NaCl对疏水缔合聚合物溶液性质的影响研究

研究了NaCl对疏水缔合聚合物溶液性质的影响。结果表明,所合成的疏水缔合聚合物的特性粘数随NaCl浓度的增加而降低,其表观粘度则先降低后增加,继续增加NaCl浓度,溶液粘度降低,但仍保持很高的粘度。环境扫描电镜(ESEM)研究表明,疏水缔合聚合物在去离子水体系中会形成网状结构,而在NaCl浓度为5g·L-1的溶液中,ESEM照片显示疏水缔合聚合物的结构为致密的树枝状结构,且存在一临界缔合浓度。     

煤的缔合结构研究 Ⅰ 溶液缔合动力学

研究了煤可溶组分——吡啶不溶物（PI）在溶液中的缔合动力学，该PI系二硫化碳/N-甲基-2-吡咯烷酮（CS2/NMP）混合溶剂可溶组分。结果表明PI在NMP溶液中的缔合属于反应控制机理，并提出了二步动力学反应过程，即基本缔合单元的生成和缔合单元之间的缔合。通过实验获得了有关缔合的动力学参数，PI在NMP溶液中二步缔合的活化能分别为73.3 kJ/mol和21.6 kJ/mol。温度对缔合速率的影响显著，随着温度的升高，缔合速率增加。由于PI分子在CS2/NMP混合溶剂中相对NMP具有较高的扩散性，因而其在CS2/NMP混合溶剂中缔合速率较NMP快。此外，还讨论了PI在溶液中的缔合机理。     

荧光探针法研究疏水改性聚丙烯酰胺溶液的疏水缔合行为

采用胶束共聚 共水解方法合成疏水改性水溶性聚合物聚(丙烯酰胺/丙烯酸钠/N 辛基丙烯酰胺)[P(AM/NaAA/C8AM)],并以芘为荧光探针,应用稳态荧光光谱法研究了它的疏水缔合行为。结果表明,随聚合物浓度、疏水单体摩尔分数、疏水侧链长和温度的增加,疏水缔合作用增强;不同疏水单体含量的P(AM/NaAA/C8AM)的临界缔合浓度为1.5~3.0 g/L;表面活性剂十二烷基硫酸钠(SDS)与P(AM/NaAA/C8AM)发生了强烈的疏水相互作用,形成混合胶束,得到SDS的临界胶束浓度(CMC)为8×10-3 mol/L;由于聚合物链上羧基的存在,使其具有良好的 pH敏感性,随 pH值的增大,P(AM/NaAA/C8AM)的疏水缔合作用呈现先减弱后恒定再增强的变化。     

硼酸盐水溶液热力学研究: 4.离子对[CaB(OH)~4]^+标准缔合 常数的确定

在温度为278.15-318.15K范围内测定了含有不同Li~2B~4O~7和CaCl~2浓度测试液的无液接电池:Pt,H~2(101.325kPa)|Li~2B~4O~7(m~1),CaCl~2(m~2)|AgCl-Ag的电动势E(V)。在Pitzer电解质溶液理论基础上,用线性外推法确定离子对[CaB(OH)~4]^+的标准缔合常数K~d,并得到K~d随温度T变化的经验公式:pK~d=0.6857-359.72/T-4.632×10^-^3T。同时计算得到了离子对缔合过程的热力学函数,指出形成该离子对的推动力是缔合熵。     

中东常压渣油热反应过程中沥青质的缔合性变化规律

用表面张力法研究了中东常压渣油热反应过程中正庚烷沥青质缔合性的变化。测定沥青质的不同浓度甲苯溶液的表面张力,利用溶液的临界胶束浓度表征沥青质的缔合性。定义蒸气压渗透法(VPO法)测得的沥青质平均分子量和表面张力法计算得到的平均分子量之比为沥青质的缔合度参数。结果表明,随着热反应的进行,在生焦诱导期内,沥青质的临界胶束浓度下降、沥青质缔合度参数增大,缔合性增强；达到生焦诱导期后临界胶束浓度上升、缔合度参数下降,缔合性下降。     

