~1H-NMR法测定苯乙烯-乙烯-丁二烯-苯乙烯嵌段共聚物的加氢度和微观结构

采用核磁共振氢谱(1H-NMR)法测定苯乙烯-乙烯-丁二烯-苯乙烯嵌段共聚物(SEBS)的加氢度和微观结构。结果表明,采用镍系催化剂对苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)进行加氢反应制备SEBS时,在苯乙烯链段未参与加氢反应的前提下,通过对SBS和SEBS的谱峰进行归属,建立了用1H-NMR测定SEBS总加氢度的方法,且无需已知苯乙烯的摩尔分数,适用范围较宽;用该法还可直接得到SEBS中各微观结构含量和丁二烯1,2-结构和1,4-结构的加氢度。     

The thermodynamics of micelle formation by a polystyrene-b-polyisoprene block copolymer in N,N′-dimethylacetamide

The thermodynamics of micelle formation by a polystyrene-b-polyisoprene block copolymer in N,N′-dimethylacetamide, which is a selectively bad solvent for polyisoprene, has been investigated. The micelles have a very narrow size distribution enabling the association process to be treated as a single-stage equilibrium. The temperature dependence of the critical micelle concentration was determined from measurements of scattering intensity against temperature carried out at six concentrations within the range 2.3 × 10⁻⁷ to 1.2 × 10⁻⁴ mol dm⁻³. A plot of 1n (c.m.c.) against T⁻¹ gave a value for the standard enthalpy of micellisation (per mole of copolymer chains in the micelle) of − 153 ± 6 kJ mol⁻¹. The standard entropy contribution (-TΔS^Θ) to the standard free energy of micellisation was found to be positive. These results are in strong contrast to those reported for synthetic surfactants in aqueous media for which a favourable standard entropy change is the factor mainly responsible for micelle formation.     

生物可降解两亲性嵌段共聚物胶束的制备及其对叶酸的控制释放

以甲氧基聚乙二醇(mPEG)为引发剂,在辛酸亚锡催化下引发ε-环己内酯(CL)开环聚合,合成了聚乙二醇-聚己内酯两亲性嵌段共聚物(mPEG-PCL)。通过FTIR、1H-NMR及GPC等表征手段确定了mPEG-PCL的组成及结构。采用芘荧光探针法、透射电镜和动态激光光散射研究了聚合物在水中的自组装行为。结果表明:聚合物在水溶液中能够自组装形成粒径小于100 nm的规则球状胶束,且具有较低的临界胶束浓度(7.35×10-3 g/L);模型药物(叶酸)成功负载于聚合物纳米胶束内,并且能延缓叶酸的释放,其释药速率受载药量和释放介质pH的影响。     

Crosslinking of unsaturated polyester resins studied by low-resolution 1H-NMR spectroscopy

The curing behavior of five unsaturated polyester resins with different molar ratios of styrene to the double bonds in the polyester chain (MR) was investigated. The gel time was measured according to a standard method by the Society of the Plastic Industry (SPI) and by low-resolution pulse nuclear magnetic resonance (LRP-NMR). The gel and curing times decreased and the maximum temperature of the reaction increased when the MR was decreased. The proton mobilities and populations were measured by LRP-NMR. Three components could be seen in the crosslinking reaction: styrene (very mobile, T₂ ≅ 3 s), free polyester polymers (less mobile, T₂ ≅ 150 ms), and cured resin (immobile, T₂ ≅ 0.04 ms). The third component, cured resin, could be detected at the gel point. At this point, the proton mobilities of styrene and free polyester polymers were rapidly decreasing and the proton populations of the cured resin started to increase. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 77–83, 1997     

Time-resolved GISAXS and cryo-microscopy characterization of block copolymer membrane formation

Time-resolved grazing-incidence small-angle X-ray scattering (GISAXS) and cryo-microscopy were used for the first time to understand the pore evolution by copolymer assembly, leading to the formation of isoporous membranes with exceptional porosity and regularity. The formation of copolymer micelle strings in solution (in DMF/DOX/THF and DMF/DOX) was confirmed by cryo field emission scanning electron microscopy (cryo-FESEM) with a distance of 72 nm between centers of micelles placed in different strings. SAXS measurement of block copolymer solutions in DMF/DOX indicated hexagonal assembly with micelle-to-micelle distance of 84–87 nm for 14–20 wt% copolymer solutions. GISAXS in-plane peaks were detected, revealing order close to hexagonal. The d-spacing corresponding to the first peak in this case was 100–130 nm (lattice constant 115–150 nm) for 17 wt% copolymer solutions evaporating up to 100 s. Time-resolved cryo-FESEM showed the formation of incipient pores on the film surface after 4 s copolymer solution casting with distances between void centers of 125 nm.     

