【作者】 王鑫；

【导师】 史林启；

【作者基本信息】 南开大学 ， 高分子化学与物理， 2012， 博士

【摘要】 金属卟啉作为催化剂和光敏剂等广泛运用于生物化学和光化学反应中。它同时也广泛存在于自然界的生命体中，对维持正常的生命活动起着非常重要的作用。对金属卟啉进行深入研究和探讨，对于人工开发太阳能、生命药物科学、分子电子学和催化仿生化学等领域和学科的发展具有非常重要的意义。通过水溶性金属卟啉和双亲水性的嵌段聚合物进行自组装，发挥协同效应将赋予嵌段聚合物自组装体以新的功能，同时增强或保持金属卟啉某些特殊性能。这一性质会在光催化、光动力疗法和光化学合成等方面具有潜在的应用前景。本论文将选用水溶性的金属5,10,15,20-四-(4-对磺酸基苯基)-卟啉（Metallo-TPPS）和双亲水性聚乙二醇-b-聚4-乙烯基吡啶（PEG-b-P4VP）或聚乙二醇-b-聚甲基丙烯酸二甲氨基乙酯（PEG-b-PDMAEMA）来构筑复合胶束。通过复合胶束的构建，增强金属卟啉的某些性能。在酸性水溶液中,多种金属卟啉容易水解而发生去金属化。并且在高浓度的情况下倾向于发生聚集，导致荧光自淬灭。由于这两个原因，金属卟啉作为光敏剂和光催化剂的运用受到了巨大的限制。因此研究人员希望找到一种有效的方法来增强金属卟啉稳定性同时防止其聚集。P4VP在pH<4.0的酸性水溶液中发生质子化，与ZnTPPS中带负电的磺酸基发生静电相互作用，形成PEG-b-P4VP与ZnTPPS复合胶束。这种胶束提供的微环境能够有效的减少水溶液中H+对ZnTPPS中Zn2+的取代。在胶束核中4VP/ZnTPPS比值（R）不同，对ZnTPPS的保护效果也不相同。在R值较低时，部分ZnTPPS随着时间的增加依然会发生水解；随着R值的增加，较高的聚合物浓度对ZnTPPS表现出了更好的保护性。同时聚合物胶束通过核内贯穿网络结构合理抑制ZnTPPS局部的高浓度，降低其聚集的发生，从而保护了其光学性能。众所周知，光敏剂通常在具有高光活性的同时，而往往伴随着低光稳定性。例如，金属卟啉在光照后容易发生电子转移，发生光降解。聚合物胶束可以通过核壳结构有效保护包裹在核内的物质免遭周围溶液中分子和离子的进攻和破坏。在酸性条件下，嵌段共聚物PEG-b-P4VP和ZnTPPS通过静电相互作用形成以P4VP/ZnTPPS复合物为核、以PEG嵌段为壳的胶束。然后再利用P4VP嵌段的pH响应性，调节溶液pH值到7.4，此时复合胶束核转变成致密斥水性核。亲水性的ZnTPPS由于中间的金属原子和P4VP嵌段吡啶上的氮原子发生轴向配位作用被包裹在斥水性的胶束核内。由于胶束核内斥水环境能够很强的阻碍经光照后还原的金属离子和氧化的卟啉配合物之间的分离，所以金属卟啉经光照后从配合体转移到中心金属的电子又会回到初始状态，这样提高了金属卟啉光稳定性。随着R（4VP/ZnTPPS）值的增加，复合胶束核变得更加致密和斥水，胶束对ZnTPPS和Co(III)TPPS光不稳定性的保护更加有效。选用另一种双亲水性嵌段共聚物PEG-b-PDMAEMA，利用PDMAEMA嵌段和ZnTPPS静电相互作用，来进一步研究其保护机理。最后利用ZnTPPS作为光催化剂通过DPP的脱溴反应，验证了在胶束核中金属卟啉的光活性。聚合物胶束在提高Metallo-TPPS光稳定性的同时依然使其具有很高的光催化活性。环状高分子的合成在高分子合成领域具有重要意义。我们提出了一种合理方法来合成尺寸较大的高分子大环。首先通过合成三嵌段聚合物ABA，聚甲基丙烯酸-2-月桂酰乙酯-b-聚丙烯酸叔丁酯-b-聚甲基丙烯酸-2-月桂酰乙酯（PCEMA-b-PtBA-b-PCEMA），然后把ABA溶解在良溶剂中，通过滴加PCEMA链段不良溶剂使三嵌段聚合物形成PCEMA为核，PtBA为壳的胶束。接着把胶束溶液以极缓慢的速度滴加入大量原配比的混合溶剂中。此时胶束浓度低于CMC，发生胶束解体。大量单链的高分子从胶束核中扩散出来，这时单分子链两端PCEMA嵌段由于选择性溶剂的存在容易发生首尾碰撞，此时进行紫外光照PCEMA链段发生双键光交联形成大分子环状聚合物。然后水解中间长链PtBA，水解成PAA接着修饰炔基之后和聚合度较小的高分子链PtBA-N3发生点击化学，形成环状的高分子梳性聚合物。通过NMR和GPC对合成PCEMA-b-PtBA-b-PCEMA环状梳型聚合物的每一步进行了表征。最终结果通过AFM观察到，没有得到预想中的大环状梳型高分子形态，出现了部分线性梳型高分子聚合物。这一结果是由于在制备ABA聚合物胶束的过程中，良溶剂和不良溶剂比例不恰当造成的。当稀释后，由于良溶剂量过多，导致PCEMA嵌段比较舒展的溶解在混合溶剂中，两端的PCEMA嵌段有效碰撞在一起的几率降低。通过调节滴定胶束中良溶剂和不良溶剂的配比，找到了合理的临界点。在不良溶剂占85%时，两端的PCEMA嵌段所成环数量最大，同时胶束没有解体的量保持在最小的范围内。更多还原

