用单-检测器的尺寸排除色谱同时测量嵌段共聚物的组成和分子量

 本文建议了一种使用具有单一检测器的常规尺寸排除色谱仪同时测量嵌段共聚物纽成和分子量的方法。方法要求测定原试样的特性粘数和尺寸排除色谱图,而检测器只对嵌段共聚物两个组份之中的一个有响应。首先用均聚物标样定出尺寸排除色谱柱的响应常数和分子量分离校准曲线。原试样的实验谱图用解叠方法得到共聚物和均聚物的两个组成峰。借助响应常数和普适校准原则计算得到共聚物的组成和分子量。本法应用于苯乙烯-硅氧烷嵌段共聚物的分析得到满意结果。     

共聚产物的体积排除色谱定量组成分析

]本文给出了一种测定共聚产物组成的一般性体积排除色谱定量方法。共聚产物中存在的均聚物和未反应单体的含量以及共聚物本身的单体组成,可以结合用溶解度分离均聚物以处理试样,从体积排除色谱的试样注入量和实验谱图的面积计算得到。这一方法在聚二甲基硅氧烷-g-聚苯乙烯接枝共聚产物的组成分析上获得成功应用。     

研究多嵌段共聚物组成分布的一种新方法

提出一种研究-(A-B)_n-型嵌段共聚物组成分布的新方法。本方法不需任何单分散样品或模型化合物作为标准物质,不需另外进行仪器常数标定,只要求测试过程中仪器常数保持不变。要求样品必须是系列样品,每个样品的平均组成已知或可用其它方法得到,样品个数n≥2,且样品越多越好;对检测器的要求是,两种检测器对不同的嵌段其响应不成比例,响应比差别越大越好。对分离手段的分离机理无要求,只要求样品的分散程度足够大即可。本文还提供了用薄层色谱法研究聚己内酯型聚氨酯多嵌段共聚物的组成分布的实例。     

聚苯乙烯-b-聚丙烯酸/聚苯乙烯在水中的自组装及胶束尺寸的研究

利用动态光散射、透射电镜研究了嵌段共聚物聚苯乙烯 b 聚丙烯酸(PS b PAA)与均聚物聚苯乙烯(PS)在选择性溶剂水中的自组装行为.由于均聚物PS与PS嵌段具有相同的结构单元,均聚物PS参与胶束的形成,和嵌段共聚物的PS链段一同组成胶束的核;在适当的均聚物分子量和含量条件下,PS b PAA PS可以自组装形成单分散的纳米胶束;通过改变体系中均聚物PS的分子量和含量可在较大范围内调变胶束的尺寸.     

聚乙烯-聚二甲基硅氧烷两嵌段共聚物的合成及表征

用阴离子聚合方法合成了具有确定组成、确定分子量及窄分子量分布的聚丁二烯-聚二甲基硅氧烷两嵌段共聚物(PB-PDMS)。用对-甲苯磺酰肼氢化聚丁二烯段,得到聚乙烯-聚二甲基硅氧烷两嵌段共聚物(PE-PDMS)。¹H-NMR谱及IR光谱均表明加氢是完全的。示差扫描量热法(DSC)对PE-PDMS研究结果表明其结晶行为与共聚物的组成有关。     

沉淀分离法及高效凝胶色谱分析聚合物的共混物-聚苯乙烯、氯醇橡胶及苯乙烯与环氧丙烷嵌段共聚物

 ]脆性的聚苯乙烯塑料与韧性的氯醇橡胶共混，聚苯乙烯-聚环氧丙烷的多嵌段共聚物作为共混物的增容剂，这种共混高分子材料具有热塑性弹性体的基本特点。本文用沉淀分离法定量得到共混物的组分，并用高效凝胶色谱（GPC）分析各组分的含量；从GPC曲线计算嵌段共聚物的k和值；表征了聚苯乙烯-聚环氧丙烷的嵌段共聚物分子量、分子量分布及组成。     

PS-PMMA嵌段共聚物/PMMA在选择性溶剂中的自组装行为

用动态光散射和透射电镜研究了嵌段共聚物聚苯乙烯-聚甲基丙烯酸甲酯(PS-b-PMMA)和其对应的均聚物聚甲基丙烯酸甲酯(PMMA)在选择性溶剂四氢呋喃/环己烷(THF/CYH)中的自组装行为.选择性溶剂对PS嵌段是良溶剂,对PMMA嵌段和均聚物PMMA是非良溶剂,实验结果表明,在适当的分子量及组成条件下,PS-PMMA/PMMA在选择性溶剂中形成了单分散的纳米胶束,均聚物PMMA与PMMA嵌段一同形成了胶束的核,通过控制均聚物PMMA的量可以在较大的范围内调整胶束的尺寸.     

