Smart surfaces of biobased materials: IV. Dynamic surface effects in films of F-containing cellulose esters

Smart surfaces of biobased materials: IV. Dynamic surface effects in films of F-containing cellulose esters Ulrike Becker and Wolfgang Glasser Biobased Materials/Recycling Center, and Department of Wood Science and Forest Products Virginia Tech, Blacksburg, VA Abstract: Dynamic surface phenomena were examined in films of fluorine (F)-containing cellulose derivatives. The derivatives were either statistical F-esters or F-terminated segments. Dynamic wetting force measurements indicated hysteresis behavior in all films. The hysteresis depended on kinetic (water sorption and reorganization) and thermodynamic (surface roughness and surface coverage with F-moieties) factors. Consecutive force loops revealed an increase in the wetting force with increasing loop number, indicating an increased hydrophobicity of the surface. The force increase was determined to be due to water sorption as well as surface reorganization. In increase in the size of the F-groups signified a decrease in reorganization rate due to a decreased mobility of the group. The process of reorganization was fully reversible, a behavior which is congruent with the definition of smart behavior.