【作者】 程林；

【导师】 陈道勇；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2009， 博士

【摘要】 大分子自组装是软物质科学研究中的最重要领域之一,自组装指的是构筑基元借助于分子内或分子间的相互作用自发形成周期有序结构。这些弱相互作用主要有氢键、亲水-疏水作用、静电作用、主-客体包结作用以及π-π相互作用等,可用于组装的构筑基元包括无机分子、有机小分子、生物大分子、高分子以及粒子等。其中π-π相互作用是生命体中存在的一类重要相互作用,在一定程度上决定了生物大分子的结构与功能。有关π-π相互作用诱导有机小分子的组装在文献中多有报道,而鲜见于大分子组装。其次,以粒子的结构控制和作为组装基元的研究最近受到越来越多的关注,其高级组装体在光电材料、功能性纳米器件等研究中具有重要的潜在应用价值。近年来我们课题组建立了一种高效制备结构可控聚合物胶束的方法,还对杂化粒子、聚合物粒子等的高级组装进行了富有成效地研究。本论文在此基础上,将非共价键交联诱导胶束化方法和π-π相互作用等引入共聚物组装体系的研究中,制备了结构可控的聚合物粒子,并以聚合物初级粒子为构筑单元,对其高级自组装行为和规律进行了探索。论文主要分为以下几个方面:1,不对称聚合物粒子的制备新机制及其高级组装我们将非共价键交联法引入混合壳胶束的制备中,高效率制得具有疏松核结构的混合壳胶束。再利用混合壳胶束核的非共价键交联特点,通过核交联结构的解离、胶束内的核壳相互络合并与疏水嵌段的微相分离与聚集等协同作用,制备了双亲性不对称聚合物纳米粒子。1,2-丙二胺(PDA)是我们选用的非共价键交联剂,在共同溶剂DMF中,PDA可以高效率交联混合的嵌段聚合物P2VN-b-PAA和PEO-b-PAA的PAA嵌段,从而得到具有疏松核结构的且以P2VN和PEO嵌段为壳的混合壳胶束。通过调节胶束水溶液的PH值至3.1,PDA交联的PAA核发生解离,同时壳层的PEO嵌段与核内的PAA嵌段络合并与疏水的P2VN嵌段发生相分离,最终形成双亲性不对称聚合物粒子。制备的双亲性不对称粒子可以进行多维的高级自组装,形成以不对称粒子为构筑基元的聚合物纳米管以及半圆形的纳米片层结构。这一高级组装体的形成是不对称粒子自组装的新进展。2,单分子链不对称粒子的制备及其在共同溶剂中的组装行为运用化学交联诱导胶束化机制,高效率制备了双亲性的单分子链不对称聚合物粒子,并研究了它们在共同溶剂中独特的组装行为。我们用1,4-二溴丁烷作交联剂,对PS-b-P2VP-b-PEO的中间嵌段P2VP实施了有效地交联。并详细研究了浓度、温度、交联剂用量等参数对交联结果的影响。制备了理论上“最小”的聚合物粒子,研究了它们在共同溶剂中随浓度变化的独特的自组装行为。单分子链不对称粒子随着浓度增加,会逐渐聚集组装形成以PS为核,PEO为壳,交联的P2VP为中间层的超胶束(R_h=50～100 nm)结构。单分子链不对称粒子的高效制备为其可能的应用提供了必要的前提条件。3,π-π相互作用诱导的嵌段聚合物分级自组装我们将π-π相互作用引入到聚合物自组装体系中,利用π-π相互作用与氢键的协同效应,在嵌段聚合物(P2VN-b-PAA)的良溶剂中实现了其胶束化。在嵌段聚合物P2VN-b-PAA的DMF溶液中,加入小分子1-萘甲胺(NMA),首先发生的是氨基与羧基的氢键络合,络合后,NMA分子中的萘环与嵌段分子中的P2VN发生π-π相互作用,发生相互作用的络合部分形成了胶束的核,未相互作用的部分以壳层形式保持了胶束在溶剂中的稳定分散。经过适当热处理,我们进一步研究了以初级聚合物粒子作为基本构筑单元的自组装行为。在溶剂挥发过程中,各向同性的聚合物初级粒子可以在各类不同性质的基底上定向生长,形成了垂直阵列的柱状聚合物超级结构。研究并探索了该高级组装体作为荧光探针对酸、碱以及过渡金属离子等的化学响应。更多还原

