磺化聚苯乙烯镧离子型聚合物的稀溶液性质

聚电解质行为;比浓粘度;电解质;磺化聚苯乙烯镧离子型聚合物的稀溶液性质     

磺化SIS及其离聚物的稀溶液性质

嵌段共聚物;比浓粘度;特性粘液;磺化SIS及其离聚物的稀溶液性质     

关于高分子极稀溶液粘度测定问题的探讨

对聚苯乙烯(PS)／甲苯稀及极稀溶液的粘度用常规的乌氏粘度法进行了测定．发现高分子在毛细管壁上无稳固吸附．在极稀浓度区，粘数(ηsp/c)值波动较大，在时间测量精度不变的条件下，粘数测量误差与浓度成反比，以致ηsp／c-c曲线的线性及重现性变差，并推导出了粘数测量误差与浓度及时间测量误差间的关系式．在此基础上，讨论了确定浓度测量下限的原则及计算公式，认为常规的乌氏粘度测定方法对极稀溶液的应用值得商榷．     

一种统一处理稀溶液的温度、压力和浓度关系的方法

运用Gibbs-Duhem方程统一处理稀溶液与纯溶剂的气态、液态和固态平衡时的温度、压力和浓度相互之间的关系,由此不仅能直接导出稀溶液的依数性质,而且能给出用于研究沸点上升和凝固点下降的模型中稀溶液的压力与温度、压力与浓度的关系以及渗透压模型中的温度与渗透压、温度与溶液浓度的关系。     

离分子混合物溶液在极稀浓度区的粘度异常行为

上世纪50年代初人们就发现,高分子溶液的粘度在极稀浓度区往往表现出异常行为,即当浓度低于某一特定值后,比浓增比粘度浓度图偏离预计的线性关系,出现上弯或下弯的曲线.几十年来人们对此现象展开了大量研究,提出了一些互不协同的解释[1,2].最近,程时等[3,4]对该问题作了系统深入的研究,指出这种粘度异常是源于粘度测量中高分子溶液与毛细管内壁间的界面作用,并给出了消除界面作用干扰的理论改正公式.至此,单一高分子溶液粘度的异常问题得到了明确的解释.但是,关于高分子混合物在极稀浓度区的粘度行为的研究就比较稀少.80年代Ｄｏｎｄｏｓ…     

稀溶液的依数性与浓度关系的推导方法

讨论稀溶液的依数性与浓度关系的两种推导方法,并指出了说明此种关系的μA-T图与p-r图需要注意的地方。     

高分子稀溶液粘度的浓度依赖性

综述了高分子稀溶液粘度浓度依赖性的物理起源问题。对原有理论的不足作了分析,并论述了新近出现的团簇理论对理解此问题所作出的贡献。     

支化高分子稀溶液粘度的浓度依赖性

自缔合平衡常数;支化高分子稀溶液粘度的浓度依赖性     

维生素C稀溶液光化分解导致的振荡行为

光化学振荡是近十多年才发现和研究的一种新的时空振荡行为目前的文献屈指可数,机制的解释各说不一。维生素C的化学振荡1982年以来仅有个别的报导。我们发现在一定浓度,温度条件下,局部光照维生素C稀溶液,若不搅拌,经过一段前置期可以获得规整性和重现性相当好的衰减式周期性振荡波。本文还研究了它的特征,形成条件及其可能的偶合机制,对维生素C稀溶液光化学反应动力学和机理也进行了探讨。     

极稀溶液体系中自组装合成纳米介孔氧化硅及其铝修饰材料

在极稀溶液中, 通过改变反应溶剂去离子水的量或原料中铝源的量, 可控合成了不同粒径(20~70 nm)、形貌和孔道结构的纳米介孔氧化硅颗粒和纳米介孔铝掺杂氧化硅材料. 这种材料具有高比表面积(BET比表面积1000 m²/g)和较大的孔容(1.1~1.8 cm³/g). 反应物浓度降低或反应物中添加铝源后, 介孔材料的有序性下降, 粒径减小, 孔容增大, 并产生大量的间隙孔. 通过小角X射线衍射(SAXRD)、透射电镜和氮气吸附-脱附实验表征了样品.     

