PNI PAM/CS微凝胶的性质测定

以N-异丙基丙烯酰胺(NIPAM)、壳聚糖(CS)为单体,N,N-亚甲基双丙烯酰胺(MBA)为交联剂,制备了PNIPAM/CS微凝胶.测定了不同单体配比对微凝胶体积相转变温度(VPTT)的影响和25℃不同pH条件下微凝胶液浊度及粒径的变化.研究表明,PNIPAM/CS微凝胶具有温敏性;并且随着pH的增大,微凝胶粒径先变小后变大,显示pH敏感性;浊度法测定结果与粒径测定一致.     

PAMPS/SiO_2杂化水凝胶的合成及电场敏感性研究

以2-丙烯酰胺-2-甲基丙磺酸(AMPS)为有机原料,正硅酸乙酯(TEOS)为无机原料,过硫酸钾为引发剂,N,N'-亚甲基双丙烯酰胺为交联剂,通过原位-凝胶水溶液聚合法合成了一系列不同二氧化硅含量和不同聚离子浓度的聚(2-丙烯酰胺-2-甲基丙磺酸)/二氧化硅杂化电场敏感性水凝胶.通过扫描电子显微镜(SEM)表征凝胶的结构,研究水凝胶在去离子水以及氯化钠溶液中的溶胀和消溶胀行为.结果表明,系列凝胶的平衡溶胀度介于224.9至325.6之间,复合凝胶的溶胀速率随TEOS用量的增加而降低;除理想杂化凝胶外,随着聚离子浓度的升高,凝胶在氯化钠溶液中的消溶胀速率逐渐减小.对凝胶的电场敏感性研究表明,当聚离子浓度大于氯化钠溶液浓度时,凝胶进一步溶胀,反之则消溶胀,其中杂化凝胶的再溶胀性能减弱,而消溶胀行为变得更为明显.同时制得的理想杂化凝胶,较纯有机凝胶具有更为理想的力学性能,最大抗压缩强度可达23.4 MPa.     

P(MAA-co-AM)纳米水凝胶的制备与表征

利用单体对之间的氢键特殊相互作用,采用一步反应在水相中共聚甲基丙烯酸(MAA)、丙烯酰胺(AM)和交联剂乙二醇二甲基丙烯酸酯(EGDMA),制备了pH响应性共聚物P(MAAco-AM)纳米水凝胶。采用纳米粒度与电位分析仪、傅里叶红外光谱仪、透射电子显微镜、场发射扫描电镜等对P(MAA-co-AM)纳米水凝胶的尺寸、形貌、组成和结构进行了表征。系统研究了反应参数对P(MAA-co-AM)纳米水凝胶的影响。结果表明:当两单体等物质的量投料时所制备的P(MAA-co-AM)纳米水凝胶粒径分布最窄(〈Dh〉=129nm,PDI=0.095),且其粒径随着两单体用量的增加而增大。随着单体加入时间的延长或EGDMA用量的增加,P(MAA-co-AM)纳米水凝胶的粒径逐渐变小。P(MAA-co-AM)纳米水凝胶表现出极好的pH响应性:当介质的pH从4增加到8时,溶胀比高达7,体积扩张了343倍。     

甲基丙烯酸/丙烯酰胺双单体共聚反蛋白石光子晶体的制备

以烧结后的二氧化硅光子晶体为模板,采用溶胶凝胶法向模板间隙填充以甲基丙烯酸(MAA)和丙烯酰胺(AM)为双功能单体,N,N’-亚甲基双丙烯酰胺(BIS)为交联剂的聚合物前驱液,制备了甲基丙烯酸/丙烯酰胺共聚(PMAM)双单体反蛋白石凝胶光子晶体.通过紫外可见光谱分析表明,反蛋白石结构的凝胶膜对pH响应范围在4.0～7.0之间.由于其不受离子强度的影响,除了可以作为pH传感器外,还可以作为金属离子及生物小分子等分子印迹光子晶体传感器的基体膜.     