DMF-H_2O缔合体系的~1HNMR研究

DMF水溶液是一种生物分子水溶液的简单生化模型。测量了DMF-H_2O体系不同 温度下全浓度范围的~1H NMR数据，对体系中的缔合情况进行了讨论，基于H_2O, H_2O·DMF, (H_2O)_2和(DMF)_2·H_2O的缔合平衡建立了化学缔合模型，采用最 小二乘法拟合实验数据，联合遗传算法和Levenberg-Marquardt算法对模型参数进 行全局寻优求解得不同温度的缔合平衡常数K，再根据不同温度的K求得缔合平衡的 ΔH和ΔS。为了更好地理解DMF水溶液中分子间的相互作用，还测量了298 K下DMF- CCl_4和DMF-BuOH体系全浓度范围的~1H NMR数据作为比较，结合NMR的基本原理对 各DMF溶液体系~1H NMR的实验现象进行了分析和解释，认为水溶液的特殊结构、氢 键和DMF酰胺基的共轭体系是影响DMF-H_2O体系~1H NMR的主要因素。     

煤的缔合结构研究Ⅱ溶液黏度变化

采用Pal-Rhodes方程描述了一种煤可溶组分PI-1溶液黏度随时间的变化关系,并计算得到了缔合物的缔合维数。25 ℃下PI-1在NMP和CS2/NMP混合溶剂中缔合物的缔合维数分别为2.08和2.19,表明其在低温下缔合属于反应控制机理。随着温度的提高,缔合维数趋于减小,表明在较高温度下,PI-1具有较快的缔合动力学过程,在50 ℃时PI-1在NMP中的缔合维数大于在CS2/NMP混合溶剂中的缔合维数,表明PI-1在NMP的缔合速率相对低于CS2/NMP混合溶剂。     

四丁基氟化铵在H2O-DMF中的电导研究

测量了298.15~328.15 K温度范围内四丁基氟化铵在20(wt)%~80(wt)%H2O/DMF混合溶液中的电导率,测得的电导率分别通过Kray-Bray方程和Shedlovsky方程分析,推导出了四丁基氟化铵在H2O-DMF混合溶液中的摩尔极限电导、缔合常数和离解常数,并计算出缔合反应的热力学参数(△Ga,△Ha,△Sa);同时探讨了温度和混合溶剂的组成对摩尔极限电导、缔合常数和热力学参数的影响。     

疏水缔合效应对聚丙烯酰胺类水溶液结构和流变性质的影响

以聚合物驱油为背景,研究了部分水解聚丙烯酰胺(HPAM)和缔合型部分水解聚丙烯酰胺(AHPAM)水溶液的结构与流变性质的差别.通过粘度法和静态激光光散射法得到了所分析的聚丙烯酰胺的分子量,用动态激光光散射法和粘度法分析了特定AHPAM分子缔合形态,并用流变学法测定了AHPAM在地层温度与矿化度条件下的线性粘弹性与非线性流变特性.着重讨论了临界缔合浓度的概念,研究了结构和流变性质的关系,以及分析了缔合对聚合物驱油的可能影响.实验结果表明,AHPAM水溶液在宽浓度范围存在分子缔合;一般临界缔合浓度的概念实际反映在进入亚浓溶液范围分子间缔合的效应,剪切速率约为10 s-1时,剪切粘度突降数倍,反映缔合结构在剪切场中的变化,该现象在高缠结浓度下较不明显;拉伸粘度随拉伸速率变化与HPAM定性不同,该拉伸特性反映了疏水缔合近程作用的本质.     

