分子量规整聚p-乙烯基苯甲酸及苯乙烯p-乙烯基苯甲酸两嵌段共聚物的合成

当两嵌段共聚物为由性质不同的规制 (Ｗｅｌｌ ｄｅｆｉｎｅｄ)分子量两链段所构成时 ,在只对其中一链段为良溶剂的选择性溶剂中 ,它能够自组装形成尺寸均一的胶束 .胶束的形态与共聚物的组成、浓度、溶剂的性质等关系密切[1] .因此 ,两嵌段共聚物的合成颇被关注[2 ] .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、催化剂以及传感器等方面展示着潜在的应用前景 .规制分子量的两嵌段共聚合物的合成主要通过阴离子、阳离子、开环易位、基团转移等活性或可控聚合来实现 .但是这些方法受到单体…     

多分散性对两亲性两嵌段共聚物在选择性溶剂中自组装行为影响的Monte Carlo模拟

采用Monte Carlo模拟方法研究了多分散性AB两亲性两嵌段共聚物在选择性溶剂中的自组装行为.模拟结果表明,嵌段共聚物的多分散性对体系在选择性溶剂中自组装所形成的胶束形貌结构有很大影响.当AB两嵌段共聚物的多分散系数由1.0增加至1.4时,体系中自组装所形成的胶束将会发生由囊泡到片层直至球状的一系列形态转变.通过统...     

ABA两亲性嵌段共聚物在双选择性溶剂中自组装行为的Monte Carlo模拟

采用Monte Carlo模拟方法研究了ABA两亲性三嵌段共聚物在两种选择性溶剂中的自组装行为.模拟结果表明,在保证溶剂总浓度一定的情况下,改变两种选择性溶剂的体积比对于ABA两亲性嵌段共聚物自组装所形成的胶束形貌结构有很大影响.随着双选择性溶剂体积比的改变,体系中胶束形貌结构将会发生由囊泡到层状,再到环状、棒状直至球...     

用SAXS/WAXS研究聚氧乙烯/聚氧丁烯嵌段共聚物在n-己烷中的结晶性球形胶束结构

嵌段共聚物在选择性溶剂中能够自组装形成胶束,胶束的不同形状与嵌段共聚物的结构、溶剂和浓度有关．无定形嵌段共聚物通常形成球形胶束,在某些情况下也可以形成其它形状的胶束,关于结晶性嵌段共聚物在无定形链段选择性溶剂中的胶束结构和形状的报道非常少．由于结晶和相似相溶两种作用力的竞争,使得这类胶束的形状丰富多变．通常结晶作用较强时,结晶性嵌段共聚物形成片状的胶束,当结晶组分比较少时,可形成棒状胶束,尽管理论上已经指出存在球形胶束,但尚无关于这方面的报道。     

两亲性嵌段共聚物的合成及其在离子液体中的自组装行为

采用阴离子开环聚合法合成了两亲性嵌段共聚物PLA-PEG-PLA.用FT-IR,1H NMR和GPC等手段对嵌段共聚物的结构组成进行了表征.两亲性嵌段共聚物在离子液体1-丁基-3-甲基咪唑六氟磷酸盐中能自组装成胶束,用透射电子显微镜观察了聚合物在离子液体中形成胶束的纳米结构.当疏水链长固定时,胶束的自组装形状主要依赖于亲水链的长度.两亲性共聚物在离子液体中可自组装成可控制结构的纳米胶束,这种纳米结构胶束在很多领域具有广泛的应用前景.     

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.     

嵌段共聚物在选择性溶剂中自组装过程的计算机模拟

嵌段共聚物由于各嵌段性质不同,在选择性溶剂中能够自发地组装形成众多形态结构各异的纳米结构,如纳米级的球状、棒状、环状、片层状、囊泡及复合胶束等。这些胶束结构在药物传输、催化、电子信息等众多领域都有潜在的应用价值。通过计算机模拟可以在线监控嵌段共聚物的组装过程、揭示其组装机理,明确各种因素对组装结构的影响规律,为实验研究提供思路和理论支持,因此越来越受到人们的广泛关注。本文主要综述了通过计算机模拟对嵌段共聚物在选择性溶剂中自组装研究的一些最新进展,详细讨论了影响嵌段共聚物自组装过程和胶束形貌的各种因素,并对这个领域未来的发展进行了展望。     

