GPC普适校准法确定聚醚化合物的Mark-Houwink方程的k-α值

<正> 一、前言粘度法是一种利用粘度测定高分子分子量的方法。该法所使用的方程是Mark、Houwink 在其他人研究的基础上,提出的著名高分子特性粘数定律方程:[η]=KM~α(1)K、α为常数,两者与高分子物种类、结构、分子量范围、溶剂性质、温度有关。M、[η]为分子量和特性粘数。K、α值的确定一般需使用单分散已知分子量的高分子物。本方法是以GPC 普适校准法与粘度测     

单濃度法測定聚氯乙烯特性粘数

粘度法测定高聚物的特性粘数,一般是由η_(sp)/c或hlη_r/c对c作图,外推至→0求得。此法手续烦琐而费时。梅朗(S.H.Maron)提出了以下公式[η]=(η_(sp)-γlnη_r)/((1+r)c) (1)以计算高聚物的特性粘数。在给定高聚物——溶剂体系中,γ是与高聚物分子量无关的常数,也就是,每种高聚物—溶剂体系有一个确定的γ值。如果在给定体系中,测得高聚物一个样品的γ值,此值即可用于同一高聚物的不同分子量样品的特性粘数的计算中。梅朗测得聚苯乙烯—甲苯体系在30℃和醋酸纤维素—丙酮体系在25℃时的γ值分别为2.73和5.33,以此二值分别代入式(1),计算得到的特性粘数值的误差在要求的范围之内。我们采用此法测定聚氯乙烯的特性粘数,确定聚氯乙烯—环已酮体系在25℃时其γ值为2.21。测得不同浓度的聚氯乙烯环已酮溶液的η_(sp)和lnη_r,以此γ值(2.21)代入式(1)计算得到的特性粘数值与其外推值列于下表。     

纤维素在氯化锂—N,N二甲基乙酰胺溶剂系中溶胀与溶解的影响因素(摘)

在纤维素、氯化锂(LiCl)、N.N二甲基乙酰胺(DMAc)体系中,LiCl分子与纤维素分子中葡葡糖残基的摩尔比大于3左右,纤维素才可能形成真溶液。LiCl/DMAc溶剂体系中含少量水份,能加快纤维素在其中的溶解;溶剂体系中含过多的水分,便失去溶解纤维素的能力。适当升高纤     

混合溶液中SBS—g—PMMA接枝共聚物极限粘数的研究

本文研究了ＳＢＳ－ｇ－ＰＭＭＡ接枝共聚物在环己烷、甲苯、丙酮两两混合体系中极限粘数（η）随混合溶剂组成变化的关系，发现：混合溶剂中共聚物极限粘数是溶剂分别对共聚物各组份链段作用的共同贡献结果。因此，聚合物在混合溶液中有可能存在分子链最为舒展的点，即为（η）极大值点。     

在线红外跟踪碱活化纤维素在LiCl/DMAc中的溶解

LiCl/DMAc可作为纤维素的溶剂。笔者利用在线红外技术实时跟踪碱活化纤维素在LiCl/DMAc中的溶解过程。结果表明,LiCl/DMAc可以在一定程度上破坏纤维素中氢键,实现对纤维素的溶解,无中间衍生物产生,最终溶液中纤维素主要以多聚体形式存在。同时,检测出LiCl/DMAc对纤维素的高温预溶解与室温溶解过程,且此过程可逆。     

生物合成聚γ-谷氨酸(钠盐型)稀溶液的粘度特性

为了确定特定条件下生物合成聚γ 谷氨酸(γ PGA)稀溶液的Mark Houwink方程参数,从而在关系适用范围内能够通过比较简单的特征粘数测量对γ PGA的相对分子质量进行快捷而可靠的估算,用毛细管粘度计法对钠盐型γ PGA稀溶液的粘度特性进行了系统考察。结果发现钠盐型γ PGA是一种典型的聚电解质,在一定浓度范围内显示了比浓粘度独特的浓度依赖性:不服从Huggins方程。中等离子强度的外加小分子强电解质会减小γ PGA稀溶液的特性粘数[η],并使之呈现出正常的粘度行为,且[η]与溶液中离子强度的-1/2次幂成较好的线性关系。[η]具有一定的时间依赖性。     

乙烯-醋酸乙烯酯弹性体的制备和研究

制备乙烯-醋酸乙烯酯(EVA)共聚物弹性体,研究溶剂引发剂选择及不同反应乙烯压力对EVA弹性体分子结构、固含量、玻璃化转变温度(Tg)、分子量和特性粘数[η]的影响。研究表明,链转移常数低的小分子醇类宜作为反应溶剂;适量引发剂可提高EVA弹性体醋酸乙烯酯(VAc)含量(w)和分子量;反应压力提高,EVA分子结构亚甲基质子峰向高磁场移动,产物固含量增加,玻璃化转变温度(Tg)和特性粘数[η]降低。     

