed to probe the natures and accessibilities of the sites available to guest molecules in low-density polyethylene films. The methods, which include covalent modification of interior sites with fluorophores, are described. The results indicate that a distribution of site types, each with its characteristic shape, free-volume, and accessibility, is present. Furthermore, this distribution is changed drastically when a film is stretched. Activation energies for diffusion of a series of N,N-dialkylanilines in unstretched and stretched, modified and ''native'' films are reported, compared, and analyzed.