广谱型木质素天然紫外防护剂的高效构建及其应用基础研究

Lignin is the most abundant renewable resource that contains conjugated aromatic structures in nature. It blocks irradiation from UVB rays (range of 290-320nm) and thus is a natural macromolecular UV-blocker. However, factors such as its poor absorbance in UVA wavelength range (320-400nm), which causes cumulative damages due to its small conjugated structures, its deep color, and poor compatibility have seriously hindered the applications of lignin in skincare products and as UV-blocking functional materials. In this project, broad-spectrum lignin-based UV-blockers are prepared by activating the structure of lignin and grafting benzophenone to improve its conjugation. Then amphipathic controllable and uniform lignin nano colloidal spheres are prepared by self-assembly. Formation of nano spheres not only lightens the deep color of lignin and improves its material compatibility, but it also enhances its UV-blocking performance. Detailed investigation of the effect of the molecular structure and microstructure of lignin on the grafting modification will be conducted. The regulating mechanisms of the self-assembly structures on the performance of modified lignin will also be analyzed. Additionally, the mechanisms of irregular lignin self-assembly into regular nano spheres will be elucidated. Based on these investigations, lignin-based macromolecular UV blockers that could block both UVA and UVB radiations will be prepared. This new material may effectively avoid the drawbacks of traditional UV blockers, such as poor photo-stability, penetrating into skin, and the damage that it can do to living cells. The implementation of this project will expand high-end applications for biomass lignin in areas such as skincare and UV-blocking functional composites.

木质素是自然界最大的含共轭芳香结构的可再生资源，具有一定抵御中波紫外（UVB）辐照能力，而成为天然高分子紫外防护剂。但是，木质素分子中共轭程度小导致其对具有累积伤害性的长波紫外（UVA）防护不足，同时存在颜色深、相容性差等问题,限制了其在防晒护肤、功能材料等领域的应用。本项目拟通过活化木质素分子结构，接枝二苯甲酮等增加共轭程度，赋予木质素优良的UVA防护功能，进一步耦合超分子自组装制备均一有序、表面亲疏水可控的木质素纳米微球，淡化木质素颜色，改善材料相容性，强化抗紫外性能。在此基础上，研究木质素分子与微结构对其接枝改性的影响规律，探索自组装结构和粒径对其性能的调控机制，阐明无规木质素形成有序纳米球的组装机理，构建同时抗UVA和UVB的广谱型高分子紫外防护剂，解决传统小分子紫外防护剂易光解及渗透而伤害皮肤的制约。本项目的实施可拓展生物质资源木质素在防晒护肤、抗紫外功能材料等高端领域的应用。

项目针对木质素分子共轭程度小、无规团聚导致其作为天然高分子紫外防护剂存在的对中波紫外线（UVB）吸收难以发挥，对长波紫外线（UVA）吸收不足等问题，通过活化木质素分子结构，亲核取代和接枝聚合改性，成功制备了广谱型木质素高分子紫外防护剂，并通过改变接枝长度、密度，实现了木质素紫外吸收范围和强度的精准调控；进一步，通过超分子自组装制备亲水性纳米微球、疏水性反相胶束，通过超声空化自组装制备木质素/紫外防护剂复合纳米微胶囊，淡化了木质素颜色，改善了材料相容性，强化了抗紫外性能；在此基础上，将制备广谱改性木质素紫外防护剂及其纳米颗粒进行配方设计，制备木质素基防晒护肤品、功能复合材料，拓展了其在日化、材料及柔性电子领域的应用。相关研究获得授权中国发明专利10项，美国专利1项，并实现转化1项；在国内外学术期刊上发表学术论文18篇；培养了国家自然科学基金优秀青年基金获得者1名、博士研究生2名、硕士研究生4名。项目相关研究作为“木质素的微结构调控及在微/纳米领域的应用”的主体内容之一，荣获2020年度广东省技术发明一等奖。