两亲性嵌段共聚物PMnEOS-b-PAA的可控合成及与PS-b-PAA共组装体的形貌

在苯乙烯单体的对位引入具有亲水性链段的乙二醇单元, 利用可逆加成断裂链转移聚合方法(RAFT), 可控合成了几种新的两亲性嵌段共聚物聚(4-乙烯基苄基乙二醇单甲醚)-b-聚丙烯酸(PMnEOS-b-PAA, n=1~3), 对其温敏和pH敏性质进行了初步研究. 同时, 研究了PMnEOS-b-PAA分别在亲水性环境下(四氢呋喃/水)和亲脂性环境下(四氢呋喃/甲苯)自组装体的形貌. 将聚对二乙二醇单甲醚苯乙烯-b-聚丙烯酸与聚苯乙烯-b-聚丙烯酸按质量比1:1[m(PMDEOS-b-PAA)/m(PS-b-PAA)=1:1]共混进行共组装, 在四氢呋喃/甲苯体积比为2∶1的混合溶剂中, 发现了一类新型具有均匀分布内部孔道且表面光滑的球形组装体. 进一步研究了该组装体的可重复性和组装机理, 为其后期应用于工业上的负载催化、 小分子识别与释放提供了一种新的策略.     

两嵌段共聚物反相溶剂中组装结构转变动力学的模拟研究

利用耗散粒子动力学方法,分别研究了不同结构的组装体在改变溶剂的选择性后,在溶液及界面上的结构演变动力学.模拟结果表明,在改变溶剂的选择性后,大球形胶束在溶液中转变形成反向球形胶束,而在界面上则转变形成反向环状胶束,当前模拟结果与已有的实验结果一致.此外,模拟结果还预测出,在改变溶剂的选择性后,环状胶束在溶液中转变形成反向环状胶束,而在界面处受限形成反向的支化蠕虫状胶束;蠕虫状胶束则在溶液中转变形成反向环状胶束,而在界面处受限形成多层纳米球结构;囊泡在溶液中转变形成分散的小胶束聚集体,而在界面处受限形成球形的补丁纳米粒子.     

Water-dispersible non-aqueous emulsions stabilized by a poly(butadiene)-b-poly(2-vinylpyridine) block copolymer

Submicron non-aqueous emulsions, of interest for biomedical and cosmetic formulations, were developed for the system comprising poly(ethylene glycol) (PEG) 400 and Miglyol 812, an enzymatic degradable liquid glycerine ester. These emulsions, with PEG 400 as continuous phase and Miglyol 812 droplets, in the size range of 200 nm, were stabilized by a poly(butadiene)-b-poly(2-vinylpyridine) (PBut-b-P2VP) block copolymer with a composition close to 50/50 wt%. The droplet size, stability and the rheological characteristics were examined as a function of the copolymer concentration. An original aspect of these anhydrous emulsions, with a water miscible continuous phase, is their water dispersibility without additional surfactant. In fact, the initial anhydrous emulsion is sterically stabilized and after water addition at low pH, the protonated P2VP sequence of the copolymer provides the electro-steric stabilization. This oil-in-water emulsion is characterized by sub micron sized Miglyol 812 droplets in an aqueous phase of PEG 400 and water at pH 1.     

载紫杉醇星型M-PLA-TPGS纳米颗粒的合成及其用于前列腺癌治疗药物载体的研究

合成了一种甘露醇引发的星型共聚物甘露醇-聚乳酸-聚乙三醇1000维生素E琥珀酸酯(M-PLATPGS).利用纳米沉淀法制备载紫杉醇M-PLA-TPGS纳米颗粒.纳米颗粒近似球形,粒径分布较窄.对载药纳米颗粒进行粒径、表面电荷、载药量、包封率和体外药物释放的表征,结果表明,体外药物释放呈双相释放模型,M-PLA-TPGS纳米颗粒在前列腺癌PC-3细胞中的摄取水平要高于PLGA和PLA-TPGS纳米颗粒.载紫杉醇M-PLA-TPGS纳米颗粒对于前列腺癌细胞的的毒性显著高于载紫杉醇PLA-TPGS纳米颗粒和商业制剂Taxol,证明星型M-PLA-TPGS聚合物作为纳米药物载体优于线性PLGA和PLA-TPGS聚合物.     

采用反应挤出三次加料法合成苯乙烯/异戊二烯/苯乙烯

以同向啮合双螺杆挤出机为反应器,采用苯乙烯和异戊二烯为聚合单体,以正丁基锂为引发剂,采用三次加料法合成苯乙烯/异戊二烯/苯乙烯(SIS)三嵌段热塑性弹性体.氢核磁共振(1H NMR)谱分析结果表明,共聚物中聚异戊二烯嵌段以1,4-结构为主.采用四氧化锇催化双氧水氧化降解聚合物分子链,利用凝胶渗透色谱对氧化降解后的聚苯乙烯碎片进行分析,证明共聚物分子为(聚苯乙烯-聚异戊二烯-聚苯乙烯)(PS-PI-PS)三嵌段结构.动态力学分析(DMA)及透射电子显微镜(TEM)分析结果表明,SIS具有两相分离结构.拉伸试验结果表明,共聚物拉伸强度与苯乙烯含量有关.     

