Toward thermoplastic lignin polymers. Part 1. / Hasan Sadeghifar in Industrial & engineering chemistry research, Vol. 51 N° 51 (Décembre 2012)  

Public ISBD [article]  inIndustrial & engineering chemistry research > Vol. 51 N° 51 (Décembre 2012) . - pp. 16713–16720 Titre : Toward thermoplastic lignin polymers. Part 1. : Selective masking of phenolic hydroxyl groups in kraft lignins via methylation and oxypropylation chemistries Type de document : texte imprimé Auteurs : Hasan Sadeghifar, Auteur ; Chengzhong Cui, Auteur ; Dimitris S. Argyropoulos, Auteur Année de publication : 2012 Article en page(s) : pp. 16713–16720 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Thermoplastic Hydroxyl Résumé : This work offers a comprehensive understanding of the conditions required for the selective masking of the phenolic hydroxyl groups in technical kraft lignins, which is pivotal in determining their subsequent chemical and thermal reactivity. To this effect, we have examined the chemistry and developed the conditions for the facile, mild, and selective masking of the phenolic hydroxyl groups in softwood and hardwood kraft lignins. We have compared two series of methylated softwood kraft lignins synthesized using different methylation chemistries. Our data show that (when used as specified) dimethyl sulfate in aqueous NaOH selectively converts the phenolic hydroxyl groups of kraft lignin to its methylated derivatives without apparent side reactions. In contrast, methyl iodide (in the presence of excess K2CO3 in N,N-dimethylformamide) was found to be rather ineffective and unselective. Various milder methylation conditions were also examined for both softwood and hardwood kraft lignins using dimethyl sulfate, and the details of this work are documented. In addition, a series of oxypropylation reactions were also carried out using propylene oxide in aqueous NaOH. Propylene oxide was shown to selectively add (at room temperature, 0.5 M NaOH, 18 h) less than two units on average per phenolic hydroxyl group without significant additional polymerization or other side reactions. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie301848j [article] Toward thermoplastic lignin polymers. Part 1. : Selective masking of phenolic hydroxyl groups in kraft lignins via methylation and oxypropylation chemistries [texte imprimé] / Hasan Sadeghifar, Auteur ; Chengzhong Cui, Auteur ; Dimitris S. Argyropoulos, Auteur . - 2012 . - pp. 16713–16720. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 51 (Décembre 2012) . - pp. 16713–16720 Mots-clés : Thermoplastic Hydroxyl Résumé : This work offers a comprehensive understanding of the conditions required for the selective masking of the phenolic hydroxyl groups in technical kraft lignins, which is pivotal in determining their subsequent chemical and thermal reactivity. To this effect, we have examined the chemistry and developed the conditions for the facile, mild, and selective masking of the phenolic hydroxyl groups in softwood and hardwood kraft lignins. We have compared two series of methylated softwood kraft lignins synthesized using different methylation chemistries. Our data show that (when used as specified) dimethyl sulfate in aqueous NaOH selectively converts the phenolic hydroxyl groups of kraft lignin to its methylated derivatives without apparent side reactions. In contrast, methyl iodide (in the presence of excess K2CO3 in N,N-dimethylformamide) was found to be rather ineffective and unselective. Various milder methylation conditions were also examined for both softwood and hardwood kraft lignins using dimethyl sulfate, and the details of this work are documented. In addition, a series of oxypropylation reactions were also carried out using propylene oxide in aqueous NaOH. Propylene oxide was shown to selectively add (at room temperature, 0.5 M NaOH, 18 h) less than two units on average per phenolic hydroxyl group without significant additional polymerization or other side reactions. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie301848j

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