EFFECT OF ADSORPTION ON THE VISCOSITY OF DILUTE POLYMER SOLUTION*

Careful measurements of the dilute solution viscosities of polyethylene glycol and polyvinylalcohol in water were carried out. The reduced viscosities of both polymer solutions plot upward curves atextremely dilute concentration levels similar to the phenomena observed for many polymer solutions in theearly 1950's. Upon observation of the changes of the flow times of pure water in and the wall surfacewettability of the viscometer after measuring solution viscosity, a view was formed that the observed viscosityabnormality at extremely dilute concentration regions is solely due to the effect of adsorption of polymerchains onto the wall surface of viscometer. A theory of adsorption effect based on the Langmuir isothermswas proposed and a mathematical analysis for data treatment was performed. The theory could adequatelydescribe the existing viscosity data. It seems necessary to correct the viscosity result of dilute polymersolutions measured by glass capillary viscometer by taking into account the effect of adsorption in all cases.     

高分子混合物溶液在极稀浓度区的粘度异常行为

上世纪50年代初人们就发现,高分子溶液的粘度在极稀浓度区往往表现出异常行为,即当浓度低于某一特定值后,比浓增比粘度-浓度图偏离预计的线性关系,出现上弯或下弯的曲线.     

VISCOSITY BEHAVIOR OF PS／TOLUENE SOLUTION IN DILUTE AND EXTREMELY DILUTE CONCENTRATION REGION

The influences of both the volume of PS/toluene solution in the Ubbelohde viscometer and the precision of the time measuring on the viscosity behavior in dilute and extremely dilute concentration region are investigated. It was found that the influence of the former can neglect, but that of the latter is so prominent that the data fluctuate bitterly and linearity of the curve of the reduced viscosity vs. concentration (ηsp/c-c) becomes too bad to obey the Huggins equation down to the extremely dilute region, despite the error of the flow times Δt≤0.2s, which is permitted by the conventional method of viscosity measurement. Through strict mathematical analyses, it was found that the error (E) of the reduced viscosity is in proportion and inverse propor tion to Δt and concentration c, respectively. So the less the concentration, the more the error is. Consequently, a lowest concentration limit cL corresponding to given experimental error may exist and it will be meaningless for further operation below CL because of the great fluctuation of the data. Therefore, it needs to seriously reconsider the application of the conventional method of Ubbelohde viscosity measurement in the extremely dilute polymer solution under traditional conditions because of the great influence of the experimental error.     

VISCOSITY BEHAVIOR OF PS/TOLUENE SOLUTION IN DILUTE AND EXTREMELY DILUTE CONCENTRATION REGION

1.INTRODUCTIONAsearlyas1950sitwasfoundthatsolutionviscosityofasinglepolymerinextremelydiluteconcentrationregionusuallyrevealssomeabnormalities,i.e.,thereducedviscosityconcentration(hsp/c~c)curvesdeviatefromlinearrelationshippredictedasHugginsequationandshoweitheranupwardoradownwardturnasconcentrationisverylow[1].Evenifforthe[()-0.2()]identicalPMMA/toluenesolution,therearetwocontraryresults:onereportedthecurvebendsupward[2],whiletheotherfounditdownward[3].Inordertointerpretthisabnormalphe…     

Grafting of maleic anhydride on polyethylene. I. Mechanism of grafting in a heterogeneous medium in the presence of radical initiators

Polyethylene has been grafted with maleic anhydride, as proved by the infrared spectra and the properties of the grafted films. The influence of oxygen and a comparison of the effectiveness of benzoyl peroxide and AIBN showed that polyethylene macroradicals are formed through the decomposition of hydroperoxide and peroxide groups. Side chains of poly(maleic anhydride) are formed by a combination of polyethylene macroradicals with those of poly(maleic anhydride). This mechanism of reaction was confirmed by the influence of the amount of film, the initiator and monomer concentrations, and temperature on the percentage of grafting.     