反相微乳液聚合法制备聚(丙烯酰胺-co-丙烯酸)pH敏感微凝胶及其性能

以丙烯酰胺(AM)和丙烯酸(AA)单体的水溶液为分散相,失水山梨醇单油酸脂(Span80)/聚氧乙烯失水山梨醇脂肪酸脂(Tween80)/异辛烷为分散介质,分别以N,N′-亚甲基双丙烯酰胺(MBA)、过硫酸铵/亚硫酸氢钠((NH4)2S2O8/NaHSO3)为交联剂和氧化还原引发剂,在30℃进行反相微乳液聚合制备了一系列不同单体摩尔百分数的P(AM-co-AA)微凝胶.通过傅立叶红外光谱、浊度法、透射电镜(TEM)和动态光散射(DLS)等测试手段分别对微凝胶特征官能团的存在、pH敏感性、微观形态、粒径大小及粒径分布等进行表征分析.结果表明,共聚物中存在AM和AA结构单元;样品的TEM照片显示在原料中AA的摩尔百分数为60%时,P(AM-co-AA)微凝胶粒子的数均粒径为90 nm左右,呈现非规则球形;DLS结果表明,P(AM-co-AA)微凝胶与PAM微凝胶相比具有较宽的粒径分布,且随原料中AA摩尔百分数增加,粒径分布逐渐变宽;P(AM-co-AA)微凝胶具有良好的pH敏感性,敏感pH值与AA的解离常数有关,通过调节pH值可以迅速控制自身体积的溶胀与收缩.     

粒径可控的纳米铁酸铋的制备及其光催化性能

采用改进的聚丙烯酰胺凝胶法制备了BiFeO3纳米颗粒,利用热重-差热、红外光谱及X射线衍射等手段研究了干凝胶的热分解及BiFeO3的成相过程.结果表明,在600℃煅烧可制备出高纯的BiFeO3纳米颗粒.同时发现,随着双丙烯酰胺含量的增加,所得样品晶粒尺寸逐渐减小,从而制备出平均粒径约52～110nm的系列BiFeO3颗...     

以环糊精准聚轮烷为“假载体”印迹识别蛋白质的研究

实验以聚乙烯醇分子为客体分子,与γ-环糊精(γ-CD)分子组装制备环糊精准聚轮烷(CD-PPRs);在金属离子存在下,以丙烯酰胺(AM)为单体,N,N-亚甲基双丙烯酰胺为交联剂,以CD-PPRs为"假载体",制备了以牛血清白蛋白(BSA)为模板的分子印迹聚合物(cp-MIP)。结果表明,随着功能基化CD-PPRs(CD-PPRsAc)用量增加,印迹聚合物吸附量先增加后减小,当CD-PPRs-Ac与AM的质量比为0.55时,印迹聚合物的吸附量最大;在Cu2+共存时,吸附量最高可达5.16 mg/g;将cp-MIP用于4种混合蛋白溶液吸附,结果表明,引入CD-PPRs使印迹聚合物的特异性吸附能力明显提高,特异性吸附量可提高约6倍。     

P(AMPS-co-BMA)水凝胶的电场敏感性及电刺激响应机理

以离子型单体2-丙烯酰胺-2-甲基丙磺酸(AMPS)及非离子型单体甲基丙烯酸丁酯为原料, 偶氮二异丁腈为引发剂, N,N′-亚甲基双丙烯酰胺为交联剂, N,N-二甲基甲酰胺为溶剂, 通过自由基聚合合成了一系列聚离子浓度不同的聚(2-丙烯酰胺-2-甲基丙磺酸-co-甲基丙烯酸丁酯)电场敏感性水凝胶. 研究了其在去离子水及NaCl溶液中的溶胀行为. 结果表明, 该水凝胶在去离子水中的平衡溶胀度在236.4~298.5之间, 其溶胀速率随着AMPS用量的增加而增加; 并且随着凝胶内部聚离子浓度的增加, 凝胶在NaCl溶液中的消溶胀速率及消溶胀度逐渐减小. 凝胶的电刺激响应性能研究结果表明, 在电场存在下, 凝胶在NaCl溶液中的溶胀行为与凝胶内部聚离子浓度和溶液中NaCl浓度的相对大小有关, 当凝胶内部聚离子浓度大于溶液中NaCl浓度时, 凝胶溶胀, 反之则凝胶消溶胀; 而且, 凝胶在电场作用下的偏转行为同样与凝胶内部聚离子浓度和溶液中NaCl浓度的相对大小有关, 当凝胶内部聚离子浓度大于溶液中NaCl浓度时, 偏向阴极, 反之则凝胶偏向阳极. 另外, 在电场存在下, 凝胶在NaCl溶液中的电偏转速度与环境温度密切相关.     

