聚苯乙烯-b-聚丙烯酸/聚苯乙烯在水中的自组装及胶束尺寸的研究

利用动态光散射、透射电镜研究了嵌段共聚物聚苯乙烯 b 聚丙烯酸(PS b PAA)与均聚物聚苯乙烯(PS)在选择性溶剂水中的自组装行为.由于均聚物PS与PS嵌段具有相同的结构单元,均聚物PS参与胶束的形成,和嵌段共聚物的PS链段一同组成胶束的核;在适当的均聚物分子量和含量条件下,PS b PAA PS可以自组装形成单分散的纳米胶束;通过改变体系中均聚物PS的分子量和含量可在较大范围内调变胶束的尺寸.     

聚苯乙烯-丙烯酸嵌段共聚物在Ca~(2 )或乙二胺存在下的自组装行为

近 1 0年来 ,人们对于具有纳米尺度聚合物自组装结构的研究日益增多 .其中 ,嵌段共聚物在选择性溶剂中的胶束行为的研究非常引人瞩目 [1～ 3] .其表现出诸多常规尺寸所不具备的特殊性能 ,使得纳米胶束不仅在理论上有研究价值 ,而且在材料化学、生物医学和环境科学等领域都具有广阔的应用前景 .Ma等[4 ] 对聚丙烯酸和聚苯乙烯接枝共聚物的研究发现聚合物接枝率和聚合物浓度以及溶液离子强度对胶束结构有影响 ;Zhang等 [1,5] 对不同嵌段比例的苯乙烯 -丙烯酸嵌段共聚物的自组装行为的研究 ,发现不同嵌段比例所对应的纳米结构不同 ;而胶束表面…     

苯乙烯-p-乙烯基苯甲酸两亲性嵌段共聚物在乙醇中自组装行为的电镜观察

两亲性嵌段共聚物在只对其中一链段为良溶剂的选择性溶剂中 ,能够自组装形成胶束 .胶束的形态和尺寸大小依赖于两链段的性质 ,共聚物的组成、浓度、溶剂的性质等[1] .这一性质使得嵌段共聚物在分子识别、药物和其他物质的输送、基因疗法、水系涂料、污染物的除去、纳米复合材料的制备、催化剂以及传感器等方面展示着潜在的应用前景 .因此 ,两亲性嵌段共聚物的合成及其在选择性溶剂中的自组装行为的研究近年来颇受关注[2 ] .依据两链段的比例不同 ,嵌段共聚物可形成星状胶束和“板寸头”(Ｃｒｅｗ ｃｕｔ)型胶束[3 ] .当可溶段远比不溶段长时…     

聚苯乙烯-丙烯酸嵌段共聚物在不同pH值和Ca2+浓度下的胶束行为

近年来, 对具有纳米尺寸的聚合物自组装结构的研究日益增多. 其中, 嵌段共聚物在选择性溶剂中的胶束行为研究得最为广泛和深入[1~5]. 纳米胶束表现出诸多常规尺寸材料所不具备的特殊性能, 在材料化学、生物医学以及环境科学等领域有广阔的应用前景. Webber等[6]对聚丙烯酸和聚苯乙烯接枝共聚物的研究发现, 聚合物的接枝率和聚合物浓度以及溶液离子强度对胶束结构有影响; Eisenberg等[1,7]对不同嵌段比例的苯乙烯-丙烯酸嵌段共聚物的自组装行为进行研究发现, 不同嵌段比例所对应的胶束结构不同. 胶束形成的环境对胶束的形成与稳定性的影响是人们研究的重点. 本文报道了聚苯乙烯-丙烯酸嵌段共聚物在水中的胶束行为, 着重讨论了溶液pH值和钙离子浓度对聚丙烯酸链段相互作用的影响.     

嵌段共聚物自组装及其在纳米材料制备中的应用(上)

嵌段共聚物分子链中，嵌段间的相互热力学不相容性及化学键相连接性，使体系发生自组装，通过适当的分子及体系设计，嵌段共聚物体系能够自组装形成丰富的周期性有序微结构。本文概要地总结了嵌段共聚物体系主要的三方面自组装物理行为：本体自组装、在选择性溶剂中的缔合，及薄膜自组装，同时，介绍了这三方面的一些新的研究进展。     

嵌段共聚物自组装的研究进展

自组装是分子间通过非共价键相互作用自发组合形成的一类结构明确、稳定,同时具有某种特定功能或性能的分子聚集体或超分子结构的现象.嵌段共聚物不仅可以在本体中自组装,还能在溶液中自组装.本文综述了嵌段共聚物在溶液中自组装的规律及其主要影响因素,包括嵌段共聚物链段长度、选择性溶剂的性质、嵌段共聚物的浓度、溶液的pH值等;并介绍...     

