【作者】 刘晓磊；

【导师】 段雪；

【作者基本信息】 北京化工大学 ， 应用化学， 2008， 博士

【摘要】 本论文依据插层组装理论,以层状双氢氧化物(Layered doublehydroxides,LDHs)为主体,羧甲基β-环糊精(CMCD)为客体,分别采用离子交换法和原位生长法制备了环糊精插层水滑石(CMCD-LDH)的粉体和薄膜。系统而深入地研究了CMCD-LDH粉体及薄膜材料对外消旋苯基乙二醇(PED)的手性拆分性能,及其包合十二烷基苯(DDB)的性能。揭示了CMCD-LDH材料的手性拆分机理以及LDH层板和CMCD的双重限域效应对包合客体分子光学性质的影响,并探讨了此类插层材料在手性拆分、吸附中性客体分子、光学增效等领域的潜在应用前景。利用LDHs层间阴离子的可交换性将CMCD插入LDH层间,制备了CMCD-LDH粉体。采用XRD、FT-IR、ICP、TG-DTA等手段对该插层产物进行了表征,得到其超分子结构模型。发现CMCD采取轴线垂直层板的单层定位方式排列于主体层板间,主-客体间存在静电及氢键相互作用。采用手性高效液相色谱等手段研究了CMCD-LDH对外消旋PED的手性吸附性能。研究发现层间的CMCD空腔和LDH外表面分别对外消旋PED产生选择性和非选择性吸附,并分别采用Langmuir-Freundlich和Freundlich等温线模型描述了这两种吸附过程。针对CMCD-LDH对PED的吸附过程,对平行扩散模型进行了修正,修正后的模型很好地描述了全部吸附过程。采用本实验室提出的原位生长技术制备了LDH层板垂直于基底排列的CMCD-LDH膜,并采用XRD、FT-IR和SEM对膜的结构、组成和表面形貌进行了表征。研究发现该薄膜材料对外消旋PED具有手性选择性吸附的能力,LDH薄膜材料的层间CMCD空腔和外表面分别发生选择性和非选择性吸附。分别采用Langmuir-Freundlich和Freundlich等温线模型描述了这两种吸附过程。针对CMCD-LDH膜对PED的吸附,发现膜扩散模型很好地拟合了该过程,进一步计算得到不同温度下的表观扩散系数。对比CMCD-LDH粉体和薄膜的手性吸附特性,发现薄膜材料不仅具有更高的手性选择吸附,而且具有易分离、易回收、流失少等优点。因此,CMCD-LDH薄膜材料在拆分宏量手性醇领域具有潜在的应用价值。研究发现在组装得到的CMCD-LDH材料中,CMCD纳米级空腔的上下开口被LDH层板所遮蔽形成了封闭的纳米笼。该笼可通过LDH的溶胀/干燥过程实现可控开关。选取DDB作为客体分子,研究了该纳米笼对中性分子的包合性质。分别提出了“先插层后包合”和“先包合后插层”的方法,并制备了CMCD-LDH包合DDB的粉体;提出以溶剂蒸发法制备CMCD-LDH包合DDB的薄膜,并用XRD、FT-IR、ICP、TG-MS、SEM等手段对包合产物的结构、组成、热分解行为及表面形貌进行了研究。进一步的研究证实LDH层板和层间CMCD的空腔对DDB光学性质存在双重限域效应。与未插层CMCD空腔的限域效应相比,发现CMCD-LDH的双重限域效应能够更加明显地限制客体分子的运动,从而导致DDB的荧光光谱发生蓝移,荧光寿命增长。综上所述,本论文系统研究了CMCD-LDH对外消旋体的手性拆分以及包合中性分子的性能。揭示了CMCD-LDH材料的手性拆分机理以及手性吸附规律;还研究了CMCD-LDH的包合过程以及LDH层板和CMCD的双重限域效应对包合客体分子光学性质的影响。本工作对于揭示复杂超分子体系中主客体的相互作用具有一定的理论意义,并为实现此类插层结构LDH材料用于外消旋体的手性拆分和中性分子的吸附、存储、光学增效等领域提供了实验依据。更多还原