Effect of urea and salt on micelle formation of zwitterionic surfactants

The effect of urea on micelle formation of zwitterionic surfactants was investigated by measuring conductivity, critical micelle concentration (CMC), relative viscosity, and the spectrophotometric shift in wavelength. We examined two zwitterionic surfactants, N,N-dimethyl dodecylamine N-oxide and N,N-dimethyl tetradecylamine N-oxide (DMTAO). The CMC values of the surfactants increased with the addition of urea. Also, the relative viscosity of the surfactant solutions decreased at higher concentrations of urea and increased with increasing KCl concentration. The absorbance maxima of the surfactants decreased with increasing urea concentration.     

Effect of composition of added random copolymer on the phase behavior of block copolymer

Blends of styrene-butadiene diblock copolymer (S-B, 52 wt% styrene content) and styrene-butadiene random copolymer (SBR) of various styrene compositions were studied by small-angle X-ray scattering, light scattering, and transmission electron microscopy. The composition of random copolymer plays an important role in the solubilization of SBR in S-B. The order-disorder transition temperature, T_ODT, decreases linearly with the addition of SBR. T_ODT decreases as the symmetry in SBR composition increases and shows the highest value in the case of homopolymers. Asymmetric butadiene-rich SBR dissolves mostly into PB microdomain of S-B to increase lamella microdomain spacing, D, and its addition makes the overall microdomains of S and B in the mixture more asymmetrical. Symmetric SBR is localized into the interface of S-B microdomain to reduce unfavorable S-B contact at the interface. The phase diagram for S-B containing asymmetric SBR shows a succession of mixed mesophases of different morphologies from lamellae and cylinder to disordered liquid phases, whereas the phase diagram containing symmetric SBR shows two homogeneous phases and one region of two-phase coexistence, where macroscopically separated phases coexist together.     

Solution conformation of endothelin determined by means of 1H-NMR spectroscopy and distance geometry calculations

The structure of endothelin-1 (ET-1), an endothelial cell-derivedpeptide with vasoconstricting activity, was determined in anaqueous solution by means of a combination of NMR and distancegeometry calculations. The resulting structure is characterizedby an -helical conformation in the sequence region, Lys9-Cys15.Furthermore, an extended structure and a turn structure existin the Cys1-Ser4 and Ser5-Asp8 regions respectively, and nopreferred conformation was found for the C-terminal part ofthe peptide which was not uniquely constrained by the NMR data.These structural elements, the -helical structure in the sequenceportion, Cys-X-X-X-Cys, and the extended structure in Cys-X-Cys,are homologous to those found commonly in several neurotoxicpeptides.     

Photo-responsive block copolymer containing azobenzene group: Synthesis by reversible addition-fragmentation chain transfer polymerization and characterization

The design and synthesis of a new azobenzene-based methacrylate monomer (Azo-IEM) was demonstrated, and its polymerization behavior during reversible addition-fragmentation chain transfer (RAFT) polymerization was investigated. Well-defined homopolymer and amphiphilic block copolymer containing Azo-IEM monomeric units were successfully prepared as evidenced by NMR and GPC analysis. Moreover, the photo-triggered reversible isomerization of polymer products in selected solvents was investigated. Finally, TEM analysis showed that there were significant differences in the nanoparticle morphologies when the block copolymer samples were irradiated with different wavelengths of light (i.e., UV and visible). The size and shapes of the p(HEMA-b-Azo-IEM) polymer capable of transitions upon changes in Vis/UV light exposure which prepared from MeOH/CHCl₃ mixture solvent. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47870.     

The fabrication of graphitic thin films with highly dispersed noble metal nanoparticles by direct carbonization of block copolymer inverse micelle templates

Ordered arrays of Au or Ag nanoparticles supported on two-dimensional graphitic carbon films were prepared by direct carbonization of stabilized asymmetric polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP) inverse micellar films loaded with metal precursors. Crosslinked PS-b-P4VP thin film templates with metal precursors selectively distributed in P4VP domains were converted to carbonaceous thin films having well-defined, highly dispersed metal nanoparticle (NP) arrays by ultraviolet (UV) irradiation under vacuum and subsequent carbonization. Mesoporous carbon films were also obtained after extracting the metal NPs by sonication in selected solvents. PS-b-P4VP was employed not only as carbon source, but also as template for introducing metal NPs in a nanopatterned configuration. The characteristic features and properties of thus generated hybrid carbon nanostructures were investigated by microscopy, UV–visible spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction measurement, and Raman spectroscopy.     

