具有空间异构结构的树枝状温敏高分子的制备及其高级结构与温敏性质关系的研究

The study on the influence of the advanced structures of thermoresponsive polymers on their thermoresponsive properties favors to the deep understand on their thermoresponsive mechanism. Moreover, it also helps to understand the relationship of advanced structure with properties of proteins. To date, the researches on thermoresponsive polymers mainly focus on the thermoresponsive properties tuned and explained through the difference of primary structures. Although there are some reports on the advanced structures of thermoresponsive polymers, lacks of comparison cannot embody the importance of advanced structures in the tuning of thermoresponsive property. Our primary study demonstrated that the different secondary structures of thermoresponsive hyperbranched polymers with different spatial isomeric structures in water had inmitate relationship with their obvious difference in thermoresponsive properties. Therefore, in this project we attempt to design and prepare a series of thermoresponsive dendritic polymers with isomeric structure. Then the relationship of their secondary structures with their thermoresponsive properties will be studied. The analyses on the secondary structure will be mainly through the multidimensional NMR techniques that can tell the difference of secondary structure resulted from the different interaction among hydrophobic groups of polymers.

研究温敏高分子高级结构对其温敏性质的影响有助于对温敏高分子温敏机理更深入的理解，也有助于理解蛋白质高级结构与性质的关系。目前，对于温敏高分子的研究，主要还是通过一级结构来调控和解释其温敏性质。对于温敏高分子高级结构的报导虽然有，但由于缺乏对比，无法体现高级结构在温敏性质调节方面的重要性。我们初步的研究发现具有同分异构结构的超支化温敏高分子在水溶液中不同的二级结构与它们显著的温敏性质差异有很大的关联。因此，本项目将主要设计并合成一系列具有同分异构结构的树枝状温敏高分子，以它们作为研究对象，侧重研究它们的二级结构与温敏性质的关系。其中对于二级结构的解析，我们主要通过多维核磁技术来分析大分子中非极性基团之间疏水相互作用不同而导致的二级结构的差异。

目前，对于温敏高分子的研究，主要是通过一级结构来调控和解释其温敏性质。对于温敏高分子高级结构的报导虽然有，但由于缺乏对比，无法体现高级结构在温敏性质调节方面的重要性。在本项目中，我们合成了两类同分异构温敏基元，一类是位置异构体，另一类是手性异构体。把这些同分异构温敏基元分别接枝到两种类球形聚合物骨架上，一种是树形大分子，另一种是超支化聚合物。研究了温敏基元的同分异构结构及其在高分子骨架上的分布对温敏性质的影响。发现对聚合物温敏性质影响的二级结构因素有两个，一个是超支化结构和树形结构本身对温敏有影响。树形结构中温敏基元仅仅分布在类球形结构的表面，而超支化结构中温敏基元不仅分布于类球形结构的表面，还分布于类球形结构的内部，从而更容易出现温敏，对温度敏感性更高；另一个二级结构因素是温敏基元本身的疏水基团位置异构化，温敏基元中疏水基元远离类球形核心使聚合物更容易出现温敏现象，对温度敏感性更高。此外，目前的研究表明，温敏基元的手性异构化对聚合物温敏影响不显著。蛋白质中普遍存在大量的疏水基元，通过了解这些疏水基元在类球状蛋白质中的分布，结合本项目的结论，有助于解释蛋白质在水中溶解的状态。