Lignin, Copolymerization

Common chemistries include tannins and lignins but also more modem polyacrylates and derivatives, which often act as carriers for specific functional groups and provide novel chemistry molecules. The polyacrylates may also be copolymerized, perhaps with maleates [maleic anhydride, cis-butenedioic anhydride (OCOCHrCHCO) is the usual starting point material], styrene (vinylbenzene, phenylethylene,... 

This study examines the synthesis of acrylated lignin derivatives using IEM, and the copolymerization characteristics of these derivatives with methylmethacrylate (MMA) and styrene (S). 

Acrylated lignin derivatives were copolymerized with MMA and S in dry methylene chloride with benzoyl peroxide and N,N-dimethyl anyline as catalyst. Reaction mixtures were poured onto Teflon molds, the solvent was evaporated at room temperature in the fume hood, and films were cured in an oven at 105°C for 6 hrs. Experimental details and results are given elsewhere (15). 

Acrylated lignin derivatives were copolymerized with vinyl monomers to yield network materials (gels) with gel fraction declining as vinyl equivalent weight increased. 

Straforelli (2) investigated the effect of lignin on the graft copolymerization of methyl methacrylate initiated by azo-... 

Given the fact that lignin is easily oxidized by most conventional oxidants which are in turn often used to initiate copolymerization, one expects that its presence will retard, if not inhibit, the reaction as the initiator will be used up preferentially in the reaction with lignin. Moreover, the reaction of lignin with oxidants gives rise to the formation of quinonoid structures which have pronounced retarding and/or inhibiting properties (5). 

The same authors (5) showed also in another work that the presence of larger amounts of lignin in bisulfite pulps may have a favourable effect on grafting polyacrylonitrile using the cellulose xanthate-hydrogen peroxide redox system to initiate the copolymerization reaction. The plots of the total conversion as well as of polymer loading show a minimum centered around approximately 15% of lignin. 

In conclusion, even though there is the definite correlation between carboxylic group index and minimum in respect to graftability in our system, a detailed work with model compounds would be required to futher elucidate the mechanism of lignin participation in the copolymerization reaction. 

Liu J, Yuan W, Lo T (1999) Copolymerization of lignin with cresol catalyzed by peroxidase in reversed micellar systems. EJB Elect J Biotechnol 2 82-87... 

Popp JL, Kirk TK, Dordick JS (1991) Incorporation of p-cresol into lignins via peroxidase-catalysed copolymerization in nonaqueous media. Enzyme Microb Technol 13 964—968... 

Liu J, Yang F, Xian M et al (2001) Molecular weight and distribution of the copolymer of lignin/phenol in the copolymerization catalyzed by peroxidase. Macromol Chem Phys 202 840-848... 

Yoshida T, Xia Z, Takeda K et al (2005) Peroxidase-catalyzed polymerization and copolymerization of lignin-based macromonomer (lignocresol) having high content of p-cresol and thermal properties of the resulting polymers. Polym Adv Technol 16 783-788... 

XS = sulfonation, M = methylolation, MO = miscellaneous oxidation, G = grafting, P = phenolation, CM = carboxymethylation, MAC = maleic anhydride copolymerization, MCR = miscellaneous carboxyla-tion reactions, E = epichlorohydrin (also in conjunction with pheno-lated lignin), A = alkoxylation (i.e., ethylene, propylene, and butylene oxides), M+EP = modification with compounds containing unsaturated end groups ( divalent hydrocarbons ) followed by epoxidation with peroxide, MA = methacrylic acid. 

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