细菌纤维素在LiCl/DMAc溶剂体系中的溶解性能研究

纤维素经过活化后可以溶解在LiCl/DMAc溶剂体系中,研究了乙二胺活化对细菌纤维素溶解性能的影响,得到最佳活化条件;研究了LiCl的浓度、溶解温度和搅拌时间对溶解性能的影响,得到最佳溶解条件;研究了细菌纤维素在LiCl/DMAc极性溶剂体系中的溶解机理。     

高聚物特性粘数的研究 Ⅰ特性粘数的二次外推

高聚物分子量的测定,最方便、应用最广泛的方法是粘度法。即高聚物溶解在一定的溶剂中,在一定的温度下测得其特性粘数,然后按已经订出的分子量—特性粘数关系式。 [η]=KM~α求得聚合物的分子量。但是,对于特性粘数的概念,以及如何正确求得聚合物的特性     

三元共聚丙烯腈纤维的一点法粘度式

本工作以山东淄博合成纤维厂生产的三元共聚丙烯腈纤维为样品将其分成十一个级分,分别用四个不同方法制定的一点法粘度式计算该纤维和十一个级分的[η](特性粘数),并与经典方法Huggins方程求出的[η]比较,得到适合于工厂推广应用的一点法粘度式。     

Comparison of various solvents for determination of intrinsic viscosity and viscometric constants for cellulose

Different solvents used to determine the intrinsic viscosity and the viscometic constants, a and K, published in the literature for cellulose, were compared. The various parameters affecting the viscometric constants were also evaluated. The main conclusions obtained from the experimental data available in the literature are that (1) the intrinsic viscosities in various solvents are ordered as follows: [η]_LiCl/DMAc > [η]_NH3/NH4SCN ≥ [η]_FeTNa > [η]_CED > [η]_Cadoxen > [η]_Cuoxam; (2) the reported intrinsic viscosities and molecular weights for cellulose are lower than the true value due to degradation of cellulose in the solvents; (3) the rate of degradation was the smallest in LiCl/DMAc and NH₃/NH₄SCN, moderate in cadoexn and FeTNa, and the highest in CED and cuoxam; (4) the plot of log K versus exponent a was linear and inversely related; (5) the curve was used for estimation of the constant K for cellulose in a solvent (NH3/NH4SCN) with a known exponent a; and (6) among various reported solvents, LiCl/DMAc and NH₃/NH₄SCN are advantageous over other solvents because of a complete dissolution of the polymer with a negligible reduction in its intrinsic viscosity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2189–2193, 2002     

Investigation of the cellulose/LiCl/dimethylacetamide and cellulose/LiCl/N-methyl-2-pyrrolidinone solutions by 13C NMR spectroscopy

The cellulose/lithium chloride/dimethylacetamide (DMAc) and cellulose/lithium chloride/N-methyl-2-pyrroilidinone (NMP) solutions were investigated by ¹³C NMR spectroscopy. Well-resolved spectra were obtained for both solutions and indicated that cellulose was present in these systems in the form of underivatized cellulose. The change in ¹³C chemical shifts of DMAc and NMP in the presence of LiCl and LiBr was compared with that of several salt/aprotic solvents, and the results point to the existence of a cellulose–LiCl–DMAc (or NMP) complex in which the lithium cation is strongly bound to the amide carbonyl oxygen and the chloride anion involved in the dissociation of the cellulose hydrogen bonds. Spin–lattice relaxation times (T₁ of the ¹³C carbons of the solvent molecules, DMAc and NMP, show a large decrease in T¹ for all solvent carbons upon addition of LiCl. Further decrease in T₁ is observed when cellulose is introduced to the LiCl/NMP but not to the LiCl/DMAc systems. These observations are attributed to slower molecular motions of DMAc and NMP in the presence of LiCl, and, in the case of NMP, in the presence of cellulose.     

Rheological Behavior of Poly(m-phenyleneisophthalamide) in Ionic Liquid

Summary The rheological behavior of poly(m-phenyleneisophthalamide) (PMIA) in 1-n-butyl-3-methylimidazolium chloride ([Bmim]Cl, ionic liquid) has been investigated. The polymer in the concentration range investigated exhibits very different behavior between [Bmim]Cl and DMAc/LiCl solvent. Unlike in DMAc/LiCl solvent, PMIA/[Bmim]Cl solution exhibits maxima in apparent viscosity-concentration plots in the range studied. The complex viscosity-frequency behavior of the PMIA/[Bmim]Cl solutions is similar to that steady-state rheological behavior. The different rheological behavior shows the interaction between macromolecule and IL which leading the supermolecular aggregates in PMIA/[Bmim]Cl solution.     

Derivatization of cellulose in lithium chloride and N-N-dimethylacetamide solutions

The derivatization of cellulose in mixtures of lithium chloride and N,N-dimethylacetamide (LiCl/DMAc) is described. A wide range of cellulose derivatives, including cellulose esters, carbamates, sulphonates and ethers, have been synthesized in homogeneous solution using the LiCl/DMAc solvent. In most cases, a high degree of substitution was achieved, and the degree of substitution could be controlled accurately. Compared to current heterogeneous synthesis of cellulose derivatives, reactions conducted in homogeneous solutions of LiCl/DMAc have many advantages: (1) reactions may be conducted at moderate temperatures; (2) less reagent is required; (3) less degradation of the cellulose occurs; and (4) substitution is uniformly controllable.     

