【作者】 孟锦宏；

【导师】 段雪；

【作者基本信息】 北京化工大学 ， 应用化学， 2005， 博士

【摘要】 本文依据插层组装理论,以层状双氢氧化物(Layered double hydroxides,LDHs)为主体,以食品添加剂山梨酸(SA)和乳酸(LA)及除草剂草甘膦(GLY)三种有机活性物质为客体,采用共沉淀自组装技术,合成了SA插层LDHs、LA插层LDHs和GLY插层LDHs。对插层LDHs的超分子结构、热稳定性和结构-缓/控释性能的内在联系进行了系统而深入的研究,揭示出此类插层材料在缓/控释食品添加剂和农药及作为模板储库提高此类有机活性物质的热稳定性方面的潜在应用前景。 运用XRD、FT-IR、UV-Vis、BET、SEM、TEM、TG/DTA/MS、in situ HT-XRD、MAS NMR及XPS等表征方法,建立了三种有机活性物质插层LDHs的超分子结构,并给出了相应的结构模型。SA插层ZnAl-LDHs的层间客体以单层垂直的定位方式排列于主体层板间,其超分子结构中主-客体间以静电及氢键相互作用连接,客-客体间则以π-π相互作用连接。LA插层ZnAl-LDHs的层间客体以双层倾斜的定位方式排列于主体层板间,其超分子结构中客体以分子内氢键及分子间氢键两种形式以静电及氢键相互作用与主体层板连接。GLY插层ZnAl-LDHs的层间客体以单层交错垂直的定位方式排列于主体层板间,其超分子结构中主-客体及客-客体间均以静电和氢键相互作用连接。 三种有机活性物质插层LDHs的热分解均经历了层间水及吸附水的脱除、层板的分解、层间阴离子的分解烧燃和氧化物的形成四个步骤。同时,层间客体阴离子的分解及燃烧温度较单一客体的分解温度提高60～200℃。 基于超分子插层结构,三种有机活性物质插层LDHs较相应物理混合物对客体的释放行为有着明显的改变。前者的释放行为表现为初期释放速率较快,随后伴随一个持续的缓释过程。缓释机理研究表明,近中性及碱性溶液中,插层LDHs更多还原

【Abstract】 Using the concept of intercalation chemistry, with layered double hydroxides (LDHs) chosen as host material and organic active agents as guest species, food preservative sorbic acid (SA)-intercalated LDHs, food additive lactic acid (LA)-intercalated LDHs, and herbicide glyphosate (GLY)-intercalated LDHs have been successfully synthesized by using coprecipitation self-assembly techniques. The supramolecular structure, thermal behavior and relations between structure and release properties of these organic active agent-intercalated LDHs have been studied in detail. The results suggest potential applications of these intercalated materials in slow/controlled release of the organic active agents and as template reservoirs with enhanced thermal stability of organic active agents.Characterization using XRD, FT-IR, UV-Vis, BET, TEM, SEM, TG/DTA/MS, in situ HT-XRD, MAS NMR and XPS techniques confirm the supramolecular structures of the three organic active agent-intercalated LDHs, and corresponding structural models are presented. The interlayer anions of SA-intercalated ZnAl-LDHs are positioned in a vertical interdigitated monolayer mode based on a host-guest interaction involving both electrostatic attraction and hydrogen bonding and a guest-guest interaction involving intermolecular n-n functions of SA anions within the two-dimensional interlayer galleries. The interlayer anions of LA-intercalated ZnAI-LDHs are oriented in a tilted bilayer mode with two conformations involving intramolecular and intermolecular hydrogen bonding, respectively. The interlayer anions of GLY-intercalated ZnAl-LDHs are strongly stabilized with a verticalinterdigitated monolayer mode based on host-guest and guest-guest interactions involving both electrostatic attraction and hydrogen bonding.The thermal decomposition process of the three organic active agent-intercalated LDHs exhibits four steps involving the removal of physisorbed and cointercalated water, dehydroxyiation and collapse of the host layer, decomposition and combustion of interlayer guest anions, and the formation of oxide, respectively. Furthermore, the decomposition and combustion temperature of interlayer intercalated guest anions of the three organic active agent- intercalated LDHs is increased by 60~200°C compared with that of the pure organic active agents.As a consequence of the supramolecular intercalation structures, all three organic active agent-intercalates present obvious differences in release behavior compared to the corresponding physical mixtures with rapid release in the initial step, followed by a more sustained release of the remaining guest anions. The release mechanism in neutral and basic aqueous solution is an ion-exchange process between the interlayer guest anions and inorganic anions in the release media, and the diffusion process of guest anions in the interstices and interlayers of organic active agent-intercalates is the rate-limiting step. On the other hand, the guest release of organic active agent-intercalates in acidic aqueous solution is essentially controlled by the dissolution process of the host layers.The relationship between the structural parameters and the release behavior for the organic active agent-intercalated LDHs has been studied systemically. The interlayer conformation of GLY-intercalated LDHs strongly influences its release behavior. The release rate of GLY intercalates markedly decreases according to the sequence: interlayer guest conformation in the tilted monolayer mode > vertical monolayer mode > vertical interdigitated monolayer mode. This is due to the increase in host-guest and guest-guest interactions and interlayer guest packing density of GLY-intercalated LDHs. An increase in layer charge density of intercalates also causes a decrease of release rate for GLY-intercalated LDHs due to the increase in the host-guest and guest-guest interactions and the interlayer guest packing density.更多还原