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...     

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...     

ABC三嵌段共聚物的聚合诱导自组装研究

聚合诱导自组装(PISA)是一种在高浓度溶液中可连续大量制备纳米材料的新技术,结合计算模拟方法,研究其动力学过程可强化对PISA的认识和调控.通过耗散粒子动力学(DPD)模拟,研究了ABC三嵌段共聚物的聚合诱导自组装过程.先利用亲溶剂A链段引发B单体聚合,随着疏溶剂B链段的增长,AB二嵌段共聚物可组装并发生聚集体结构的连续转变,由球形胶束→蠕虫状胶束→层状结构→囊泡.再将C单体逐步聚合到AB共聚物上,调控C链段的亲疏溶剂性,可聚合诱导组装或解组装形成不同的ABC三嵌段共聚物聚集体.     

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(L-丙氨酸-co-羟丙-L-谷氨酰胺)无规共聚物的两亲性及其胶束行为研究

采用丙氨酸作为疏水聚合单体,谷氨酸作为亲水聚合单体,一步开环聚合反应,合成了具有两亲性的聚氨基酸无规共聚物.利用IR,1H-NMR等方法对所合成的聚合物进行了详细的表征,结果表明两种单体都能够按照投料比参加聚合反应生成无规共聚物.对比聚丙氨酸-聚羟丙谷氨酰胺嵌段共聚物,探讨了无规共聚物与嵌段共聚物在两亲性及结构性质上的差异和特点.研究表明,聚(L-丙氨酸-co-羟丙-L-谷氨酰胺)无规共聚物与嵌段共聚物一样,具有两亲性,在水溶液中也能够形成胶束,但胶束尺寸较嵌段共聚物要小,胶束形态也不像嵌段共聚物是规整的球形.实验发现,亲疏水单体的比例对胶束的形成有很大影响,P(A10-co-HPG40)所制得的胶束分散最为均匀.所形成的胶束以疏水的聚丙氨酸为内核,亲水的聚羟丙谷氨酰胺为外壳.     

三嵌段刷状共聚物的合成及溶液组装制备多孔纳米粒子

结合可控自由基聚合和铜催化的叠氮-炔环加成(Cu AAC)反应,合成了coil-brush-coil型三嵌段刷状共聚物.其中coil段为亲水性的聚(N,N′-二甲基丙烯酰胺)(PDMA),brush段为高密度接枝V形侧链的疏水性聚丙烯酸酯.由于其两亲性特征及刷状拓扑结构所赋予的主链刚性,该嵌段共聚物在选择性溶剂甲醇和乙醇中可分别自组装得到片状胶束和囊泡.刷状嵌段的V形侧链包含聚苯乙烯(PS)和聚左旋丙交酯(PLLA)2条链,它们在胶束(或囊泡)组装体的核(或壁)区发生微相分离得到有序的柱状相分离形貌.将离散柱状PLLA相水解,即可得到核或壁具有多孔结构的片状胶束或囊泡.     

两亲性/双疏性嵌段共聚物共混体系的自组装行为研究

采用耗散粒子动力学方法,研究了两亲性嵌段共聚物和双疏性嵌段共聚物共混体系的自组装行为,探讨了双疏性嵌段共聚物的浓度以及双疏性嵌段共聚物的嵌段体积分数对聚集体结构的影响.结果表明,随着双疏性嵌段共聚物浓度的增加,聚集体发生自囊泡到棒状胶束再到同心圆多舱胶束的转变,且当浓度较高时,同心圆多舱胶束的同心圆层数量与浓度密切相关.当双疏性嵌段共聚物中的嵌段体积分数降低时,球形胶束由同心圆结构转变为非同心圆结构.此外,利用Minkowski泛函方法表征了多舱胶束的形成过程,发现这是一个先形成大尺度球形结构、再形成小尺度内核结构的分级组装过程.     

两亲性聚合物刷的合成和溶液自组装

结合可控自由基聚合和铜催化的叠氮-炔环加成(Cu AAC)反应,合成了一系列Ab BA型两亲性的聚合物刷.其中A段为亲水性的聚(N,N'-二甲基丙烯酰胺)(PAm);B段为高密度接枝的聚合物刷,其侧链为疏水性的聚苯乙烯(PS).通过核磁氢谱(1H-NMR),凝胶渗透色谱(GPC)表征了聚合物刷的组成及结构,其侧链接枝密度约为100%.研究了亲水链段含量不同的聚合物刷在多种条件下的溶液自组装行为,通过透射电子显微镜(TEM)表征了组装体的形貌.在相同的组装条件下,两亲性聚合物刷中亲水链段含量较高时(5%),组装体形貌为球形,而随着亲水链段含量降低,形貌向片层状胶束和囊泡转变.对聚合物刷PAm195-b-(PA-g-PS67)153-b-PAm195的自组装研究表明,提高初始浓度促使组装体形貌向片层和囊泡转变;采用与PS的溶度参数相近的良溶剂,可提高胶束核的活动性,组装体更容易形成囊泡(热力学稳定态);而采用与PS的溶度参数相差大的选择性溶剂时,组装体倾向于聚集形成大尺寸的囊泡.     