【Abstract】 Metalloporphyrins have received much attention because of their important roleas catalysts and sensitizers in a wide variety of biochemical and photochemicalreactions. For example, photocatalysis, photoredox systems, photochemical synthesis,solar cells and photodynamic therapy. However, ZnTPPS, MgTPPS, CdTPPS, etc, areapt to be demetallized in acidic solutions due to hydrolysis. Besides, ZnTPPS is apt toform aggregates at a high concentration, which leads to fluorescence self-quenchingeffect of the excited state. For these reasons, application of metalloporphyrins asphotosensitizers and photocatalysts is significantly limited. Therefore, it is desirableto enhance the stability of metalloporphyrins against demetallization and aggregation.It is well-known that self-assembled block copolymer micelles can encapsulatesubstances in their core, which can effectively protect the encapsulated substancesagainst invasion by molecules and ions in the solution. Here we report a novel andeffective method to enhance the stability of ZnTPPS in acidic aqueous solutions.Block copolymer PEG-b-P4VP and ZnTPPS form complex micelles in acidicsolutions through electrostatic interaction between positively charged pyridyls onpolymer and negatively charged sulfonte groups on ZnTPPS. The microenvironmentprovided by micelles effectively reduces the opportunities of H+replacing Zn2+, andthus prevents demetallization of the encapsulated ZnTPPS. Furthermore, fluorescencequenching is restrained to a certain extent due to segregation of ZnTPPS in themicelle core.Metallo-meso-5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrins (metallo-TPPS)have been widely used as photosensitizers. However, their vulnerability tophotodegradation significantly limits their applications. In this contribution, wedemonstrate a method to enhance the photostability of metallo-TPPS while retaintheir photoactivity by encapsulating them in the cores of complex micelles. Poly(ethylene glycol)-b-poly(4-vinylpyridine)(PEG-b-P4VP) and metallo-TPPS canform complex micelles in acidic solution through electrostatic interactions and thenundergo axial coordination with the pyridine moieties of PEG-b-P4VP when the pH isadjusted to7.4. Metallo-TPPS were entrapped in the hydrophobic and compactmicellar core, which effectively prevented photodegradation of the metallo-TPPS thatwould otherwise occur in aqueous solution due to attack by species such as oxygenmolecules. To further understand the mechanism of the improved photostability ofZnTPPS by their comicellization with PEG-b-P4VP in aqueous media, the stability ofmetallo-TPPS in the presence of other block polymers was tested. Complex micelleswere formed using PEG-b-PDMAEMA through electrostatic interactions betweenZnTPPS and DMAEMA under conditions identical to that of PEG-b-P4VP/ZnTPPSsystems. The resulting complex micelles provided some degree of protection, butwere less efficient than PEG-b-P4VP. In addition, the photodebromination of2,3-dibromo-3-phenylpropionate (DPP) sensitized with Zn(II)TPPS has been used as amodel reaction to study the photosensitive activity of ZnTPPS entrapped in complexmicelles. The entrapped ZnTPPS exhibit pronounced activity and have much higherefficiency and faster photosensitive reaction rates compared to free ZnTPPS, due toprotection of ZnTPPS by polymeric micelles and enrichment of DPP in the micellarcore.Poly(2-hydroxyethyl methacrylate)-b-poly(tert-butyl acrylate)-b-poly(2-hydroxyethyl methacrylate)(PHEMA-b-PtBA-b-PHEMA) was synthesized.The hydroxyethyl compounds in the PHEMA blocks were used to react with thecinnamoyl chloride, to magnify the chains. The macrocycles could be prepared by theassociation of PtBA blocks in a selective solvent for the PCEMA block, in which thePCEMA blocks collapsed together to decrease the interfacial energy. The polymerconcentration was kept below its CMC, which to prevent inter-chain coupling. Thenthe PCEMA block was photo-crosslinked to get macrocycles. Synthesis of cyclicmolecular brushes by click reactions between alkyne-modified PAA chains and azido terminated PtBA. The macrocycles and the linear chains of the crosslinked productscan be determined by comparing retention time of the peaks for GPC. Meanwhile, thepopulation of the macrocyclic brushes product would be determined from GPC andAFM images.更多还原