一种水溶性疏水缔合聚合物二临界缔合行为研究

对三元共聚疏水缔合聚合物（丙烯酰胺／十八烷基二甲基烯丙基氯化铵／苯乙烯）的临界缔合浓度进行研究,发现其具有二临界缔合现象以及其在二临界缔合浓度附近不同的耐温抗盐的流变行为。研究结果表明,该疏水缔合聚合物的第一临界缔合浓度（C1^＊）为500mg／L,第二临界缔合浓度（C2^＊）为2400mg／L;C2^＊附近聚合物溶液的耐温性能较差;抗盐性能表现出三种不同的情况：随着盐质量浓度的增加,C〈C1^＊时,溶液粘度下降;C1^＊〈C〈C2^＊时,溶液粘度先增加后下降;C〉C2^＊时,溶液粘度先快速增加,后缓慢增加,最后下降。     

增溶甲苯对聚氧乙烯-聚氧丙烯嵌段共聚物胶团的影响

用动态光散射, 测定聚氧乙烯-聚氧丙烯嵌段共聚物水溶液胶团增溶不同量的甲苯后, 其平均流体力学半径R_h的变化, 以及温度对它们的影响。实验结果表明, 25 ℃时胶团水化度高, R_h数值大, 增溶不同量的甲苯对R_h的影响较小。温度升高,胶团的水化度降低, R_h变小, 当温度接近浊点, 水化作用降至最低。因温度升高引起的胶团聚集数增加以及增溶的甲苯进入胶团内部的胀大作用, 使R_h随增溶量增加近于线性的上升。     

Influence of microwave radiation on the growth of gold nanoparticles and microporous zincophosphates in a reverse micellar system

The water core of reverse micelles has been extensively used as the site for synthesis of a variety of materials. However, water-in-oil reverse micelles have a limited range of temperatures over which they are stable as a single phase. Directing heat to the water cores, the usual site of synthesis without heating the bulk provides added opportunities for synthesis. Microwave radiation is a method for superheating the water cores. In this study, we use an H2O-sodium bis(2-ethylhexyl) sulfosuccinate (AOT)-heptane reverse micelle system for the synthesis of Au particles by hydrazine reduction of HAuCl4 in the presence and absence of microwave radiation. The duration of the microwave radiation was limited to a 2-min duration at a power of 300 W, thereby ensuring that the reverse micelle phase is maintained during the synthesis. At all hydrazine concentrations studied (0.5-2 M), the presence of microwave radiation led to an increase in the particle size of Au. The second system examined was the growth of microporous zincophosphate-X (ZnPO-X, an analogue of the faujasite structure) synthesized from H2O-dioctyldimethylammonium chloride (DODMAC)-heptane reverse micelle system. Microwave radiation was applied for 1 min at 150 W at various stages of the nucleation and growth process, and did not disrupt the reverse micelle system. Product analysis after 48 h of reaction showed that the 1-min microwave pulse, if applied during the nucleation stage (the first 4 h), promoted the formation of NaZnPO4.H2O over ZnPO-X. The effect of the microwave pulse at the growth stage was to promote the formation of ZnPO-X. Absorption of the microwave radiation by the water core and surrounding polar surfactant molecules leads to a rapid rise in local temperature (predicted to be approximately 150 degrees C/min for the AOT system), increasing the rates of intramicellar reactions.     

A structural development of an organogel explored by synchrotron time-resolved small-angle X-ray scattering

We investigated the gelation process of 12-hydroxystearic acid (12-HSA)/dodecane gel (turbid gel), 12-HSA/xylene and 12-HSA/toluene gels (transparent gels) by using time-resolved synchrotron small-angle X-ray scattering technique. The fibers were developed via nucleation and growth mechanism, and the induction period was longer at higher temperatures. After the induction period, the fiber growth can be divided into two regimes. In the first stage, the scattering intensity increased with time without appearance of any crystalline peak, and in the second stage (001) peak appeared due to crystalline nucleation. In the former regime, the fibers grew with increasing the cross-sectional size, while in the latter regime, they grew with keeping it almost constant, i.e., with keeping the fiber thickness constant. The fiber thickness for the turbid gel (radius of the gyration R _c of ～100 Å) was thicker than that for the transparent gel (R _c of ～82 Å). The fractal dimensions of the fibrillar aggregates for the turbid gels (2.0–2.3) at various temperatures were larger than those for the transparent gels (1.4–1.6), suggesting that the structure of the former gels is more branching or more compact in comparison with the latter.     