无规共聚物自组装球形胶束表面亲水性的耗散粒子动力学模拟

建立了含不同亲疏水粒子比的双亲性无规共聚物粗粒化模型. 采用耗散粒子动力学方法模拟了两亲性无规共聚物选择性溶剂自组装球形胶束表面的亲水性能. 模拟结果表明, 无规共聚物在选择性溶剂中自组装得到实心球形胶束, 球形胶束表面的亲水性与聚合物链亲水粒子含量、溶剂的选择性有关. 随着聚合物链所含亲水粒子增加, 球形胶束表面的亲水性增强. 球形胶束表面的亲水性随着疏水粒子与溶剂粒子间的排斥参数增大而增强, 模拟结果与实验结论一致. 该模拟方法给出的胶束微结构信息可以为双亲无规共聚物分子设计及自组装双亲胶束制备提供一定的理论指导.     

聚合物囊泡尺寸均一性及其膜冠结构调控的研究进展

聚合物囊泡是由两亲性嵌段共聚物制备而成的一种具有独特中空结构的纳米聚集体.聚合物囊泡的中空结构、囊泡的内外亲水冠以及亲水冠中间膜层的两亲性赋予了聚合物囊泡选择性封装亲水性和疏水性药物的能力,这使得聚合物囊泡在药物负载与释放、靶向识别等生物医药领域具有潜在的应用价值.聚合物囊泡能否实现其潜在应用价值还依赖于人们能否精准调控聚合物囊泡的膜冠结构、尺寸以及尺寸均一性等微观结构参数.因此,本文针对近期有关嵌段共聚物囊泡尺寸均一性和聚合物囊泡膜冠结构调控的研究进展进行了介绍,从而使人们通过物理手段有效地调控聚合物囊泡的微观结构,为制备膜冠结构可控、尺寸均一的聚合物囊泡提供新思路.     

可控自由基聚合与其它活性聚合方法结合制备嵌段共聚物

可控自由基聚合与其它聚合方法结合，可以制备多种类型的嵌段共聚物，因此得到了广泛关注。本文着重介绍可控自由基聚合与离子开环聚合、阴离子聚合、烯类单体的阳离子聚合及其它活性聚合方法结合制备嵌段共聚物的研究现状和进展。     

FORMATION OF FLOWER-LIKE AGGREGATES FROM SELF-ASSEMBLING OF MICELLES WITH PEO SHELLS AND CROSS-LINKED POLYACRYLAMIDE CORES

Amphiphilic block copolymers,poly(ethylene oxide)-b-poly(N-acryloxysuccinimide) (PEO-b-PNAS) with various molecular weights have been successfully synthesized by atom transfer radical polymerization (ATRP) of NAS using functionalized PEO (PEO-Br) as ATRP macroinitiator.The self-assembling of the block copolymers in water,which is a good solvent for PEO and a non-solvent for PNAS.yielded spherical core-shell micelles with PNAS as core and PEO as shell.The cross-linked reaction of oxysuccinimide in PNAS ch...     

Controlled/living heterogeneous radical polymerization in supercritical carbon dioxide

Supercritical carbon dioxide (scCO₂) is an inexpensive and environmentally friendly medium for radical polymerizations. ScCO₂ is suited for heterogeneous controlled/living radical polymerizations (CLRPs), since the monomer, initiator, and control reagents (nitroxide, etc.) are soluble, but the polymer formed is insoluble beyond a critical degree of polymerization (J_crit). The precipitated polymer can continue growing in (only) the particle phase giving living polymer of controlled well‐defined microstructure. The addition of a colloidal stabilizer gives a dispersion polymerization with well‐defined colloidal particles being formed. In recent years, nitroxide‐mediated polymerization (NMP), atom transfer radical polymerization (ATRP), and reversible addition fragmentation chain transfer (RAFT) polymerization have all been conducted as heterogeneous polymerizations in scCO₂. This Highlight reviews this recent body of work, and describes the unique characteristics of scCO₂ that allows composite particle formation of unique morphology to be achieved. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3711–3728, 2009     

自由基活性聚合及其最新进展

本文介绍了实现自由基活性聚合的动力学、热力学条件及可能的途径。在这些条件下自由基保持稳定的低浓度，增长链自由基与休眠种处于动力学平衡动态，可有效地控制聚合反应，使聚合反应具有聚合物分子量随反应时间、单体转化率成线性增长关系及所得聚合物分子量分布较窄的特征，并且在加入第二单体时可继续生成嵌段共聚物。     

