水杨醛席夫碱聚合物荧光纳米微球的设计合成

Polymeric luminescent nanoparticles have attracted significant attention because of their potential such as fluorescent chemosensors and biosensors, fluorescent imaging agents, and metal-ion sensors. On the other hand, salicylidene Schiff base are known to have strong binding abilities to the metal ions and display different optical properties from the ligands themselves. Therefore this study is aimed at the design and syntheses of polymeric luminescent nanoparticles based on polymeric Schiff bases from vinyl salicylaldehyde. On the base of achievement of living/controlled polymerization of vinyl salicylialdehyde via RAFT technique, well-defined amphiphilic vinyl salicylialdehyde-based polymeric Schiff bases with different molecular architectures (block or comb) and chemical components (adjusted by the amine used for the formation of polymeric Schiff bases) will be prepared. The obtained polymeric Schiff bases can self-assemble into nanosized micelles in selective solvent (water or ethanol). The formed micelles are then used as nanoreactors to complex with metal ions (such as Zn ion) to give stable luminescent micelles with ionic cross-linking structure. Hollow luminescent capsules may also be obtained by using the block copolymers with a disulfide linkage between the hydrophobic and hydrophilic blocks. These polymeric luminescent nanoparticles are also expected to have photo responsive switch function on the base of the reversible metal-ligand coordination and de-coordination upon to light exposure. The properties including luminescence, photo-responsive and encapsulating ability of the resulting luminescent nanoparticles would be also investigated, providing sound scientific base for their applications such as in therapeutic and diagnostic medicine.

通过可控自由基聚合获得结构明确、分子量可控的聚乙烯基水杨醛，将其与亲水性胺基化合物如端氨基聚乙二醇或氨基功能化beta-环糊精进行醛-氨反应，生成两亲性聚合物水杨醛席夫碱，它们能在选择性溶剂如水中自组装，形成以水杨醛席夫碱配体为核、水溶性聚乙二醇或环糊精为壳的胶束，再以此为纳米反应器与金属离子如Zn2+配位，可以同时实现纳米微球的荧光功能化与交联稳定化，得到具有稳定纳米结构的（干燥后可在水或有机溶剂中再分散，并能保持其原来的纳米结构）荧光聚合物微球。上方法还可拓展应用于空心结构的荧光聚合物微球的制备。所得荧光聚合物微球（或空心球）可在UV光照射下使原本稳定化的交联结构解交联而去稳定化，这将有利于被其囊包着的客体分子的控制释放。通过形成席夫碱时所用胺基化合物的结构调节，还可方便地在发光聚合物微球的壳上引入合适的功能基，进一步拓展和提高所得荧光聚合物纳米微球的性能和应用价值。

由于在催化、生物医学、分析化学和材料科学等领域具有广泛的应用前景，水杨醛席夫碱引起人们极大的研究兴趣。迄今为止，国内外学者不断地开展该领域的研究工作，也取得不少令人注目的进展。但相关研究绝大多数集中在小分子体系，水杨醛席夫碱聚合物的研究还相当缺乏。与小分子相比，聚合物不仅可以保持其本身的性能特点，而且具有良好的成型加工性和机械稳定性，更具吸引力的是，聚合物还具有更强的自组装能力，方便构筑具有新颖结构和独特性能优势的纳米材料。本课题首次实现水杨醛功能化单体乙烯水杨醛的活性/可控聚合，获得结构及分子量可控的水杨醛聚合物。在此基础上，又设计合成了聚苯乙烯-b-聚乙烯基水杨醛嵌段共聚物。水杨醛聚合物直接与胺基环糊精反应，生成含环糊精的水杨醛席夫碱聚合物，与Zn2+ 离子配位后再包合金刚烷羧酸钠，可获得在水中发荧光的纳米微球，它能与蛋白质分子构建能量转移体系，有望应用于生物分子荧光检测。将聚苯乙烯-b-聚乙烯基水杨醛与二甘醇胺和胺基聚乙二醇反应，生成两亲性水杨醛席夫碱聚合物，在乙醇中自组装后，可形成核壳界面上带有水杨醛席夫碱配体的胶束，再Zn2+配位，一方面赋予胶束荧光性能，同时使胶束的核壳之间的中间层通过离子交联而稳定化，得到具有稳定纳米结构的荧光聚合物微球。由于胶束中间层的交联网络是由对光具有敏感性的水杨醛席夫碱锌配合物单元组成，可通过在紫外-可见光交替刺激作用下，实现荧光聚合物胶束的配位与解配位，可用于药物或催化剂分子的光可控释放。项目还设计合成了一种新型含水杨醛功能基的甲基丙烯酸酯类单体，以此为核单体进行聚合诱导自组装，得到不同形貌的纳米自组装体，进一步和肼反应得到具有聚集诱导发光特性、交联稳定的纳米材料。