Block copolymers at interfaces: Interactions with physiological media

Triblock copolymers (also known as Pluronics or poloxamers) are biocompatible molecules composed of hydrophobic and hydrophilic blocks with different lengths. They have received much attention recently owing to their applicability for targeted delivery of hydrophobic compounds. Their unique molecular structure facilitates the formation of dynamic aggregates which are able to transport lipid soluble compounds. However, these structures can be unstable and tend to solubilize within the blood stream. The use of nanoemulsions as carriers for the lipid soluble compounds appears as a new alternative with improved protection against physiological media. The interfacial behavior of block copolymers is directly related to their peculiar molecular structure and further knowledge could provide a rational use in the design of poloxamer-stabilized nanoemulsions. This review aims to combine the new insights gained recently into the interfacial properties of block copolymers and their performance in nanoemulsions. Direct studies dealing with the interactions with physiological media are also reviewed in order to address issues relating metabolism degradation profiles. A better understanding of the physico-chemical and interfacial properties of block copolymers will allow their manipulation to modulate lipolysis, hence allowing the rational design of nanocarriers with efficient controlled release.     

Colloidal micelles of block copolymers as nanoreactors,templates for gold nanoparticles,and vehicles for biomedical applications

Target drug delivery methodology is becoming increasingly important to overcome the shortcomings of conventional drug delivery absorption method. It improves the action time with uniform distribution and poses minimum side effects, but is usually difficult to design to achieve the desire results. Economically favorable, environment friendly, multifunctional, and easy to design, hybrid nanomaterials have demonstrated their enormous potential as target drug delivery vehicles. A combination of both micelles and nanoparticles makes them fine target delivery vehicles in a variety of biological applications where precision is primarily required to achieve the desired results as in the case of cytotoxicity of cancer cells, chemotherapy, and computed tomography guided radiation therapy.     

High angular-resolution automated visible-wavelength scanning angle Raman microscopy

A scanning angle (SA) Raman microscope with 532-nm excitation is reported for probing chemical content perpendicular to a sample interface. The instrument is fully automated to collect Raman spectra across a range of incident angles from 20.50 to 79.50° with an angular spread of 0.4 ± 0.2° and an angular uncertainty of 0.09°. Instrumental controls drive a rotational stage with a fixed axis of rotation relative to a prism-based sample interface mounted on an inverted microscope stage. Three benefits of SA Raman microscopy using visible wavelengths, compared to near infrared wavelengths are: (i) better surface sensitivity; (ii) increased signal due to the frequency to the fourth power dependence of the Raman signal, and the possibility for resonant enhancement; (iii) the need to scan a reduced angular range to shorten data collection times. These benefits were demonstrated with SA Raman measurements of thin polymer films of polystyrene or a diblock copolymer of polystyrene and poly(3-hexylthiophene-2,5-diyl). Thin film spectra were collected with a signal-to-noise ratio of 30 using a 0.25 s acquisition time.     

Influence of different inorganic salts on crystallization-driven morphological transformation of PCL-b-PEO micelles in aqueous solutions

Different inorganic salts, including NaSCN, NaCl, MgCl2 and Na2SO4, were added into the aqueous solution containing poly(ε-caprolactone)-b-poly(ethylene oxide)(PCL-b-PEO) semicrystalline micelles. The effects of inorganic salt on the micellar size and morphology were investigated with TEM and DLS. It is found that addition of NaSCN leads to increase of the micellar size, but the micelles remain to be spherical. By contrast, the other three inorganic salts can induce sphere-to-cylinder or sphere-to-lamella transformations of the PCL-b-PEO semicrystalline micelles. The alteration rate of the micellar size with the time after addition of the inorganic salts decreases in the following order: Na2SO4 NaCl ≈ MgCl2 NaSCN. These results were interpreted in terms of the "salting-out" ability of the cations and anions. The anions SO42- and Cl- have a stronger "salting-out" ability, driving the morphological transformations of the micelles and leading to a rapid change in micellar size. By contrast, SCN- has a weaker salting-out" ability. The cations Na+ and Mg2+ may associate with the PEO blocks, leading to a "salting-out" effect as well. However, the "salting-out" ability of cations is weaker than that of SO42- and Cl- anions, and the "salting-out" abilities of Na+ and Mg2+ are similar.     

pH-Sensitive Wettability Induced by Topologicaland Chemical Transition on the Self AssembledSurface of Block Copolymer简

pH-sensitive wettability of polystyrene-b-poly（4-vinylpyridine） （PS-b-P4VP） self assembled films, exhibiting superoleophobicity under water and hydrophilicity at low pH value, and oleophobicity under water and hydrophobicity at neutral condition, has been realized. The wettability properties resulted from the surface topological and chemical transition, which were confirmed by in situ AFM measurements under water at different pH. At low pH, P4VP chains, which were confined in the hexagonal-packed nanodomains, got protonated into a swollen state, while at high pH, P4VP chains were deprotonated into a collapsed state. The reversible protonation/deprotonation procedure on the molecular scale leads to surface topological and chemical transition, thereby pH-sensitive wettability.