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 polymeri zable groups is investigated. To transform lignin fragments into macro monomers, the anchoring of styrenyl and methacryloyl groups has been f irst studied; the optimal conditions for an etherification or an ester ification of hydroxy functions in lignin residues, by chloromethylstyr ene and methacryloyl chloride leading to lignin-macromonomers of contr olled size and functionality, have been investigated. The influence of experimental conditions on both the degree of substitution and the ch aracteristics of functionalized lignin fragments is discussed; linear and cross-linked lignin-MMA copolymers have been prepared. The accurat e control of the number of anchored polymerizable groups per lignin fr agment is a determining step that establishes the dimensionality of th e chains and therefore the processability of the prepared copolymers. ''Linear'' lignin-MMA copolymers containing up to 40% in mass of ligni n have been obtained and some structural aspects of the corresponding materials are examined.