【作者】 廖小娟；

【导师】 江明；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2011， 博士

【摘要】 我们课题组在20世纪90年代研究了基于氢键相互作用的相容体系和络合体系。研究发现,随着氢键作用密度的增加,体系可实现“不相容—相容—络合”转变。随后,我们课题组提出并发展了氢键诱导的“非共价键接胶束”(NCCM)的概念,取得丰硕的成果。最近,我们又将超分子化学中的主—客体间的分子识别相互作用引入到大分子自组装的领域中,不仅拓展了NCCM的研究范围,更深化了我们对非共价键连接的理解。本论文的研究工作是在课题组已有的工作基础上开展起来的。主要是利用环糊精与客体分子的包结络合作用,在实现准聚轮烷(PPR)水凝胶的光可逆、粘土杂化水凝胶和不同链长的偶氮苯季铵盐诱导聚丙烯酸PAA的组装等方面展开研究。本论文分为以下几部分：1.基于竞争主客体相互作用的光敏准聚轮烷水凝胶的研究目前,对α-环糊精(α-CD)和聚乙二醇(PEG)形成的PPR水凝胶的研究很活跃,但是很少涉及其环境响应性的问题。我们提出了一个便捷的光响应性超分子策略来实现PPR水凝胶的解离以及再次形成。我们首先合成了一种含偶氮苯的水溶性光敏竞争客体分子：Azo-Cl-N+,进一步地,基于三种竞争主客体相互作用,我们成功地制备了光敏准聚轮烷水凝胶。我们的研究表明,这三种主客体相互作用的强弱顺序如下：trans-Azo-C1-N+/a-CD> PEG/a-CD> cis-Azo-C1-N+/α-CD。PEG10K和α-CD在水中可以形成PPR水凝胶。在该水凝胶中加入竞争的客体分子trans-Azo-C 1-N+,由于它是更强的客体分子,可以取代PEG,与α-CD形成包结络合物,从而使得水凝胶变成了溶液。对该溶液进行紫外光照射后,trans-Azo-C1-N+异构成cis-Azo-C1-N+,失去了与α-CD的络合能力,α-CD又重新回到PEG链上,使得PPR水凝胶再次生成。对该水凝胶进行可见光照射后,水凝胶又变成了溶液。如此光可控的凝胶—溶胶以及溶胶—凝胶转变可以循环往复。因此,在本论文中,我们不仅证明了广泛研究的PEG/a-CD PPR水凝胶具有超分子活性,而且实现了这一超分子材料的可逆转变。2.粘土上的准聚轮烷及其水凝胶的研究PPR水凝胶的力学性能很差,但是它具有剪切变稀的特性,可以应用于生物医药材料。而粘土在创造新的优异的聚合物水凝胶方面已显示出优越性。如果将纳米结构的粘土引入到PPR水凝胶中会是非常有价值的课题。因为可以期望粘土的引入不仅能降低PPR水凝胶的有机固含量,还可以提高其力学性能。然而,事实上,这是很难实现的,因为PEG链和粘土片层之间很强的相互作用将使得PEG被紧紧地吸附在粘土的表面,从而无法穿入环糊精的空腔。在本论文中,我们提出一个非常简便的方法,将粘土有效地引入到PPR水凝胶中。我们对PEG进行化学修饰,即在末端修饰上阳离子,这样PEG链便以类似于刷子的构象植入粘土的表面。这种刷子的构象使得α-CD能够串在PEG链上,从而形成杂化的准聚轮烷水凝胶。这种杂化水凝胶的弹性模量比没有修饰的PPR水凝胶高出一个数量级。另外,这种杂化水凝胶还具有超分子活性：基于上一章的竞争主客体相互作用,在紫外可见光照下,可以实现“凝胶—溶胶”转变。3.基于包结络合作用的以粘土为超级交联剂的杂化超分子凝胶我们合成了一种偶氮苯的季铵盐衍生物Azo-C4-N+,以及带有可聚合双键的环糊精单体GMA-CD,利用两者之间的包结络合作用得到组装体N+-(Azo-CD)-GMA,然后通过静电作用,与粘土片层上的Na+进行阳离子交换,得到负载了可聚合双键的粘土纳米片层的超级交联剂C-GMA,接着加入共单体PEG大分子单体,通过调节粘土的修饰率,采用自由基共聚合的方法,制备了粘土杂化的超分子水凝胶。4.不同链长的偶氮苯衍生物诱导聚丙烯酸的自组装我们合成了不同链长的偶氮苯季铵盐Azo-R-N+:Azo-C1-N+,Azo-C4-N+, Azo-C10-N+,并研究了偶氮苯季铵盐诱导的PAA的组装行为、偶氮苯季铵盐/α-CD诱导的PAA的组装行为及其pH响应和光响应。初步研究表明：(1)PAA/Azo-C4-N+可以组装成为棒状结构,而PAA/Azo-C1-N+和PAA/Azo-C10-N+可以组装成为球状结构；(2)PAA/Azo-C1-N+/α-CD可以组装成为囊泡,PAA/Azo-C4-N+/α-CD可以组装成为实心小球,PAA/Azo-C10-N+/α-CD可以组装成为长棒；(3)PAA/Azo-R-N+具有pH响应,随着pH的升高,PAA/Azo-C4-N+能够从棒状转变成球；(4)PAA/Azo-R-N+/α-CD具有pH响应,随着pH的升高,PAA/Azo-C4-N+/α-CD能够从聚集的小球转变成分散的球,最终球状结构遭到破坏；(5)PAA/Azo-R-N+/α-CD具有光响应,经过紫外光照后,PAA/Azo-C4-N+/α-CD由球变成棒,类似于PAA/Azo-C4-N+的聚集形态。更多还原

