title: Morphology of dry lignins and size and shape of dissolved kraft lignin particles by X-ray scattering.
abstract: Lignin is a highly branched polymer consisting of phenylpropane units, and it is one of the ingredients of the supporting matrix in plant cell walls. The morphology of several lignins extracted from plant cell walls using different methods was studied by small-angle and ultra-small-angle X-ray scattering. A power-law type intensity was observed for the dry lignins, but on the basis of the power-law exponent the fractal approach often applied to lignins is not fully justified. However, the intensity of kraft lignin did show a power law with surface fractal dimension D(s) = 2.7 +/- 0.1. The specific surface area of the lignins ranged from about 0.5 to 60 m(2)/g with 20% relative accuracy. The radius of gyration was determined from small-angle X-ray scattering data for aqueous solutions of kraft lignin. The shape of the particles in NaCl and NaOH solutions was found to be elongated. The particles were about 1-3 nm thick, while the length (5-9 nm) depended on the solvent and on the lignin concentration. The size of these primary particles was approximately the same as the size of the pores in the fractal aggregates of the dry kraft lignin. Their size was determined to be about 3.5 nm.
authors.affiliation: Division of X-ray Physics, Department of Physical Sciences, P.O. Box 64, FI-00014 University of Helsinki, Helsinki, Finland. ulla.vainio@helsinki.fi
authors.forename: Ulla
authors.initials: U
authors.lastname: Vainio
authors.forename: Natalia
authors.initials: N
authors.lastname: Maximova
authors.forename: Bo
authors.initials: B
authors.lastname: Hortling
authors.forename: Janne
authors.initials: J
authors.lastname: Laine
authors.forename: Per
authors.initials: P
authors.lastname: Stenius
authors.forename: Liisa Kaarina
authors.initials: LK
authors.lastname: Simola
authors.forename: Janis
authors.initials: J
authors.lastname: Gravitis
authors.forename: Ritva
authors.initials: R
authors.lastname: Serimaa
mesh_terms: D024202:Electrophoretic Mobility Shift Assay; D008031:Lignin / Q000737:chemistry*; D008970:Molecular Weight; D010316:Particle Size; D012542:Scattering, Radiation
chemical_list: D008031:Lignin