【作者】 诸致远；

【导师】 刘世勇；

【作者基本信息】 中国科学技术大学 ， 高分子化学与物理， 2009， 博士

【摘要】 超分子有序聚集体由于在催化化学、材料制备、生物医药等多方面存在着极为重要而广泛的应用价值,长期以来一直是科研领域研究的热点。我们结合近年来备受关注的可控自由基聚合和点击化学等手段合成具有特定功能化的嵌段聚合物;利用非共价键相互作用来构筑多种环境响应性的超分子有序聚集体,研究不同化学构造对于超分子自组装的影响;发展新的稳定超分子有序组装结构的方法,并对超分子聚集体的形成机理进行详细地研究。具体来说,本论文的工作包括以下几个方面:1.利用静电相互作用、包结络合作用、π-π共轭相互作用、氢键作用和阳离子-π相互作用等各种弱相互作用来构筑多种多重环境响应性的超分子组装体。首先利用原子转移自由基聚合（ATRP）的方法使用聚环氧乙烷双端大分子引发剂合成了一系列聚4-乙烯基吡啶-b-聚乙二醇-b-聚4-乙烯基吡啶（P4VP-b-PEO-b-P4VP）三嵌段聚合物。在酸性环境中当有二价有机阴离子萘二磺酸钠（NDSNa）存在时,该三嵌段聚合物可以在高浓度下形成温度敏感的水凝胶。接着合成了侧链被偶氮苯基团部分改性的聚N,N-二甲基氨乙基甲基丙烯酸酯（PDMA-co-PAzoC₆PMA）,并利用偶氮苯基团和环糊精之间的包结络合作用和低聚环糊精（oligo-（β-CD））在水溶液中混合构筑超分子水凝胶。该水凝胶具有多重环境响应性:由于偶氮苯基团的光致顺反异构特性使其具有可逆光敏感性;另外由于偶氮苯基团和环糊精之间的相对较低的包结络合作用常数,水凝胶同时又具有温度响应性和竞争络合响应性。然后我们使用单叠氮官能化的β-CD合成超支化的星形聚合物前体,该前体具有两个反应位点,利用Click方法将端炔基的聚N-异丙基丙烯酰胺（alkynyl-PNIPAM）接到该前体上形成PNIPAM的星形聚合物（oligo（CD-PNIPAM））,然后通过包结络合作用与端金刚烷官能化的聚N,N-二乙基氨乙基甲基丙烯酸酯（Ad-PDEA）作用形成全亲水性的杂臂星形聚合物,该杂臂星形聚合物拥有温度敏感的PNIPAM链和pH敏感的PDEA链,可以分别在高温低pH或低温高pH条件下的水溶液中分别形成以PNIPAM为核或以PDEA为核的球状胶束。接下来合成了主链上含有刚性偶氮苯重复单元的两亲性ABA三嵌段聚合物（PEG-b-BPADB-b-PEG）和多嵌段聚合物（m-PEG-b-BPADB）,在水溶液中自组装能形成树叶状的有序聚集体,而在紫外辐照下自组装只能形成短棒结构的聚集体。最后研究SDS和PTHC的混合体系,发现在高PTHC浓度下混合物能形成囊泡,并且该囊泡具有温度和稀释响应性,提高温度和稀释浓度均可以使囊泡结构向蠕虫状胶束转变。2.在超分子自组装的工作基础上,我们进一步致力于超分子纳米聚集体结构的固定。首先合成了分别被叠氮基团和炔基部分功能化的带相反电荷的正负离子聚电解质,聚环氧乙烷-b-聚（季铵化的二甲基氨乙基甲基丙烯酸酯-co-甲基丙烯酸叠氮丙酯）（PEO-b-P（QDMA-co-AzPMA））和聚环氧乙烷-b-聚（甲基丙烯酸-co-甲基丙烯酰炔丙胺）（PEO-b-（PMAA-co-PgAM））。在水溶液中,这两个嵌段聚合物混合,可以自发的形成聚离子复合物胶束,然后加入少量的一价铜作为催化剂可以在胶束核内通过点击化学核交联反应固定聚离子复合物胶束结构。随后研究了利用π-π共轭相互作用来稳定小分子表面活性剂的组装结构:极性头上都连接有苯环的十二烷基苯磺酸钠（SDBS）和对辛氧基苯胺盐酸盐（POAHC）在水溶液中混合能自发形成囊泡结构,利用苯环之间的π-π共轭相互作用可以将这种囊泡结构固定。3.对超分子有序组装体的形成过程也进行了详细的研究。使用停流技术首次研究了PGMA-PDMA-PDEA三嵌段聚合物的pH诱导胶束化动力学过程以及聚离子复合物的形成动力学过程。停流实验得到的动力学曲线能通过双指数动力学方程进行拟合得到两个特征弛豫时间,在快过程中（τ₁）,大量的高分子单链（unimer）快速形成小聚集体并且小聚集体之间相互融和形成准平衡态胶束或非平衡态聚离子复合物,在第一个过程结束的时候溶液中高分子单链的浓度接近于溶液的临界胶束化浓度（cmc）。紧接着是一个慢过程,这些准平衡态的聚集体逐渐调整形成最终平衡态的聚集结构。对于pH诱导的胶束化过程,第一个过程按照胶束的融合/裂分机理进行,第二个过程则对应着胶束的形成和解离过程,在这个过程中,胶束的聚集数增加,同时胶束的数均密度降低。对于第二个过程的限速步骤是第一个过程形成的部分准平衡态胶束的解离,而在这个过程中,同时并存着高分子链的插入/离开机理和胶束的融合/裂分机理这两种机理。在没有外加盐的存在下,胶束的形成和解离过程按照高分子链的插入/离开机理进行,随着溶液中盐浓度的增加,胶束的融合/裂分机理逐渐产生作用并最终在高盐浓度下占据着主导作用。对于聚离子复合物的形成动力学过程,其两个过程都完全按照二级动力学反应进行,弛豫过程遵从胶束的融合/裂分机理。而聚离子复合物的解离过程不光存在着胶束的融合/裂分,高分子单链的插入/离开在此时也起到了很重要的作用。4.在最后一章中我们利用聚合物胶束作为模板,实现了金纳米粒子在胶束内壳或者外壳上的致密有序堆积。首先合成了可断链的以二硫键连接的聚甲基丙烯酸甲酯-（s-s）-甲基丙烯酸三缩乙二醇单甲醚酯-（s-s）-聚甲基丙烯酸甲酯三嵌段聚合物(PMMA₃₆-（s-s）-PMEO₃MA₉₀-（s-s）-PMMA₃₆)。通过共溶剂过渡制成的胶束溶液中,二硫键位于疏水的PMMA内核和PMEO₃MA外壳的界面。四羟甲基氯化膦（THPC）稳定的水溶性小尺寸金纳米粒子,经过扩散作用进入到胶束的核壳界面,并通过硫-金化学键的生成在胶束内核表面形成一层致密金纳米壳层,二硫键断裂后生成的PMEO₃MA-SH仍然共价键接到金粒子表面形成该组装体的外壳。最终形成的组装体具有温度敏感性。其次利用含有吡啶二硫醚的ATRP引发剂引发合成了全亲水性AB嵌段聚合物PyDS-PMEO₂MA-b-PDEA,在酸性溶液中,嵌段聚合物和柠檬酸钠稳定的12nm左右金纳米粒子作用后包裹在金粒子表面,利用外层PDEA的pH敏感性,实现金纳米粒子的可控聚集。在碱性条件下将四羟甲基氯化膦稳定的金纳米粒子加入到嵌段聚合物胶束溶液中,金纳米粒子与壳层上的PyDS基团作用形成一层致密的金纳米外壳;调节溶液的pH值至酸性,该超分子组装体发生解离,而再将溶液pH值调至碱性时,金粒子可以再次组装形成球状聚集体。更多还原