AB型聚乙二醇单甲醚-聚(L-丙氨酸)嵌段共聚物自组装过程的核磁共振研究

利用核磁共振方法研究了AB型双嵌段共聚物(MPEG45-b-PA32)在选择性溶剂中的自组装行为及胶束化过程.嵌段共聚物在三氟乙酸中聚氨基酸和聚乙二醇链段均处于自由运动状态,聚丙氨酸链段为无规线团结构.在向该溶液中逐渐加入氘代水的过程中,聚丙氨酸链段又重新聚集形成规整的二级结构.结合1H-NMR和COSY谱分析,结果显示这一自组装过程伴随着聚(L-丙氨酸)链段由无规线团向α-螺旋结构的构象转变,同时嵌段共聚物逐渐形成核-壳型胶束结构.利用透射电镜观察了所形成胶束的形态,嵌段共聚物主要形成粒径150 nm到220 nm的球形胶束.     

星形胶束自由能和聚集数的理论分析

ＡＢ型嵌段聚合物在选择性溶剂中将发生微相分离,形成一种球形胶束[1].所谓选择性溶剂是指此溶剂仅能溶解共聚物中某一链段,而对另一链段则为不良溶剂.对这一体系的实验研究是从80年代兴起的,主要采用现代测试技术来表征形成胶束的回转半径[2],动力学半径[3]、聚集数[4]和临界胶束浓度[5].从分子图景上看来,这种球形胶束包括两部分,内核(Ｃｏｒｅ)为密堆砌的链段Ａ;壳层(Ｃｏｒｏｎａ)为溶涨的链段.Ｈｅｌｆａｎｄ等[6]最早利用数值计算法来研究嵌段聚合物在本体中的微相分离的问题;Ｌｅｉｂｌｅｒ等[7]将此方法引入嵌段聚合物/均聚物体系.…     

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…     

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.     

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…     

EFFECTS OF STYRENE-ETHYLENE/PROPYLENE DIBLOCK COPOLYMER (SEP) ON THE COMPATIBILIZATION OF PP/PS BLENDS

The effects of styrene-ethylene/propylene (SEP) diblock copolymer on the morphology and mechanical propertiesof polypropylene/polystyrene (PP/PS) blends were investigated. The results showed that SEP diblock copolymer, acting as acompatibilizer in PP/PS immiscible blends, can diminish the coalescence of the dispersed particles, reduce their averageparticle size, change their phase morphologies significantly, and increase the mechanical properties. It was found that SEP has better compatibilization effects on the PP/PS (20/80) blends.     

pH responsive surfaces with nanoscale topography

We report the preparation of nanostructured adaptive polymer surfaces by diffusion of an amphihilic block copolymer toward the interface. The surface segregation of a diblock copolymer, polystyrene‐block‐poly(acrylic acid) (PS‐b‐PAA), occurred when blended with high molecular weight polystyrene employed as a matrix. On annealing, the polymer surfaces changed both the chemical composition and the hydrophilicity depending on the environment and pH, respectively. By exposure to either water vapor or air, the surface wettability varied between hydrophilic and hydrophobic. In addition, surface enrichment on diblock copolymer by water vapor annealing led to self‐assembly occurring at the interface. Hence, nanostructured domains can be observed by AFM in liquid media. Moreover, the PAA segments placed at the interface respond to pH and can switch from an extended hydrophilic state at basic pH values to a collapsed hydrophobic state in acidic media. Accordingly, the surface morphology changed from swelled micelles to nanometer size holes. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2982–2990, 2010     

Molecular design of multicomponent polymer systems. III. Comparative behavior of pure and tapered block copolymers in emulsification of blends of low-density polyethylene and polystyrene

Poly(hydrogenated butadiene-b-styrene) copolymers are very effective emulsifiers for blends of polystyrene and low-density or high-density polyethylene. It is shown that the extent of improvement in mechanical properties is dependent not only on the molecular weight but also on the structure of the diblock copolymer. A comparative study of the morphology and the mechanical behavior of modified low-density polyethylene/polystyrene blends demonstrates that a tapered diblock is more efficient than a pure diblock with the same composition and molecular weight. It is assumed that the unique behavior of the tapered sample results from its particular miscibility characteristics at the blend interface. The tapered copolymer could behave essentially as a solu-bilizing agent for the homopolymers at the interface and provide a “graded” modulus responsible for the improved mechanical response of the material.     

