Design and Function of Lignin-Based Recyclable Composites
Design and Function of Lignin-Based Recyclable Composites
复制标题
木质素基可回收复合材料的设计和功能
DOI：
10.2472/jsms.52.3appendix_108
复制
发表时间：
2003
期刊：
影响因子：
--
通讯作者：
M. Funaoka
中科院分区：
文献类型：
--
作者：
Y. Nagamatsu;M. Funaoka
通过酚类化合物与浓酸组成的相分离体系，酚类化合物选择性地杂化到天然木质素苯丙烷单元的C1位，定量地得到1，1-双（芳基）丙烷型线型聚合物（木质酚）。木素酚具有酚活性高、相变明显等独特性质。此外，木质酚的功能是能够控制使用的分子内开关功能：在碱性条件下，木质酚中的C1-酚亲核攻击相邻的C2作为开关设备，随后由芳基醚键的裂解。在具有类似开关功能和结构特征的木质素-对-甲酚和木质素-2，4-二甲基苯酚中，木质素-对-甲酚在甲酚核上被高度羟甲基化（HM）以得到网络生活预聚物。另一方面，主要在末端单元上具有反应性位点的木质素-2，4-二甲基苯酚得到线性活性预聚物。聚合木质酚的结构由HM-木质素-对甲酚和HM-木质素-2，4-二甲基苯酚的混合比例或木质酚中对甲酚和2，4-二甲基苯酚的杂化比例控制，然后进行羟甲基化。所得的聚合物链在开关点处裂解，通过开关功能得到低分子量亚基。将纤维素与高锰酸钾-木质素酚（HM-ligno-p-cresol：HM-ligno-2，4-dimethylphenol）按1：0，1：1，0：1的比例复配，制备了可回收复合材料。这种复合材料表面光滑，看起来像木头。复合材料的尺寸稳定性随着HM-木质素-对甲酚与HM-木质素-2，4-二甲基苯酚混合比例的增加而显著提高。利用木质素酚的开关功能，将复合材料重新分离为低分子量的木质素酚和纤维素。
Through the phase-separation system composed of phenols and concentrated acid, the phenol components are selectively hybridized into C1-positions of phenylpropane units of native lignin to give 1, 1-bis(aryl)propane-type linear polymers (lignophenols) quantitatively. Lignophenols have unique properties such as high phenolic activity and obvious phase transition. Furthermore, the functionality of lignophenols was able to be controlled using the intramolecular switching function: Under alkaline condition, C1-phenols in lignophenols nucleophilically attack adjacent C2 as switching devices, followed by the cleavage of aryl ether linkages. In ligno-p-cresol and ligno-2, 4-dimethylphenol with similar switching functionality and structural characteristics, ligno-p-cresol was highly hydroxymethylated (HM) on the cresolic nucleus to give network-living pre-polymer. On the other hand, ligno-2, 4-dimethylphenol having reactive sites mainly on the terminal unit gave linear-living pre-polymers. The structures of polymerized lignophenols were controlled by mixing ratio of HM-ligno-p-cresol and HM-ligno-2, 4-dimethylphenol or by the hybridization ratio of p-cresol and 2, 4-dimethylphenol in lignophenols followed by hydoxymethylation. The resulting polymer chains were cleaved at the switching points to give low molecular weight subunits by the switching function. Recyclable composites were prepared by the combination of cellulose and HM-lignophenol (the mixing ratio of HM-ligno-p-cresol to HM-ligno-2, 4-dimethylphenol was 1:0, 1:1, 0:1, respectively). The composites had glossy surfaces and looked like wood. The dimensional stability of composites was improved significantly with increasing mixing ratio of HM-ligno-p-cresol to HM-ligno-2, 4-dimethylphenol. Using the switching functionality of lignophenol, the composites were re-separated into lignophenols with low molecular weight and cellulose.