Basic Study on Novel Molecule-Based Magnetic Polymers and Homogeneous Magnetic Fluids

高居里温度(T_C)的分子基磁性聚合物的设计、合成和表征。我们将合成一系列具有四氰基或稳定的电子受体基团的单体(如魔芋基团或硫胺基)，每个单体都将与含有二茂铁和双二茂铁的具有柔性侧链的单体反应，得到基于分子的磁性聚合物。这类聚合物将通过大分子链上二茂铁或双二茂铁单元的强电子给体与四氰基或稳定自由基的强电子受体之间的共价键形成分子内交换作用。分子间的超交换耦合是由于二茂铁(或双二茂铁)单元和四氰基单元(或稳定自由基)的极化而发生的，而大分子链的纠缠将促进一维自旋耦合扩展到三维耦合。合成的聚合物的磁性将使用磁强计进行表征。用X射线衍射法确认合成的聚合物不含氧化铁等杂质，用电子自旋共振光谱确认合成的聚合物中存在自旋相互作用。由于所使用的含二茂铁或双二茂铁的单体上存在长而柔韧的侧链，这类分子基磁性聚合物有望溶于常见的溶剂。这样的前景会吗？打开大门？与目前工业上使用的传统磁流变液完全不同的是，磁流变液是将非常重的磁性粒子(氧化铁或铁氧体)悬浮在轻载液中，容易出现严重的沉淀和团聚问题。PI将研究由本研究合成的聚合物制备的新一代均相磁流变液的基本流变性。尽管有报道称具有低居里温度(TC)(远低于室温)的小分子有机磁体，但在过去的三十年里，许多研究小组试图开发具有高TC(远高于室温)的真正基于分子的磁性聚合物。如果这项研究取得成功，将在聚合物合成、电子结构化学和材料化学方面开辟新的前沿，并激励理论家为大分子的磁性发展新的理论，因为目前可用的磁性理论涉及小分子有机磁体。基于高T_c分子的磁性聚合物可能会表现出许多理想的性能，包括溶解性、加工性和合成延展性，并可能有实际应用。该项目可以为如何设计具有高T_c的分子基磁性材料提供新的见解。它还可以从根本上促进稳定自由基的配位化学。BROADER IMPACT这项研究可能会对多个科学工程学科产生广泛影响，包括聚合物化学、有机金属/配位化学、凝聚态物理和流变学，以开发均相磁流变液的新理论。该研究项目的成功完成可能会为合成目前尚不存在的具有高T_c的新型分子基磁性聚合物带来新的方法(S)，并可能对新一代新型磁性聚合物的制造工艺以及广泛使用磁流变液的汽车工业产生影响。这项研究将是高度跨学科的；研究生将接触到新型聚合物的设计和合成及其表征方面的广泛研究经验，这将为他们未来的职业生涯提供广度和灵活性。

CBET-0755763, HanThis research focuses on the design, synthesis, and characterization of molecule-based magnetic polymers having high Curie temperature (Tc). A series of monomers having tetracyano units or stable radicals (e.g., verdazyl radical or thioaminyl radical) for electron acceptor will be synthesized and each of the monomers will be reacted with a ferrocene- and biferrocene-containing monomer with long flexible side chains to obtain molecule-based magnetic polymers. Such polymers will form intramolecular exchange interactions through covalent bonding between the strong electron donor of ferrocene or biferrocene units along the macromolecular chains with the strong electron acceptor of tetracyano unit or stable radical. The intermolecular super exchange coupling will occur due to the polarization of both ferrocene (or biferrocene) units and tetracyano units (or stable radicals), and the entanglement of macromolecular chains will facilitate the expansion of one-dimensional spin coupling into a three-dimensional one. The magnetic properties of the polymers synthesized will be characterized using a magnetometer. X-ray diffraction will be employed to confirm that the polymers synthesized do not contain any impurities such as iron oxide, and electron spin resonance spectrometry will be employed to confirm the presence of spin interactions in the polymers synthesized. Owing to the presence of long flexible side chains on the ferrocene- or biferrocene-containing monomers used, such molecule-based magnetic polymers are expected to be soluble in common solvents. Such a prospect will ?open the door? to the development of a new generation of homogeneous magnetorheological (MR) fluids, quite different from the conventional MR fluids in current industrial use that are suspensions of very heavy magnetic particles (iron oxide or ferrite) in a light carrier liquid which are subject to serious problems of sedimentation and aggregation. The PI will investigate the fundamentals of the rheological behavior of a new generation of homogeneous MR fluids that will be prepared from the polymers synthesized in this research.INTELLECTUAL MERITAlthough small-molecule organic magnets having low Curie temperature (Tc) (much lower than room temperature) have been reported, during the past three decades many research groups have tried to develop truly molecule-based magnetic polymers having high Tc (much higher than room temperature). This research, if successful, will pave new frontiers in polymer synthesis, electronic structure chemistry, and materials chemistry, as well as stimulate theorists to develop new theory for magnetisms of macromolecules, since the currently available theories of magnetism deal with small-molecule organic magnets. High Tc molecule-based magnetic polymers may exhibit numerous desirable properties, including solubility, processability, and synthetic tenability, and could have practical applications. This project could provide new insights into how to design molecule-based magnetic materials having high Tc. It could also fundamentally advance the coordination chemistry of stable free radicals.BROADER IMPACTSThe research could have a broad impact on several scientific engineering disciplines including polymer chemistry, organometallic/coordination chemistry, condensed matter physics, and rheology for the development of a new theory for homogeneous MR fluids. Successful completion of the research project could lead to new method(s) for the synthesis of novel molecule-based magnetic polymers having high Tc, which do not exist at present, and can have an impact on manufacturing processes for a new generation of novel magnetic polymers and also the automotive industry that makes extensive use of magnetorheological fluids. The research will be highly interdisciplinary; graduate students will be exposed to a wide range of research experiences in the design and synthesis of novel polymers and their characterization, which will provide breadth and flexibility for their future careers.