MULTIPHASE MATERIALS WITH LIGNIN .10. A NOVEL GRAFT COPOLYMER WITH HYDROXYALKYL LIGNIN

A hydroxyalkyl lignin derivative was grafted in varying amounts onto the backbone of a methyl methacrylate/meta TMI(m-isopropenyl-alpha,alpha-dimethyl benzyl isocyanate) copolymer with NCO functionality ranging from 0 to 5.1 mol%, and the prepared graft copolymers were with 0 to 40% lignin derivative contents, and with weight average molecular weights between 45000 and 66000. The lignin was found to affect properties in a manner consistent with multiphase materials with considerable phase compatibility. In the case of graft copolymers, a single glass transition temperature (Tg) was detected, and this declined as the lignin content increased. The tan delta peak width doubled as the lignin content rose from 0 to 40%. On the other hand, polymer blend had two Tgs at the same temperature of the parent raw component. These results support the observation that lignin is a biopolymer with surprisingly wide-ranging phase compatibility if it has chemical bonds between the other constituents. This fact is consistent with lignin's role in nature that lignin-carbohydrate composite can be a compatibilizer between lignin and polysaccharides.