单一分子量含氟嵌段共聚物的本体及薄膜自组装研究

嵌段共聚物导向自组装作为一种自下而上的图案化工艺,受到工业界和学术界的广泛关注.然而,导向自组装中缺陷率与分子参数之间的关系研究尚不清晰.本文工作基于模块化合成策略,利用迭代指数增长法并结合巯基-双键的点击反应成功制备了高χ低N的单一分子量含氟聚酯嵌段共聚物(oLA_n-FPOSS).单一分子量特征可以排除多分散性对自组装行为的影响.本体自组装研究表明聚酯嵌段和含氟嵌段具有强相分离驱动力,可以形成特征尺寸小于10 nm的六方柱状相结构(HEX).在薄膜自组装中,嵌段共聚物经过简单的热退火可以在硅片表面形成平行基底排布的柱状纳米图案.此外,通过对比研究不同链长单一分子量嵌段共聚物的薄膜组装行为,发现随着嵌段共聚物链长的增长薄膜组装图形缺陷率明显下降,初步揭示了薄膜自组装过程中缺陷形成对嵌段共聚物链长的依赖性.     

刺激响应性刚柔嵌段共聚物的自组装

刚柔嵌段共聚物是指刚性链段和柔性链段以共价键相连形成的共聚物。不仅由于刚性链段有序排列的特点使得其自组装行为更为丰富多样,而且刚性分子将优异的功能特性赋予到超分子组装体中,有望实现超分子材料的功能应用。这类嵌段共聚物在溶液中自组装形成的聚集体会对外界的刺激(例如pH、光、温度、化学添加剂等)敏感,产生聚集体形态的变化。本文选取了部分典型的具有刺激响应性的刚柔嵌段共聚物,介绍了其智能自组装行为,并对其良好的发展前景做了展望。     

偶氮液晶嵌段共聚物自组装和光响应性研究进展

偶氮液晶嵌段共聚物是指分子中带有偶氮苯基团的液晶嵌段共聚物.偶氮液晶嵌段共聚物兼具偶氮聚合物的光响应性和液晶嵌段共聚物自组装形成多尺度有序结构的特性,是一类有重要应用前景的新材料.本文简要综述了近10年来偶氮液晶嵌段共聚物的研究进展,以几种典型的偶氮液晶嵌段共聚物为例,介绍嵌段共聚物在本体以及溶液状态下自组装,自组装形貌的光致变化,以及偶氮液晶嵌段共聚物在光全息存储领域等的研究进展.     

柱状相聚苯乙烯-b-聚乳酸的合成及引导组装

设计并合成了2种柱状相结构的聚苯乙烯-b-聚乳酸(PS-b-PLA)两嵌段共聚物,并表征了它们在化学图案上的引导自组装行为。在辛酸亚锡(Sn(Oct)_2)催化下,采用羟基官能化的聚苯乙烯(PS-OH)大分子引发剂分别引发外消旋丙交酯(rac-LA)和左旋丙交酯(L-LA)开环聚合,制备了两个相对分子质量相近但构型不同的PS-b-PLA:PS-b-PDLLA和PS-b-PLLA。通过核磁共振波谱仪(NMR)、凝胶渗透色谱仪(GPC)、示差扫描量热仪(DSC)、热重分析仪(TGA)、小角X射线衍射仪(SAXS)等测试手段对两个嵌段共聚物的性质进行了表征。然后,将PS-b-PDLLA和PS-b-PLLA薄膜在六方点阵化学图案模板上加热引导自组装,得到长程有序排列的六方柱状相结构。相对于柱状相的PS-b-PLLA,柱状相的PS-b-PDLLA具有较大的拉伸比例,可以在更大的周期范围内组装出规整的六方结构。这一结果与层状相PS-b-PDLLA和PS-b-PLLA薄膜在线性化学图案上组装的结果相似。     

The synthesis of P(MAn-co-St)-b-PS-b-P(MAn-co-St) block copolymers by RAFT polymerization and the nanostructure of their self-assembly aggregates

A series of block copolymers of styrene, maleic anhydride and acrylic acid were synthesized by the reverse addition–fragmentation chain transfer (RAFT) process. The structure, molecular weight and polydispersity index were determined by FTIR, ¹H NMR, SEC&MALLS and DSC analysis. The results showed that the polymerization occurred in a living and controlled manner. Multiple self-assembled nanostructures of these block copolymers were investigated by transmission electron microscopy (TEM). Tetrahydrofuran (THF), N,N-dimethylformamide (DMF) and 1,4-dioxane were used as the common solvents and twice-distilled water as the selective solvent to clarify the effects of the solvent. The results revealed that with the increase of the extension degree of the core, non-spherical aggregates were easily formed, the composition of the copolymers influences the aggregation behavior, and other factors also influence the self-assembly, such as hydrolysis, temperature, annealing time, molecular architecture etc. A mechanism is proposed to illustrate the formation of the various aggregates of P(MAn-co-St)-b-PS-b-P(MAn-co-St) copolymer, which were confirmed by TEM results.     