聚N-异丙基丙烯酰胺/纳米SiO_2复合水凝胶的合成及溶胀性能

通过纳米SiO2的表面功能化,在其表面引入乙烯基功能基团,在H2OTHF的混合溶剂中,超声分散后,交联剂N,N′亚甲基双丙烯酰胺存在时,于25℃下使其与N异丙基丙烯酰胺共聚,制得聚N异丙基丙烯酰胺纳米SiO2复合水凝胶,并用FTIR和SEM对产物进行了表征.研究了凝胶的溶胀动力学,消溶胀动力学和温度敏感性.实验结果表明,纳米SiO2的引入,改善了聚N异丙基丙烯酰胺水凝胶在低温时的溶胀性能和在高温时对水的释放性能,并讨论了引起这些性能改变的原因.     

基于葫芦[10]脲的超分子水凝胶的制备及其在H2O2检测中的应用研究

以丙烯酰胺(AM)与客体单元二茂铁衍生物(G)在引发剂作用下共聚形成P(AM-G)聚合物.基于客体分子与主体分子葫芦[10]脲之间的动态主-客体相互作用为交联点制备了超分子水凝胶.采用核磁、扫描电镜及流变等测试方法对水凝胶的结构、形貌以及自修复性能等进行研究.结果表明超分子水凝胶为3D多孔结构的弹性体,CB[10]的引入有利于在聚合物网络中提供交联点,并且本研究中的超分子水凝胶可在没有任何外部刺激的情况下进行自修复.在水凝胶制备后,二茂铁的固有催化活性仍然得以保留,其良好的催化活性可应用于H_2O_2的检测,检测限为2.5×10~(-4) mol/L.本研究为超分子水凝胶功能化提供了一种新的方法,在生物技术和环境化学等领域具有潜在应用.     

Absorption and fluorescence of a nonionic detergent in aqueous solution

The absorption and fluorescence spectra of a detergent, polyoxyethylene octylphenyl ether, were measured in water at different concentrations. The absorption spectra had a peak at 275 mμ and a shoulder at 281 mμ. The spectra were independent of concentration below the critical micelle concentration, but the molar extinction coefficients of the peak and the shoulder increased with concentration above the critical micelle concentration. The critical micelle concentration value derived from the absorption data was in good agreement with those obtained by other methods. The fluorescence spectra of the detergent in water were independent of concentration in dilute solutions, if the intensities of the spectra were normalized at the peak at 302 mμ. At higher concentrations, a weak excimer band appeared at 345 mμ, whose intensity increased with concentration. The excimer band manifested itself at a concentration slightly lower than the critical micelle concentration. The main band decreased and the excimer band increased, as the temperature was raised. An excimer band was observed in the same region of the spectra for the pure detergent, either in the solid or liquid state. The equilibrium solid spectra exhibited a very strong excimer emission. It was concluded that the excimers were formed within micelles in the case of aqueous solutions.     

芳基油酸酰胺羟丙基磺基甜菜碱的合成及性能

合成了3种具有不同疏水基团的新型磺基甜菜碱两性表面活性剂,通过红外光谱对它们的结构进行了表征。 用滴体积法测定表面活性剂水溶液在25 ℃下的表面张力,从而确定其临界胶束浓度(cmc)及临界胶束浓度下的表面张力(γcmc);采用罗氏泡沫仪考察了浓度、温度对其泡沫性能的影响;采用分水时间法考察了其乳化性能。 结果表明,随着芳环在烷基链中的体积增大,cmc以及γcmc增大,饱和吸附面积Amin增大,而饱和吸附量Γmax减小。 3种表面活性剂的起泡性随浓度增大而增加,到一定值后趋于稳定;泡沫稳定性随浓度增大逐渐增强;起泡性随着温度的升高而显著增加,泡沫稳定性随温度升高而显著降低。 3种表面活性剂的乳化能力随浓度增大而逐渐增强然后趋于稳定。     

Investigation of the mechanism of formation of chlorine atoms in chlorine-hydrogen plasmas

To explain the trend of an experimental dependence for concentration of chlorine atoms in a discharge, the principal processes of the formation and decay in the plasma of a chlorine mixture with hydrogen were considered. The rate coefficients and rates of processes involving electrons were calculated by mathematical modeling in order to reveal the contribution of each process to the observed concentration of chlorine atoms. The greatest contribution is made by direct electron-impact dissociation. The experimental concentration of chlorine atoms at a high percentage of hydrogen is explained by an increase in electron concentration and, hence, in the rate of the direct dissociation process. It is suggested that chain reactions can make a substantial contribution to the formation of atoms at low hydrogen concentrations.     