SEP对PP/PS共混物的增容作用

研究了苯乙烯 -乙烯 /丙烯二嵌段共聚物 (SEP)对聚丙烯 /聚苯乙烯 (PP/PS)共混物的形态和力学性能的影响。结果表明 ,SEP在PP/PS共混物中作为增容剂 ,降低了分散相的聚结 ,减小了分散相的平均粒子尺寸 ,大大改变了共混物的形态 ,提高了共混物的力学性能 ,对PP/PS( 2 0 /80 )共混物的增容作用较为显著     

iPS－b－iPP共聚物对iPS／iPP共混物的性能和形态影响的研究

报道了苯乙烯－丙烯等规嵌段共聚物（ｉＰＳ－ｂ－ｉＰＰ）增溶作用及ｉＰＳ－ｂ－ｉＰＰ／ｉＰＳ／ｉＰＰ三组分共混体系微观形态和力学性能的研究结果。ｉＰＳ－ｂ－ｉＰＰ的加入明显地改善了ｉＰＳ／ｉＰＰ二组分共混物的力学性能;共聚物含量超过１５％时,三组分共混物的抗冲击强度超过ＮＩＰＳ的抗冲击强度,并具有较高的耐热性。ＳＥＭ结果表明,ｉＰＳ－ｂ－ｉＰＰ在ｉＰＳ／ｉＰＰ共混中起到了相分散和相间“偶联”作用,并降低了共混体系的微相尺寸和增加相间相互作用或粘附性。ｉＰＳ－ｂ－ｉＰＰ／ｉＰＳ／ｉＰＰ共混合金具有高的软化温度和刚性。     

High‐Density Liquid‐Crystalline Polymer Brushes Formed by Surface Segregation and Self‐Assembly

High‐density polymer brushes on substrates exhibit unique properties and functions stemming from the extended conformations due to the surface constraint. To date, such chain organizations have been mostly attained by synthetic strategies of surface‐initiated living polymerization. We show herein a new method to prepare a high‐density polymer brush architecture using surface segregation and self‐assembly of diblock copolymers containing a side‐chain liquid‐crystalline polymer (SCLCP). The surface segregation is attained from a film of an amorphous base polymer (polystyrene, PS) containing a minor amount of a SCLCP‐PS diblock copolymer upon annealing above the glass‐transition temperature. The polystyrene portion of the diblock copolymer can work as a laterally mobile anchor for the favorable self‐assembly on the polystyrene base film.     

Self-assembly behavior of carbon nanotubes modified by amphiphilic block copolymer

Block copolymers of poly(tert-butyl methyacrylate) (PtBMA) and polystyrene (PSt) were grafted onto multi-walled carbon nanotubes (MWNTs) by the reaction of azide groups at the copolymer chain end with the surface of MWNTs. After hydrolysis, PtBMA block was transformed to polymethyacrylic acid (PMAA) block, and amphiphilic diblock copolymer-modified MWNTs were finally obtained. The modified MWNTs were characterized by XPS, TGA, FTIR, and Raman, and the results showed that the amphiphilic diblock copolymers were grafted onto MWNTs by the covalent bond. The TEM and SEM observation showed that PMAA-b-PSt copolymer modified MWNTs (S2) formed self-assembly tube bundles with the size up to 20 μm in both ethanol and chloroform. However, PtBMA-b-PSt copolymer modified MWNTs (S1) only formed small-size aggregates or dispersed as single-modified MWNTs. The dispersion stability tests showed that S1 had good dispersion stability in several solvents (water, ethanol, acetone, and chloroform) even after 20 days. Due to the big-size tube bundles formed by self-assemble S2, the dispersion stability of S2 in above all solvents decreased, but it was still much better than that of pristine MWNTs.     

Syntheses of polyolefin‐based stereoregular diblock copolymers for self‐assembled nanostructures

The preparation of polyolefin‐based stereoregular diblock copolymers by postpolymerization of ethenyl‐capped syndiotactic polypropylene‐based propylene/norbornene copolymer (sPP‐based P‐N copolymer) led to the successful generation of a structurally uniform stereoregular diblock copolymer for self‐assembly studies. The ethenyl‐capped prepolymer was prepared by conducting propylene/norbornene copolymerization in the presence of Me₂C(Cp)(Flu)ZrCl₂/MAO. Ozonolysis of ethenyl‐capped sPP‐based P‐N copolymer provided the formyl group end‐capped, end‐functionalized prepolymer with a quantitative functional group conversion ratio. Subsequently, connecting the formyl end‐group of the stereoregular prepolymer by coupling with living anionic polystyrene resulted in the high yield production of stereoregular diblock copolymer (sPP‐based P‐N‐block‐polystyrene), which is difficult to prepare by other methods. The resulting stereoregular diblock copolymer possesses precise chemical architecture to self‐organize into consistent nanostructures as evidenced by transmission electron microscopy and small angle X‐ray scattering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4843–4856, 2008