用于大分子定向自组装的新型嵌段共聚物的合成与表征

设计了具有高Flory-Huggins相互作用参数的嵌段共聚物聚(对叔丁基苯乙烯)-b-聚(甲基丙烯酸羟乙酯)(PtBS-b-PHEMA),并分别采用阴离子聚合和原子转移自由基聚合(ATRP)方式制备了不同嵌段比例、不同分子量的窄分子量分布的该嵌段共聚物。利用核磁共振分析了嵌段共聚物的组分,利用小角X射线散射(SAXS)分析了嵌段共聚物相分离后的尺寸及结构,对比研究了两种聚合方式对嵌段共聚物性能的影响。结果表明,采用阴离子聚合方式得到的嵌段共聚物分子量分布更窄,相同分子量下发生微相分离的尺寸更小,其在150℃真空烘箱中加热18h后可以形成尺寸为9.96nm的柱状相及8.42nm的层状相。     

示差折光和光散射双检测体积排除色谱的绝对定量化

讨论了示差折光和光散射联用双检测体积排除色谱的绝对定量化的原理,强调指出了试样注入量在数据处理中的重要作用.测量注入试样的这两种检测器的检测常数,可以同时得到试样的折光指数增量和重均分子量的绝对值.这一方法除了适用于各种均聚物外,还可以应用于高分子混合物的分析.此时,如将混合物看作为单一溶质,从所得折光指数增量和重均分子量,可对它们的组成作出定量分析,还可以判断共混物两个组分之间有无分子缔合等现象的产生.这一方法应用于聚甲基丙烯酸甲酯/聚苯乙烯(PMMA/PS)混合物的溶液,指明在四氢呋喃中两者产生缔合而形成了复合物.     

用薄层色谱法表征苯乙烯-二甲基硅氧烷嵌段共聚物的结构

常规的红外或核磁法不能区别嵌段共聚物与均聚物的共混物。不同类型嵌段共聚物间的区别更加困难.我们用薄层色谱法(TLC)来表征嵌段共聚物的结构.根据TLC吸附机理,利用展开剂的极性大小可将均聚物及嵌段共聚物迅速地区别、鉴定与分离.实验时应注意控制条件以抑制薄层吸附剂的分子筛效应,避免分子量及其分布的干扰.     

定量SEC法同时测定短链共聚物的组成和分子量

由于端基对整体高分子链光学性质的贡献，短链高分子的折光指数增量有明显的分子量依赖性．从整体高分子链折光指数增量依从各结构组成单元折光指数增量的重量分数加和律，指示同一高分子链改变端基后，如分别测定它们的折光指数增量。由其差值可以同时获得链干的分子量和折光指数增量，对共聚物言，从链干的折光指数增量又可进而估定共聚物的组成．这一原则特别适用于具有显著端基效应的短链高分子．本工作用定量尺寸排除色谱方法测量具有不同端基的环氧乙烷－环氧丙烷共聚物苯溶液的折光指数增量，以考验此原则，获得了满意结果．     

二元复杂共混体系组成的SEC-LS分析

提供了一种利用体积排阻色谱-光散射(SEC-LS)联用技术来解决二元复杂共混体系组成的定量分析问题.基于体积排除色谱的绝对定量化原则,首先从理论上分析了共混物的光散射响应因子与组成呈线性关系.通过分析六组复杂共混体系的光散射响应因子与组成的关系,验证了该线性关系确实存在.进而利用该线性关系计算了共混体系的组成.在某些共混体系中,通过光散射响应因子得出的组成比利用示差法得出的组成更加接近原料组成.通过分析这两种方法产生误差的来源,阐述了产生该现象的原因.     

二元复杂混合物组成的定量SEC分析

提供了一种体积排除色谱(SEC)的绝对定量分析方法以解决复杂的二元混合物组成的定量分析问题.首先对传统的SEC数据处理方法作了改进,将示差检测响应信号H(V)除以样品进样质量,得到单位质量的示差折光检测响应分布Hw(V)和累积分布Iw(V),这两个分布与试样的检测响应常数有关.然后将Hw(V)除以总面积,再得到常规的归一化分布F(V).混合物检测响应常数的不同,提供了一种从单独组分的Hw(V)或Iw(V)分布,运用加和计算共混物的Hw(V)或Iw(V)分布,得出二元混合物的组成.运算过程利用最小差方和的枚举计算方法,在一个自行编写的Mathcad程序工作单上进行.应用该方法对一种工业沥青和两种稀释剂配成的二元混合物作了范例分析,得到满意结果.     

Two-dimensional liquid chromatography of PDMS-PS block copolymers

In this study, liquid chromatography at critical conditions of polystyrene (PS) and polydimethylsiloxane (PDMS) is used as the first dimension for the two-dimensional analysis of polydimethylsiloxane-block-polystyrene copolymers. Comprehensive two-dimensional liquid chromatography with size exclusion chromatography as the second dimension reveals information about the molar mass distributions of all separated fractions from the first dimension. Furthermore, fractions eluting at the critical conditions were collected and subjected to analysis in the second dimension at the critical adsorption point of the other block. These fractions were analyzed by Fourier transform infrared spectroscopy to determine their chemical compositions. The combination of the above approaches and the calibration of the evaporative light scattering detector for the first-dimension analysis yield deep insights into the molecular heterogeneity of the block copolymer samples. The composition of the samples and the chemical composition of the real block copolymer are also calculated by combining the results obtained at both critical conditions.     