苯乙烯微乳液种子聚合

通过观测苯乙烯微乳液种子聚合前后体系内聚合物粒子大小及其分布的变化发现,无论是γ射线还是KPS引发,聚合过程中都没有新的聚合物粒子生成。尽管聚合前体系中存在单体溶胀的胶束,但在聚合过程中这些胶束主要充当单体仓库,自己成核聚合的几率很低。由于微乳液种子聚合体系内,单体量相对较低,聚合物粒子数目很大,其聚合动力学明显不同于常规乳液种子聚合。     

Mechanistic Transformations Involving Radical and Cationic Polymerizations

Mechanistic transformation approach has been widely applied in polymer synthesis due to its unique feature combining structurally different polymers prepared by different polymerization mechanisms.Reported methods for the formation of block and graft copolymers through mechanistic transformation involve almost all polymerizations modes.However,certain polymerization processes require extensive purification processes,which can be time-consuming and problematic.Recent developments on controlled/living polymerizations involving radical and cationic mechanisms with the ability to control molecular weight and functionality led to new pathways for mechanistic transformations.In this mini-review,we systematically discussed relevant advances in the field through three main titles namely(i)from radical to cationic mechanism,(ii)from cationic to radical mechanism,and(iii)application of specific catalyst systems for both radical and cationic polymerizations.     

Synthesis and characterization of amphiphilic triblock polymers by copper mediated living radical polymerization

2-Dimethylaminoethyl methacrylate (DMAEMA) and 2-diethylaminoethyl methacrylate (DEAEMA) block copolymers have been synthesized by using poly(ethylene glycol), poly(tetrahydrofuran) (PTHF) and poly(ethylene butylenes) macroinitiators with copper mediated living radical polymerization. The use of difunctional macroinitiator gave ABA block copolymers with narrow polydispersities (PDI) and controlled number average molecular weights (M_n’s). By using DMAEMA, polymerizations proceed with excellent first order kinetics indicative of well-controlled living polymerization. Online ¹H NMR monitoring has been used to investigate the polymerization of DEAEMA. The first order kinetic plots for the polymerization of DEAMA showed two different rate regimes ascribed to an induction period which is not observed for DMAEMA. ABA triblock copolymers with DMAEMA as the A blocks and PTHF or PBD as B blocks leads to amphiphilic block copolymers with M_n’s between 22 and 24 K (PDI 1.24-1.32) which form aggregates/micelles in solution. The critical aggregation concentrations, as determined by pyrene fluorimetry, are 0.07 and 0.03 g dm⁻¹ for PTHF- and PBD-containing triblocks respectively.     

原子转移自由基聚合及可控自由基聚合

以作者在原子转移自由基聚合领域的研究成果为主导,结合国内外文献,对近年来出现的颇具影响的可控自由基聚合体系与进行了评述与展望。     

Micellar structures of poly(styrene-b-4-vinylpyridine)s in THF/toluene mixtures and their functionalization with gold

The effects of the block copolymer composition and the solvent selectivity on the micellar morphologies of poly(styrene- b-4-vinylpyridine)s (PS- b-P4VPs) and their functionalizations with gold were studied in 10 mg/mL solutions using small-angle X-ray scattering and transmission electron microscopy (TEM). The solvent selectivity for the PS block was controlled by toluene/tetrahydrofuran (THF) mixtures in which toluene and THF are selective for PS and nonselective, respectively. The micellar structure was strongly dependent on phi (wt % toluene in toluene/THF mixture) and the composition of the block copolymers. PS(12K)- b-P4VP(11.8K) (symmetric) showed spherical micelles in the entire range of phi except phi = 0 (THF, nonselective solvent). PS(3.3K)- b-P4VP(18.7K) (asymmetric, longer P4VP) showed multiple morphologies with transitions from spheres to cylinders and finally to vesicles with an increase in phi. PS(19.6K)- b-P4VP(5.1K) (asymmetric, longer PS) showed spherical micelles only at the narrow ranges of 90 wt % 相似文献   

Direct through anionic,cationic, and radical active species: Terminal carbon–halogen bond for “controlled”/living polymerizations of styrene

In this work, we examined the synthesis of novel block (co)polymers by mechanistic transformation through anionic, cationic, and radical living polymerizations using terminal carbon–halogen bond as the dormant species. First, the direct halogenation of growing species in the living anionic polymerization of styrene was examined with CCl₄ to form a carbon–halogen terminal, which can be employed as the dormant species for either living cationic or radical polymerization. The mechanistic transformation was then performed from living anionic polymerization into living cationic or radical polymerization using the obtained polymers as the macroinitiator with the SnCl₄/n‐Bu₄NCl or RuCp^*Cl(PPh₃)/Et₃N initiating system, respectively. Finally, the combination of all the polymerizations allowed the synthesis block copolymers including unprecedented gradient block copolymers composed of styrene and p‐methylstyrene. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 465–473