两亲性含糖嵌段共聚物在水中分子聚集形态的转变

两亲性嵌段共聚物在不同的介质中可形成不同形态的有序分子聚集体［１～３］．当其亲水段长度远大于亲油段时,在水中主要形成球形胶束［１］;但当亲水段长度远小于亲油段时,则形成多种形态的分子聚集体,即所谓的“ｃｒｅｗ－ｃｕｔ”聚集体,如球形、柱状、层状、囊泡和管状等［４］．Ｅｉｓｅｎｂｅｒｇ等［４～６］详细研究了聚苯乙烯－ｂ－聚丙烯酸在水中的“ｃｒｅｗ－ｃｕｔ”聚集体,发现聚集体的形态和多种因素有关,如共聚物组成、溶剂、ｐＨ值和金属离子等．以两亲分子形成的囊泡不但可以用来模拟生物膜的结构,而且在药物载体…     

Micelle formation of a diblock copolymer having pyridine as pendant groups by carboxylic acids in nonselective solvents

The micelle formation of a poly(4-pyridinemethoxymethylstyrene)-block-polystyrene diblock copolymer (PPySt-b-PSt) was investigated in nonselective solvents using bifunctional and trifunctional carboxylic acids. The copolymer showed no self-assembly in 1,4-dioxane and tetrahydrofuran (THF) because the PPySt and PSt blocks were solvophilic to the solvents. Dynamic light scattering studies demonstrated that the copolymer formed micelles in the nonselective solvents in the presence of bifunctional carboxylic acids. Oxalic acid, maleic acid, citric acid, and phospholic acid promoted the micellization, while malonic acid, succinic acid, and glutalic acid had no effect on the micellization. The micellar size, aggregation number, and critical micelle concentration were dependent not only on the acid strength but also on the type of acid and the functionality. The micellization was also affected by the solvent quality. The micellization proceeded more effectively in 1,4-dioxane than in THF. It was found that the micellization occurred by hydrogen bonding between the pyridine moiety and the carboxylic acid and by the interaction among the carboxylic acids. This is because the copolymer needed over an equivalent of the acid to the PySt unit to complete the micellization. Furthermore, monofunctional carboxylic acid such as trichloroacetic acid and trifluoroacetic acid promoted the micellization, although dichloroacetic acid had no effect on the micellization.     

On modulating the self-assembly behaviors of poly(styrene-b-4-vinylpyridine)/octyl gallate blends in solution state via hydrogen bonding from different common solvents

We have investigated the complexation-induced phase behavior of the mixtures of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) and octyl gallate (OG) due to hydrogen bonding in different solvents. The Fourier transform infrared spectroscopic result indicates that the hydrogen-bonding was formed between the P4VP blocks and OG in both THF and DMF, implying the P4VP blocks can bind to OG. For PS-b-P4VP/OG mixture in chloroform, the morphological transitions were induced from the unimer configuration to swollen aggregate and complex-micelles by adding OG. Interestingly, the complex-micelles can lead the formation of the honeycomb structure from chloroform solution. The PS-b-P4VP/OG mixture in THF, behaving an amphiphilic diblock copolymer in solution state, exhibited a series of morphological transitions from sphere, pearl-necklace-liked rod, worm-liked rod, vesicle, to core-shell-corona aggregates by increasing the OG content. In contrast, the PS-b-P4VP/OG mixture in DMF maintained the unimer configuration upon adding OG. Therefore, the complexation-induced morphology of the mixtures of PS-b-P4VP and OG can be mediated by adopting different common solvents to affect the self-assembly behavior.     

