Organization Behavior of Guaiacyl and Guaiacyl/Syringyl Dehydrogenation Polymers (Lignin Model Compounds) at the Air/Water Interface

In plant cell walls, lignins are closely associated with hydrophilic polysaccharides. In these associations, the interface between the two polymers may have a strong influence on the molecular architecture of plant cell walls. To model such hydrophilic/hydrophobic and anisotropic media, two DHPs (dehydrogenation polymer models of lignins, one guaiacyl type (G) and one mixed guaiacyl/syringyl type (GS)) were spread at the air/water interface. The investigation of these two DHP layers at the air/water interface by neutron reflectivity has demonstrated that both DHPs form a nonhomogeneous structure with DHP distribution going from a concentrate structure at the air side to a dilute one at the water side. When the amount of spread polymer is increased, the GS DHP layer shows a regular increase of the DHP volume fraction whereas the GDHP forms steeper density profile structures, implying that molecular structural differences might be involved in these different behaviors.