Modification of Kraft Lignin to Expose Diazobenzene Groups: Toward pH- and Light-Responsive Biobased Polymers

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• 作者：Antoine Duval ; Heiko Lange ; Martin Lawoko ; Claudia Crestini
• 刊名：Biomacromolecules
• 出版年：2015
• 出版时间：September 14, 2015
• 年：2015
• 卷：16
• 期：9
• 页码：2979-2989
• 全文大小：695K
• ISSN：1526-4602

文摘

A pH- and light-responsive polymer has been synthesized from softwood kraft lignin by a two-step strategy that aimed to incorporate diazobenzene groups. Initially, styrene oxide was reacted with the phenolic hydroxyl groups in lignin, to offer the attachment of benzene rings, thus creating unhindered reactive sites for further modifications. The use of advanced spectroscopic techniques (¹H and ³¹P NMR, UV and FTIR) demonstrated that the reaction was quantitative and selective toward the phenolic hydroxyl groups. In a second step, the newly incorporated benzene rings were reacted with a diazonium cation to form the target diazobenzene motif, whose formation was again thoroughly verified. As anticipated, the diazobenzene-containing kraft lignin derivatives showed a pH-dependent color change in solution and light-responsive properties resulting from the cis鈥?i>trans photoisomerization of the diazobenzene group.