聚甲基丙烯酸甲酯接枝聚氧乙烯在甲苯中的聚集态结构

两亲接枝共聚物;胶束;聚甲基丙烯酸甲酯接枝聚氧乙烯在甲苯中的聚集态结构     

Particle Nucleation and Growth in the Emulsion Polymerization of Styrene: Effect of Monomer/Water Ratio and Electrolyte Concentration

This work is an extension of previous research results reported by our team (Colloid and Polymer Science 2013, 291: 2385-2398), where large scale and high solid content latexes of poly(n-butyl acrylate) were obtained with the particle coagulation method induced by the electrolyte. However, how to prepare controlled particle size distribution polymer latex has not been studied. Thus, in this study, the effect of the monomer/water ratios and electrolyte concentrations on particle formation and growth methods were studied by following the tracks of the evolutions of particle size, number and distribution as a function of reaction time or conversion. Experimental results showed that the length of time that particle nucleation occurred increased with increasing monomer charged for the systems without electrolyte. A point worthy of attention here is that homogeneous nucleation may occur at high monomer concentrations (30/70, 40/60). However, electrolyte added could be made the nucleation mechanism shift from micellar/homogeneous nucleation to micelle /coagulation nucleation. As a result, the final particle size distribution can be controlled by adding an appropriate electrolyte to regulate the nucleation mechanism. Spherical and uniformly sized particles could be obtained when electrolyte concentration is between 0.2 wt% and 0.4 wt% for water at the high monomer/water ratio (40/60). The effects of electrolyte concentration on nucleation mechanism mainly were expressed by decreasing the solubility of the monomer and interparticle potential, and then preventing homogeneous nucleation and enhancing particle coagulation.     

Interactions between cationic starch and anionic surfactants

The surface tensions and the phase equilibria of dilute aqueous cationic starch (CS)/surfactant systems were investigated. The degree of substitution of the CS varied from 0.014 to 0.772. The surfactants investigated were sodium dodecyl sulphate (SDS), potassium octanoate (KOct), potassium dodecanoate (KDod) and sodium oleate (NaOl). The concentrations of CS were 0.001, 0.01 and 0.1 w%.Critical association concentrations (cac) occur at surfactant concentrations well below the critical micelle concentrations of the surfactants, except for KOct, KDod and NaOl at the lowest CS concentrations investigated (0.001 w%). The surface tensions of CS/surfactant solutions decrease strongly already below the cac. This is attributed to the formation of surface active associates by ion condensation. Associative phase separation of gels formed by CS and surfactant takes place at extremely low concentrations when the surfactant/polymer charge ratio is somewhat larger than 1. The gel is higly viscous and contains 40–60% water, depending on the concentration of electrolyte, the surfactant hydrocarbon chain length and the nature of the polar head of the surfactant.The concentration at which the phase separation occurs decreases with increasing surfactant chain length and the concentration of simple electrolyte, factors that promote micelle formation. This indicates that the gels are formed by association of CS to surfactant micelles. When surfactant well in excess of charge equivalence is added, the gels dissolve because the CS/surfactant complexes acquire a high charge.     