【Abstract】 Based on the conception of intercalation chemistry,with layered double hydroxides(LDHs) chosen as host material and carboxymethyl-β-cyclodextrinas(CMCD) as guest species,CMCD intercalated LDHs powder and film materials have been successfully synthesized by the use of ion-exchange and in situ crystallization techniques,respectively.The chiral adsorption of 1-phenyl-1,2-ethanediol (PED) by CMCD-LDH has been studied in detail.The enantioselective adsorption mechanism for the CMCD-LDH has been systematically investigated.We also investigate the inclusion of dodecylbenzene(DDB) by CMCD-LDH as well as the double-confinement effect on the included guest.The CMCD-LDH powder sample was obtained by the method of ion exchange.Characterization using XRD,FT-IR,ICP and TG-DTA techniques confirm the supramolecular structure of CMCD-LDH,and the corresponding structural model are presented.CMCD molecule is accommodated as monolayer arrangement with its cavity axis perpendicular to the LDH host layer and carboxymethyl groups on the narrow side of the cyclodextrin cavity attaching to the LDH surface.Both electrostatic attraction and hydrogen bonding are involved in the host-guest interactions.Moreover,the enantioselective adsorption of racemic PED by CMCD-LDH has been investigated by chiral HPLC.The adsorption isotherms of enantioselective as well as non-enantioselective adsorption of PED by CMCD-LDH have been investigated,and it was found that the Langmuir-Frendlich and Frendlich model can be respectively used to describe the two different adsorptions satisfactorily. Furthermore,the intraparticle diffusion model is successfully validated in this work.The film of carboxymethyl-β-cyclodextrin-intercalated Zn-Al layered double hydroxide(CMCD-LDH) has been prepared by in situ crystallization on a porous anodic alumina/aluminum(PAO/Al) substrate. The structure of the CMCD-LDH film was investigated by XRD,FT-IR, SEM and EDX.CMCD adopt a monolayer arrangement with its cavity axis perpendicular to the LDH layer and the ab-face of LDH microcrystals is predominantly perpendicular with respect to the substrate. This film can be used to enantioselectively separate racemic PED.The adsorption isotherms of enantioselective as well as non-enantioselective adsorption of PED by CMCD-LDH film have been investigated,and it was found that the Langmuir-Frendlich and Frendlich model can be respectively used to describe the two different adsorptions satisfactorily. Furthermore,the plane sheet diffusion model is successfully validated in this work.As the structured CMCD-LDH film is conveniently used and exhibits high enantioselective adsorption ratio compared with the powder material,it can be expected that this film could be feasibly applied in the field of industrial chiral adsorption and separation.A novel nanocage derived from CMCD-LDH has been demonstrated in this work,whose gates can be controlled by the process of swelling/drying the CMCD-LDH.Dodecylbenzene(DDB) as the guest molecule has been incorporated into the nanocage,through two different routes:the intercalation-inclusion method andthe inclusion-intercalation method.For the convenience of using this nanocage as absorbent and storage vessel for neutral guest,films of the resulting composite materials (CMCD-LDH) were fabricated by the method of solvent evaporation on glass substrates.The structure,chemical composition,morphology and physicochemical properties of the materials were characterized by XRD, TG-MS,elemental analysis,SEM,fluorescence spectroscopy and time-resolved fluorescence decay measurements.Moreover,the combined confinement effect of both the LDHs layers and cyclodextrin cavity on the optical properties of encaged guest has been investigated. Compared with the confinement effect produced from cyclodextrin only, this double-confinement imposes stronger confinements on the mobilities of the guest molecule,which causes the blue shift in fluorescence spectrum and prolongs the decay time of the guest.Consequently,the elucidation of the enantioselective adsorption mechanism as well as the illustration of the inclusion process and the host-guest interaction of CMCD-LDH,affords a convincing and useful theoretical foundation for the application of CMCD-LDH as chiral adsorbents,synergistic agents and storage vessels.更多还原