The effect of block lengths on micelle structure in blends of styrene-isoprene diblock copolymer and poly(vinyl methyl ether)

The micellar structure of styrene-isoprene diblock copolymer and poly(vinyl methyl ether) blends was investigated by using small-angle X-ray scattering and transmission electron microscopy techniques. In order to determine the effect of styrene block length on the formation of micellar structure, three sets of diblock copolymers, with near-identical isoprene block molecular weights, but with different styrene block lengths were studied. With modeling based on the polydisperse Percus-Yevick hard sphere fluid model, the structural parameters characterizing the micelles were determined as a function of copolymer concentrations, temperature, and copolymer block lengths. The core radius was found to decrease on increasing the length of styrene block. The degree of swelling of the corona by PVME increased steadily with increasing the styrene block length.     

DPE法合成双亲性丙烯酸酯嵌段共聚物及用于颜料分散剂的研究

以1,1-二苯基乙烯（DPE）为分子量调节剂,偶氮二异丁腈（AIBN）为引发剂进行甲基丙烯酸丁酯（BMA）的可控自由基聚合（DPE法）。研究了溶剂、DPE用量及反应温度对于聚合的影响,得到分子量分布较窄（PDI=1.43）的含有DPE半醌式休眠种结构的聚甲基丙烯酸丁酯（PBMA）。以PBMA为引发剂引发甲基丙烯酸二甲氨基乙酯（DMAEMA）聚合,得到分子量分布较窄的（PDI=2.0）双亲性嵌段共聚物（PBMA-b-PDMAEMA）。核磁共振氢谱（¹H NMR）测得共聚物组成与GPC测试结果相近。差示扫描量热分析（DSC）测试表明嵌段共聚物在11℃和35℃处有两个玻璃化转变温度。色浆的流变和粒径测试及漆膜性能测试表明,将所得双亲性嵌段共聚物作为酞菁蓝颜料分散剂,可以明显提高酞菁蓝颜料在丙烯酸酯树脂中的分散效率。     

坡缕石对苯乙烯-丁二烯-苯乙烯嵌段共聚物改性沥青性能的影响

研究了坡缕石对苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)改性沥青性能的影响.结果表明,坡缕石特殊的层链状结构和大的比表面积不仅改善了SBS改性沥青的低温性能和抗老化性能,同时形成的 .网状结构使SBS改性沥青稳定性增强.     

相转移催化剂对苯乙烯-丁二烯-苯乙烯嵌段共聚物环氧化反应的影响(英文)

研究了三辛基甲基氯化铵(MTAC)、三十二烷基三甲基氯化铵(TMAC)、十六烷基三甲基溴化铵(HTAB)、十八烷基三甲基溴化铵(OTAB)以及聚乙二醇(PEG-400)等5种相转移催化剂对苯乙烯-丁二烯-苯乙烯嵌段共聚物环氧化反应的影响.结果表明,MTAC的环氧化效果最好,当其质量分数为1.0%时,可使环氧化苯乙烯-丁二烯-苯乙烯嵌段共聚物(ESBS)的环氧基质量分数从18.1%提高到20.1%;HTAB和PEG-400有利于ESBS的环氧基质量分数的提高;而OTAB和TMAC由于自身较大的分子体积反而使ESBS的环氧基质量分数下降.傅里叶变换红外光谱分析表明,MTAC可以有效抑制环氧基开环副反应的发生.     