【Abstract】 Our research group studied the interpolymer complexation and miscibility enhancement by hydrogen bonding in the 1990s. It was found that immiscibility-miscibility-complexation transitions occur upon progressive increase in the density of hydrogen bonding. Later on, we proposed and developed a new concept of "Non-Covalent Connected Micelles" (NCCMs). Recently, we constructed a new kind of NCCMs using host-guest recognition, which is widely used in supramolecular chemistry, as the driving force for macromolecular self-assembly. Based on the previous research work in our group, the present thesis is mainly focusing on realizing photoresponsibility of pseudopolyrotaxane (PPR) hydrogel, preparation of hydrogel hybridized with clay, and self-assembly of poly(acrylic acid) (PAA) induced by azobenzene pyridinium with different alkyl chains, using inclusion complexation between cyclodextrin (CD) and guest molecules as the driving force. The content of this thesis is as follows:1. Photoreversible pseudopolyrotaxane hydrogels based on competitions of host-guest interactionsPhotoreversible pseudopolyrotaxane (PPR) hydrogels were simply achieved via competitions of three host-guest interactions. Our studies proved that the strength of the interactions is in the sequence of turans-Azo-C1-N+/α-CD> PEG/a-CD> cis-Azo-C1-N+/a-CD. PEG10K andα-CD form PPR hydrogel in water. The hydrogel can be transfered into sol by simply adding competitive guest trans-Azo-C1-N+, which replaces PEG units forming complexes with a-CD. After UV irradiation, PPR hydrogel regenerates because Azo-C1-N+ in cis form looses its ability to complex with a-CD and then the latter is threaded by PEG chain again. Following irradiation of the regenerated hydrogel by visible light converts it to sol again. The photocontrollable processes of gel-to-sol and sol-to-gel can be repeated cyclically. Thus the widely investigated PEG/a-CD PPR hydrogel is proved’active’in supramolecular chemistry, and the reversible nature of the supramolecular materials is fully materialized.2. Pseudopolyrotaxane(PPR) on clay nanoplatelets:demonstration and forming hydrogels wherefromClay is efficient in fabricating new polymeric hydrogels with outstanding properties. However, up to now, no reports on introducing clay nanostructures into supramolecular hydrogel, e.g. pseudopolyrotaxane (PPR) hydrogels, appeared. The PPR hydrogels, though usually are mechanically weak, are promising as biomedical materials because of their shear-thinning properties. Introducing clay nanostructures into PPR hydrogels are very attractive as it is reasonable to expect to improve the mechanical properties as well as to reduce the organic contents. However, in practice this target is difficult to reach, as PEG chains possess strong interactions with clay nano-platelets so may tightly adhere to the platelet surfaces, which makes the PEG chains threading into CD cavities impossible.Herein, we report a very simple way of modifying PEG chain by capping with a pyridinium group (PEG-N+), which can anchor to clay surface via electrostatic interaction and thus make the chains to form brushes. Such chains are then able to thread into CDs and thus form hybrid PPR hydrogel. These hydrogels with homogeneously dispersed clay nanoplatelets display dynamic modulus one order of magnitude higher than the native hydrogel of PEG and a-CD. Furthermore, the resultant PPR hydrogel can perform photo-switchable sol-gel transitions fully based on the above discussed competitive host-guest interaction.3. Hybrid supramolecular hydrogel using clay nanosheet as supra-cross-linkers via inclusion complexationA derivative of azobenzene Azo-C4-N+ andβ-cyclodextrin monomer GMA-CD was firstly synthesized and inclusion complex N+-(Azo-CD)-GMA formed between them. This inclusion complex was ion exchanged with Na+of clay to obtain double bond functionalized clay (C-GMA) as "supramolecular-cross-linker" (SCL). Adding a co-monomer and performing the polymerization will lead to the formation of hybrid supramolecular hydrogel.4. Self assembly of poly(acrylic acid) (PAA) induced by azobenzene pyridinium with different alkyl chainsAzobenzene pyridinium with different alkyl chains Azo-R-N+, named Azo-C1-N+, Azo-C4-N+ and Azo-C10-N+were synthesized. The self assembly of poly(acrylic acid) (PAA) induced by these azobenzene pyridinium and azobenzene/a-CD, and their pH sensitivity and light responsibility were studied. The results are as follows:(1) PAA/Azo-C4-N+ can self assemble into rods while PAA/Azo-C1-N+and PAA/Azo-C10-N+ self assemble into spheres;(2) PAA/Azo-Cl-N+/a-CD can self assemble into vesicles, while PAA/Azo-C4-N+/a-CD gives spheres and PAA/Azo-C 10-N+/a-CD gives rods;(3) PAA/Azo-R-N+ is pH sensitive. The morphology of PAA/Azo-C4-N+ can transfer from rods to spheres with increasing pH.(4) PAA/Azo-R-N+/a-CD is pH sensitive as well. The morphology of PAA/Azo-C4-N+/a-CD can transfer from aggregated spheres to separated spheres, and finally disappeared while the pH was increased.(5) PAA/Azo-R-N+/a-CD is light responsive. After UV irradiation, the morphology of PAA/Azo-C4-N+/a-CD can transfer from spheres to rods, similar to that of PAA/Azo-C4-N+更多还原