【Abstract】 Supramolecular assemblies have attracted much interest in the past century due to their promising applications in diverse fields such as catalysis,material preparation and biomedicine.In this dissertation,a series of supramolecular assemblies were fabricated via different non-covalent interactions from specific functionalized surfactants and block copolymers with varying chemical architectures.The block copolymers were prepared in the combination of widely-noted controlled radical polymerizations and click chemistry.Besides the construction of the aggregates,new approaches in the fixation of nanostructures from supramolecular assemblies were investigated and the relaxation kinetics of the formation of the assemblies was also studied.The dissertation includes the following four parts:1.Supramolecular assemblies were built based on varies of non-covalent interactions such as electrostatic interaction,inclusion complexation,π-πinteractions, hydrogen bond and cation-πinteractions.First,ABA triblock copolymer, poly（4-vinyl-pyridine）-b-poly（ethylene oxide）-b-poly（4-vinylpyridine）（P4VP-b-PEO -b-P4VP） was prepared via Atom Transfer Radical Polymerization（ATRP）. In the presence of cross-linker,sodium 2,6-naphthalene disulfonate（NDSNa）, thermo-sensitive "flower-like" spherical micelles with a "UCST" behavior would form at low polymer concentrations while physical hydrogel can be obtained at high polymer concentrations in acid aqueous solutions.Second,azobenzene groups were introduced to the side chain of poly（2-（dimethylamino） ethyl methacrylate-co-azidopropyl methacrylate）,P（DMA-co-AzPMA）,by using the click chemistry technology.By mixing aqueous solutions of azobenzene polymer and oligo-β-cyclodextrin,multi-responsive physical hydrogel can form due to the inclusion complexation.The obtained hydrogel would translate to fluid solutions upon heating,UV-irradiation and adding competitive guest molecule.Third, narrow-dispersed PNIPAM-functionalized hyperbranched oligo（mono-N₃-CD）, oligo（CD-PNIPAM）,and adamantane-terminated PDEA were synthesized via a combination of ATRP and click chemistry.The inclusion complexation betweenβ-CD and Ad moieties was employed as the driving force in constructing supramolecular double hydrophilic miktoarm star copolymer,which consisting of PNIPAM chains as thermo-responsive arms and PDEA chains as pH-responsive arms.The supramolecular star copolymer showed "schizophrenic" micellization behavior in aqueous solution upon dually playing with solution pH and temperature.Forth,amphiphilic ABA triblock copolymers and multi-block copolymers consisting with a rigid azobenzene repeat unit in the main chain were successfully synthesized."Leaf-like" supramolecular aggregates were obtained in aqueous solutions while short "rod-like" aggregates were observed upon UV-irradiation.Last,spontaneous vesicles can form in the aqueous solution of anionic surfactant,sodium dodecyl sulfate（SDS）,when hydrotropic salt, p-toluidine hydrochloride（PTHC）,was added at certain concentrations.When these vesicles were heated above a