Multiphase materials with lignin: 5. Effect of lignin structure on hydroxypropyl cellulose blend morphology

Abstract

The incremental elimination of hydroxy functionality in an organosolv lignin by ethylation or acetylation dramatically influenced the state of miscibility and resulting morphology of blends prepared with hydroxypropyl cellulose (HPC). A maximum level of interaction between the blend components, as determined from melting point depression, occurred where 23–40% of the hydroxy groups were substituted. Above this level of modification, the interaction parameter decreased rapidly. Complete incompatibility occurred at a 90% degree of substitution with acetoxy functionality. Essentially three distinct phase morphologies could be detected in these materials. At the lowest levels of interaction, the morphology resulted from lignin domain formation and hydroxypropyl cellulose liquid crystal mesophase separation. A completely miscible, amorphous blend resulted when the polymer-polymer interaction was maximized. At intermediate levels, however, these materials were characterized by a dispersion of liquid crystal domains in an amorphous, lignin-reinforced HPC matrix.