【Abstract】 Molecular self-assembly is one of the most important research areas in the field of soft matter. Through self-assembly of various building blocks including inorganic and organic molecules, macromolecules, biomacromolecules, complex structures can be formed. The driving forces for self-assembly involve hydrogen bonding, hydrophobic and electrostatic interactions, the host-guest inclusions andπ-πstacking. Among them,π-πinteractions are especially important in the self-assembly of biomolecules to form specific structures with desirable functions in biological systems. Recently, assembly using nanoparticles as building blocks has drawn great attention, because "colloidal building blocks will be the "atoms" and "molecules" of tomorrow’s materials." For the self-assembly of nanoparticles, it is necessary to control their structure and properties, i.e. we have to endow nanoparticles with anisotropy or flexibility that makes anisotropic assembly of nanoparticles possible. This thesis mainly focuses on the structure and property-controlling as well as the self-assembly of nanoparticles. It includes three sections. Section 1: A novel approach to polymeric Janus nanoparticles and their self-assembly into tubular and sheet-like superstructure; Section 2: Preparation of unimolecular Janus micelles and their self-assembly in common solvent; Section 3: Vertically aligned nanofibers formed byπ-πinteraction induced self-assembly of nanoparticles and the application of the nano-array as a chemical sensor.Section 1: A novel approach to polymeric Janus nanoparticles and their self-assembly into tubular and sheet-like superstructure:Here, a novel mechanism for forming polymeric Janus particles from mixed-shell micelles (MSMs) and template-free self-assembly of the Janus particles into tubular superstructure and nanosheets was developed. By noncovalent crosslinking of poly (acrylic acid) (PAA) blocks in a mixture of PEO-b-PAA and P2VN-b-PAA using 1, 2-propanediamine (PDA) in DMF, micelles with mixed P2VN/PEO shells were prepared. After switching the solvent from DMF to neutral water, P2VN in the mixed shell collapsed into separated microdomains. In neutral water, P2VN microdomains were surrounded and protected by solvated PEO chains so that MSMs were individually dispersed. By decreasing the pH value of the aqueous solution to 3.1, intra-micellar complexation occurred between PEO and PAA, resulting in an asymmetric intramicellar phase separation between PEO/PAA complex and P2VN. As a result, amphiphilic Janus nanoparticles with hydrophobic P2VN at one side and hydrophilic PEO/PAA complex at the opposite side were formed. These Janus nanoparticles were able to self-assemble in water to produce tubular and sheet-like superstructures. These novel superstructures from amphiphilic Janus nanoparticle self-assembly are promising candidates for future nanodevices and sensors.Section 2: Prepration of unimolecular Janus micelles and their self-assembly in common solvent:The "smallest" (i.e., unimolecular) polymeric Janus nanoparticles were prepared with a high efficiency by intramolecular crosslinking the middle P2VP block of a PS-b-P2VP-b-PEO(SVEO) triblock copolymer in a common solvent DMF using 1, 4-dibromobutane (DBB) as the cross-linker . The intramolecular cross-linking could occur because of the steric shielding of PS and PEO end blocks. After intramolecular crosslinking, DMF changed from a good to a slightly poor solvent. As a result, concentration dependent self-assembly in DMF was observed. When the concentration gradually increased, the unimolecular polymeric Janus nanoparticles started to aggregate into supermicelles (R_h = 50-100 nm), where PS formed the supercore and PEO formed the corona with crosslinked P2VP nanoparticles in between. The amphiphilic nature of these unimolecular Janus nanoparticles will enable us to study programmable and hierarchical self-assembly of asymmetrically modified polymeric nanoparticles in various solvents.Section 3: Vertically aligned nanofibers formed byπ-πinteraction induced self-assembly of nanoparticles and the application of the nano-array as a chemical sensor:In this section, we demonstrated that primary polymeric nanoparticles could self-assemble anisotropically into vertically aligned nanofibers. The primary polymeric nanoparticles formed when a diblock copolymer poly (2-vinyl naphthalene)-block-poly (acrylic acid) (P2VN-b-PAA) was mixed with 1-aminomethyl naphthalene (1-NMA) in DMF. Upon the mixing, hydrogen bonding formed between amino groups of 1-NMA and carboxyl groups of the PAA block. Then, subsequentπ-πinteraction between naphthalene groups of the 1-NMA hydrogen bound to the PAA block and these of the P2VN block led to the complexation between P2VN block and PAA/1-NMA block, resulting in the primary nanoparticles. Theπ-πinteraction stabilized the structure of the primary nanoparticles, while the un-interacted units of the block copolymer led to their dispersibility. These primary spherical nanoparticles, annealed at 70℃, could self-assemble on various substrates into vertical aligned nanofibers during solvent evaporation. Theπ-πinteraction between the primary nanoparticles and re-distribution of naphthalene groups during the self-assembly are responsible for the anisotropic growth of the nanoparticles along the direction vertical to the substrates. It was also confirmed that the nano-array could be used as chemosensor responsible to protons and some metallic cations.更多还原