critical temperature or diluted with certain water,they would transform into flexible wormlike micelles.2.On the basis of the works concerning the aggregation behavior of block copolymers mentioned above,we further devoted to the fixation the supramolecular assembly nanostructures.First,alkynyl group functionalized anionic polyelectrolyte,poly（ethylene oxide）-b-poly（methacrylic acid-co-propargyl methacrylamide）（PEO-b-P（MAA-co-PgAM））,and azide group functionalized cationic polyelectrolyte,poly（ethylene oxide）-b-poly（quaternized 2-（dimethylamino） ethyl methacrylate-co-azidopropyl methacrylate）(PEO₁₁₃-b-P（QDMA-co-AzPMA）) were synthesized.Polyion complex（PIC） micelles formed by mixing aqueous solution of the two oppositely charged polyelectrolytes. Upon adding Cu（Ⅰ） catalysis,the PIC micelles were facilely cross-linkd via "click" reaction which was processed in the PIC micellar core.Second,surfactant vesicles were observed to form in mixed aqueous solutions of sodium dodecyl benzenesulfonate（SDBS） and p-octyl aniline hydrochloride（POAHC）.Both the cationic and anionic surfactants possess a phenyl group connected to the polar head.Theπ-πinteraction between phenyl groups greatly enhanced the stability of the formed vesicles.3.In the third part,the kinetics processes of supramolecular assembly formation were detailedly investigated using stopped-flow technique.First,Poly（glycerol monomethacrylate）-b-poly（2-（dimethylamino）ethyl methacrylate）-b-poly（2-（di-ethylamino）ethyl methacrylate）（PGMA-PDMA-PDEA） triblock copolymer was synthesized via ATRP.The pH-induced micellization kinetics of the triblock copolymer was investigated by employing the stopped-flow light scattering and fluorescence.Upon pH-jump from 4 to 12,all relaxation curves recorded by stopped-flow light scattering can be well fitted with a double-exponential function, leading to a fast relaxation time constant（τ₁） and a slow relaxation time constant （τ₂）.The fast process（τ₁） is associated with the formation of quasi-equilibrium micelles,while the slow process（τ₂） is associated with micelle formation-breakup, approaching the final equilibrium state.Both processes occur much more slowly on initial addition of NaCl,and then level off at higher salt concentrations（＞0.5 M NaCl）.The concentration dependence ofτ₂ revealed that the mechanism of micelle formation/breakup process transforms from unimer insertion/expulsion in the absence of salt to micelle fusion/fission in the presence of high NaCl concentrations.Relaxation curves obtained with stopped-flow fluorescence using pyrene as a probe can be well-fitted with a single-exponential function,and the relaxation time(τ_py) was in agreement withτ_f,the relaxation time of the overall micellization process as detected by stopped-flow light scattering.Second, oppositely charged polyions,anionic block copolymer poly（ethylene oxide）-b-poly（sodium 4-styrene sulfonate）（PEO-b-PSSNa） and