功能性胆甾化合物的设计合成、分子组装及对环境的响应能力

【作者】 吴君臣；

【导师】 易涛； 黄春辉；

【作者基本信息】 复旦大学 ， 无机化学， 2009， 博士

【摘要】 大自然通过创造精美的复杂分子自组装形成超分子结构来维持生命的进行。因此,开发环境响应的超分子功能材料将显得特别重要。虽然有机小分子凝胶通过平衡分子间氢键作用、π-π相互作用、范德华力等可以形成有序的三维网络结构,从而使合适的有机溶剂凝胶化,但是设计刺激诱导的有机小分子凝胶作为一类新型的自组装材料仍然充满挑战。本论文设计合成了四类基于胆甾基团的有机小分子凝胶因子,在此基础上详细研究了外部刺激对凝胶的形貌结构、成胶机理、分子堆积结构的影响,全文包括以下四个部分:1.超声波诱导、热力学修复的可逆有机凝胶体系1)合成了一系列含胆甾和萘酰胺的凝胶因子、通过控制可形成氢键的个数及强弱来调控其成凝胶行为,发现含有两个氢键位点的凝胶可由超声波控制形成二维的表面结构;2)该凝胶可通过溶胶.凝胶的热力学过程转换变成三维空心球结构,这两种结构可多次可逆转换,且其表面疏水性也发生相应的变化;3)首次在凝胶体系中实现由超声波诱导、热力学修复的表面结构和疏水性变化,对声音对软材料及生物组织的影响提出了有价值的分子模型。2.超声波调控的不同空间尺度自组装凝胶体系1)设计合成了一类含有不同长度碳链胆甾和萘酰胺的凝胶因子;通过控制可形成氢键的空间环境和分子的溶解性来调控其成凝胶行为;2)随着碳链的增加,凝胶结构由三维空心球过渡到乳凸状纤维结构,凝胶机械强度开始下降,超声波的辐射对凝胶结构的影响开始减小。3)通过溶胶.凝胶的转变过程发现:在超声辐射和热力学修复状态下的凝胶,表面疏水性能发生相应的变化;同时,超声波在纳秒范围内产生热压,选择性地调节了分子间和分子内聚集的非共价键之间的相互作用。3.自发驱动的凝胶体系的研究1)设计合成了一种含有多个氢键的胆甾、方酸以及萘酰胺的C2对称的凝胶化合物。该化合物的方酸核能够与脂肪多胺作用形成凝胶,同时凝胶以动力学的方式自发地收缩并释放溶剂;2)通过溶胶.凝胶的转变过程发现:在热力学的条件下,这种收缩的凝胶能够恢复到最初状态并吸入所有溶剂。因此,这种凝胶可以充当溶剂泵把凝胶内的物质通过动力学作用运送到凝胶之外;3)通过时间依赖的XRD和CLSM的测试,我们发现凝胶从层状的囊泡逐渐转变成紧密堆集的六方结构。这种自发释放现象清楚地显示该凝胶体系对外界刺激有较好响应,因此在生物应用、药物缓释等方面都存在着广泛的应用前景。4.超声波触发上转换纳米晶(UCNPs)的自组装凝胶体系1)设计合成了一类含有不同肽链长度的胆甾酸和萘酰胺的凝胶化合物,在上转换纳米晶(UCNPs)存在下,通过分子间强的氢键相互作用及范德华力在超声波的触发下形成有机凝胶:2)上转换纳米晶(UCNPs)的加入增强了凝胶的机械强度,同时在980nm激光的激发下发出不同颜色的光,形成多彩色的荧光有机凝胶,由于分子间的相互作用而使这个两组分体系更加稳定;3)超声控制了含有油酸的上转换纳米晶(UCNPs)与凝胶化合物分子间的相互作用而形成的特殊行为的具有粘弹性的一类新型的功能化软材料,本研究为更好的理解这类软材料的自组装过程提供了实验依据。更多还原

【Abstract】 Nature does wonders by crafting complex molecular and supramolecular architectures, which are vital for sustaining life. It is increasingly important for the development of stimuli-responsive supramolecular functional materials by the means of self-assembling. Therefore, creating a stimulus-induced organogel is even more challenging because of the especial need to design a smart molecular that can be changed by external stimulus. Supramolecular organogel can organize into regular nano-architectures through specific non-covalent interactions including hydrogen bonds, hydrophobic interactions,π-πinteractions and Van der Waals forces. In this thesis, four series of naphthalic unit contained cholestoral gelators were designed and synthesized. The external stimulus （ultrasonic irradiation） morphology, mechanism of the gel formation and the packing fashion in the gel state were studied in details. The whole paper contains four parts as following:1. Ultrasound switch and thermal self-repair of morphology and surface wettability in a cholesterol-based self-assembly system.1) Designed and synthesized a novel family of asymmetric cholesterol-based fluorescent compounds 1a-1c with ALS （aromatic group A, linker L, steroidal group S）; 1c has the ability for gelating a wide variety of organic solvents, such as 1-butanol, Acetone, p-xylene.2) Both the self-assembly and surface wettability of the compound 1c with two H-bond sites can be controlled by ultrasound stimuli and restored by a thermal process.3) The ultrasound irradiation provides heat and pressure, and thus results in the spontaneous formation of the intermolecular H bonds and aggregation-induced helical motif.2. Tunable structural gel formation by both sonication and thermal processing in a cholesterol-based self-assembly system.1) Three asymmetric cholesterol-based fluorescent organogelators 2a, 2b and 2c with ALS （aromatic group A- linker L- steroidal group S） structural character were prepared, which have similar structure but different alkyl chain spacers between the naphthalimide and amide.2) The locations of hydrogen bonds （by different alkyl chain lengths） show a strong effect on the solubility and gelling properties of these compounds.3) Both the self-assembly and surface wettability of those compounds can be controlled by ultrasound stimuli and renovated by a thermodynamic process. These results provide a deeper understanding of the intermediate transition states in the gel under ultrasound irradiation.3. Gelation induced reversible syneresis via structural evolution.1) We reported here a tremendous volume changes in a cholesterol based low weight molecular gel system in the presence of multiamine. Meanwhile, the gelling solvents dissociated from the gel in a dynamic manner.2) This capability can be restored and recycled by gel-sol transformation. Thus, the gel may serve as a dynamic solvent pump that can be controlled by subtle changes in parameters, solvent composition or gel composition.3) A structural evolution from lamellar vesicles to a more compact hexagonal structure was observed accompanied by the solvent release. This report clearly shows how a practical actuator gel can react to external effects, and thus provides a strategy for the development of spontaneous-release soft materials and raises the possibility of stimulus-responsive organogels as new gel-based systems for applications such as drug delivery and other active ingredients.4. Self-assembly of peptide-based multi-color gel triggered by up-converting rare earth nano-particles.1) The self-assembly of dipeptide 1a and tripeptide 1b molecules are accelerated through physical interaction with UCNPs （NaYF₄） in polar solvent, which facilitates the self-assembly processes and leads to the formation of hydrid multi-color organogels.2) The dipeptide 1a and tripeptide 1b are locked by hydrogen bond and van der Waals forces to realize disperse of UCNPs in gel networks. The individually dispersed UCNPs are significantly aligned within the peptide gel, thereby reinforcing the peptide supramolecular tapes.3) UCNPs may also act as physical crosslinks between the tapes, thus enhancing gel stability. This new strategy to make UCNPs-peptide hybrid multi-color gels allows the UCNPs to retain their nanophosphor properties in the gel state.更多还原