title: Positron lifetime reveals the nano level packing in complex polysaccharide-rich hydrolysate matrixes.
abstract: Positron annihilation lifetime spectroscopy (PALS) was used to quantify the free volume and molecular packing in hydrolysate and hemicellulose-based barriers films, derived from process streams during wood processing operations. These hydrolysate films, comprising a fair share of lignin coexisting with poly- and oligo-saccharides, have very low but variable oxygen permeability but differ among themselves with respect to barrier performance as well as molecular weight, degree of branching, and monosaccharide residue main chain composition. From PALS measurements on hydrolysates, the free volume hole radius (r(h)), radius distributions (n(r(h))), volume-weighted hole sizes (<v(h)>(v)), and hole volume distributions (g(v(h))) were calculated showing that the hydrolysate matrixes are very densely packed with small holes. The results show a clear relationship between hydrolysate molecular architecture and composition, the nanolevel molecular packing, and the ability of suppressing the diffusion of oxygen through the film.
authors.affiliation: Fiber and Polymer Technology, Royal Institute of Technology (KTH), Stockholm, Sweden.
authors.forename: Ulrica
authors.initials: U
authors.lastname: Edlund
authors.forename: Yang
authors.initials: Y
authors.lastname: Yu
authors.forename: Yingzhi Zhu
authors.initials: YZ
authors.lastname: Ryberg
authors.forename: Reinhard
authors.initials: R
authors.lastname: Krause-Rehberg
authors.forename: Ann-Christine
authors.initials: AC
authors.lastname: Albertsson