含双噻唑自组装膜的制备及磁性能研究

以2,2′-二氨基-4,4′-联噻唑(DABT)和苯酚为原料合成了新型的偶氮化合物2,2′-对苯酚偶氮基-4,4′-联噻唑(BTDP),将其与聚二甲基二烯丙基氯化铵(PDDA)在聚乙烯(PE)膜上进行层层自组装,并与过渡金属离子进行了配位.UV-Vis和FT-IR表征发现这种膜可以均匀的进行组装,且能较好的与金属离子配位.多功能材料物理特性测量系统(physical property measurement system,PPMS)测定配合物的磁性能,测试结果表明,与两者溶液直接混合后沉淀配合物的磁性相比,在PE膜上形成的自组装膜配合物的磁性能有较大幅度的提高.

Studies on preparation and magnetic properties of self-assembled multilayer films containing bithiazole rings

Organic magnetism is a rapidly developing field that combines the skills of experimental and theoretical scientists in many areas of chemistry and physics.Compared with inorganic ferromagnet,the organic ferromagnet exhibits the characteristics of structural diversities,low density,and readily processing.In addition,layer-by-layer (LBL) assembled multilayered films have received considerable interest because they allow fabrication of supramolecules with tailored architecture and properties.The design and preparation of organic soft ferromagnets by self-assembling is reported in this article.4,4′-(4,4′-Bithiazole-2,2′-diylbis(diazene-2,1-diyl))diphenol (BTDP) was first synthesized from phenol and 2,2′-diamino-4,4′-bithiazole (DABT),and the structure of BTDP was characterized by ~1H-NMR.The hydroxyls of the BTDP provide anions while the poly(diallydimethylammonium chloride) (PDDA) provides cations,so the layer-by-layer self-assembling of BTDP with PDDA was carried out based on the electrostatic interaction on the polyethylene (PE) surface with carboxylic acid groups (—COOH).BTDP coordinates with transition metal ions since two nitrogen atoms in the thiazole rings and metal ions can provide stable five-member rings.Therefore,the complexes of assembled multilayer films (PE-(PDDA/BTDP-M~ 2+ )_n) were also prepared via layer-by-layer assembly.The assembling process was monitored by UV-Vis spectroscopy.The linear increase of the absorbance at 413 nm with increasing the layer number indicates a process of uniform assembling.The structure of the complexes was characterized by FTIR,which suggests that the chelation has taken place demonstrated by the shift of the characteristic absorption band.In addition,the BTDP and PDDA deposition obtained by mixing their solutions could react with transition metal ions to form their metal complexes,which was also characterized by FTIR.The magnetic properties of these complexes were measured using a Physical Property Measurement System (PPMS-9),which included magnetization versus temperature,magnetization versus applied field,magnetic susceptibility versus temperature and magnetic hysteresis.The temperature is ranged from 4 to 300 K, and the intensity of magnetic field is in the range of -4×10~6～4×10~6 A/m.It was found that these complexes were organic soft magnets and had typical "S" shaped magnetic hysteresis loops.The saturation magnetization of the complex of assembled multilayer film PE-(PDDA/BTDP-Ni~ 2+ )_ 25 is 5.30 emu/g, and the paramagnetic Curie temperature is 128 K,while the remanence magnetization and coercivity are 0.0049 emu/g and 2228.17 A/m,respectively.The results show that PE-(PDDA/BTDP-Ni~ 2+ )_ 25 is an organic soft ferromagnet at low temperatures.The magnetic properties of the multilayer film for PE-(PDDA/BTDP-Cu~ 2+ )_ 25 is similar with those for PE-(PDDA/BTDP-Ni~ 2+ )_ 25 .The saturation magnetization of deposit complex PDDA/BTDP-Cu~ 2+ is 2.60 emu/g, and the paramagnetic Curie temperature is -10 K,while the remanence magnetization and coercivity are 0.0035 emu/g and 2307.75 A/m, respectively.The results show that PE-(PDDA/BTDP-Cu~ 2+ )_ 25 is an organic soft antiferromagnet at low temperatures.The magnetic properties of deposition for PDDA/BTDP-Cu~ 2+ are similar with those for PDDA/BTDP-Ni~ 2+ .In comparison,it was proved that the magnetic properties of multilayer self-assembled films were much better than those of deposited complexes.The strong ferromagnetism of the multilayered film may arise from the exchange interaction of the transition metal ions in the ligands which show a well-ordered 3-D network structure.