添加剂对镍系催化苯乙烯-丁二烯-苯乙烯嵌段共聚物加氢的影响

考察了镍系催化剂用于苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)加氢时添加剂对加氢反应的影响。结果表明,六甲基磷酰三胺(HMPA)是一种较好的添加剂。催化剂的最佳陈化方式为：于50℃将HMPA加入到环烷酸镍(简称Ni)中,使其充分络合,然后加入三异丁基铝(简称Al)。在65℃。1．96MPa的条件下,当Ni用量为0．001g/g,HMPA/Ni(摩尔比)为1．0,Al/Ni(摩尔比)为6～8时。可制得氢化度大于98％的氢化SBS。     

“Reservoir” and “barrier” effects of ABC block copolymer micelle in hydroxyapatite mineralization control

An amphiphilic triblock poly (ethylene glycol)-block-poly (acrylate acid)-block-poly (ε-caprolactone) (PEG-PAA-PCL) copolymer was synthesized by sequential anionic polymerization. By comparing with diblock copolymer poly (acrylic acid)-block-poly (ε-caprolactone) (PAA-PCL), the triblock copolymer (PEG-PAA-PCL) micelle has core-shell-corona structure, which possesses better dispersion, could be a good candidate as structure template for the controlled mineralization of hydroxyapatite (HA). The interactions between inorganic ions and polymers were studied by using Ca²⁺ ion selective electrode and zeta potential, which indicated the “reservoir” effect of micelles and the “barrier” effect of PEG segments during mineralization process. Ca²⁺ ions can penetrate through the corona and interact with PAA segments. When PO₄³⁻ ions were added, Ca²⁺ ions diffuse out, and react with PO₄³⁻ ions to form the new apatite layer. Thus the supersaturation could be well tuned by the triblock copolymer micelles, and the nucleation and crystal growth in nano scale could be controlled by appropriate usage of this template system.     

Electrokinetic transport of water and methanol in Nafion membranes as observed by NMR spectroscopy

Electrophoretic NMR (eNMR) and pulsed-field-gradient NMR (PFG-NMR) methods were used to study transport processes in situ and in a chemically resolved manner in the electrolyte of an experimental direct methanol fuel cell (DMFC) setup, constituted of several layers of Nafion 117. The measurements were conducted at room temperature for membranes fully swollen by methanol-water mixtures over a wide concentration interval. The experimental setup and the experimental protocol for the eNMR experiments are discussed in detail. The magnitude of the water and methanol self-diffusion coefficients show a good agreement with previously published data while the ratio of the two self-diffusion coefficients may indicate an imperfect mixing of the two solvent molecules. On the molecular level, the drag of water and methanol molecules by protons is roughly of the same magnitude, with the drag of methanol molecules increasing with increasing methanol content. The electro-osmotic drag defined on mass-flow basis increased for methanol from a low level with increasing methanol concentration while that of water remained roughly constant.     

Effect of PEO-PPO-PEO structure on the compressed ethylene-induced reverse micelle formation and water solubilization

Some of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) tri-block copolymers aggregate in p-xylene upon addition of ethylene and form reverse micelles at higher temperature at which the reverse micelles cannot be formed without addition of compressed ethylene. An abrupt increase of water solubilization is observed at a certain ethylene pressure. The effects of surfactant structure, such as the ratio of EO (EO weight percent) and the molecular mass, on the copolymer micellization and the solubilization of water in such systems are studied. For the copolymers with the same length of PO block, higher EO ratios facilitate the reverse micelle formation. However, as the EO ratio reaches 70%, it cannot form reverse micelles because the hydrophilicity is too high. For the copolymers with same composition, higher molecular weight is favorable to forming the reverse micelle due to the hydrophilic and folding effects, respectively. The reverse micelle solution can solubilize water with W₀ (molar ratio of water to EO segment) up to 4.1.     

Flour rice husk as filler in block copolymer polypropylene: Effect of different coupling agents

Flour rice husk (FRH) was employed as a filler in block copolymer polypropylene (PPB) in order to prepare polymer‐based reinforced composites. Four coupling agents were selected to modify the surface of the rice husk in the composite materials, including two types of functionalized polymers [PP homopolymer grafted with maleic anhydride (MA‐PP) and an elastomer styrene–ethylene–butadiene–styrene triblock copolymer grafted with MA (MA‐SEBS)] and two bifunctional organometallic coupling agents (silane and titanate with linear low‐density polyethylene as a carrier). The influence of each type of coupling agent on the interfacial bonding strength was studied by dynamic mechanical analysis, scanning electronic microscopy, and rheological tests. The results showed that strong interactions were formed between the coupling agents and the filler surface. The addition of a coupling agent with an elastomeric carrier (MA‐SEBS) increased the loss tangent and reduced the storage modulus of the composite. A similar but less intense effect was observed for the titanate coupling agent. However, an antagonistic performance was obtained when MA‐PP and silane were employed as coupling agents. In addition, when the percentage of MA‐SEBS was increased, the impact properties of FRH/PPB blends were improved and the strength was reduced. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1823–1831, 2006