PSt-g-PEO两亲接枝共聚物溶液的性质

两亲共聚物是指分子结构中同时具有对两种相结构都有亲和性的聚合物,一般指分子结构中同时含有亲油和亲水基团的共聚物,研究两亲共聚物在选择性溶剂中的形态及聚集态结构,对于其作为表面活性剂,增溶剂,生物医药材料,以及固体微胶束的研究都具有重要的理论和实际意义。[1-3]／     

High-Q ultrasonic determination of the critical nanoaggregate concentration of asphaltenes and the critical micelle concentration of standard surfactants

Asphaltenes are known to be interfacially active in many circumstances such as at toluene-water interfaces. Furthermore, the term micelle has been used to describe the primary aggregation of asphaltenes in good solvents such as toluene. Nevertheless, there has been significant uncertainty regarding the critical micelle concentration (CMC) of asphaltenes and even whether the micelle concept is appropriate for asphaltenes. To avoid semantic debates we introduce the terminology critical nanoaggregate concentration (CNAC) for asphaltenes. In this report, we investigate asphaltenes and standard surfactants using high-Q, ultrasonic spectroscopy in both aqueous and organic solvents. As expected, standard surfactants are shown to exhibit a sharp break in sonic velocity versus concentration at known CMCs. To prove our methods, we measured known surfactants with CMCs in the range from 0.010 g/L to 2.3 g/L in agreement with the literature. Using density determinations, we obtain micelle compressibilities consistent with previous literature reports. Asphaltenes are also shown to exhibit behavior similar to that of ultrasonic velocity versus concentration as standard surfactants; asphaltene CNACs in toluene occur at roughly 0.1 g/L, although the exact concentration depends on the specific (crude oil) asphaltene. Furthermore, using asphaltene solution densities, we show that asphaltene nanoaggregate compressibilities are similar to micellar compressibilities obtained with standard nonionic surfactants in toluene. These results strongly support the contention that asphaltenes in toluene can be treated roughly within the micelle framework, although asphaltenes may exhibit small levels of aggregation (dimers, etc.) below their CNAC. Furthermore, our extensive results on known surfactants agree with the literature while the asphaltene CNACs reported here are one to two orders of magnitude lower than most previously published results. (Previous work utilized the terminology "micelle" and "CMC" for asphaltenes.) We believe that the previously reported high concentrations for asphaltene CMCs do not correspond to primary aggregation; perhaps they refer to higher levels of aggregation or perhaps to a particular surface structure.     

Deposition of small organic molecules by the displacement of two immiscible supercritical phases

A new coating process is described (deposition from two immiscible supercritical phases, or DISP) in which a solution of supercritical carbon dioxide (scCO2) with a desired solute is displaced by supercritical helium (scHe). After depressurization, the solute is deposited on substrates initially submerged in the coating solvent. Micron-sized particles and thin films of sucrose octaacetate (SOA) were formed on silicon wafer substrate coupons from DISP at relatively low temperatures and pressures (< or = 6500 psi and < or = 60 degrees C). The particle size, film thickness, and morphology of SOA were characterized as a function of coating conditions-solution concentrations, withdrawal velocities, and pressures. Particles in the range of 1-14 microm in diameter were deposited at low solute concentrations (< or = 0.2 wt % at 4500 psi), whereas films in the range of 0.1-0.5 microm in thickness were deposited at higher solute concentrations (> or = 1.5 wt % at 4500 psi). Particle sizes decreased with increasing displacement velocity and increasing pressure. Estimates of characteristic times for diffusion and nucleation indicate that DISP is a diffusion-limited process. Optical microscopy and atomic force microscopy (AFM) were used to characterize film morphology, including defect formations and film roughness. Highly uniform films with low root-mean-square (RMS) roughness (approximately 10 angstroms) were obtained at a low displacement velocity of 0.0035 cm/s, while ring-like defect structures were observed in films deposited at a higher displacement velocity of 0.035 cm/s. The film thickness and morphology of the films deposited from DISP were compared with films from normal dip coating with typical organic solvents (acetone and toluene). Films deposited from scCO2 by DISP were much thicker, more uniform, and exhibited much fewer drying defects and lower RMS roughness compared with films from the organic solvents.