cationic block copolymer poly（ethylene oxide）-b-poly（quaternized 2-（dimethyl amino）ethyl methacrylate）（PEO-b-PQDMA） were prepared via ATRP.Upon directly mixing aqueous solutions of the two block copolymers,colloidally stabilized PIC micelles were obtained.The relaxation curves can be well fitted by a double-exponential function,leading to a fast relaxation process related to the initial quasi-equilibrium complex formation and a slow process related to the pre-complex structure rearrangements to the final equilibrium complexes.Both the two stages are determined to be acted as second-order reactions and processed through micelle fusion/fission mechanism.Fluorescence kinetics studies revealed that the neutralization of oppositely charged polyion was too fast to be detected and should be completed within the stopped-flow dead-time.Thermodynamics studies revealed that the spontaneously complexation is entropy driven.Upon increasing the ionic strength of the solutions,the complexation processes become slower by the reason of the decrease of entropy driven force.Last,the formation process of thermo-degradable micelles obtained by mixing acid aqueous solutions of PEO-b-P4VP diblock copolymer and 8-aminonaphthalene-1,3,6-trisulfonic acid disodium salt（ANTS） were studied both by directly mixing the two solutions and temperature jump from 50℃to 20℃.The relaxation process can be divided into two parts.In the first fast process,small complex micelles with low aggregates number formed via the electrostatic interaction and then transform to the quasi-equilibrium complexes.The quasi-complex structure rearrangements to the final equilibrium complex micelles accrued in the second slow stage.4.In the last section,the block copolymer micelles were employed as the template to assemble the gold nanoparticles.First,cleavable ABA triblock copolymer poly （methyl methacrylate）-（s-s）-poly（tri（ethylene glycol） methyl ether methacrylate）-（s-s）-poly（methyl methacrylate）（PMMA-（s-s）-PMEO₃MA-（s-s）-PMMA） was synthesized.In aqueous solutions,the block copolymer micelles were consisted with a PMMA core,PMEO₃MA outer shell and disulfide bonds in the core-shell interface.Tetrahydroxymethyl phosphate chloride（THPC） stabilized gold nanoparticles were added to the micellar solution.The gold nanoparticles were diffused into inner shell and then reacted with the disulfide bonds to form a compact gold nanoparticle inner shell.Second,pyridine disulfide ether end-functionalized AB diblock copolymer PyDS-PMEO₂MA-b-PDEA was synthesized,pH-jump from 4 to 10 lead to the formation of PDEA-core micelles with PyDS groups at the micellar outer shell.Compact gold nanoparticles outer shell was then obtained by adding the THPC-stabilized gold nanoparticles to the micellar solutions.The gold nanoparticle surface coated micelles can be dispersed in acid aqueous and the re-aggregate to spherical supramolecular assemblies at pH 10.更多还原