部分水解聚丙烯酰胺水溶液的零剪切黏度和临界浓度

通过蠕变和振荡实验分别测定了部分水解聚丙烯酰胺(PHPA)水溶液的零剪切黏度(η₀)和线性黏弹区储能模量(G'), 并依据其浓度依赖性得到叠加浓度(C^*)和交叠浓度(C^*), 考察了温度、pH值和电解质(NaCl和CaCl₂)浓度的影响. 结果表明, 随着温度的升高和电解质浓度的增大, PHPA水溶液的η₀及G'减小, C^*和C^*增大; 电解质阳离子价态越高, 溶液黏度和临界浓度的变化越显著; 而随着pH值的增大, η₀及G'先增大后减小, C^*和C^*先减小后增大.     

Kinetic studies of grafting of maleic anhydride to hydrocarbon substrates

The kinetics of grafting of maleic anhydride to various hydrocarbon substrates has been investigated. Grafting to eicosane and squalane was effected in the pure hydrocarbons and in 1,2-dichlorobenzene solution, while polyethylene was grafted only in solution. The initiator was 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne which has a half life of about 1 h at a typical reaction temperature of 150°C. At high concentrations of initiator (Ca. 0.02M), the rate of disappearance of maleic anhydride is linear with time. In the pure hydrocarbons the order with respect to initiator is close to 0.5. In squalane, the overall activation energy is 112 kJ mol^?1; the average number of maleic anhydride molecules grafted per molecule of peroxide decomposed varies from 8 at high rates of initiation to 57 at low rates of initiation. The results are interpreted in terms of a chain mechanism, including a slow propagation step in which a succinic anhydride radical abstracts hydrogen from the same or a different chain. The same general mechanism is proposed for grafting of maleic anhydride to polyethylene and the hydrocarbons in 1,2-dichlorobenzene solution.     

马来酸酐改性聚乙烯的制备及其与尼龙的共混物

本文叙述了在聚乙烯-马来酸酐熔融接枝反应过程中,伴随着聚乙烯分子之间的交联反应,少量的己内酰胺添加剂可以有效地阻止交联反应的发生,改善体系的流变性能,而不明显地降低它的接枝率。这种马来酸酐化聚乙烯作为界面相容剂可使尼龙6-聚乙烯共混物的简支梁抗冲击强度比没有界面相容剂的共混物增加近4倍。     

Effect of comonomer sorption on radiation-induced copolymer grafting onto polyethylene and EVA films in the vapor phase

Radiation-induced copolymer grafting of acenaphthylene and maleic anhydride onto polyethylene or EVA film in the vapor phase was carried out and the effect of comonomer sorption on the grafting was studied. When polyethylene film was used as a backbone polymer, the sorption of the binary monomers during the grafting increased linearly as the grafting reaction proceeded. The marked increase was probably caused by the formation of a grafted layer. Particularly, the sorption of maleic anhydride was brought about by the existence of a grafted layer. In grafting onto EVA film, the content of maleic anhddride in the grafted copolymer increased with the increasing content of vinyl acetate in EVA. Continuous measurements of sorption of the comonomers onto EVA and grafted EVA films were carried out by use of an electrobalance. The distinctive feature of the sorption was that the equilibrium sorption of acenaphthylene or maleic anhydride onto the grafted EVA film increased and the diffusion constants for both comonomers decreased markedly with increasing percentage of graft. The copolymer grafting was explained from these results by assuming that the monomer molecules are supplied to the propagating chain ends mostly through a sorbed state on the polymer film.     

Rheology of polymers that are initially in the disentangled state

An attempt was made to measure the effects of molecular entanglements on the rheological properties of polymer melts. Two classes of polymers were studied; glassy atactic polystyrene polymers covering a 60-fold range in molecular weight, and semicrystalline high-density polyethylene from two sources covering about a twofold range in molecular weight. The entanglements initially present were removed or greatly reduced in number by freeze drying the polystyrene polymers from dilute solutions below and above C*, the critical overlap concentration, and by slowly crystallizing the polyethylene from very dilute solutions. Since only minor rheological changes were observed with polystyrene, it would appear that the initially isolated coils interpenetrate more rapidly than is indicated by the results of Liu and Morawetz, or that the rheological behavior is rather insensitive to whether the flow obstacles are intermolecular or intramolecular. The enhancement of the viscosity and elasticity observed with polyethylene polymers indicate the importance of the crystallization step on the local melt topology of the polymer chains.