Effect of temperature on the adsorption behavior of tryptophan in reversed-phase liquid chromatography

Single-component adsorption isotherm data of l-tryptophan on a C(18)-bonded silica column were acquired by frontal analysis (FA), with aqueous mobile phases containing 5% of acetonitrile at five different temperatures between 23 and 62 degrees C. The non-linear fitting of these data provided the bi-Moreau model for all temperatures as the best isotherm model. The inverse method (IM) was used to derive the parameters at these temperatures from the parameters of the 25 degrees C isotherm. The adsorption constants and the saturation capacities of the low and high-energy sites decreases by increasing the temperature, while the adsorbate-adsorbate parameters of both sites increase. An excellent agreement was found between the experimental and calculated overloaded band profiles at all the temperatures used. The breakthrough curves obtained and the overloaded band profiles obtained were found to have different shapes according to the range of concentration studied and the temperatures. At low concentration 0.05-0.5 g/L the breakthrough curves and the overloaded band profiles have a front shock and diffuse rear, which indicates langmuirian behavior, but at intermediate 1-2 g/L and high concentration 8 g/L they start to have diffuse fronts and shocks at the rear or more than one shock at the rear which indicates non-langmuirian behavior. At 23 degrees C the isotherm has another langmuirian part, which appears at high concentration. The behavior of the breakthrough curves is explained by the shape of the isotherm in which all of the isotherms have a langmuirian part (the isotherm is concave upward) and an antilangmuirian part (the isotherm is concave downward). The temperature affected the breakthrough curves by decreasing the time of the appearance of the fronts for all concentration ranges studied, and by decreasing the time difference between the highest concentration and lowest concentration of the fronts, especially the low concentration range at 0.5 g/L. The fronts of the breakthrough curves at high concentration seems to be the most affected by temperature.     

Adsorption of cetyltrimethylammonium bromide and propanol mixtures with regard to wettability of polytetrafluoroethylene. I. Adsorption at aqueous solution-air interface

Measurements of surface tension of aqueous solutions of cetyltrimethylammonium bromide (CTAB) and propanol mixtures (gamma(L)) for 1 x1 0(-5), 1 x 10(-4), 6 x 10(-4), and 1 x 10(-3) M concentrations of CTAB as a function of propanol concentration in the range from 0 to 6.67 M at 293 K were carried out. The obtained results indicate that there is first-order exponential relationship between the surface tension and propanol concentration in the solution at constant CTAB concentration. These results were compared with those calculated from the equations derived by von Szyszkowski, Joos, Miller et al. From the comparison it resulted that the values of gamma(L) determined by the Szyszkowski equation are correlated with those measured only in a limited propanol concentration range because of changes of the constant related to the specific capillary activity in this equation as a function of propanol concentration, particularly in the range of its high concentration. In the case of the modified Joos equation there is a correlation between the calculated and measured values of gamma(L) only at a very low concentration of propanol. The values of the surface tension of aqueous solutions of CTAB and propanol mixtures determined by the relationships of Miller et al. at CTAB concentration, corresponding to unsaturated surface layer in the absence of propanol, are close to those measured, but there are bigger differences between the calculated and measured values of the surface tension for solutions at a constant value of CTAB concentration close to CMC. However, the values of the surface tension of aqueous solution of CTAB and propanol mixtures calculated from the modified Miller et al. equation, in which the aggregation process of alcohol molecules at water-air interface was taken into account, are in excellent agreement with those measured. The measured values of the surface tension and the Gibbs equations were used for determination of the surface excess of CTAB and propanol concentration at solution-air interface. The obtained results indicate that at the constant concentration of CTAB equal to 1 x 10(-5) and 1 x 10(-4) M there is a maximum of excess concentration of propanol in the surface region at its bulk concentration close to 1 M. Using the calculated values of the surface excess concentration of propanol and CTAB at solution-air interface and assuming the proper thickness of the interface region, the total values of their concentration in this region were evaluated. Next, the standard surface free energy of CTAB and propanol mixtures adsorption was calculated. The calculated values of this energy indicate that the tendency to adsorb molecules of CTAB and propanol decreases with increasing propanol concentration probably because of entropy of adsorption decrease resulting from water structure destruction by propanol molecules.     