Densimeter detector in gel permeation chromatography of copolymers

A commercially available densimeter with a vibrating stainless steel tube was used as a detector in the GPC analysis of styrene/methyl methacrylate copolymers under normal GPC operational conditions. The densimeter was thermostated to ±0.001°C and sample injection concentrations were 4.0 mg/mL. The copolymer samples were polydisperse in molecular weight but uniform in composition. A refractive index detector and the densimeter detector produced comparable estimates of the parameters of the molecular weight distributions. The densimeter is less sensitive to the effects of variations in copolymer composition than differential refractive index or ultraviolet detectors. The only serious drawback to the densimeter is a relative lack of sensitivity. Variations in composition of styrene/methyl methacrylate copolymers over a fairly wide range have no signficant effect on the relation between gel permeation chromatographic elution volume and copolymer molecular weight. In general, however, conventional means of summarizing these data are not applicable to compositionally heterogeneous mixtures. Instrumental and data-handling solutions to this problem are discussed.     

丙烯酰胺-苯乙烯双亲嵌段共聚物水溶液的表面活性及增溶性

在微乳液介质中制备了系列的丙烯酰胺 (AM)与苯乙烯 (St)的双亲嵌段共聚物 (PAM b PSt) ,用紫外分光光度法测定了共聚物的组成 ,用乌氏粘度计测定了共聚物的特性粘数 [η],并用其相对表征共聚物的分子量大小 .重点研究了双亲嵌段共聚物 (PAM b PSt)疏水链段在水溶液中的缔合行为、共聚物的表面活性及其对有机物的增溶性能 ,考察了共聚物分子组成 (疏水链段含量 )与分子量对其表面活性与增溶性能的影响规律 .研究结果表明 ,由于疏水链段的憎水性 ,PAM b PSt的分子链在水溶液表面会形成表面吸附 ,从而降低水溶液的表面张力 ;而在水溶液中 ,在疏水相互作用下 ,PAM b PSt分子链中的苯乙烯疏水链段会形成分子间或分子内的胶束 ,烃类有机物可增溶其中 ;疏水链段含量越大 ,分子量越小 ,PAM b PSt的表面活性与增溶性能越强     

Composition analysis of poly(ethylene glycol)-poly(L-lactide) diblock copolymer studied by two-dimensional column chromatography

We used two-dimensional column chromatography to analyze the composition of a sample of presumably a diblock copolymer of poly(ethylene glycol) (PEG) and poly(L-lactide) synthesized from monomethoxy-terminated PEG. The first dimension of the separation is phase fluctuation chromatography to prepare fractions that contain various components of the copolymer in different ratios. The second dimension is size-exclusion chromatography, NMR, and HPLC at the critical condition of PEG. The PEG initiator has small amounts of diol-terminated dimeric components. We found that the copolymer sample contains a triblock copolymer and low-molecular-mass components in addition to the main part of the diblock copolymer. The SEC chromatograms show that the main part consists of two components with distinct peak lengths for the PLLA block. The low-molecular-mass components have a broad distribution in chemical composition. Phase fluctuation chromatography enriched the triblock copolymer and the diblock copolymer with the longer PLLA block in early fractions when the column was packed with carboxymethyl-modified porous silica. When the porous medium was PLLA-grafted silica, size exclusion dominated, but the low-molecular-mass components were separated according to their chemical composition.     

Synthesis and characterization of amphiphilic diblock copolymers of methyl tri(ethylene glycol) vinyl ether and isobutyl vinyl ether

Water-soluble diblock copolymers of methyl tri(ethylene glycol) vinyl ether (hydrophilic block) and isobutyl vinyl ether (hydrophobic block) of different molecular weights and composition were synthesized by living cationic polymerization. The molecular weight and comonomer composition of these copolymers were determined by GPC and ¹H NMR spectroscopy, respectively. Aqueous solutions of the copolymers were characterized in terms of their micellar behavior using dynamic light scattering, aqueous GPC, and dye solubilization. All the copolymers formed aggregates with the exception of a diblock copolymer with only two hydrophobic monomer units. The micellar hydrodynamic size scaled with the 0.61 power of the number of hydrophobic units, in good agreement with a theoretical exponent of 0.73. An increase in the length of the hydrophobic block at constant hydrophilic block length or an increase in the overall polymer size at constant block length ratio both resulted in lower critical micelle concentrations (cmcs). The cloud points of 1% w/w aqueous solutions of the polymers were determined by turbidimetry. An increase in the length of the hydrophobic block at constant hydrophilic block length caused a decrease in the cloud points of the copolymers. However, an increase in the overall polymer size at constant block length ratio led to an increase in the cloud point. © 1996 John Wiley & Sons, Inc.