SYNTHESIS AND POLYMERIZATION OF LIGNIN-BASED MACROMONOMERS .3. RADICAL COPOLYMERIZATION OF LIGNIN-BASED MACROMONOMERS WITH METHYL-METHACRYLATE

The radical copolymerization of methyl methacrylate (MMA) with lignin fragments (resulting from flash hydrolysis) functionalized by polymerizable groups is investigated. To transform lignin fragments into macromonomers, the anchoring of styrenyl and methacryloyl groups has been first studied; the optimal conditions for an etherification or an esterification of hydroxy functions in lignin residues, by chloromethylstyrene and methacryloyl chloride leading to lignin-macromonomers of controlled size and functionality, have been investigated. The influence of experimental conditions on both the degree of substitution and the characteristics of functionalized lignin fragments is discussed; linear and cross-linked lignin-MMA copolymers have been prepared. The accurate control of the number of anchored polymerizable groups per lignin fragment is a determining step that establishes the dimensionality of the chains and therefore the processability of the prepared copolymers. ''Linear'' lignin-MMA copolymers containing up to 40% in mass of lignin have been obtained and some structural aspects of the corresponding materials are examined.