High pressure raman study of isotropic lineshapes of aqueous sodium nitrate solutions

The isotropic lineshape of the v₁ (A₁) stretching mode of the nitrate ion in solutions of sodium nitrate has been studied at 25°C as a function of NaNO₃ concentration ranging from 0.1 to 6M. The pressure dependence has been determined for 1 and 6M solutions at pressures ranging from 1 bar to 3 kbar. The isotropic band becomes more asymmetric with increasing concentration, and its v₁ peak frequency undergoes a blue shift both with increased concentration and increased pressure. At low concentration the vibrational correlation function is well described by the Kubo formula, whereas at higher concentration it becomes more Gaussian. The experimental data indicate that the v₁ vibrational lineshape in aqueous solutions of NaNO₃ is dominated by strong intermolecular interactions which produce inhomogeneous broadening at higher concentration.     

Application of constant rate thermal analysis (CRTA) to the synthesis of silicon nitride by carbothermal reduction of silica

The carbothermal reduction of silica under flowing nitrogen at a pressure of 1 atm has been followed by means of a CO IR detector attached to the gas output of a high temperature tubular furnace. The control of the reaction temperature is carried out by interfacing the analogical output of the IR detector to a controller that allows to monitor the sample temperature in such a way that the concentration of CO generated in the reaction is maintained constant at a value previously selected by the user. The reaction rate at a particular concentration of CO can be fixed by properly selecting the flow rate of the reactive gas. The influence of the reaction rate and the CO concentration on both the reaction temperature and the structure of the final product of the reaction are analysed.     

Effect of cationic surfactants on enhancement of firefly bioluminescence in the presence of liposomes

Firefly bioluminescence (BL) was greatly affected by cationic surfactants coexisting with liposomes containing phosphatidylcholine and cholesterol. In this study, the effects of the type and concentration of cationic surfactants on BL were studied in the presence of the liposomes. Three types of cationic surfactant: benzalkonium chloride (BAC), n-dodecyltrimethylammonium bromide (DTAB), and benzethonium chloride (BZC), were used. As a common effect in these surfactants, BL intensity was increased and then drastically decreased with increasing surfactant concentration. This can be explained by the formation of cationic liposomes as BL enhancers at low concentration of the surfactant, and by the transformation into cationic (mixed) micelles as inhibitors at high concentration. The maximal BL intensity and the concentration for the maximal BL were dependent on the type of the surfactants. To explain the differences in these parameters in the enhanced BL, we determined the distribution coefficient, K, of the surfactants to the liposomal membrane. The result indicated that the surfactant with higher K value gives the maximal BL intensity at lower concentration.     

The Effect of Alcohol Solvents on the Porosity and Phase Composition of Titania

Bimodally porous titania powders were made by hydrolysis of titanium tetraisopropoxide (TTIP) dissolved in various alcohols (methanol, ethanol, isopropanol, and sec-butanol). The specific surface area (SSA) of the powders dried at 150 degrees C ranged from 332 to 624 m(2)/g as determined by nitrogen adsorption. At excess alcohol concentration, the SSA of the dried powders decreased in the order of sec-butanol, iso-propanol, ethanol, and methanol at a constant alcohol/TTIP molar ratio. The pore size distribution was bimodal with fine intraparticle pore diameters at 1-6 nm and larger interparticle pore diameters at 30-120 nm as determined by nitrogen adsorption isotherms. The average intraparticle pore diameter decreased with increasing alcohol concentration for methanol and ethanol, while it was rather constant at 3.3 nm, irrespective of alcohol concentration for iso-propanol and sec-butanol. The evolution of particle phase composition was determined by X-ray diffraction ranging from amorphous to crystalline anatase and rutile largely proportional to the calcination temperature and to a lesser extent on the type and concentration of alcohols. Copyright 2000 Academic Press.     

Influence of molecular characteristics of nonionic cellulose ethers on their interaction with ionic surfactant investigated by conductometry

The interaction between nonionic derivatives of cellulose, hydroxypropylmethyl cellulose (HPMC) and methyl cellulose (MC), and ionic surfactant, sodium dodecylsulfate (SDS) were investigated by conductometric titration method, at 30°C. Obtained titration curves show two break points: critical aggregation concentration (cac) defined as the concentration of SDS at which interaction starts, and polymer saturation concentration (psp) as the concentration at which interaction finishes. Changes of characteristic concentration breaks were determined in dependence on concentration and molecular characteristics of cellulose derivatives (degree of substitution (DS) and molecular mass, i.e. intrinsic viscosity). It was shown that the first break point, cac, is independent of polymer concentration; while the second break point, psp, increases as polymer concentration increases, as described by a linear correlation. The slopes of linear relationship justify the DS on the intensity of the cellulose derivatives–SDS interaction. Changes in the intrinsic viscosity of cellulose derivatives do not exhibit influence on the interaction with SDS.