聚丙烯腈/棉纤维素薄膜的制备与性能研究

以N,N二甲基乙酰胺/无水氯化锂（DMAc/LiCl）为溶剂配置聚丙烯腈（PAN）和棉纤维素溶液,采用旋涂法制备不同比例的PAN/棉纤维素薄膜。通过旋转黏度计对PAN/棉纤维素共混溶液的表观黏度进行研究,采用X射线衍射仪、傅里叶红外光谱仪、电子万能试验机以及吸水性能测试对PAN/棉纤维素薄膜的结构和性能进行了研究。结果表明,共混溶液的表观黏度随着纤维素含量的增加逐渐增大;DMAc/LiCl溶剂对PAN和棉纤维素的溶解为直接溶解,没有发生衍生化反应;PAN和棉纤维素均保持各自结晶结构不变;当棉纤维素含量为2.0 %（质量分数,下同）时,复合薄膜的拉伸强度和断裂伸长率达到最大值;棉纤维素含量越高,复合薄膜的吸水性越好。     

Substitution of corn starch with polycaprolactone via chlorination and water resistance of the substituted starch

Corn starch was chlorinated using methanesulfonyl chloride in dimethylformamide (DMF) and then substituted with polycaprolactone (PCL) in various solvents [dimethylsulfoxide (DMSO), water and dimethylacetamide (DMAc)] containing a catalyst [sodium hydroxide (NaOH) or lithium chloride (LiCl)] to improve water resistance. The reaction yield based on the product weight was highest (85%) when DMAc and LiCl were used. Fourier transform infrared (FTIR) spectra showed that starch was monosubstituted with PCL in the aqueous NaOH solution, whereas it was to crosslink by PCL in the case using DMAc and LlCl. The intrinsic viscosity of the products in DMSO supports these trends. By introducing the hydrophobic PCL onto starch, solvent resistance of the substituted starches to water and other aqueous media increased. The crosslinked starch displayed higher water resistance than the monosubstituted starch. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2197–2202, 2001     

Comparative study of homogeneous solvents for the esterification crosslinking of cellulose with 1,2,3,4‐butanetetracarboxylic dianhydride and water absorbency of the reaction products

Superabsorbent hydrogels were prepared via esterification crosslinking of cellulose with 1,2,3,4‐butanetetracarboxylic dianhydride (BTCA) in three solvent systems: lithium chloride (LiCl)/N‐methyl‐2‐pyrrolidinone (NMP), LiCl/N,N‐dimethylacetamide (DMAc), and tetrabutylammonium fluoride/dimethyl sulfoxide (TBAF/DMSO). The absorbency of the hydrogels was strongly dependent on the BTCA feed to cellulose ratio as well as the nature of the solvent system used. The rate of cellulose esterification was enhanced in TBAF/DMSO relative to the other systems, and the highest water absorbency of the hydrogels (987 g g^?1 polymer) was also achieved using this system. The hydrogels obtained in the TBAF/DMSO system had a similar degree of both crosslinking and grafting, indicating that both reactions were promoted to the same extent in this solvent, whereas crosslinking was preferentially enhanced over grafting in the LiCl/NMP and LiCl/DMAc systems. The difference in the composition of the hydrogels was attributed to the difference in the electronegativity of the fluoride and chloride anions in these solvents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

棉纤维在LiCl/DMAc极性溶液中的溶解性能研究

采用不同方法将棉纤维活化并溶解在LiCl/DMAc极性溶液中,研究了活化方法、溶解温度、时间及LiCl浓度对棉纤维素溶解性的影响。结果表明:DMAc热活化法为较好的活化方法;提高溶解温度,延长溶解时间及提高LiCl浓度均有利于棉纤维溶解;棉纤维在LiCl质量分数为12%的LiCl/DMAc溶液中,150℃下搅拌4h,溶解度可达3%。碱活化法使棉纤维素聚合度大幅度降低,可提高棉纤维溶解度至8%。通过扫描电镜和X射线衍射方法研究了棉纤维在前处理和溶解过程中的形态和结构变化,初步揭示了纤维素高温处理后在低温下发生溶解的机理。     

Cellulose in lithium chloride/N,N-dimethylacetamide, optimisation of a dissolution method using paper substrates and stability of the solutions

Activation and dissolution in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) of cellulose from paper substrates are studied. The importance of the multiple parameters involved such as salt concentration, sample source and preparation is shown in a literature review. The experiments are carried out in order to perfect the method of activation and dissolution of paper containing different kinds of additives, typically found in historic papers. The suitability and efficiency obtained in the different trials are evaluated. The final procedure involves the activation by solvent exchange, with a water/methanol/DMAc sequence, followed by dissolution in 8% LiCl/DMAc at 4 °C. A study of the stability of the cellulose solutions in the experimental conditions showed that no degradation nor aggregation occurred during the solvation process and even after several months and confirmed the non-aggressiveness of LiCl/DMAc.