Solubility and solution thermodynamics of 2, 6-bis (4-hydroybenzylidene) cyclohexanone in pure and binary solvents at various temperatures

Solubility of 2, 6-bis (4-hydroxybenzylidene) cyclohexanone (BHBC) in pure solvents such as 1,4-dioxane, methanol, 1-butanol, 1-propanol, ethyl acetate, acetone, tetrahydrofuran (THF), glacial acetic acid, dimethyl sulphoxide (DMSO) and binary solvents dimethyl formamide (DMF) and (1-Propanol + Tetrahydrofuran) were investigated by gravimetric method at different temperature range. The experiment solubility increases with increase in temperature in both pure and binary solvents. The Maximum solubility is found in DMF at 328.15 K and for binary solvent mixture i.e. 1-propanol and THF (0.9 mol fraction) it was maximum at 318.15 K. Further modified Apelblate and Buchowski-Ksiazczak models were used for the theoretical calculation of solubility of BHBC in pure as well binary solvents. A satisfactory correlation of these models with experimental data was observed. The solution thermodynamics parameters like enthalpies, Gibb's free energy of dissolution and entropy of solutions were calculated using Van't Hoff and Gibb's equation, which reveals the solvation mechanism is non-spontaneous and entropy driven.     

Noncovalent Macromolecular Architectures of Oligo(p-phenylenevinylene)s (OPVs): Role of End Functional Groups on the Gelation of Organic Solvents

Summary: Self-assembly of a few OPV derivatives having different end functional groups to aggregates, fibrous networks and organogels are discussed. OPV1 and OPV2 functionalized with ester moieties form gels in nonpolar hydrocarbon solvents whereas OPV3 with carboxylic acid groups form gel from THF and dichloromethane. OPV4 with dicyano moieties form aggregates but could not gelate solvents. AFM and TEM studies revealed considerable difference in the morphology of the self-assembled structures of OPV1-4 . From the optical, morphological and gelation data it is concluded that the nature of the end functional groups strongly influences upon the self-assembly and gelation properties of OPVs.     

Soft confinement-induced morphologies of diblock copolymers

The self-assembly of diblock copolymers under soft confinement is studied systematically using a simulated annealing method applied to a lattice model of polymers. The soft confinement is realized by the formation of polymer droplets in a poor solvent environment. Multiple sequences of soft confinement-induced copolymer aggregates with different shapes and self-assembled internal morphologies are predicted as functions of solvent-polymer interaction and the monomer concentration. It is discovered that the self-assembled internal morphology of the aggregates is largely controlled by a competition between the bulk morphology of the copolymer and the solvent-polymer interaction, and the shape of the aggregates can be non-spherical when the internal morphology is anisotropic and the solvent-polymer interaction is weak. These results demonstrate that droplets of diblock copolymers formed in poor solvents can be used as a model system to study the self-assembly of copolymers under soft confinement.     

树枝状聚(醚-酰胺)基胶束的制备及其形貌研究

采用ε-己内酯(CL)开环聚合的方法首先合成树枝状聚(醚-酰胺)基(DPEA)星形聚合物star-PCL,再与异氰酸基封端的PEG(PEG-NCO)偶合制备了两亲性树枝状聚(醚-酰胺)基星形嵌段聚合物star-PCL-b-PEG.利用FT-IR、1H-NMR和GPC分析测试手段对star-PCL-b-PEG的结构进行了表征.通过滴加选择性溶剂的方法,制备了star-PCL-b-PEG以水为介质的类似"平头"聚集体胶束溶液.采用荧光光谱法测得star-PCL-b-PEG水溶液的临界胶束浓度(CMC)为1.623mg/L;采用激光光散射仪测得其在浓度0.15mg/mL和0.5mg/mL的流体力学半径分别为86.2nm和224.6nm,其多分散指数分别为0.115和0.197.透射电镜(TEM)观察发现胶束的形貌受共溶剂的特性,初始聚合物浓度,水含量等因素的影响.     

Thermodynamic functions of solvation of 1,4-dioxane in various solvents at 298.15 K

The standard changes in enthalpy during the solvation of 1,4-dioxane in methanol, ethyl acetate, DMF, and acetonitrile were determined from calorimetric data and compared with the literature data for a series of solvents with different polarities. The standard changes in the Gibbs energy during the solvation of 1,4-dioxane in a wide series of solvents were calculated from the activity coefficients reported in the literature. The variation of the solvation functions of low-polar 1,4-dioxane in the series of solvents was found to be consistent with the enthalpy-entropy compensation rule. The results for 1,4-dioxane were compared with those for its open-chain analog and related large cyclic molecules. The electrostatic interactions of the solute with the solvents did not markedly affect the thermodynamic characteristics of ether in media with different polarities, but affected the interaction of the solute with the solvent more significantly. The solvation of the small ring of 1,4-dioxane in aprotic solvents was accompanied by a more significant exothermal effect than in the case of its open-chain analog. The conclusion was drawn that the enthalpies of the formation of hydrogen bonds between 1,4-dioxane and the associated water and chloroform molecules in solution were smaller in magnitude than the bonds of the similar open-chain polyether.